JP7511762B2 - Heat exchange type ventilation system - Google Patents

Description

The present disclosure relates to a heat exchange type ventilation device that ventilates while exchanging heat between outdoor air and indoor air using a heat exchanger.

When taking in outdoor air into a room, a heat exchange ventilation system transfers the thermal energy of the indoor air that has been conditioned by an indoor air conditioning unit to the outdoor air through a heat exchanger, thereby recovering thermal energy through ventilation while providing ventilation.

When the outdoor temperature drops in winter, a heat exchange ventilation system transfers the thermal energy of the exhausted indoor air to the outdoor air brought into the room in the heat exchanger. As the exhausted indoor air is cooled, the moisture held in the indoor air condenses into water droplets. If the outdoor temperature drops further, the water droplets freeze into ice, causing the heat exchanger to become clogged, resulting in a problem of reduced heat exchange efficiency or reduced exhaust airflow.

For this reason, in heat exchange ventilation systems, the temperature of the outdoor air being supplied is detected, and when the temperature of the outdoor air falls below a certain temperature, intermittent operation is performed in which the supply air blower is turned on and off repeatedly for a certain period of time, or the output of the supply air blower is reduced for a certain period of time to prevent the heat exchanger from clogging.

Patent Document 1 discloses a heat exchange type ventilation device that monitors the motor current value of an exhaust direct current (DC) motor equipped in an exhaust fan, detects clogging of the heat exchanger due to icing when the motor current value exceeds a predetermined value, and melts the ice by reducing the rotation speed of an intake DC motor equipped in an intake fan to prevent clogging of the heat exchanger. When the rotation speed of the intake DC motor is reduced, the ice can be melted, but the ventilation air volume of the heat exchange type ventilation device is limited.

JP 2015-190684 A

However, with the heat exchange type ventilation device of Patent Document 1, when the filter becomes clogged over time and is not caused by freezing of the heat exchanger, the motor current value exceeds a predetermined value, which reduces the rotation speed of the DC motor for supplying air. This causes a problem in that the ventilation air volume is unnecessarily restricted even when there is no need to melt the ice to prevent the heat exchanger from becoming clogged.

The present disclosure has been made in consideration of the above, and aims to provide a heat exchanger ventilation device that can accurately detect temporary clogging of a heat exchanger due to icing, improve the icing condition of the heat exchanger, and suppress unnecessary restrictions on ventilation air volume caused by the operation of improving the icing condition of the heat exchanger other than when the heat exchanger is temporarily clogged due to icing.

In order to solve the above-mentioned problems and achieve the object, the heat exchange type ventilation device according to the present disclosure includes a housing in which an exhaust air duct for exhausting indoor air to the outside and an intake air duct for supplying outdoor air to the inside are formed independently, an exhaust fan having an exhaust motor and disposed in the exhaust air duct to generate an exhaust flow flowing through the exhaust air duct, and an intake fan having an intake motor and disposed in the intake air duct to generate an intake air flow flowing through the intake air duct. The heat exchange type ventilation device includes a heat exchanger disposed across the intake air duct and the exhaust air duct to exchange heat between the intake air flow and the exhaust air flow, an exhaust filter disposed upstream of the heat exchanger in the exhaust air duct, an outdoor temperature detector for detecting the outdoor temperature, which is the temperature of the outdoor air, a current detector for detecting the motor current value flowing through the exhaust motor, and a controller for controlling the operation of the intake air fan and the exhaust air fan. When the outdoor temperature is below a predetermined temperature threshold, the control unit stores the current motor current value of the exhaust motor as a pre-freezing reference current value, and when the current motor current value of the exhaust motor after storing the pre-freezing reference current value is equal to or lower than a freezing determination current value that is smaller than the pre-freezing reference current value, determines that freezing has occurred in the heat exchanger, and performs freezing condition improvement control by reducing the air volume of the supply air blower below the air volume of the exhaust blower to melt the ice.

The heat exchange ventilation device disclosed herein has the advantage that it is possible to accurately detect temporary clogging of the heat exchanger due to icing, improve the icing condition of the heat exchanger, and suppress unnecessary restrictions on ventilation air volume caused by operations to improve the icing condition of the heat exchanger other than when the heat exchanger is temporarily clogged due to icing.

FIG. 1 is a schematic diagram showing a configuration of a heat exchange type ventilation device according to a first embodiment. FIG. 1 is a block diagram showing a functional configuration of a heat exchange type ventilation device according to a first embodiment. FIG. 1 is a characteristic diagram showing the relationship between the air volume and static pressure of a blower when constant command voltage control is performed on the blower in the first embodiment. FIG. 11 is a characteristic diagram showing the relationship between the motor current and the rotation speed of the blower when constant command voltage control is performed on the blower in the first embodiment. 1 is a first flowchart showing an example of an operation of detecting clogging due to ice formation in a heat exchanger and an operation of improving a state of ice formation in the heat exchanger in a heat exchange type ventilation device according to a first embodiment; 2 is a second flowchart showing an example of an operation of detecting clogging due to icing of the heat exchanger and an operation of improving the icing state of the heat exchanger in the heat exchange type ventilation device according to the first embodiment; FIG. 1 is a diagram for explaining an example of frost state improvement control in a heat exchange type ventilation device according to a first embodiment. FIG. 1 is a diagram showing an example of a hardware configuration of a processing circuit according to a first embodiment; FIG. 1 is a block diagram showing a functional configuration of another heat exchange type ventilation device according to a first embodiment.

Below, the heat exchange type ventilation device of the embodiment is described in detail with reference to the drawings.

Embodiment 1.
Fig. 1 is a schematic diagram showing the configuration of a heat exchanger type ventilation device 1 according to a first embodiment. Fig. 2 is a block diagram showing the functional configuration of the heat exchanger type ventilation device 1 according to the first embodiment. The heat exchanger type ventilation device 1 is a device capable of performing ventilation while performing heat exchange between an intake air flow and an exhaust air flow. The heat exchanger type ventilation device 1 operates for the purpose of 24-hour ventilation. Therefore, once the heat exchanger type ventilation device 1 starts operating, it basically does not stop operating except for maintenance.

The heat exchange type ventilation device 1 maintains a comfortable indoor air environment by ventilating the room by supplying air from outside to the room and exhausting air from the room to the outside. The heat exchange type ventilation device 1 also reduces the temperature difference between the air taken into the room and the air inside the room by exchanging heat between the supply air flow and the exhaust air flow, thereby reducing the burden of air conditioning in the room. The heat exchange type ventilation device 1 is installed in the space above the ceiling, for example.

The heat exchange type ventilation device 1 comprises a housing 1a, a heat exchanger 2, an intake air blower 3, an exhaust air blower 4, an intake air filter 5, an exhaust air filter 6, an indoor outlet section 7, an indoor intake section 8, an outdoor intake section 9, an outdoor outlet section 10, an outdoor temperature detection section 11, a control device 12, and a display section 13.

In the heat exchange type ventilation device 1, a heat exchanger 2 that exchanges heat between an intake airflow and an exhaust airflow is housed in a housing 1a. The housing 1a has a hexahedron shape, for example, a rectangular parallelepiped shape, and constitutes the main body of the heat exchange type ventilation device 1. Inside the housing 1a, there are an intake air duct 21 through which the intake airflow passes, an exhaust air duct 22 through which the exhaust airflow passes, and a partition wall 23 that separates the intake air duct 21 and the exhaust air duct 22. In FIG. 1, the intake air duct 21 is indicated by a dashed arrow. In FIG. 1, the exhaust air duct 22 is indicated by a solid arrow. In FIG. 1, the heat exchange type ventilation device 1 is shown in a state in which one surface of the housing 1a is removed from the housing 1a.

On one side 1b of the housing 1a, an indoor air outlet 7, which is an air supply outlet, an indoor air intake 8, which is an exhaust air intake, an outdoor air intake 9, which is an air supply intake, and an outdoor air outlet 10, which is an exhaust air outlet, are provided. An outdoor air supply duct (not shown) that connects the outside of the room to the outdoor air intake 9 is connected to the outdoor air intake 9, which is an air supply intake. An indoor air supply duct (not shown) that connects the room to the indoor air outlet 7 is connected to the indoor air intake 8, which is an exhaust air intake. An indoor exhaust duct (not shown) that connects the room to the indoor air intake 8 is connected to the indoor air intake 8, which is an exhaust air intake. An outdoor exhaust duct (not shown) that connects the outside of the room to the outdoor air outlet 10 is connected to the outdoor air outlet 10, which is an exhaust air outlet.

The heat exchanger 2 is provided across the intake air duct 21 and the exhaust air duct 22, and performs total heat exchange between the intake air flow and the exhaust air flow. The heat exchanger 2 has a primary air duct through which the exhaust air flow passes, and a secondary air duct through which the intake air flow passes. Inside the heat exchanger 2, the primary air duct and the secondary air duct intersect perpendicularly. The primary air duct and the secondary air duct are formed by a laminated body formed by alternately stacking and bonding flat paperboard and corrugated sheets, which are corrugated paperboard. In FIG. 1, the primary air duct and the secondary air duct are omitted from the illustration. The laminated body has a rectangular prism shape. The end faces located at both ends of the heat exchanger 2 in the stacking direction each have a square shape. The stacking direction is the direction in which the flat paperboard and the corrugated sheets are stacked, and is the depth direction of the paper in FIG. 1.

The supply air duct 21 is an air duct for supplying outdoor air, which is outdoor air, into the room, and has an upstream supply air duct 21a formed between the outdoor intake section 9, which is an air supply inlet, and the heat exchanger 2, a downstream supply air duct 21b formed between the heat exchanger 2 and the indoor outlet section 7, which is an air supply outlet, and an in-heat exchanger supply air duct 21c, which is the air supply air duct 21 inside the heat exchanger 2. That is, the upstream supply air duct 21a is an air duct upstream of the heat exchanger 2 in the supply air duct 21, and is an upstream supply air duct that communicates with the outside of the room. The downstream supply air duct 21b is an air duct downstream of the heat exchanger 2 in the supply air duct 21, and is a downstream supply air duct that communicates with the inside of the room.

The exhaust air duct 22 is an air duct for exhausting the return air, which is indoor air, to the outside of the room, and has an upstream exhaust air duct 22a formed between the indoor suction section 8, which is an exhaust intake port, and the heat exchanger 2, a downstream exhaust air duct 22b formed between the heat exchanger 2 and the outdoor outlet section 10, which is an exhaust outlet, and an exhaust air duct 22c inside the heat exchanger 2, which is the exhaust air duct 22 inside the heat exchanger 2. That is, the upstream exhaust air duct 22a is an air duct upstream of the heat exchanger 2, and is an upstream exhaust air duct that communicates with the room. The downstream exhaust air duct 22b is an air duct downstream of the heat exchanger 2, and is a downstream exhaust air duct that communicates with the outside of the room.

The heat exchange type ventilation device 1 has an intake fan 3 that takes in outdoor air and sends it indoors, and an exhaust fan 4 that takes in indoor air and sends it outdoors.

The intake air blower 3 is disposed in the downstream intake air duct 21b and generates an intake air flow from the outdoor intake section 9 toward the indoor outlet section 7. The intake air blower 3 includes an intake air fan 31 in an intake air blower casing 30 and a DC brushless motor that is an intake air DC motor 32 for rotating the intake air fan 31. The intake air blower 3 generates an intake air flow by rotating the intake air fan 31 with the intake air DC motor 32. The operation of the intake air blower 3 is controlled by the control section 123, which will be described later, by controlling the operation, stop and rotation speed of the intake air DC motor 32.

The air supply DC motor 32 has an air supply motor control circuit 320 that controls the drive of the air supply DC motor 32 and adjusts the load according to the control of the control unit 123 as a control circuit that is a feature of the DC motor. The air supply motor control circuit 320 can adjust the motor power of the air supply DC motor 32 by controlling control parameters such as the voltage output to the air supply DC motor 32, the motor current flowing through the air supply DC motor 32, and the rotation speed of the air supply DC motor 32. The control unit 123 can grasp the operating state of the air supply DC motor 32 by acquiring these control parameters. In the first embodiment, this feature of the DC motor is utilized, and the control unit 123 constantly monitors the control parameters of the air supply DC motor 32 to detect the clogging state of the exhaust filter 6 without using a pressure sensor that detects the pressure of the air duct or an air volume sensor that detects the air volume flowing through the air duct.

When the air supply motor control circuit 320 receives an output instruction from the control unit 123, it operates the air supply DC motor 32. Furthermore, when the load on the air supply blower 3 fluctuates, such as a change in air duct pressure, the load on the air supply DC motor 32 also changes, causing changes in the rotation speed, voltage, and motor current. The air supply motor control circuit 320 includes an air supply rotation speed detection unit 321, an air supply voltage detection unit 322, an air supply current detection unit 323, and an air supply communication unit 324.

The air supply rotation speed detection unit 321 detects the rotation speed of the air supply DC motor 32. The air supply voltage detection unit 322 detects the voltage supplied to the air supply DC motor 32. The air supply current detection unit 323 detects the motor current value, which is the current value of the motor current flowing through the air supply DC motor 32. The air supply communication unit 324 communicates with the control device 12. The air supply rotation speed detection unit 321, the air supply voltage detection unit 322, and the air supply current detection unit 323 transmit the detection results to the control unit 123 via the air supply communication unit 324.

The exhaust blower 4 is disposed in the downstream exhaust air duct 22b and generates an exhaust flow from the indoor suction section 8 toward the outdoor blower section 10. The exhaust blower 4 includes an exhaust fan 41 in an exhaust blower casing 40 and a DC brushless motor that is an exhaust DC motor 42 for rotating the exhaust fan 41. The exhaust blower 4 generates an exhaust flow by rotating the exhaust fan 41 with the exhaust DC motor 42. The operation of the exhaust blower 4 is controlled by the control section 123, which will be described later, by controlling the operation, stop and rotation speed of the exhaust DC motor 42.

The exhaust DC motor 42 has an exhaust motor control circuit 420, which is a control circuit characteristic of a DC motor and controls the drive of the exhaust DC motor 42 and adjusts the load according to the control of the control unit 123. The exhaust motor control circuit 420 can adjust the motor power of the exhaust DC motor 42 by controlling control parameters such as the voltage output to the exhaust DC motor 42, the motor current value flowing through the exhaust DC motor 42, and the rotation speed of the exhaust DC motor 42. The control unit 123 can grasp the operating state of the exhaust DC motor 42 by acquiring these control parameters.

When the exhaust motor control circuit 420 receives an output instruction from the control unit 123, it operates the exhaust DC motor 42. Furthermore, when the load on the exhaust blower 4 fluctuates, such as a change in air duct pressure, the load on the exhaust DC motor 42 also changes, causing changes in the rotation speed, voltage value, and motor current value. The exhaust motor control circuit 420 includes an exhaust rotation speed detection unit 421, an exhaust voltage detection unit 422, an exhaust current detection unit 423, and an exhaust communication unit 424.

The exhaust rotation speed detection unit 421 detects the rotation speed of the exhaust DC motor 42. The exhaust voltage detection unit 422 detects the voltage supplied to the exhaust DC motor 42. The exhaust current detection unit 423 detects the motor current value, which is the current value of the motor current flowing through the exhaust DC motor 42. The exhaust communication unit 424 communicates with the control device 12. The exhaust rotation speed detection unit 421, exhaust voltage detection unit 422, and exhaust current detection unit 423 transmit the detection results to the control unit 123 via the exhaust communication unit 424.

The intake air filter 5 is an air filter that purifies the outside air by removing dust from the outside air sucked into the heat exchanger 2 to prevent a decrease in performance of the heat exchanger 2 due to clogging caused by dust contained in the outside air. The intake air filter 5 is removably installed in the upstream intake air duct 21a of the intake air duct 21. In other words, the intake air filter 5 is installed in a position upstream of the heat exchanger 2 in the intake air duct 21.

The outside air taken in by the heat exchange type ventilation device 1 passes through the intake air filter 5, and some of the suspended particles contained therein are removed. The intake air filter 5 can be replaced from a normal dust filter to a high-performance dust filter that can capture fine particulate matter and pollen at a higher capture rate than a normal dust filter.

The exhaust filter 6 is an air filter that removes dust from the return air sucked into the heat exchanger 2 to prevent a decrease in performance of the heat exchanger 2 due to clogging caused by dust contained in the return air. The exhaust filter 6 is removably installed in the upstream exhaust duct 22a of the exhaust duct 22. In other words, the exhaust filter 6 is installed in a position upstream of the heat exchanger 2 in the exhaust duct 22. The return air taken in by the heat exchange type ventilation device 1 passes through the exhaust filter 6, and some of the suspended particles contained therein are removed.

The outdoor temperature detection unit 11 is a detection unit that detects the outdoor temperature T, which is the temperature of the outdoor air drawn into the heat exchange type ventilation device 1 from the outdoors via the outdoor intake unit 9, i.e., the temperature of the outdoor air. In other words, the outdoor temperature detection unit 11 can be said to be an outdoor air temperature detection unit that detects the temperature of the outdoor air. The outdoor temperature detection unit 11 is provided in the upstream supply air duct 21a in the supply air duct 21. The outdoor temperature detection unit 11 transmits the detected outdoor air temperature to the control unit 123.

The display unit 13 notifies the user by displaying various warnings, such as a clogging warning that the heat exchanger 2 has become clogged due to icing, and a frost formation warning that there is a possibility of icing occurring in the heat exchanger 2. The display unit 13 can notify the user of various warnings, for example, by turning on a light-emitting diode. Details of each warning will be described later.

The control device 12 is provided inside the housing 1a and controls the entire heat exchange type ventilation device 1. The control device 12 includes a memory unit 121, a communication unit 122, and a control unit 123.

The memory unit 121 stores various information used to control the heat exchange type ventilation device 1.

The communication unit 122 communicates with the supply air blower 3, the exhaust air blower 4, and external equipment of the heat exchange type ventilation device 1.

The control unit 123 controls the entire heat exchange type ventilation device 1, including the intake air blower 3 and the exhaust air blower 4. The control unit 123 also functions as a determination unit that determines whether temporary clogging of the heat exchanger 2 due to icing has occurred, and whether clogging of the exhaust air filter 6 has occurred over time.

The control unit 123 controls the ventilation operation of the heat exchange type ventilation device 1 under predetermined conditions. The predetermined conditions are constant command voltage control that keeps the voltage supplied to the DC motor equipped in the blower constant, and ventilation operation at a predetermined ventilation volume, and the air volumes of the supply air blower 3 and the exhaust air blower 4 are set to the same predetermined air volume.

The control unit 123 determines whether or not there is a possibility of frost formation in the heat exchanger 2 based on the current outdoor temperature T. That is, the control unit 123 compares the current outdoor temperature T with the temperature threshold value. When the current outdoor temperature T is equal to or higher than the temperature threshold value, the control unit 123 determines that the current outdoor temperature and heat exchanger 2 are in a state in which frost formation is unlikely to occur in the heat exchanger 2. Furthermore, when the current outdoor temperature T is less than the temperature threshold value, the control unit 123 determines that the current outdoor temperature and heat exchanger 2 are in a state in which frost formation is likely to occur in the heat exchanger 2. That is, the control unit 123 determines whether or not there is a possibility of frost formation in the heat exchanger 2 based on the current outdoor temperature T.

When the current outdoor temperature T is less than the temperature threshold value, i.e., when there is a possibility of icing occurring in the heat exchanger 2 under the current outdoor temperature T, the control unit 123 stores the current motor current value I of the exhaust DC motor 42 as a pre-icing reference current value _Ii0 . The control unit 123 also calculates a current value by subtracting a predetermined set value A from the pre-icing reference current value _Ii0 , and stores this as an icing determination current value _Ii1 . The control unit 123 also calculates a current by subtracting a predetermined set value B from the pre-icing reference current value _Ii0 , and stores this as an icing improvement determination current value _Ii2 .

The pre-icing reference current value _Ii0 is a reference motor current value used by the control unit 123 to determine whether or not icing has occurred in the heat exchanger 2, i.e., whether or not the heat exchanger 2 has become clogged due to icing, based on the motor current value of the exhaust DC motor 42. The pre-icing reference current value _Ii0 may be referred to as a current value _Ii0 .

The freezing determination current value _Ii1 is a motor current value used by the control unit 123 to determine whether or not freezing has occurred in the heat exchanger 2, i.e., whether or not the heat exchanger 2 has become clogged due to freezing, based on the motor current value of the exhaust DC motor 42. The freezing determination current value _Ii1 is a value smaller than the pre-freezing reference current value _Ii0 . The freezing determination current value _Ii1 may also be referred to as the current value _Ii1 .

The icing improvement determination current value I _i2 is a motor current value used by the control unit 123 to determine, after it has been determined that icing has occurred in the heat exchanger 2, the state of recovery from the icing state of the heat exchanger 2 through icing condition improvement control, which will be described later, i.e., the state of improvement of the icing state, based on the motor current value of the exhaust DC motor 42. The icing improvement determination current value I _i2 is a value smaller than the pre-icing reference current value I _i0 and a value larger than the icing determination current value I _i1 . The icing improvement determination current value I _i2 may also be referred to as the current value I _i2 .

The set value A is a subtraction value used to calculate the ice formation determination current value _Ii1 based on the pre-icing reference current value _Ii0 . The set value A is determined in advance through experiments and simulations, and is stored in the control unit 123. The control unit 123 can also calculate the set value A by multiplying the pre-icing reference current value _Ii0 by a predetermined ratio. The predetermined ratio is determined in advance through experiments and simulations, and is stored in the control unit 123.

The set value B is a subtraction value used to calculate the icing amelioration determination current value _Ii2 based on the pre-icing reference current value _Ii0 . The set value B is determined in advance through experiments and simulations, and is stored in the control unit 123. The set value A and the set value B have a magnitude relationship of A>B.

After acquiring the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 , the control unit 123 monitors the current outdoor temperature T, and when the current motor current value I of the exhaust DC motor 42 becomes equal to or less than the icing determination current value _Ii1 , it determines that icing has occurred in the heat exchanger 2, i.e., that the heat exchanger 2 has become clogged due to icing.

When the current motor current value I of the exhaust DC motor 42 becomes equal to or less than the ice formation determination current value _Ii1 , the control unit 123 performs ice condition improvement control to reduce the air volume of the intake air blower 3 to be lower than the air volume of the exhaust air blower 4 for a predetermined operation change time, thereby reducing the amount of outside air, which is at a lower temperature than the indoor air, flowing into the heat exchanger 2. This allows the ice on the heat exchanger 2 to melt by the heat of the airflow of the indoor air that is transported to the heat exchanger 2 by the exhaust air blower 4 and exhausted from the room.

After the icing condition improvement control, the control unit 123 returns the state of the supply air blower 3 to the normal operating state, and determines the effect of the icing condition improvement control on the heat exchanger 2 based on the amount of change in the motor current value of the exhaust air blower 4. If the current motor current value I of the exhaust DC motor 42 is equal to or greater than the icing improvement determination current value _Ii2 , the control unit 123 determines that there is an effect of improving the icing condition of the heat exchanger 2, and that although there is a possibility of icing occurring, the icing condition has been improved. Thereafter, the control unit 123 returns to the operation of determining whether or not there is a possibility of icing occurring on the heat exchanger 2 based on the current outdoor temperature T.

When the current motor current value I of the exhaust DC motor 42 is less than the ice improvement judgment current value _Ii2 , the control unit 123 determines that the effect of improving the icing state of the heat exchanger 2 is insufficient. When the control unit 123 determines that the effect of improving the icing state of the heat exchanger 2 is insufficient, the control unit 123 repeats the ice improvement control to alleviate and improve the icing state of the heat exchanger 2 until the current motor current value I of the exhaust DC motor 42 becomes equal to or greater than the ice improvement judgment current value _Ii2 or until the current outdoor temperature T becomes greater than a predetermined temperature threshold value.

When the ice condition improvement control is repeated, the operation change time C may be extended, and the reduction amount by which the air volume of the supply air blower 3 is reduced below the air volume of the exhaust air blower 4 may be increased. This makes it possible to further reduce the amount of outside air, which is colder than the indoor air, flowing into the heat exchanger 2, thereby increasing the effect of improving the ice condition of the heat exchanger 2.

Here, if the control unit 123 determines that the current motor current value I of the exhaust DC motor 42 is less than the ice improvement judgment current value _Ii2 and that the effect of improving the ice condition of the heat exchanger 2 is insufficient, and if the ice condition improvement control can be repeatedly performed, it notifies the user of an ice occurrence warning to the effect that ice has occurred on the heat exchanger 2 but the ice condition can be improved.

On the other hand, when the control unit 123 repeats the ice condition improvement control a predetermined number of times, it notifies the user of an ice clogging warning that temporary clogging of the heat exchanger 2 has occurred due to ice.

When the current outdoor temperature T is less than the temperature threshold value, i.e., when there is a possibility of icing occurring in the heat exchanger 2 at the current outdoor temperature T, the control unit 123 stores the pre-icing reference current value I _i0 , the icing determination current value I _i1 , and the icing improvement determination current value I _i2 until a state in which there is no possibility of icing occurring in the heat exchanger 2 is reached, and resets this information when a state in which there is no possibility of icing occurring in the heat exchanger 2 is reached.

Figure 3 is a characteristic diagram showing the relationship between the air volume and static pressure of the blower when constant command voltage control is performed on the blower in embodiment 1. Figure 4 is a characteristic diagram showing the relationship between the motor current and rotation speed of the blower when constant command voltage control is performed on the blower in embodiment 1. As shown in Figure 4, the blower in embodiment 1 has a relationship in which the motor current required to drive the DC motor decreases as the rotation speed increases during constant command voltage control in which the voltage supplied to the DC motor provided in the blower is constant. The blowers in embodiment 1 are the intake blower 3 and the exhaust blower 4. The DC motors in embodiment 1 are the intake DC motor 32 and the exhaust DC motor 42.

The control unit 123 can obtain the motor current value, which is the current value of the motor current flowing through the supply DC motor 32 of the supply blower 3, from the supply current detection unit 323, and can obtain the motor current value, which is the current value of the motor current flowing through the exhaust DC motor 42 of the exhaust blower 4, from the exhaust current detection unit 423. The control unit 123 can also obtain the outdoor temperature T, i.e., the temperature of the outside air, from the outdoor temperature detection unit 11. The control unit 123 detects the occurrence of icing in the heat exchanger 2 and clogging due to icing in the heat exchanger 2 based on the outdoor temperature and the motor current value of the exhaust DC motor 42.

3, characteristic curve 111 represents the relationship between air volume and static pressure. Heat exchange type ventilation device 1 has the ventilation performance shown in characteristic curve 111. Initial pressure loss curve 112 represents the relationship between air volume and static pressure when there is no clogging due to icing in heat exchanger 2. In other words, the initial pressure loss is the pressure loss when there is no icing in heat exchanger 2. Clogging pressure loss curve 113 represents the relationship between air volume and static pressure when there is clogging due to icing in heat exchanger 2. In other words, the clogging pressure loss is the pressure loss when there is icing in heat exchanger 2. The air volume at intersection 114 between characteristic curve 111 and initial pressure loss curve 112 is the ventilation air volume by heat exchange type ventilation device 1 at the time of initial pressure loss. The motor current of each blower at this ventilation air volume corresponds to motor current 131 in FIG. 4.

When the outdoor air temperature drops during ventilation operation, the heat exchange ventilation device 1 causes condensation in the heat exchanger exhaust air duct 22c, which is the exhaust air duct 22 in the heat exchanger 2. That is, condensation occurs when the indoor air flowing through the exhaust air duct 22 drops in temperature below the dew point due to heat exchange with the outdoor air in the heat exchanger 2. When the exhaust air temperature after heat exchange falls below the freezing temperature, the moisture generated by the condensation freezes and turns into ice, causing clogging of the heat exchanger 2 and reducing the ventilation function. That is, when clogging of the heat exchanger 2 occurs due to freezing, the ice becomes air duct resistance, increasing the pressure loss and reducing the ventilation function.

When ice creates airway resistance and pressure loss increases, the control unit 123 performs control to reduce the current value of the exhaust DC motor 42 so as to increase the rotation speed of the exhaust DC motor 42 according to the relationship between the rotation speed of the exhaust DC motor 42 and the motor current value of the exhaust DC motor 42 in order to maintain a predetermined ventilation air volume in constant command voltage control that keeps the voltage supplied to the blower constant. The ice melts when the outdoor temperature rises or the heat quantity of the exhausted indoor air increases. In other words, clogging of the heat exchanger 2 due to ice is temporary.

When the heat exchanger 2 becomes clogged due to icing, the initial pressure loss curve 112 rises in the direction of the arrow in Figure 3. The clogging pressure loss curve 113 shows the relationship between the air volume and static pressure when the heat exchanger 2 becomes clogged due to icing and it becomes difficult for air to pass through the heat exchanger 2.

In this case, the air volume at intersection 115 between characteristic curve 111 and clogging pressure loss curve 113 is the ventilation air volume produced by heat exchange type ventilation device 1. The rotation speed of the blower at this ventilation air volume corresponds to motor current 132 in Figure 4. At intersection 115, the air volume is lower than at intersection 114, making it difficult to ventilate even if the blower is rotating. The motor current of the blower also decreases from the position of motor current 131 to the position of motor current 132.

And the clogging of the heat exchanger 2 due to icing reduces the ventilation function of the heat exchange type ventilation device 1. In other words, when the clogging of the heat exchanger 2 occurs due to icing, the clogging of the heat exchanger 2 due to icing creates airflow resistance, increasing the pressure loss, reducing the air volume of the blower and the ventilation air volume, and reducing the ventilation function.

Figure 5 is a first flowchart showing an example of an operation for detecting clogging due to icing on the heat exchanger 2 in the heat exchanger type ventilation device 1 according to the first embodiment and an operation for improving the icing state of the heat exchanger 2. Figure 6 is a second flowchart showing an example of an operation for detecting clogging due to icing on the heat exchanger 2 in the heat exchanger type ventilation device 1 according to the first embodiment and an operation for improving the icing state of the heat exchanger 2.

The control unit 123 acquires the motor current value of the supply DC motor 32 from the supply DC motor 32 mounted on the supply blower 3, acquires the motor current value of the exhaust DC motor 42 from the exhaust DC motor 42 mounted on the exhaust blower 4, and acquires the outdoor temperature, i.e., the airflow temperature of the outdoor air, from the outdoor temperature detection unit 11. The control unit 123 performs filter clogging and icing clogging detection based on the acquired motor current value of the supply DC motor 32, motor current value of the exhaust DC motor 42, and outdoor temperature. In the heat exchange type ventilation device 1, the supply DC motor 32 mounted on the supply blower 3 and the exhaust DC motor 42 mounted on the exhaust blower 4 are controlled by constant command voltage control.

Below, we will explain the operation of detecting clogging due to icing of the exhaust filter 6 in the heat exchange type ventilation device 1.

In step S110, after the heat exchange type ventilation device 1 starts operating, the current outdoor temperature T is monitored. Specifically, the control unit 123 acquires the current outdoor temperature T from the outdoor temperature detection unit 11. The control unit 123 acquires the current outdoor temperature T at a predetermined period and monitors the outdoor temperature T. Note that the outdoor temperature T may also be referred to as temperature T. The control unit 123 controls the operation of the supply air DC motor 32 and the exhaust air DC motor 42 in response to the detected current outdoor temperature T to perform ventilation operation.

In step S120, it is determined whether the current outdoor temperature T is equal to or higher than a first temperature threshold _T0 , which is a temperature threshold. Specifically, the control unit 123 compares the current outdoor temperature T acquired in step S110 with the first temperature threshold _T0 to determine whether or not there is a possibility of icing occurring in the heat exchanger 2 under the current outdoor temperature T condition.

The first temperature threshold _T0 is a reference threshold for the control unit 123 to determine whether or not there is a possibility of icing occurring in the heat exchanger 2, and is determined in advance and stored in the control unit 123. The first temperature threshold _T0 can be said to be a reference threshold for determining whether or not there is a possibility of icing occurring in the heat exchanger 2. The first temperature threshold _T0 can also be said to be a icing occurrence warning temperature, which is a temperature at which it is necessary to be wary of the possibility of icing occurring in the heat exchanger 2. The first temperature threshold _T0 is, for example, 1°C.

When the current outdoor temperature T is equal to or higher than the first temperature threshold _T0 , the control unit 123 determines that the current outdoor temperature T and the heat exchanger 2 are in a state where there is no possibility of frost forming in the heat exchanger 2. When the current outdoor temperature T is lower than the first temperature threshold _T0 , the control unit 123 determines that the current outdoor temperature T and the heat exchanger 2 are in a state where there is a possibility of frost forming in the heat exchanger 2.

If it is determined that the current outdoor temperature T is equal to or higher than the first temperature threshold value _T0 , i.e., if it is determined that there is no possibility of icing occurring in the heat exchanger 2, then the answer in step S120 is Yes, and the process returns to step S110. If it is determined that the current outdoor temperature T is lower than the first temperature threshold value _T0 , i.e., if it is determined that there is a possibility of icing occurring in the heat exchanger 2, then the answer in step S120 is No, and the process proceeds to step S130.

In step S130, it is determined whether the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing amelioration determination current value _Ii2 have been acquired. Specifically, the control unit 123 determines whether the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing amelioration determination current value _Ii2 have been acquired by determining whether the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing amelioration determination current value _Ii2 are stored in the control unit 123.

The control unit 123 determines that the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 have been acquired if the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 are stored in the control unit 123. The control unit 123 determines that the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 have not been acquired if the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 are not stored in the control unit 123.

If it is determined that the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 have not been obtained, the answer in step S130 is No and the process proceeds to step S140. If it is determined that the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing improvement determination current value _Ii2 have been obtained, the answer in step S130 is Yes and the process proceeds to step S150.

In step S140, the pre-icing reference current value _Ii0 , the icing determination current value _Ii1 , and the icing amelioration determination current value _Ii2 are acquired. Specifically, the control unit 123 acquires the current motor current value I of the exhaust DC motor 42 from the exhaust current detection unit 423 of the exhaust DC motor 42 mounted on the exhaust blower 4.

The control unit 123 stores the acquired current motor current value I of the exhaust DC motor 42 as the pre-icing reference current value _Ii0 . This allows the control unit 123 to acquire the pre-icing reference current value _Ii0 . In other words, the control unit 123 can grasp the motor current value I of the exhaust DC motor 42 in the normal state in the pressure loss state of the environment before clogging due to icing occurs in the heat exchanger 2.

In this way, when the current outdoor temperature T is less than the first temperature threshold value _T0 , i.e., when the current outdoor temperature T falls below the first temperature threshold value _T0 , the control unit 123 stores the current motor current value I of the exhaust DC motor 42 as the pre-icing reference current value _Ii0 .

The control unit 123 also calculates a current value by subtracting a predetermined set value A from the pre-icing reference current value I _i0 . The control unit 123 stores the current value calculated based on the set value A and the pre-icing reference current value I _i0 as the icing determination current value I _i1 . This allows the control unit 123 to obtain the icing determination current value I _i1 . The control unit 123 also calculates a current by subtracting a predetermined set value B from the pre-icing reference current value I _i0 . The control unit 123 stores the current value calculated based on the set value B and the pre-icing reference current value I _i0 as the icing improvement determination current value I _i2 . This allows the control unit 123 to obtain the icing improvement determination current value I _i2 . Thereafter, the process proceeds to step S150.

Since the heat exchange type ventilation device 1 can change the air volume from a small volume to a large volume using the same blower, the pre-freezing reference current value I _i0 may be relatively high or relatively low depending on the ventilation air volume, and is not a constant value. Therefore, the degree of influence of freezing changes when the pre-freezing reference current value I _i0 is relatively high and when the pre-freezing reference current value I _i0 is relatively low. When the set value A is a predetermined constant value, when the pre-freezing reference current value I _i0 is relatively high and when the pre-freezing reference current value I _i0 is relatively low, the control unit 123 may not be able to accurately determine whether or not freezing has occurred in the heat exchanger 2.

In contrast, by multiplying the pre-icing reference current value I _i0 by a predetermined ratio to calculate the set value A, it is possible to avoid erroneous detection that occurs when the set value A is set to a constant value as described above. That is, when the pre-icing reference current value I _i0 is relatively high, it is possible to set the set value A to a relatively large value suitable for determining whether or not icing has occurred in the heat exchanger 2 when the pre-icing reference current value I _i0 is relatively high. Also, when the pre-icing reference current value I _i0 is relatively low, it is possible to set the set value A to a relatively small value suitable for determining whether or not icing has occurred in the heat exchanger 2 when the pre-icing reference current value I _i0 is relatively low.

In step S150, it is determined whether the current outdoor temperature T is equal to or lower than _a second temperature threshold T1, which is a temperature threshold. Specifically, the control unit 123 compares the outdoor temperature T acquired in step S110 with the second temperature threshold _T1 to determine whether or not there is a possibility of icing occurring in the heat exchanger 2 in the state of the current outdoor temperature T.

The second temperature threshold _T1 is a threshold that serves as a reference for the control unit 123 to determine whether or not there is a possibility of icing occurring in the heat exchanger 2, and is determined in advance and stored in the control unit 123. The second temperature threshold _T1 can be said to be a threshold that serves as a reference for determining whether or not a state has been reached in which there is no possibility of icing occurring in the heat exchanger 2 when steps S160 to S240 described below are repeated. In other words, the second temperature threshold _T1 can be said to be a freezing safety temperature, which is a temperature at which it can be determined that the heat exchanger 2 will not freeze. The second temperature threshold _T1 is, for example, 3° C. By performing step S150, it is possible to determine whether or not there is a possibility of icing occurring in the heat exchanger 2.

When the current outdoor temperature T is equal to _or lower than the second temperature threshold T1, the control unit 123 determines that there is a possibility of frost formation in the heat exchanger 2. When the current outdoor temperature T is greater than the second temperature threshold _T1 , the control unit 123 determines that there is no possibility of frost formation in the heat exchanger 2.

In the flow of steps S120 → S130 → S140 → S150 and the flow of steps S120 → S130 → S150, in the flow of No in step S120, it is determined that there is a possibility of icing occurring in the heat exchanger 2. On the other hand, in the flow of steps S230 or S240 → S150, in order to determine whether to continue monitoring the motor current value I of the exhaust DC motor 42 of the exhaust blower 4 in step S190 described later, it is necessary to determine in step S150 whether there is a possibility of icing occurring in the heat exchanger 2.

If it is determined that the current outdoor temperature T is equal to or lower than the second temperature threshold _T1 , i.e., if it is determined that there is a possibility of icing occurring in the heat exchanger 2, then the answer in step S150 is Yes, and the process proceeds to step S160. If it is determined that the current outdoor temperature T is greater than the second temperature threshold _T1 , i.e., if it is determined that there is no possibility of icing occurring in the heat exchanger 2, then the answer in step S150 is No, and the process proceeds to step S250.

In step S160, the motor current value I of the exhaust DC motor 42 of the exhaust blower 4 is monitored. Specifically, the control unit 123 acquires the current motor current value I of the exhaust DC motor 42 from the exhaust current detection unit 423 of the exhaust motor control circuit 420 of the exhaust blower 4. The control unit 123 acquires the motor current value I of the exhaust DC motor 42 at a predetermined cycle and monitors the motor current value I of the exhaust DC motor 42.

In step S170, it is determined whether the current motor current value I of the exhaust DC motor 42 is equal to or less than the ice formation determination current value _Ii1 . Specifically, the control unit 123 compares the current motor current value I of the exhaust DC motor 42 acquired in step S160 with the ice formation determination current value _Ii1 stored in the control unit 123, and determines whether the current motor current value I of the exhaust DC motor 42 is equal to or less than the ice formation determination current value _Ii1 . In other words, the control unit 123 determines whether the current motor current value I of the exhaust DC motor 42 has decreased by the set value A or more from the pre-icing reference current value _Ii0 .

If the current motor current value I of the exhaust DC motor 42 is equal to or less than the ice formation determination current value _Ii1 , the control unit 123 determines that ice has formed in the heat exchanger 2. If the current motor current value I of the exhaust DC motor 42 is greater than the ice formation determination current value _Ii1 , the control unit 123 determines that ice has not formed in the heat exchanger 2.

4, the motor current value I of the exhaust DC motor 42 decreases due to an increase in pressure loss caused by the occurrence of icing in the heat exchanger 2. When the motor current value I of the exhaust DC motor 42 is equal to or less than the icing determination current value _Ii1 , the control unit 123 determines that icing has occurred in the heat exchanger 2.

If it is determined that the current motor current value I of the exhaust DC motor 42 is equal to or less than the ice formation determination current value _Ii1 , the result in step S170 becomes Yes, and the process proceeds to step S180. If it is determined that the current motor current value I of the exhaust DC motor 42 is greater than the ice formation determination current value _Ii1 , the result in step S170 becomes No, and the process returns to step S160.

Here, in the heat exchange type ventilation device 1, while the current motor current value I of the exhaust DC motor 42 is greater than the freezing determination current value _Ii1 , i.e., while No in step S170→step S160 is repeated, normal operation is performed in which the air volume of the supply DC motor 32 is the same as the air volume of the exhaust DC motor 42. That is, when it is determined in step S120 that the current outdoor temperature T is less than the first temperature threshold _T0 , which is a predetermined temperature threshold, the control unit ₁₂₃ controls the operation of the heat exchange type ventilation device 1 in normal operation in which the air volume of the supply DC motor 32 is the same as the air volume of the exhaust DC motor 42, while the current motor current value I of the exhaust DC motor 42 is greater than the freezing determination current value Ii1, i.e., while No in step S170→step S160 is repeated.

In step S180, the output of the intake air blower 3 is reduced or the intake air blower 3 is stopped for a predetermined operation change time C to melt the ice and improve the icy condition. Specifically, the control unit 123 controls to reduce the output of the intake air blower 3 only during the operation change time C, or controls to stop the intake air blower 3 only during the operation change time C. The reduction in the output of the intake air blower 3 is a reduction in the voltage supplied to the intake air blower 3, i.e., a reduction in the voltage supplied to the intake air DC motor 32. In the reduction in the output of the intake air blower 3, the output of the intake air blower 3 is reduced by the set value D. Therefore, the control unit 123 controls to reduce the output of the intake air blower 3 by the set value D only during the operation change time C, or controls to stop the intake air blower 3 only during the operation change time C to improve the icy condition. The control to reduce the output of the intake air blower 3 only during the operation change time C, or the control to stop the intake air blower 3 only during the operation change time C, is a control to reduce the air volume of the intake air blower 3 below the air volume of the exhaust air blower 4 only during the operation change time C.

The operation change time C is the time during which the control unit 123 performs control to change the operation of the intake air blower 3 in order to improve the ice formation of the heat exchanger 2. The operation change time C is predetermined by experiments and simulations and stored in the control unit 123. The operation change time C is, for example, 5 minutes. The predetermined operation change time C means the operation change time C set in the series of ice formation improvement controls. The control for melting the ice to improve the ice formation is the control performed in step S180. On the other hand, the control for melting the ice to improve the ice formation, including the process of extending or shortening the operation change time C as described later, can be considered as a series of ice formation improvement controls in a broad sense. In other words, the predetermined operation change time C includes the initial value of the operation change time C, the extended operation change time C, and the shortened operation change time C, which are predetermined and set before step S180 is performed.

The set value D is the amount by which the control unit 123 reduces the output of the supply air blower 3 in order to improve icing of the heat exchanger 2. The set value D is determined in advance through experiments and simulations and is stored in the control unit 123.

By reducing the output of the intake fan 3, the amount of outside air, which is at a lower temperature than the indoor air, flowing into the heat exchanger 2 is reduced, and the ice on the heat exchanger 2 can be melted by the heat of the airflow of the indoor air transported to the heat exchanger 2 by the exhaust fan 4 and exhausted from the room. This allows the heat exchange type ventilation device 1 to improve the icing condition of the heat exchanger 2. Also, by stopping the intake fan 3, the flow of outside air, which is at a lower temperature than the indoor air, into the heat exchanger 2 is stopped, and the ice on the heat exchanger 2 can be melted by the heat of the airflow of the indoor air transported to the heat exchanger 2 by the exhaust fan 4 and exhausted from the room. This allows the heat exchange type ventilation device 1 to improve the icing condition of the heat exchanger 2.

After the operation change time C has elapsed, in step S190, the state of the intake air blower 3 is returned to the normal state. Specifically, the control unit 123 returns the state of the intake air blower 3 whose output has been reduced or stopped in step S180 to the normal operating state before step S180.

In step S200, it is determined whether the current motor current value I of the exhaust DC motor 42 is equal to or greater than the ice formation improvement determination current value I _i2 . That is, it is determined whether the current motor current value I of the exhaust DC motor 42 has increased by equal to or greater than "A-B", which is the difference between the ice formation improvement determination current value I _i1 and the ice formation improvement determination current value I _i2 . Specifically, after the control unit 123 returns the intake air blower 3 to the normal operating state in step S190, it obtains the current motor current value I of the exhaust DC motor 42 from the exhaust current detection unit 423 of the exhaust motor control circuit 420 of the exhaust blower 4. Then, the control unit 123 compares the obtained current motor current value I of the exhaust DC motor 42 with the ice formation improvement determination current value I _i2 stored in the control unit 123, and determines whether the current motor current value I of the exhaust DC motor 42 is equal to or greater than the ice formation improvement determination current value I _i2 .

Here, when the current motor current value I of the exhaust DC motor 42 is equal to or greater than the icing improvement determination current value _Ii2 , the control unit 123 determines that there is an improvement effect on the icing state of the heat exchanger 2. When the current motor current value I of the exhaust DC motor 42 is less than the icing improvement determination current value _Ii2 , the control unit 123 determines that there is insufficient improvement effect on the icing state of the heat exchanger 2. Note that the icing improvement determination current value _Ii2 corresponds to the motor current 133 located between the motor currents 131 and 132 in FIG. 4.

If it is determined that the current motor current value I of the exhaust DC motor 42 is equal to or greater than the ice improvement determination current value _Ii2 , the answer in step S200 is Yes, and the process proceeds to step S260. In this case, the control unit 123 determines that there has been an effect of improving the ice condition of the heat exchanger 2, and that although there is a possibility of ice formation, the ice condition has been improved, and the process proceeds to step S260. If it is determined that the current motor current value I of the exhaust DC motor 42 is less than the ice improvement determination current value _Ii2 , the answer in step S200 is No, and the process proceeds to step S210.

In step S210, whether or not the icing condition in the heat exchanger 2 can be improved is determined based on whether or not the current operation change time C is equal to or less than the set value E. Specifically, the control unit 123 determines whether the current operation change time C is equal to or less than the set value E.

The set value E is a reference value for the control unit 123 to determine whether or not the icing condition in the heat exchanger 2 can be improved based on the current operation change time C, and is a time threshold value that is greater than the initial value of the operation change time C. The set value E is determined in advance through experiments and simulations and is stored in the control unit 123.

If the current operation change time C is equal to or less than the set value E, the control unit 123 determines that it is possible to improve the icing condition in the heat exchanger 2 by further performing icing condition improvement control. If the current operation change time C is greater than the set value E, the control unit 123 determines that clogging due to icing has occurred in the heat exchanger 2, and that it is impossible to improve the icing condition in the heat exchanger 2 even if icing condition improvement control is further performed.

If it is determined that the current operation change time C is equal to or less than the set value E, the answer is Yes in step S210 and the process proceeds to step S220. If it is determined that the current operation change time C is greater than the set value E, the answer is No in step S210 and the process proceeds to step S240.

In step S220, the operation change time C is extended. Specifically, the control unit 123 adds a predetermined set value F to the current operation change time C and stores it as the operation change time C to be used in the next ice condition improvement control. If the operation change time C used in the current ice condition improvement control is an already extended operation change time C, the control unit 123 further adds the set value F to the extended operation change time C and stores it as the operation change time C to be used in the next ice condition improvement control. By extending the operation change time C to be used in the next ice condition improvement control, the amount of outside air, which is lower in temperature than the indoor air, flowing into the heat exchanger 2 can be further reduced, thereby increasing the effect of improving the ice condition of the heat exchanger 2. The above-mentioned set value D may be increased. By increasing the set value D, the amount of outside air, which is lower in temperature than the indoor air, flowing into the heat exchanger 2 can be further reduced, thereby increasing the effect of improving the ice condition of the heat exchanger 2. Then, proceed to step S230.

In the flow proceeding from step S220 to step S230 to step S150, icing will occur repeatedly unless the temperature conditions are improved in step S150, i.e., unless there is a change in the current outdoor temperature T that becomes greater than the second temperature threshold T1, so a notification is issued that there is a possibility of icing occurring in the heat exchanger 2, and the flow from No in step S170 to step S160 is repeated to continuously check for the occurrence of icing. In addition, the flow from Yes in step S170 to step S180 is repeated to continuously perform icing condition improvement control.

The set value F is an extension time that is added to the current operation change time C to extend the operation change time C. The set value F is determined in advance through experiments and simulations and is stored in the control unit 123.

That is, the operation change time C is extended and set in accordance with the amount of decrease in the current motor current value I of the exhaust DC motor 42 after the lapse of the operation change time C. Then, after the operation change time C is extended and set, if the current outdoor temperature T is equal to or lower than the second temperature threshold value _T1 and the current motor current value I of the exhaust DC motor 42 is equal to or lower than the ice formation determination current value _Ii1 , control is repeatedly performed to reduce the air volume of the supply air blower 3 below the air volume of the exhaust air blower 4 by the extended operation change time C.

In step S230, a warning of frost formation is issued. Specifically, the control unit 123 performs control to display the frost formation warning on the display unit 13. The frost formation warning is a warning indicating that the current outdoor temperature T and the heat exchanger 2 are in a state in which frost formation may occur in the heat exchanger 2. That is, the frost formation warning is a warning indicating that, unless there is a change in the temperature condition in step S150, that is, unless there is a change in which the current outdoor temperature T becomes greater than the second temperature threshold _T1 , frost formation may occur in the heat exchanger 2, and therefore the frost formation improvement control may be repeatedly performed. The frost formation warning indicates that the level of the frost formation state of the frost formation state of the heat exchanger 2 is a mild frost formation state level at which the frost formation state improvement control can melt the frost formation state of the heat exchanger 2. By displaying the frost formation warning on the display unit 13, the user can recognize that the ventilation volume of the heat exchanger type ventilator 1 has decreased due to the formation of frost in the heat exchanger 2, but that the frost formation state of the heat exchanger 2 can be improved. Then, return to step S150.

In step S240, a warning of ice clogging is issued. Specifically, the control unit 123 controls the display unit 13 to display the ice clogging warning. By displaying the ice clogging warning on the display unit 13, the user can recognize that temporary clogging of the heat exchanger 2 due to ice has occurred. Then, the process returns to step S150.

The ice clogging warning is a warning that indicates that ice has formed in the heat exchanger 2, causing temporary clogging, and that the ice will not be cleared even if ice condition improvement control is performed. The ice clogging warning indicates that the level of ice formed in the heat exchanger 2 is at a severe level of ice condition, where the ice on the heat exchanger 2 cannot be melted by ice condition improvement control, and the ice condition will not be cleared even if ice condition improvement control is performed.

In step S250, the icing warning is cancelled. Specifically, the control unit 123 performs control to end the display of the icing warning on the display unit 13. In addition, the pre-icing reference current value I _i0 , the icing determination current value I _i1 , the icing amelioration determination current value I _i2 , and the extended operation change time C are cleared. Specifically, the control unit 123 deletes from the control unit 123 the pre-icing reference current value I _i0 , the icing determination current value I _i1 , the icing amelioration determination current value I _i2 , and the extended operation change time C that are stored therein. Then, the process returns to step S110.

In step S260, it is determined whether the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value _Ii0 . That is, it is determined whether the current motor current value I of the exhaust DC motor 42 is equal to or greater than the icing improvement determination current value _Ii2 and less than the pre-icing reference current value _Ii0 . Specifically, the control unit 123 compares the current motor current value I of the exhaust DC motor 42 acquired in step S200 with the pre-icing reference current value _Ii0 to determine whether the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value _Ii0 . By performing step S260, it is possible to determine whether the heat exchanger 2 has recovered from the icing state.

Here, if the current motor current value I of the exhaust DC motor 42 is equal to the pre-icing reference current value I _i0 , the control unit 123 determines that the icing of the heat exchanger 2 has been appropriately improved and the heat exchanger 2 has recovered from the icing state to the normal state. If the current motor current value I of the exhaust DC motor 42 is less than the pre-icing reference current value I _i0 , that is, if the motor current value I of the exhaust DC motor 42 does not return to the pre-icing reference current value I _i0 , the control unit 123 determines that the icing of the heat exchanger 2 has not been sufficiently improved and the heat exchanger ₂ has not recovered from the icing state. In other words, the icing recovery state of the heat exchanger 2 can be determined by determining whether the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value I i0.

If it is determined that the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value _Ii0 , the result in step S260 becomes Yes, and the process proceeds to step S270. If it is determined that the current motor current value I of the exhaust DC motor 42 has not returned to the pre-icing reference current value _Ii0 , the result in step S260 becomes No, and the process proceeds to step S210.

In step S270, it is determined that there is a possibility that the icing condition improvement control is being performed excessively, and the operation change time C is shortened. Specifically, the control unit 123 subtracts a predetermined set value G from the current operation change time C and stores the result as the operation change time C to be used for the next icing condition improvement control. If the operation change time C used for the current icing condition improvement control has already been extended or shortened, the control unit 123 further subtracts the set value G from the extended or shortened operation change time C and stores the result as the operation change time C to be used for the next icing condition improvement control. Then, proceed to step S230.

Figure 7 is a diagram illustrating an example of ice-formation state improvement control in the heat exchange type ventilation device 1 according to embodiment 1. In Figure 7, the state of the supply air DC motor 32, the motor current value I of the exhaust air DC motor 42, and the ice-formation state of the heat exchanger 2 are shown on the vertical axis. The state of the supply air DC motor 32 is an operating state or a stopped state. The ice-formation state of the heat exchanger 2 includes a normal state in which there is no ice, a frozen state, and a semi-frozen state which is a state between the normal state and the frozen state. The horizontal axis in Figure 7 indicates time.

As shown in Figure 7, during operation of the heat exchange ventilation device 1, at time T1, icing begins to occur in the heat exchanger 2. Then, the current motor current value I of the exhaust DC motor 42 starts to decrease from time T1.

At time T2, the icing state of heat exchanger 2 is in a semi-icing state, which is between the normal state and the icing state.

At time T3, the current motor current value I of the exhaust DC motor 42 drops to the ice formation determination current value _Ii1 . At this point, the heat exchanger 2 is in an iced state. At time T3, the intake air blower 3 is stopped, and ice formation improvement control is performed to melt the ice and improve the iced state. Time T3 corresponds to Yes in step S170 and step S180 in FIG. 5.

At time T4, the state of the supply air blower 3 is returned to the normal state. At this time, the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value I _i0 . Also, at this time, the heat exchanger 2 has returned to the normal state in which no ice has formed. Time T4 corresponds to Yes in steps S190 and S200 in FIG. 6.

At time T5, icing begins to occur in the heat exchanger 2. Then, the current motor current value I of the exhaust DC motor 42 starts decreasing from time T5.

At time T6, the current motor current value I of the exhaust DC motor 42 drops to the ice formation determination current value _Ii1 . At this point, the heat exchanger 2 is in an ice formation state. Then, at time T6, the intake air blower 3 is stopped, and ice formation improvement control is performed. Time T6 corresponds to Yes in step S170 and step S180 in FIG. 5.

At time T7, the state of the intake air blower 3 is returned to the normal state. The motor current value I7, which is the current motor current value I of the exhaust DC motor 42 at time T7, is equal to or greater than the ice improvement determination current value _Ii2 , but is less than the pre-icing reference current value _Ii0 and has not returned to the pre-icing reference current value _Ii0 . Furthermore, at this point in time, the heat exchanger 2 has not returned to a normal state in which there is no ice. Since the heat exchanger 2 has not returned to a normal state in which there is no ice, ice forms in the heat exchanger 2 in a short period of time, and ice formation in the heat exchanger 2 begins from the time T7.

Time T7 corresponds to Yes in steps S190 and S200 in Fig. 6. More specifically, time T7 corresponds to step S190 → Yes in step S200 → No in step S260 → Yes in step S210 → step S220 → step S230 → step S150 in Fig. 5 and Fig. 6. That is, the control unit 123 transitions to normal operation control. Also, the control unit 123 extends the operation change time C in step S220.

At time T8, the current motor current value I of the exhaust DC motor 42 drops to the ice formation determination current value _Ii1 . At this point, the heat exchanger 2 is in an ice formation state. Then, at time T8, the intake air blower 3 is stopped, and ice formation state improvement control is performed. Here, ice formation state improvement control is performed only during the extended operation change time C. Time T8 corresponds to Yes in step S170 and step S180 in FIG. 5.

At time T9, the state of the supply air blower 3 is returned to the normal state. At this time, the current motor current value I of the exhaust DC motor 42 has returned to the pre-icing reference current value I _i0 . Also, at this time, the heat exchanger 2 has returned to the normal state in which no ice has formed. Time T9 corresponds to Yes in steps S190 and S200 in FIG. 6.

As described above, when determining the motor current value I of the exhaust DC motor 42 in the heat exchange type ventilation device 1, the motor current value I of the exhaust DC motor 42 cannot be correctly determined unless both the supply air DC motor 32 and the exhaust air DC motor 42 are operating, because the environment is different from that during normal operation. For this reason, in the heat exchange type ventilation device 1, the motor current value I of the exhaust DC motor 42 is not determined while the supply air DC motor 32 is stopped. Furthermore, even if the actual motor current value I of the exhaust DC motor 42 becomes the pre-icing reference current value I _i0 while the supply air DC motor 32 is stopped in the icing state improvement control in step S180, the heat exchange type ventilation device 1 cannot immediately resume operation of the stopped supply air DC motor 32.

For this reason, after the operation change time C has elapsed and the state of the supply air blower 3 is returned to the normal state in step S190, the current motor current value I of the exhaust DC motor 42 is detected during operation of the supply air DC motor 32. Then, in the heat exchanger type ventilation device 1, even if the detected current motor current value I of the exhaust DC motor 42 exceeds the icing improvement determination current value _Ii2 , the icing on the heat exchanger 2 may not necessarily be completely removed, as in the state at time T7 described above.

Therefore, even if the current motor current value I of the exhaust DC motor 42 detected after the state of the supply air blower 3 is returned to the normal state in step S190 exceeds the icing improvement judgment current value _Ii2 , if the current motor current value I of the exhaust DC motor 42 is less than the pre-icing reference current value _Ii0 , the control unit 123 determines that the icing on the heat exchanger 2 has not been completely removed. Also, the control unit 123 determines that the icing on the heat exchanger 2 has not been sufficiently improved, and extends the operation change time C used in the icing condition improvement control in the next step S180.

Furthermore, if the current motor current value I of the exhaust DC motor 42 detected after the state of the supply air blower 3 is returned to the normal state in step S190 is equivalent to the pre-icing reference current value _Ii0 , the control unit 123 determines that icing in the heat exchanger 2 has been appropriately improved and that the heat exchanger 2 has recovered from the icy state to the normal state. Furthermore, the control unit 123 determines that there is a possibility that the icing condition improvement control is being performed excessively, and shortens the operation change time C used for the icing condition improvement control in the next step S180.

7, if the operation change time C is too long, the supply air blower 3 will be stopped more than necessary. Therefore, if the current motor current value I of the exhaust DC motor 42 detected after the state of the supply air blower 3 is returned to the normal state in step S190 is equivalent to the pre-icing reference current value _Ii0 , the control unit 123 shortens the operation change time C used for the next icing condition improvement control in step S180.

In the heat exchange type ventilation device 1, the control unit 123 repeatedly performs the above-mentioned control, thereby enabling the performance of ice-formation improvement control appropriate for improving the ice formation in the heat exchanger 2.

Each of the control unit 123, the air supply motor control circuit 320, and the exhaust motor control circuit 420 of the control device 12 is realized, for example, as a processing circuit having a hardware configuration shown in FIG. 8. FIG. 8 is a diagram showing an example of the hardware configuration of the processing circuit in embodiment 1. When each of the control unit 123, the air supply motor control circuit 320, and the exhaust motor control circuit 420 of the control device 12 is realized by the processor 201 executing a program stored in the memory 202. In addition, multiple processors and multiple memories may cooperate to realize the above functions. In addition, some of the functions of the control unit 123, the air supply motor control circuit 320, and the exhaust motor control circuit 420 of the control device 12 may be implemented as electronic circuits, and the other parts may be realized using the processor 201 and the memory 202.

The heat exchanger type ventilator 1 according to the above-described first embodiment performs a primary determination as to whether or not frost is likely to occur in the heat exchanger 2 at the current outdoor temperature T, depending on whether or not the current outdoor temperature T is equal to or higher than the first temperature threshold value _T0 . Furthermore, if it is determined in the primary determination that frost is likely to occur in the heat exchanger 2, the heat exchanger type ventilator 1 performs a secondary determination to determine whether or not frost has occurred in the heat exchanger 2, based on the motor current value I of the exhaust DC motor 42.

In this way, the heat exchanger type ventilation device 1 uses two judgment parameters to detect temporary clogging of the heat exchanger 2 due to icing in the heat exchanger type ventilation device 1, and can accurately judge temporary clogging of the heat exchanger 2 due to icing. This makes it possible for the heat exchanger type ventilation device 1 to eliminate erroneous detection of aging clogging of the exhaust filter 6 as temporary clogging of the heat exchanger 2 due to icing, and to suppress unnecessary restrictions on ventilation air volume caused by the execution of icing condition improvement control at times other than when the heat exchanger 2 is temporarily clogged due to icing.

Therefore, the heat exchange type ventilation device 1 can accurately determine temporary clogging of the heat exchanger 2 due to ice formation in the heat exchange type ventilation device 1 without using a pressure sensor or a flow sensor, and can suppress unnecessary restrictions on the ventilation air volume.

Furthermore, in the heat exchange type ventilation device 1, ice condition improvement control for melting the ice to improve the ice condition is carried out in response to the ice condition, thereby improving the ice condition in the heat exchanger 2. As a result, the heat exchange type ventilation device 1 can suppress unnecessary reductions in air volume when temporary clogging of the heat exchanger 2 occurs due to ice, and can suppress a reduction in the ventilation volume of the heat exchange type ventilation device 1. Furthermore, by changing the operation change time C in response to the ice condition, the heat exchange type ventilation device 1 can reduce unnecessary waiting time for ice to melt, and can suppress unnecessary reductions in ventilation air volume.

In addition, the heat exchanger type ventilation device 1 can set various reference values and set values used when determining whether temporary clogging of the heat exchanger 2 due to icing has occurred to any appropriate value corresponding to the installation environment of the heat exchanger type ventilation device 1. This allows the heat exchanger type ventilation device 1 to accurately determine temporary clogging of the heat exchanger 2 due to icing corresponding to the installation environment of the heat exchanger type ventilation device 1.

In this embodiment 1, a judgment is made using the motor current value I of the exhaust DC motor 42 to determine whether the heat exchange type ventilation device 1 is clogged. However, it is also possible to replace the motor current value I of the exhaust DC motor 42 with a judgment using the rotation speed N of the exhaust DC motor 42, which is a well-known technology, or the command voltage value of the exhaust DC motor 42.

As described above, the heat exchange type ventilation device 1 according to the first embodiment can accurately detect temporary clogging of the heat exchanger 2 due to icing, improve the icing condition of the heat exchanger 2, and suppress unnecessary restriction of ventilation air volume caused by the operation of improving the icing condition of the heat exchanger 2 other than when the heat exchanger 2 is temporarily clogged due to icing.

In addition, in the first embodiment, an example is shown in which a DC motor is used for the motor used in the intake air blower 3 and the exhaust air blower 4, but the motor used for the intake air blower 3 and the exhaust air blower 4 is not limited to a DC motor. In other words, an alternating current (AC) motor may be used for the intake air blower 3 and the exhaust air blower 4. When an AC motor is used for the intake air blower 3 and the exhaust air blower 4, the same control as above is performed, and the above-mentioned effect can be obtained.

Figure 9 is a block diagram showing the functional configuration of another heat exchange type ventilation device 1X according to embodiment 1. In Figure 9, the same components as those shown in Figure 2 are given the same reference numerals as in Figure 2, and detailed explanations are omitted. The other heat exchange type ventilation device 1X basically has the same configuration and effect as the heat exchange type ventilation device 1 according to embodiment 1, but differs from the heat exchange type ventilation device 1 according to embodiment 1 in that AC motors are used for the supply air blower 3 and the exhaust air blower 4.

The other heat exchange type ventilation device 1X comprises a housing 1a, a heat exchanger 2, an intake air blower 3X, an exhaust air blower 4X, an intake air filter 5, an exhaust air filter 6, an indoor outlet section 7, an indoor intake section 8, an outdoor intake section 9, an outdoor outlet section 10, an outdoor temperature detection section 11, a control device 12X, and a display section 13.

The intake air blower 3X is disposed in the downstream intake air duct 21b and generates an intake air flow from the outdoor intake section 9 toward the indoor outlet section 7. The intake air blower 3X includes an intake air fan 31 and an intake air AC motor 33 for rotating the intake air fan 31 within the intake air blower casing 30. The intake air blower 3X generates an intake air flow by rotating the intake air fan 31 with the intake air AC motor 33. The operation of the intake air blower 3X is controlled by the control section 123X, which will be described later, by controlling the operation, stop and rotation speed of the intake air AC motor 33.

The exhaust blower 4X is disposed in the downstream exhaust air duct 22b and generates an exhaust flow from the indoor suction section 8 toward the outdoor blower section 10. The exhaust blower 4X includes an exhaust fan 41 in an exhaust blower casing 40 and an exhaust AC motor 43 for rotating the exhaust fan 41. The exhaust blower 4X generates an exhaust flow by rotating the exhaust fan 41 with the exhaust AC motor 43. The operation of the exhaust blower 4X is controlled by the control section 123X, which will be described later, by controlling the operation, stop and rotation speed of the exhaust AC motor 43.

The control device 12X is provided inside the housing 1a and controls the entire heat exchange type ventilation device 1X. The control device 12X includes a memory unit 121, a control unit 123X, an air supply current detection unit 124, and an exhaust current detection unit 125.

The control unit 123X controls the entire heat exchange type ventilation device 1X, including the supply air blower 3X and the exhaust air blower 4X. The control unit 123X performs the same control as the control unit 123 of the heat exchange type ventilation device 1 according to the first embodiment, except that the control unit 123X uses the current value of the motor current flowing through the supply air AC motor 33 and the current value of the motor current flowing through the exhaust air AC motor 43 instead of the current value of the motor current flowing through the supply air DC motor 32 and the current value of the motor current flowing through the exhaust air DC motor 42.

The air supply current detection unit 124 can detect the current value of the motor current flowing through the air supply AC motor 33 using the measurement value of a current measuring instrument, such as a clamp meter clamped to an electric wire connecting a power source (not shown) and the air supply AC motor 33. Note that the method of detecting the current value of the motor current flowing through the air supply AC motor 33 is not limited to this.

The exhaust current detection unit 125 can detect the current value of the motor current flowing through the exhaust current detection unit 125 using the measurement value of a current measuring instrument, such as a clamp meter clamped to an electric wire connecting a power supply (not shown) and the exhaust current detection unit 125. Note that the method of detecting the current value of the motor current flowing through the exhaust current detection unit 125 is not limited to this.

By being configured as described above, the other heat exchange type ventilation device 1X can perform the same control as that shown in Figures 5 and 6 using the current value of the motor current flowing through the supply AC motor 33 and the current value of the motor current flowing through the exhaust AC motor 43, and can obtain the same effect as the heat exchange type ventilation device 1 according to the first embodiment. It is also possible to configure the supply current detection unit 124 to be provided in the supply air blower 3X and the exhaust current detection unit 125 to be provided in the exhaust air blower 4X. In this case, the supply air blower 3X and the exhaust air blower 4X are capable of communicating with the control device 12X.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

1 Heat exchange type ventilation device, 1a Housing, 1b Side, 1X Other heat exchange type ventilation device, 2 Heat exchanger, 3, 3X Supply air blower, 4, 4X Exhaust air blower, 5 Supply air filter, 6 Exhaust air filter, 7 Indoor air outlet, 8 Indoor air intake, 9 Outdoor air intake, 10 Outdoor air outlet, 11 Outdoor temperature detection unit, 12, 12X Control device, 13 Display unit, 21 Supply air duct, 21a Upstream supply air duct, 21b Downstream supply air duct, 21c Supply air duct in heat exchanger, 22 Exhaust air duct, 22a Upstream exhaust air duct, 22b Downstream exhaust air duct, 22c Exhaust air duct in heat exchanger, 23 Partition wall, 30 Supply air blower casing, 31 Supply air fan, 32 DC motor for air supply, 33 AC motor for air supply, 40 Exhaust blower casing, 41 Exhaust fan, 42 DC motor for air supply, 43 AC motor for air supply, 111 Characteristic curve, 112 Initial pressure loss curve, 113 Clogging pressure loss curve, 114, 115 Intersection, 121 Memory unit, 122 Communication unit, 123, 123X Control unit, 124 Current detection unit for air supply, 125 Current detection unit for exhaust, 131 Motor current, 132 Motor current, 320 Motor control circuit for air supply, 321 Rotational speed detection unit for air supply, 322 Voltage detection unit for air supply, 323 Current detection unit for air supply, 324 Communication unit for air supply, 420 Motor control circuit for exhaust, 421 Rotational speed detection unit for exhaust, 422 Voltage detection unit for exhaust, 423 Current detection unit for exhaust, 424 Exhaust communication unit, A, B, D, E, F, G set value, C operation change time, T outdoor temperature, _T0 first temperature threshold, _T1 second temperature threshold.

Claims (6)

a housing having an exhaust air duct for exhausting indoor air to the outside and an intake air duct for supplying outdoor air to the inside of the room formed independently therein;
an exhaust fan that includes an exhaust motor and is disposed in the exhaust air passage to generate an exhaust flow that flows through the exhaust air passage;
an intake air blower including an intake motor, disposed in the intake air passage, and configured to generate an intake air flow through the intake air passage;
a heat exchanger provided across the intake air passage and the exhaust air passage for exchanging heat between the intake air flow and the exhaust air flow;
an exhaust filter disposed upstream of the heat exchanger in the exhaust air duct;
an outdoor temperature detection unit that detects an outdoor temperature, which is the temperature of the outdoor air;
a current detection unit that detects a motor current value flowing through the exhaust motor;
a control unit for controlling operations of the intake air blower and the exhaust air blower;
Equipped with
The control unit is
When the outdoor temperature is less than a predetermined temperature threshold, a current motor current value of the exhaust motor is stored as a pre-freezing reference current value;
determining that icing has occurred in the heat exchanger when a current motor current value of the exhaust motor after storing the pre-icing reference current value is equal to or less than a icing determination current value which is smaller than the pre-icing reference current value;
performing a freezing state improvement control in which the air volume of the intake fan is reduced to be less than the air volume of the exhaust fan to melt the freezing;
A heat exchange type ventilation device characterized by the above. the control unit repeats the icing condition improvement control until a current motor current value of the exhaust motor becomes equal to or greater than a predetermined icing improvement determination current value that is smaller than the pre-icing reference current value and larger than the icing determination current value;
The heat exchange type ventilation device according to claim 1 . the control unit, when the outdoor temperature is lower than a predetermined temperature threshold, performs normal control to make the air volume of the supply air fan and the air volume of the exhaust air fan equal to each other while a current motor current value of the exhaust motor is greater than the freezing determination current value;
The heat exchange type ventilation device according to claim 1 or 2, the control unit performs control in the icing condition improvement control to reduce an air volume of the intake air blower for an operation change time set in the icing condition improvement control;
The heat exchange type ventilation device according to any one of claims 1 to 3, the control unit, in the icing condition improvement control, performs control to stop the supply air blower for an operation change time set in the icing condition improvement control;
The heat exchange type ventilation device according to any one of claims 1 to 3, The control unit calculates the ice formation determination current value by adding a value of a predetermined ratio to the pre-icing reference current value;
The heat exchange type ventilation device according to any one of claims 1 to 5,

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