Heat exchange system for wafer production

Abstract

The utility model provides a heat exchange system for wafer production, which comprises an automatic liquid supplementing device, a main machine table and a plurality of heat exchangers, and the plurality of heat exchangers are connected in parallel with the main machine table and used for exchanging heat with the main machine table. The automatic liquid supplementing device is connected with a plurality of heat exchangers in parallel through pipelines; the main machine table is in communication connection with the multiple heat exchangers and the automatic liquid supplementing device. When liquid supplementing is needed, the heat exchanger transmits a liquid supplementing signal to the main machine table, the main machine table judges the current running state, when the main machine table is in an idle state, the signal is fed back to the automatic liquid supplementing device, and therefore cooling liquid is supplemented into the corresponding heat exchanger according to the time period when the main machine table is in the idle state, and liquid supplementing operation is completed. Manual liquid adding can be avoided, the workload of equipment engineers is reduced, meanwhile, a host machine does not need to borrow the machine in advance, and time consumption of the machine is avoided.

Description

Technical Field

[0001] The utility model relates to the field of wafer manufacturing, and particularly relates to a heat exchange system for wafer production. Background Art

[0002] In the semiconductor industry, some machine tools such as EPI, RTP, and CVD in the Fab (clean room) need to use a Heater Exchange (heat exchanger) to cool the Wafer Susceptor (tray) and Heater in the Chamber. The most commonly used refrigerant is DI Water (deionized water). Since part of the DI Water will evaporate and be lost during the cooling cycle of the heat exchanger and the machine tool equipment, it is necessary to regularly supplement the DI Water in the Heater Exchange.

[0003] The existing method of supplementary liquid addition uses manual liquid addition, that is, personnel fill a plastic bucket with DI Water and then add the liquid from the filling port of the Heater Exchange to the designated position. However, the manual liquid addition method not only increases the workload and work burden of equipment engineers, but also requires personnel to borrow the machine at least one hour in advance to put the machine tool in the Down state (shutdown state), and then restart the machine after liquid addition, consuming the machine time of the machine tool. Summary of the Utility Model

[0004] In view of the above-mentioned disadvantages of the prior art, the utility model provides a heat exchange system for wafer production to improve the technical problems that the existing manual liquid addition method increases the work burden of operators and requires the machine tool to be in the Down state and then restarted after liquid addition, consuming the machine time of the machine tool.

[0005] To achieve the above object and other related objects, the utility model provides a heat exchange system for wafer production.

[0006] The utility model provides a heat exchange system for wafer production, which includes a main machine platform, a plurality of heat exchangers, and an automatic liquid supplement device; the main machine platform is used for wafer production and manufacturing; the plurality of heat exchangers are connected in parallel to the main machine platform for heat exchange with the main machine platform; the automatic liquid supplement device is connected to the plurality of heat exchangers through a parallel pipeline; the main machine platform is communicatively connected to the plurality of heat exchangers and the automatic liquid supplement device respectively.

[0007] In an example of the heat exchange system of the utility model, the automatic liquid supplement device includes a liquid storage tank and a first liquid supplement pump. The liquid storage tank is used to store the coolant; the inlet of the first liquid supplement pump is connected to the liquid outlet of the liquid storage tank through a pipeline, and the outlet of the first liquid supplement pump is connected to the plurality of heat exchangers through a parallel pipeline; the first liquid supplement pump is communicatively connected to the main machine platform.

[0008] In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device further includes a plurality of branch control valves, the plurality of branch control valves are communicatively connected to the main machine platform, and a single branch control valve is disposed on a parallel pipeline between the first liquid replenishing pump and a single heat exchanger.

[0009] In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device further includes a liquid replenishing control valve, and the liquid replenishing control valve is disposed on a connecting pipeline between the liquid storage tank and the inlet of the first liquid replenishing pump.

[0010] In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device further includes a first liquid replenishing pipeline, the first liquid replenishing pipeline includes a liquid replenishing inlet pipe and a parallel outlet pipe, the liquid storage tank is connected to the first liquid replenishing pump through the liquid replenishing inlet pipe, and the liquid replenishing control valve is disposed on the liquid replenishing inlet pipe; the first liquid replenishing pump is connected to the heat exchanger through the parallel outlet pipe; and a plurality of the branch control valves are disposed in parallel on the parallel outlet pipe.

[0011] In an example of the heat exchange system of the present utility model, the liquid replenishing control valve and the branch control valves adopt electric valves or pneumatic valves.

[0012] In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device further includes a liquid supply control valve, the liquid supply control valve has an inlet that can be connected to a factory service pipeline, and an outlet of the liquid supply control valve is connected to an inlet of the liquid storage tank through a pipeline.

[0013] In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device further includes a liquid level sensing assembly, and the liquid level sensing assembly is disposed in the liquid storage tank.

[0014] In an example of the heat exchange system of the present utility model, the liquid level sensing assembly includes a first liquid level sensor and a third liquid level sensor, the first liquid level sensor and the third liquid level sensor are disposed on a side wall of an inner cavity of the liquid storage tank, and the third liquid level sensor is located above the first liquid level sensor.

[0015] In an example of the heat exchange system of the present utility model, the liquid level sensing assembly further includes a second liquid level sensor, the second liquid level sensor is disposed on a side wall of the inner cavity of the liquid storage tank, and the second liquid level sensor is located between the first liquid level sensor and the third liquid level sensor.

[0016] The present utility model proposes a heat exchange system for wafer production. By setting an automatic liquid replenishment device to store coolant and replenish the heat exchanger, the automatic liquid replenishment device and the heat exchanger are communicatively connected to the main machine platform. The heat exchanger transmits a liquid replenishment signal to the main machine platform. According to the current operating state of the main machine platform, when the main machine platform is in the IDEL (idle state), a feedback signal is sent to the automatic liquid replenishment device. Thus, during the time period when the main machine platform is in the IDEL state, the coolant is replenished into the corresponding heat exchanger to complete the liquid replenishment operation. This can not only avoid manual liquid addition, reduce the workload of equipment engineers, but also eliminate the need for the main machine platform to borrow machines in advance, avoiding the consumption of machine time. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0018] Figure 1 It is a schematic diagram of the hardware connection in an example of the heat exchange system of the present utility model;

[0019] Figure 2 It is a schematic diagram of the signal connection in an example of the heat exchange system of the present utility model;

[0020] Figure 3 It is a schematic diagram of the connection structure of the liquid replenishment inlet pipe in an example of the heat exchange system of the present utility model.

[0021] Description of Component Labels

[0022] 100, heat exchanger; 200, automatic liquid replenishment device; 210, liquid storage tank; 220, first liquid replenishment pump; 230, branch control valve; 240, liquid replenishment control valve; 250, liquid supply control valve; 260, liquid level sensing assembly; 261, first liquid level sensor; 262, second liquid level sensor; 263, third liquid level sensor; 270, first liquid replenishment pipeline; 271, liquid replenishment inlet pipe; 2711, liquid replenishment hole; 272, parallel outlet pipe; 280, first liquid supply pipeline; 300, main machine platform; 400, factory service end. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following specific examples illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present utility model are for describing specific implementation manners and are not intended to limit the protection scope of the present utility model. The test methods without specific conditions noted in the following embodiments are generally carried out according to conventional conditions or according to the conditions recommended by each manufacturer.

[0024] When the embodiments give a numerical range, it should be understood that, unless otherwise stated in the present utility model, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present utility model, based on the understanding of those skilled in the art of the prior art and the description of the present utility model, any method, device, and material similar to or equivalent to the methods, devices, and materials described in the embodiments of the present utility model can also be used to implement the present utility model.

[0025] It should be noted that the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of clear narration and are not intended to limit the scope of implementation of the present utility model. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope of implementation of the present utility model.

[0026] To solve the technical problems that the existing heat exchanger requires manual liquid replenishment, which increases the workload of equipment engineers and consumes machine time, the present utility model provides a heat exchange system for wafer production. Through the communication connection between the automatic liquid replenishment device and the main machine platform, the automatic liquid replenishment of the heat exchanger is completed in real time according to the working state of the main machine platform, without manual liquid replenishment and restarting the machine after the machine is stopped.

[0027] To achieve the above and other related purposes, the present utility model provides a heat exchange system for wafer production.

[0028] Please refer to Figures 1 to 3, the present utility model provides a heat exchange system for wafer production. The heat exchange system includes a main machine platform 300, a plurality of heat exchangers 100, and an automatic liquid replenishing device 200. The main machine platform 300 can be any suitable type of device for semiconductor or wafer production, such as main equipment like EPI, RTP, CVD, etc. The main machine platform 300 is located in the Fab (cleanroom). The heat exchangers 100 and the automatic liquid replenishing device 200 are auxiliary devices for assisting the production of the main machine platform 300. The heat exchangers 100 and the automatic liquid replenishing device 200 are installed in the Sub-Fab (sub-clean area, which provides infrastructure and support services for the cleanroom). Among them, the plurality of heat exchangers 100 are respectively connected in parallel to the main machine platform 300 and are used for refrigeration and heat exchange with parts such as trays and heaters in the main machine platform 300. Different main machine platforms 300 are configured with different numbers of heat exchangers 100 according to actual production needs, so the number of heat exchangers 100 is not limited. The automatic liquid replenishing device 200 is connected to the plurality of heat exchangers 100 through a parallel pipeline. The automatic liquid replenishing device 200 is configured to: when the coolant in one group of heat exchangers 100 evaporates and loses coolant during the heat exchange process with the main machine platform 300 and the liquid level is lower than a preset value, the coolant is transported to the heat exchangers 100 through the automatic liquid replenishing device 200. The main machine platform 300 is respectively communicatively connected to the plurality of heat exchangers 100, and the main machine platform 300 is communicatively connected to the automatic liquid replenishing device 200. The automatic liquid replenishing device 200 is used for liquid replenishing connection with the plurality of heat exchangers 100. When the heat exchangers need to be replenished with liquid, the automatic liquid replenishing device 200 transports the deionized water, which is the coolant it stores, to the heat exchangers 100 to complete the liquid replenishment.

[0029] The process of the main machine 300 controlling the automatic liquid replenishing device 200 to automatically replenish liquid to the heat exchange system is specifically as follows. When the heat exchanger 100 needs to be replenished with liquid, the heat exchanger 100 transmits a liquid replenishing signal to the main machine 300. The main machine 300 automatically identifies the current operating state to determine whether liquid replenishment can be carried out. When the main machine 300 is in the IDEL (idle state) and the idle time of the IDEL is relatively long, and there is enough time to eliminate the temperature fluctuation after the liquid replenishment is completed, the main machine 300 sends a liquid replenishing signal to the automatic liquid replenishing device 200. The automatic liquid replenishing device 200 replenishes the heat exchanger 100 with liquid, completing the automatic liquid replenishment. It should be noted that the communication control between the main machine 300, the heat exchanger 100, and the automatic liquid replenishing device 200 is a conventional technical means of existing automation, such as line connection control, wireless connection control, etc.; details will not be elaborated here. In an example of the heat exchange system of the present utility model, the automatic liquid replenishing device 200 described in any of the above examples includes a liquid storage tank 210 and a first liquid replenishing pump 220; the liquid storage tank 210 is used to store the coolant, that is, deionized water; the inlet of the first liquid replenishing pump 220 is connected to the liquid outlet of the liquid storage tank 210 through a pipeline, and the first liquid replenishing pump 220 has an outlet that can be connected in parallel with multiple heat exchangers through pipelines; when liquid replenishment is required, taking the first liquid replenishing pump 220 as the power source, the coolant in the liquid storage tank 210 is replenished into the heat exchanger 100 through the pipeline; the first liquid replenishing pump 220 is communicatively connected to the main machine 300, and multiple heat exchangers 100 are respectively communicatively connected to the main machine 300; for controlling the automatic liquid replenishment of the automatic liquid replenishing device 200; specifically, when the coolant in the heat exchanger 100 evaporates and is lost to the point where liquid replenishment is required, the heat exchanger 100 transmits a signal to the main machine 300. The main machine 300 judges the working state of the current machine. When the main machine 300 is in the IDEL state, the current main machine 300 device is in a vacant or waiting task state, and at this time, the main machine 300 does not process products; the main machine 300 sends a signal to control the first liquid replenishing pump 220 to work, and replenishes the coolant in the liquid storage tank 210 into the heat exchanger 100. Since the main machine 300 works intermittently, when the main machine 300 is in the IDEL state and there is no product processing, after the coolant with a lower temperature in the first liquid replenishing pump 220 converges with the coolant with a higher temperature in the heat exchanger 100, there is relatively sufficient time to eliminate the temperature fluctuation caused by the converged coolant, which can avoid the impact on the product caused by the temperature fluctuation. Utilizing the IDEL state of the main machine 300 can not only avoid manual liquid addition and reduce the work burden of equipment engineers, but also avoid the need to stop product production and the main machine 300 from crashing and then restarting, thus avoiding the waste of machine time. In this embodiment, the first liquid replenishing pump 220 can be any suitable type of device that can provide power for the liquid to flow in the pipeline and can be obtained through general commercial means.

[0030] Please refer to Figure 1, in an example of the heat exchange system of the present utility model, the automatic liquid replenishing device 200 further includes a plurality of branch control valves 230, and the plurality of branch control valves 230 are communicatively connected to the main machine platform 300; each branch control valve 230 is disposed on a parallel pipeline between the outlet of the first liquid replenishing pump 220 and a single heat exchanger 100, and the on-off of the coolant in the pipeline between the first liquid replenishing pump 220 and the heat exchanger 100 on the corresponding parallel branch is controlled by each branch control valve 230, so as to independently replenish liquid for a plurality of heat exchangers 100. Specifically, the automatic liquid replenishing device 200 includes a first liquid replenishing pipeline 270, and the first liquid replenishing pipeline 270 includes a liquid replenishing inlet pipe 271 and a parallel outlet pipe 272; one end of the liquid replenishing inlet pipe 271 communicates with the coolant in the liquid storage tank 210, and the other end communicates with the inlet of the first liquid replenishing pump 220; one end of the parallel outlet pipe 272 communicates with the outlet of the first liquid replenishing pump 220, and the other end is divided into several parallel branches, and each parallel branch corresponds to a filling port of a heat exchanger 100; a branch control valve 230 is disposed on the pipeline of each parallel branch to control the on-off of the parallel branch. When the heat exchanger 100 on a certain branch needs to be replenished with liquid, the heat exchanger 100 on this branch transmits a signal to the main machine platform 300. When the main machine platform 300 is in the IDEL state, the main machine platform 300 transmits a signal to the branch control valve 230 on the branch that needs to be replenished with liquid to open and the first liquid replenishing pump 220 to operate, and the branch control valves 230 on other branches remain in the closed state, so as to replenish liquid for a single heat exchanger 100 that needs to be replenished with liquid.

[0031] Please refer to Figure 3 , in an example of the heat exchange system of the present utility model, the end of the liquid replenishing inlet pipe 271 communicating with the liquid storage tank 210 is a closed end, and this closed end is located at the bottom of the liquid storage inner cavity of the liquid storage tank 210. A plurality of liquid replenishing holes 2711 are opened on the side wall of the pipe body of the liquid replenishing inlet pipe 271 at this closed end. There is a certain height difference between the liquid replenishing holes 2711 and the closed end, and it is located below the coolant liquid level, so as to prevent sediment foreign matters from entering, and prevent pressure fluctuations and turbulence generated inside the pump due to uneven liquid inlet of the first liquid replenishing pump 220, which may cause the pump to whistle. Of course, those skilled in the art can understand that if there are no foreign matters or the function of preventing foreign matters from entering is not considered, the structural form of the end of the liquid replenishing inlet pipe 271 communicating with the liquid storage tank 210 in the liquid storage tank 210 may not be limited either.

[0032] Please refer to Figure 1, in an example of the heat exchange system of the present utility model, the automatic liquid replenishing device 200 further includes a liquid replenishing control valve 240, and the liquid replenishing control valve 240 is arranged on the connecting pipeline between the liquid storage tank 210 and the inlet of the first liquid replenishing pump 220; specifically, the liquid replenishing control valve 240 is arranged on the liquid replenishing inlet pipe 271 and is used to control the on-off of the liquid in the pipeline between the liquid storage tank 210 and the first liquid replenishing pump 220, so as to prevent the fluid from flowing back due to the pressure difference when the first liquid replenishing pump 220 stops working.

[0033] In an example of the heat exchange system of the present utility model, the liquid replenishing control valve 240 and the branch control valve 230 described in any of the above examples can be any suitable device types capable of controlling the on-off of the liquid in the pipeline. In this embodiment, the liquid replenishing control valve 240 and the branch control valve 230 adopt electric valves or pneumatic valves to control the on-off of the liquid in the pipeline, and both electric valves and pneumatic valves can be obtained through general commercial means.

[0034] Please refer to Figure 1 , in an example of the heat exchange system of the present utility model, the automatic liquid replenishing device 200 further includes a liquid supply control valve 250. The liquid supply control valve 250 has an inlet that can be connected to the pipeline of the factory service end 400. The outlet of the liquid supply control valve 250 is connected to the inlet of the liquid storage tank 210 through a pipeline. The liquid supply control valve 250 is used to control the on-off of the coolant delivery pipeline between the factory service end 400 and the liquid storage tank 210. Specifically, when the liquid in the liquid storage tank 210 is insufficient and liquid supply is required, the factory service end 400 transports the coolant to the liquid storage tank 210 through the first liquid supply pipeline 280, and a liquid supply control valve 250 is arranged on the first liquid supply pipeline 280 to control the on-off of the liquid in the pipeline; in this embodiment, the liquid supply control valve 250 adopts an electric valve or a pneumatic valve, and both can be obtained through general commercial means.

[0035] Please refer to Figure 1 , in an example of the heat exchange system of the present utility model, the automatic liquid replenishing device 200 further includes a liquid level sensing assembly 260. The liquid level sensing assembly 260 is used to monitor the liquid storage volume in the liquid storage tank 210. The liquid level sensing assembly 260 is arranged on the inner side wall of the tank of the liquid storage tank 210. When it is monitored that the liquid storage volume in the liquid storage tank 210 is relatively low, the liquid level sensing assembly 260 sends out a liquid supply signal, and the factory service end 400 feeds the coolant into the liquid storage tank 210 for storage and standby.

[0036] Please refer to Figure 1, in an example of the heat exchange system of the present utility model, the liquid level sensing assembly 260 includes a first liquid level sensor 261, a second liquid level sensor 262 and a third liquid level sensor 263. The first liquid level sensor 261 is disposed on the inner cavity side wall of the liquid storage tank 210 for monitoring the lowest liquid level in the liquid storage tank 210. When the liquid level in the liquid storage tank 210 is lower than the monitoring height of the first liquid level sensor 261, a signal is sent to the factory service terminal 400, and the factory service terminal 400 supplies the coolant. The liquid inlet port of the liquid replenishment inlet pipe 271 is located in the liquid storage tank 210 below the first liquid level sensor 261. The second liquid level sensor 262 is disposed on the inner cavity side wall of the liquid storage tank 210 and above the first liquid level sensor 261. When the coolant in the liquid storage tank 210 is replenished to the monitoring height of the second liquid level sensor 262, it is the reasonable liquid storage height of the liquid storage tank 210, and a signal can be transmitted to the factory service terminal 400 and the liquid supply control valve 250 to stop the liquid supply. The third liquid level sensor 263 is disposed on the inner cavity side wall of the liquid storage tank 210 and above the first liquid level sensor 261. The third liquid level sensor 263 is the highest liquid level monitoring height, and controls that the liquid level height in the liquid storage tank 210 cannot exceed the monitoring height of the third liquid level sensor 263. In this embodiment, the first liquid level sensor 261, the second liquid level sensor 262 and the third liquid level sensor 263 can be any suitable type of device capable of monitoring the liquid level height in the tank and capable of signal transmission, and can be obtained by general commercial means.

[0037] The heat exchange system for wafer production of the present utility model has the beneficial effects that it can automatically replenish the heat exchanger when the main machine is in an idle state, the main machine does not need to borrow the machine in advance and stop for liquid replenishment to avoid wasting machine time, and at the same time avoid manual intervention and reduce the workload of equipment engineers. Therefore, the present utility model effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance. The above embodiments are only illustrative of the principles and effects of the present utility model and are not intended to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A heat exchange system for wafer production, characterized in that: The heat exchange system comprises: Mainframe, used for wafer production and manufacturing; A plurality of heat exchangers, wherein the plurality of heat exchangers are connected in parallel to the main station for performing heat exchange with the main station; An automatic liquid replenishing device, wherein the automatic liquid replenishing device is connected to a plurality of the heat exchangers via parallel pipelines; and the main machine station is respectively communicatively connected to the plurality of the heat exchangers and the automatic liquid replenishing device.

2. The heat exchange system according to claim 1, characterized in that: The automatic liquid replenishing device comprises: A liquid storage tank for storing coolant; a first infusion pump, wherein the inlet of the first infusion pump is connected to the liquid outlet pipeline of the liquid storage tank, and the outlet of the first infusion pump is connected to the parallel pipelines of the plurality of heat exchangers; The first fluid infusion pump is communicatively connected to the host station.

3. The heat exchange system according to claim 2, characterized in that: The automatic fluid replenishment device also includes a plurality of branch control valves, which are communicatively connected to the main station, and a single branch control valve is arranged on a parallel pipeline between the first fluid replenishment pump and a single heat exchanger.

4. The heat exchange system according to claim 3, characterized in that: The automatic liquid replenishing device further includes a liquid replenishing control valve, which is disposed on a connecting pipeline between the liquid storage tank and an inlet of the first liquid replenishing pump.

5. The heat exchange system according to claim 4, characterized in that: The automatic fluid replenishment device also includes a first fluid replenishment pipeline, which includes a fluid replenishment inlet pipe and a parallel fluid outlet pipe. The fluid storage tank is connected to the first fluid replenishment pump via the fluid replenishment inlet pipe, and the fluid replenishment control valve is arranged on the fluid replenishment inlet pipe; the first fluid replenishment pump is connected to the heat exchanger via the parallel fluid outlet pipe; and a number of the branch control valves are arranged in parallel on the parallel fluid outlet pipe.

6. The heat exchange system according to claim 4, characterized in that: The liquid replenishment control valve and the branch control valve are electric valves or pneumatic valves.

7. The heat exchange system according to claim 2, characterized in that: The automatic liquid replenishing device also includes a liquid supply control valve, which has a liquid inlet that can be connected to a factory service end pipeline, and a liquid outlet of the liquid supply control valve is connected to the liquid inlet pipeline of the liquid storage tank.

8. The heat exchange system according to claim 2, characterized in that: The automatic liquid replenishing device also includes a liquid level sensor component, and the liquid level sensor component is arranged in the liquid storage tank.

9. The heat exchange system according to claim 8, characterized in that: The liquid level sensor assembly includes a first liquid level sensor and a third liquid level sensor. The first liquid level sensor and the third liquid level sensor are arranged on the inner cavity side wall of the liquid storage tank, and the third liquid level sensor is located above the first liquid level sensor.

10. The heat exchange system according to claim 9, characterized in that: The liquid level sensor assembly also includes a second liquid level sensor, which is disposed on a side wall of the inner cavity of the liquid storage tank and is located between the first liquid level sensor and the third liquid level sensor.

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