AU2022202621A1 - Cab pressure regulating system, cab and work machine including the same, and cab pressure regulating method - Google Patents

Abstract

CAB PRESSURE REGULATING SYSTEM, CAB AND WORK MACHINE INCLUDING THE SAME, AND CAB PRESSURE REGULATING METHOD The present disclosure relates to a cab pressure regulating system, a cab and a work machine including the same, and a method for regulating cab pressure. The cab is provided with an air conditioner, and the pressure regulating system includes an air supply device, a temperature sensor and a controller, the air supply device delivers air outside the cab into the cab to ensure a positive pressure in the cab, and the air supply device is provided with a regulating valve. The controller is configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on a difference between a measured value of the temperature sensor and a predetermined comfortable temperature. In the present disclosure, reduction of the air volume supplied by the air supply device can be realized when a rapid heating/cooling is required, the cooling/heating efficiency of the air conditioner is optimized while meeting the positive pressure requirement in the cab, and the energy consumption is reduced. In the present disclosure, a pressure sensor can also be provided in the cab, so as to ensure that the opening degree of the regulating valve can be reduced only when the positive pressure requirement is met. 1/3 cov emen

Description

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Description

CAB PRESSURE REGULATING SYSTEM, CAB AND WORK MACHINE INCLUDING THE SAME, AND CAB PRESSURE REGULATING METHOD

Technical Field

[0001] The present disclosure relates to a cab pressure regulating system and a pressure regulating method, and also relates to a cab and a work machine including the pressure regulating system.

Background

[0002] Work machines, such as motor graders, loaders, dozers, excavators, etc., work in a variety of work environments such as construction sites, mines, farms, and roads. Due to the harsh working environment of the work machine, there will be a lot of dust or blowing sand. In order to ensure the quality of the air breathed by the driver in a cab, one method is used to keep a positive pressure in the cab of the work machine to prevent dust etc. from entering into the cab. According to relevant standards such as ISO10263, the positive pressure in the cab (that is, the difference between the air pressure in the cab and the air pressure outside the cab) should be guaranteed to be greater than 50Pa, for example.

[0003] For this purpose, in the prior art, an air supply device is arranged on the cab to supply air into the cab to ensure a positive pressure in the cab. The air supply device may be in the form of a pre-cleaner, which supplies to the cab fresh air filtered with its air cleaning function.

[0004] Meanwhile, in order to ensure the comfort of the driver, an air conditioner is usually provided in the cab. By providing the air conditioner and the air supply device, drivers in the cab can still enjoy cool and fresh air even in the scorching sun and dusty conditions.

[0005] However, under extremely cold or extremely hot weather conditions, when the driver turns on the air conditioner, the cooling or heating performance of the air conditioner is seriously affected because the air supply device introduces air with very low or high temperature from the outside into the cab, resulting in energy waste.

[0006] Meanwhile, drivers have different preferences in the volume of air supplied by the air supply device. Continuous high volume of air supply may make some drivers feel uncomfortable, while other drivers may prefer more fresh air. Therefore, there is a demand for manually regulating the volume of air supplied by the air supply device according to personal preference.

[0007] The present disclosure aims to solve the above-mentioned problems and/or other problems existing in the prior art.

Summary of the Invention

[0008] A cab pressure regulating system is provided in the present disclosure. The cab is provided with an air conditioner. The pressure regulating system comprises an air supply device, a temperature sensor and a controller. The air supply device takes air outside the cab into the cab to ensure a positive pressure in the cab and is provided with a regulating valve for regulating an amount of air supplied by the air supply device. The temperature sensor is arranged in the cab to measure temperature in the cab; and the controller is connected to the regulating valve and the temperature sensor and is used to control regulation of opening degree of the regulating valve; the controller is configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on a difference between a measured value of the temperature sensor and a predetermined comfortable temperature.

[0009] The present disclosure also provides a method for regulating pressure in a cab, the cab is provided with an air conditioner and an air supply device for delivering air outside the cab into the cab to ensure a positive pressure in the cab; the air supply device is provided with a regulating valve for regulating an amount of air supplied by the air supply device, the method including: a judging step: in an ON state of the air conditioner, measuring temperature in the cab, and judging whether to automatically adjust an opening degree of the regulating valve of the air supply device depending on a difference between a measured temperature and a predetermined comfortable temperature; and a regulating step: regulating the opening degree of the regulating valve when the regulating valve needs to be regulated.

[0010] The present disclosure also provides a cab comprising the cab pressure regulating system as described above.

[0011] The present disclosure further provides a work machine comprising the cab as described above.

[0012] Advantages of the present disclosure lie in at least the following points. By providing a regulating valve in the air supply device, a temperature sensor in the cab, and the controller configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on a temperature difference, regulation of the air volume supplied by the air supply device is achieved when rapid heating/cooling is required, thus the cooling/heating efficiency of the air conditioner is optimized and energy consumption is reduced while meeting the positive pressure requirement. Moreover, by providing a pressure sensor to ensure that the opening degree of the regulating valve is reduced only when the positive pressure requirement is met, the positive pressure in the cab can be automatically ensured, the positive pressure in the cab can be monitored in real time and the regulation of positive pressure in the cab can be controlled more sensitively. Through the displaying and manual regulating device, it is convenient for the driver to know the positive pressure in the cab and adjust the positive pressure according to personal preference. Further, the alarm warns the driver to timely check the sealing problem of the cab and the failure of the air supply device. Moreover, the regulating system of the present disclosure does not need to make any change to the air conditioning system of the cab, instead, only an input of the on/off signal of the air conditioner to the controller is needed. Therefore, an improvement in air conditioning efficiency is achieved with a simple structure.

Brief Description of the Drawings

[0013] FIG. 1 shows a schematic perspective view of a work machine to which a cab pressure regulating system according to an exemplary illustration of the present disclosure is applied;

[0014] FIG. 2 shows a schematic diagram of a cab pressure regulating system according to an exemplary illustration of the present disclosure; and

[0015] FIG. 3 shows a flowchart of a method for regulating pressure in a cab according to an exemplary illustration of the present disclosure.

Detailed Description

[0016] The technical solutions of the present disclosure will be further described in detail below in conjunction with the embodiments and the accompanying drawings. The description of the embodiments of the present disclosure with reference to the accompanying drawings intends to illustrate the general inventive concept of the invention, and should not be construed as a limitation to the invention.

[0017] In addition, in the detailed description below, for ease of interpretation, many specific details are described to provide a comprehensive understanding of the disclosed embodiments. Obviously, however, one or more embodiments may also be implemented without these specific details.

[0018] FIG. 1 shows an exemplary work machine 100. The work machine 100 maybe any type of machine that performs operations related to a particular industry (e.g. construction, mining, agriculture, transportation, etc.) and works in various work environments (e.g. construction sites, mines, farms, roads, etc.), such as a motor grader, a wheel loader, a wheel dozer, a crawler excavator, etc.

[0019] The work machine 100 may include amain frame 30, a cab 35 and a work implement 36. In one embodiment, the work implement 36 may be a bucket applied to a loader. A running device is provided at the lower part of the work machine 100 for supporting and moving the work machine 100. As an example, the running device is provided as wheels 41.

[0020] During the operation of the work machine 100 in a harsh work environment, in order to ensure the quality of the air breathed by the driver in the cab, it is necessary to keep a positive pressure in the cab of the work machine to prevent dust and the like from entering the cab. According to relevant standards such as ISO10263, the positive pressure in the cab (that is, the difference between the air pressure in the cab and the air pressure outside the cab) should be guaranteed to be not less than 50Pa, for example. In the example described below, the cab is provided with an air supply device to ensure positive pressure in the cab. When the work machine is started, the air supply device is activated by default to continuously supply fresh air to the cab, thereby ensuring that the relative air pressure in the cab with respect to the outside of the cab is greater than a minimum positive pressure required in the cab (e.g. 50Pa).

[0021] As an exemplary illustration, the present disclosure provides a pressure regulating system for a cab, the cab is provided with an air conditioner. The pressure regulating system comprises: an air supply device for delivering air outside the cab into the cab to ensure a positive pressure in the cab; the air supply device is provided with a regulating valve for regulating an volume of air supplied by the air supply device; a temperature sensor arranged in the cab to measure temperature in the cab; and a controller connected to the regulating valve and the temperature sensor and used to control regulation of opening degree of the regulating valve. The controller is configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on a difference between a measured value of the temperature sensor and a predetermined comfortable temperature.

[0022] In the above illustration, the cab is provided with an air supply device and an air conditioner. As an example, the air supply device is turned on at the maximum opening degree by default to rapidly increase the pressure in the cab. In this illustration, in the ON state of the air conditioner, if the temperature in the cab is very high or very low, for example, having a large difference from the predetermined comfortable temperature (the temperature that the human body feels comfortable, for example, 20°C), for example, larger than 10°C (that is, the temperature in the cab is higher than 30°C or lower than 10°C), it means that the cab needs to be cooled rapidly. At this time, if the air supply device still keeps taking a large volume of high temperature or low-temperature gas outside the cab into the cab continuously, it will greatly slow down the cooling or heating process of the air conditioner and affect the performance of the air conditioner. Therefore in this illustration a temperature sensor is also provided in the cab to measure the temperature in the cab. The controller is configured to determine that the opening degree of the regulating valve is reduced and an operation of the reduction is performed, if the difference between the measured value of the temperature sensor and the predetermined comfortable temperature is greater than 10°C. In this illustration, if the difference between the measured value of the temperature sensor and the predetermined comfortable temperature exceeds 10°C, the opening degree of the regulating valve is automatically reduced, so that the air flow delivered to the cab from the outside through the air supply device is reduced so as to reduce the impact on the cooling/heating effect of the air conditioner and improve the working efficiency of the air conditioner. Meanwhile, in this illustration, no changes need to be made to the air conditioning system of the cab, instead, only an input of an on/off signal of the air conditioner to the controller is needed. Therefore, an improved efficiency in air conditioning is achieved with a simple structure. Preferably, the air supply device may be a pre-cleaner, which supplies filtered fresh air to the cab with its air cleaning function.

[0023] Further, a pressure sensor may also be provided, which is installed in the cab to measure the positive pressure in the cab; the controller is configured to determine, in the ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on the difference between the measured value of the temperature sensor and the predetermined comfortable temperature and the comparison result between a measured value of the pressure sensor and a predetermined positive pressure.

[0024] As an illustration, the controller is configured to determine that the opening degree of the regulating valve is reduced and a reduction in the opening degree is performed, if the difference in temperature is greater than a predetermined value (e.g. 100 C.) and the measured value of the pressure sensor is greater than a predetermined positive pressure. By this illustration, it is realized to automatically regulate the opening degree of the regulating valve under the condition that the positive pressure requirement in the cab is met. If the difference between the measured value of the temperature sensor and the predetermined comfortable temperature is less than a certain value, that is, when rapid cooling is not required, or if the positive pressure in the cab is insufficient, the opening degree of the regulating valve shall not be reduced.

[0025] As described above, the operation of the air supply device should first ensure positive pressure in the cab. In this illustration using the pressure sensor, one end of the pressure sensor provided is communicated with the outside atmosphere, and the other end is communicated with the cab. Output of the measured value from the pressure sensor is a difference between the pressure in the cab and the outside atmosphere pressure, that is, the positive pressure. A predetermined positive pressure can be set in the controller. It should be noted that the predetermined positive pressure may be a positive pressure greater than the minimum positive pressure required to meet the ISO standard, that is, a positive pressure to ensure a certain margin in the positive pressure. For example, the predetermined positive pressure is set to be greater than the minimum positive pressure required by the cab in consideration of the inevitable tolerances of the air supply device, the pressure sensor, etc., and the unsatisfactory airtightness of the cab. For example, when the minimum positive pressure is 50Pa, the predetermined positive pressure may be 55Pa. Those skilled in the art can understand that the predetermined positive pressure is set to be greater than the required minimum positive pressure in the above illustration, in order to ensure a better effect in positive pressure. However, the predetermined positive pressure may also be equal to the required minimum positive pressure (that is, the minimum positive pressure required in the cab to meet the standard).

[0026] In this illustration, the controller is configured to determine whether to automatically regulate the opening degree of the regulating valve based on the following, 1) the difference between the measured value of the temperature sensor and the predetermined comfortable temperature, and 2) the comparison result of the measured value of the pressure sensor with the predetermined positive pressure. Therefore, in this example, both the positive pressure and the temperature in the cab are taken into account, and it is determined to regulate the opening degree of the regulating valve of the air supply device only when both of the two are satisfied. At the same time, by providing the pressure sensor, it is also allowed to monitor the positive pressure in the cab in real time and control the regulation of the positive pressure in the cab more sensitively.

[0027] It should be noted that although the pressure sensor described in the previous illustration allows firstly ensuring required positive pressure in the cab at the time of regulating the opening degree of the regulating valve of the air supply device to improve the air conditioning efficiency, the pressure sensor is not necessary. For example, in one illustration described below (will be explained further below), the regulating valve is configured to have a minimum opening degree at which the minimum positive pressure required in the cab can be met. In this way a minimum positive pressure can be guaranteed without the use of a pressure sensor.

[0028] To ensure the minimum positive pressure, the controller is further configured to prohibit reducing the opening degree of the regulating valve if the measured value of the pressure sensor is less than or equal to the minimum positive pressure required in the cab. The minimum positive pressure value is pre-set in the controller. The minimum positive pressure can also be ensured in other ways, for example, by configuring the regulating valve with a minimum opening degree at which the minimum positive pressure required in the cab is provided. In other words, the minimum opening degree of the regulating valve is ensured structurally. Through both of the above two ways, the positive pressure in the cab can be ensured at the time of automatically regulating the regulating valve of the air supply device. However, these two ways can also be used at the same time, providing a double guarantee of the minimum positive pressure.

[0029] As an example, as shown in Fig. 2, the cab pressure regulating system further comprises a displaying and manual regulating device, the device being configured to display the measured value of the pressure sensor and provided with a regulating key connected to the controller to regulate the opening degree of the regulating valve. Through the displaying and manual regulating device in this example, the driver can know the positive pressure in the cab visually, and can also conveniently regulate the air volume supplied by the air supply device manually according to personal preference.

[0030] Therefore, in the present disclosure, the opening degree of the regulating valve of the air supply device can be regulated automatically or manually.

[0031] As shown in Fig. 2, the cab pressure regulating system may further comprises an alarm connected to the controller, the controller is configured to control the alarm to send out a warning signal in the event that the measured value of the pressure sensor is less than a minimum positive pressure required in the cab. In this illustration, the system has monitoring and alarm functions to the positive pressure in the cab. If the positive pressure in the cab is less than the minimum positive pressure, for example, less than 50Pa, the displaying and manual regulating device and the alarm cooperate to inform the driver of a low pressure state that does not meet the minimum positive pressure and suggest the driver that it is necessary to check the airtightness in the cab or whether there is fault with the air supply device.

[0032] The present disclosure also provides a method for regulating pressure in a cab, the cab being provided with an air conditioner and an air supply device for delivering air outside the cab into the cab to ensure a positive pressure in the cab; and the air supply device being provided with a regulating valve for regulating a volume of air supplied by the air supply device. The method includes: a judging step: in an ON state of the air conditioner, measuring temperature in the cab, and judging whether to automatically adjust an opening degree of the regulating valve of the air supply device depending on a difference between a measured temperature and a predetermined comfortable temperature; and a regulating step: regulating the opening degree of the regulating valve when the regulating valve needs to be regulated.

[0033] Those skilled in the art can understand that the regulating step not only includes regulating the opening degree of the regulating valve if the air conditioner is in an ON state and the difference in temperature is too large and requiring rapid heating/cooling as described in this illustration, but also includes, for example, regulating the opening degree of the regulating valve according to the manual operation of the driver. Exemplarily, in this judging step, it is judged that the opening degree of the regulating valve is reduced if the difference in temperature is greater than a predetermined value (e.g. 10 C).

[0034] Correspondingly, as to the illustration in which the pressure sensor is provided in the cab, the regulating method further includes the step of measuring the positive pressure in the cab, and in the judging step, judging, in an ON state of the air conditioner, whether to automatically adjust the opening degree of the regulating valve depending on the difference between the measured temperature and the predetermined comfortable temperature and the comparison result between a measured positive pressure and a predetermined positive pressure. Exemplarily, in this judging step, it is determined that the opening degree of the regulating valve is reduced, if the difference is greater than a predetermined value (e.g. 10° C) and the measured value of the positive pressure is greater than the predetermined positive pressure.

[0035] Exemplarily, the method further includes a step of prohibiting reduction of the opening degree of the regulator valve when the measured positive pressure is less than a minimum positive pressure required in the cab.

[0036] Fig. 3 shows a flowchart of a method for regulating pressure in a cab according to an exemplary illustration of the present disclosure, and the present disclosure can be better understood through the description of the method. In the detailed example shown in this flowchart, the cab pressure regulating system employs the temperature sensor, the pressure sensor, the displaying and manual regulating device, and an alarm to perform the detailed pressure regulating method. However, it will be understood by those skilled in the art, that one or more embodiments may be practiced without these specific details.

[0037] Firstly, the work machine is started by, for example, turning a key. The air supply device is turned on and the regulating valve thereof opens to a maximum opening degree as default, to rapidly deliver air into the cab. After a predetermined time (the predetermined time is determined to be a time within which the air supply device can deliver air to increase the positive pressure in the cab to a predetermined value, for example, to the minimum positive pressure required in the cab), the positive pressure P in the cab is obtained by the pressure sensor, and it is judged whether the positive pressure is greater than or equal to the minimum positive pressure (for example, 50Pa). If the positive pressure is less than the minimum positive pressure, the alarm is activated and words such as "Attention! Low pressure!" are displayed on the displaying screen of the displaying and manual regulating device, so as to inform the driver to check the tightness of the cab, for example, to check whether the door of the cab is completely closed, or whether there is fault with the air supply device. If the positive pressure is greater than or equal to the minimum positive pressure, then it is judged whether the regulating key on the displaying and manual regulating device is operated, if so, the opening degree of the regulating valve of the air supply device is controlled according to the signal from the displaying and manual regulating device.

[0038] Simultaneously, the state of the air conditioner is detected to see whether it is in an ON state. If yes, judging whether the difference between the measured value T from the temperature sensor and the predetermined comfortable temperature (20°C) is greater than a predetermined value (for example, 10°C, if so, it means a rapid heating or cooling is required. ) and whether the measurement result from the pressure sensor is greater than a predetermined positive pressure (e.g. 55Pa), if so, automatically reducing the opening degree of the regulating valve to reduce the air volume supplied by the air supply device. If not, the regulation of the opening degree of the regulating valve is not performed.

[0039] The present disclosure also relates to a cab comprising the pressure regulating system and the air conditioner as described above. The pressure regulating system can improve the cooling/heating effect of the air conditioner while ensuring the positive pressure in the cab, improve the efficiency of the air conditioner, and reduce energy waste.

[0040] Furthermore, the present disclosure also relates to a work machine comprising the above-described cab, whereby the work machine can ensure the positive pressure in the cab and the efficiency of the air-conditioner during operation, give the driver a more comfortable experience, and facilitate operation of the driver.

Industrial Applicability

[0041] The cab pressure regulating system and method according to the present disclosure can be applied to cabs of various work machines and innovatively coordinate the air supply device and the air conditioner in the cab of the work machine, so that not only the positive pressure in the cab can be ensured, but also efficiency of the air conditioner can be improved. The operation of the cab pressure regulating system is described below exemplarily. - After a predetermined time following starting of the work machine (for example, one minute), when the air conditioner is not open, the pressure sensor measures the positive pressure in the cab. If the pressure difference of the pressure in the cab relative to the outside atmosphere pressure is lower than the minimum positive pressure required in the cab, the displaying and manual regulating device and the alarm will cooperate to inform the driver of a low pressure state and suggest the driver that it is necessary to check the airtightness in the cab or whether there is fault with the air supply device. If the current pressure difference is greater than the minimum positive pressure required in the cab, the driver can control the opening degree of the regulating valve through the keys on the displaying and manual regulating device according to personal preference, so as to regulate the air volume supplied by the air supply device. If the positive pressure in the cab is reduced to a threshold value, that is, the minimum positive pressure, the controller will control the regulating valve to no longer reduce the opening degree, or the structure of the regulating valve itself restricts further reduction of the opening degree.

- When the air conditioner is turned on, the controller firstly judges whether the cab needs to be cooled/heated rapidly according to the difference between the measurement value of the temperature sensor and the predetermined comfortable temperature (e.g. 20°C). If the absolute value of the difference in temperature is greater than a predetermined value, such as °C, it means that the temperature outside the cab is greater than 30°C or less than 10°C. At this time, if difference of the pressure in the cab relative to the outside atmosphere pressure is greater than the predetermined positive pressure, such as 55Pa, the controller will automatically drive the regulating valve to reduce the opening degree thereof and decrease the inflow amount of air, while guaranteeing the pressure difference to be larger than 50Pa, so that the temperature in the cab can reach the temperature set by the air conditioner rapidly. If the difference in temperature is less than 10°C or the difference of the pressure in the cab relative to the outside atmosphere pressure is less than 55Pa, the controller will not actively adjust the opening degree of the air valve. During the whole process, the driver can make manual regulation according to personal preference through the displaying and manual regulating device.

[0042] Various modifications and variations can be made by those skilled in the art to the embodiments disclosed above without departing from the scope or spirit of the disclosure. According to the practice of the invention disclosed in the specification, other embodiments of the invention are obvious to those skilled in the art. The specification and the embodiments disclosed therein shall be considered as illustrative only, and the real scope of the invention shall be specified by the appended claims and their equivalents.

Claims (19)

Claims

1. A cab pressure regulating system, wherein the cab is provided with an air conditioner, the pressure regulating system comprising: an air supply device for delivering air outside the cab into the cab to ensure a positive pressure in the cab; wherein the air supply device is provided with a regulating valve for regulating a volume of air supplied by the air supply device; a temperature sensor arranged in the cab to measure temperature in the cab; and a controller connected to the regulating valve and the temperature sensor and used to control regulation of opening degree of the regulating valve, wherein the controller is configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on a difference between a measured value of the temperature sensor and a predetermined comfortable temperature.

2. The cab pressure regulating system according to claim 1, further comprising a pressure sensor installed in the cab to measure the positive pressure in the cab; wherein the controller is configured to determine, in an ON state of the air conditioner, whether to automatically regulate the opening degree of the regulating valve depending on the difference between the measured value of the temperature sensor and the predetermined comfortable temperature and the comparison result between a measured value of the pressure sensor and a predetermined positive pressure.

3. The cab pressure regulating system according to claim 1, wherein the controller is configured to determine that the opening degree of the regulating valve is reduced and a reduction in the opening of the regulating valve is performed, if the difference is greater than a predetermined value.

4. The cab pressure regulating system according to claim 2, wherein the controller is configured to determine that the opening degree of the regulating valve is reduced and a reduction in the opening degree of the regulating valve is performed, if the difference is greater than a predetermined value and the measured value of the pressure sensor is greater than a predetermined positive pressure.

5. The cab pressure regulating system according to claim 3 or claim 4, wherein the predetermined value is 10°C.

6. The cab pressure regulating system according to claim 2, further comprising a displaying and manual regulating device, the device being configured to display the measured value of the pressure sensor and provided with a regulating key connected to the controller to regulate the opening degree of the regulating valve.

7. The cab pressure regulating system according to any one of claims 2, 4 and 6, wherein the controller is further configured to prohibit reducing the opening degree of the regulating valve if the measured value of the pressure sensor is less than or equal to a minimum positive pressure required in the cab.

8. The cab pressure regulating system according to any one of claims 1-6, wherein the regulating valve is configured to have a minimum opening degree at which a minimum positive pressure required in the cab is provided.

9. The cab pressure regulating system according to any one of claims 1-8, further comprising an alarm connected to the controller, wherein the controller is configured to control the alarm to send out a warning signal in the event that the measured value of the pressure sensor is less than a minimum positive pressure required in the cab.

10. A cab comprising a cab pressure regulating system according to any one of claims 1-9 and an air conditioner.

11. A work machine comprising the cab according to claim 10.

12. A method for regulating pressure in a cab, wherein the cab is provided with an air conditioner and an air supply device for delivering air outside the cab into the cab to ensure a positive pressure in the cab; and wherein the air supply device is provided with a regulating valve for regulating a volume of air supplied by the air supply device, the method including: a judging step: in an ON state of the air conditioner, measuring temperature in the cab, and judging whether to automatically adjust an opening degree of the regulating valve of the air supply device depending on a difference between a measured temperature and a predetermined comfortable temperature; and a regulating step: regulating the opening degree of the regulating valve when the regulating valve needs to be regulated.

13. The method according to claim 12, further comprising a step of measuring the positive pressure in the cab, and in the judging step, judging, in an ON state of the air conditioner, whether to automatically adjust the opening degree of the regulating valve depending on the difference between the measured temperature and the predetermined comfortable temperature and the comparison result between a measured positive pressure and a predetermined positive pressure.

14. The method according to claim 12, wherein, in the judging step, it is judged that the opening degree of the regulating valve needs to be reduced if the difference is larger than a predetermined value.

15. The method according to claim 13, wherein, in the judging step, it is judged that the opening degree of the regulating valve needs to be reduced if the difference is larger than a predetermined value and the measured positive pressure is larger than the predetermined positive pressure.

16. The method according to claim 14 or 15, wherein the predetermined value is 10°C.

17. The method according to claim 12, further comprising a step of sending out a warning signal when the measured positive pressure is less than a minimum positive pressure required in the cab.

18. The method according to any one of claims 12-17, wherein the cab is further provided with a displaying and manual regulating device provided with a regulating key, and wherein the method further includes a step of regulating the opening degree of the regulating valve when the key is operated.

19. The method according to any one of claims 12-17, further including a step of prohibiting reduction of the opening degree of the regulator valve if the measured positive pressure is less than or equal to a minimum positive pressure required in the cab.