Range hood

Abstract

To provide a range hood which can suppress and prevent the generation of an impact (noise), is suppressed in the failure risk and adverse effect on a product life, and can reduce the manufacturing cost even when switching an operation mode of an exhaust fan to a low-rotation operation mode which is low in the rotation number of the exhaust fan from a high-rotation operation mode which is high in the rotation number of the exhaust fan.SOLUTION: When switching an operation mode of an exhaust fan 101 to a low-rotation operation mode which is low in the rotation number of the exhaust fan to a high-rotation operation mode which is high in the rotation number of the exhaust fan, the switching to the low-rotation operation mode is performed after making a non-load state that drive power is not supplied to an AC motor 107 interposed between the high-rotation operation mode and the low-rotation operation mode for a prescribed time.SELECTED DRAWING: Figure 5A

Description

Technical Field

[0001] The present invention relates to, for example, a range hood used together with cooking appliances, and more specifically to a range hood configured to be capable of switching exhaust air volume.

Background Art

[0002] There is a type of range hood configured such that an AC motor rotates an exhaust fan (blower) to perform exhaust, and the exhaust air volume is switched by switching the driving power supplied to the AC motor to adjust the rotation speed of the exhaust fan.

[0003] However, in the conventional range hood as described above, when the operating state of the range hood is changed by switching the rotation speed of the AC motor and changing the rotation speed of the exhaust fan (especially when the rotation speed of the AC motor is switched abruptly), abnormal noise (impact noise) may occur due to impact caused by the deviation between the rotation speed from the moment of inertia of the exhaust fan and the shaft speed from power switching of the exhaust fan. In addition, the aforementioned impact is also unfavorable in that it adversely affects the durability of components. This tendency is particularly pronounced in range hoods that employ a simple attachment / detachment structure allowing the exhaust fan to be attached to and detached from the motor shaft with one touch.

[0004] Further, as a range hood capable of switching exhaust air volume as described above and a control method thereof, Patent Document 1 discloses an invention of a range hood and a control method thereof, wherein when changing the operating state of the range hood by switching the rotation speed through changing energization to the windings of an electric motor according to an operation signal sent from a switch, energization is changed while maintaining the energization before the rotation speed switching, and the energization before the switching is stopped after a predetermined time has elapsed (that is, the energization states are overlapped for switching). With this configuration, no non-energization time occurs when switching the rotation speed of the electric motor, no large torque change is generated, and thus abnormal noise does not occur from the blower (exhaust fan).

[0005] Furthermore, according to the invention described in Patent Document 1, by switching the rotation speed of the electric motor to change the rotation speed of the fan, it is possible to suppress the generation of abnormal noise from the exhaust fan when the operating state of the range hood is changed (especially when the rotation speed of the electric motor is changed abruptly). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-257056 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, in the case of the range hood and its control method described in Patent Document 1 above, the power supply state is overlapped and switched, which can result in temporary overcurrent and overload the exhaust fan's power supply. This necessitates a higher output power supply, leading to increased manufacturing costs (raw material costs) and undesirable effects on the risk of failure and product lifespan.

[0008] The present invention aims to solve the above problems by providing a range hood that can suppress and prevent the occurrence of shocks (abnormal noises) when switching the exhaust fan's operating mode from a high-speed operation mode to a low-speed operation mode, thereby reducing the risk of failure and adverse effects on product lifespan, and reducing manufacturing costs. [Means for solving the problem]

[0009] To achieve the above objectives, the range hood of the present invention is A range hood configured to rotate an exhaust fan using an AC motor to exhaust air, and to control the rotation speed of the exhaust fan by switching the power supplied to the AC motor, thereby switching the amount of air blown by the exhaust fan to a predetermined number of stages, The operating mode of the exhaust fan is configured such that, when switching from a high-speed operation mode where the exhaust fan rotates at a high rotational speed to a low-speed operation mode where the exhaust fan rotates at a low rotational speed, a no-load state in which no driving power is supplied to the AC motor is interposed for a predetermined period of time between the high-speed operation mode and the low-speed operation mode before the switch to the low-speed operation mode occurs. It is characterized by the following.

[0010] In the range hood of the present invention, The rotating shaft of the aforementioned AC motor is provided with a male screw portion. The mounting jig for attaching the exhaust fan to the rotating shaft is provided with a female screw portion. The exhaust fan is attached to the rotating shaft of the AC motor by screwing the female threaded portion of the mounting jig onto the male threaded portion of the rotating shaft and tightening it, and The mounting jig can be configured such that the tightening direction of the female screw portion is opposite to the rotation direction of the exhaust fan driven by the AC motor.

[0011] Furthermore, the system may be configured to include a rotation speed detection means for detecting the rotation speed of the exhaust fan, and if the rotation speed detected by the rotation speed detection means exceeds a predetermined upper limit, the system may switch from the high-speed operation mode to the low-speed operation mode after a predetermined period of no-load conditions.

[0012] Furthermore, the system may be configured to include a blockage detection means for detecting the blockage state of the exhaust path, which is the path for the gas exhausted by the exhaust fan, and if the blockage detected by the blockage detection means exceeds a predetermined degree of blockage, the system will switch from the high-speed operation mode to the low-speed operation mode via a predetermined period of no-load state.

[0013] Furthermore, it is also possible to configure the system so that the predetermined no-load state is 1.0 second or longer and 3.0 seconds or shorter. [Effects of the Invention]

[0014] The range hood of the present invention is configured such that when switching the exhaust fan's operating mode from a high-speed operation mode to a low-speed operation mode, a no-load state in which no driving power is supplied to the AC motor is interposed for a predetermined period of time between the high-speed and low-speed operation modes before switching to the low-speed operation mode. This suppresses and prevents the generation of abnormal noise caused by the shock resulting from the mismatch between the exhaust fan's moment of inertia and its axial speed when switching from the high-speed to the low-speed operation mode.

[0015] Furthermore, the mismatch between the exhaust fan's moment of inertia and its axial speed reduces the risk of failure and shortened product life caused by shocks to the exhaust fan and other equipment. In other words, when the rotational speed changes due to tap switching (switching of drive power) performed by the AC motor, the load on the mating part between the AC motor's rotating shaft and the exhaust fan can be reduced, thereby suppressing and preventing problems such as increased failure risk and shortened product life.

[0016] Furthermore, as in the case of the range hood described in Patent Document 1, which switches the power supply state to the AC motor by overlapping, it becomes possible to avoid situations such as temporary overcurrent, thereby suppressing overload on the power supply and preventing the need for a high-output power supply. This reduces concerns such as increased risk of failure, shortened product lifespan, and increased manufacturing costs (raw material costs).

[0017] Furthermore, if the tightening direction of the female screw portion of the mounting jig is configured to be opposite to the rotation direction of the exhaust fan driven by the AC motor, when switching from a high-speed rotation mode, where the fan rotates at high speed due to the moment of inertia, to a low-speed rotation mode, the screw portion of the mounting jig may loosen due to the impact caused by the difference in the shaft speed of the exhaust fan (rotation speed of the exhaust fan > shaft speed). However, in the present invention, when switching from a high-speed rotation mode to a low-speed rotation mode, a predetermined period of no load is intervened before switching to the low-speed rotation mode. This suppresses a sudden decrease in the rotation speed of the exhaust fan and prevents the screw portion of the mounting jig from loosening.

[0018] In other words, loosening of the screw fastening occurs when the impact caused by the mismatch between the exhaust fan's moment of inertia and its axial speed exceeds the frictional resistance of the screw fastening. However, by introducing a no-load state for a predetermined period of time between the high-speed and low-speed operation modes before switching to the low-speed operation mode, it becomes possible to suppress an excessively rapid decrease in the exhaust fan's rotational speed. As a result, it becomes possible to prevent the impact caused by the mismatch between the exhaust fan's moment of inertia and its axial speed from exceeding the frictional resistance of the screw fastening, thereby preventing the screw fastening from loosening and improving reliability.

[0019] Further, the present invention comprises a rotational speed detection means for detecting the rotational speed of an exhaust fan, and when the rotational speed detected by the rotational speed detection means exceeds a predetermined upper limit value, if switching from the high-speed rotation operation mode to the low-speed rotation operation mode is performed immediately, the difference between the moment of inertia in the high-speed rotation operation mode and the torque of the AC motor in the low-speed rotation operation mode becomes large, which causes large impact, and easily leads to the generation of abnormal noise and damage to equipment. However, if switching from the high-speed rotation operation mode to the low-speed rotation operation mode is performed via a no-load state for a predetermined period of time, the impact during switching can be reliably suppressed, and the present invention can be made more effective.

[0020] Further, the present invention comprises a blockage state detection means for detecting a blockage state of an exhaust path which is the path of gas exhausted by the exhaust fan, and even when the blockage state detected by the blockage state detection means exceeds a predetermined blockage degree, if switching from the high-speed rotation operation mode to the low-speed rotation operation mode is performed immediately, the difference between the moment of inertia in the high-speed rotation operation mode and the torque of the AC motor in the low-speed rotation operation mode becomes large, which causes large impact, and easily leads to the generation of abnormal noise and damage to equipment. However, if switching from the high-speed rotation operation mode to the low-speed rotation operation mode is performed via a no-load state for a predetermined period of time, the impact during switching can be reliably suppressed, and the present invention can be made more effective.

[0021] The duration of the no-load state to be secured before switching from the high-speed rotation operation mode to the low-speed rotation operation mode is affected by conditions such as the rotational speed of the exhaust fan in the high-speed rotation operation mode and the low-speed rotation operation mode. Generally, when the duration of the no-load state is less than 1.0 second, the effect of impact suppression becomes insufficient, and even when the duration exceeds 3.0 seconds, no significant improvement in the effect is observed. Therefore, it is generally desirable to secure a duration of 1.0 second or more and 3.0 seconds or less. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0022] [Figure 1] It is a notched front view of a range hood according to an embodiment of the present invention. [Figure 2] It is a front view showing the configuration of an operating unit of a range hood according to an embodiment of the present invention. [Figure 3] It is a diagram illustrating a mode of air volume switching by an operation / air volume switch in the range hood according to an embodiment of the present invention. [Figure 4] It is a diagram illustrating a mode of switching of timer set time by a timer switch in the range hood according to an embodiment of the present invention. [Figure 5A] (a) and (b) are diagrams for explaining the operation of the range hood according to an embodiment of the present invention. [Figure 5B] (a) and (b) are diagrams for explaining the operation of a conventional range hood. [Figure 6] It is a notched front view of a range hood according to another embodiment of the present invention. [Figure 7] It is a diagram showing the main configuration of a range hood according to still another embodiment of the present invention, wherein (a) is a diagram showing a state where an exhaust path is blocked, and (b) is a diagram showing a state where the exhaust path is not blocked. MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be shown to describe the characteristic features thereof in further detail.

[0024] [Embodiment] In this embodiment, a range hood configured to be capable of switching the air volume of an exhaust fan to a plurality of predetermined stages (four stages in the present embodiment) by switching the driving power to an AC motor to control the rotation speed of the exhaust fan will be described as an example.

[0025] As shown in FIG. 1, the range hood 110 according to the embodiment of the present invention is installed and used in a kitchen together with a gas stove (not shown), and a commercial power supply (AC 100V) is used as a power supply for operating the range hood 110.

[0026] The range hood 110 includes an exhaust fan 101, an AC motor 107 that drives the exhaust fan 101, a hood section 103 which is an air intake for the kitchen, and an exhaust duct 106.

[0027] The system is configured such that the air drawn into the kitchen from the hood section 103 is expelled to the outside (outside) of the kitchen via the exhaust path by energizing the AC motor 107 that drives the exhaust fan 101.

[0028] In this embodiment of the range hood, an extension exhaust pipe (not shown) is connected to the exhaust duct 106 of the range hood 110, and the air from inside the kitchen drawn in from the hood section 103 of the range hood 110 is discharged outside the kitchen through the exhaust duct 106 and the extension exhaust pipe. Therefore, the exhaust duct 106 and the extension exhaust pipe connected thereto constitute the exhaust path in this invention.

[0029] <Characteristic Structure> Next, a characteristic configuration of the range hood 110 according to an embodiment of the present invention will be described.

[0030] The range hood 110 according to this embodiment has four modes for controlling the exhaust airflow: "high power," "medium power," "low power," and "continuous ventilation." Note that "continuous ventilation" is a control mode that has less airflow (lower exhaust fan rotation speed) than "low power," which is the "lowest power" setting.

[0031] In the range hood 110 of the present invention, the rotation speed of the exhaust fan 101 can be controlled by switching the drive power to the AC motor 107 that rotates the exhaust fan 101, thereby enabling the airflow of the exhaust fan 101 to be switched between a predetermined number of stages (in the range hood 110 of this embodiment, there are four stages: "high speed," "medium speed," "low speed," and "continuous ventilation (lowest speed)"). Furthermore, the general operating state of the range hood 110 is controlled by the control unit 20.

[0032] In the range hood 110 according to this embodiment, the rotation speed (airflow rate) of the exhaust fan 101 can be switched in multiple stages by switching terminals (taps) taken from predetermined positions on the motor windings that make up the AC motor 107 for rotating the exhaust fan 101 using a switch. In other words, the taps are switched using a switch so that the number of motor windings corresponds to the rotation speed of the exhaust fan 101.

[0033] Figure 2 shows the configuration of the control unit 50 of the range hood 110 according to this embodiment. As shown in Figure 2, the control unit 50 includes an off switch / lock 51, an operation / airflow switch 52, a timer switch 53, a lighting switch 54, a cleaning switch 55, and a continuous ventilation switch 56.

[0034] The power switch / lock 51 switches the power ON / OFF and, when pressed and held for 3 seconds, switches the child lock ON / OFF. When the child lock is engaged, all switches except the light switch 54 are configured not to respond (not to receive commands). The light switch 54 is configured to switch ON / OFF each time it is pressed.

[0035] The operation / airflow switch 52 is configured so that the airflow changes each time the operation / airflow switch 52 is pressed while the power is ON. Specifically, as shown in Figure 3, for example, the airflow is configured to switch in the order of "low," "medium," and "high" each time the operation / airflow switch 52 is pressed.

[0036] Furthermore, the range hood 110 according to this embodiment is equipped with a constant ventilation switch 56. The constant ventilation switch 56 is configured to turn ON (the display lights up) when pressed and OFF (the display turns off) when pressed for 3 seconds. In this embodiment, even when the range hood 110 is operating under one of the following conditions, selected by the operation / airflow switch 52 ("high operation," "medium operation," or "low operation"), pressing the continuous ventilation switch 56 turns on the continuous ventilation, and the "high operation," "medium operation," or "low operation" selected by the operation / airflow switch 52 is reset (cancelled). Furthermore, when the continuous ventilation switch 56 is ON, the continuous ventilation operation continues even after the operation of the range hood 110 is stopped by pressing the OFF switch 51. In other words, the exhaust fan 101 continues to operate at a low rotation speed for continuous ventilation (for example, 300 rpm).

[0037] Furthermore, while the range hood 110 is in operation, each time the timer switch 53 on the control unit 50 is pressed, the timer setting is configured to switch in the order of 5 minutes → 10 minutes → 15 minutes → off, as shown in Figure 4. Note that although only numbers are shown in Figure 4, the unit for each is "minutes".

[0038] The range hood 110 will either stop operating when the timer switch 53 expires, or, if the continuous ventilation switch is ON, ventilation will continue in continuous ventilation mode (the lights will be turned off).

[0039] Furthermore, the maintenance switch 55 is configured to light up when the total operating time reaches a predetermined time (for example, 1000 hours), and to be reset and the display turns off when the maintenance switch 55 is pressed after the maintenance is completed.

[0040] In the range hood 110 according to this embodiment, when switching from the high-speed operation mode (in this embodiment, the "strong operation" mode, where the exhaust fan 101 rotates at its highest speed (1000 rpm)) to the low-speed operation mode (in this embodiment, either the "continuous ventilation" mode, where the exhaust fan 101 rotates at its lowest speed (300 rpm), or the "weak operation" mode, where the rotation speed is the next lowest (400 rpm)), a no-load state in which no driving power is supplied to the AC motor 107 is interposed between the high-speed operation mode and the low-speed operation mode for a predetermined period of time (1 second in this embodiment) before switching from the high-speed operation mode to the low-speed operation mode.

[0041] By the way, in conventional range hoods that use an AC motor to operate the exhaust fan, when switching from a high-speed operation mode such as "strong" to a low-speed operation mode such as "weak" or "continuous ventilation," the difference between the moment of inertia in the high-speed operation mode and the axial speed of the exhaust fan, which drops sharply due to the switch to the low-speed operation mode, becomes large. In other words, a discrepancy occurs between the rotational speed of the exhaust fan, which was rotating at high speed due to its moment of inertia, and the shaft speed of the exhaust fan, which drops sharply due to the power switch (exhaust fan rotational speed > shaft speed). This can cause shocks that result in abnormal noises (impact noises) or damage to equipment such as the exhaust fan. This tendency is particularly pronounced in range hoods that employ a simple detachable structure that allows the exhaust fan to be attached to and detached from the motor shaft with a single touch.

[0042] In contrast, in the range hood 110 according to this embodiment, as described above, a no-load state in which no driving power is supplied to the AC motor 107 is interposed between the high-speed operation mode and the low-speed operation mode for a predetermined period of time (1 second in this embodiment) before switching from the high-speed operation mode to the low-speed operation mode. Therefore, even when switching from the high-speed operation mode (the "strong operation" mode in this embodiment) to the low-speed operation mode (either the "continuous ventilation operation" mode or the "weak operation" mode), it is possible to suppress and prevent the generation of abnormal noise due to impact or damage to equipment such as the exhaust fan.

[0043] The specific operation (function) of the range hood 110 according to this embodiment will be explained with reference to Figures 5A(a) and (b). Figure 5A(a) shows the switching (ON / OFF) of the motor tap and the manner in which a no-load state is introduced when switching from high-speed operation to continuous ventilation operation, and Figure 5A(b) shows the manner in which the rotation speed of the exhaust fan decreases when the operating mode is switched from high-speed operation to continuous ventilation operation after an intervening no-load state of 1 second.

[0044] When the range hood 110 according to this embodiment is operated in high-speed mode, if "high-speed operation" is selected with the operation / airflow switch 52, the motor tap for high-speed operation is switched on, the exhaust fan 101 rotates at 1000 rpm, and the range hood 110 is operated in high-speed mode.

[0045] Subsequently, to switch the range hood 110 to continuous ventilation mode, pressing the continuous ventilation switch 56 switches the motor tap to the continuous ventilation mode, the exhaust fan 101 rotates at 300 rpm, and the range hood 110 operates in continuous ventilation mode. Pressing the continuous ventilation switch 56 also resets (cancels) the "high power" setting that was selected by the operation / airflow switch 52.

[0046] Furthermore, in the range hood 110 according to this embodiment, when switching the operating mode from high-speed operation to continuous ventilation operation, a no-load state in which no driving power is supplied to the AC motor 107 is introduced for 1 second before switching the operating mode to continuous ventilation operation.

[0047] Thus, when switching from high-speed operation to continuous ventilation operation, a 1-second no-load state is introduced, causing the rotational speed of the exhaust fan 101 to gradually decrease from 1000 rpm to 300 rpm, as shown in Figure 5A(b).

[0048] In Figure 5A(b), the solid line L1 shows the mode of decrease in the rotational speed of the exhaust fan 101 in this embodiment. Furthermore, the dotted line L2, which is drawn along and extending from the solid line L1 showing the decrease in the rotational speed of the exhaust fan, shows the mode of decrease in the rotational speed of the exhaust fan when the supply of driving power to the AC motor 107 is stopped.

[0049] On the other hand, Figure 5B(a) shows the manner in which the motor tap is switched (ON / OFF) when switching from high-speed operation to continuous ventilation operation without going through a no-load state, and Figure 5B(b) shows the manner in which the rotational speed of the exhaust fan decreases when the operating mode is switched from high-speed operation to continuous ventilation operation without going through a no-load state. In Figure 5B(b), the solid line L1a shows the manner in which the rotational speed of the exhaust fan decreases, and the dotted line L2 shows the manner in which the rotational speed of the exhaust fan decreases when the supply of drive power to the AC motor 107 is set to 0 (when the power is off).

[0050] As shown in Figures 5B(a) and (b), in the case of conventional range hoods configured to switch the operating mode from high-speed operation to continuous ventilation operation immediately without an intervening no-load state, a rapid decrease in rotational speed occurs due to the switch, and the discrepancy between the rotational speed of the exhaust fan due to the moment of inertia and the shaft speed due to the power switch (exhaust fan rotational speed > shaft speed) becomes large. In other words, as shown in Figure 5B(b), a rapid decrease in rotational speed occurs in the region indicated by S within 1 second after switching the operating mode from high-speed operation to continuous ventilation operation. The shock caused by this rapid decrease in rotational speed can lead to the generation of abnormal noise (impact noise) and damage to equipment such as the exhaust fan.

[0051] In contrast, in the case of the range hood 110 according to this embodiment, as described above, when switching the operating mode from high-speed operation to continuous ventilation operation, a no-load state is introduced for 1 second before switching the operating mode to continuous ventilation operation. Therefore, in the no-load state, the tendency for the rotation speed of the exhaust fan to decrease is the same as when the supply of driving power to the AC motor 107 is stopped (when the power is turned off), and a sudden decrease in rotation speed is not caused. As a result, even when switching from a high-speed operation mode (e.g., "high-speed operation" mode) to a low-speed operation mode (e.g., "continuous ventilation operation" mode), it is possible to suppress and prevent the generation of abnormal noise due to impact and damage to equipment such as the exhaust fan.

[0052] Furthermore, in the range hood of the present invention, when switching the operating mode from high-speed operation to low-speed operation (an operating mode in which the rotation speed of the exhaust fan 101 is slightly higher than that of "continuous ventilation operation"), the system is configured to switch to low-speed operation after an intervening period of no load for 1 second. In this case as well, effects similar to those obtained when switching the operating mode from high-speed operation to continuous ventilation operation can be obtained.

[0053] Furthermore, in the range hood 110 according to this embodiment, although not specifically shown, the rotating shaft of the AC motor 107 is provided with a male threaded portion, and the mounting jig for attaching the exhaust fan 101 to the rotating shaft of the AC motor 107 is provided with a female threaded portion. The exhaust fan 101 is held on the rotating shaft of the AC motor 107 by screwing the female threaded portion of the mounting jig onto the male threaded portion of the rotating shaft and tightening it. The tightening direction of the female threaded portion of the mounting jig is configured to be opposite to the rotation direction of the exhaust fan driven by the AC motor.

[0054] Therefore, when switching from a high-speed rotation mode (e.g., "strong operation" mode) to a low-speed rotation mode (e.g., "continuous ventilation operation" mode) due to the moment of inertia, the screw fastening part of the mounting jig may loosen due to the impact caused by the deviation in the shaft speed of the exhaust fan (rotation speed of the exhaust fan > shaft speed). However, in this embodiment, as described above, when switching the operation mode from strong operation to continuous ventilation operation, a no-load state is intervened for 1 second before switching the operation mode to continuous ventilation operation. This prevents a sudden decrease in the rotation speed of the exhaust fan, thus preventing the screw fastening part of the mounting jig from loosening, and enabling the realization of a highly reliable range hood.

[0055] In the range hood 110 according to the above embodiment, the time to be maintained in a no-load state when switching from the high-speed operation mode to the low-speed operation mode is set to 1 second. However, the time to be maintained in a no-load state (predetermined time) is affected by conditions such as the rotation speed of the exhaust fan in the high-speed operation mode and the low-speed operation mode, but is usually preferably between 1.0 second and 3.0 seconds. This is because if the no-load state time is less than 1.0 second, the shock suppression effect becomes insufficient, and even if it exceeds 3.0 seconds, no significant improvement in effect is observed. However, if there is no particular problem with the user experience, it is also possible to set the time to exceed 3.0 seconds (for example, 5 seconds).

[0056] Figure 6 is a cutaway front view of a range hood 110A according to another embodiment of the present invention.

[0057] As shown in Figure 6, this range hood 110A is equipped with a rotation speed detection means 121 for detecting the rotation speed of the exhaust fan 101. When the rotation speed detected by the rotation speed detection means 121 exceeds a predetermined upper limit, the system is configured to switch from a high rotation speed operation mode to a low rotation speed operation mode after a predetermined period of no load (1 second in this embodiment). The other configurations are the same as those of the range hood 110 according to the above embodiment.

[0058] The rotation speed detection means 121 is configured to include a permanent magnet (not shown) attached to the exhaust fan 101 and a Hall IC circuit (magnetic sensor) 121a. When the exhaust fan 101 rotates, the permanent magnet attached to the exhaust fan 101 is detected to pass near the Hall IC circuit (magnetic sensor) 121a, thereby detecting the rotation speed of the exhaust fan 101.

[0059] Furthermore, if the detected rotational speed of the exhaust fan 101 is above a predetermined value, the system is configured to switch from high-speed operation mode to low-speed operation mode via a 1-second no-load state, similar to the case of the range hood 110 in the above-described embodiment.

[0060] With the range hood 110A configured in this way, it becomes possible to reliably suppress the shock when switching to the low-speed operation mode, thereby better reducing the negative impact on the product's lifespan (risk of malfunction).

[0061] Furthermore, Figures 7(a) and 7(b) show the main components of a range hood 110B according to yet another embodiment of the present invention, where (a) shows the case when the exhaust path is blocked and (b) shows the case when the exhaust path is not blocked. The basic configuration of the range hood 110B according to this embodiment is the same as that of the range hood 110 shown in Figure 1.

[0062] This range hood 110B is equipped with a blockage detection means for detecting the blockage state of the exhaust path, which is the path for the gas exhausted by the exhaust fan 101. In this embodiment of the range hood 110B, the exhaust duct 106 and an extension exhaust pipe (not shown) connected thereto form the exhaust path.

[0063] The blockage detection means provided in the range hood 110B of this embodiment consists of a backflow-stopping blockage plate 131, a rotating support shaft 132 of the backflow-stopping blockage plate 131, a rotary encoder (not shown), and a control unit 20 that determines the blockage state of the exhaust path, which is the path of gas exhausted by the exhaust fan, based on information about the rotation angle θ of the rotating support shaft 132 detected by the rotary encoder and the operation information of the exhaust fan. The other configurations are the same as those in the range hood 110 (Figure 1) according to the above embodiment.

[0064] Furthermore, in the blockage detection means, when the exhaust fan 101 is operating at high speed, if the rotation angle θ of the backflow stopper closure plate 131 is less than or equal to a predetermined angle (for example, θ = 30° or less), the control unit 20 determines that the exhaust path is blocked. Note that as the amount of air passing through the exhaust path decreases, the rotation angle θ of the backflow stopper closure plate 131 decreases.

[0065] Furthermore, if it is determined that the exhaust path is blocked, the system is configured to switch from high-speed operation mode to low-speed operation mode after a 1-second no-load state, similar to the case of the range hood 110 in the above-described embodiment.

[0066] In the case of the range hood 110B configured in this way, it becomes possible to reliably suppress the shock when switching to the low-speed operation mode, thereby better reducing the negative impact on the product's lifespan (risk of malfunction).

[0067] The present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the invention. [Explanation of symbols]

[0068] 20 Control Unit 50 Control section 51 Off switch / lock 52 Operation / Airflow Switch 53 Timer switch 54 Light switch 55 Cleaning switch 56 Continuous ventilation switch 101 Exhaust fan 103 Food Section 106 Exhaust duct 107 AC motor 110 Range Hood 110A Range hood according to another embodiment 110B Range hood according to another embodiment 121 Rotation speed detection means 121a Hall IC circuit (magnetic sensor) constituting the rotation speed detection means 131 Backflow-blocking occlusion plate constituting the occlusion state detection means 132 Rotation support shaft of the backwind blocking plate θ Rotation angle of the pivot axis

Claims

1. A range hood is configured to rotate an exhaust fan using an AC motor to exhaust air, and to control the rotation speed of the exhaust fan by switching the power supplied to the AC motor, thereby switching the amount of air blown by the exhaust fan to a predetermined number of stages, As a method for switching the airflow rate of the exhaust fan to a predetermined number of stages, terminals (taps) taken from predetermined positions on the motor windings constituting the AC motor for rotating the exhaust fan are switched by a switch; that is, the taps are switched by a switch so that the number of motor windings corresponds to the rotation speed of the exhaust fan. A range hood characterized in that, when switching the operating mode of the exhaust fan from a high-speed operation mode in which the exhaust fan rotates at a high rotational speed to a low-speed operation mode in which the exhaust fan rotates at a low rotational speed, a no-load state in which no driving power is supplied to the AC motor is interposed for a predetermined period of time between the high-speed operation mode and the low-speed operation mode before switching to the low-speed operation mode.

2. The rotating shaft of the aforementioned AC motor is provided with a male screw portion. The mounting jig for attaching the exhaust fan to the rotating shaft is provided with a female screw portion. The exhaust fan is attached to the rotating shaft of the AC motor by screwing the female threaded portion of the mounting jig onto the male threaded portion of the rotating shaft and tightening it, and The range hood according to claim 1, characterized in that the tightening direction of the female screw portion of the mounting jig is configured to be opposite to the rotation direction of the exhaust fan driven by the AC motor.

3. The range hood according to claim 1, further comprising an obstruction state detection means for detecting an obstruction state of the exhaust path, which is a path for gas exhausted by the exhaust fan, wherein if the obstruction state detected by the obstruction state detection means exceeds a predetermined degree of obstruction, the range hood is configured to switch from the high-speed operation mode to the low-speed operation mode via a predetermined period of no-load state.

4. The range hood according to any one of claims 1 to 3, characterized in that the no-load state for the predetermined time is 1.0 second or more and 3.0 seconds or less.

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