A DC motor, a DC motor control method, and a cooking appliance

Abstract

This invention provides a DC motor, a DC motor control method, and a cooking appliance, relating to the technical field of cooking appliances. The DC motor is installed inside the cooking appliance and includes a drive board. The drive board includes a VDC terminal for controlling the positive power supply, a GND terminal for controlling the ground wire, an FG terminal for controlling the feedback signal, and a PWM terminal for controlling the rotation speed and direction. This invention alleviates the technical problems of numerous control terminal interfaces, complex control, high cost, and poor reliability associated with DC motors used in cooking appliances with heating fans. It optimizes the driver program for DC motors in cooking appliances, achieving the technical effects of simplifying DC motor costs and improving reliability.

Description

Technical Field

[0001] This invention relates to the field of cooking appliance technology, and in particular to a DC motor, a DC motor control method, and a cooking appliance. Background Technology

[0002] Steam ovens, ovens, and steam ovens, which are sealed kitchen appliances used to heat food, have gradually come into the public eye in recent years. Most of them use a heating fan to enhance heat convection within the appliance cavity to heat the food. Specifically, the motor body is fixed to the outer side of the rear wall of the inner cavity, and the shaft extends into the cavity through an opening in the inner cavity to drive the fan blades to rotate.

[0003] Currently, most kitchen appliances using heating fans employ AC motors, which can only rotate in one direction at a single speed. This lack of flexibility in changing the rotation speed and direction makes it difficult to ensure uniform temperature within the cavity, complicating product development and testing, and compromising the cooking results for users. Using DC motors, however, allows for speed adjustment and reversal, resulting in better temperature uniformity and cooking performance.

[0004] However, the control board of current DC motors has many drive terminals, usually five terminals, including VDC terminal for controlling the positive power supply, GND terminal for controlling the ground, FG terminal for controlling the feedback signal, CW / CCW terminal for controlling the rotation direction, and PWM terminal for controlling the speed.

[0005] Existing DC motors are typically powered by VDC and GND, with speed regulated by the duty cycle of a PWM signal, speed and direction data fed back via FG, and the rotation direction controlled by the high and low levels of CW / CCW. This makes the control board for DC motors complex, costly, and prone to failure with poor reliability. Summary of the Invention

[0006] The purpose of this invention is to provide a DC motor, a DC motor control method, and a cooking appliance, so as to alleviate the technical problems of existing cooking appliances with heating fans having a large number of DC motor control terminal interfaces, complex control, high cost, and poor reliability.

[0007] The present invention provides a DC motor for installation in the inner pot of a cooking appliance, comprising a drive board: the drive board includes a VDC terminal for controlling the positive power supply, a GND terminal for controlling the ground wire, an FG terminal for controlling the feedback signal, and a PWM terminal for controlling the rotation speed and direction of rotation.

[0008] Furthermore, the DC motor includes a motor body, a bracket, and a sealing assembly; the motor body has a motor shaft; the bracket has a shaft hole, and the bracket is fitted onto the motor shaft through the shaft hole, with the motor shaft passing through the bracket and into the inner liner; the sealing assembly is fitted onto the motor shaft, and a sealed space is formed between the inner liner, the bracket, the motor shaft, and the sealing assembly.

[0009] Furthermore, the sealing assembly includes a first seal, which is sleeved on the motor shaft and installed between the bracket and the inner liner, and is used to press against the inner liner.

[0010] Furthermore, the bracket has a protrusion surrounding the motor shaft on the side facing the inner liner, and the first seal has a first groove surrounding the motor shaft on the side facing the bracket, with the protrusion and the first groove interlocking.

[0011] Furthermore, the first sealing element is a sealing ring structure, and the end face of the first sealing element facing the inner liner is provided with a second groove surrounding the motor shaft.

[0012] Furthermore, the sealing assembly includes a second seal, which is sleeved on the motor shaft and located inside the shaft hole. The second seal is interference-fitted with the hole wall of the shaft hole and the motor shaft, respectively.

[0013] Furthermore, the outer wall of the motor shaft is provided with an annular third groove, and the second seal is installed in the third groove.

[0014] Furthermore, the hole wall of the bracket's shaft hole is annularly stepped, comprising multiple layers of annular steps, with the radius of the annular steps gradually increasing along the direction closer to the inner liner.

[0015] Furthermore, along the direction close to the output end of the motor shaft, the hole wall of the shaft hole is provided with a first layer of annular steps, a second layer of annular steps and a third layer of annular steps, and the second seal is provided in the second layer of annular steps.

[0016] Furthermore, the DC motor also includes a baffle, which is installed on the third layer of annular steps.

[0017] Furthermore, the sealing assembly includes a third seal, which is sleeved on the motor shaft on the side of the bracket away from the inner liner. While the third seal is sealed to the bracket, it also achieves a dynamic sealing fit with the motor shaft.

[0018] Furthermore, the third seal is a sealed bearing.

[0019] Furthermore, the drive board is located on the side of the motor body away from the inner liner.

[0020] Furthermore, the drive board is located on the outside of the cooking appliance and is electrically connected to the motor body.

[0021] A second aspect of the present invention provides a control method for a DC motor, applied to the aforementioned DC motor; the DC motor includes a controller and a PWM terminal for controlling the rotation speed and rotation direction; the method includes: the controller detecting whether the potential of the PWM terminal changes within a set time; if not, the controller sending a rotation direction switching signal to the DC motor to cause the DC motor to switch its rotation direction.

[0022] Furthermore, the PWM terminal is used to output a PWM signal during the operation of the DC motor. The method includes: the controller detecting whether the PWM terminal outputs a PWM signal; if so, the controller sets the speed of the DC motor according to the PWM signal.

[0023] Furthermore, the PWM signal is a square wave. The steps for the controller to set the speed of the DC motor according to the PWM signal include: the controller obtains the duty cycle of the square wave and controls the speed of the DC motor according to the duty cycle.

[0024] Furthermore, the set time is at least an order of magnitude higher than the pulse width of the PWM signal.

[0025] Furthermore, the DC motor also includes an FG terminal for control feedback signals. The method includes: the controller acquiring the speed and direction of rotation of the DC motor fed back by the FG terminal; and the controller setting the speed and direction of rotation of the DC motor based on the acquired speed and direction of rotation of the DC motor.

[0026] A third aspect of the present invention provides a cooking appliance, including an inner pot, a fan blade and the aforementioned DC motor, wherein the DC motor is installed outside the inner pot, the fan blade is installed inside the inner pot, and the motor shaft of the DC motor passes through the inner pot and is connected to the fan blade for transmission.

[0027] The beneficial effects of the DC motor, DC motor control method, and cooking appliance provided by this invention are:

[0028] This invention provides a DC motor, a control method for the DC motor, and a cooking appliance. The DC motor is used to install in the inner pot of the cooking appliance and includes a drive board. The drive board includes a VDC terminal for controlling the positive terminal of the power supply, a GND terminal for controlling the ground wire, an FG terminal for controlling the feedback signal, and a PWM terminal for controlling the rotation speed and direction of rotation.

[0029] This invention controls the motor's rotational speed by adjusting the duty cycle of the PWM signal, and controls the motor's rotational direction by comparing the duration of the PWM signal remaining unchanged with a set time. This integrates the function of controlling the motor's rotational direction from the existing CW / CCW terminals into the PWM terminal, enabling the PWM terminal to control both the DC motor's rotational direction and speed. This reduces the number of terminals and corresponding control circuitry and components, simplifying the DC motor's structure and lowering its production costs and usage risks. This invention also alleviates the technical problems of numerous control terminal interfaces, complex control, high cost, and poor reliability associated with DC motors used in cooking appliances with heating fans.

[0030] The present invention also provides a control method for a DC motor and a cooking appliance, which, since it includes all the technical features of the DC motor described above, also possesses the aforementioned technical effects. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 A schematic diagram of the terminals of a DC motor drive board provided in an embodiment of the present invention;

[0033] Figure 2 A schematic diagram of the structure of a DC motor (with the drive board disposed on the side of the motor body away from the inner tube) provided in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of the structure of a DC motor (with the drive board disposed on the outside of the cooking appliance) provided in an embodiment of the present invention;

[0035] Figure 4 A cross-sectional view of a DC motor provided in an embodiment of the present invention;

[0036] Figure 5 A cross-sectional view of a DC motor (with a third groove on the motor shaft) provided in an embodiment of the present invention;

[0037] Figure 6 A cross-sectional view of a DC motor (with a sealed bearing on the motor shaft) provided in an embodiment of the present invention;

[0038] Figure 7 Square wave diagram of the PWM signal of a DC motor provided in an embodiment of the present invention;

[0039] Figure 8 A logic diagram of a DC motor control method provided in an embodiment of the present invention.

[0040] Icons: 100-Inner liner; 200-Motor shaft; 210-Third groove; 300-Bracket; 310-Protrusion; 400-First seal; 410-First groove; 420-Second groove; 500-Second seal; 510-Baffle; 600-Sealed bearing; 700-Drive plate. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of this invention, it should be noted that the terms "upper," "lower," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," "fourth," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," not that the structure must be completely horizontal, but can be slightly tilted.

[0046] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0047] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0048] Steam ovens, steam ovens, and ovens, which heat food, have gradually come into the public eye in recent years. Most of them use a heating fan to enhance the heat convection inside the appliance to heat the food. Specifically, the motor body is fixed on the outer side of the rear wall of the inner liner, and the shaft extends into the cavity through the opening in the inner liner to drive the fan blades to rotate.

[0049] Currently, most kitchen appliances using heating fans employ AC motors. AC motors can only rotate in one direction at a single speed, making it impossible to change the rotation speed and direction. This makes it difficult to ensure uniform temperature within the cavity, hindering product development and testing, and also compromising the cooking results for users. Using DC motors, on the other hand, allows for speed adjustment and reversal functions, resulting in better temperature uniformity and cooking performance.

[0050] However, current DC motors have a relatively simple structure and poor sealing when installed with the inner cavity, making them unsuitable for the dual operation of a steam oven, which combines steaming and baking functions. During use, steam generated during steaming and volatile gases such as grease generated during baking can seep into the rotor, bearings, and other internal structures behind the support structure along the outer wall of the inner cavity and the motor shaft. This can lead to bearing rust, rotor seizure, and motor failure, increasing maintenance costs and affecting normal use.

[0051] Based on this, the present invention proposes a DC motor, a DC motor control method, and a cooking appliance to alleviate the technical problems of DC motor control terminal interfaces, complex control, high cost, and poor reliability in some cooking appliances with heating fans.

[0052] This invention provides a DC motor for installation in the inner pot 100 of a cooking appliance, including a drive plate 700: as shown Figure 1 As shown, the driver board 700 includes a VDC terminal for controlling the positive power supply, a GND terminal for controlling the ground wire, an FG terminal for controlling the feedback signal, and a PWM terminal for controlling the rotation speed and direction.

[0053] This invention controls the motor's rotational speed by adjusting the duty cycle of the PWM signal, and controls the motor's rotational direction by comparing the duration of the PWM signal remaining unchanged with a set time. This integrates the function of controlling the motor's rotational direction from the existing CW / CCW terminals into the PWM terminal, enabling the PWM terminal to control both the DC motor's rotational direction and speed. This reduces the number of terminals and corresponding control circuitry and components, simplifying the DC motor's structure and lowering its production costs and usage risks. This invention also alleviates the technical problems of numerous control terminal interfaces, complex control, high cost, and poor reliability associated with DC motors used in cooking appliances with heating fans.

[0054] In this embodiment, as Figure 4 As shown, the DC motor includes a motor body, a bracket 300, and a sealing assembly; the motor body has a motor shaft 200; the bracket 300 has a shaft hole, and the bracket 300 is sleeved on the motor shaft 200 through the shaft hole, and the motor shaft 200 is used to pass through the bracket 300 and into the inner liner 100; the sealing assembly is sleeved on the motor shaft 200, and a sealed space is formed between the inner liner 100, the bracket 300, the motor shaft 200, and the sealing assembly.

[0055] For aesthetic reasons, the DC motor is positioned in the space between the inner pot 100 and the outer wall of the cooking appliance. The motor shaft 200 extends into the cavity of the cooking appliance through an opening in the inner pot 100, and the motor body is connected to the inner pot 100 via the motor shaft 200. When the cooking appliance is in use, the motor body drives the motor shaft 200 to rotate, thereby driving the fan blades inside the cooking appliance to rotate, thus enhancing heat convection within the walls of the cooking appliance.

[0056] A sealed space is provided between the inner liner 100 and the motor body. In this embodiment, the sealed space is an annular space surrounding the motor shaft 200, with the inner liner 100 and the support 300 on the left and right walls of the sealed space along the direction of the motor shaft 200, respectively. When the cooking appliance is in use, volatile gases such as water vapor and grease may flow out of the appliance's cavity through the gap between the inner liner 100 and the motor shaft 200, seeping into the internal structures such as the rotor and bearings behind the support 300, or into other devices in the space between the inner liner 100 and the outer wall, causing damage and corrosion. By setting up the sealed space, the volatile gases are sealed within the sealed space, thus avoiding both of these situations.

[0057] In this embodiment, the sealing assembly includes a first sealing element 400, which is sleeved on the motor shaft 200 and installed between the bracket 300 and the inner liner 100. The first sealing element 400 is used to press and abut against the inner liner 100. Specifically, the first sealing element 400 and the motor shaft 200 do not contact each other, and the sealing space is an annular space between the first sealing element 400, the motor shaft 200, the inner liner 100, and the bracket 300. The left and right end faces of this annular space along the direction of the motor shaft 200 are the inner liner 100 and the bracket 300, respectively, and the end faces along the tangential direction of the motor shaft 200 are the outer surface of the motor shaft 200 and the inner surface of the first sealing element 400, respectively. The first sealing element 400 abuts against the inner liner 100 and the bracket 300 respectively along the square of the motor shaft 200. The main function of the first seal 400 is to prevent volatile gases that leak out along the motor shaft 200 from entering the space between the inner pot 100 and the outer wall of the cooking appliance, thus preventing contamination and corrosion of other devices between the inner pot 100 and the outer wall.

[0058] Optional, such as Figure 4 As shown, the bracket 300 has a protrusion 310 surrounding the motor shaft 200 on the side facing the inner liner 100, and the first seal 400 has a first groove 410 surrounding the motor shaft 200 on the side facing the bracket 300. The protrusion 310 and the first groove 410 are interlocked. Specifically, the length of the protrusion 310 is greater than the depth of the first groove 410, and the cross-section of the protrusion 310 is the same as the cross-section of the first groove 410. After the protrusion 310 and the first groove 410 are engaged, the tip of the protrusion 310 abuts against the bottom of the groove 410, and the groove wall of the first groove 410 limits the protrusion 310, thus fixing the first groove 410 and the protrusion 310 relatively. The engagement of the protrusion 310 and the first groove 410 stabilizes the relative position of the first seal 400 and the bracket 300, preventing the first seal 400 from shifting or deforming during the rotation of the DC motor, thus ensuring the stability of the sealing space.

[0059] Preferably, the first sealing element 400 is a sealing ring structure, and the end face of the first sealing element 400 facing the inner liner 100 is provided with a second groove 420 surrounding the motor shaft 200. The inner and outer rings of the second groove 420 provide a double-layer seal at the contact surface between the first sealing element 400 and the inner liner 100, further improving the sealing effect of the first sealing element 400. Furthermore, the second groove 420 ensures that the first sealing element 400 and the inner liner 100 have a double-layer line contact rather than a surface contact. Compared to surface contact, line contact avoids water accumulation and leakage caused by deformation of the contact surface between the first sealing element 400 and the inner liner 100.

[0060] In this embodiment, as Figure 4As shown, the sealing assembly includes a second seal 500, which is sleeved on the motor shaft 200 and located within the shaft hole. The second seal 500 is interference-fitted with both the hole wall of the shaft hole and the motor shaft 200. The second seal 500 blocks the path of volatile gases into the motor body. Its main function is to prevent volatile gases seeping along the motor shaft 200 from entering the motor body and contaminating and corroding the rotor, bearings, and other structures of the motor body.

[0061] Furthermore, such as Figure 5 As shown, an annular third groove 210 is formed on the outer wall of the motor shaft 200, and the second seal 500 is installed in the third groove 210. The third groove 210 prevents the second seal 500 from being misaligned or tilted along the direction of the motor shaft 200, thereby avoiding seal failure that may be caused by misalignment or tilting of the second seal 500. Specifically, the width of the third groove 210 is the same as the width of the second seal 500.

[0062] In this embodiment, the hole wall of the shaft hole of the bracket 300 is in the shape of annular steps, including multiple layers of annular steps, and the radius of the annular steps gradually increases along the direction close to the inner liner 100.

[0063] Specifically, along the direction near the output end of the motor shaft 200, the shaft hole wall is provided with a first layer of annular steps, a second layer of annular steps, and a third layer of annular steps. The second seal 500 is located on the second layer of annular steps. The first layer of annular steps abuts against the outer surface of the motor shaft 200, preventing the second seal 500 from being misaligned towards the motor body.

[0064] Furthermore, such as Figure 4 , Figure 5 As shown, the DC motor also includes a baffle 510, which is installed on the third annular step. The baffle 510 abuts against the lower surface of the third annular step and the outer surface of the motor shaft 200, respectively, preventing the second seal 500 from shifting towards the output end of the motor shaft 200. The baffle 510 and the first annular step respectively limit the second seal 500 to the left and right along the direction of the motor shaft 200, thus stabilizing the position of the second seal 500.

[0065] In this embodiment, as Figure 6As shown, the sealing assembly includes a third seal, which is fitted onto the motor shaft 200 on the side of the bracket 300 opposite to the inner liner 100. The third seal provides a sealing connection with the bracket 300 while also achieving a dynamic seal with the motor shaft 200. Both the third and third seals 500 are fitted onto the motor shaft 200 and abut against its outer surface. The function of both the second and third seals is to prevent volatile gases from seeping into the motor body and contaminating its internal rotor and bearings. Therefore, the second and third seals can be installed simultaneously, or only one of them can be installed, depending on the structure of the DC motor and its sealing requirements.

[0066] Specifically, the third sealing element is a sealing bearing 600. It should be noted that the third sealing element is not necessarily the sealing bearing 600 in this embodiment. It is sufficient as long as it can achieve a dynamic sealing fit with the motor shaft 200 and can play a sealing role along the direction of the motor shaft 200.

[0067] Preferred, such as Figure 2 As shown, the drive board 700 is located on the side of the motor body away from the inner pot 100. In this case, the drive board 700 does not come into contact with the heat source of the cooking appliance, i.e., the inner pot 100, which reduces the operating temperature of the electronic components on the drive board 700, solves the problem of the drive board 700 being unable to withstand high temperatures, and improves the reliability of the drive board 700.

[0068] Optional, such as Figure 3 As shown, the drive board 700 is disposed on the outside of the cooking appliance and is electrically connected to the motor body. This connection method between the drive board 700 and the cooking appliance allows the drive board 700 to operate at room temperature, further ensuring the operating temperature requirements of the drive board 700.

[0069] The structure of a DC motor has been described above. Next, we will explain how the PWM terminal of a DC motor can control both the motor's rotation speed and rotation direction.

[0070] This invention provides a control method for a DC motor, which is applied to the aforementioned DC motor. The DC motor includes a controller and a PWM terminal for controlling the rotation speed and rotation direction. The method includes: the controller detecting whether the potential of the PWM terminal changes within a set time; if not, the controller sending a rotation direction switching signal to the DC motor to switch the rotation direction; if yes, the controller not sending a signal, and the DC motor maintaining its existing rotation direction.

[0071] Specifically, the PWM terminal is used to output a PWM signal during the operation of the DC motor. The control method includes: the controller detecting whether the PWM terminal outputs a PWM signal; if so, the controller sets the speed of the DC motor according to the PWM signal.

[0072] like Figure 7 As shown, the PWM signal is a square wave. The steps for the controller to set the speed of the DC motor according to the PWM signal include: the controller obtains the duty cycle of the square wave and controls the speed of the DC motor according to the duty cycle.

[0073] It should be noted that the setpoint time needs to be at least an order of magnitude higher than the pulse width of the PWM signal. During the normal speed regulation process of the PWM signal, the PWM signal also switches between high and low levels. That is, the PWM signal continuously maintains a high level for a period of time, then a low level for a period of time, then switches back to a high level for a period of time, and so on. To distinguish between the frequency band for regulating the DC motor's rotation direction and the frequency band for normal speed regulation, the setpoint time needs to be at least an order of magnitude higher than the pulse width of the PWM signal. In this case, the duration of maintaining the same level in the frequency band for regulating the DC motor's rotation direction is at least an order of magnitude longer than the duration of maintaining the same level in the frequency band for normal speed regulation, thus avoiding mutual interference between the PWM signals for regulating the DC motor's rotation direction and for normal speed regulation.

[0074] In this embodiment, the DC motor also includes an FG terminal for control feedback signals. The method includes: the controller acquiring the speed and rotation direction of the DC motor fed back by the FG terminal; and the controller setting the speed and rotation direction of the DC motor according to the acquired speed and rotation direction of the DC motor.

[0075] The specific working principle of the DC motor control method provided by this invention is described below:

[0076] The DC motor provided in this embodiment of the invention has four terminals: VDC terminal for controlling the positive power supply, GND terminal for controlling the ground wire, FG terminal for controlling the feedback signal, and PWM terminal for controlling the speed and direction of rotation.

[0077] After the motor is turned on, the VDC and GND terminals provide power. The speed is adjusted by the duty cycle of the PWM signal, the rotation direction is adjusted by detecting the duration during which the PWM signal does not change, and finally the speed and direction data are fed back through the FG terminal.

[0078] Specifically, such as Figure 7As shown, the PWM signal is a square wave with different duty cycles. When the duty cycle is 0%, the square wave is a continuous low level; when the duty cycle is 100%, the square wave is a continuous high level. When the DC motor detects a PWM signal, it starts up and rotates in the default direction. The DC motor can detect the duty cycle of the PWM signal and adjust its speed accordingly; an increased duty cycle increases the motor speed, and a decreased duty cycle decreases the motor speed.

[0079] Simultaneously, the motor detects the duration for which the PWM signal remains at the same level and compares this time with a set time: if the time is less than the set time, the current rotation direction is maintained; if the time is greater than the set time, the motor's rotation direction is changed. For example, Figure 7 The longer straight line in the middle represents the duration for which the PWM signal remains low. If this time is less than the set time, the current rotation direction will be inconvenient; if this time is greater than the set time, the motor rotation direction will be changed.

[0080] It should be noted that since the motor switches between high and low levels during the speed change process, in order to prevent the detection structure from misjudging and changing the direction of motor rotation when the motor is adjusting its speed normally, the setting time should be at least one order of magnitude higher than the pulse width of the PWM signal.

[0081] For example, in this embodiment, the frequency of the PWM signal is 10 kHz, so the pulse width period of the signal is 0.1 ms, and the set time for detecting the change of the motor's rotation direction is 100 ms. That is, the set time is three orders of magnitude higher than the pulse width.

[0082] Depending on the DC motor model and operating environment, the frequency of the PWM signal will vary, and the setpoint time will also change accordingly. The setpoint time should be at least one order of magnitude higher than the PWM signal pulse width. However, if it is too much higher, it will affect the normal speed regulation of the motor. The specific setpoint time should be set according to the frequency of the PWM signal and the motor's operating conditions to avoid misjudgment as much as possible.

[0083] Through the above process, users can control the rotation speed of a DC motor by adjusting the duty cycle, and control the rotation direction by comparing the duration of the PWM signal remaining unchanged with the set time. This integrates the function of controlling the motor rotation direction from the CW / CCW terminals in the prior art into the PWM terminals, reducing one terminal and the corresponding control circuitry and components, simplifying the structure of the DC motor, and reducing the production cost and usage risks of the DC motor.

[0084] The logic diagram of the DC motor control method provided by this invention is as follows: Figure 8 As shown.

[0085] This invention also provides a cooking appliance, including an inner pot 100, a fan blade and the aforementioned DC motor. The DC motor is installed outside the inner pot 100, the fan blade is installed inside the inner pot 100, and the motor shaft 200 of the DC motor passes through the inner pot 100 and is connected to the fan blade for transmission.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A DC motor, characterized in that, For installation in the inner pot (100) of a cooking appliance, including a drive plate (700): The drive board (700) includes a VDC terminal for controlling the positive power supply, a GND terminal for controlling the ground wire, an FG terminal for controlling the feedback signal, and a PWM terminal for controlling the rotation speed and direction of rotation. The PWM terminal is configured to control the rotational speed of the motor by adjusting the duty cycle of the PWM signal, and to control the rotational direction of the motor by comparing the duration during which the PWM signal does not change with a set time. The DC motor includes a motor body, a bracket (300), and a sealing assembly; the motor body has a motor shaft (200); the bracket (300) has a shaft hole, and the bracket (300) is sleeved on the motor shaft (200) through the shaft hole, and the motor shaft (200) is used to pass through the bracket (300) and into the inner liner (100); the sealing assembly is sleeved on the motor shaft (200), and a sealed space is formed between the inner liner (100), the bracket (300), the motor shaft (200), and the sealing assembly; The sealed space is an annular space surrounding the motor shaft (200), and the left and right walls of the sealed space along the direction of the motor shaft (200) are the inner liner (100) and the bracket (300), respectively.

2. The DC motor according to claim 1, characterized in that, The sealing assembly includes a first seal (400), which is sleeved on the motor shaft (200) and installed between the bracket (300) and the inner liner (100). The first seal (400) is used to press against the inner liner (100).

3. The DC motor according to claim 2, characterized in that, The bracket (300) has a protrusion (310) surrounding the motor shaft (200) on the side facing the inner liner (100), and the first seal (400) has a first groove (410) surrounding the motor shaft (200) on the side facing the bracket (300), and the protrusion (310) and the first groove (410) are inserted into each other.

4. The DC motor according to claim 2, characterized in that, The first sealing element (400) is a sealing ring structure, and the end face of the first sealing element (400) facing the inner liner (100) is provided with a second groove (420) surrounding the motor shaft (200).

5. The DC motor according to claim 1, characterized in that, The sealing assembly includes a second seal (500), which is sleeved on the motor shaft (200) and located inside the shaft hole. The second seal (500) is interference-fitted with the hole wall of the shaft hole and the motor shaft (200).

6. The DC motor according to claim 5, characterized in that, The outer wall of the motor shaft (200) is provided with an annular third groove (210), and the second seal (500) is installed in the third groove (210).

7. The DC motor according to claim 5, characterized in that, The hole wall of the shaft hole of the bracket (300) is in the shape of annular steps, including multiple layers of annular steps, and the radius of the annular steps gradually increases along the direction close to the inner liner (100).

8. The DC motor according to claim 5, characterized in that, Along the direction close to the output end of the motor shaft (200), the shaft hole wall is provided with a first layer of annular steps, a second layer of annular steps and a third layer of annular steps, and the second seal (500) is provided on the second layer of annular steps.

9. The DC motor according to claim 8, characterized in that, The DC motor also includes a baffle (510), which is installed on the third layer of the annular step.

10. The DC motor according to claim 1, characterized in that, The sealing assembly includes a third sealing element, which is sleeved on the motor shaft (200) on the side of the bracket (300) away from the inner liner (100). The third sealing element is sealed to the bracket (300) while also achieving a dynamic sealing fit with the motor shaft (200).

11. The DC motor according to claim 10, characterized in that, The third sealing element is a sealed bearing (600).

12. The DC motor according to claim 1, characterized in that, The drive plate (700) is located on the side of the motor body away from the inner liner (100).

13. The DC motor according to claim 1, characterized in that, The drive plate (700) is disposed outside the cooking appliance, and the drive plate (700) is electrically connected to the motor body.

14. A control method for a DC motor, characterized in that, The method is applied to a DC motor as described in any one of claims 1-13; the DC motor includes a controller and PWM terminals for controlling speed and direction of rotation; the method includes: The controller detects whether the potential of the PWM terminal changes within a set time period; If not, the controller sends a rotation direction switching signal to the DC motor to cause the DC motor to switch its rotation direction.

15. The control method for a DC motor according to claim 14, characterized in that, The PWM terminal is used to output a PWM signal during the operation of the DC motor, and the method includes: The controller detects whether the PWM terminal outputs the PWM signal; If so, the controller sets the speed of the DC motor according to the PWM signal.

16. The control method for a DC motor according to claim 15, characterized in that, The PWM signal is a square wave, and the step of the controller setting the speed of the DC motor according to the PWM signal includes: The controller acquires the duty cycle of the square wave and controls the speed of the DC motor according to the duty cycle.

17. The control method for a DC motor according to claim 16, characterized in that, The set time is at least an order of magnitude higher than the pulse width of the PWM signal.

18. The control method for a DC motor according to claim 14, characterized in that, The DC motor further includes an FG terminal for control feedback signals, and the method includes: The controller obtains the speed and direction of rotation of the DC motor from the feedback of the FG terminal; The controller sets the speed and direction of rotation of the DC motor based on the obtained speed and direction of rotation of the DC motor.

19. A cooking utensil, characterized in that, The device includes an inner liner (100), fan blades, and a DC motor according to any one of claims 1 to 13. The DC motor is installed outside the inner liner (100), the fan blades are installed inside the inner liner (100), and the motor shaft (200) of the DC motor passes through the inner liner (100) and is connected to the fan blades for transmission.

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