A method for controlling a refrigeration system of a vehicle

Abstract

A method for controlling a refrigeration system (1) of a vehicle is provided. The refrigeration system (1) comprises a circuit (2) containing a refrigerant; a compressor (3); a first evaporator (4) and a second evaporator (5) connected in parallel to the compressor; a first expansion valve (9) arranged upstream of the first evaporator, which regulates a pressure drop of the refrigerant before the first evaporator; a second expansion valve (10) arranged upstream of the second evaporator, which regulates a pressure drop of the refrigerant before the second evaporator; and a condenser (11) arranged downstream of the compressor between the compressor (3) and the first and second expansion valves. The method comprises controlling a total opening degree of the first expansion valve (9) and the second expansion valve (10) based on a temperature and a pressure of the refrigerant, the refrigerant temperature and the refrigerant pressure being measured downstream of the first and second evaporators at a location between the first and second evaporators and the compressor.

Description

Technical Field

[0001] The present invention relates to a method and a control unit for controlling a vehicle's refrigeration system. Background Technology

[0002] Electric vehicles and plug-in hybrid electric vehicles typically have a refrigeration system with two evaporators connected in parallel to the compressor. This system is used for HVAC functions and for cooling the battery and motor.

[0003] Depending on the various cooling requirements and available secondary fluid flows, a different distribution of cooling power is desired among the evaporators. At the same time, the necessary superheat level of the refrigerant flowing to the compressor inlet must be ensured. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling a vehicle's refrigeration system, by which the superheat level of the refrigerant can be ensured, and at the same time the desired cooling power distribution between the two evaporators of the system can be achieved.

[0005] This objective is achieved through a method for controlling a vehicle's refrigeration system. The refrigeration system includes: a circuit for containing refrigerant; a compressor; a first evaporator and a second evaporator connected in parallel to the compressor; a first expansion valve disposed upstream of the first evaporator, the first expansion valve regulating the pressure drop of the refrigerant before the first evaporator; a second expansion valve disposed upstream of the second evaporator, the second expansion valve regulating the pressure drop of the refrigerant before the second evaporator; and a condenser disposed downstream of the compressor between the compressor and the first and second expansion valves. The method includes controlling the total opening (total opening) of the first and second expansion valves based on the temperature and pressure of the refrigerant, which are measured downstream of the first and second evaporators at a location between the first and second evaporators and the compressor.

[0006] This invention is based on the insight that this method can separate the problems of ensuring the necessary superheat level of the refrigerant and achieving the desired cooling power distribution among the evaporators. A target superheat level is not required at each evaporator outlet, and temperature sensors are not needed to measure the refrigerant temperature at each evaporator outlet.

[0007] According to one embodiment, the method includes controlling the total opening of a first expansion valve and a second expansion valve based on an overheat control error, which is the difference between a superheat value, a function of refrigerant temperature and refrigerant pressure, and a target superheat value. This allows a target superheat level to be achieved, thereby further reducing the risk of liquid refrigerant entering the compressor.

[0008] According to another embodiment, the method includes controlling the opening of the first expansion valve based on the temperature of the first-stage fluid measured when the first-stage fluid has passed through the first evaporator and the temperature of the second-stage fluid measured when the second-stage fluid has passed through the second evaporator. This minimizes the number of sensors used in the system.

[0009] Liquid coolants such as water can be used as one of the primary and secondary fluids. Air or other liquid coolants can be used as the other of the primary and secondary fluids. For example, heat from the battery and / or motor, and heat from the vehicle compartment, can be transferred to the first and second evaporators, respectively.

[0010] According to another embodiment, the method includes controlling the opening of the first expansion valve based on a first temperature control error (the difference between the temperature of the first-stage fluid and the target temperature) and a second temperature control error (the difference between the temperature of the second-stage fluid and the target temperature), and preferably based on the difference between the first and second temperature control errors. This ensures that the portion of the total cooling power of the refrigeration system allocated to the first evaporator is adapted to the relationship between the cooling requirements of the first-stage fluid and the cooling requirements of the second-stage fluid.

[0011] According to another embodiment, the method includes controlling the opening of the second expansion valve to be the remainder after subtracting the portion allocated to the opening of the first expansion valve from the total opening of the first and second expansion valves. This ensures that the control unit distributing the total cooling power of the refrigeration system between the first and second evaporators does not affect the total opening area of ​​the first and second expansion valves.

[0012] The present invention also relates to a control unit for controlling a vehicle's refrigeration system. The advantages of this control unit are similar to those of different embodiments of the reference methods already discussed above.

[0013] Further advantages and advantageous features of the invention are disclosed in the following description and claims. Attached Figure Description

[0014] Referring to the accompanying drawings, embodiments of the present invention, which are cited as examples, will now be described in more detail.

[0015] In the attached diagram:

[0016] Figure 1 A refrigeration system for a vehicle is shown, and

[0017] Figure 2 This is a control diagram of a control unit used to control the refrigeration system. Detailed Implementation

[0018] Figure 1 This is a schematic diagram of a refrigeration system 1 for a vehicle. The refrigeration system 1 includes a circuit 2 containing refrigerant, a compressor 3, and a first evaporator 4 and a second evaporator 5 connected in parallel to the compressor 3. The circuit 2 has a main circuit 6, a first sub-circuit 7 for the first evaporator 4, and a second sub-circuit 8 for the second evaporator 5. The compressor 3 is arranged in the main circuit 6 and is used to compress the refrigerant or working fluid circulating in the circuit 2 of the refrigeration system 1. The compressor 3 may be driven by an electric motor (not shown).

[0019] The refrigeration system 1 also includes a first expansion valve 9 disposed upstream of the first evaporator 4 in the first sub-circuit 7 and a second expansion valve 10 disposed upstream of the second evaporator 5 in the second sub-circuit 8. The first expansion valve 9 is arranged to regulate the pressure drop of the refrigerant before the first evaporator 4, and the second expansion valve 10 is arranged to regulate the pressure drop of the refrigerant before the second evaporator 5. In addition to reducing the refrigerant pressure, the first expansion valve 9 and the second expansion valve 10 are used to control the distribution (allocation) of the refrigerant flow between the first evaporator 4 and the second evaporator 5. In other words, the refrigerant flow in the main circuit 6 is divided into a first flow through the first sub-circuit 7 and a second flow through the second sub-circuit 8.

[0020] Furthermore, the condenser 11 is suitably arranged downstream of the compressor 3 in the main circuit 6, between the compressor 3 and the first expansion valve 9 and the second expansion valve 10. During operation, heat can be transferred from the surroundings to the refrigerant at the first evaporator 4 and the second evaporator 5, and heat can be transferred from the refrigerant to the surroundings at the condenser 11.

[0021] The working principle of refrigeration system 1 is as follows: The compressor 3 pressurizes the gaseous refrigerant and circulates it through the system. The operation of the compressor 3 controls the refrigerant flow in the main circuit 6. After passing through the compressor 3, the hot and high-pressure refrigerant is cooled in the condenser 11 until it condenses into a high-pressure liquid with a lower temperature.

[0022] The first portion of the condensed refrigerant passes through the first expansion valve 9, and the remaining portion passes through the second expansion valve 10. Then, the low-pressure refrigerant in the first sub-loop 7 enters the first evaporator 4, where it absorbs heat and evaporates. Similarly, the low-pressure refrigerant in the second sub-loop 8 enters the second evaporator 5, where it absorbs heat and evaporates. Afterward, a portion of the refrigerant flows back to the main loop 6 and the compressor 3, and this cycle repeats. The direction of refrigerant circulation in loop 2 (referring to "upstream" and "downstream") is indicated by arrow 12.

[0023] like Figure 1As schematically shown, the first evaporator 4 and the second evaporator 5 operate as heat exchangers. When passing through the first evaporator 4, heat is transferred from the first stage fluid 13 to the refrigerant, and when passing through the second evaporator 5, heat is transferred from the second stage fluid 14 to the refrigerant.

[0024] When the refrigeration system 1 is applied to a vehicle, a liquid coolant such as water can be used as one of the primary and secondary fluids. For example, the primary fluid 13 can be water. Air or another liquid coolant can be used as the other of the primary and secondary fluids. For example, the secondary fluid 14 can be air.

[0025] Furthermore, heat from the motor, battery, or any other component and / or from the vehicle compartment requiring cooling can be transferred to the first evaporator 4 and the second evaporator 5 via the primary fluid 13 and the secondary fluid 14. Additionally, the condenser 11 can transfer heat to the surrounding air and / or the vehicle compartment and / or any other components of the vehicle requiring heating. Heat from the condenser 11 can be transferred from the refrigerant to the air or another working fluid.

[0026] Figure 1 A control unit 15 for controlling the refrigeration system 1 is shown. The control unit 15 is configured to operate based on the temperature T of the refrigerant. m and pressure p m The refrigerant temperature and pressure are measured in the main circuit 6, between the first evaporator 4 and the second evaporator 5 and the compressor 3, to control the overall opening of the first expansion valve 9 and the second expansion valve 10. The refrigerant temperature T... m and refrigerant pressure p m Measurements can be taken at any point between point 16, where the first sub-loop 7 and the second sub-loop 8 merge into the main loop 6, and the compressor inlet 17, but the refrigerant temperature T... m and refrigerant pressure p m Suitable for measurement at 17 near the compressor inlet.

[0027] To measure the refrigerant temperature T m and refrigerant pressure p m Temperature sensor 18 and pressure sensor 19 can be used respectively. Signals 20 and 21 from temperature sensor 18 and pressure sensor 19 are transmitted to control unit 15.

[0028] In the exemplary embodiment shown, the control unit 15 is configured to control the total opening degree of the first expansion valve 9 and the second expansion valve 10 based on an overheat control error ΔSH, where the overheat control error ΔSH is the refrigerant temperature T. m and refrigerant pressure pm The superheat value SH and the target superheat value SH of the function target The difference between them. For example Figure 1 As shown, control signals 22 and 23 are transmitted from the control unit 15 to control the opening degree of the first expansion valve 9 and the second expansion valve 10.

[0029] The total opening degree of the first expansion valve 9 and the second expansion valve 10 is the sum of the opening degrees of the first expansion valve 9 and the second expansion valve 10. The opening degree of each expansion valve 9 and 10 can be controlled based on the desired cooling power distribution between the first evaporator 4 and the second evaporator 5.

[0030] In the exemplary embodiment shown, the control unit 15 is configured to control the opening degree of the first expansion valve 9 based on the temperature T1 of the first-stage fluid 13 measured when the first-stage fluid 13 has passed through the first evaporator 4 and the temperature T2 of the second-stage fluid 14 measured when the second-stage fluid 14 has passed through the second evaporator 5.

[0031] The primary fluid temperature T1 and the secondary fluid temperature T2 can be measured by temperature sensors 24 and 25, preferably at the outlets of the first and second evaporators. Signals 26 and 27 from temperature sensors 24 and 25 are transmitted to control unit 15.

[0032] The control unit 15 is appropriately configured to control the opening degree of the first expansion valve 9 based on a first temperature control error ΔT1 and a second temperature control error ΔT2, wherein the first temperature control error ΔT1 is the difference between the temperature T1 of the primary fluid and the target temperature T2. target The difference, the second temperature control error ΔT2 is the difference between the temperature T2 of the second stage fluid and the target temperature T2. target The difference between the first temperature control error ΔT1 and the second temperature control error ΔT2 is preferred, and the control unit 15 is configured to control the opening degree of the first expansion valve 9 based on the difference between the first temperature control error ΔT1 and the second temperature control error ΔT2.

[0033] Furthermore, the control unit 15 can be configured to control the opening degree of the second expansion valve 10 to the remainder after subtracting the portion allocated to the opening degree of the first expansion valve 9 from the total opening degree of the first expansion valve 9 and the second expansion valve 10.

[0034] The control unit 15 may include one or more microprocessors and / or one or more storage devices or any other components for executing computer programs or receiving and / or transmitting control signals for providing control functions. In particular, the control unit preferably includes a computer program comprising program code means for performing all steps of any embodiment of the methods described herein. The control unit may be a separate component or integrated into another controller. The control unit may be arranged to control other components of the refrigeration system. For example, the control unit may be suitably arranged to control the compressor.

[0035] The control unit 15 may include one or more controllers of type P, type PI, type PID, or combinations thereof. For example, the control unit 15 may include a first PID controller 28 for controlling the total opening of the first expansion valve and the second expansion valve based on the overheat control error ΔSH, and a second PID controller 29 for controlling the opening of the first expansion valve based on the difference between the first temperature control error ΔT1 and the second temperature control error ΔT2.

[0036] Figure 2 A control schematic diagram of the control unit 15 used to control the refrigeration system 1 is shown. (Reference) Figure 2 Control diagram 30 and Figure 1 A refrigeration system 1 is used to illustrate an exemplary embodiment of the method. The method includes, based on the temperature T of the refrigerant... m and pressure p m The total opening degree of the first expansion valve and the second expansion valve is controlled. The refrigerant temperature and refrigerant pressure are measured at a position between the first evaporator and the second evaporator and the compressor, downstream of the first evaporator and the second evaporator.

[0037] The method also includes controlling the total opening of the first and second expansion valves based on an overheat control error ΔSH, where the overheat control error ΔSH is the refrigerant temperature T. m and refrigerant pressure p m The superheat value SH and the target superheat value SH of the function target The difference between them.

[0038] The first PID controller 28 of the control unit 15 is used to control the total opening degree of the first expansion valve and the second expansion valve.

[0039] In the exemplary embodiment shown, the method further includes controlling the opening of the first expansion valve based on the temperature T1 of the first-stage fluid measured when the first-stage fluid has passed through the first evaporator and the temperature T2 of the second-stage fluid measured when the second-stage fluid has passed through the second evaporator.

[0040] The method includes controlling the opening degree of the first expansion valve based on a first temperature control error ΔT1 and a second temperature control error ΔT2, wherein the first temperature control error ΔT1 is the temperature T1 of the first stage fluid and the target temperature T2. target The difference, the second temperature control error ΔT2 is the temperature of the second stage fluid T2 and the target temperature T2. target The method further includes controlling the opening degree of the first expansion valve based on the difference between the first temperature control error ΔT1 and the second temperature control error ΔT2. The second PID controller 29 of the control unit 15 is used to control the opening degree of the first expansion valve.

[0041] The first temperature error ΔT1 and the second temperature error ΔT2 can be corrected by scaling factors (factors) K1 and K2 to achieve the desired system behavior.

[0042] The method further includes controlling the opening of the second expansion valve to be the remainder after subtracting the portion allocated to the opening of the first expansion valve from the total opening of the first and second expansion valves. It should be understood that the present invention is not limited to the embodiments described above and shown in the accompanying drawings; rather, those skilled in the art will recognize that many changes and modifications can be made within the scope of the appended claims.

Claims

1. A method for controlling a vehicle's refrigeration system (1), the refrigeration system comprising: The circuit for containing the refrigerant (2); Compressor (3); The first evaporator (4) and the second evaporator (5) are connected in parallel to the compressor; A first expansion valve (9) is arranged upstream of the first evaporator, and the first expansion valve regulates the pressure drop of the refrigerant before the first evaporator; A second expansion valve (10) is arranged upstream of the second evaporator, and the second expansion valve regulates the pressure drop of the refrigerant before the second evaporator; as well as A condenser (11) is arranged between the compressor and the first expansion valve and the second expansion valve and downstream of the compressor (3); The circuit (2) has a main circuit (6), a first sub-circuit (7) for the first evaporator (4) and a second sub-circuit (8) for the second evaporator (5). Its characteristic is that, based on the temperature T of the refrigerant m and pressure p m The total opening of the first expansion valve (9) and the second expansion valve (10) is controlled. The refrigerant temperature and refrigerant pressure are measured in the main circuit (6) at a location between the first evaporator and the second evaporator and the compressor, downstream of the first evaporator and the second evaporator. The measurement location is between the point (16) where the first sub-circuit (7) and the second sub-circuit (8) merge into the main circuit (6) and the inlet (17) of the compressor. The opening degree of the first expansion valve (9) is controlled based on the temperature T1 of the first-stage fluid (13) measured when the first-stage fluid (13) has passed through the first evaporator (4) and the temperature T2 of the second-stage fluid (14) measured when the second-stage fluid (14) has passed through the second evaporator (5); and The opening degree of the second expansion valve (10) is controlled to be the remainder after subtracting the portion allocated to the opening degree of the first expansion valve (9) from the total opening degree of the first expansion valve (9) and the second expansion valve (10).

2. The method according to claim 1, characterized in that, The total opening degree of the first expansion valve (9) and the second expansion valve (10) is controlled based on the overheat control error ΔSH, wherein the overheat control error ΔSH is taken as the refrigerant temperature T. m and refrigerant pressure p m The superheat value SH and the target superheat value SH of the function target The difference between them.

3. The method according to claim 1, characterized in that, The opening degree of the first expansion valve (9) is controlled based on the first temperature control error ΔT1 and the second temperature control error ΔT2, wherein the first temperature control error ΔT1 is the temperature T1 of the first stage fluid and the target temperature T2. target The difference, the second temperature control error ΔT2 is the temperature T2 of the second stage fluid and the target temperature T2. target difference.

4. The method according to claim 3, characterized in that, The opening degree of the first expansion valve (9) is controlled based on the difference between the first temperature control error ΔT1 and the second temperature control error ΔT2.

5. The method according to claim 1, characterized in that, A liquid coolant is used as one of the first-stage fluid (13) and the second-stage fluid (14).

6. The method according to claim 5, characterized in that, Use air or another liquid coolant as the other of the first-stage fluid (13) and the second-stage fluid (14).

7. A control unit (15) for controlling a vehicle's refrigeration system (1), the refrigeration system comprising: The circuit for containing the refrigerant (2); Compressor (3); The first evaporator (4) and the second evaporator (5) are connected in parallel to the compressor (3); A first expansion valve (9) is arranged upstream of the first evaporator, and the first expansion valve regulates the pressure drop of the refrigerant before the first evaporator; A second expansion valve (10) is arranged upstream of the second evaporator, and the second expansion valve regulates the pressure drop of the refrigerant before the second evaporator; as well as A condenser (11) is arranged between the compressor and the first expansion valve and the second expansion valve, and downstream of the compressor (3). The circuit (2) has a main circuit (6), a first sub-circuit (7) for the first evaporator (4) and a second sub-circuit (8) for the second evaporator (5). The control unit (15) is characterized in that it is configured to be able to base its operation on the temperature T of the refrigerant. m and pressure p m The total opening of the first expansion valve (9) and the second expansion valve (10) is controlled. The refrigerant temperature and refrigerant pressure are measured in the main circuit (6) at a location between the first evaporator and the second evaporator and the compressor, downstream of the first evaporator and the second evaporator. The measurement location is between the point (16) where the first sub-circuit (7) and the second sub-circuit (8) merge into the main circuit (6) and the inlet (17) of the compressor. The control unit (15) is configured to control the opening of the first expansion valve (9) based on the temperature T1 of the first-stage fluid (13) measured when the first-stage fluid (13) has passed through the first evaporator (4) and the temperature T2 of the second-stage fluid (14) measured when the second-stage fluid (14) has passed through the second evaporator (5); and The control unit (15) is configured to control the opening of the second expansion valve (10) to be the remainder after subtracting the portion allocated to the opening of the first expansion valve (9) from the total opening of the first expansion valve (9) and the second expansion valve (10).

8. The control unit according to claim 7, characterized in that, The control unit (15) is configured to control the total opening of the first expansion valve (9) and the second expansion valve (10) based on an overheat control error ΔSH, wherein the overheat control error ΔSH is the refrigerant temperature T. m and refrigerant pressure p m The superheat value SH and the target superheat value SH of the function target difference.

9. The control unit according to claim 7, characterized in that, The control unit (15) is configured to control the opening degree of the first expansion valve (9) based on a first temperature control error ΔT1 and a second temperature control error ΔT2, wherein the first temperature control error ΔT1 is the temperature T1 of the first stage fluid (13) and the target temperature T1. target The difference, the second temperature control error ΔT2 is the temperature T2 of the second stage fluid (14) and the target temperature T2. target difference.

10. The control unit according to claim 9, characterized in that, The control unit (15) is configured to control the opening degree of the first expansion valve (9) based on the difference between the first temperature control error ΔT1 and the second temperature control error ΔT2.

11. A computer program comprising program code means for performing the method according to any one of claims 1-6.

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