Ventilation systems, heat exchange ventilation systems

Abstract

To provide a technique for suppressing an overcurrent to a compressor in a refrigeration cycle.SOLUTION: An air supply fan supplies air outside of a space to inside of the space as a supply air current. A dehumidification section dehumidifies the supply air current by using a refrigeration cycle for circulating a refrigerant in a compressor 14, a condenser, an expander and an evaporator in this order. A sensorless DC motor is a motor for driving the compressor 14 and has no sensing element for detecting a position of a rotor. An evaporator outlet temperature sensor 20 detects a downstream temperature that is a temperature downstream of the evaporator. An evaporator inlet temperature sensor 19 detects an upstream temperature that is a temperature upstream of the evaporator. A control section 21 prevents an overcurrent to the sensorless DC motor on the basis of a time after starting, the downstream temperature and the upstream temperature.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a ventilator and a heat exchange type ventilator. BACKGROUND ART

[0002] A refrigeration cycle mounted on an air conditioner is known, in which the refrigeration cycle circulates a refrigerant sequentially through a compressor, a condenser, an expander, and an evaporator (for example, Patent Document 1). PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] PATENT DOCUMENT 1 Japanese Unexamined Patent Publication No. 2022-101451 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] When the pressure in the compressor of the refrigeration cycle changes abruptly, the current to the DC motor of the compressor, which is driven without a sensor, increases sharply, so there is a risk that the compressor will stop due to overcurrent.

[0005] The present disclosure has been made to solve the above problem, and an object thereof is to provide a technique for suppressing overcurrent to a compressor in a refrigeration cycle. MEANS FOR SOLVING THE PROBLEMS

[0006] To solve the above problems, a ventilation system in one aspect of the present disclosure includes: an air supply fan that supplies outside air into the space as an air supply flow; a dehumidification unit that dehumidifies the air supply flow using a refrigeration cycle that circulates a refrigerant in the order of a compressor, condenser, expander, and evaporator; a motor that drives the compressor, which is a sensorless DC motor that does not have a sensing element for detecting the position of the rotor; a downstream temperature detection unit that detects the downstream temperature, which is the temperature downstream of the evaporator; an upstream temperature detection unit that detects the upstream temperature, which is the temperature upstream of the evaporator; and a control unit that prevents overcurrent to the sensorless DC motor based on the time since startup and the downstream and upstream temperatures. The control unit includes a calculation unit that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, a comparison unit that compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value, and a rotation speed control unit that, after a certain period of time has elapsed since startup, if the difference value as a result of the comparison by the comparison unit is greater than or equal to the threshold value, sets the rotation speed of the sensorless DC motor to a predetermined rotation speed or less.

[0007] Another aspect of the present disclosure is a heat exchange ventilation system. This system comprises a ventilation unit, an exhaust fan that exhausts air from within the space to the outside as an exhaust flow, and a heat exchange element that exchanges heat between the supply air flow and the exhaust air flow. The ventilation unit comprises an air supply fan that supplies air from outside the space to the space as an air supply flow, a dehumidification unit that dehumidifies the supply air flow using a refrigeration cycle that circulates a refrigerant in the order of a compressor, a condenser, an expander, and an evaporator, a sensorless DC motor that drives the compressor and does not have a sensing element for detecting the position of the rotor, a downstream temperature detection unit that detects the downstream temperature which is the temperature downstream of the evaporator, an upstream temperature detection unit that detects the upstream temperature which is the temperature upstream of the evaporator, and a control unit that prevents overcurrent to the sensorless DC motor based on the time since startup and the downstream and upstream temperatures. The control unit includes a calculation unit that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, a comparison unit that compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value, and a rotation speed control unit that, after a certain period of time has elapsed since startup, if the difference value as a result of the comparison by the comparison unit is greater than or equal to the threshold value, sets the rotation speed of the sensorless DC motor to a predetermined rotation speed or less.

[0008] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, recording media, computer programs, etc., are also valid forms of this disclosure. [Effects of the Invention]

[0009] According to this disclosure, it is possible to suppress overcurrent to the compressor in the refrigeration cycle. [Brief explanation of the drawing]

[0010] [Figure 1]This is a schematic diagram of a heat exchange ventilation system according to this embodiment. [Figure 2] This diagram shows the configuration of the control unit shown in Figure 1. [Figure 3] This figure shows another configuration of the control unit in Figure 1. [Figure 4] This figure shows yet another configuration of the control unit in Figure 1. [Figure 5] Figure 1 is a flowchart showing the control procedure of the control unit. [Modes for carrying out the invention]

[0011] The embodiments described below all represent preferred specific examples of the present disclosure. Therefore, the numerical values, shapes, materials, components, arrangement and connection configurations of components, as well as the steps (processes) and their order shown in the following embodiments are examples and are not intended to limit the present disclosure. Accordingly, among the components in the following embodiments, those components that are not described in the independent claims representing the highest-level concepts of the present disclosure will be described as optional components. In addition, substantially identical components are denoted by the same reference numerals in each figure, and redundant explanations are omitted or simplified.

[0012] Figure 1 is a schematic diagram of the heat exchange ventilation system 1. The heat exchange ventilation system 1 is a ventilation system with a dehumidifying function that provides supply and exhaust of air in indoor spaces, which can be installed in the ceiling space, side walls, or under the floor of a building. It is a ventilation system that has the function of exchanging heat during supply and exhaust.

[0013] The heat exchange ventilation system 1 ventilates by exchanging heat between the air exhausted from indoors to outdoors (exhaust flow 13, described later) and the air supplied from outdoors to indoors (supply flow 12, described later), while also dehumidifying the supply flow 12 as needed using its dehumidification function and introducing it into the indoors. In other words, the heat exchange ventilation system 1 performs ventilation and, during this ventilation, transfers heat from the supply flow 12 to the exhaust flow 13, suppressing the unnecessary inflow of heat. Furthermore, it dehumidifies the supply flow 12, suppressing the rise in indoor air humidity (indoor relative humidity).

[0014] Here, the exhaust flow 13 is the flow of air discharged from indoors to outdoors. The exhaust flow 13 is transported from indoors to the heat exchange ventilation device 1. The exhaust flow 13, which has exchanged heat with the supply air flow 12 by the heat exchange ventilation device 1, is discharged from the heat exchange ventilation device 1 to outdoors. The supply air flow 12 is the flow of air introduced from outdoors to indoors. The supply air flow 12 is transported from outdoors to the heat exchange ventilation device 1. The supply air flow 12, which has exchanged heat with the exhaust flow 13 by the heat exchange ventilation device 1, is dehumidified as needed by the dehumidification function and introduced into the indoors.

[0015] The heat exchange ventilation system 1 is a device that ventilates by exchanging heat between indoor air RA (exhaust flow 13) and outdoor air OA (supply air flow 12). Specifically, the heat exchange ventilation system 1 comprises a main body 2 as shown in Figure 1. The main body 2 has a roughly rectangular parallelepiped housing. An inner air inlet 5, an exhaust port 6, an outer air inlet 8, and a supply air inlet 9 are provided on the side of the main body 2. The inner air inlet 5 is an intake for taking in indoor air RA (exhaust flow 13) into the heat exchange ventilation system 1. The exhaust port 6 is an outlet for discharging the exhaust flow 13 as exhaust EA from the heat exchange ventilation system 1 to the outside. The outer air inlet 8 is an intake for taking in outdoor air OA (supply air flow 12) into the heat exchange ventilation system 1. The supply air inlet 9 is an outlet for discharging the supply air flow 12 as supply air SA from the heat exchange ventilation system 1 to the inside.

[0016] The main body 2 is equipped with a heat exchange element 3. The heat exchange element 3 is a component for exchanging heat between the exhaust flow 13 and the supply air flow 12. The heat exchange can be either sensible heat exchange, which is the exchange of temperature between the exhaust flow 13 and the supply air flow 12, or total heat exchange, which is the exchange of both sensible heat and latent heat, which is the exchange of humidity between the exhaust flow 13 and the supply air flow 12.

[0017] The heat exchange element 3 is a total heat exchange element formed of heat transfer paper (heat transfer plate) based on cellulose fibers. However, the material is not limited thereto. As the heat transfer plate constituting the heat exchange element 3, for example, a moisture-permeable resin film based on polyurethane or polyethylene terephthalate, or a paper material based on cellulose fibers, ceramic fibers, glass fibers, or the like can be used. Further, the heat transfer plate constituting the heat exchange element 3 may be a thin sheet with heat conductivity and having a property that gas does not permeate therethrough. In this case, the heat exchange element 3 serves as a sensible heat exchange element.

[0018] Inside the main body 2, an exhaust fan 4 and a supply air fan 7 are provided. The exhaust fan 4 is a blower for taking in an exhaust air flow 13 from an indoor air port 5 and discharging it from an exhaust port 6. The supply air fan 7 is a blower for taking in a supply air flow 12 from an outdoor air port 8 and discharging it from a supply air port 9. That is, the exhaust fan 4 exhausts the air in the space to the outside of the space as the exhaust air flow 13, and the supply air fan 7 supplies the air outside the space into the space as the supply air flow 12.

[0019] Inside the main body 2, an exhaust air duct 10 that communicates the indoor air port 5 and the exhaust port 6, and a supply air duct 11 that communicates the outdoor air port 8 and the supply air port 9 are formed. The exhaust air flow 13 sucked by the exhaust fan 4 passes through the heat exchange element 3, the exhaust fan 4, and the condenser 15 in the exhaust air duct 10, and is discharged outdoors from the exhaust port 6. In addition, the supply air flow 12 sucked by the supply air fan 7 passes through the heat exchange element 3, the supply air fan 7, and the evaporator 17 in the supply air duct 11, and is supplied indoors from the supply air port 9. When performing heat exchange ventilation, the heat exchange type ventilation device 1 operates the exhaust fan 4 and the supply air fan 7, and performs heat exchange in the heat exchange element 3 between the exhaust air flow 13 flowing through the exhaust air duct 10 and the supply air flow 12 flowing through the supply air duct 11.

[0020] Thereby, the heat exchange type ventilator 1 transfers the heat of the supply airflow 12 taken indoors to the exhaust airflow 13 discharged outdoors during ventilation, and suppresses the inflow of unnecessary heat. As a result, in the summer in Japan, it is possible to suppress an increase in indoor temperature caused by high-temperature outdoor air during ventilation. In addition, the heat exchange type ventilator 1 transfers the heat of the exhaust airflow 13 discharged outdoors to the supply airflow 12 taken indoors during ventilation, suppresses unnecessary heat discharge, and recovers heat indoors. As a result, in the winter in Japan, it is possible to suppress a decrease in indoor temperature caused by low-temperature outdoor air during ventilation.

[0021] Inside the main body 2, a compressor 14, a condenser 15, an expander 16, and an evaporator 17 are provided. The compressor 14, the condenser 15, the expander 16, and the evaporator 17 constitute a refrigeration cycle for circulating a refrigerant, which is annularly connected in this order by a refrigerant pipe 18, and the evaporator 17 serves as a dehumidifying unit and has a dehumidifying function for dehumidifying the supply airflow 12.

[0022] The compressor 14 is a device that compresses the low-temperature low-pressure refrigerant in the refrigerant pipe 18 and raises its temperature by increasing the pressure. The refrigerant refers to a heat medium used for transferring heat in the refrigeration cycle. A sensorless DC motor (not shown) is provided inside the compressor 14. The sensorless DC motor is a motor mounted to rotate a compression mechanism that compresses the refrigerant inside the compressor 14. That is, by starting and rotating the sensorless DC motor, the compressor 14 is started, and the operation of the compressor 14 is initiated. Here, the sensorless DC motor does not have a sensing element for detecting the position of the rotor, for example, a Hall element.

[0023] The condenser 15 is located downstream of the heat exchange element 3 on the exhaust air passage 10. The condenser 15 releases heat from the refrigerant, which has been heated to a high temperature and pressure by the compressor 14, into the air (exhaust flow 13). In this process, the refrigerant condenses and liquefies under high pressure. In other words, because the temperature of the refrigerant introduced into the condenser 15 is higher than the temperature of the air (exhaust flow 13), the air (exhaust flow 13) is heated and the refrigerant is cooled. That is, the heat exchange ventilation system 1 is equipped with a condenser cooling structure that cools the condenser 15 with the exhaust flow 13.

[0024] Furthermore, since the condenser 15 is located downstream of the heat exchange element 3 on the exhaust air passage 10, the condenser 15 can be cooled without degrading the heat exchange efficiency between the exhaust flow 13 and the supply air flow 12 by the heat exchange element 3. This will be explained in detail below.

[0025] The dehumidification function of the heat exchange ventilation system 1 is intended for use during Japanese summers when the outdoor air is hot and humid. During Japanese summers, the supply airflow 12 flowing into the heat exchange element 3 is hot. However, it is desirable that the supply airflow 12 after heat exchange with the exhaust airflow 13 by the heat exchange element 3 be at a lower temperature. This is because a lower temperature supply airflow 12 flowing into the building after heat exchange improves user comfort. And for the supply airflow 12 after heat exchange with the exhaust airflow 13 by the heat exchange element 3 to be at a lower temperature, it is desirable that the exhaust airflow 13 flowing into the heat exchange element 3 be at a lower temperature. If the condenser 15 is installed upstream of the heat exchange element 3 on the exhaust air passage 10, the exhaust airflow 13 will be heated by the condenser 15, and the heated exhaust airflow 13 will flow into the heat exchange element 3. However, since the condenser 15 is located downstream of the heat exchange element 3 on the exhaust air passage 10, the exhaust flow 13 flows into the heat exchange element 3 before being heated by the condenser 15. In other words, the heat exchange efficiency between the exhaust flow 13 and the supply air flow 12 by the heat exchange element 3 is not worsened.

[0026] The expander 16 is a device that reduces the pressure of the high-pressure refrigerant liquefied by the condenser 15 to a low-temperature, low-pressure liquid.

[0027] The evaporator 17 is located in the air supply passage 11. The evaporator 17 absorbs heat from the air (air supply flow 12) using the refrigerant, which has been reduced to a low temperature and low pressure by the expander 16. At that time, the refrigerant evaporates and vaporizes under low pressure. In other words, because the temperature of the refrigerant introduced into the evaporator 17 is lower than the temperature of the air (air supply flow 12), the air (air supply flow 12) is cooled and the refrigerant is heated. That is, the heat exchange ventilation system 1 is equipped with an evaporator heating structure that heats the evaporator 17 with the air supply flow 12. Both the condenser cooling structure and the evaporator heating structure can be considered temperature control structures.

[0028] The main unit 2 contains an evaporator inlet temperature sensor 19, an evaporator outlet temperature sensor 20, and a control unit 21.

[0029] The evaporator inlet temperature sensor 19 is an upstream temperature detection unit that detects the upstream temperature, which is the temperature upstream of the evaporator 17 in the refrigeration cycle of the compressor 14. The evaporator inlet temperature sensor 19 is installed on the refrigerant piping 18. The evaporator inlet temperature sensor 19 is a sensor that measures the temperature on the suction side of the evaporator 17, and mainly thermistors or platinum resistors are used.

[0030] The evaporator outlet temperature sensor 20 is a downstream temperature detection unit that detects the downstream temperature, which is the temperature downstream of the evaporator 17 in the refrigeration cycle of the compressor 14. The evaporator outlet temperature sensor 20 is installed on the refrigerant piping 18. The evaporator outlet temperature sensor 20 is a sensor that measures the temperature on the discharge side of the evaporator 17, and mainly thermistors or platinum resistors are used.

[0031] The control unit 21 controls the start timing of the compressor 14. In other words, the control unit 21 also controls the start timing of the sensorless DC motor installed inside the compressor 14.

[0032] In addition to the heat exchange ventilation described above, the heat exchange ventilation system 1 can also dehumidify the supply airflow 12 using the evaporator 17 as a dehumidifying unit. Here, we will explain the process of dehumidifying the supply airflow 12 using the evaporator 17.

[0033] First, the control unit 21 starts the compressor 14 to compress the refrigerant. The compressed refrigerant becomes high temperature and high pressure and is led to the condenser 15. In the condenser 15, the refrigerant becomes a high-pressure liquid by transferring heat to the exhaust flow 13. Next, the expander 16 reduces the pressure of the refrigerant that has liquefied in the condenser 15. When the compressor 14 is started, the opening of the expander 16 is set to be larger than the normal opening adjustment range in order to circulate the refrigerant.

[0034] Once the rotational speed of the sensorless DC motor of the compressor 14 stabilizes at the desired rotational speed, the opening of the expander 16 is reduced. Rapidly reducing the opening of the expander 16 would lead to a rapid change in the refrigerant pressure, potentially causing unstable operation of the compressor 14 or even an abnormal shutdown. Therefore, the opening of the expander 16 is adjusted with a period of several tens of seconds. The refrigerant, which has been depressurized in the expander 16 and become a low-temperature, low-pressure liquid that is easily evaporated, is led to the evaporator 17. In the evaporator 17, the supply airflow 12 loses heat due to the low-temperature, low-pressure refrigerant as it passes through the evaporator 17. At the same time, moisture in the supply airflow 12 condenses, reducing the amount of moisture in the supply airflow 12, and the supply airflow 12 becomes low-humidity air. In other words, the supply airflow 12 is dehumidified by the evaporator 17, which is the dehumidification section. The heat exchange ventilation system 1 does not operate the refrigeration cycle by stopping the compressor 14 and expander 16 when dehumidification is not required.

[0035] To ensure sufficient condensation in the supply airflow 12 when the evaporator 17 dehumidifies it, the operating frequency of the compressor 14 or the opening of the expander 16 is controlled so that the temperature difference obtained by subtracting the temperature of the evaporator inlet temperature sensor 19 from the temperature of the evaporator outlet temperature sensor 20 is 6-8°C. This temperature difference is also called SH (superheat). The evaporator 17 absorbs heat and evaporates, lowering the ambient temperature. Also, before the refrigerant returns from the evaporator 17 to the compressor 14, it is necessary to completely turn it into a gas before sending it to the compressor 14, so the temperature of the refrigerant vapor should be slightly increased after passing through the evaporator 17. By controlling SH within an appropriate range, the amount of dehumidification is ensured while preventing liquid return to the compressor 14.

[0036] When the system is operating stably under a heavy dehumidification load, for example, if the temperature of the supply airflow 12 decreases, the dehumidification load will decrease. When the dehumidification load decreases, the amount of dehumidification in the evaporator 17 decreases, which changes the distribution of liquid and gas phases in the evaporator 17, and the pressure required by the compressor 14 increases rapidly. When the pressure required by the compressor 14 increases rapidly, the motor current of the sensorless-driven compressor 14 increases rapidly, which may lead to overcurrent detection of the compressor 14 and cause it to stop.

[0037] In this embodiment, a sudden change in the dehumidification load is detected by the change in SH, and if SH changes rapidly (from positive to negative), the occurrence of overcurrent detection stop is anticipated, and the absolute value of the current of the compressor 14 is reduced. This suppresses overcurrent detection. This process will be explained in detail below.

[0038] Figure 2 shows the configuration of the control unit 21. The control unit 21 includes a calculation unit 50, a comparison unit 52, a storage unit 54, and a rotation speed control unit 60. The calculation unit 50 receives the upstream temperature from the evaporator inlet temperature sensor 19 and the downstream temperature from the evaporator outlet temperature sensor 20. The calculation unit 50 calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals by subtracting the upstream temperature from the downstream temperature. The calculation unit 50 outputs the calculated temperature difference to the comparison unit 52.

[0039] The comparison unit 52 calculates a difference value, which is the difference between the past temperature difference and the current temperature difference, by subtracting the current temperature difference calculated by the calculation unit 50 from the past temperature difference calculated by the calculation unit 50. For example, the time between when the past temperature difference was calculated and when the current temperature difference was calculated is assumed to be within 10 minutes. The comparison unit 52 compares the calculated difference value with a threshold value stored in the storage unit 54.

[0040] The rotational speed control unit 60 acquires the time elapsed since the compressor 14 was started. After a certain period of time has elapsed since the compressor was started, the rotational speed control unit 60, based on the comparison result by the comparison unit 52, determines if the difference value is greater than or equal to a threshold value, and sets the rotational speed of the sensorless DC motor of the compressor 14 to a predetermined rotational speed or less. A rotational speed below the predetermined speed is a rotational speed at which overcurrent to the sensorless DC motor can be suppressed. As a result, the rotational speed of the compressor 14 is reduced, and the operating current of the compressor 14 decreases. The threshold value for achieving this process is derived in advance through experimentation or simulation. The control unit 21 prevents overcurrent to the sensorless DC motor based on the time elapsed since the compressor 14 was started, the downstream temperature, and the upstream temperature.

[0041] Figure 3 shows another configuration of the control unit 21. The control unit 21 includes a calculation unit 50, a comparison unit 52, a storage unit 54, and an opening degree control unit 62. The calculation unit 50, comparison unit 52, and storage unit 54 are the same as in Figure 2. After a certain period of time has elapsed since startup, the opening degree control unit 62, based on the comparison result by the comparison unit 52, sets the opening degree of the expander 16 to a predetermined opening degree or higher if the difference value is greater than or equal to a threshold. For example, the opening degree of the expander 16 is set to the maximum. By easing the pressure reduction of the refrigerant in the evaporator 17 and reducing the amount of evaporation of the supply air flow 12 in the evaporator 17, the dehumidification load is reduced, and the operating current of the compressor 14 decreases as the dehumidification load is reduced. An opening degree above the predetermined opening degree is an opening degree that can suppress overcurrent to the sensorless DC motor.

[0042] Figure 4 shows yet another configuration of the control unit 21. The control unit 21 includes a calculation unit 50, a comparison unit 52, a storage unit 54, and an air supply volume control unit 64. The calculation unit 50, comparison unit 52, and storage unit 54 are the same as in Figure 2. After a certain period of time has elapsed since startup, the air supply volume control unit 64, based on the comparison result by the comparison unit 52, sets the air supply volume of the air supply fan 7 to a predetermined air supply volume or less if the difference value is greater than or equal to a threshold. This reduces the airflow of the air supply flow 12. By reducing the airflow of the air supply flow 12, the amount of evaporation of the air supply flow 12 in the evaporator 17 is reduced, thereby reducing the dehumidification load, and the operating current of the compressor 14 decreases as the dehumidification load is reduced. An air supply volume below the predetermined air supply volume is an air supply volume that can suppress overcurrent to the sensorless DC motor.

[0043] The subject of the apparatus, system, or method in this disclosure comprises a computer. The functions of the subject of the apparatus, system, or method in this disclosure are realized by the computer executing a program. The computer comprises a processor as its main hardware component, which operates according to the program. The processor is of any type as long as it can realize its functions by executing the program. The processor consists of one or more electronic circuits, including semiconductor integrated circuits (ICs) or LSIs (Large Scale Integrations). Multiple electronic circuits may be integrated on one chip or provided on multiple chips. Multiple chips may be aggregated in one device or provided on multiple devices. The program is recorded on a non-temporary recording medium such as a ROM, optical disc, or hard disk drive that is readable by the computer. The program may be pre-stored on the recording medium or supplied to the recording medium via a wide-area communication network, including the Internet.

[0044] The operation of the heat exchange ventilation system 1 with the above configuration will now be explained. Figure 5 is a flowchart of the control procedure of the control unit 21. When a certain period of time has elapsed since the compressor 14 was started (Y in S10), the calculation unit 50 obtains the downstream temperature and the upstream temperature (S12). The calculation unit 50 calculates the temperature difference (S14). The comparison unit 52 calculates the difference value (S16). If the difference value is greater than or equal to the threshold value (Y in S18), the rotation speed control unit 60, the opening degree control unit 62, or the supply air volume control unit 64 executes control to prevent overcurrent (S20). If the difference value is not greater than or equal to the threshold value (N in S18), step 20 is skipped. If a certain period of time has not elapsed since the compressor 14 was started (N in S10), steps 12 to 20 are skipped.

[0045] According to this embodiment, overcurrent to the sensorless DC motor is prevented based on the time elapsed since the compressor 14 started, the downstream temperature of the evaporator 17, and the upstream temperature of the evaporator 17, thereby suppressing overcurrent to the compressor 14 in the refrigeration cycle. Since overcurrent to the compressor 14 is suppressed, it becomes less likely to stop the compressor 14. In addition, since control is performed after a certain period of time has elapsed since the compressor 14 started, cases where the operation at startup is unstable can be excluded. Furthermore, if the difference value becomes large, the rotation speed of the sensorless DC motor of the compressor 14 is reduced to a predetermined rotation speed or less, thereby reducing the operating current of the compressor 14 by reducing the rotation speed of the compressor 14. Furthermore, if the difference value becomes large, the opening degree of the expander 16 is set to a predetermined opening degree or more, thereby easing the pressure reduction of the refrigerant in the evaporator 17 and reducing the dehumidification load, thereby reducing the operating current of the compressor 14. Furthermore, if the difference value becomes large, the supply airflow of the supply air fan 7 will be reduced to below a predetermined supply airflow, thereby reducing the amount of evaporation of the supply airflow 12 in the evaporator 17 and reducing the dehumidification load, which in turn reduces the operating current of the compressor 14.

[0046] An outline of one aspect of the present disclosure is as follows: A ventilation system in one aspect of the present disclosure includes an air supply fan (7) that supplies outside air into the space as an air supply flow (12), a dehumidification unit (17) that dehumidifies the air supply flow (12) using a refrigeration cycle that circulates a refrigerant in the order of a compressor (14), a condenser (15), an expander (16), and an evaporator (17), a sensorless DC motor that drives the compressor (14) and does not have a sensing element for detecting the position of the rotor, a downstream temperature detection unit (20) that detects the downstream temperature which is the temperature downstream of the evaporator (17), an upstream temperature detection unit (19) that detects the upstream temperature which is the temperature upstream of the evaporator (17), and a control unit (21) that prevents overcurrent to the sensorless DC motor based on the time since startup and the downstream and upstream temperatures.

[0047] The control unit (21) may include a calculation unit (50) that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, a comparison unit (52) that compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit (50) and the current temperature difference calculated by the calculation unit (50), with a threshold value, and a rotation speed control unit (60) that, after a certain period of time has elapsed since startup, if the difference value as a result of the comparison by the comparison unit (52) is greater than or equal to a threshold value, sets the rotation speed of the sensorless DC motor to a predetermined rotation speed or less.

[0048] The control unit (21) may include a calculation unit (50) that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, a comparison unit (52) that compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit (50) and the current temperature difference calculated by the calculation unit (50), with a threshold value, and an opening degree control unit (62) that, after a certain period of time has elapsed since startup, if the difference value as a result of the comparison by the comparison unit (52) is greater than or equal to the threshold value, sets the opening degree of the expander (16) to a predetermined opening degree or greater.

[0049] The control unit (21) may include a calculation unit (50) that calculates the temperature difference between the upstream temperature and the downstream temperature at predetermined intervals. The control unit (21) may also include a comparison unit (52) that compares a difference value, which is the difference between past temperature differences calculated by the calculation unit (50) and the current temperature difference calculated by the calculation unit (50), with a threshold value, and an air supply airflow control unit (64) that, after a certain period of time has elapsed since startup, sets the air supply airflow of the air supply fan (7) to a predetermined air supply airflow rate or less if the difference value is greater than or equal to the threshold value as a result of the comparison by the comparison unit (52).

[0050] The time between when the past temperature difference is calculated and when the current temperature difference is calculated may be less than 10 minutes.

[0051] Another aspect of the present disclosure is a heat exchange ventilation system (1). This system comprises a ventilation unit, an exhaust fan (4) that exhausts the air in the space to the outside as an exhaust flow, and a heat exchange element (3) that exchanges heat between the supply air flow (12) and the exhaust flow. The ventilation unit includes an air supply fan (7) that supplies air from outside the space into the space as an air supply flow (12), a dehumidification unit (17) that dehumidifies the air supply flow (12) by utilizing a refrigeration cycle that circulates a refrigerant in the order of a compressor (14), a condenser (15), an expander (16), and an evaporator (17), a sensorless DC motor that drives the compressor (14) and does not have a sensing element for detecting the position of the rotor, a downstream temperature detection unit (20) that detects the downstream temperature which is the temperature downstream of the evaporator (17), an upstream temperature detection unit (19) that detects the upstream temperature which is the temperature upstream of the evaporator (17), and a control unit (21) that prevents overcurrent to the sensorless DC motor based on the time since startup and the downstream and upstream temperatures.

[0052] The present disclosure has been described above based on examples. These examples are illustrative, and it will be understood by those skilled in the art that various modifications are possible for each component or combination of processing steps, and that such modifications are also within the scope of the present disclosure. [Explanation of symbols]

[0053] 1 Heat exchange ventilation system, 2 Main unit, 3 Heat exchange element, 4 Exhaust fan, 5 Inner air inlet, 6 Exhaust port, 7 Supply air fan, 8 Outside air inlet, 9 Supply air inlet, 10 Exhaust air passage, 11 Supply air passage, 12 Supply air flow, 13 Exhaust air flow, 14 Compressor, 15 Condenser, 16 Expander, 17 Evaporator (dehumidifying section), 18 Refrigerant piping, 19 Evaporator inlet temperature sensor, 20 Evaporator outlet temperature sensor, 21 Control unit, 50 Calculation unit, 52 Comparison unit, 54 Memory unit, 60 Rotation speed control unit, 62 Opening degree control unit, 64 Supply air volume control unit.

Claims

1. An air intake fan that supplies air from outside the space into the space as an air intake flow, A refrigeration cycle is used in which the refrigerant is circulated in the order of compressor, condenser, expander, and evaporator, and a dehumidification unit is used to dehumidify the supply airflow, A motor for driving the compressor, which is a sensorless DC motor that does not have a sensing element for detecting the position of the rotor, A downstream temperature detection unit detects the downstream temperature, which is the temperature downstream of the evaporator. An upstream temperature detection unit detects the upstream temperature, which is the temperature upstream of the evaporator, A control unit that prevents overcurrent to the sensorless DC motor based on the time since startup, the downstream temperature, and the upstream temperature, Equipped with, The control unit, A calculation unit that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, A comparison unit compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value. A ventilation device comprising: a rotation speed control unit that, after a certain period of time has elapsed since the start-up, if the difference value obtained from the comparison by the comparison unit is greater than or equal to the threshold value, reduces the rotation speed of the sensorless DC motor to a predetermined rotation speed or less.

2. An air supply fan that supplies air from outside the space into the space as an air supply flow, A refrigeration cycle is used in which the refrigerant is circulated in the order of compressor, condenser, expander, and evaporator, and a dehumidification unit is used to dehumidify the supply airflow, A motor for driving the compressor, which is a sensorless DC motor that does not have a sensing element for detecting the position of the rotor, A downstream temperature detection unit detects the downstream temperature, which is the temperature downstream of the evaporator. An upstream temperature detection unit for detecting the upstream temperature, which is the temperature upstream of the evaporator, A control unit that prevents overcurrent to the sensorless DC motor based on the time since startup, the downstream temperature, and the upstream temperature, Equipped with, The control unit, A calculation unit that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, A comparison unit compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value. A ventilation device comprising: an opening degree control unit that, after a certain period of time has elapsed since the start-up, if the difference value obtained from the comparison by the comparison unit is greater than or equal to the threshold value, sets the opening degree of the expander to a predetermined opening degree or greater.

3. An air supply fan that supplies air from outside the space into the space as an air supply flow, A refrigeration cycle is used in which the refrigerant is circulated in the order of compressor, condenser, expander, and evaporator, and a dehumidification unit is used to dehumidify the supply airflow, A motor for driving the compressor, which is a sensorless DC motor that does not have a sensing element for detecting the position of the rotor, A downstream temperature detection unit detects the downstream temperature, which is the temperature downstream of the evaporator. An upstream temperature detection unit for detecting the upstream temperature, which is the temperature upstream of the evaporator, A control unit that prevents overcurrent to the sensorless DC motor based on the time since startup, the downstream temperature, and the upstream temperature, Equipped with, The control unit, The system includes a calculation unit that calculates the temperature difference between the upstream temperature and the downstream temperature at predetermined intervals. A comparison unit compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value. A ventilation device comprising: an air supply airflow control unit that, after a certain period of time has elapsed since the start-up, if the difference value obtained from the comparison by the comparison unit is greater than or equal to the threshold value, reduces the air supply airflow of the air supply fan to a predetermined air supply airflow.

4. The ventilation device according to any one of claims 1 to 3, wherein the time from the time when the past temperature difference was calculated to the time when the current temperature difference was calculated is within 10 minutes.

5. Ventilation section, An exhaust fan that exhausts the air in the space to the outside of the space as an exhaust flow, It comprises a heat exchange element that exchanges heat between the supply airflow and the exhaust airflow, The aforementioned ventilation section is An air intake fan that supplies air from outside the space into the space as an air intake flow, A refrigeration cycle is used in which the refrigerant is circulated in the order of compressor, condenser, expander, and evaporator, and a dehumidification unit is used to dehumidify the supply airflow, A motor for driving the compressor, which is a sensorless DC motor that does not have a sensing element for detecting the position of the rotor, A downstream temperature detection unit detects the downstream temperature, which is the temperature downstream of the evaporator. An upstream temperature detection unit for detecting the upstream temperature, which is the temperature upstream of the evaporator, The system includes a control unit that prevents overcurrent to the sensorless DC motor based on the time since startup, the downstream temperature, and the upstream temperature. The control unit, A calculation unit that calculates the temperature difference between the downstream temperature and the upstream temperature at predetermined intervals, A comparison unit compares a difference value, which is the difference between the past temperature difference calculated by the calculation unit and the current temperature difference calculated by the calculation unit, with a threshold value. A heat exchange ventilation system comprising: a rotation speed control unit that, after a certain period of time has elapsed since the start-up, if the difference value obtained from the comparison by the comparison unit is greater than or equal to the threshold value, reduces the rotation speed of the sensorless DC motor to a predetermined rotation speed or less.

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