Composite thermal runaway detector for battery pack

Abstract

According to the composite thermal runaway detector for the battery pack provided by the invention, the photoelectric smoke sensor is arranged to monitor smoke, and the gas sensor is used to detect gas generated in combustion, so that the functional requirements of the composite thermal runaway detector are met; meanwhile, the use scene of the battery pack of the lithium battery is a sealed environment, so that a complicated labyrinth structure does not need to be designed in the scheme, the overall size is effectively reduced, and the cost is saved; according to the photoelectric smoke sensor, the light-emitting tubes of discrete devices are combined with the patch-type receiving tubes to realize brand new optical design, so that the cost can be saved, the overall size can be reduced by utilizing the advantages of the patch-type receiving tubes, and meanwhile, the patch-type receiving tubes are also beneficial to layout and placement of the devices on a circuit board.

Description

Technical Field

[0001] The utility model relates to the technical field of composite smoke sensors, in particular to a composite thermal runaway detector for a battery pack. Background Art

[0002] With the vigorous development of new energy, the safety of lithium batteries has received more and more attention. Lithium battery cells, such as lithium iron phosphate and ternary lithium battery cells, will not only produce smoke when thermal runaway occurs, but also carbon monoxide CO, hydrogen H2 and volatile organic compounds VOC. When conducting safety monitoring on lithium battery packs, it is necessary not only to monitor the smoke generated by fire, but also to monitor gases such as carbon monoxide, hydrogen, and volatile organic compounds. In the prior art, smoke sensors are usually used as the main sensors to monitor the smoke generated during the thermal runaway of lithium batteries and even the thin smoke particles in the early thermal runaway; gas sensors are used as auxiliary sensors to monitor other gases, which creates the need to set up multiple sensors at the same time and perform sensor information fusion.

[0003] With the popularization of battery pack technology, especially water cooling technology, most battery packs use sealed technology. If you want to accurately monitor the thermal runaway of lithium batteries, you must go deep into the battery pack. This is also the reason why the latest GB / T42288-2022 "Safety Regulations for Electrochemical Energy Storage Power Stations" emphasizes that the minimum protection unit of the automatic fire extinguishing system of the lithium-ion battery room / cabin should be the battery module, and each battery module can be individually configured with a fire extinguishing medium nozzle or a fire detector. However, the problem that follows is the size and cost of the monitoring module. One of the purposes of using water cooling technology in the battery pack is to improve the energy density and temperature balance of the battery pack. Therefore, there is little available space inside the battery pack, or in order to increase the energy density, the free space inside the battery pack needs to be as small as possible, so the thermal runaway monitoring module used in the battery pack is also as small as possible.

[0004] In the prior art, traditional smoke sensors need to consider the layout of optical devices and the design of optical mazes. Gas sensors based on electrochemical principles, such as sensors for detecting carbon monoxide CO and hydrogen H2, are generally large in size. Taking Figaro's carbon monoxide sensor as an example, these sensors will take up a large space, and such sensors are generally cylindrical in shape with a metal shell. Direct integration with traditional smoke sensors and controlling the volume will cause optical reflection problems, so the optical maze of traditional smoke sensors must be modified accordingly to ensure that the optical devices of the smoke sensors will not be interfered with. For example, the technical solution disclosed in patent CN202320267741.0 adopts a thin design of a horizontal maze to adapt to the characteristics of the battery pack, but the discrete optical devices and the mechanism that cooperates with the optical design all need to occupy space. If multiple sensors including smoke sensors are integrated in a limited space, it will take up a very large space. The large volume will make it impossible to use the composite detector of multiple sensors in application scenarios with limited space. Summary of the invention

[0005] In order to solve the problem that the composite smoke detectors integrating multiple sensors in the prior art are large in size and thus have limited usage scenarios, the utility model provides a composite thermal runaway detector for a battery pack, which effectively reduces the size of the detector on the basis of realizing the function of composite monitoring of gas and smoke, so that it can be suitable for more application scenarios.

[0006] The structure of the utility model is as follows: a composite thermal runaway detector for a battery pack, comprising: a housing, a circuit board arranged in the inner cavity of the housing, and a core component mounted on the circuit board, wherein the core component comprises: a connector, a photoelectric smoke sensor, and a gas sensor; characterized in that:

[0007] The photoelectric smoke sensor adopts a discrete light-emitting tube and a patch-type receiving tube;

[0008] The optical main axis of the light emitting tube is parallel to the circuit board, and the receiving tube and the gas sensor are arranged around the optical main axis of the light emitting tube; no core device higher than the bottom edge of the optical sensitive area is arranged in the optical sensitive area of ​​the light emitting tube;

[0009] The shell is a closed structure; smoke inlet holes are evenly arranged on the shell; gaps are maintained between the core components in the shell and between the core components other than the connector and the shell; the core components are projected on the shell adjacent to them, and the smoke inlet holes covered by the projection cannot exceed 1 / 2 of all the smoke inlet holes, and the smoke inlet holes not covered by the projection of the core components are distributed on the side walls of the shell in different directions.

[0010] It is further characterized by:

[0011] The receiving tube comprises: a main receiving tube and an auxiliary receiving tube;

[0012] The main receiving tube is implemented based on a patch type photoelectric receiving tube and is arranged below the optical sensitive area; the auxiliary receiving tube is arranged outside the optical sensitive area and is located between the main receiving tube and the light emitting tube;

[0013] At least one main receiving tube is provided; the auxiliary receiving tubes are provided in pairs and are symmetrically arranged based on the optical main axis, and at least one pair of the auxiliary receiving tubes is provided;

[0014] The gas sensors include: a carbon monoxide CO sensor, a hydrogen H2 sensor and a VOC volatile gas sensor;

[0015] On the installation plane in the housing, the gaps between the core components and between the core components other than the connector and the housing are maintained to be no less than 5 mm; the height of the components on the corresponding PCB circuit board within the coverage range of the optical sensitive area of ​​the light-emitting tube is no higher than 2 mm;

[0016] The specific installation position of the light emitting tube meets the following conditions:

[0017] Assume that the light-emitting point of the light-emitting tube is point O, and point O is set at the midpoint of the distance between the upper surface of the circuit board and the inner surface of the top of the shell;

[0018] It also includes: a light blocking device, which is arranged between the light emitting tube and the main receiving tube;

[0019] Assume that the angle between the two sides of the optical sensitive area of ​​the light-emitting tube is α, the distance from point O to the circuit board is h, the distance from point O to the farthest edge of the photosensitive area of ​​the main receiving tube is d, the height of the main receiving tube is dforward, dforward≤2mm; according to the triangular relationship, the following relationship is obtained:

[0020] h≥d×tan(α / 2)+2;

[0021] The shapes of the shell include: a cylinder and a prism with a square or rectangular cross section;

[0022] The housing is a prism with a rectangular cross section; the connector is arranged on one side of the rectangle, located on one side of the midpoint of the side, and the distance between the connector and the adjacent rectangular vertex is greater than or equal to 5 mm;

[0023] The light-emitting point O of the light-emitting tube is set at the midpoint of the distance between the circuit board and the top of the shell; in the horizontal direction, the optical principal axis of the light-emitting tube is not parallel to any side of the rectangle, and the angle between the optical principal axis of the light-emitting tube and the side where the connector is located is an acute angle; on the optical principal axis of the light-emitting tube, point O is farthest from the connector;

[0024] The angle between the two horizontal sides of the optical sensitive area of ​​the light-emitting tube does not exceed 30°; no device higher than 2 mm is set on the corresponding PCB circuit board within the coverage range of the optical sensitive area of ​​the light-emitting tube;

[0025] The main receiving tube is arranged below the optical sensitive area, and the two auxiliary receiving tubes are symmetrically arranged outside the optical sensitive area based on the optical main axis of the light-emitting tube, and are located between the main receiving tube and the light-emitting tube;

[0026] The largest gas sensor and the light-emitting tube are placed near the two vertices of the side away from the connector; the largest gas sensor and the connector are located at diagonal positions; the second largest gas sensor is arranged between the light-emitting tube and the connector; the device or sensor no higher than 2mm is arranged below the optical sensitive area.

[0027] The present application provides a composite thermal runaway detector for a battery pack, which monitors smoke by setting up a photoelectric smoke sensor and detects gas generated during combustion by using a gas sensor, thereby meeting the functional requirements of the composite thermal runaway detector; at the same time, because the use scenario of the lithium battery battery pack itself is a sealed environment, this solution does not need to design a complex maze structure, effectively reducing the overall size and saving costs; the photoelectric smoke sensor uses a discrete device light-emitting tube combined with a surface-mount receiving tube to achieve a new optical design, which can not only save costs, but also take advantage of the surface-mount receiving tube to reduce the overall size At the same time, the SMD receiving tube is also conducive to the layout and placement of devices on the circuit board; in addition to reducing the volume, the SMD optical receiving tube has the natural advantage of electromagnetic shielding. At the same time, the copper plating of the circuit board can effectively reduce electromagnetic radiation and improve monitoring accuracy; the smoke inlet holes are evenly arranged on the shell, and the position of each internal device is controlled to keep gaps between the devices, ensuring that smoke and gas at various angles can smoothly enter the shell, meeting the detection requirements of different azimuths; the receiving tube and the gas sensor are arranged around the optical main axis of the light-emitting tube, further ensuring that the technical solution of the present application can meet the detection requirements of different azimuths. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an example of the layout of the composite thermal runaway detector in this application;

[0029] Figure 2 Schematic diagram of the optical structure of the photoelectric smoke sensor in this application. DETAILED DESCRIPTION

[0030] The present application includes a composite thermal runaway detector for a battery pack, which includes: a shell of an outer shell, a circuit board arranged in an inner cavity of the shell, and core components installed on the circuit board, the core components including: a connector, a photoelectric smoke sensor and a gas sensor.

[0031] The core components are set on the circuit board, and the connector is close to the shell to realize the data link between the detector and the outside and connect the detector to the power supply. The shape of the shell includes: a cylinder and a prism with a square or rectangular cross section. The specific shape is selected according to actual needs.

[0032] The photoelectric smoke sensor uses a discrete light-emitting tube and a patch-type receiving tube. This application changes the layout of the traditional photoelectric smoke sensor, adopts the light-emitting tube mode commonly used in the horizontal maze, cancels the complex maze structure design, and the receiving tube adopts a combination mode of multiple patch devices, which can reduce space.

[0033] The optical axis of the light-emitting tube is parallel to the circuit board. The receiving tube and the gas sensor are arranged around the optical axis of the light-emitting tube. No core components are arranged in the optical sensitive area of ​​the light-emitting tube that are higher than the bottom edge of the optical sensitive area to avoid the reflection of components affecting the optical components. Usually, the core components arranged in the optical sensitive area coverage of the light-emitting tube are not higher than 2mm.

[0034] In actual application, the light-emitting tube of the photoelectric smoke sensor and a larger gas sensor occupy a corner of the composite detector respectively, and are not on the same side as the connector. Placing the light-emitting tube in the corner is conducive to obtaining the maximum optical path, and placing the larger gas sensor in another corner is conducive to ensuring the smoothness of the gas detection, while avoiding the larger gas sensor from becoming the light-emitting surface on the light path of the light-emitting tube. The gas sensor is located at the edge or corner of the composite thermal runaway detector and is away from the optically sensitive area of ​​the photoelectric smoke sensor; except for the photoelectric smoke sensor and the larger gas sensor, the remaining gas sensors can be placed in the main light path direction of the light-emitting tube if they are not higher than 2mm, otherwise they can be placed on the side of the main light path, leaving space for smoke and air intake.

[0035] In a specific implementation, the gas sensor includes: two or more of a carbon monoxide CO sensor, a hydrogen H2 sensor, a volatile gas VOC sensor, and the like.

[0036] Except for the smoke sensor, large-size sensors cannot be placed in the center of the detector module to avoid blocking the optical path and causing optical reflection. The sensors can only be arranged at the corners of the composite detector. The sensors are arranged separately around the optical axis of the light-emitting tube, which can not only keep the smoke and air intake channels unobstructed, but also provide a certain smoke detection space for the internal smoke sensor, creating a maze-like effect.

[0037] The shell in the present application is a closed structure; because the interior of the lithium battery pack is a sealed space, it does not encounter the problem of ambient light interference of traditional external smoke sensors; in particular, a closed shell is set in the present application to ensure that no external ambient light will affect the use of the optoelectronic device. Based on the use environment and the closed shell, the present application simplifies the optical design of the maze or even does not use the maze to save space, optimize the optical structure, and reduce costs. Therefore, compared with the traditional way of setting up a maze for photoelectric smoke sensors, the technical solution of the present application effectively reduces the volume of the equipment. At the same time, the outer shell of the gas sensor has a very high reflectivity. If it is placed on the optical path of the photoelectric smoke sensor, it will cause a large reflection, which will seriously affect the operation of the smoke sensor. This is a problem that is easy to think of, but if the traditional discrete device design plus the corresponding shading mechanism is installed, it will take up a lot of space. Therefore, it is beneficial to optimize the structure and enclose an internal optical detection space by placing a high-reflectivity large-volume gas sensor at the corners of the conforming detector.

[0038] The smoke inlet holes are evenly arranged on the shell; gaps are maintained between the core components in the shell and between the core components other than the connector and the shell; the core components are projected on the adjacent shell, and the smoke inlet holes covered by the projection cannot exceed 1 / 2 of all the smoke inlet holes, and the smoke inlet holes not covered by the projection of the core components are distributed on the side walls of the shell in different directions to ensure that sufficient smoke and air intake space is left. Figure 1 In the embodiment, the smoke entering from all directions is shown with reference to the arrow airflow direction 6 outside the housing 7. In this embodiment, on the mounting plane inside the housing, the gap between the core components and between the core components other than the connector and the housing is maintained at a gap of not less than 5 mm.

[0039] The receiving tube includes: a main receiving tube and an auxiliary receiving tube; the main receiving tube is implemented based on a patch type photoelectric receiving tube and is arranged below the optical sensitive area; the auxiliary receiving tube is arranged outside the optical sensitive area and is located between the main receiving tube and the light emitting tube. At least one main receiving tube is arranged; the auxiliary receiving tubes are arranged in pairs, at least one pair, and are arranged symmetrically based on the optical main axis. Neither the main receiving tube nor the auxiliary receiving tube will be directly illuminated by the light emitted by the light emitting tube, and is only suitable for detecting scattered light.

[0040] In this application, the light-emitting tube adopts a cylindrical separation device, and the main axis of the light emission after mounting is parallel to the PCB circuit board; the layout of the receiving tube is completely different from the classic design, and at least one SMD photoelectric receiving tube device is placed in the direction of the main optical axis to receive the smoke scattering model.

[0041] The detection area of ​​the smoke sensor is a cone-like three-dimensional area formed by the light emitted by the light emitting tube. Considering that a large optical angle will cause the light emitted by the light emitting tube to directly irradiate the circuit board, the components on the circuit board and the receiving tube, the light emitting tube is selected with a half-power angle θ between ±5° and ±30°. At the same time, a shading mechanism is required around it to ensure that the optical angle α does not exceed 30°. Figure 1 and 2 In the embodiment shown, it is ±15°, and the angle toward the PCB circuit board does not exceed 20°. Figure 1 and 2 In the embodiment shown, this is ±10°.

[0042] At least one main receiving tube is set in the receiving tube and placed below the main light path direction, mainly detecting forward scattered light and part of the backward scattered light; if there are more receiving tubes, the azimuth angle balance can be taken into account. If there are three receiving tubes, the other two receiving tubes are placed as auxiliary receiving tubes outside the optical angle α of the light-emitting tube and close to the transmitting tube, mainly used to detect scattered light information at different azimuth angles.

[0043] When selecting the receiving tube, the effective photosensitive area of ​​the SMD photoelectric receiving tube used in the photoelectric smoke sensor should not be less than 0.3 square millimeters to ensure sufficient sensitivity.

[0044] Assuming that the current data of the receiving tube collected under the same transmitting tube power condition is I=[I 21 ,I 22 ,I 23 ], each current threshold can be used as a basis for smoke detection. 21 It is the main photoelectric receiving tube, which mainly detects the forward scattered light and part of the backscattered photocurrent I M = I 21 ; Receiving tube I 22 and I 23 To assist the photoelectric receiving tube, it mainly detects the scattered light current I at different azimuth angles. A = I 22 + I 23 ;I M and I A Can be used as the basis for smoke detection independently, only I M The main photoelectric receiving tube is insufficient for judgment. Combined with the current value I of the main and auxiliary photoelectric receiving tubes AA method of judging smoke by ratio can be implemented. Assume that the ratio is R, R=I M / I A The fluctuation of this ratio reflects the imbalance of smoke intake, and the more stable the ratio is, the more stable the smoke in the maze tends to be.

[0045] In this application, the light-emitting angle of the light-emitting tube presents a spatial layout similar to that of a cone in space. The asymmetry of the smoke detection space will cause the problem of uneven azimuth of detection. To solve this problem, two auxiliary receiving tubes are placed outside the light-emitting direction of the light-emitting tube near the light-emitting tube to collect scattered light in different directions. Therefore, the combination of the main and auxiliary photoelectric receiving tubes helps to balance the smoke detection sensitivity at different azimuths. This is both a requirement of fire regulations and a requirement for judging the optical scattering of smoke at different azimuths during actual use.

[0046] Figure 1 The layout diagram of the composite thermal runaway detector is a layout diagram in actual size ratio. The circuit board 5 is fixed in the inner cavity of the shell through screw holes 51 and screws. The optical part of the smoke sensor consists of a light-emitting tube 1 and three receiving tubes: a main receiving tube 21, and auxiliary receiving tubes 22 and 23. The light-emitting tube 1 is located in the upper right corner and is an optical light-emitting diode. It can be a conventional cylindrical round-head light-emitting tube or a side-emitting device. The light-emitting center point of the light-emitting tube 1 is O, and OA is the optical axis and is parallel to the circuit board 5. The half-power angle θ of the light-emitting tube is preferably in the range of ±5° to ±30°. In this way, the main receiving tube 21 will receive forward scattered and partially backward scattered light, and the auxiliary receiving tubes 22 and 23 are located outside the optical angle α and are symmetrically placed. The optically sensitive area of ​​the light-emitting tube 1 is the cone covered by the optical angle α of the light-emitting tube 1, that is, Figure 1 and Figure 2 The range of ∠BOC is a pyramid-like body in space, with the vertex O. The arrangement space of the optical components of the photoelectric smoke sensor is guaranteed, and it is ensured that there is no obstruction and reflection within the range of ∠BOC covered by the optical angle α of the light-emitting tube 1.

[0047] To realize the optical angle α of the light-emitting tube 1, LED devices with small light-emitting angles, such as ±15°, can be selected. However, the ±15° here refers to the half power angle of the LED by default. There is also light intensity outside this angle, but the power density is lower. A mechanical light blocking device can be added to physically limit the optical angle α. Figure 1In the illustrated embodiment, a mechanical light blocking device is added: a light blocking mechanism 61, which physically blocks and limits the optical angle of the light-emitting tube 1 to ensure that there is no light outside the limited angle; the light blocking mechanism 61 includes an F-shaped light blocking structure, which limits the optical angle α of the light-emitting tube 1 to no more than ±15° and the angle toward the circuit board 5 and the opposite direction of the circuit board 5 (the default is the housing) to no more than ±10°, so as to ensure that all emitted light does not irradiate the circuit board or even directly irradiate the receiving tube, so that most of the light-emitting energy of the light-emitting tube is symmetrical in the space parallel to the circuit board. The above design can not only ensure that the light-emitting power is concentrated near the optical main axis, but also prevent the light outside the half-power angle from being reflected and interfered by other tall sensor housings through further limitation of the light blocking mechanism 61.

[0048] The edges of the angle α shown in the figure are OB and OC, so other tall sensors or sensors with highly reflective shells need to be placed outside the range of ∠BOC, and the area covered by ∠BOC cannot have any devices higher than 2mm to avoid reflection.

[0049] Taking Figaro carbon monoxide sensor TGS5141 as an example, its dimensions after installation are 14~15mm in diameter and 6~7mm in height. The outer shell is a metal reflective surface, so it cannot be placed in the area covered by ∠BOC. It should be placed in the upper left corner, which can ensure the ventilation effect without affecting the use of the photoelectric smoke sensor.

[0050] Carbon monoxide (CO) sensors have low power consumption due to their electrochemical nature and are generally the preferred sensor besides smoke sensors, and are preferably placed in the upper left corner.

[0051] Taking Figaro hydrogen sensor TGS2626 as an example, the diameter after installation is 8~9mm, the height is 7.5~8.5mm, and the shell is made of metal with a reflective surface, so it cannot be placed in the area covered by ∠BOC and must be placed outside. It can be placed in the middle between the light-emitting tube 1 and the connector 4, which will not cause reflection problems and is also conducive to the operation of the gas sensor.

[0052] Considering that the detector for battery pack generally needs a connector 4, the connector needs to be reliable and stable, and its size should not be too small. Taking the MOLEX connector 34793-0081 as an example, the space it occupies on the circuit board 5 is about 23x18mm, and the connector must be located at the edge of the PCB board. Therefore, when the light-emitting tube 1 and the sensor 31 each occupy two corners, the connector can only be located opposite them, and cannot be in the area covered by the ∠BOC, so it can only be located in the middle of the lower right corner. It is not placed in the lower right corner because of the problem of air intake and smoke intake to ensure the patency of the lower right corner. At the same time, the sensor 32 is placed in the middle of the right side, which can ensure both the air intake effect and the smoke intake problem on the right and lower right corners.

[0053] The sensor 31 with the largest volume is placed in the corner to ensure that there is no overlap with the ∠BOC area; the second largest sensor 32 is placed in the middle of the side of the light-emitting tube 1 away from the ∠BOC area. This layout can avoid the ∠BOC area and ensure the smoke and air intake channels of the composite detector. Here, the sizes of sensors 31, 32, and 33 are arranged from large to small by default. Regardless of the type and number of sensors, this principle must be respected to ensure the optimization of the space size. If there are other sensors in addition to sensor 31 and sensor 32, they are still placed according to this principle. This method ensures the smoothness of air intake and smoke intake, and does not affect the azimuth balance of smoke intake. In this example, the third sensor 33 is preferably a low-height and small-volume sensor placed in the coverage area of ​​∠BOC, with a height not exceeding 2mm. The typical device is the GM-503AVOC gas sensor of Weisheng Technology, with a length, width and height of 7x5x1.5mm, which meets the requirements.

[0054] Figure 2 Optical design of photoelectric smoke sensor. This is a side view of the optical design, which is used to explain the design features of this new optical layout. The light-emitting tube 1 is installed on the circuit board 5. No matter what packaging form the light-emitting tube 1 is, the optical axis OA of the light-emitting tube 1 after installation is parallel to the circuit board 5. The typical light-emitting tube 1 is a cylindrical round-head device. The mounting method can be direct insertion (manual bending needle), patch or direct insertion side-lighting device.

[0055] The light-emitting tube should be a photoelectric tube with a half-power angle θ between ±5° and ±30°. At the same time, a shading mechanism should be provided around it to ensure that the optical angle α emitted does not exceed ±15°, and the angle to the PCB circuit board and the upper cover 7 does not exceed ±10. Here, LITEON's LTE-4208M is selected, and the half-power angle θ of the light-emitting tube is ±10°, which meets the design requirements.

[0056] The light emitting center of the light emitting tube 1 is O, its optical principal axis is OA, and the edge of the optical angle α is ∠BOC. The basic principle of optical design is that there should be no reflective surface within the coverage of ∠BOC, so all large-volume sensors need to be moved outside the ∠BOC area. ∠BOC is a three-dimensional space similar to a cone. From the side view, the design needs to avoid the reflection of the emitted light through the housing 7 and the circuit board 5, or even directly irradiate the receiving tube 21. Because only the main receiving tube 21 of the typical three receiving tubes is in the optical path, only one is drawn here, and the other two auxiliary receiving tubes 22 and 23 are located outside the ∠BOC near the light emitting tube 1 for detecting backscattering. The three receiving tubes here can use SFH2705, 3.4mm from AMS-OSRAM. 2 The photosensitive area and photosensitive angle of 65° have very high photosensitivity. The device size is 2.5x2.2x0.6mm, which is very small and convenient for chip placement.

[0057] In order to further prevent the light in the OC direction from irradiating the receiving tube, it is necessary to optionally add a light blocking device 62 to the receiving tube 21 in the OC incident direction. The light blocking device 62 is arranged between the light emitting tube and the main receiving tube 21, and can be a separately installed part or a part of the upper and lower shells. Figure 2 As shown, assuming that the height of the light-emitting point of the light-emitting tube 1 is O, in this embodiment, point O is located at the midpoint of the distance from the upper surface of the circuit board 5 to the lower surface of the housing 7, and the distance from point O to the circuit board is h, and the distance from point O to the edge of the left photosensitive area of ​​the receiving tube 21 is d. The receiving tube 21 is recommended to be placed below the cone formed by ∠BOC, but not necessarily directly below OA.

[0058] Assumption: The height of the main receiving tube is dforward, dforward≤2mm;

[0059] The trigonometric relationship between h, d and angle α is as follows:

[0060] (h-2) / d=tan(α / 2)

[0061] In order to ensure that the optically sensitive area of ​​the light-emitting tube 1 has no reflective surface of the device, the following conditions must be met:

[0062] (h-2)≥d×tan(α / 2);

[0063] That is: h ≥ d × tan (α / 2) + 2;

[0064] The height hshad of the light blocking device 62 satisfies the following conditions:

[0065] Then: dforward≤ hshad <h。

[0066] If it is located directly below, it is necessary to ensure that OC does not irradiate the receiving tube 21 within the range of a distance of d=30mm. In this embodiment, h is 7.3mm, α / 2≤10°, to ensure that the optical angle in the direction toward the circuit board 5 and the upper shell 7 is as small as possible, so that the detector can be made thinner. In this example, the height hshad of the light-blocking device 62 is 1~3mm, depending on the specific situation. The 2mm in the above formula is the margin left, that is, the height of the device corresponding to the ∠BOC area on the circuit board is less than 2mm, so that theoretically there is no optical reflection problem. Similarly, the distance from point O to the upper cover is 7.3mm, so the distance from the upper surface of the PCB to the inner surface of the upper shell can be controlled at 14.6mm. The thickness of the entire module depends on the thickness of the outer shell, the thickness of the circuit board and the assembly space. The thickness of the entire module is controlled at 20mm or less.

[0067] After using the technical solution of the utility model, including the layout of the photoelectric smoke sensor and at least two gas sensors and the method of achieving azimuth balance, the overall size including the connector can be controlled within the range of 60x60mm circuit board, which is very beneficial to the narrow application space of the battery pack.

Claims

1. A composite thermal runaway detector for a battery pack, comprising: A housing, a circuit board arranged in the inner cavity of the housing, and core components mounted on the circuit board, wherein the core components include: a connector, a photoelectric smoke sensor, and a gas sensor; characterized in that: The photoelectric smoke sensor adopts a discrete light-emitting tube and a patch-type receiving tube; The optical main axis of the light emitting tube is parallel to the circuit board, and the receiving tube and the gas sensor are arranged around the optical main axis of the light emitting tube; no core device higher than the bottom edge of the optical sensitive area is arranged in the optical sensitive area of ​​the light emitting tube; The shell is a closed structure; the smoke inlet holes are evenly arranged on the shell; gaps are maintained between the core components in the shell and between the core components other than the connector and the shell; the core components are projected on the adjacent shell, and the smoke inlet holes covered by the projection cannot exceed 1 / 2 of all the smoke inlet holes, and the smoke inlet holes not covered by the projection of the core components are distributed on the side walls of the shell in different directions.

2. A composite thermal runaway detector for a battery pack according to claim 1, characterized in that: The receiving tube comprises: a main receiving tube and an auxiliary receiving tube; The main receiving tube is implemented based on a patch type photoelectric receiving tube and is arranged below the optical sensitive area; the auxiliary receiving tube is arranged outside the optical sensitive area and is located between the main receiving tube and the light emitting tube.

3. A composite thermal runaway detector for a battery pack according to claim 2, characterized in that: At least one main receiving tube is provided; the auxiliary receiving tubes are provided in pairs and are symmetrically arranged based on the optical main axis, and at least one pair of the auxiliary receiving tubes is provided.

4. A composite thermal runaway detector for a battery pack according to claim 1, characterized in that: The gas sensors include: a carbon monoxide CO sensor, a hydrogen H2 sensor and a VOC volatile gas sensor.

5. A composite thermal runaway detector for a battery pack according to claim 1, characterized in that: On the installation plane in the shell, the gaps between the core components and between the core components other than the connector and the shell are maintained at no less than 5 mm; the height of the core components on the corresponding PCB circuit board within the coverage range of the optical sensitive area of ​​the light-emitting tube is no higher than 2 mm.

6. A composite thermal runaway detector for a battery pack according to claim 1, characterized in that: The specific installation position of the light-emitting tube meets the following conditions: Assume that the light-emitting point of the light-emitting tube is point O, and point O is set at the midpoint of the distance between the upper surface of the circuit board and the inner surface of the top of the shell.

7. A composite thermal runaway detector for a battery pack according to claim 2, characterized in that: It also includes: a light blocking device, which is arranged between the light emitting tube and the main receiving tube; Assume that the angle between the two sides of the optical sensitive area of ​​the light-emitting tube is α, the distance from point O to the circuit board is h, the distance from point O to the farthest edge of the photosensitive area of ​​the main receiving tube is d, the height of the main receiving tube is dforward, dforward≤2mm; according to the triangular relationship, the following relationship is obtained: h≥d×tan(α / 2)+2.

8. A composite thermal runaway detector for a battery pack according to claim 1, characterized in that: The shapes of the shell include: a cylinder and a prism with a square or rectangular cross section.

9. A composite thermal runaway detector for a battery pack according to claim 2, characterized in that: The housing is a prism with a rectangular cross section; the connector is arranged on one side of the rectangle, located on one side of the midpoint of the side, and the distance between the connector and the adjacent rectangular vertex is greater than or equal to 5 mm; The light-emitting point O of the light-emitting tube is set at the midpoint of the distance between the circuit board and the top of the shell; in the horizontal direction, the optical principal axis of the light-emitting tube is not parallel to any side of the rectangle, and the angle between the optical principal axis of the light-emitting tube and the side where the connector is located is an acute angle; on the optical principal axis of the light-emitting tube, point O is farthest from the connector; The angle between the two horizontal sides of the optical sensitive area of ​​the light-emitting tube does not exceed 30°; no core device with a height of 2 mm is arranged on the corresponding PCB circuit board within the coverage range of the optical sensitive area of ​​the light-emitting tube; The main receiving tube is arranged below the optical sensitive area, and the two auxiliary receiving tubes are symmetrically arranged outside the optical sensitive area based on the optical main axis of the light-emitting tube, and are located between the main receiving tube and the light-emitting tube; The largest gas sensor and the light-emitting tube are placed near the two vertices of the side away from the connector; the largest gas sensor and the connector are located at diagonal positions; the second largest gas sensor is arranged between the light-emitting tube and the connector; the device or sensor no higher than 2mm is arranged below the optical sensitive area.

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