CN103423835A - Control method of vehicle air-conditioning system and vehicle air-conditioning system - Google Patents

Abstract

The invention provides a control method of a vehicle air-conditioning system and the vehicle air-conditioning system. The control method includes the steps that an actual degree of superheat, a preset degree of superheat and the opening degree of an electronic expansion valve are obtained; whether the electronic expansion valve is in a failure state or not is judged according to the obtained actual degree of superheat, the preset degree of superheat and the opening degree of the electronic expansion valve; a control signal is outputted to an execution control mechanism when the judging result is that the electronic expansion valve is in the failure state; the execution control mechanism controls and adjusts parameters of equipment influencing changes of the actual degree of superheat in the vehicle air-conditioning system to adjust the degree of superheat of the vehicle air-conditioning system. According to the control method, whether the electronic expansion valve is in the failure state or not is judged according to the opening degree of the electronic expansion valve, the actual degree of superheat and the preset degree of superheat, the control signal is outputted to the execution control mechanism according to the judging result, and the execution control mechanism controls the parameters of the equipment influencing the changes of the actual degree of superheat in the vehicle air-conditioning system, and thus the system continues operating in a mode of normal performance or degraded performance.

Description

Control method of vehicle air conditioning system and vehicle air conditioning system

The application is a divisional application of patent applications with application date of 2012, 24/04, application number of 201210121890.2, and invention name of vehicle air conditioning system and control method thereof.

Technical Field

The invention relates to a control method of a vehicle air conditioning system and the vehicle air conditioning system, in particular to a vehicle air conditioning control method and a vehicle air conditioning control system which can control the superheat degree of the vehicle air conditioning system by adjusting the rotating speed or the discharge capacity of a compressor and/or the rotating speed of an evaporator fan and the like after an electronic expansion valve fails so that the vehicle air conditioning system can continuously run in a normal performance or a performance reduction mode, and belongs to the technical field of automobile air conditioning.

Background

The automobile air conditioning system mainly comprises a compressor, a condenser, a throttling element and an evaporator, wherein high-temperature and high-pressure refrigerant gas from the compressor is condensed by the condenser to become refrigerant liquid, the refrigerant liquid enters the evaporator after being throttled and depressurized by the throttling element, the refrigerant gas is changed into refrigerant gas and returns to the compressor again after being subjected to heat exchange with air outside the evaporator in the evaporator, so that a refrigeration cycle is completed, the air cooled by the evaporator enters a vehicle cabin, and if the temperature in the vehicle cabin is lower than or higher than a set temperature in the vehicle cabin, the degree of superheat is controlled by controlling and adjusting the opening degree of the throttling element.

Wherein, select electronic expansion valve as throttling element, have following advantage:

the electronic expansion valve can be adjusted according to various parameters in the air-conditioning system, and the corresponding control strategy is adjusted in real time according to different working conditions, so that the aims of improving the efficiency of the refrigeration system, saving energy and protecting environment are fulfilled; the control superheat degree of the electronic expansion valve is more stable than that of the thermal expansion valve, so that the air outlet temperature is more stable, and the comfort level is improved.

However, in the prior art, when the electronic expansion valve has a locked-rotor fault and is stuck in a certain position and cannot act, or when the electronic expansion valve has a fault and cannot be opened to a certain interval, the current vehicle air conditioning system cannot take corresponding fault treatment measures, so that the air conditioning system is damaged.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a control method of a vehicle air conditioning system and the vehicle air conditioning system, which are used for controlling the superheat degree of the vehicle air conditioning system and enabling the vehicle air conditioning system to continue to operate in a normal performance or performance reduction mode without damaging the system.

The technical scheme provided by the invention is as follows:

a method of controlling an air conditioning system for a vehicle, the method comprising:

acquiring an actual superheat degree, a preset superheat degree and an opening degree of an electronic expansion valve;

judging whether the electronic expansion valve is in a fault state or not according to the acquired actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve;

and when the judgment result shows that the electronic expansion valve is in a fault state, outputting a control signal to an execution control mechanism, and controlling and adjusting parameters of equipment influencing the actual superheat degree change in the vehicle air-conditioning system by the execution control mechanism so as to adjust the superheat degree of the vehicle air-conditioning system.

Further, the parameters of the device influencing the actual superheat degree change in the vehicle air conditioning system include: speed or displacement C of the compressor₁And/or the rotational speed C of the evaporator fan₂。

Furthermore, on the premise that the judgment result is that the electronic expansion valve is in a fault state,

when the actual superheat degree is larger than the first preset superheat degree, a control signal is output to the execution control mechanism, and the execution control mechanism controls to reduce the rotating speed or the discharge capacity C of the compressor₁Or reducing the rotating speed C of the evaporator fan₂Or turning off the compressor;

when the actual superheat degree is less than a second preset superheat degree, a control signal is output to the execution control mechanism, and the execution control mechanism controls and increases the rotating speed or the discharge capacity C of the compressor₁Or increasing the rotating speed C of the fan of the evaporator₂Or turning off the compressor;

when the actual superheat degree is more than or equal to a second preset superheat degree and less than or equal to a first preset superheat degree, a control signal is output to an execution control mechanism, and the execution control mechanism controls the rotating speed or the discharge capacity C of the compressor₁And the rotational speed of the evaporator fanC₂Remain unchanged.

Further, on the premise that the actual superheat degree is larger than the first preset superheat degree,

when the compressor speed or displacement C₁Greater than a minimum value C_1min+Δ₁Outputting control signal to the executing control mechanism, and controlling to reduce the rotation speed or discharge C of the compressor by the executing control mechanism₁，

When the compressor speed or displacement C₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂Greater than a minimum value C_2min+Δ₂When the evaporator fan is started, a control signal is output to an execution control mechanism, and the execution control mechanism controls and reduces the rotating speed C of the evaporator fan₂，

When the compressor speed or displacement C₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂To a minimum value C_2min+Δ₂When the compressor is started, a control signal is output to the execution control mechanism, and the execution control mechanism controls the compressor to be closed;

on the premise that the actual superheat degree is less than the second preset superheat degree,

when the low pressure of the vehicle air conditioning system is higher than the low pressure alarm value and the high pressure is lower than the high pressure alarm value, and the rotating speed or the discharge capacity C of the compressor₁Less than a maximum value C_1max-Δ₃When the compressor is started, the control signal is output to the executing control mechanism, and the executing control mechanism controls and increases the rotating speed or the discharge capacity C of the compressor₁；

When the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂Less than a maximum value C_2max-Δ₄When the evaporator fan is started, a control signal is output to an execution control mechanism, and the execution control mechanism controls and increases the rotating speed C of the evaporator fan₂；

When the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value, and the evaporatorRotational speed C of fan₂To a maximum value C_2max-Δ₄And when the compressor is started, the control signal is output to the execution control mechanism, and the execution control mechanism controls the compressor to be closed.

Further, the speed or displacement C of the compressor₁Or the rotating speed C of the evaporator fan₂Obtained according to the following calculations:

$C=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}$

in the formula,

c is the speed or displacement C of the compressor₁Or the rotational speed C of the evaporator fan₂，

e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a coefficient of proportionality that is,

K_din order to be the differential coefficient,

K_iis an integral coefficient.

Further, the method further comprises the following steps:

acquiring the actual superheat degree and the preset superheat degree, and acquiring feed-forward information influencing the actual superheat degree change in real time;

adjusting the opening degree of an electronic expansion valve in real time according to the obtained actual superheat degree, the preset superheat degree and feed-forward information to control the superheat degree of a vehicle air conditioning system, wherein the feed-forward information comprises the rotating speed or displacement variable quantity of a compressor; and/or the rotating speed variation of the evaporator fan.

The invention also provides a vehicle air conditioning system, which comprises a compressor unit and a throttling element, wherein the compressor unit comprises a compressor, a condenser, an evaporator and an evaporator fan, and the throttling element comprises an electronic expansion valve; the vehicle air conditioning system further includes:

the first acquisition module is used for acquiring the actual superheat degree and the opening degree of the electronic expansion valve in real time;

the first controller is used for storing a preset superheat degree, receiving an actual superheat degree and the opening degree of the electronic expansion valve, judging whether the electronic expansion valve is in a fault state or not according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve, and generating a first control signal according to the acquired actual superheat degree when the electronic expansion valve is in the fault state according to a judgment result;

and the execution control mechanism is used for receiving the first control signal sent by the first controller and controlling and adjusting parameters of equipment influencing the actual superheat degree change in the vehicle air conditioning system according to the first control signal.

Further, the parameters of the device influencing the actual superheat degree change in the vehicle air conditioning system include:

speed or displacement C of the compressor₁And/or the rotational speed C of the evaporator fan₂。

Further, the first controller includes:

the judging module is used for judging whether the electronic expansion valve is in a fault state or not according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve and generating a first control command when the judging result shows that the electronic expansion valve is in the fault state;

a first control module for receiving the judgment moduleThe first control command is sent by the block, and when the actual superheat degree is larger than a first preset superheat degree, the execution control mechanism is controlled to execute the reduction of the rotating speed or the discharge capacity C of the compressor₁Or reducing the rotating speed C of the evaporator fan₂Or a command to shut down the compressor;

the second control module is used for receiving the first control command sent by the judging module and controlling the execution control mechanism to execute and improve the rotating speed or the discharge capacity C of the compressor when the actual superheat degree is less than a second preset superheat degree₁Or increasing the rotating speed C of the fan of the evaporator₂Or a command to shut down the compressor;

a third control module for receiving the first control command sent by the judging module and controlling the execution control mechanism to execute and maintain the rotating speed or the discharge capacity C of the compressor when the actual superheat degree is more than or equal to a second preset superheat degree and less than or equal to a first preset superheat degree₁Or increasing the rotating speed C of the fan of the evaporator₂An unchanging command.

Further, the first control module comprises:

a first command module for commanding the speed or the displacement C of the compressor₁Greater than a minimum value C_1min+Δ₁When the compressor is in the normal state, the execution control mechanism is controlled to execute the reduction of the rotating speed or the displacement C of the compressor₁A command of (2);

a second command module for controlling the speed or the displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotating speed C of the evaporator fan₂Greater than a minimum value C_2min+Δ₂When the evaporator is started, the execution control mechanism is controlled to execute the reduction of the rotating speed C of the evaporator fan₂A command of (2);

a third command module for controlling the speed or the displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂To a minimum value C_2min+Δ₂When the compressor is in use, the execution control mechanism is controlled to execute the compression closingA command of the machine;

the second control module includes:

a fourth command module for controlling the rotation speed or displacement C of the compressor when the low pressure of the vehicle air conditioning system is higher than the low pressure warning value and the high pressure is lower than the high pressure warning value₁Less than a maximum value C_1max-Δ₃When the compressor is started, the execution control mechanism is controlled to execute the operation of increasing the rotating speed or the discharge capacity C of the compressor₁A command of (2);

a fifth command module for controlling the rotation speed C of the evaporator fan when the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value₂Less than a maximum value C_2max-Δ₄When the evaporator is started, the execution control mechanism is controlled to execute the operation of increasing the rotating speed C of the fan of the evaporator₂A command of (2);

a sixth command module for indicating whether the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂To a maximum value C_2max-Δ₄And controlling the execution control mechanism to execute a command of closing the compressor.

Further, the rotation speed or displacement of the compressor, or the rotation speed of the evaporator fan is obtained according to the following calculation:

$C=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}$

in the formula,

c is the speed or displacement C of the compressor₁Or the rotational speed C of the evaporator fan₂，

e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a coefficient of proportionality that is,

K_din order to be the differential coefficient,

K_iis an integral coefficient.

Further, the vehicle air conditioning system further includes:

the second acquisition module is used for acquiring feed-forward information influencing the actual superheat degree change in real time;

and the second controller is used for storing a preset superheat degree, receiving an actual superheat degree and feed-forward information, and adjusting the opening degree of the electronic expansion valve in real time according to the actual superheat degree, the preset superheat degree and the feed-forward information, wherein the feed-forward information comprises the rotating speed or displacement variation of the compressor and/or the rotating speed variation of the evaporator fan.

Further, the first acquisition module and the second acquisition module are communicated with the second controller through a vehicle CAN bus or a LIN bus; the first controller, the second controller and the electronic expansion valve are communicated through a CAN bus or a LIN bus of the vehicle.

The invention has the beneficial effects that:

compared with the prior art, the control method obtains the judgment result of whether the electronic expansion valve is in the fault state currently according to the obtained opening degree, the actual superheat degree and the preset superheat degree of the electronic expansion valve, outputs a control signal to the execution control mechanism according to the judgment result, controls the parameters of equipment influencing the actual superheat degree change in the vehicle air conditioning system by the execution control mechanism, and adjusts the superheat degree of the vehicle air conditioning system, so that the vehicle air conditioning system continues to operate in a normal performance or performance reduction mode without damaging the system.

Drawings

Fig. 1 is a block flow diagram showing a first embodiment of a control method of a vehicle air conditioning system according to the present invention;

FIG. 2 is a block flow diagram illustrating a fault handling process of a control method of the vehicle air conditioning system according to the present invention;

FIG. 3 is a block flow diagram illustrating a process of fault diagnosis for a control method of a vehicle air conditioning system according to the present invention;

FIG. 4 is a block flow diagram showing a second embodiment of a control method of a vehicle air conditioning system according to the present invention;

FIG. 5 is a block flow diagram showing a control method of a vehicle air conditioning system according to a third embodiment of the present invention;

FIG. 6 is a graph showing the relationship between the degree of superheat and control time obtained by comparing the control method of the air conditioning system for a vehicle according to the present invention with the prior art;

fig. 7 is a block diagram showing the construction of a first embodiment of the air conditioning system for a vehicle of the invention;

fig. 8 shows a block diagram of a second embodiment of the vehicular air conditioning system of the present invention.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

In the prior art, when an electronic expansion valve has a locked-rotor fault and is clamped at a certain position and cannot act, or when the electronic expansion valve has a fault and cannot be opened to a certain interval, the conventional vehicle air conditioning system cannot make a corresponding fault treatment countermeasure, so that the air conditioning system is damaged.

In view of the above disadvantages, the present invention provides a method for controlling a vehicle air conditioning system, which obtains a determination result of whether an electronic expansion valve is currently in a fault state according to an obtained opening degree of the electronic expansion valve, an actual superheat degree, and a preset superheat degree, outputs a control signal to an execution control mechanism according to the determination result, and controls parameters of equipment affecting actual superheat degree change in the vehicle air conditioning system by the execution control mechanism to adjust the superheat degree of the vehicle air conditioning system, so that the vehicle air conditioning system continues to operate in a normal performance or a performance-reducing mode without causing damage to the system.

Fig. 1 is a block flow diagram illustrating a first embodiment of a control method of an air conditioning system for a vehicle according to the present invention. The vehicle air conditioning system control method of the present invention includes:

s01, acquiring the opening degree, the actual superheat degree and the preset superheat degree of the electronic expansion valve in real time;

s02, judging whether the electronic expansion valve is in a fault state or not according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve, and performing effective fault diagnosis on the electronic expansion valve in real time in the superheat degree control process;

s03, when the judgment result shows that the electronic expansion valve is in a fault state, outputting a control signal to an execution control mechanism;

and S04, controlling and adjusting parameters of equipment influencing actual superheat degree change in the vehicle air conditioning system by using an execution control mechanism so as to adjust the superheat degree of the vehicle air conditioning system.

In this embodiment, the parameters of the device affecting the actual superheat change in the vehicle air conditioning system are preferably: speed or displacement C of the compressor₁Rotating speed C of evaporator fan₂. Of course, the parameters of the device that influence the actual superheat change may also include: the rotational speed of the condenser fan, etc.

In the above steps S03 and S04, when the electronic expansion valve is determined to be in the failure state as a result of the determination, as shown in fig. 2, the specific control steps are as follows:

s031, judge whether the actual superheat degree is less than the second and preserve the superheat degree, if, carry out step S041, otherwise, carry out step S032;

s032, judging whether the actual superheat degree is larger than a first preset superheat degree, if so, executing a step S042, otherwise, executing a step S043;

s041, increasing the speed or displacement C of compressor₁Or increasing the rotation speed C of the evaporator fan₂Or, alternatively, the compressor is turned off;

s042, reducing the rotating speed or the displacement C of the compressor₁Or, reducing the evaporator fan speed C₂Or, alternatively, the compressor is turned off;

s043, rotation speed or displacement C of compressor₁And the rotational speed C of the evaporator fan₂No adjustment is made.

In the above steps, the first preset superheat degree and the second preset superheat degree may be set according to actual conditions, where the second preset superheat degree is greater than the first preset superheat degree when the preset superheat degree is a range value, and the first preset superheat degree is equal to the second preset superheat degree when the preset superheat degree is a specific value.

As shown in fig. 2, in step S031, when the actual superheat degree is less than the preset superheat degree, the specific control steps are as follows:

s0311, judging whether the low pressure is lower than a low pressure alarm value, if so, executing a step S0314; otherwise, execute step S0312;

s0312, judging whether the high pressure is higher than the high pressure alarm value, if so, executing a step S0314, otherwise, executing a step S0313;

s0313, judge compressor rotational speed or discharge capacity C₁Whether or not at the highest value C_1max-Δ₃If yes, go to step S0314,otherwise, execute step S0411;

s0314, judge the rotational speed C of the evaporator fan₂Whether or not it is at the maximum value C_2max-Δ₄If yes, executing step S0413, otherwise, executing step S0412;

s0411, increasing the speed or displacement C of compressor₁；

S0412, increasing the fan rotating speed C of the evaporator₂；

S0413, closing the compressor.

In the above step,. DELTA.₃≥0、Δ₄Not less than 0 and Δ₃、Δ₄Can be set according to actual conditions to ensure safe operation of the compressor and the evaporator fan.

As shown in fig. 2, when the actual superheat degree is less than the preset superheat degree in step S032, the specific control steps are as follows:

s0321, judging the rotating speed or the displacement C of the compressor₁Whether or not it is at the minimum value C_1min+Δ₁If yes, executing step S0322, otherwise, executing step S0421;

s0322, judging rotating speed C of evaporator fan₂Whether or not it is at the minimum value C_2min+Δ₂If yes, go to step S0423, otherwise go to step S0422;

s0421, reducing the rotating speed or the displacement C of the compressor₁；

S0422, reducing the rotating speed C of the evaporator fan₂；

S0423, closing the compressor.

In the above step,. DELTA.₁≥0、Δ₂Not less than 0 and Δ₁、Δ₂Can be set according to actual conditions to ensure safe operation of the compressor and the evaporator fan.

The above control process is exemplified below. Supposing that the condition of locked-rotor occurs when the opening of the electronic expansion valve is 50%, and the flow required by the system is smaller than the flow which can be provided by the opening of the electronic expansion valve, the condition that the actual superheat degree is smaller than the preset superheat degree occurs, therefore, firstly, whether the low pressure of the system is lower than an alarm value and whether the high pressure is higher than the alarm value is judged, if the two conditions occur, the superheat degree cannot be controlled by increasing the rotating speed (or the discharge capacity) of the compressor, and because increasing the rotating speed (or the discharge capacity) of the compressor can further reduce the low pressure and increase the high pressure, the superheat degree can only be increased by increasing the rotating speed of an evaporator fan; if not, since changes in the evaporator fan speed can affect comfort in the passenger compartment, it is preferable to increase the compressor speed (or displacement) to increase superheat.

In addition, in the control process, if the current opening degree is larger than the actually required opening degree when the electronic expansion valve is locked, the refrigerating capacity generated by the vehicle air conditioning system is larger than the actually required opening degree, and the redundant refrigerating capacity can be neutralized by the heat of the heating core; when the current opening degree is smaller than the actually required opening degree when the electronic expansion valve is locked, the refrigerating capacity generated by the vehicle air conditioning system is lower than the required refrigerating capacity, and the system continues to perform a fault handling process.

According to the control method of the vehicle air conditioning system, when the valve fails, the rotating speed of the compressor and the fan of the evaporator can be adjusted, so that the system can continue to operate in a normal performance or performance reduction mode under the condition of keeping a reasonable superheat degree, the refrigeration effect can still be achieved in a carriage, the battery can still be cooled, and the system cannot be damaged.

The compressor here is in particular a variable frequency electric compressor.

In the present embodiment, as shown in fig. 3, step S02 is a process of accurately diagnosing a failure based on the relationship between the actual superheat degree and the preset superheat degree and the opening degree of the electronic expansion valve, and the process of determining the failure state is as follows:

s01, acquiring the opening degree, the actual superheat degree and the preset superheat degree of the electronic expansion valve;

s021, judging whether the preset superheat degree-actual superheat degree is larger than a first fixed value w1, if yes, executing a step S022; if not, go to step S025;

s022, judging whether the opening degree of the electronic expansion valve reaches the minimum value, if so, executing a step S023; if not, go to step S025;

s023, adding 1 to the error frequency n of the valve;

s024, judging whether the accumulated error times N in the first time length t1 are greater than or equal to a preset time N; if yes, determining that the current electronic expansion valve is in a fault state;

and S03, outputting a control signal to an actuating mechanism according to the judgment result.

In step S024, if the accumulated error number N of the electronic expansion valve is smaller than the preset number N by taking the first time length t1 as a period, it is determined that the electronic expansion valve is currently in a normal state, step S05 is executed, that is, the corresponding error report belongs to the influence of external factors, the accumulated error number N of the process parameters is cleared, and the next fault diagnosis period is entered.

That is, when the preset superheat degree is larger than the actual superheat degree, the valve performs an action of decreasing the opening degree tendency to raise the actual superheat degree to the preset superheat degree. Obviously, the steps S021 and S022 may determine that the superheat degree control is faulty when the preset superheat degree is greater than the actual superheat degree first fixed value w1 and the valve opening degree has reached the minimum value.

On the contrary, when the actual superheat degree is larger than the preset superheat degree, the valve performs an action of an opening degree increasing tendency to decrease the actual superheat degree to reach the preset superheat degree. Similarly, when the preset superheat is larger than the actual superheat second fixed value w2 at which the valve opening degree has reached the maximum value, it is determined that the superheat degree control is erroneous. As shown in fig. 2, the method specifically comprises the following steps:

s025, judging whether the actual superheat degree-preset superheat degree is larger than a second fixed value w2, if so, executing a step S026; if not, executing step S05, namely, correspondingly reporting errors belonging to the influence of external factors, clearing the accumulated error times n of the process parameters, and entering the next fault diagnosis period.

S026, judging whether the opening degree of the electronic expansion valve reaches the maximum value, if so, executing a step S023, and adding 1 to the valve error frequency n; if the two error times N are greater than or equal to the predetermined times N within the first time period t1, step S03 is executed, and a control signal is output to the actuator according to the determination result. If not, go to step S05.

In addition, the automobile needs to work within the limit working condition range of the design of the refrigeration system, for example, the automobile works in special working conditions that the outdoor temperature of the automobile exceeds the limit temperature of the design of the refrigeration system of the automobile. Under the influence of the special working conditions, the error reporting phenomenon often occurs on the working parameters of the refrigeration system, and obviously, the accuracy of fault diagnosis in the control method of the scheme is directly influenced by the interference of external factors outside various limit working condition ranges. For this reason, a determination step S0 as to whether to process within the limit operating condition range may be added before step S01. As shown in particular in figure 3.

S0., determining whether the electronic expansion valve is in the limit condition range. If not, executing step S01 to perform fault diagnosis; if yes, entering the next fault diagnosis period, namely stopping executing the subsequent fault diagnosis steps so as to avoid the problem of error reporting under an abnormal state.

Of course, the process of determining the fault state of the electronic expansion valve may also adopt other manners.

In addition, in the prior art, in the household and commercial air conditioning system adopting the electronic expansion valve as the throttling element, the control method of the superheat degree is realized by adopting the actual superheat degree as a PID input parameter to control the opening degree of the electronic expansion valve, and the problems of slow response speed, easy overshoot, low system efficiency, liquid sluggish of the compressor and the like exist. In order to solve the technical problem, the method of the invention adopts a feed-forward strategy to control the degree of superheat, namely: besides, the actual superheat degree is used as a PID input parameter to control the opening degree of the electronic expansion valve, the opening degree of the electronic expansion valve is also controlled according to the pre-feedback information acquired in real time, the response speed is high, and the superheat degree is controlled more stably.

Here, the feedforward is first explained as follows:

the feedforward is that the control output of the system is not only related to the change of the controlled object parameter, but also related to disturbance factors influencing the change of the controlled object parameter, such as: the opening degree control of the electronic expansion valve is not only related to the change of the actual superheat degree, but also related to other parameters in the vehicle air conditioning system which affect the change of the actual superheat degree and react more timely than the actual superheat degree when the working condition changes, therefore, the system can be adjusted before the controlled object (the actual superheat degree) is affected when the working condition changes through a front feedback control strategy, and better control quality is achieved.

Referring to fig. 4, in conjunction with the above description, in a second embodiment of the method of the present invention, the superheat control process includes the following steps:

s1, acquiring an actual superheat degree and a preset superheat degree in real time, and acquiring feed-forward information influencing actual superheat degree change in real time;

and S2, adjusting the opening degree of the electronic expansion valve in real time according to the obtained actual superheat degree, the preset superheat degree and the front feedback information so as to control the superheat degree of the vehicle air conditioning system.

The following explains which feedforward information affecting the actual superheat change may include in the vehicle air conditioning system:

generally, a vehicle air conditioning system mainly comprises a compressor, a condenser, a throttling element and an evaporator, and when the vehicle air conditioning system is in a stable working condition, the rotating speed of the compressor (for a displacement compressor, the displacement of the compressor), the rotating speed of a fan of the evaporator, the external temperature of a vehicle, the internal temperature of the vehicle and the opening degree of an electronic expansion valve are all in a stable state. At a certain moment, when the external environment exerts a disturbance on the vehicle air conditioning system, for example: in the case where the vehicle is driven from a shade of a tree or a tunnel to the sun, and the like, the operating condition changes, and the temperature in the vehicle suddenly rises, the temperature of the evaporator rises, the evaporation pressure rises, and the rotation speed of the compressor gradually increases (for the variable displacement compressor, the displacement of the compressor is increased) to reach the set outlet air temperature, and the rotation speed of the evaporator fan increases. In brief, when the working condition changes, the rotation speed (displacement) of the compressor is increased, the rotation speed of the fan of the evaporator is increased, the actual superheat degree is increased, and vice versa, and in order to enable the refrigerating system to have larger flow, the opening degree of the electronic expansion valve needs to be continuously increased, so that the actual superheat degree returns to the set value.

In the whole process, after the working condition changes, the rotating speed of the fan of the evaporator, the rotating speed or the discharge capacity of the compressor are increased for a period of time (generally 5-10 seconds, which is determined according to the sensitivity of the pressure sensor and the temperature sensor for obtaining the actual superheat degree), and then the pressure sensor and the temperature sensor can know that the actual superheat degree is increased, so that the opening degree of the electronic expansion valve is adjusted.

Therefore, in the present invention, the feed-forward information is preferably: information on the variation of the speed of the compressor (for a variable displacement compressor, the displacement of the compressor), and/or information on the variation of the speed of the evaporator fan.

Of course, according to the above whole process and by combining the working principle of the air conditioning system, the feed-forward information may further include: the rotational speed of the condenser fan.

Of course, according to the above whole process and combining the working principle of the air conditioning system, the front feedback information may also include the rotation speed of the condenser fan.

Referring to fig. 5, fig. 5 is a flowchart illustrating a third embodiment of the method of the present invention.

As shown in fig. 5, when the feed-forward information is the rotational speed variation of the compressor, the method for controlling the superheat degree of the vehicle air conditioning system specifically comprises the following steps:

s11, acquiring actual superheat degree, preset superheat degree and rotation speed change information of a compressor in real time;

s21, comparing the obtained actual superheat degree with a preset superheat degree to obtain a superheat degree difference value, and obtaining a corresponding opening degree regulating quantity V of the first electronic expansion valve according to the superheat degree difference value_out1; specifically, when the opening degree of the electronic expansion valve is controlled by the actual superheat degree, the opening degree adjustment amount V of the first electronic expansion valve is controlled in accordance with the same PID control principle as that of the electronic expansion valve of the household air conditioner_out1 can be calculated according to the following:

$V_{\mathrm{out}}1=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt},$

wherein e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a proportionality coefficient, K_dIs a differential coefficient, K_iIs an integral coefficient;

wherein the proportionality coefficient K_pDifferential coefficient K_dAnd integral coefficient K_iIs a coefficient obtained by experimental debugging.

S22, acquiring corresponding opening adjusting quantity V of the second electronic expansion valve according to the acquired rotating speed change information of the compressor _out2; specifically, when the opening degree of the electronic expansion valve is adjusted through the information of the rotation speed change of the compressor, the control principle is similar to a differential link, the rotation speed of the compressor changes with time to form a corresponding function CS (t), and the output value at a certain time t0 is

The second electronic expansion valve opening degree adjustment amount V _out2 can be calculated as follows:

$V_{\mathrm{out}}2=K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}},$

in the formula, K_CSThe feedback coefficient of the compressor is, and CS is the rotating speed variation of the compressor;

wherein the feedback coefficient K of the compressor_CSIs a coefficient obtained by experimental debugging.

S23, adjusting the opening degree V of the first electronic expansion valve_out1 and the opening regulating quantity V of the second electronic expansion valve _out2, outputting a control signal for adjusting the opening degree to the control end of the electronic expansion valve to control the opening degree of the electronic expansion valve, i.e. the opening degree adjustment quantity V of the electronic expansion valve_outThis can be calculated as follows:

$V_{\mathrm{out}}=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}+K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}},$

wherein e is the difference between the actual superheat degree and the preset superheat degree, K_pIs a proportionality coefficient, K_dIs a differential coefficient, K_iIs the integral coefficient, K_CSAnd CS is a compressor speed variation.

Further, for the scaling factor K in the above-described step S21_pDifferential coefficient K_dAnd integral coefficient K_iThe compressor feedback coefficient K in the step S22_CSCan be obtained by experimental debugging.

When the compressor is a variable displacement compressor, in the above control method, the amount of change in the rotational speed of the compressor is accordingly the amount of change in the displacement of the compressor.

A fourth embodiment of the method of the present invention is provided below, and different from the third embodiment, the front feedback information in this embodiment is rotation speed variation information of an evaporator fan, and the specific steps are as follows:

s11', acquiring the actual superheat degree, the preset superheat degree and the rotating speed change information of an evaporator fan in real time;

s21', comparing the obtained actual superheat degree with a preset superheat degree to obtain a superheat degree difference value, and obtaining a corresponding opening degree regulating quantity V of the first electronic expansion valve according to the superheat degree difference value_out1; specifically, the opening degree adjustment amount V of the first electronic expansion valve_out1 can be calculated from:

$V_{\mathrm{out}}1=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt},$

wherein e is the difference between the actual superheat degree and the preset superheat degree, K_pIs a proportionality coefficient, K_dIs a differential coefficient, K_iIs an integral coefficient; wherein the proportionality coefficient K_pDifferential coefficient K_dAnd integral coefficient K_iIs a coefficient obtained by experimental debugging.

S22', acquiring the corresponding opening degree regulating quantity V of the second electronic expansion valve according to the acquired rotating speed change information of the evaporator fan _out2; specifically, the second electronic expansion valve opening degree adjustment amount V _out2 can be calculated as follows:

$V_{\mathrm{out}}2=K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}},$

in the formula, BS is the variation of the fan rotating speed of the evaporator, K_BSIs the evaporator fan feedback coefficient; wherein, the feedback coefficient K of the evaporator fan_BSIs a coefficient obtained by experimental debugging.

S23', adjusting the opening degree of the first electronic expansion valve by an amount V_out1 and the opening regulating quantity V of the second electronic expansion valve _out2, outputting a control signal for adjusting the opening degree to the control end of the electronic expansion valve to control the opening degree of the electronic expansion valve, i.e. the opening degree adjustment quantity V of the electronic expansion valve_outThis can be calculated as follows:

$V_{\mathrm{out}}=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}+K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}}.$

wherein, in the above step, the proportionality coefficient K_pDifferential coefficient K_dAnd integral coefficient K_iFeedback coefficient K of evaporator fan_BSCan be obtained by an experimental debugging method.

A fifth embodiment of the present invention is provided below, which is different from the third and fourth embodiments in that the feed-forward information includes information about a change in the rotational speed of the evaporator fan and information about a change in the rotational speed of the compressor fan, and the specific control steps are as follows:

s11 '' obtaining the actual superheat degree, the preset superheat degree, the rotating speed change information of the evaporator fan and the rotating speed change information of the compressor in real time;

s21 '' comparing the actual superheat obtainedObtaining a superheat difference value between the degree and a preset superheat degree, and obtaining a corresponding opening degree regulating quantity V of the first electronic expansion valve according to the superheat degree difference value_out1；

Specifically, the opening degree adjustment amount V of the first electronic expansion valve_out1 can be calculated from:

$V_{\mathrm{out}}1=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt},$

wherein e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a proportionality coefficient, K_dIs a differential coefficient, K_iIs an integral coefficient;

wherein the proportionality coefficient K_pDifferential coefficient K_dAnd integral coefficient K_iIs a coefficient obtained by experimental debugging.

S22 '', according to the obtained rotation speed change information of the evaporator fan, obtaining the corresponding opening degree regulating quantity V of the second electronic expansion valve _out2；

Specifically, the second electronic expansion valve opening degree adjustment amount V _out2 can be calculated as follows:

$V_{\mathrm{out}}2=K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}}+K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}},$

in the formula, K_CSIs the feedback coefficient of the compressor, CS is the variation of the rotating speed of the compressor,

wherein BS is the variation of the fan speed of the evaporator, K_BSIs the evaporator fan feedback coefficient;

compressor feedback coefficient K_CSFeedback coefficient K of evaporator fan_BSIs a coefficient obtained by experimental debugging.

S23 '' adjusting the opening degree of the first electronic expansion valve by an amount V_out1 and the opening regulating quantity V of the second electronic expansion valve _out2, outputting a control signal for adjusting the opening degree to the control end of the electronic expansion valve to control the opening degree of the electronic expansion valve, i.e. the opening degree adjustment quantity V of the electronic expansion valve_outThis can be calculated as follows:

$V_{\mathrm{out}}=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}+K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}}+K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}}.$

wherein, in the above step, the proportionality coefficient K_pDifferential coefficient K_dIntegral coefficient K_iAnd a compressor feedback coefficient K_CSFeedback coefficient K of evaporator fan_BSCan be obtained by an experimental debugging method.

The superheat control process in the method of the invention is illustrated by way of a specific example:

when an automobile enters the tunnel from the tunnel and is exposed to sunlight in the advancing process, the temperature in the automobile is suddenly increased, so that the temperature of an evaporator is increased, the evaporation pressure is increased, the rotating speed of a compressor is increased according to the set outlet air temperature, a controller immediately acquires the rotating speed change information of the compressor and immediately pre-adjusts the opening degree of an electronic expansion valve; the actual superheat degree is improved due to the fact that the rotating speed of the compressor is improved, the controller obtains the actual superheat degree, the superheat degree difference e changes, and the opening degree of the electronic expansion valve is adjusted; therefore, the opening degree of the electronic expansion valve is increased, more refrigerant flow is brought to the system, the refrigerating capacity is gradually increased, the temperature in the carriage is gradually reduced and returns to the vicinity of the preset superheat degree, the disturbance is eliminated, the rotating speed of the compressor is not increased any more and tends to a certain rotating speed, and the opening degree of the electronic expansion valve is not increased any more and tends to a certain opening degree gradually.

In the process, the opening degree of the electronic expansion valve is controlled and adjusted immediately after the rotating speed of the compressor changes, and compared with the method that the opening degree of the electronic expansion valve is adjusted after the actual superheat degree signal is obtained by a temperature sensor of a pressure sensor, the response speed is greatly improved, and the system fluctuation is smaller.

Similarly, when the fan speed of the evaporator is increased, the heat exchange efficiency of the evaporator is improved, the temperature of the refrigerant is increased, the actual superheat degree is also improved, the opening degree of the electronic expansion valve is immediately adjusted after the rotating speed of the fan of the evaporator is changed, and compared with the method that the temperature sensor and the pressure sensor obtain actual superheat degree signals and then adjust the opening degree of the electronic expansion valve, the response speed is greatly improved, and the system fluctuation is smaller.

Fig. 6 is a graph showing the relationship between the degree of superheat and the control time of the system obtained by comparing the method of the present invention with the method of controlling the degree of superheat using only the actual degree of superheat to control the opening degree of the electronic expansion valve as a comparison method. Wherein the curve a represents the superheat degree versus control time curve of the method of the invention, and the curve b represents the superheat degree versus control time curve of the comparative method. As can be seen from the curves a and b in FIG. 3, when the superheat degree is controlled by the method of the present invention, the fluctuation range of the actual superheat degree is small, and the control time is short, whereas when the superheat degree is controlled by using the contrast direction, the fluctuation range of the actual superheat degree is large, and the control time is long. That is to say, the method of the invention adopts the feedforward strategy to control the superheat degree, and can immediately obtain the disturbance magnitude and the change direction when the system compressor or fan rotating speed changes, so as to predict the change of the actual superheat degree in advance.

In addition, the valve needle of the electronic expansion valve is operated in a different manner from that of the thermal expansion valve, in which a stepping motor is used to drive the valve needle to rotate along a thread, and the valve needle can be raised or lowered by one thread pitch every time the valve needle rotates by one revolution, so as to achieve the purpose of moving the valve needle to control the opening degree of the valve needle. The rotating speed of the stepping motor is limited by the performance of the solenoid and the controller, so that the moving speed of the thermostatic expansion valve can not be achieved generally. Assuming that the speed of the stepping motor is 80pps and the entire stroke of the valve wire package is 480 steps, the electronic expansion valve needs 6 seconds to be opened from the fully closed state to the fully opened state.

Therefore, in order to optimize the control of the system on the degree of superheat, the change rate of the rotating speed of the compressor and the fan of the evaporator cannot be too high, so that the change rate of the opening degree of the electronic expansion valve cannot follow up, and the degree of superheat of the vehicle air conditioning system is not adjusted.

Therefore, the opening degree adjustment amount of the second electronic expansion valve should not exceed the maximum change rate of the opening degree of the electronic expansion valve, that is, when the rotation speed of the compressor or the rotation speed of the fan of the evaporator changes, the feedback value corresponding to the change speed does not exceed the action speed of the electronic expansion valve, and then the maximum change rate of the rotation speed or the displacement of the compressor is calculated by the following method:

$\frac{\mathrm{dCS}}{\mathrm{dt}}\max =\frac{\mathrm{dVout}\left(t\right)}{\mathrm{dt}}\max /K_{\mathrm{CS}},$

wherein,is the maximum rate of change of the opening degree of the electronic expansion valve.

In the same way, the maximum change rate of the rotating speed of the fan of the evaporator is as follows:

$\frac{\mathrm{dBS}}{\mathrm{dt}}\max =\frac{\mathrm{dVout}\left(t\right)}{\mathrm{dt}}\max /K_{\mathrm{BS}},$

wherein,

is the maximum rate of change of the opening degree of the electronic expansion valve.

In addition, it should be noted that, in the method of the present invention, a pressure sensor may be used to obtain the rotation speed of the compressor or the rotation speed of the evaporator fan, after the vehicle air conditioning system stops operating for a long time, at the initial stage of first start, the system has not yet performed a stable operating condition, because the reaction speed of the pressure sensor is faster than that of the temperature sensor, the pressure will decrease faster than the temperature, so that the superheat degree will rapidly increase at the initial stage of operation, and the calculated opening degree of the electronic expansion valve is greater than the actually required opening degree, which may cause an excessive flow of the system and an overload due to an excessive current of the compressor. Therefore, in the case where the compressor is stopped for more than 5 minutes, the speed at the time of restart is not more than 50% of the maximum rotation speed for 15 seconds, and then the normal control is resumed.

The limitation on the rotating speed of the compressor and the rotating speed change speed of the evaporator fan and the limitation on the compressor when the system is started can better protect an air conditioning system of a vehicle and improve the control precision of the superheat degree.

As shown in fig. 7, the present invention further provides a vehicle air conditioning system, which includes a compressor unit and a throttling element, wherein the compressor unit includes a compressor, a condenser fan, an evaporator and an evaporator fan, the throttling element is an electronic expansion valve, and the vehicle air conditioning system further includes:

the first acquisition module 3 is used for acquiring the opening degree of the electronic expansion valve in real time;

the first controller 4 is used for judging whether the electronic expansion valve is in a fault state according to the acquired actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve, and generating a first control signal according to the acquired actual superheat degree when the electronic expansion valve is in the fault state according to the judgment result;

an execution control mechanism 5 for receiving the first control sent by the first controller 4And controlling and adjusting parameters of equipment influencing the actual superheat degree change in the vehicle air conditioning system according to the first control signal, wherein the parameters of the equipment influencing the actual superheat degree change in the vehicle air conditioning system comprise the rotating speed or the discharge capacity C of a compressor₁And/or the rotational speed C of the evaporator fan₂。

In this embodiment, the first acquisition module 3 communicates with the second controller 2 through a vehicle CAN bus or a LIN bus; the first controller 4 and the electronic expansion valve are communicated through a CAN bus or a LIN bus of the vehicle.

In the present embodiment, the execution control means 5 is preferably an on-vehicle controller ECU.

Wherein the first controller 4 includes:

the judging module 41 is configured to judge whether the electronic expansion valve is in a fault state according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve, and generate a first control command when the judging result indicates that the electronic expansion valve is in the fault state;

a first control module 42, configured to receive the first control command sent by the determining module 41, and control the execution control mechanism 5 to execute the reduction of the rotation speed or the displacement C of the compressor when the actual superheat degree is greater than a first preset superheat degree₁Or reducing the rotating speed C of the evaporator fan₂Or a command to shut down the compressor;

a second control module 43, configured to receive the first control command sent by the determining module 41, and control the execution control mechanism 5 to execute the operation of increasing the rotation speed or the displacement C of the compressor when the actual superheat degree is less than a second preset superheat degree₁Or increasing the rotating speed C of the fan of the evaporator₂Or a command to shut down the compressor;

a third control module 44, configured to receive the first control command sent by the determining module 41, and control the execution control mechanism 5 to execute the operation of maintaining the rotation speed or the discharge speed of the compressor when the actual superheat degree is greater than or equal to the second preset superheat degree and less than or equal to the first preset superheat degreeQuantity C₁Or increasing the rotating speed C of the fan of the evaporator₂An unchanging command.

Wherein the first control module 42 includes:

a first command module 421 for commanding the speed or displacement C of the compressor₁Greater than a minimum value C_1min+Δ₁When the compressor is stopped, the control execution mechanism 5 is controlled to execute the reduction of the rotating speed or the displacement C of the compressor₁A command of (2);

a second command module 422 for controlling the speed or displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotating speed C of the evaporator fan₂Greater than a minimum value C_2min+Δ₂In time, the execution control mechanism 5 is controlled to execute the reduction of the rotating speed C of the evaporator fan₂A command of (2);

a third command module 423 for controlling the speed or displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂To a minimum value C_2min+Δ₂When the compressor is started, the execution control mechanism 5 is controlled to execute a command for closing the compressor;

wherein the second control module 43 comprises:

a fourth command module 431 for commanding the speed or displacement C of the compressor when the low pressure of the vehicle air conditioning system is higher than the low pressure warning value and the high pressure is lower than the high pressure warning value₁Less than a maximum value C_1max-Δ₃When the rotation speed or the displacement C of the compressor is increased, the execution control mechanism 5 is controlled to execute₁A command of (2);

a fifth command module 432, configured to set a rotation speed C of an evaporator fan when a low pressure of the vehicle air conditioning system is lower than a low pressure warning value or a high pressure is higher than a high pressure warning value₂Less than a maximum value C_2max-Δ₄In time, the execution control mechanism 5 is controlled to execute the increase of the rotating speed C of the evaporator fan₂A command of (2);

a sixth command module 433 for under Low pressure for vehicle air Conditioning SystemThe pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂To a maximum value C_2max-Δ₄And controls the execution control means 5 to execute a command to shut down the compressor.

In addition, the first controller 4 further includes a hardware diagnosis module for diagnosing a hardware fault, which is used to detect a driving current and a driving voltage and to acquire fault information such as an open circuit, a short circuit, and a step loss.

In this embodiment, a second embodiment of the air conditioning system for a vehicle according to the present invention is shown in fig. 8. In this embodiment, the vehicle air conditioning system further includes:

the second acquisition module 1 is used for acquiring the actual superheat degree and feed-forward information influencing the actual superheat degree change in real time;

and the second controller 2 is used for storing the preset superheat degree, receiving the actual superheat degree and the pre-feedback information, and adjusting the opening degree of the electronic expansion valve in real time according to the actual superheat degree, the preset superheat degree and the pre-feedback information.

Compared with the prior art, the vehicle air conditioning system can immediately obtain the size and the change direction of disturbance when the system is disturbed, so that the change of the superheat degree is predicted in advance.

Preferably, the pre-feedback information acquired by the second acquiring module 1 includes: the amount of change in the speed or displacement of the compressor; and/or the variation of the rotating speed of the fan of the evaporator.

The second obtaining module 1 includes an acquiring module for obtaining the variation information of the rotating speed (displacement) of the compressor and/or the variation information of the rotating speed of the fan of the evaporator, and a temperature sensor for obtaining the temperature of the inlet and the outlet of the evaporator, wherein the acquiring module can select the rotating speed sensor or the pressure sensor, etc.

In this embodiment, preferably, the second controller 2 communicates with the electronic expansion valve through a CAN bus or a LIN bus of the vehicle; the second acquisition module 1 communicates with the second controller 2 through a vehicle CAN bus or a LIN bus.

As shown in fig. 7, the second controller 2 includes:

the PID control module 21 is used for storing a preset superheat degree, comparing the received actual superheat degree with the preset superheat degree to obtain a superheat degree difference value, and acquiring a corresponding opening degree regulating quantity of the first electronic expansion valve according to the superheat degree difference value;

the front feedback control module 22 is configured to obtain a corresponding opening adjustment amount of the second electronic expansion valve according to the received rotation speed or displacement variation of the compressor and/or the rotation speed variation of the evaporator fan; and the number of the first and second groups,

and the execution control module 23 is configured to actually control and adjust the opening of the electronic expansion valve according to the first electronic expansion valve opening adjustment amount and the second electronic expansion valve opening adjustment amount.

Wherein, the PID control module 21 obtains the opening degree regulating quantity V of the first electronic expansion valve by the following calculation_out1：

$V_{\mathrm{out}}1=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt},$

Wherein e is a superheat difference, K_pIs a proportionality coefficient, K_dIs a differential coefficient, K_iIs an integral coefficient;

the feedback control module 22 obtains the output value V of the second electronic expansion valve by the following calculation_out2：

$V_{\mathrm{out}}2=K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}},$ Or $V_{\mathrm{out}}2=K_{\mathrm{CS}}\×\frac{\mathrm{dCS}}{\mathrm{dt}}+K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}},$ Or $V_{\mathrm{out}}2=K_{\mathrm{BS}}\×\frac{\mathrm{dBS}}{\mathrm{dt}},$

In the formula, K_CSIs the feedback coefficient of the compressor, CS is the variation of the compressor speed or displacement, BS is the variation of the evaporator fan speed, K_BSIs the evaporator fan feedback coefficient;

the opening degree of the first electronic expansion valve is adjusted by an adjusting amount V in the execution control module 23_out1 and the opening regulating quantity V of the second electronic expansion valve _out2, outputting a control signal for adjusting the opening degree to the control end of the electronic expansion valve after accumulation.

In this embodiment, the first controller 4 and the second controller 2 may be integrated on one chip.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (13)

1. A control method of a vehicle air conditioning system, characterized in that the method comprises:

acquiring an actual superheat degree, a preset superheat degree and an opening degree of an electronic expansion valve;

judging whether the electronic expansion valve is in a fault state or not according to the acquired actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve;

when the judgment result shows that the electronic expansion valve is in a fault state, outputting a control signal to an execution control mechanism;

the execution control mechanism controls and adjusts parameters of equipment influencing actual superheat degree change in the vehicle air conditioning system so as to adjust the superheat degree of the vehicle air conditioning system.

2. The control method of a vehicular air-conditioning system according to claim 1, characterized in that the parameters of the devices that influence the actual superheat degree variation in the vehicular air-conditioning system include: speed or displacement C of the compressor₁And/or the rotational speed C of the evaporator fan₂。

3. The control method of a vehicular air conditioning system according to claim 2, characterized in that, on the premise that the electronic expansion valve is in a failure state as a result of the judgment,

when the actual superheat degree is larger than the first preset superheat degree, a control signal is output to the execution control mechanism, and the execution control mechanism controls to reduce the rotating speed or the discharge capacity C of the compressor₁Or reducing the rotating speed C of the evaporator fan₂Or turning off the compressor;

when the actual superheat degree is less than a second preset superheat degree, a control signal is output to the execution control mechanism, and the execution control mechanism controls and increases the rotating speed or the discharge capacity C of the compressor₁Or increasing the rotating speed C of the fan of the evaporator₂Or turning off the compressor; and the number of the first and second groups,

when the actual superheat degree is more than or equal to a second preset superheat degree and less than or equal to a first preset superheat degree, a control signal is output to an execution control mechanism, and the execution control mechanism controls the rotating speed or the discharge capacity C of the compressor₁And the rotational speed C of the evaporator fan₂Remain unchanged.

4. The control method of a vehicle air conditioning system according to claim 3, characterized in that: on the premise that the actual superheat degree is larger than the first preset superheat degree,

when the compressor speed or displacement C₁Greater than a minimum value C_1min+Δ₁Outputting control signal to the executing control mechanism, and controlling to reduce the rotation speed or discharge C of the compressor by the executing control mechanism₁，

When the compressor speed or displacement C₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂Greater than a minimum value C_2min+Δ₂When the evaporator fan is started, a control signal is output to an execution control mechanism, and the execution control mechanism controls and reduces the rotating speed C of the evaporator fan₂，

When the compressor speed or displacement C₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂To a minimum value C_2min+Δ₂When the compressor is started, a control signal is output to the execution control mechanism, and the execution control mechanism controls the compressor to be closed;

on the premise that the actual superheat degree is less than the second preset superheat degree,

when the low pressure of the vehicle air conditioning system is higher than the low pressure alarm value and the high pressure is lower than the high pressure alarm value, and the rotating speed or the discharge capacity C of the compressor₁Less than a maximum value C_1max-Δ₃When the compressor is started, the control signal is output to the executing control mechanism, and the executing control mechanism controls and increases the rotating speed or the discharge capacity C of the compressor₁；

When the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂Less than a maximum value C_2max-Δ₄When the evaporator fan is started, a control signal is output to an execution control mechanism, and the execution control mechanism controls and increases the rotating speed C of the evaporator fan₂；

When the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂To a maximum value C_2max-Δ₄And when the compressor is started, the control signal is output to the execution control mechanism, and the execution control mechanism controls the compressor to be closed.

5. The control method of a vehicular air conditioning system according to any one of claims 2 to 4, characterized in that the rotation speed or the displacement C of the compressor₁Or the rotating speed C of the evaporator fan₂Obtained according to the following calculations:

$C=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}$

in the formula,

c is the speed or displacement C of the compressor₁Or the rotational speed C of the evaporator fan₂，

e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a coefficient of proportionality that is,

K_din order to be the differential coefficient,

K_iis an integral coefficient.

6. The control method of a vehicle air conditioning system according to claim 1, characterized by further comprising:

acquiring the actual superheat degree and the preset superheat degree, and acquiring feed-forward information influencing the actual superheat degree change in real time;

adjusting the opening degree of an electronic expansion valve in real time according to the obtained actual superheat degree, the preset superheat degree and feed-forward information to control the superheat degree of a vehicle air conditioning system, wherein the feed-forward information comprises the rotating speed or displacement variable quantity of a compressor; and/or the rotating speed variation of the evaporator fan.

7. A vehicle air conditioning system comprising a compressor unit and a throttling element, the compressor unit comprising a compressor, a condenser, an evaporator and an evaporator fan, characterized in that the throttling element comprises an electronic expansion valve;

the vehicle air conditioning system further includes:

the first acquisition module is used for acquiring the actual superheat degree and the opening degree of the electronic expansion valve in real time;

the first controller is used for storing a preset superheat degree, receiving an actual superheat degree and the opening degree of the electronic expansion valve, judging whether the electronic expansion valve is in a fault state or not according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve, and generating a first control signal according to the acquired actual superheat degree when the electronic expansion valve is in the fault state according to a judgment result;

and the execution control mechanism is used for receiving the first control signal sent by the first controller and controlling and adjusting parameters of equipment influencing the actual superheat degree change in the vehicle air conditioning system according to the first control signal.

8. A vehicle air conditioning system as set forth in claim 7, characterized in that the parameters of the devices affecting the actual superheat degree variation in the vehicle air conditioning system include:

speed or displacement C of the compressor₁And/or the rotational speed C of the evaporator fan₂。

9. The vehicle air conditioning system of claim 8, wherein the first controller comprises:

the judging module is used for judging whether the electronic expansion valve is in a fault state or not according to the actual superheat degree, the preset superheat degree and the opening degree of the electronic expansion valve and generating a first control command when the judging result shows that the electronic expansion valve is in the fault state;

the first control module is used for receiving the first control command sent by the judging module and controlling the execution control mechanism to execute the reduction of the rotating speed or the discharge capacity C of the compressor when the actual superheat degree is greater than a first preset superheat degree₁Or reducing the rotating speed C of the evaporator fan₂Or a command to shut down the compressor;

the second control module is used for receiving the first control command sent by the judging module and is used for receiving the first control command when the actual superheat degree is less than a second preset superheat degreeControlling the actuating control mechanism to increase the rotating speed or the displacement C of the compressor₁Or increasing the rotating speed C of the fan of the evaporator₂Or a command to shut down the compressor;

a third control module for receiving the first control command sent by the judging module and controlling the execution control mechanism to execute and maintain the rotating speed or the discharge capacity C of the compressor when the actual superheat degree is more than or equal to a second preset superheat degree and less than or equal to a first preset superheat degree₁Or increasing the rotating speed C of the fan of the evaporator₂An unchanging command.

10. The control method of a vehicle air conditioning system according to claim 9, characterized in that the first control module includes:

a first command module for commanding the speed or the displacement C of the compressor₁Greater than a minimum value C_1min+Δ₁When the compressor is in the normal state, the execution control mechanism is controlled to execute the reduction of the rotating speed or the displacement C of the compressor₁A command of (2);

a second command module for controlling the speed or the displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotating speed C of the evaporator fan₂Greater than a minimum value C_2min+Δ₂When the evaporator is started, the execution control mechanism is controlled to execute the reduction of the rotating speed C of the evaporator fan₂A command of (2);

a third command module for controlling the speed or the displacement C of the compressor₁To a minimum value C_1min+Δ₁And the rotation speed C of the evaporator fan₂To a minimum value C_2min+Δ₂When the compressor is started, the execution control mechanism is controlled to execute a command of closing the compressor;

the second control module includes:

a fourth command module for controlling the rotation speed or displacement C of the compressor when the low pressure of the vehicle air conditioning system is higher than the low pressure warning value and the high pressure is lower than the high pressure warning value₁Less than a maximum value C_1max-Δ₃When the compressor is started, the execution control mechanism is controlled to execute the operation of increasing the rotating speed or the discharge capacity C of the compressor₁A command of (2);

a fifth command module for controlling the rotation speed C of the evaporator fan when the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value₂Less than a maximum value C_2max-Δ₄When the evaporator is started, the execution control mechanism is controlled to execute the operation of increasing the rotating speed C of the fan of the evaporator₂A command of (2);

a sixth command module for indicating whether the low pressure of the vehicle air conditioning system is lower than the low pressure alarm value or the high pressure is higher than the high pressure alarm value and the rotating speed C of the evaporator fan₂To a maximum value C_2max-Δ₄And controlling the execution control mechanism to execute a command of closing the compressor.

11. A vehicle air conditioning system according to any of claims 7 to 10, characterized in that the rotational speed or displacement of the compressor, or the rotational speed of the evaporator fan is obtained according to the following calculation:

$C=K_p\×e+K_d\×\frac{\mathrm{de}}{\mathrm{dt}}+K_i\×{\∫}_n^t\mathrm{edt}$

in the formula,

c is the speed or displacement C of the compressor₁Or the rotational speed C of the evaporator fan₂，

e is the difference value of the actual superheat degree and the preset superheat degree,

K_pis a coefficient of proportionality that is,

K_din order to be the differential coefficient,

K_iis an integral coefficient.

12. The vehicle air conditioning system of claim 11, further comprising:

the second acquisition module is used for acquiring feed-forward information influencing the actual superheat degree change in real time;

and the second controller is used for storing a preset superheat degree, receiving an actual superheat degree and feed-forward information, and adjusting the opening degree of the electronic expansion valve in real time according to the actual superheat degree, the preset superheat degree and the feed-forward information, wherein the feed-forward information comprises the rotating speed or displacement variation of the compressor and/or the rotating speed variation of the evaporator fan.

13. A vehicle air conditioning system according to claim 12, characterized in that: the first acquisition module and the second acquisition module are communicated with the second controller through a vehicle CAN bus or a LIN bus; the first controller, the second controller and the electronic expansion valve are communicated through a CAN bus or a LIN bus of the vehicle.

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