Unloading control method for a compressor of a dryer

Abstract

This invention relates to the field of drying technology, specifically providing a compressor unloading control method for a dryer. The aim is to solve the problems of long unloading times during compressor unloading in existing dryers, leading to frost or even ice buildup on the external heat exchanger, and excessively high unloading frequencies causing performance degradation and reduced lifespan. To this end, the compressor unloading control method for a dryer of this invention includes: acquiring the compressor's operating current; comparing the compressor's operating current with the unloading current and the unloading exit current; and based on the comparison results, selectively controlling the dryer to enter different unloading modes or normal operation modes. This invention can select different unloading modes according to the compressor's operating current, reducing compressor unloading time compared to existing compressor unloading methods, improving the dryer's operational stability and baking quality, and extending its service life.

Description

Technical Field

[0001] This invention relates to the field of drying technology, and specifically provides a method for unloading a compressor in a dryer. Background Technology

[0002] Many people have a smoking habit. For tobacco to become the cigarettes consumers ultimately buy, it needs to undergo many processing steps. Among these, tobacco drying is an essential step in tobacco production. In the tobacco drying process, heat pump heating technology is generally used. This technology can improve the quality of tobacco leaf drying while reducing the difficulty of the drying process.

[0003] Current technology uses dryers to dry tobacco. During drying, the temperature inside the dryer's curing chamber can reach over 68°C in the later stages. When drying is carried out in the summer when the ambient temperature is high, the dryer is under heavy load: the internal and external heat exchangers operate at high pressure and temperature, easily leading to excessive compressor load. This results in increased compressor operating current, severe compressor overheating, and consequences such as compressor oil deterioration and coil burnout. To protect the compressor, compressor unloading is usually performed. Compressor unloading refers to gradually increasing the compressor operating current to the maximum allowable current value set in the program, then reducing the current to a certain value through unloading before resuming normal operation, and so on. However, for some dryers (such as the 420 tobacco dryer), this operation can cause frost or even ice formation on the external heat exchanger. Excessive unloading frequency can lead to decreased machine performance and reduced lifespan.

[0004] Therefore, the present invention needs to provide a new unloading control method for a compressor in a dryer to solve the above-mentioned technical problems. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned technical problems, namely, to solve the problems that the long unloading time of the compressor during unloading of existing dryers leads to easy frost or even ice formation on the external heat exchanger, and that excessive unloading frequency leads to decreased machine performance and reduced lifespan.

[0006] To this end, the present invention provides an unloading control method for a compressor of a dryer, the unloading control method comprising:

[0007] Obtain the operating current of the compressor;

[0008] Compare the operating current of the compressor with the unloading current and the unloading exit current.

[0009] Based on the comparison results of the compressor's operating current, unloading current, and unloading exit current, the dryer is selectively controlled to enter different unloading modes or normal operation modes.

[0010] In a specific embodiment of the above-mentioned unloading control method for the compressor of the dryer, the dryer includes a drying chamber and a heating chamber. A return air vent cover is installed between the drying chamber and the heating chamber. A circulating fan, an electric heater, a first exhaust fan, and an internal heat exchanger are installed sequentially from top to bottom inside the heating chamber. A second exhaust fan is installed outside the heating chamber. The second exhaust fan is located below the internal heat exchanger and is capable of exhausting the air inside the heating chamber to the outside. An external fan is installed outside the heating chamber.

[0011] The different uninstallation modes include pre-uninstallation mode, first-level uninstallation mode, and second-level uninstallation mode;

[0012] The pre-unloading mode is as follows: increase the opening of the expansion valve until the current difference between the unloading current and the operating current is greater than the preset current difference or the opening is adjusted to the maximum.

[0013] The first-level unloading mode is as follows: stop the pre-unloading mode, control the external fan and the electric heater to turn off, adjust the circulating fan to the highest level, and control the compressor to continue running;

[0014] The secondary unloading mode is as follows: control the circulating fan, the electric heater and the return air vent cover to close, control the external fan, the first exhaust fan and the second exhaust fan to start, and control the compressor to continue running.

[0015] With the above technical solution adopted, the present invention sets up a pre-unloading mode, a first-level unloading mode, and a second-level unloading mode. The dryer is selected to enter the appropriate unloading mode based on the comparison results of the compressor's operating current, unloading current, and unloading exit current. The unloading mode is diversified and can be adjusted in a timely manner according to the compressor's operating current. Compared with the compressor unloading method in the prior art, the compressor unloading time is reduced, while the stability of the dryer operation is improved, the baking quality is improved, and the service life is extended.

[0016] In a specific embodiment of the above-mentioned unloading control method for a compressor used in a dryer, the step of "selectively controlling the dryer to enter different unloading modes or normal operation modes based on the comparison results of the compressor's operating current, unloading current, and unloading exit current" specifically includes:

[0017] Based on the relationship between the difference between the unloading current and the operating current of the compressor and the preset current difference, the dryer is selectively controlled to enter the pre-unloading mode or the normal operation mode.

[0018] After entering the pre-unloading mode, based on the relationship between the operating current and the unloading current of the compressor, the dryer is selectively controlled to enter the first-level unloading mode or the normal operation mode.

[0019] After entering the first-level unloading mode and executing for a preset time, the dryer is selectively controlled to enter the second-level unloading mode or normal operation mode based on the relationship between the operating current of the compressor and the unloading exit current.

[0020] When the compressor is unloaded, the pre-unloading mode, the first-level unloading mode, and the second-level unloading mode are tried in sequence. Once one of the unloading modes meets the unloading requirements of the compressor, the process stops and the next unloading mode is entered. This method enables the compressor to find the most advantageous unloading method during unloading, which helps to reduce unloading time and frequency.

[0021] In a specific embodiment of the above-mentioned unloading control method for a compressor used in a dryer, the step of "selectively controlling the dryer to enter the pre-unloading mode or the normal operation mode based on the relationship between the current difference between the unloading current and the operating current of the compressor and the preset current difference" specifically includes:

[0022] If the current difference is less than or equal to the preset current difference, then the dryer is controlled to enter the pre-unloading mode; and / or

[0023] If the current difference is greater than the preset current difference, the dryer is controlled to maintain normal operation mode.

[0024] When the above technical solution is adopted, the expansion valve is connected between the internal heat exchanger and the external heat exchanger. After entering the pre-unloading mode, the opening of the expansion valve is increased, which can reduce the heat exchange performance of the external heat exchanger, which acts as an evaporator, and reduce the heating capacity of the dryer, thereby achieving the purpose of unloading. Since the pre-unloading mode can achieve the purpose of unloading the compressor, it is beneficial to reduce the number of times the compressor enters the subsequent unloading mode, that is, reduce the unloading frequency of the compressor using the subsequent unloading mode.

[0025] In a specific embodiment of the above-described unloading control method for the compressor of a dryer, after entering the pre-unloading mode, if the current difference becomes greater than the preset current difference, the dryer is controlled to maintain the pre-unloading mode.

[0026] In the specific implementation of the above-mentioned unloading control method for the compressor of the dryer, the step of "selectively controlling the dryer to enter the first-level unloading mode or the normal operation mode based on the relationship between the operating current and the unloading current of the compressor after entering the pre-unloading mode" specifically includes:

[0027] After entering the pre-unloading mode, if the compressor's operating current is greater than the unloading current, the dryer is controlled to enter the first-level unloading mode; and / or

[0028] After entering the pre-unloading mode, if the operating current of the compressor is less than the unloading current, the dryer is controlled to resume normal operation.

[0029] When the above technical solution is adopted, after the dryer enters the first-level unloading mode, the evaporation effect of the external heat exchanger, which acts as an evaporator, is weakened due to the shutdown of the external fan. The external heat exchanger is connected to the suction side of the compressor, which reduces the suction pressure. The reduced suction pressure also reduces the discharge pressure. The electric heater is located next to the internal heat exchanger. Turning off the electric heater and turning the circulating fan to the highest setting are both for cooling the internal heat exchanger. The internal heat exchanger is connected to the discharge side of the compressor, which reduces the heat exchange pressure of the internal heat exchanger while reducing the discharge pressure, thereby achieving the purpose of unloading the compressor.

[0030] In the specific implementation of the above-mentioned unloading control method for the compressor of a dryer, the step of "selectively controlling the dryer to enter the second-level unloading mode or normal operation mode based on the relationship between the operating current of the compressor and the unloading exit current after entering the first-level unloading mode and executing a preset time" specifically includes:

[0031] If the operating current of the compressor is greater than the unloading exit current, then the dryer is controlled to enter the secondary unloading mode; and / or

[0032] If the operating current of the compressor is less than the unloading exit current, the dryer is controlled to resume normal operation.

[0033] When the above technical solution is adopted, since the compressor is unloaded due to a large load, and the main reason for the large load is the excessively high temperature in the heating chamber where the internal heat exchanger is located, after entering the secondary unloading mode, the return air vent cover is closed, temporarily separating the drying chamber and the heating chamber, so that heat exchange does not occur between the drying chamber and the heating chamber. The first and second exhaust fans are turned on to reduce the temperature in the heating chamber where the internal heat exchanger is located, thereby achieving the purpose of rapidly reducing the load. Due to the addition of the first and second exhaust fans, the temperature in the heating chamber decreases quickly, which shortens the compressor unloading time. At the same time, after entering the primary unloading mode and executing the preset time, if the operating current is greater than the unloading current, the secondary unloading mode is executed, avoiding the phenomenon of frost or even ice formation on the external heat exchanger, which acts as the evaporator, caused by executing the primary unloading mode for a long time.

[0034] In a specific embodiment of the above-described unloading control method for a compressor used in a dryer, the unloading control method further includes:

[0035] When the operating current of the compressor is less than the unloading exit current, the first exhaust fan and the second exhaust fan are in the off state.

[0036] In a specific embodiment of the above-described unloading control method for a compressor used in a dryer, the unloading control method further includes:

[0037] The temperature of the inner coil in the internal heat exchanger and the temperature of the drying room in the drying room are obtained.

[0038] The temperature difference between the coil temperature and the oven temperature is obtained, and the temperature difference is compared with a preset temperature difference.

[0039] Compare the temperature of the coil with the temperature of the drying oven;

[0040] After entering the pre-unloading mode, the electric heater is selectively controlled to turn on based on the comparison between the temperature difference and the preset temperature difference.

[0041] After entering the secondary unloading mode, the electric heater is selectively controlled to turn on based on the comparison between the coil temperature and the oven temperature.

[0042] In a specific embodiment of the above-mentioned unloading control method for the compressor of a dryer, the step of "selectively controlling whether the electric heater is turned on based on the result of comparing the temperature difference value with the preset temperature difference value after entering the pre-unloading mode" specifically includes:

[0043] If the temperature difference is less than or equal to the preset temperature difference, then the electric heater is controlled to turn on; and / or

[0044] If the temperature difference is greater than the preset temperature difference, then the electric heater is controlled to turn off; and / or

[0045] The step of "selectively controlling whether the electric heater is turned on after entering the secondary unloading mode, based on the comparison between the coil temperature and the oven temperature" specifically includes:

[0046] If the temperature of the coil is lower than the temperature of the drying oven, then the electric heater is turned on; and / or

[0047] If the temperature of the coil is greater than or equal to the temperature of the drying oven, the electric heater is controlled to turn off.

[0048] When using the above technical solution, the present invention compares the coil temperature with the oven temperature during the pre-unloading mode and the secondary unloading mode to determine whether the electric heater is turned on, so as to avoid large fluctuations in the oven temperature and affect the baking quality. Attached Figure Description

[0049] The preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:

[0050] Figure 1 This is a schematic diagram of the drying chamber and heating room of the dryer provided by the present invention;

[0051] Figure 2 This is a flowchart of the main steps of the unloading control method for a compressor in a dryer provided by the present invention;

[0052] Figure 3 yes Figure 2 Detailed flowchart of step S3.

[0053] List of attached figures

[0054] 1. Baking room; 2. Heating chamber; 3. Air inlet; 4. Circulating fan; 5. Electric heater; 6. First exhaust fan; 7. Internal heat exchanger; 8. Second exhaust fan; 9. Return air outlet; 10. Return air outlet cover. Detailed Implementation

[0055] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0056] It should be noted that in the description of this invention, terms such as "upper," "lower," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the relevant devices or elements must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, ordinal numbers such as "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0057] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation" and "connection" 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. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] First refer to Figure 1 This invention provides a dryer comprising a drying chamber 1 and a heating chamber 2. An air inlet 3 and a return air inlet 9 are provided between the drying chamber 1 and the heating chamber 2. Air from the heating chamber 2 enters the drying chamber 1 through the air inlet 3 and then returns to the heating chamber 2 through the return air inlet 9. A return air inlet cover 10 is installed at the return air inlet 9 to open or close it. Inside the heating chamber 2, from top to bottom, a circulating fan 4, an electric heater 5, a first exhaust fan 6, and an internal heat exchanger 7 are installed sequentially. A second exhaust fan 8 is installed outside the heating chamber 2, located below the internal heat exchanger 7, and is capable of exhausting air from the heating chamber 2 to the outside. An external heat exchanger and an external fan are installed outside the heating chamber 2, with the external fan used to accelerate airflow around the external heat exchanger. An expansion valve is connected between the internal heat exchanger 7 and the external heat exchanger.

[0059] It should be noted that since the return air vent cover, external heat exchanger, internal heat exchanger, electric heater and circulating fan are existing technologies and are known to those skilled in the art, their specific structures will not be described in detail here.

[0060] See below. Figure 2 The present invention also provides an unloading control method for a compressor of a dryer, the unloading control method comprising:

[0061] S1, obtain the operating current of the compressor;

[0062] S2, compare the operating current of the compressor with the unloading current and the unloading exit current;

[0063] S3, based on the comparison results of the compressor's operating current, unloading current and unloading exit current, selectively controls the dryer to enter different unloading modes or normal operation modes.

[0064] In one embodiment, different uninstallation modes include pre-uninstallation mode, first-level uninstallation mode, and second-level uninstallation mode;

[0065] The pre-unloading mode is as follows: increase the opening of the expansion valve until the current difference between the unloading current and the operating current is greater than the preset current difference or the opening is adjusted to the maximum.

[0066] The first-level unloading mode is as follows: stop the pre-unloading mode, control the external fan and electric heater to shut down, adjust the circulating fan to the highest level, and control the compressor to continue running;

[0067] The secondary unloading mode is as follows: control the circulating fan, electric heater and return air vent cover to close, control the external fan, first row fan and second row fan to open, and control the compressor to continue running.

[0068] It should be noted that both the compressor's unloading current and unloading exit current are pre-stored in the dryer's memory. The compressor's unloading current refers to the current at which the compressor's operating current reaches the unloading current, at which point the compressor unloads. The unloading exit current refers to the current at which the compressor's operating current decreases to the unloading exit current, at which point the compressor exits the unloading mode.

[0069] In addition, in the pre-unloading mode, the specific operation of increasing the opening of the expansion valve is to gradually increase it according to the set interval time and the set opening value based on the current opening. For example, the set interval time is 1 minute and the set opening value is 50 pls. That is, every 1 minute, the opening of the expansion valve is increased by 50 pls until the maximum opening is increased or the current difference between the unloading current and the operating current is greater than the preset current difference.

[0070] See Figure 3 In one embodiment, step S3, "selectively controlling the dryer to enter different unloading modes or normal operation modes based on the comparison results of the compressor's operating current, unloading current, and unloading exit current," specifically includes:

[0071] S31, based on the relationship between the difference between the unloading current and the operating current of the compressor and the preset current difference, selectively controls the dryer to enter the pre-unloading mode or the normal operation mode.

[0072] S32, after entering the pre-unloading mode, selectively controls the dryer to enter the first-level unloading mode or the normal operation mode based on the relationship between the compressor's operating current and the unloading current.

[0073] S33, after entering the first-level unloading mode and executing the preset time, selectively controls the dryer to enter the second-level unloading mode or normal operation mode based on the relationship between the compressor's operating current and the unloading exit current.

[0074] When the compressor is unloaded, the pre-unloading mode, the first-level unloading mode, and the second-level unloading mode are tried in sequence. Once one of the unloading modes meets the unloading requirements of the compressor, the process stops and proceeds to the next unloading mode. This method allows the compressor to find the most advantageous unloading method, which helps to reduce unloading time and frequency.

[0075] Continue reading Figure 3 In one embodiment, step S31, "selectively controlling the dryer to enter either a pre-unloading mode or a normal operation mode based on the relationship between the difference between the compressor's unloading current and operating current and a preset current difference," specifically includes:

[0076] S311, if the current difference is less than or equal to the preset current difference, control the dryer to enter the pre-unloading mode;

[0077] S312, if the current difference is greater than the preset current difference, the dryer will be controlled to maintain normal operation mode.

[0078] Since the expansion valve is connected between the internal and external heat exchangers, entering the pre-unloading mode increases the valve's opening, thereby increasing the refrigerant flow from the internal to the external heat exchanger. This raises the evaporation pressure and temperature of the refrigerant entering the external heat exchanger, reducing steam superheat and consequently decreasing the heat exchange performance of the external heat exchanger (acting as an evaporator). This reduces the dryer's heating capacity, achieving the unloading purpose. Because the pre-unloading mode effectively unloads the compressor, it reduces the number of times the compressor enters subsequent unloading phases, thus lowering the frequency of subsequent unloading.

[0079] It should be noted that the present invention does not limit the specific value of the preset current difference. The preset current difference is set according to the working requirements and baking conditions of different dryers.

[0080] Furthermore, after entering the pre-unloading mode, if the current difference becomes greater than the preset current difference, the dryer is controlled to maintain the pre-unloading mode.

[0081] In the above embodiment, since the operating current of the compressor is reduced by adjusting the opening of the expansion valve, it is sufficient to maintain the opening of the expansion valve, that is, to maintain the pre-unloading mode.

[0082] Continue reading Figure 3 In one embodiment, step S32, "after entering the pre-unloading mode, selectively controlling the dryer to enter the first-level unloading mode or the normal operation mode based on the relationship between the compressor's operating current and the unloading current," specifically includes:

[0083] S321: After entering the pre-unloading mode, if the compressor's operating current is greater than the unloading current, the dryer will be controlled to enter the first-level unloading mode.

[0084] S322: After entering the pre-unloading mode, if the compressor's operating current is less than the unloading current, the dryer will be controlled to return to normal operation mode.

[0085] In the above embodiment, after the dryer enters the first-level unloading mode, the evaporation effect of the external heat exchanger, which acts as an evaporator, is weakened due to the shutdown of the external fan. The external heat exchanger is connected to the suction side of the compressor, which reduces the suction pressure. The reduced suction pressure also reduces the discharge pressure. The electric heater is located next to the internal heat exchanger. Turning off the electric heater and turning the circulating fan to the highest setting are both for cooling the internal heat exchanger. The internal heat exchanger is connected to the discharge side of the compressor, which reduces the heat exchange pressure of the internal heat exchanger while reducing the discharge pressure, thereby achieving the purpose of unloading the compressor.

[0086] Continue reading Figure 3 In one embodiment, step S33, "after entering the first-level unloading mode and executing a preset time, selectively controlling the dryer to enter the second-level unloading mode or the normal operation mode based on the relationship between the compressor's operating current and the unloading exit current," specifically includes:

[0087] S331, if the compressor's operating current is greater than the unloading exit current, the dryer is controlled to enter the secondary unloading mode.

[0088] S332: If the compressor's operating current is less than the unloading exit current, the dryer will be controlled to resume normal operation.

[0089] In the above embodiment, since the compressor is unloaded due to a large load, and the main reason for the large load is the excessively high temperature in the heating chamber where the internal heat exchanger is located, after entering the secondary unloading mode, the return air vent cover is closed, temporarily separating the drying chamber and the heating chamber, so that heat exchange does not occur between the drying chamber and the heating chamber. The first and second exhaust fans are turned on to reduce the temperature in the heating chamber where the internal heat exchanger is located, thereby achieving the purpose of rapidly reducing the load. Due to the addition of the first and second exhaust fans, the temperature in the heating chamber decreases quickly, which shortens the compressor unloading time. At the same time, after entering the primary unloading mode and executing the preset time, if the operating current is greater than the unloading current, the secondary unloading mode is executed, avoiding the phenomenon of frost or even ice formation on the external heat exchanger, which acts as the evaporator, caused by executing the primary unloading mode for a long time.

[0090] Furthermore, the unloading control method also includes: when the compressor's operating current is less than the unloading exit current, the first and second exhaust fans are in a closed state. When the operating current is less than the unloading exit current, it means that unloading is not required, i.e., the two-stage unloading mode does not need to be executed. During normal operation of the dryer, the first and second exhaust fans need to be turned off to ensure normal baking operation.

[0091] In addition, the uninstallation control method also includes:

[0092] Obtain the coil temperature of the internal heat exchanger and the oven temperature in the oven.

[0093] Obtain the temperature difference between the coil temperature and the oven temperature, and compare the temperature difference with the preset temperature difference.

[0094] Compare the coil temperature with the oven temperature;

[0095] After entering the pre-unloading mode, the electric heater is selectively controlled to turn on based on the comparison between the temperature difference and the preset temperature difference.

[0096] After entering the secondary unloading mode, the electric heater is selectively turned on based on the comparison between the coil temperature and the oven temperature.

[0097] Specifically, a temperature sensor is installed on the inner coil to detect its temperature. The drying oven is equipped with a dry bulb temperature sensor to detect the dry bulb temperature. The temperature information of the inner coil is obtained through the temperature sensor, and the temperature information of the drying oven is obtained through the dry bulb temperature sensor.

[0098] In one embodiment, the step of "selectively controlling whether the electric heater is turned on based on the comparison between the temperature difference value and the preset temperature difference value after entering the pre-unloading mode" specifically includes:

[0099] If the temperature difference is less than or equal to the preset temperature difference, the electric heater will be turned on.

[0100] If the temperature difference exceeds the preset temperature difference, the electric heater will be turned off.

[0101] It should be noted that this invention does not limit the specific value of the preset temperature difference, but designs it according to the usage requirements and baking conditions of the dryer. For example, the preset temperature difference may be 10℃. Taking a baking oven temperature of 65℃ as an example, if the temperature difference between the coil temperature and 65℃ is less than or equal to 10℃, the electric heater is turned on; if the temperature difference between the coil temperature and 65℃ is greater than 10℃, the electric heater is turned off.

[0102] In one embodiment, the step of "selectively controlling whether the electric heater is turned on based on the comparison between the coil temperature and the oven temperature after entering the secondary unloading mode" specifically includes:

[0103] If the coil temperature is lower than the oven temperature, the electric heater will be turned on.

[0104] If the coil temperature is greater than or equal to the oven temperature, the electric heater will be turned off.

[0105] Taking a drying oven temperature of 65℃ as an example, if the coil temperature is less than 65℃, the electric heater will be turned on; if the coil temperature is greater than or equal to 65℃, the electric heater will be turned off.

[0106] In the above embodiments, the coil temperature and the oven temperature are compared when the pre-unloading mode and the secondary unloading mode are executed to determine whether the electric heater is turned on, so as to avoid large fluctuations in the oven temperature and affect the baking quality.

[0107] In addition, the dryer also includes a controller configured to perform the unloading control method for the compressor of the dryer described in any of the above technical solutions.

[0108] In the above embodiments and various extended implementations, the present invention provides a pre-unloading mode, a first-level unloading mode, and a second-level unloading mode. The dryer is selected to enter a suitable unloading mode based on a comparison of the compressor's operating current, unloading current, and unloading exit current. The unloading modes are diversified, and the unloading method progresses step-by-step according to set conditions. This allows the present invention to adjust the unloading mode in a timely manner based on the compressor's operating current. Compared to the compressor unloading method in the prior art, this reduces the compressor unloading time. During unloading, a pre-unloading mode is first performed, and subsequent unloading is not performed if the compressor's operating current requirements are met. This helps reduce the unloading frequency, improves the stability of the dryer's operation, enhances the baking quality, and extends its service life.

[0109] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for unloading a compressor in a dryer, characterized in that, The uninstallation control method includes: Obtain the operating current of the compressor; Compare the operating current of the compressor with the unloading current and the unloading exit current. Based on the comparison results of the compressor's operating current, unloading current, and unloading exit current, the dryer is selectively controlled to enter different unloading modes or normal operation modes. The dryer includes a drying chamber and a heating chamber. A return air vent cover is installed between the drying chamber and the heating chamber. A circulating fan, an electric heater, a first exhaust fan, and an internal heat exchanger are installed in the heating chamber from top to bottom. A second exhaust fan is installed on the outside of the heating chamber. The second exhaust fan is located below the internal heat exchanger and can exhaust the air in the heating chamber to the outside. An external fan is installed on the outside of the heating chamber. An expansion valve is connected between the internal heat exchanger and the external heat exchanger. The different uninstallation modes include pre-uninstallation mode, first-level uninstallation mode, and second-level uninstallation mode; The pre-unloading mode is as follows: increase the opening of the expansion valve until the current difference between the unloading current and the operating current is greater than the preset current difference or the opening is adjusted to the maximum. The first-level unloading mode is as follows: stop the pre-unloading mode, control the external fan and the electric heater to turn off, adjust the circulating fan to the highest level, and control the compressor to continue running; The secondary unloading mode is as follows: control the circulating fan, the electric heater and the return air vent cover to close, control the external fan, the first exhaust fan and the second exhaust fan to start, and control the compressor to continue running.

2. The unloading control method for a compressor in a dryer according to claim 1, characterized in that, The step of "selectively controlling the dryer to enter different unloading modes or normal operation modes based on the comparison results of the compressor's operating current, unloading current, and unloading exit current" specifically includes: Based on the relationship between the difference between the unloading current and the operating current of the compressor and the preset current difference, the dryer is selectively controlled to enter the pre-unloading mode or the normal operation mode. After entering the pre-unloading mode, based on the relationship between the operating current and the unloading current of the compressor, the dryer is selectively controlled to enter the first-level unloading mode or the normal operation mode. After entering the first-level unloading mode and executing for a preset time, the dryer is selectively controlled to enter the second-level unloading mode or normal operation mode based on the relationship between the operating current of the compressor and the unloading exit current.

3. The unloading control method for a compressor in a dryer according to claim 2, characterized in that, The step of "selectively controlling the dryer to enter the pre-unloading mode or normal operation mode based on the relationship between the current difference between the unloading current and the operating current of the compressor and the preset current difference" specifically includes: If the current difference is less than or equal to the preset current difference, then the dryer is controlled to enter the pre-unloading mode; and / or If the current difference is greater than the preset current difference, the dryer is controlled to maintain normal operation mode.

4. The unloading control method for a compressor in a dryer according to claim 3, characterized in that, After entering the pre-unloading mode, if the current difference becomes greater than the preset current difference, the dryer is controlled to maintain the pre-unloading mode.

5. The unloading control method for a compressor in a dryer according to claim 2, characterized in that, The step of "selectively controlling the dryer to enter the first-level unloading mode or the normal operation mode after entering the pre-unloading mode, based on the relationship between the operating current and the unloading current of the compressor" specifically includes: After entering the pre-unloading mode, if the compressor's operating current is greater than the unloading current, the dryer is controlled to enter the first-level unloading mode; and / or After entering the pre-unloading mode, if the operating current of the compressor is less than the unloading current, the dryer is controlled to resume normal operation.

6. The unloading control method for a compressor of a dryer according to any one of claims 2-5, characterized in that, The step of "selectively controlling the dryer to enter the second-level unloading mode or normal operation mode after entering the first-level unloading mode and executing the preset time, based on the relationship between the operating current of the compressor and the unloading exit current" specifically includes: If the operating current of the compressor is greater than the unloading exit current, then the dryer is controlled to enter the secondary unloading mode; and / or If the operating current of the compressor is less than the unloading exit current, the dryer is controlled to resume normal operation.

7. The unloading control method for a compressor in a dryer according to claim 6, characterized in that, The uninstallation control method further includes: When the operating current of the compressor is less than the unloading exit current, the first exhaust fan and the second exhaust fan are controlled to be in the off state.

8. The unloading control method for a compressor of a dryer according to any one of claims 2-5, characterized in that, The uninstallation control method further includes: The temperature of the inner coil in the internal heat exchanger and the temperature of the drying room in the drying room are obtained. The temperature difference between the coil temperature and the oven temperature is obtained, and the temperature difference is compared with the preset temperature difference. Compare the temperature of the coil with the temperature of the drying oven; After entering the pre-unloading mode, the electric heater is selectively controlled to turn on based on the comparison between the temperature difference and the preset temperature difference. After entering the secondary unloading mode, the electric heater is selectively controlled to turn on based on the comparison between the coil temperature and the oven temperature.

9. The unloading control method for a compressor in a dryer according to claim 8, characterized in that, The step of "selectively controlling whether the electric heater is turned on after entering the pre-unloading mode, based on the comparison between the temperature difference and the preset temperature difference" specifically includes: If the temperature difference is less than or equal to the preset temperature difference, the electric heater is turned on; and / or, if the temperature difference is greater than the preset temperature difference, the electric heater is turned off. And / or The step of "selectively controlling whether the electric heater is turned on after entering the secondary unloading mode, based on the comparison between the coil temperature and the oven temperature" specifically includes: If the coil temperature is lower than the oven temperature, the electric heater is turned on; and / or, if the coil temperature is greater than or equal to the oven temperature, the electric heater is turned off.

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