Ventilation system

Abstract

To provide a ventilation system that can suppress the occurrence of condensation when the system is stopped. [Solution] In the ventilation system, the supply air blower 2 generates an airflow that flows from outside through the supply air passage 15 into the room. The exhaust air blower 3 generates an exhaust airflow that flows from inside the room through the exhaust air passage 16 into the room. The outdoor intake temperature sensor 6 detects the temperature of the air drawn into the supply air passage 15 from outside. In the stopped state, when the operation of both the supply air blower 2 and the exhaust air blower 3 is stopped, the control device 5 determines, based on the temperature detected by the outdoor intake temperature sensor 6, whether or not to operate the exhaust air blower 3 while the supply air blower 2 remains stopped. If the control device 5 determines that exhaust air operation is necessary, it performs exhaust air operation.

Description

Technical Field

[0001] The present disclosure relates to a ventilation device.

Background Art

[0002] Patent Document 1 discloses a heat exchange ventilation device that supplies outdoor air into a room through an air supply passage in a casing, exhausts indoor air to the outside through an exhaust passage in the casing, and performs heat exchange between the outdoor air and the indoor air in a heat exchanger disposed in the casing. The supply of outdoor air into the room is performed by an air supply blower. The exhaust of indoor air to the outside is performed by an exhaust blower. The outdoor air is sucked into the air supply passage from an outdoor side suction port and supplied into the room through an indoor side blowout port from the air supply passage. The indoor air is sucked into the exhaust passage from an indoor side suction port and exhausted to the outside through an outdoor side blowout port from the exhaust passage.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional heat exchange ventilation device disclosed in Patent Document 1, during the operation of the heat exchange ventilation device, since the outdoor air flows through the air supply passage by the air supply blower and the indoor air flows through the exhaust passage by the exhaust blower, heat exchange between the outdoor air and the indoor air is forcibly performed in the heat exchanger. As a result, the temperature of the outdoor air becomes a temperature closer to the temperature of the indoor air at the indoor side blowout port than at the outdoor side suction port. Therefore, dew condensation due to the temperature difference between the outdoor air and the indoor air hardly occurs at the indoor side blowout port of the casing installed indoors.

[0005] However, when the heat exchange ventilation system is stopped, the supply fan and exhaust fan also stop operating. Therefore, when the indoor air pressure becomes negative relative to the outdoor pressure, outdoor air flows through the supply and exhaust ducts and enters the room through the indoor air outlet and indoor air intake. At this time, since the air flowing through both the supply and exhaust ducts is outdoor air, the heat exchanger does not exchange heat between the outdoor air and the indoor air. Consequently, when the heat exchange ventilation system is stopped, a temperature difference between the outdoor air and the indoor air is likely to occur at the indoor air outlet and indoor air intake, and condensation may occur at the indoor air outlet and indoor air intake due to this temperature difference.

[0006] This disclosure aims to solve the above-mentioned problems and to provide a ventilation device that can suppress the occurrence of condensation when the device is stopped. [Means for solving the problem]

[0007] The ventilation system according to this disclosure comprises a housing in which an air supply passage and an exhaust passage are formed inside; an air supply fan that generates an air supply flow that flows from outside through the air supply passage into the room; an exhaust fan that generates an exhaust flow that flows from inside the room through the exhaust passage to the outside; a heat exchanger disposed inside the housing that performs heat exchange between the air supply flow and the exhaust flow; a control device that controls the operation of the air supply fan and the exhaust fan, respectively; and an outdoor intake temperature sensor that detects the temperature of the air drawn into the air supply passage from outside. In an operation stop state in which the operation of the air supply fan and the exhaust fan are stopped, the control device determines, based on the temperature detected by the outdoor intake temperature sensor, whether or not to operate the exhaust fan while the air supply fan is stopped. If the control device determines that exhaust fan operation is necessary, it performs exhaust fan operation. [Effects of the Invention]

[0008] According to this disclosure, it is possible to suppress the occurrence of condensation when the ventilation system is stopped. [Brief explanation of the drawing]

[0009] [Figure 1] This is a configuration diagram showing a ventilation device according to Embodiment 1. [Figure 2] Figure 1 is a diagram showing the ventilation system when the supply air fan and exhaust air fan are both stopped. [Figure 3] Figure 2 is a diagram showing the ventilation system when the control device is operating the exhaust fan. [Figure 4] This flowchart shows the processing operation of the control device when the control mode of the control device in Figure 3 is the stop control mode. [Figure 5] This is a configuration diagram showing a ventilation device according to Embodiment 2. [Figure 6] This flowchart shows the processing operation of the control device when the control mode of the control device in Figure 5 is the stop control mode. [Figure 7] This is a configuration diagram showing a first example of a processing circuit that realizes the functions of the control device according to Embodiments 1 and 2. [Figure 8] This is a configuration diagram showing a second example of a processing circuit that realizes the functions of the control device according to Embodiments 1 and 2. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the subject matter of this disclosure will be described with reference to the attached figures. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are simplified or omitted as appropriate. The subject matter of this disclosure is not limited to the following embodiments, and any modification of any component of the embodiments or omission of any component of the embodiments is possible without departing from the spirit of this disclosure.

[0011] Embodiment 1. Figure 1 is a configuration diagram showing a ventilation device according to Embodiment 1. The ventilation device is a device that exchanges outdoor air with indoor air. The ventilation device is installed, for example, on the ceiling of a room. The ventilation device has a housing 1, an air supply fan 2, an exhaust fan 3, a heat exchanger 4, a control device 5, an outdoor intake temperature sensor 6, and an indoor intake temperature sensor 7. The air supply fan 2, exhaust fan 3, heat exchanger 4, control device 5, outdoor intake temperature sensor 6, and indoor intake temperature sensor 7 are arranged inside the housing 1.

[0012] The housing 1 is provided with an outdoor intake port 11, an indoor outlet port 12, an indoor intake port 13, and an outdoor outlet port 14. The outdoor intake port 11 and the outdoor outlet port 14 are located on one of a pair of end faces in the longitudinal direction of the housing 1. The indoor outlet port 12 and the indoor intake port 13 are located on the other of a pair of end faces in the longitudinal direction of the housing 1. The outdoor intake port 11 and the indoor intake port 13 face each other in the longitudinal direction of the housing 1. Also, the outdoor outlet port 14 and the indoor outlet port 12 face each other in the longitudinal direction of the housing 1.

[0013] Inside the enclosure 1, an air intake passage 15 and an exhaust passage 16 are formed.

[0014] The air supply passage 15 runs inside the housing 1 from the outdoor intake port 11, through the heat exchanger 4, to the indoor outlet port 12. Of the air supply passage 15, the section between the outdoor intake port 11 and the heat exchanger 4 is the air supply intake passage 15a. Of the air supply passage 15, the section passing through the heat exchanger 4 is the air supply heat exchanger passage 15b. Of the air supply passage 15, the section between the heat exchanger 4 and the indoor outlet port 12 is the air supply outlet passage 15c.

[0015] The exhaust air passage 16 reaches from the indoor side suction port 13 through the heat exchanger 4 to the outdoor side blowout port 14 inside the housing 1. Among the exhaust air passage 16, the section between the indoor side suction port 13 and the heat exchanger 4 is the exhaust suction side air passage 16a. Among the exhaust air passage 16, the section passing through the heat exchanger 4 is the exhaust heat exchanger air passage 16b. Among the exhaust air passage 16, the section between the heat exchanger 4 and the outdoor side blowout port 14 is the exhaust blowout side air passage 16c.

[0016] Inside the housing 1, a first partition wall 17a, a second partition wall 17b, a third partition wall 17c, and a fourth partition wall 17d are provided. The first partition wall 17a is a wall that partitions between the exhaust suction side air passage 16a and the supply air blowout side air passage 15c. The second partition wall 17b is a wall that partitions between the supply air suction side air passage 15a and the exhaust suction side air passage 16a. The third partition wall 17c is a wall that partitions between the supply air suction side air passage 15a and the exhaust blowout side air passage 16c. The fourth partition wall 17d is a wall that partitions between the exhaust blowout side air passage 16c and the supply air blowout side air passage 15c.

[0017] An outdoor suction duct 18a reaching outdoors is connected to the outdoor side suction port 11. An indoor blowout duct 18b existing indoors is connected to the indoor side blowout port 12. An indoor suction duct 18c existing indoors is connected to the indoor side suction port 13. An outdoor blowout duct 18d reaching outdoors is connected to the outdoor side blowout port 14.

[0018] The supply air blower 2 is arranged in the supply air passage 15. In the present embodiment, the supply air blower 2 is arranged in the supply air blowout side air passage 15c. The supply air blower 2 generates a supply air flow that flows from outdoors through the supply air passage 15 into the room.

[0019] The air supply blower 2 has an air supply fan and an air supply fan motor. The air supply fan motor is a drive unit that rotates the air supply fan by energizing the air supply fan motor. When the air supply fan rotates, an air supply flow flows through the air supply duct 15 from the outdoor suction port 11 to the indoor outlet 12. As a result, outdoor air is sucked into the air supply duct 15 as outdoor air OA (Outdoor Air) from the outdoors through the outdoor suction duct 18a and the outdoor suction port 11. The outdoor air OA sucked into the air supply duct 15 flows through the air supply duct 15 as an air supply flow and is then supplied into the room as supply air SA (Supply Air) through the indoor outlet 12 and the indoor duct 18b. The air volume of the air supply flow flowing through the air supply duct 15 changes according to the rotation speed of the air supply fan.

[0020] The exhaust blower 3 is arranged in the exhaust duct 16. In the present embodiment, the exhaust blower 3 is arranged in the exhaust outlet side duct 16c. The exhaust blower 3 generates an exhaust flow that flows from the room to the outdoors through the exhaust duct 16.

[0021] The exhaust blower 3 has an exhaust fan and an exhaust fan motor. The exhaust fan motor is a drive unit that rotates the exhaust fan by energizing the exhaust fan motor. When the exhaust fan rotates, an exhaust flow flows through the exhaust duct 16 from the indoor suction port 13 to the outdoor outlet 14. As a result, indoor air is sucked into the exhaust duct 16 as return air RA (Return Air) from the room through the indoor suction duct 18c and the indoor suction port 13. The return air RA sucked into the exhaust duct 16 flows through the exhaust duct 16 as an exhaust flow and is then discharged outdoors as exhaust air EA (Exhaust Air) through the outdoor outlet 14 and the outdoor duct 18d. The air volume of the exhaust flow flowing through the exhaust duct 16 changes according to the rotation speed of the exhaust fan.

[0022] The heat exchanger 4 performs heat exchange between the supply airflow through the supply airflow passage 15 and the exhaust airflow through the exhaust airflow passage 16. In the heat exchanger 4, a supply airflow passage layer in which the supply air heat exchange airflow passage 15b is formed and an exhaust airflow passage layer in which the exhaust air heat exchange airflow passage 16b is formed are stacked. When the heat exchanger 4 is viewed along the stacking direction of the supply airflow passage layer and the exhaust airflow passage layer, the direction along the supply air heat exchange airflow passage 15b and the direction along the exhaust air heat exchange airflow passage 16b are perpendicular to each other. In the heat exchanger 4, heat exchange takes place between the supply airflow through the supply air heat exchange airflow passage 15b and the exhaust airflow through the exhaust air heat exchange airflow passage 16b. The heat exchanger 4 is constructed by alternately stacking corrugated sheets and flat sheets. The supply air heat exchange airflow passage 15b and the exhaust air heat exchange airflow passage 16b are formed between the corrugated sheets and the flat sheets.

[0023] In the ventilation system, ventilation operation is performed by the operation of both the supply fan 2 and the exhaust fan 3. Ventilation operation is an operation in which the supply air flowing from the outside through the supply air passage 15 into the room and the exhaust air flowing from the room through the exhaust air passage 16 into the outside exchange outdoor air with indoor air. Figure 1 shows the ventilation system when ventilation operation is being performed.

[0024] When there is a temperature difference between the outdoor air and the indoor air, ventilation operation is performed, and the supply airflow exchanges heat with the exhaust airflow from the room in the heat exchanger 4. The supply airflow after heat exchange then flows into the supply air outlet side air passage 15c. As a result, the temperature of the supply airflow after heat exchange becomes closer to the temperature of the indoor air than the temperature of the supply airflow before heat exchange. Therefore, even when there is a temperature difference between the outdoor air and the indoor air, when ventilation operation is performed, a temperature difference is unlikely to occur between the supply airflow flowing through the supply air outlet side air passage 15c and the indoor air.

[0025] On the other hand, when ventilation is in operation, outside air OA, before heat exchange takes place in the heat exchanger 4, is drawn in as a supply airflow from the outdoor intake port 11 to the supply air intake side air passage 15a. Therefore, if there is a temperature difference between the outdoor air and the indoor air, a temperature difference is likely to occur between the supply airflow flowing through the supply air intake side air passage 15a and the indoor air when ventilation is in operation.

[0026] Furthermore, when ventilation is in operation, the return air RA from the room is drawn in as exhaust air from the indoor intake port 13 to the exhaust intake air passage 16a. Since the temperature of the return air RA is the same as the temperature of the indoor air, when ventilation is in operation, there is little temperature difference between the exhaust air flowing through the exhaust intake air passage 16a and the indoor air.

[0027] On the other hand, if there is a temperature difference between the outdoor air and the indoor air, when ventilation is performed, the exhaust flow in the heat exchanger 4 exchanges heat with the supply air flow from the outdoors, and the exhaust flow after heat exchange flows into the exhaust outlet side air passage 16c. As a result, the temperature of the exhaust flow after heat exchange becomes closer to the temperature of the outdoor air than the temperature of the exhaust flow before heat exchange. Therefore, if there is a temperature difference between the outdoor air and the indoor air, when ventilation is performed, a temperature difference is likely to occur between the exhaust flowing through the exhaust outlet side air passage 16c and the indoor air.

[0028] Therefore, during summer, the rainy season, and other times when the temperature of the outdoor air is higher than the temperature of the indoor air, the temperature of the air flowing through the intake air passage 15a and the exhaust air passage 16c tends to be higher than the temperature of the indoor air. As a result, during summer, the rainy season, and other times when the air flowing through the intake air passage 15a and the exhaust air passage 16c comes into contact with the outdoor side of the housing 1 and is cooled, making it easy for condensation to occur on the inner surface of the outdoor side of the housing 1. The outdoor side of the housing 1 is the part of the housing 1 that forms the intake air passage 15a and the exhaust air passage 16c, respectively.

[0029] Furthermore, in winter or other times when the temperature of the outdoor air is lower than the temperature of the indoor air, the temperature of the air flowing through the intake air passage 15a and the exhaust air passage 16c tends to be lower than the temperature of the indoor air. As a result, in winter or other times, the air flowing through the intake air passage 15a and the exhaust air passage 16c comes into contact with the outdoor side of the housing 1, cooling the indoor air surrounding the housing 1, which makes condensation likely to occur on the outer surface of the outdoor side of the housing 1.

[0030] In the ventilation system, insulation material 19 is attached to both the outdoor side of the housing 1 and the third partition wall 17c. This makes it difficult for heat to be transferred between the air flowing through the supply air intake passage 15a and the exhaust air outlet passage 16c and the indoor air, thereby suppressing the occurrence of condensation on the outdoor side of the housing 1.

[0031] The outdoor intake temperature sensor 6 is located in the intake side air passage 15a of the air supply passage 15. Therefore, the outdoor intake temperature sensor 6 detects the temperature of the outside air OA that is drawn into the air supply passage 15 from the outside. In other words, the outdoor intake temperature sensor 6 detects the temperature of the air in the air supply passage 15 before it passes through the heat exchanger 4.

[0032] The indoor intake temperature sensor 7 is located in the exhaust intake side air passage 16a of the exhaust air passage 16. Therefore, the indoor intake temperature sensor 7 detects the temperature of the air drawn in from the room into the exhaust air passage 16, i.e., the return air RA. In other words, the indoor intake temperature sensor 7 detects the temperature of the air in the exhaust air passage 16 before it passes through the heat exchanger 4. In this embodiment, thermistors are used as both the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7.

[0033] A remote controller (not shown) is installed inside the room. The remote controller can be operated by a person inside the room. The remote controller can communicate with the control unit 5 via wired or wireless connection. The control unit 5 receives signals from the remote controller, including operation signals and stop signals, corresponding to the operations performed on the remote controller.

[0034] The control device 5 controls the operation of the supply air blower 2 and the exhaust air blower 3, respectively. In this embodiment, a component containing a control board inside a case is arranged inside the housing 1 as the control device 5. The control device 5 is capable of acquiring the detected temperatures of the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7 via wired or wireless means.

[0035] The control mode of the control device 5 can be switched between ventilation control mode and stop control mode. The control mode of the control device 5 enters ventilation control mode when the control device 5 receives an operation signal from the remote controller. The control mode of the control device 5 also enters stop control mode when the control device 5 receives a stop signal from the remote controller. The state in which the control device 5 is in ventilation control mode continues until the control device 5 receives a stop signal from the remote controller. The state in which the control device 5 is in stop control mode continues until the control device 5 receives an operation signal from the remote controller.

[0036] When the control mode of the control device 5 is set to ventilation control mode, the control device 5 performs ventilation operation by operating the supply air blower 2 and the exhaust air blower 3, respectively. The control device 5 performs ventilation operation while maintaining its control mode in ventilation control mode. When ventilation operation is being performed, the control device 5 acquires the detected temperatures from the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7, respectively. In addition, when ventilation operation is being performed, the control device 5 controls the operation of the supply air blower 2 and the exhaust air blower 3, respectively, based on the detected temperatures from the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7. As a result, in the ventilation system, ventilation operation is performed with the airflow rates of the supply airflow and exhaust airflow being individually controlled by the control device 5 based on the temperatures of the outside air OA and the return air RA, respectively.

[0037] For example, assuming the temperature of the outside air OA is -10°C, the temperature of the return air RA from the room is 20°C, and the temperature exchange efficiency of the heat exchanger 4 is 75%, when ventilation is performed, the temperature of the supply air SA will be 12.5°C and the temperature of the exhaust air EA will be -2.5°C.

[0038] When the control mode of the control device 5 enters the stop control mode, the control device 5 stops the ventilation operation by stopping the operation of the supply air blower 2 and the exhaust air blower 3. As a result, the state of the ventilation system becomes a stopped state in which the operation of the supply air blower 2 and the exhaust air blower 3 is stopped. Hereinafter, this stopped state in which the operation of the supply air blower 2 and the exhaust air blower 3 is stopped will simply be referred to as the "stopped state".

[0039] Here, we will explain the airflow within the enclosure 1 when the ventilation system is stopped. Figure 2 is a configuration diagram showing the ventilation system when the supply air blower 2 and exhaust air blower 3 in Figure 1 are both stopped. In the stopped state, since the supply air blower 2 and exhaust air blower 3 are both stopped, no supply airflow or exhaust airflow is forcibly generated.

[0040] However, when the indoor air pressure becomes negative relative to the outdoor air pressure, the difference in air pressure between the outdoors and indoors causes an airflow from outdoors towards the indoors in both the supply air passage 15 and the exhaust air passage 16. As a result, outside air OA flows from the outdoor intake port 11 and the outdoor outlet port 14 into both the supply air passage 15 and the exhaust air passage 16. An example of when the indoor air pressure becomes negative relative to the outdoor air pressure is when the ventilation system is stopped after business hours or other business hours in a sanitary room such as a toilet where exhaust ventilation is performed continuously for 24 hours.

[0041] Due to the difference in air pressure between the outdoors and indoors, the outside air OA that flows into the supply air passage 15 and the exhaust air passage 16 flows through the supply air passage 15 and the exhaust air passage 16 respectively, and then flows out into the room as supply air SA from the indoor outlet 12 and the indoor inlet 13, respectively. Therefore, when the system is stopped, if the indoor air pressure becomes negative relative to the outdoors, an airflow in the exhaust air passage 16 occurs in the opposite direction to when ventilation is in operation. The amount of airflow in the supply air passage 15 and the exhaust air passage 16 when the system is stopped is less than the airflow volume of the supply airflow and exhaust airflow, respectively, when ventilation is in operation.

[0042] In this case, since the air flowing through both the supply air passage 15 and the exhaust air passage 16 is outside air OA, no heat exchange occurs between the air flowing through the supply air passage 15 and the exhaust air passage 16 in the heat exchanger 4. Therefore, when the unit is stopped, if the indoor air pressure becomes negative relative to the outdoor pressure, the outside air OA from outside will flow through the inside of the housing 1 without heat exchange in the heat exchanger 4. For example, if the temperature of the outside air OA is -10°C, when the unit is stopped, the temperature of the supply air SA flowing into the room through the inside of the housing 1 will also be -10°C.

[0043] If the portions of the housing 1 that form the supply air outlet side air passage 15c and the exhaust air intake side air passage 16a are considered to be the indoor side of the housing 1, then insulation material is not installed on the indoor side of the housing 1. Therefore, if there is a temperature difference between the outdoor air and the indoor air, condensation may occur on the indoor side of the housing 1.

[0044] When the system is stopped, the control mode of the control device 5 is set to stop control mode. Also, when the system is stopped, power is continuously supplied to the outdoor intake temperature sensor 6, and the control device 5 is able to acquire the temperature detected by the outdoor intake temperature sensor 6.

[0045] When the system is stopped, the control device 5 determines whether or not to operate the exhaust fan based on the temperature detected by the outdoor intake temperature sensor 6. Exhaust fan operation is the operation of the exhaust fan 3 while the supply fan 2 is stopped. If the control device 5 determines that exhaust fan operation is necessary, it will operate the exhaust fan. If the control device 5 determines that exhaust fan operation is unnecessary, it will not operate the exhaust fan.

[0046] Specifically, a lower temperature threshold and an upper temperature threshold are pre-set in the control device 5. The upper temperature threshold is a temperature threshold higher than the lower temperature threshold. When the system is stopped, if the temperature detected by the outdoor intake temperature sensor 6 is below the lower temperature threshold or above the upper temperature threshold, the control device 5 determines that exhaust is necessary. Also, when the system is stopped, if the temperature detected by the outdoor intake temperature sensor 6 does not meet the conditions for determining that exhaust is necessary, the control device 5 determines that exhaust is not necessary. In other words, when the system is stopped, if the temperature detected by the outdoor intake temperature sensor 6 is higher than the lower temperature threshold and lower than the upper temperature threshold, the control device 5 determines that exhaust is not necessary.

[0047] Figure 3 is a configuration diagram showing the ventilation system when the control device 5 in Figure 2 is operating the exhaust fan. When the exhaust fan is operating, the exhaust fan 3 is activated. This forces an exhaust flow from the inside to the outside into the exhaust air passage 16. Consequently, return air RA from the inside is drawn into the exhaust intake air passage 16a, making it difficult for a temperature difference to occur between the exhaust flow through the exhaust intake air passage 16a and the indoor air. Therefore, when the exhaust fan is operating, condensation is suppressed even in the part of the housing 1 that forms the exhaust intake air passage 16a, where insulation material is not installed.

[0048] Furthermore, when the exhaust fan is in operation, the supply fan 2 is stopped. As a result, when the indoor air pressure becomes negative relative to the outdoor pressure, an airflow from the outdoors to the indoors is generated in the supply air passage 15. At this time, since the exhaust airflow from the indoors is flowing through the exhaust air passage 16, heat exchange takes place in the heat exchanger 4 between the air flowing through the supply air passage 15 and the exhaust airflow. Consequently, the air that has undergone heat exchange flows through the supply air outlet passage 15c, making it difficult for a temperature difference to occur between the air flowing through the supply air outlet passage 15c and the indoor air. Therefore, when the exhaust fan is in operation, condensation is suppressed even in the part of the housing 1 that forms the supply air outlet passage 15c, where insulation material is not installed.

[0049] In this embodiment, when the exhaust fan is in operation, the airflow rate of the exhaust air in the exhaust air passage 16 is greater than the airflow rate in the supply air passage 15. In the heat exchanger 4, the lower the airflow rate of the supply air, the higher the temperature exchange efficiency in the supply air and the lower the temperature exchange efficiency in the exhaust air.

[0050] For example, let's assume that when the exhaust fan is running, the temperature exchange efficiency of the heat exchanger 4 is 80% in the supply air flow and 20% in the exhaust air flow. Under this assumption, if the temperature of the outside air OA is -10°C and the temperature of the return air RA from the room is 20°C, then when the exhaust fan is running, the temperature of the supply air SA will be 14°C and the temperature of the exhaust air EA will be 16°C.

[0051] Thus, even in a stopped state where condensation may occur on the housing 1, the operation of the exhaust fan suppresses the occurrence of condensation on the housing 1. Therefore, it can be said that the operation of the exhaust fan is an operation to suppress the occurrence of condensation on the housing 1 when the system is stopped.

[0052] For example, when the device is stopped, if the temperature of the outside air OA is -10°C or lower, the temperature of the outside air OA is likely to be lower than the temperature of the indoor air, making condensation more likely to occur on the enclosure 1. Also, for example, when the device is stopped, if the temperature of the outside air OA is +30°C or higher, the temperature of the outside air OA is likely to be higher than the temperature of the indoor air, making condensation more likely to occur on the enclosure 1.

[0053] Therefore, for example, the control device 5 can be pre-set to have a lower temperature threshold of -10°C and an upper temperature threshold of +30°C. In this case, when the unit is stopped, if the temperature detected by the outdoor intake temperature sensor 6, i.e., the temperature of the outside air OA, is -10°C or lower or +30°C or higher, the exhaust fan is operated to suppress the occurrence of condensation in the housing 1. Also, in this case, when the unit is stopped, if the temperature detected by the outdoor intake temperature sensor 6, i.e., the temperature of the outside air OA, is higher than -10°C and lower than +30°C, the possibility of condensation occurring in the housing 1 is considered low, and the exhaust fan is not operated.

[0054] The control device 5 can switch the control of the operation of the exhaust blower 3 between multiple operating levels, i.e., multiple airflow notches, where the amount of exhaust flow generated in the exhaust air passage 16 is different from each other. The operating level of the exhaust blower 3 corresponds to the rotation speed of the exhaust fan. Therefore, the higher the operating level of the exhaust blower 3, i.e., the higher the airflow notch of the exhaust blower 3, the higher the rotation speed of the exhaust fan and the greater the amount of exhaust flow generated. The control device 5 can also switch the control of the operation of the supply air blower 2 between multiple operating levels, i.e., multiple airflow notches, where the amount of supply air flow generated in the supply air passage 15 is different from each other.

[0055] The control device 5 operates the exhaust fan 3 according to a preset level among multiple operating levels of the exhaust fan 3, which is set in the control device 5, thereby performing exhaust fan operation. In this embodiment, the control device 5 operates the exhaust fan 3 according to the lowest operating level among multiple operating levels of the exhaust fan 3, which generates the smallest amount of exhaust flow, thereby performing exhaust fan operation.

[0056] Next, the operation of the ventilation system will be explained. When the control device 5 receives an operation signal from the remote controller, the control mode of the control device 5 changes to ventilation control mode. As a result, the control device 5 operates the supply air blower 2 and the exhaust air blower 3 to perform ventilation operation. When ventilation operation is performed, the supply air blower 2 and the exhaust air blower 3 are operated under the control of the control device 5. When ventilation operation is performed, the outdoor air and the indoor air are exchanged while heat exchange occurs.

[0057] When the control device 5 receives a stop signal from the remote controller, the control mode of the control device 5 changes to stop control mode. When the control mode of the control device 5 changes to stop control mode, the control device 5 stops the operation of the supply air blower 2 and the exhaust air blower 3. As a result, the ventilation system is shut down.

[0058] Figure 4 is a flowchart showing the processing operation of the control device 5 when the control mode of the control device 5 in Figure 3 is the stop control mode. When the control mode of the control device 5 is the stop control mode, the control device 5 stops the operation of the supply air blower 2 and the exhaust air blower 3, and then the processing of the control device 5 is repeated at regular intervals.

[0059] When the control mode of the control device 5 is in stop control mode, the control device 5 acquires the temperature detected by the outdoor intake temperature sensor 6 in step S1. After this, the control device 5 proceeds to step S2.

[0060] In step S2, the control device 5 determines whether the temperature detected by the outdoor intake temperature sensor 6 is below the lower temperature threshold. In this way, in step S2, the control device 5 determines, for example, whether the temperature of the outside air OA is below -10°C.

[0061] In step S2, if the temperature detected by the outdoor intake temperature sensor 6 is below the lower temperature threshold, the control device 5 determines that exhaust fan operation is necessary, and the control device 5 proceeds to step S3. In step S3, the control device 5 operates the exhaust fan 3 while keeping the supply fan 2 stopped, and then terminates the processing for that cycle.

[0062] If the temperature detected by the outdoor intake temperature sensor 6 in step S2 is higher than the lower temperature threshold, the control device 5 proceeds to step S4. In step S4, the control device 5 determines whether the temperature detected by the outdoor intake temperature sensor 6 is equal to or greater than the upper temperature threshold. Based on this, in step S4, for example, the control device 5 determines whether the temperature of the outside air OA is +30°C or higher.

[0063] In step S4, if the temperature detected by the outdoor intake temperature sensor 6 is above the upper temperature threshold, the control device 5 determines that exhaust fan operation is necessary, and the control device 5 proceeds to step S3. In step S3, the control device 5 operates the exhaust fan 3 while keeping the supply fan 2 stopped, and then terminates the processing for that cycle.

[0064] In step S4, if the temperature detected by the outdoor intake temperature sensor 6 is lower than the upper temperature threshold, the control device 5 determines that exhaust fan operation is unnecessary, and the control device 5 proceeds to step S5. In step S5, the control device 5 continues to avoid operating the exhaust fan by stopping the operation of both the supply fan 2 and the exhaust fan 3, and terminates the processing for that cycle.

[0065] Specifically, in steps S2 and S4, the control device 5 determines whether or not to operate the exhaust fan by comparing the temperature detected by the outdoor intake temperature sensor 6 with the lower temperature threshold and the upper temperature threshold. Furthermore, if the control device 5 determines that exhaust fan operation is necessary, it operates the exhaust fan in step S3. If it determines that exhaust fan operation is unnecessary, it avoids operating the exhaust fan in step S5.

[0066] In this type of ventilation system, the temperature of the air drawn into the supply air passage 15 from the outside is detected by the outdoor intake temperature sensor 6. When the supply air blower 2 and the exhaust air blower 3 are both stopped, the control device 5 determines, based on the temperature detected by the outdoor intake temperature sensor 6, whether or not to operate the exhaust air blower 3 while keeping the supply air blower 2 stopped. If the control device 5 determines that exhaust air operation is necessary, it performs exhaust air operation.

[0067] Therefore, when there is a risk of condensation occurring on the indoor side of the housing 1 while the unit is stopped, an exhaust airflow from the indoor to the outdoor side can be generated in the exhaust air passage 16. This prevents outside air OA from flowing into the room from the outdoors through the exhaust air passage 16 while the unit is stopped. In addition, when the unit is stopped, the outside air OA flowing into the room from the outdoors through the supply air passage 15 can be heat-exchanged with the exhaust airflow in the heat exchanger 4, bringing the temperature of the outside air OA flowing into the room through the supply air passage 15 closer to the temperature of the indoor air. Consequently, in the indoor side of the housing 1, when the unit is stopped, the temperature of the air flowing through the supply air passage 15 and the exhaust air passage 16 can be brought closer to the temperature of the indoor air. As a result, even without protecting the indoor side of the housing 1 with insulation material, the occurrence of condensation in the housing 1 while the unit is stopped can be suppressed. Furthermore, even if insulation material is not installed in the indoor air outlet duct 18b and indoor suction duct 18c located inside the room, the occurrence of condensation in the indoor air outlet duct 18b and indoor suction duct 18c can be suppressed.

[0068] In this ventilation system, dampers are provided in the housing 1 to prevent outside air OA from flowing into the supply air passage 15 and the exhaust air passage 16 when the indoor air pressure becomes negative relative to the outdoor pressure, thereby suppressing condensation when the system is stopped. However, in this case, since dampers need to be provided in the housing 1, it not only increases the effort required to manufacture the ventilation system but also makes the ventilation system larger. Alternatively, in a ventilation system, condensation when the system is stopped can also be suppressed by attaching insulation material to the indoor side of the housing 1. However, in this case, since insulation material needs to be attached to the indoor side of the housing 1, it increases the effort required to manufacture the ventilation system and also increases the manufacturing cost of the ventilation system. In contrast, in the ventilation system according to this embodiment, there is no need to provide dampers in the housing 1 and there is no need to attach insulation material to the indoor side of the housing 1. Therefore, in the ventilation system according to this embodiment, the burden of manufacturing the ventilation system is reduced, and the size of the ventilation system is suppressed, while easily suppressing condensation when the system is stopped.

[0069] Furthermore, when the unit is stopped, if the temperature detected by the outdoor intake temperature sensor 6 falls below the lower temperature threshold or above the upper temperature threshold, the control device 5 determines that exhaust is necessary. This makes it possible to more reliably suppress the occurrence of condensation in the housing 1 when the unit is stopped.

[0070] Furthermore, the control device 5 is capable of switching the control of the operation of the exhaust fan 3 between multiple operating levels, each with a different amount of exhaust flow generated. The control device 5 operates the exhaust fan 3 at the lowest operating level, which has the smallest amount of exhaust flow generated, to perform exhaust fan operation. As a result, the power consumption of the exhaust fan 3 is reduced when the unit is stopped, while suppressing condensation in the housing 1.

[0071] In Embodiment 1, the lower and upper temperature thresholds, which are pre-set in the control device 5, cannot be changed. However, at least one of the lower and upper temperature thresholds may be changeable by operating an external control device. In this case, the external control device could be a remote controller installed in the room, or a set of DIP switches installed in the control device 5. This allows the criteria for determining whether or not to operate the exhaust fan to be changed according to the operating environment of the ventilation device, and further reliably suppresses the occurrence of condensation when the device is stopped.

[0072] Embodiment 2. Figure 5 is a configuration diagram showing a ventilation system according to Embodiment 2. Figure 5 shows the ventilation system when the control device 5 is operating the exhaust fan in a stopped state. The ventilation system includes a housing 1, a supply fan 2, an exhaust fan 3, a heat exchanger 4, a control device 5, an outdoor intake temperature sensor 6, and an indoor intake temperature sensor 7, in addition to an outdoor intake humidity sensor 8.

[0073] The outdoor intake humidity sensor 8, along with the outdoor intake temperature sensor 6, is located in the intake side air passage 15a of the air supply passage 15. The outdoor intake humidity sensor 8 detects the humidity of the air drawn into the air supply passage 15 from the outdoors, i.e., the outside air OA. In other words, the outdoor intake humidity sensor 8 detects the humidity of the air in the air supply passage 15 before it passes through the heat exchanger 4.

[0074] The control device 5 can acquire not only the temperatures detected by the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7, but also the humidity detected by the outdoor intake humidity sensor 8, either via wired or wireless connection.

[0075] When ventilation operation is in progress, the control device 5 acquires the temperatures detected by the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7, as well as the humidity detected by the outdoor intake humidity sensor 8. Furthermore, when ventilation operation is in progress, the control device 5 controls the operation of the supply air blower 2 and the exhaust air blower 3 based on the temperatures detected by the outdoor intake temperature sensor 6 and the indoor intake temperature sensor 7, as well as the humidity detected by the outdoor intake humidity sensor 8.

[0076] When the system is stopped, power is continuously supplied to both the outdoor intake temperature sensor 6 and the outdoor intake humidity sensor 8. This allows the control device 5 to acquire the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8 when the system is stopped.

[0077] When the system is stopped, the control device 5 determines whether or not to operate the exhaust fan based on the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8. If the control device 5 determines that exhaust fan operation is necessary, it operates the exhaust fan. If the control device 5 determines that exhaust fan operation is unnecessary, it does not operate the exhaust fan.

[0078] Specifically, the control device 5 has a preset lower temperature threshold and upper temperature threshold, as well as a preset upper humidity threshold. The upper temperature threshold is higher than the lower temperature threshold. When the system is stopped, the control device 5 determines that exhaust is necessary if the temperature detected by the outdoor intake temperature sensor 6 falls below the lower temperature threshold. Also, when the system is stopped, the control device 5 determines that exhaust is necessary if the temperature detected by the outdoor intake temperature sensor 6 is above the upper temperature threshold, and the humidity detected by the outdoor intake humidity sensor 8 is above the upper humidity threshold.

[0079] Furthermore, in the stopped state, if the conditions for the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8 do not meet the conditions for determining whether exhaust is necessary, the control device 5 determines that exhaust is not necessary. That is, in the stopped state, if the temperature detected by the outdoor intake temperature sensor 6 is higher than the lower temperature threshold and the temperature detected by the outdoor intake temperature sensor 6 is lower than the upper temperature threshold, the control device 5 determines that exhaust is not necessary. Also, in the stopped state, if the temperature detected by the outdoor intake temperature sensor 6 is higher than the lower temperature threshold and the humidity detected by the outdoor intake humidity sensor 8 is lower than the upper humidity threshold, the control device 5 also determines that exhaust is not necessary. The other configurations are the same as in Embodiment 1.

[0080] Next, the operation of the ventilation system will be explained. Figure 6 is a flowchart showing the processing operation of the control device 5 when the control mode of the control device 5 in Figure 5 is the stop control mode. When the control mode of the control device 5 is the stop control mode, the control device 5 stops the operation of the supply air blower 2 and the exhaust air blower 3, and then the processing of the control device 5 is repeated at regular intervals.

[0081] When the control mode of the control device 5 is in stop control mode, in step S11, the control device 5 acquires the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8. After this, the control device 5 proceeds to step S12.

[0082] In step S12, the control device 5 determines whether the temperature detected by the outdoor intake temperature sensor 6 is below the lower temperature threshold.

[0083] In step S12, if the temperature detected by the outdoor intake temperature sensor 6 is below the lower temperature threshold, the control device 5 determines that exhaust fan operation is necessary, and the control device 5 proceeds to step S13. In step S13, the control device 5 performs exhaust fan operation and then terminates the processing for that cycle.

[0084] If the temperature detected by the outdoor intake temperature sensor 6 in step S12 is higher than the lower temperature threshold, the control device 5 proceeds to step S14. In step S14, the control device 5 determines whether the temperature detected by the outdoor intake temperature sensor 6 is equal to or greater than the upper temperature threshold, and whether the humidity detected by the outdoor intake humidity sensor 8 is equal to or greater than the upper humidity threshold.

[0085] In step S14, if the temperature detected by the outdoor intake temperature sensor 6 is above the upper temperature threshold and the humidity detected by the outdoor intake humidity sensor 8 is above the upper humidity threshold, the control device 5 determines that exhaust is necessary, and the control device 5 proceeds to step S13. In step S13, the control device 5 operates the exhaust fan and then terminates the processing for that cycle.

[0086] In step S14, if the conditions for the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8 are not conditions for determining whether exhaust is necessary, the control device 5 determines that exhaust is not necessary, and the control device 5 proceeds to step S15. That is, in step S14, if the temperature detected by the outdoor intake temperature sensor 6 is lower than the upper temperature threshold, or if the humidity detected by the outdoor intake humidity sensor 8 is lower than the upper humidity threshold, the control device 5 determines that exhaust is not necessary, and the control device 5 proceeds to step S15. In step S15, the control device 5 continues in a state where the operation of the exhaust fan is avoided, and terminates the processing of that cycle.

[0087] Specifically, in steps S12 and S14, the control device 5 determines whether or not to operate the exhaust fan by comparing the temperature detected by the outdoor intake temperature sensor 6 with the lower temperature threshold and the upper temperature threshold. If the control device 5 determines that exhaust fan operation is necessary, it operates the exhaust fan in step S13. If it determines that exhaust fan operation is unnecessary, it avoids operating the exhaust fan in step S15.

[0088] In this type of ventilation system, the humidity of the air drawn into the supply air passage 15 from the outdoors is detected by the outdoor intake humidity sensor 8. When the supply air fan 2 and exhaust air fan 3 are both stopped, the control device 5 determines whether or not to operate the exhaust air fan based on the temperature detected by the outdoor intake temperature sensor 6 and the humidity detected by the outdoor intake humidity sensor 8. If the control device 5 determines that exhaust operation is necessary, it operates the exhaust air fan. Therefore, the determination of whether or not to operate the exhaust air fan can be made by taking into account not only the temperature of the outside air OA but also the humidity of the outside air OA. This further improves the accuracy of the determination of whether or not to operate the exhaust air fan, and makes it possible to more reliably suppress the occurrence of condensation when the system is stopped. In particular, during the rainy season when the humidity of the outside air OA tends to rise, it is possible to more reliably suppress the occurrence of condensation when the system is stopped.

[0089] Furthermore, in the stopped state, the control device 5 determines that exhaust is necessary when the temperature detected by the outdoor intake temperature sensor 6 falls below the lower temperature threshold, or when the temperature detected by the outdoor intake temperature sensor 6 rises above the upper temperature threshold and the humidity detected by the outdoor intake humidity sensor 8 rises above the upper humidity threshold. This makes it possible to more reliably suppress the occurrence of condensation in the housing 1 when the unit is stopped.

[0090] In Embodiment 2, the lower temperature threshold, upper temperature threshold, and upper humidity threshold, which are pre-set in the control device 5, cannot be changed. However, at least one of the lower temperature threshold, upper temperature threshold, and upper humidity threshold may be changeable by operating an external control device. In this case, the external control device may be a remote controller installed in the room, or a plurality of DIP switches installed in the control device 5. In this way, the criteria for determining whether or not to operate the exhaust fan can be changed according to the operating environment of the ventilation device, and the occurrence of condensation when the device is stopped can be suppressed even more reliably.

[0091] Furthermore, in each of the above embodiments, the air supply fan 2 is located in the air supply outlet side air passage 15c. However, the invention is not limited to this, and the air supply fan 2 may also be located in the air supply intake side air passage 15a.

[0092] Furthermore, in each of the above embodiments, the exhaust blower 3 is located in the exhaust outlet side air passage 16c. However, the invention is not limited to this, and the exhaust blower 3 may also be located in the exhaust intake side air passage 16a.

[0093] Furthermore, in each of the above embodiments, the control device 5 operates the exhaust fan 3 at the lowest operating level among the multiple operating levels of the exhaust fan 3, which results in the smallest amount of exhaust flow generated, thereby performing exhaust fan operation. However, the operating level of the exhaust fan 3 when performing exhaust fan operation is not limited to the lowest operating level. For example, the control device 5 may perform exhaust fan operation by operating the exhaust fan 3 at the second lowest operating level among the multiple operating levels of the exhaust fan 3.

[0094] Furthermore, the functions of the control device 5 according to each of the above embodiments are realized by a processing circuit. Figure 7 is a configuration diagram showing a first example of a processing circuit that realizes the functions of the control device 5 according to embodiments 1 and 2. The processing circuit 100 in the first example is dedicated hardware.

[0095] Furthermore, the processing circuit 100 may include, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

[0096] Figure 8 is a configuration diagram showing a second example of a processing circuit that realizes the functions of the control device 5 according to Embodiments 1 and 2. The processing circuit 200 of the second example includes a processor 201 and a memory 202.

[0097] In the processing circuit 200, the functions of the control device 5 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 202. The processor 201 realizes the functions of the control device 5 by reading and executing the programs stored in memory 202.

[0098] A program stored in memory 202 can be said to cause the computer to execute the procedures or methods described above. Here, memory 202 refers to non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), and EEPROM (Electrically Erasable and Programmable Read Only Memory). Magnetic disks, flexible disks, optical disks, compact disks, minidiscs, DVDs, etc., also fall under the category of memory 202.

[0099] Furthermore, some of the functions of the control device 5 described above may be implemented using dedicated hardware, while others may be implemented using software or firmware.

[0100] In this way, the processing circuit can realize the above-described functions of the control device 5 through hardware, software, firmware, or a combination thereof.

[0101] The configurations shown in the embodiments described above are merely examples of the content of this disclosure. The embodiments can be combined with other known technologies. Some parts of the configurations of the embodiments can be omitted or modified without departing from the gist of this disclosure. [Explanation of symbols]

[0102] 1. Enclosure, 2. Intake fan, 3. Exhaust fan, 4. Heat exchanger, 5. Control device, 6. Outdoor intake temperature sensor, 8. Outdoor intake humidity sensor, 15. Intake air passage, 16. Exhaust air passage.

Claims

1. A housing with an internal intake air passage and an exhaust air passage, An air supply fan that generates an airflow that flows from the outside into the room through the aforementioned air supply passage, An exhaust fan that generates an exhaust flow that flows from the room through the exhaust air passage to the outside, A heat exchanger is located inside the aforementioned housing and performs heat exchange between the supply airflow and the exhaust airflow, A control device that controls the operation of the air supply fan and the exhaust fan, respectively. An outdoor intake temperature sensor that detects the temperature of the air drawn into the air supply passage from the outdoors, Equipped with, In the stopped state, when the operation of the supply air blower and the exhaust air blower are both stopped, the control device determines, based on the temperature detected by the outdoor intake temperature sensor, whether or not to operate the exhaust air blower while keeping the supply air blower stopped. The control device is a ventilation device that performs the operation of the exhaust fan when it determines that the operation of the exhaust fan is necessary.

2. The control device has a lower temperature threshold and an upper temperature threshold that is higher than the lower temperature threshold set in advance. In the aforementioned stopped operation state, if the temperature detected by the outdoor intake temperature sensor falls below the lower temperature threshold or above the upper temperature threshold, the control device performs the exhaust necessity determination according to claim 1.

3. The ventilation device according to claim 2, wherein at least one of the lower temperature threshold and the upper temperature threshold can be changed by operating an external control device.

4. An outdoor intake humidity sensor detects the humidity of the air drawn into the air supply duct from the outdoors. Equipped with, The ventilation device according to claim 1, wherein, in the aforementioned stopped state, the control device determines whether or not to operate the exhaust fan based on the temperature detected by the outdoor intake temperature sensor and the humidity detected by the outdoor intake humidity sensor, respectively.

5. The control device has a lower temperature threshold and an upper temperature threshold that is higher than the lower temperature threshold set in advance, as well as an upper humidity threshold set in advance. The ventilation device according to claim 4, wherein, in the stopped operation state, the control device performs the exhaust necessity determination when the temperature detected by the outdoor intake temperature sensor falls below the lower temperature threshold, or when the temperature detected by the outdoor intake temperature sensor is equal to or above the upper temperature threshold and the humidity detected by the outdoor intake humidity sensor is equal to or above the upper humidity threshold.

6. The ventilation device according to claim 5, wherein at least one of the lower temperature threshold, the upper temperature threshold, and the upper humidity threshold can be changed by operating an external control device.

7. The control device is capable of switching the control of the operation of the exhaust fan between a plurality of operating levels in which the amount of exhaust flow generated is different from each other. The ventilation device according to any one of claims 1 to 6, wherein the control device operates the exhaust fan at the lowest operating level among the plurality of operating levels, which has the smallest amount of exhaust flow generated.

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