Oil return control method, medium and control device for truck air conditioner

Abstract

The present invention relates to the technical field of automotive air conditioning, and in particular to an oil return control method for a truck air conditioner. The present application aims to solve the problem of how to ensure the oil return effect of a truck air conditioner. To this end, the truck air conditioner of the present application includes an outdoor unit and an indoor unit, the outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a throttling element, the indoor unit includes an indoor heat exchanger and an indoor fan, and the compressor is vertically installed on the top or back of the truck cab. The oil return control method includes: obtaining the operating frequency of the compressor and the air outlet temperature of the indoor unit; comparing the operating frequency with the preset frequency threshold, and the air outlet temperature with the preset temperature threshold; based on the comparison result, selectively performing an oil return operation on the compressor. The oil return control method of the present application can ensure the oil return effect of the truck air conditioner, avoid compressor failure, and improve the operating stability of the truck air conditioner.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile air conditioners, and in particular to an oil return control method for a truck air conditioner. Background Art

[0002] In order to improve the working environment of the driver, large trucks are now generally equipped with split air conditioners. The outdoor unit of the split air conditioner is usually installed on the top or back of the cab, and the outdoor unit is usually higher than the indoor unit in vertical height.

[0003] When a truck or the road conditions are bad, such as when driving uphill or on a bumpy road, the truck body will tilt or bump, and the compressor will also tilt. Compressors are generally installed vertically. Once tilted, the crankshaft will not be able to absorb the refrigerant oil, which will cause dry friction between the components inside the compressor, which can easily cause the compressor to jam or the motor to burn out. Therefore, it is crucial to ensure that the refrigerant oil in the system returns to the compressor in a timely manner.

[0004] Accordingly, this field requires a new technical solution to solve the above problems. Summary of the Invention

[0005] In order to solve at least one of the above problems in the prior art, that is, to solve the problem of how to ensure the oil return effect of the truck air conditioner, the present application provides an oil return control method for a truck air conditioner, wherein the truck air conditioner includes an outdoor unit and an indoor unit, the outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a throttling element, the indoor unit includes an indoor heat exchanger and an indoor fan, and the compressor is vertically installed on the top or back of the truck cab.

[0006] The oil return control method includes:

[0007] Obtaining the operating frequency of the compressor and the air outlet temperature of the indoor unit;

[0008] Comparing the operating frequency with a preset frequency threshold, and comparing the air outlet temperature with a preset temperature threshold;

[0009] Based on the comparison result, an oil return operation is selectively performed on the compressor.

[0010] In the preferred technical solution of the above-mentioned oil return control method for a truck air conditioner, the step of "selectively performing an oil return operation on the compressor based on the comparison result" further includes:

[0011] If the operating frequency is less than or equal to the preset frequency threshold, the air outlet temperature is greater than the preset temperature threshold, and the duration of the above state exceeds a first preset time, the following oil return operation is performed on the compressor:

[0012] Controlling the compressor to increase the frequency to a first oil return frequency;

[0013] Wherein, the first oil return frequency is greater than the preset frequency threshold.

[0014] In the preferred technical solution of the above-mentioned oil return control method for truck air conditioners, the oil return control method further comprises:

[0015] After the compressor operates at the first oil return frequency for a second preset time period, the compressor is controlled to reduce the frequency to the operating frequency and continue to operate.

[0016] In the preferred technical solution of the above-mentioned oil return control method for a truck air conditioner, the step of "selectively performing an oil return operation on the compressor based on the comparison result" further includes:

[0017] If the operating frequency is less than or equal to the preset frequency threshold, the air outlet temperature is less than or equal to the preset temperature threshold, and the duration of the above state exceeds a third preset time, the following oil return operation is performed on the compressor:

[0018] Controlling the compressor to increase the frequency to the second oil return frequency and controlling the internal fan to operate at the maximum speed;

[0019] Wherein, the second oil return frequency is greater than the preset frequency threshold.

[0020] In the preferred technical solution of the above-mentioned oil return control method for truck air conditioners, the oil return control method further comprises:

[0021] After the compressor runs at the second oil return frequency for a fourth preset time, the compressor is controlled to reduce the frequency to the operating frequency and continue to run, and the speed of the internal fan is controlled to return to the speed before the oil return operation.

[0022] In the preferred technical solution of the above-mentioned oil return control method for a truck air conditioner, the step of "selectively performing an oil return operation on the compressor based on the comparison result" further includes:

[0023] If the operating frequency is greater than the preset frequency threshold, the air outlet temperature is less than or equal to the preset temperature threshold, and the duration of the above state exceeds a fifth preset time, the following oil return operation is performed on the compressor:

[0024] The rotational speed of the internal fan is controlled to increase at a first preset acceleration until it reaches a maximum rotational speed.

[0025] In the preferred technical solution of the above-mentioned oil return control method for truck air conditioners, the oil return control method further comprises:

[0026] When the rotation speed of the internal fan rises to the maximum rotation speed, the rotation speed of the internal fan is controlled to decrease at a second preset acceleration until it decreases to the rotation speed before the oil return operation.

[0027] In the preferred technical solution of the above-mentioned oil return control method for a truck air conditioner, the step of "selectively performing an oil return operation on the compressor based on the comparison result" further includes:

[0028] If the operating frequency is greater than the preset frequency threshold, and the air outlet temperature is greater than the preset temperature threshold, the oil return operation is not performed on the compressor.

[0029] The present application also provides a computer-readable storage medium storing a plurality of program codes, wherein the program codes are suitable for being loaded and run by a processor to execute the oil return control method for a truck air conditioner according to any one of the above technical solutions.

[0030] The present application also provides a control device, comprising:

[0031] processor;

[0032] A memory, wherein the memory is suitable for storing a plurality of program codes, wherein the program codes are suitable for being loaded and run by the processor to execute the oil return control method for the truck air conditioner according to any one of the above technical solutions.

[0033] It should be noted that in the preferred technical solution of the present application, the truck air conditioner includes an outdoor unit and an indoor unit, the outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a throttling element, the indoor unit includes an indoor heat exchanger and an indoor fan, and the compressor is vertically installed on the top or back of the truck cab. The oil return control method includes: obtaining the operating frequency of the compressor and the air outlet temperature of the indoor unit; comparing the operating frequency with the preset frequency threshold, and the air outlet temperature with the preset temperature threshold; based on the comparison result, selectively performing an oil return operation on the compressor.

[0034] By comparing the operating frequency with the preset frequency threshold, as well as the air outlet temperature with the preset temperature threshold, and performing oil return operation on the compressor based on the comparison results, the oil return control method of the present application can ensure the oil return effect of the truck air conditioner, avoid compressor failure, and improve the operating stability of the truck air conditioner.

[0035] Furthermore, by adopting different oil return operations in different situations, the oil return control method of the present application can also ensure the consistency of the oil return effect under any working conditions, thereby improving the operating stability of the truck air conditioner. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following describes the oil return control method, medium, and control device of the truck air conditioner of the present application with reference to the accompanying drawings.

[0037] Figure 1 This is a flow chart of the oil return control method for the truck air conditioner of the present application;

[0038] Figure 2 This is a logic diagram of the oil return control method of the truck air conditioner of this application. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present application are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are merely used to explain the technical principles of the present application and are not intended to limit the scope of protection of the present application. For example, although the detailed steps of the method of the present application are described in detail below, those skilled in the art may combine, split, and change the order of the following steps without departing from the basic principles of the present application. The modified technical solution does not change the basic concept of the present application and therefore falls within the scope of protection of the present application.

[0040] First refer to Figure 1 , the oil return control method of the truck air conditioner of the present application is described. Among them, Figure 1 This is a flow chart of the oil return control method for the truck air conditioner of the present application.

[0041] like Figure 1 As shown, in order to solve the problem of how to ensure the oil return effect of a truck air conditioner, this application provides an oil return control method for a truck air conditioner, wherein the truck air conditioner includes an outdoor unit and an indoor unit, the outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a throttling element, and the indoor unit includes an indoor heat exchanger and an indoor fan. The compressor is vertically installed on the top or back of the truck cab, and the compressor, outdoor heat exchanger, throttling element, and indoor heat exchanger are connected by a refrigerant pipeline to form a refrigerant circulation. The oil return control method includes:

[0042] S101. Obtain the operating frequency of the compressor and the outlet air temperature of the indoor unit. For example, the outlet air temperature of the indoor unit is obtained by a temperature sensor provided at the air outlet of the indoor unit, and the operating frequency of the compressor is obtained by a computer board or a frequency detection electrical component of the compressor.

[0043] S103. Compare the operating frequency with a preset frequency threshold, and the outlet air temperature with a preset temperature threshold. For example, after obtaining the operating frequency of the compressor and the outlet air temperature of the indoor unit, compare the operating frequency with the preset frequency threshold, and the outlet air temperature with the preset temperature threshold, by calculating a difference or ratio. The order of comparison is not limited in this application; the comparisons may be performed sequentially or simultaneously. The preset frequency threshold and the preset temperature threshold are pre-set and stored in the air conditioner.

[0044] S105. Based on the comparison results, selectively perform an oil return operation on the compressor. For example, when the compressor frequency is greater than a preset frequency threshold and the outlet air temperature is greater than a preset temperature threshold, the fluidity of the refrigeration oil is good, and therefore no oil return operation is required. When the outlet air temperature is lower than a certain value due to the high temperature, it is necessary to increase the evaporation temperature to reduce the oil viscosity and improve its fluidity.

[0045] When the compressor's operating frequency is greater than the preset frequency threshold and the air outlet temperature is greater than the preset temperature threshold, it indicates that the air conditioning system's internal circulation pressure is high, and the evaporation temperature of the refrigerant in the indoor heat exchanger is also high. This indicates that the refrigeration oil has good fluidity and high oil return efficiency, so there is no need to perform an oil return operation. When the compressor's operating frequency is less than or equal to the preset frequency threshold and the air outlet temperature is less than or equal to the preset temperature threshold, it indicates that the refrigeration oil has poor fluidity and low oil return efficiency, and an oil return operation is required to prevent oil shortage in the compressor.

[0046] It can be seen that by comparing the operating frequency with the preset frequency threshold, as well as the air outlet temperature with the preset temperature threshold, and performing the oil return operation on the compressor based on the comparison results, the oil return control method of the present application can ensure the oil return effect of the truck air conditioner, avoid compressor failure, and improve the operating stability of the truck air conditioner.

[0047] The preferred implementation of the oil return control method for the truck air conditioner of the present application is introduced below.

[0048] In a preferred embodiment, the step of “selectively performing an oil return operation on the compressor based on the comparison result” further includes:

[0049] (1) If the operating frequency is less than or equal to the preset frequency threshold, the air outlet temperature is greater than the preset temperature threshold, and the duration of the above state exceeds a first preset time, the following oil return operation is performed on the compressor: the compressor is controlled to increase the frequency to the first oil return frequency; after the compressor runs at the first oil return frequency for a second preset time, the compressor is controlled to reduce the frequency to the operating frequency and continue to run. The first oil return frequency is greater than the preset frequency threshold;

[0050] Specifically, the inventors' research has found that the lower the compressor operating frequency, the slower the refrigerant circulation. This means that the refrigeration oil mixes with the refrigerant and returns to the compressor more slowly. Refrigeration oil is highly viscous, and the resistance of the internally threaded copper tubes in the indoor heat exchanger can cause the refrigeration oil to remain on the inner wall of the tubes. The lower the outlet air temperature and the lower the evaporation temperature of the indoor heat exchanger, the greater the oil viscosity and the greater the flow resistance. Furthermore, the compressor frequency has a greater impact on the refrigeration oil than the other two.

[0051] Therefore, if the operating frequency is less than or equal to the preset frequency threshold, and the outlet air temperature is greater than the preset temperature threshold, and the operating frequency is less than or equal to the preset frequency threshold and the outlet air temperature is greater than the preset temperature threshold, and the state of the operating frequency being less than or equal to the preset frequency threshold and the outlet air temperature being greater than the preset temperature threshold persists for a first preset time period, the oil return effect of the compressor will deteriorate, and the compressor needs to be returned to oil. The first preset time period can be any value between 20 and 40 minutes, and is preferably 30 minutes in this application.

[0052] In this situation, the compressor performs the following oil return operation: the compressor is controlled to increase its frequency to a first oil return frequency, preferably the maximum frequency of the compressor. At this frequency, the truck air conditioner's system circulation pressure is at its maximum, and the refrigeration oil rapidly flows back into the compressor along with the refrigerant. After the compressor has been running at the maximum frequency for a second preset duration, the refrigeration oil return effect has been achieved. At this point, the compressor is controlled to decrease its frequency to the previous operating frequency and continue operation. The second preset duration can be any value between 1 and 5 minutes, preferably 3 minutes in this application.

[0053] (2) If the operating frequency is less than or equal to the preset frequency threshold, the outlet air temperature is less than or equal to the preset temperature threshold, and the duration of the above state exceeds a third preset time, the following oil return operation is performed on the compressor: the compressor is controlled to increase the frequency to the second oil return frequency and the internal fan is controlled to operate at the maximum speed; after the compressor operates at the second oil return frequency for a fourth preset time, the compressor is controlled to decrease the frequency to the operating frequency and continue to operate, and the speed of the internal fan is controlled to return to the speed before the oil return operation. The second oil return frequency is greater than the preset frequency threshold.

[0054] Specifically, when the operating frequency is less than or equal to a preset frequency threshold, the outlet air temperature is also less than or equal to a preset temperature threshold, and the operating frequency is less than or equal to the preset frequency threshold and the outlet air temperature is less than or equal to the preset temperature threshold for a third preset duration, the compressor's oil return effect is at its worst, and oil return operation needs to be performed on the compressor as soon as possible. The second preset duration can be any value between 10 and 30 minutes, and preferably, 20 minutes is used in this application.

[0055] In the above case, the following oil return operation is performed on the compressor: the compressor is controlled to increase the frequency to the second oil return frequency, and the internal fan is controlled to run at the maximum speed. The second oil return frequency preferably adopts the maximum frequency of the compressor. When running at this frequency, the system circulation pressure of the truck air conditioner is the largest, and when the internal fan runs at the maximum speed, it can speed up the heat exchange efficiency of the indoor heat exchanger, increase the temperature of the refrigerant in the indoor heat exchanger, and thus increase the fluidity of the refrigeration oil. In this way, the refrigeration oil can quickly flow back to the compressor with the refrigerant. After the compressor runs at the maximum frequency for the fourth preset time, the refrigeration oil return effect has been achieved. At this time, the compressor is controlled to reduce the frequency to the previous operating frequency and continue to run, and the internal fan is controlled to resume the previous speed and continue to run. Among them, the fourth preset time can be any value in the range of 1-5 minutes, and preferably 3 minutes is taken in this application.

[0056] (3) If the operating frequency is greater than the preset frequency threshold, the air outlet temperature is less than or equal to the preset temperature threshold, and the duration of the above state exceeds the fifth preset time, the following oil return operation is performed on the compressor: the speed of the internal fan is controlled to increase at a first preset acceleration until it reaches the maximum speed; when the speed of the internal fan increases to the maximum speed, the speed of the internal fan is controlled to decrease at a second preset acceleration until it decreases to the speed before the oil return operation.

[0057] Specifically, if the operating frequency is greater than a preset frequency threshold, the outlet air temperature is less than or equal to a preset temperature threshold, and the operating frequency is greater than the preset frequency threshold and the outlet air temperature is less than or equal to the preset temperature threshold for a fifth preset duration, the compressor's oil return effect is slightly insufficient, which may pose a hidden danger. In this case, the compressor needs to perform an oil return operation. The fifth preset duration can be any value between 50 and 70 minutes, and preferably 60 minutes in this application.

[0058] In this situation, the compressor performs the following oil return operation: the internal fan speed is controlled to increase at a first preset acceleration rate, where the first preset acceleration rate can increase by 50r every 15 minutes. Under this control mode, the heat exchange efficiency of the indoor heat exchanger gradually increases, and the refrigeration oil in the indoor heat exchanger quickly flows back to the compressor along with the refrigerant. When the internal fan speed increases to the maximum speed, the refrigeration oil return effect has been achieved. At this time, the internal fan speed is controlled to decrease at a second preset acceleration rate until it reaches the speed before the oil return operation. The second preset acceleration rate can also increase by 50r every 15 minutes.

[0059] Of course, the first preset acceleration and the second preset acceleration are not limited thereto, and those skilled in the art may adjust them. For example, the two may be set to be equal or unequal.

[0060] (4) If the operating frequency is greater than the preset frequency threshold and the air outlet temperature is greater than the preset temperature threshold, the oil return operation is not performed on the compressor.

[0061] Specifically, when the operating frequency is greater than the preset frequency threshold and the air outlet temperature is greater than the preset temperature threshold, the circulation pressure of the air-conditioning system is sufficient and the fluidity of the refrigeration oil in the indoor heat exchanger is also good. In other words, the oil return effect of the compressor is guaranteed. Therefore, the oil return operation of the compressor is not performed at this time, and the truck air conditioner can be controlled to maintain the current operating mode.

[0062] By adopting different oil return operations in different situations, the oil return control method of the present application can also ensure the consistency of the oil return effect under any working conditions, thereby improving the operating stability of the truck air conditioner.

[0063] It should be noted that the above preferred embodiments are only used to illustrate the principles of this application and are not intended to limit the scope of protection of this application. Without departing from the principles of this application, those skilled in the art may adjust the above settings so that this application can be applied to more specific application scenarios.

[0064] For example, in an alternative embodiment, although the above embodiments describe several specific control methods for oil return operations, the specific form of oil return operation is not unique. Those skilled in the art may adjust the oil return method, provided that rapid oil return can be achieved, and such adjustments do not deviate from the principles of this application. For example, those skilled in the art may also improve oil return efficiency by simply controlling the frequency of the compressor, or by simply controlling the speed of the internal fan. Of course, the oil return effect of such a single control method is inferior to the oil return method combining the two methods described in this application.

[0065] For example, in another alternative embodiment, although the operating status of the compressor and / or the internal fan is adjusted back to the state before the oil return operation after each oil return operation in the above embodiment, this adjustment method is not necessary, and technical personnel in this field can choose whether to perform such adjustment based on the specific application scenario.

[0066] For example, in another alternative embodiment, the specific values of the first oil return frequency and the second oil return frequency are not fixed, and those skilled in the art can adjust them based on needs. Such adjustment of the values does not deviate from the principles of this application.

[0067] Of course, the above-mentioned replaceable implementations, as well as the replaceable implementations and the preferred implementations, can be used in a cross-functional manner to combine new implementations to suit more specific application scenarios.

[0068] The following combination Figure 2 , a possible control process of the oil return control method of the truck air conditioner of this application is introduced. Figure 2 This is a logic diagram of the oil return control method of the truck air conditioner of this application.

[0069] like Figure 2 As shown, in one possible control process:

[0070] S201 , during the operation of the truck air conditioner, obtain the operating frequency f of the compressor and the air outlet temperature Te of the indoor unit, and then execute S202 .

[0071] S202, determine whether f≤f1 holds. If so, execute S203; otherwise, if not, execute S206. Where f1 is a preset frequency threshold.

[0072] S203, determine whether Te≤T1 holds. If so, execute S205; otherwise, if not, execute S204. T1 is a preset temperature threshold.

[0073] S204, determine whether the duration t≥30min is satisfied. If so, execute S208; otherwise, return to execute S204.

[0074] S205, determine whether the duration t≥30min is satisfied. If so, execute S209; otherwise, return to execute S205.

[0075] S206, determine whether Te≤T1 holds. If so, execute S207; otherwise, if not, execute S211. T1 is a preset temperature threshold.

[0076] S207, determine whether the duration t≥60min is satisfied. If so, execute S210; otherwise, return to execute S207.

[0077] S208 , controlling the compressor to first increase the frequency to the maximum frequency f2 and run for 3 minutes, and then reduce the frequency of the compressor to the previous frequency f and continue to run.

[0078] S209, control the compressor to first increase the frequency to the maximum frequency f2, and the internal fan to increase the speed to the maximum speed rmax and run for 3 minutes, then control the compressor to reduce the frequency to the previous frequency f, and reduce the speed of the internal fan to the previous speed r.

[0079] S210: Control the internal fan to first increase the speed to the maximum speed rmax at an acceleration of 50r / 15min, and then control the internal fan to decrease the speed to the previous speed r at an acceleration of 50r / 15min.

[0080] S211, controls the truck air conditioner to maintain the current operating state.

[0081] Although the various steps in the above embodiment are described in the above-mentioned order, those skilled in the art will understand that in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order. They can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the scope of protection of this application.

[0082] The present application also provides a computer-readable storage medium. In a computer-readable storage medium embodiment according to the present application, the computer-readable storage medium can be configured to store a program for executing the oil return control method for a truck air conditioner of the above-mentioned method embodiment. The program can be loaded and run by a processor to implement the above-mentioned oil return control method for a truck air conditioner. For ease of explanation, only the parts related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method part of the embodiment of the present invention. The computer-readable storage medium can be a storage device formed by various electronic devices. Optionally, the computer-readable storage medium in the embodiment of the present invention is a non-transitory computer-readable storage medium.

[0083] The present application also provides a control device. In one embodiment of the control device according to the present application, the control device includes a processor and a memory. The memory can be configured to store a program that executes the oil return control method for a truck air conditioner according to the above-described method embodiment, and the processor can be configured to execute the program in the memory, which includes but is not limited to a program that executes the oil return control method for a truck air conditioner according to the above-described method embodiment. For ease of explanation, only the portions related to the embodiment of the present invention are shown. For specific technical details not disclosed, please refer to the method section of the embodiment of the present invention. The control device can be a device formed by various electronic devices.

[0084] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of this application and to form different embodiments. For example, in the claims of this application, any of the claimed embodiments may be used in any combination.

[0085] Thus far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is readily understood by those skilled in the art that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present application.

Claims

1. A method for controlling oil return of a truck air conditioner, characterized in that: The truck air conditioner includes an outdoor unit and an indoor unit. The outdoor unit includes a compressor, an outdoor heat exchanger, an outdoor fan, and a throttling element. The indoor unit includes an indoor heat exchanger and an indoor fan. The compressor is vertically installed on the top or back of the truck cab. The oil return control method includes: Obtaining the operating frequency of the compressor and the air outlet temperature of the indoor unit; Comparing the operating frequency with a preset frequency threshold, and comparing the air outlet temperature with a preset temperature threshold; selectively performing an oil return operation on the compressor based on the comparison result; The step of “selectively performing an oil return operation on the compressor based on the comparison result” further includes: If the operating frequency is less than or equal to the preset frequency threshold, the air outlet temperature is greater than the preset temperature threshold, and the duration of the above state exceeds a first preset time, the following oil return operation is performed on the compressor: the compressor is controlled to increase the frequency to a first oil return frequency; wherein the first oil return frequency is greater than the preset frequency threshold; If the operating frequency is less than or equal to the preset frequency threshold, the outlet air temperature is less than or equal to the preset temperature threshold, and the above state lasts for more than a third preset time, the following oil return operation is performed on the compressor: the compressor is controlled to increase the frequency to a second oil return frequency, and the indoor fan is controlled to operate at a maximum speed; wherein the second oil return frequency is greater than the preset frequency threshold; If the operating frequency is greater than the preset frequency threshold, the air outlet temperature is less than or equal to the preset temperature threshold, and the duration of the above state exceeds the fifth preset time length, the following oil return operation is performed on the compressor: the speed of the internal fan is controlled to increase at a first preset acceleration until it reaches the maximum speed.

2. The oil return control method for a truck air conditioner according to claim 1, characterized in that: The oil return control method further includes: After the compressor operates at the first oil return frequency for a second preset time period, the compressor is controlled to reduce the frequency to the operating frequency and continue to operate.

3. The oil return control method for a truck air conditioner according to claim 1, characterized in that: The oil return control method further includes: After the compressor runs at the second oil return frequency for a fourth preset time, the compressor is controlled to reduce the frequency to the operating frequency and continue to run, and the speed of the internal fan is controlled to return to the speed before the oil return operation.

4. The oil return control method for a truck air conditioner according to claim 1, characterized in that: The oil return control method further includes: When the rotation speed of the internal fan rises to the maximum rotation speed, the rotation speed of the internal fan is controlled to decrease at a second preset acceleration until it decreases to the rotation speed before the oil return operation.

5. The oil return control method for a truck air conditioner according to claim 1, characterized in that: The step of “selectively performing an oil return operation on the compressor based on the comparison result” further includes: If the operating frequency is greater than the preset frequency threshold, and the air outlet temperature is greater than the preset temperature threshold, the oil return operation is not performed on the compressor.

6. A computer-readable storage medium storing a plurality of program codes, characterized in that: The program code is suitable for being loaded and run by a processor to execute the oil return control method for a truck air conditioner according to any one of claims 1 to 5.

7. A control device, characterized in that: include: processor; A memory, wherein the memory is adapted to store a plurality of program codes, wherein the program codes are adapted to be loaded and run by the processor to execute the oil return control method for a truck air conditioner according to any one of claims 1 to 5.

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