Refrigerant system and method of flushing oil from auxiliary evaporator of refrigerant system

Abstract

The present disclosure provides a refrigerant system and a method of flushing oil from an auxiliary evaporator of the refrigerant system. A method of flushing oil from an evaporator of a refrigerant system. The refrigerant system includes a primary (first) evaporator and at least one secondary (second) evaporator. Both evaporators receive refrigerant from the compressor. The method includes adjusting an expansion valve to increase refrigerant flow through the auxiliary evaporator if oil or other liquid may be trapped in the auxiliary evaporator, thereby flushing oil from the auxiliary evaporator.

Description

Technical Field

[0001] This disclosure generally relates to a refrigerant system, and more specifically, to a refrigerant system for controlling the refrigerant flow through at least two evaporators or coolers, thereby flushing out oil that may have accumulated in the evaporator by increasing the refrigerant flow through a selected evaporator. Background Technology

[0002] A heating, ventilation, and air conditioning (“HVAC”) system may include a refrigerant system. The refrigerant system may include a compressor that compresses refrigerant in gaseous form and circulates the refrigerant through a condenser and two or more evaporators. The condenser cools and condenses the refrigerant, thereby forming a liquid, which evaporates in the evaporators. An expansion valve upstream of the evaporators may be controlled during operation of the refrigerant system. After leaving the evaporators, the refrigerant flows back to the compressor. Oil may be used to lubricate the compressor. During operation of the refrigerant system, oil may flow into one or more evaporators. Summary of the Invention

[0003] A refrigerant system for a vehicle according to one aspect of this disclosure includes a compressor and a condenser, the condenser receiving refrigerant from the compressor. The refrigerant system also includes a first expansion valve and a second expansion valve, both receiving refrigerant from the condenser. A first evaporator receives refrigerant from the first expansion valve and returns refrigerant to the compressor. A second evaporator receives refrigerant from the second expansion valve and returns refrigerant to the compressor. The refrigerant system further includes a controller configured to: 1) utilize a master control mode to control the position of the first expansion valve as needed through a range of operating positions to meet heat demands during operation of the refrigerant system; and 2) utilize a flushing mode to adjust the position of the first expansion valve to reduce the refrigerant flow through the first evaporator and increase the refrigerant flow through the second evaporator to a position sufficient to flush oil from the second evaporator.

[0004] Embodiments of the first aspect of this disclosure may include any one or a combination of the following features: - The controller is optionally configured to revert from the flushing mode to the main control mode if the cooling performance of the first evaporator has decreased according to a predefined criterion during the flushing mode.

[0005] - The predefined criteria optionally include the temperature of the refrigerant.

[0006] - The predefined criterion optionally includes the temperature of the refrigerant leaving the first evaporator, which is higher than the predefined temperature.

[0007] - The controller is optionally configured to return from the flushing mode to the main control mode after a predefined time period starting from the flushing mode.

[0008] - The controller is optionally configured to return from the flushing mode to the main control mode even if the cooling performance of the first evaporator has not decreased according to the predefined criteria during the flushing mode.

[0009] - The predefined criteria optionally include a time period since the end of the previous flushing mode.

[0010] - The controller is optionally configured to alternate between the main control mode and the flushing mode at predefined time intervals.

[0011] - The first evaporator optionally includes a main evaporator configured to cool air or coolant supplied to the passenger compartment or battery of a motor vehicle.

[0012] The refrigerant system may include a first fluid line and a second fluid line, which fluidly connect the first expansion valve and the second expansion valve to the outlet of the condenser, respectively, thereby adjusting the position of the first expansion valve to reduce the refrigerant flow through the first fluid line and increase the refrigerant flow through the second refrigerant line.

[0013] - The controller is optionally configured to revert from the flushing mode to the main control mode if a predefined oil flushing criterion is met.

[0014] The predefined oil flushing standard can be determined at least in part by testing the refrigerant system to determine a combination of operating parameters that indicate a satisfactory oil flush from the second evaporator.

[0015] Another aspect of this disclosure is a method for flushing oil from an auxiliary evaporator of a refrigerant system having a main evaporator and an auxiliary evaporator, both receiving refrigerant from a compressor. The method includes adjusting an expansion valve to increase the refrigerant flow through the auxiliary evaporator if oil may be trapped therein, thereby flushing the oil from the auxiliary evaporator.

[0016] Embodiments of the second aspect of this disclosure may include any one or a combination of the following features: - After adjusting the expansion valve to increase the refrigerant flow through the auxiliary evaporator, the expansion valve can be adjusted to reduce the refrigerant flow through the auxiliary evaporator if a predefined criterion is met.

[0017] - The predefined criteria may optionally include the temperature of the refrigerant leaving the main evaporator, which is greater than a threshold temperature.

[0018] - The predefined criterion optionally includes the time period since the expansion valve has been adjusted to increase the refrigerant flow through the auxiliary evaporator.

[0019] The refrigerant system optionally includes a first expansion valve and a second expansion valve, the first expansion valve and the second expansion valve respectively controlling the refrigerant flow from the compressor to the main evaporator and the auxiliary evaporator. The first expansion valve is optionally adjusted to increase the refrigerant flow through the auxiliary evaporator by reducing the refrigerant flow through the main evaporator.

[0020] Another aspect of this disclosure is a motor vehicle including a refrigerant system configured to heat and / or cool the vehicle's passenger compartment or battery. The refrigerant system includes a compressor and a condenser, the condenser receiving refrigerant from the compressor. The refrigerant system also includes a first expansion valve and a second expansion valve, both receiving refrigerant from the condenser. A first evaporator receives refrigerant from the first expansion valve and returns the refrigerant to the compressor. A second evaporator receives refrigerant from the second expansion valve and returns the refrigerant to the compressor. The refrigerant system also includes a controller configured to: 1) utilize a master control mode to control the position of the first expansion valve through a range of operating positions as needed to meet heat demands during normal operation of the refrigerant system; and 2) utilize a flushing mode to adjust the position of the first expansion valve to a position outside the lower limit of the range of operating positions if oil accumulation may occur in the second evaporator according to a predefined criterion, thereby reducing the refrigerant flow through the first evaporator and increasing the refrigerant flow through the second evaporator to flush out the oil in the second evaporator.

[0021] Embodiments of the third aspect of this disclosure may include any one or a combination of the following features: - The first evaporator is optionally configured to cool air or coolant supplied to the vehicle compartment or battery of the motor vehicle.

[0022] - The controller is optionally configured to revert from the flushing mode to the main control mode if the cooling performance of the first evaporator has been sufficiently reduced according to a predefined criterion.

[0023] By referring to the following description, claims and drawings, those skilled in the art will further understand and appreciate these and other features, advantages and objectives of the present invention. Attached Figure Description

[0024] In the attached diagram: Figure 1 This is a partial schematic plan view of a motor vehicle according to one aspect of this disclosure; Figure 2 It is a diagram of a refrigerant system according to one aspect of this disclosure; and Figure 3 This is a flowchart illustrating a method for flushing oil from an evaporator according to one aspect of this disclosure. Detailed Implementation

[0025] Reference will now be made in detail to the preferred embodiments of this disclosure, examples of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. In the drawings, structural elements are depicted not to scale, and some parts are enlarged relative to others for emphasis and understanding purposes.

[0026] Detailed embodiments of the present disclosure are disclosed herein as requested; however, it should be understood that the disclosed embodiments are merely examples of different and alternative forms in which the invention may be embodied. The accompanying drawings are not necessarily detailed designs; some schematic diagrams may be enlarged or minimized to show a functional overview. Therefore, the specific structural and functional details disclosed herein are not to be construed as limiting, but are merely intended to teach those skilled in the art to employ the representative basis of the invention in various ways.

[0027] For the purposes of this description, the terms “up,” “down,” “right,” “left,” “back,” “front,” “vertical,” “horizontal,” and their derivatives should refer to, for example, the following: Figure 1 The concept of orientation is used. However, it should be understood that the concept may present various alternative orientations unless explicitly specified otherwise. It should also be understood that the specific apparatus and processes shown in the accompanying drawings and described in the following specification are merely exemplary embodiments of the inventive concept defined in the appended claims. Therefore, unless otherwise expressly stated in the claims, the specific dimensions and other physical characteristics relating to the embodiments disclosed herein should not be considered limiting.

[0028] The embodiments shown here exist primarily in combinations of method steps and equipment components related to refrigerant systems. Therefore, equipment components and method steps have been indicated by conventional symbols in the accompanying drawings where appropriate, showing only those specific details relevant to understanding embodiments of this disclosure, so as not to obscure the disclosure with details readily apparent to those skilled in the art who benefit from the description herein. Furthermore, the same reference numerals denote the same elements in the specification and drawings.

[0029] As used herein, the terms “or” and “and / or” when used with two or more listed items mean that any one of the listed items may be used alone, or any combination of two or more listed items may be used. For example, if a composition or device is described as containing or including components A, B, and / or C, the composition or device may contain (including): A only; B only; C only; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C. If a composition or device is described as containing or including components A and / or B and / or C, the composition or device may contain (including): A only; B only; C only; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0030] In this document, relational terms such as first and second, top and bottom are used individually to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprising,” “including,” or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article of manufacture, or apparatus that comprises a list of elements includes not only those elements but may also include other elements not expressly listed or inherent to such process, method, article of manufacture, or apparatus. Without further constraints, an element preceded by “comprising…” does not exclude the presence of additional identical elements in the process, method, article of manufacture, or apparatus that includes said element.

[0031] As used herein, the term "about" means that a quantity, size, formulation, parameter, and other quantity and characteristic is not precise, nor need it to be precise, but may be approximate and / or larger or smaller as required to reflect tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. When the term "about" is used to describe an endpoint of a value or range, this disclosure should be understood to include both the specific value and the mentioned endpoint. Whether or not the endpoints of numerical values ​​or ranges in this specification are referred to as "about," the endpoints are intended to include both embodiments: one modified by "about" and one not modified by "about." It should also be understood that each endpoint of a range is significant both in relation to and independent of another endpoint.

[0032] As used herein, the terms “substantially,” “basically,” and variations thereof are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a “substantially planar” surface is intended to indicate a planar or approximately planar surface. Additionally, “substantially” is intended to mean that two values ​​are equal or approximately equal. In some embodiments, “substantially” may indicate that the values ​​are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0033] Unless explicitly indicated otherwise, as used herein, the terms “the,” “an,” or “a” mean “at least one” and should not be limited to “only one.” Thus, for example, unless the context clearly indicates otherwise, references to “component” include embodiments having two or more such components.

[0034] refer to Figure 1 According to one aspect of this disclosure, a motor vehicle may include a body 2 and a passenger space or compartment 8. The vehicle 1 includes a power drive system 4 operatively coupled to one or more wheels 5 to move the vehicle 1. The power drive system 4 may include an electric drive, a combustion engine, or a combination thereof. The vehicle 1 may include a voltage source 20. If the power drive system 4 includes an electric motor, the voltage source 20 may include a high-voltage (HV) battery. The vehicle 1 also includes a controller 6 operatively interconnected with the power drive system 4 and a refrigerant system 10. The controller 6 may include a plurality of individual controllers operatively interconnected via one or more networks and may optionally include a control module specifically configured to control the refrigerant system 10. However, it should be understood that this disclosure is not limited to any particular control arrangement. The refrigerant system 10 may include a fan 9 (“HVAC blower”) that circulates air through or through one or more heat exchangers, such as a first (main) evaporator 22A, to supply conditioned air 11A to the front portion 8A of the compartment 8. As discussed below, system 10 may include a rear HVAC system 7 having a second evaporator 22B, which may be located in the rear portion of vehicle 1 to supply conditioned air 11B to the rear portion 8B of passenger compartment 8. The second evaporator 22B may be fluidly connected to compressor 12 and condenser 14 via refrigerant line A.

[0035] Further reference Figure 2The refrigerant system 10 may include a compressor 12, a condenser 14, a first expansion valve 16A and a second expansion valve 16B, a main evaporator 22A, and an auxiliary evaporator 22B. Compressed and heated refrigerant (gas) from the compressor 12 flows from the compressor 12 outlet 13B through refrigerant line A1 to the condenser 14 inlet 15A. As the refrigerant flows through the condenser 14, it is cooled to form vapor and / or liquid. After flowing through the condenser 14, the refrigerant flows from the condenser 14 outlet 15B through refrigerant lines A2 and A3 to the expansion valves 16A and 16B inlets 17A and 17B. Refrigerant from the expansion valve 16A flows from the expansion valve 16A outlet 18A through refrigerant line A4 to the evaporator 22A inlet 23A. After the refrigerant flows through the evaporator 22A, the refrigerant flows from the outlet 24A of the evaporator 22A through the refrigerant line A6, and then the refrigerant flows through the refrigerant line A8 to the inlet 13A of the compressor 12.

[0036] The refrigerant flows from the outlet 18B of the expansion valve 16B through the refrigerant line A5 to the inlet 23B of the evaporator 22B, and the refrigerant leaves the evaporator 22B at the outlet 24B and flows through the refrigerant lines A7 and A8 to the inlet 13A of the compressor 12.

[0037] Expansion valves 16A and 16B may include electrically controlled valves (“EXV”) operably connected to controller 6. Alternatively, at least one of the expansion valves (typically 16B and other expansion valves for auxiliary evaporators) may include a thermal expansion valve (“TXV”) that is not directly controlled by controller 6 but responds to a pressure input from the refrigerant after the refrigerant has expanded. Thus, if expansion valve 16B includes a thermal expansion valve (TXV), it responds to changing operating conditions rather than being directly controlled by controller 6.

[0038] The refrigerant system 10 may include valves 19A and / or 19B to control the flow of refrigerant to expansion valves 16A, 16B and evaporators 22A, 22B (and an additional evaporator). Valves 19A and 19B may be operatively connected to controller 6, and they may be used to control the flow of refrigerant. For example, if evaporator 22B is not in use (e.g., the rear portion 8B of the compartment 8 does not require cooling), valve 19B may be closed, thereby preventing refrigerant flow to evaporator 22B.

[0039] The refrigerant system 10 may include additional evaporators as required for a particular application. Examples of refrigerant systems that can be used in conjunction with oil flushing according to one aspect of this disclosure include U.S. Patent Application Publications Nos. 2022 / 0410664 A1 and 2022 / 0412611 A1, each of which is incorporated herein by reference. Typically, the refrigerant system 10 may include an air conditioning (AC) system, or it may include a heat pump system that can be used to heat and cool one or more components of the vehicle 1. For example, if the refrigerant system 10 includes a heat pump, it may be used to heat and cool the air supplied to the passenger compartment 8, and it may also be used to heat and cool the HV battery 20 using a liquid coolant. For example, the liquid coolant or air may be heated by the condenser 14 to heat the passenger compartment 8, the battery 20, or other components, and the air or liquid coolant may be cooled by one or more evaporators 22A, 22B, etc., thereby cooling the air supplied to the passenger compartment 8, or cooling the liquid coolant to cool the HV battery 20. It should be understood that, as used herein, “evaporator” can generally refer to a refrigerant-to-air and refrigerant-to-coolant (liquid) heat exchanger (“cooler”) or other evaporation device, in which the liquid refrigerant undergoes a phase change from liquid to vapor.

[0040] Oil or other lubricants may be used to lubricate compressor 12. During operation, the oil may circulate through system 10 along with the refrigerant. As used herein, the term "oil" generally refers to any liquid (e.g., lubricant) that may accumulate in the evaporator. Typically, expansion valves 16A and 16B control the refrigerant flow through evaporators 22A and 22B as needed to meet the heat requirements of normal operation. Therefore, expansion valves 16A and 16B typically move through a range of positions, including minimum and maximum open positions corresponding to the minimum and maximum refrigerant mass flow rates required to meet the heat requirements of evaporators 22A and 22B. If evaporator 22A includes a main evaporator, it may experience a greater refrigerant mass flow rate than the auxiliary evaporator 22B during normal operation. For example, during normal operation, expansion valve 16A may provide an increased refrigerant mass flow rate to evaporator 22A compared to the refrigerant mass flow rate flowing to evaporator 22B through expansion valve 16B. Because the refrigerant mass flow rate through evaporator 22A increases during normal operation, oil entrained in the refrigerant will tend to flow out of evaporator 22A rather than accumulate in it. However, if evaporator 22B experiences a lower refrigerant mass flow rate during normal operation (e.g., expansion valve 16B restricts refrigerant flow), oil may accumulate in evaporator 22B. It should be understood that system 10 may include an additional evaporator (e.g., an auxiliary evaporator) that can also operate in cases of insufficient refrigerant mass flow rate to flush (remove) oil during normal operation. As noted above, the term "oil," as used herein, can refer to virtually any liquid that can be entrained in the refrigerant flowing through the evaporator, thereby accumulating in one or more evaporators during normal operation of system 10.

[0041] Further reference Figure 3 The process or method 30 can be used to at least partially flush away oil that has accumulated in one or more evaporators of system 10. Method 30 can be implemented by a programmable controller (e.g., controller 6) configured to perform the steps of method 30. Method 30 may include a flushing mode or cycle that begins at start 32 and ends at step 42 when the main operation or normal (non-flushing) operation of system 10 is resumed. After start 32, at step 34, method 30 includes identifying one or more evaporators (such as auxiliary or second evaporator 22B)... Figure 2Whether an oil trapping condition may occur. Various predefined criteria can be used to determine the presence of an oil trapping condition (“entry condition”). Typically, evaporator 22B will only trap oil if it is in operation. Therefore, if no refrigerant flows to evaporator 22B (e.g., valve 19B is closed), method 30 will proceed to normal control (step 42). Examples of operating parameters that may indicate the possibility of an oil trapping condition may include one or more of the following: 1) compressor speed below a predefined threshold; 2) HVAC blower 9 ( Figure 1 (3) The compressor speed is below a predefined threshold; and (4) The ambient temperature is below a predefined threshold. When the compressor speed, ambient temperature, and HVAC blower are all high, there is usually a significant mass flow through the evaporator 22B and the oil flows back well to the compressor 12.

[0042] The oil trapping criteria used at step 34 may include, for example, the time period since the previous oil flushing cycle according to process 30 (e.g., the time that system 10 has been operating). It should be understood that controller 6 can be configured to implement method 30 simultaneously for multiple auxiliary evaporators, thus allowing method 30 to be implemented for multiple evaporators when each evaporator meets the criteria at step 34. Typically, each evaporator can be flushed individually in sequence when it meets the criteria of step 34. If an oil trapping condition is not possible at step 34, process 30 returns to step 42, and the control of expansion valves 16A and 16B follows the normal control scheme (i.e., a control scheme that meets the thermal demand of system 10 but is not specifically configured to flush oil from one or more evaporators).

[0043] However, if oil trapping may occur at step 34, process 30 then proceeds to step 36 and the expansion valve 16A ( Figure 2The position of the expansion valve 16A is adjusted (reduced) to a calibrated oil flush position. Typically, the calibrated oil flush position of the expansion valve 16A may include a more restricted valve position than is expected to occur during normal operation of the system 10. During normal operation, the expansion valve 16A can move through a range of operating positions, defined by a minimum and a maximum position, which can be expressed as a percentage (%) of the fully open position. Therefore, the upper and lower limits of the expansion valve position for normal use of the system 10 are typically not equal to mechanically fully closed (0%) or fully open (100%). The position of the expansion valve 16A when restricted may include a percentage (e.g., 10% or 20%) much lower than the minimum required to meet the system's thermal demand during normal operation (e.g., 30% or 40%). Typically, the main EXV (expansion valve 16A) can be restricted to extremely low levels that would not be used during normal operation because the refrigerant temperature becomes unstable when the expansion valve 16A is highly restricted. When the flow rate through expansion valve 16A is highly restricted, the oil return from evaporator 22A is also temporarily reduced. Therefore, method 30 temporarily “sacrifices” the performance of one evaporator (evaporator 22A) to perform maintenance procedures on a second evaporator 22B or other auxiliary evaporators. However, in some cases, the calibrated oil flushing position may alternatively include a valve position that provides a sufficient refrigerant mass flow rate through evaporator 22B to flush oil from evaporator 22B, said valve position being within the normal range of valve positions. Therefore, if the range of valve positions encountered during normal operation includes a valve position sufficient to flush oil from evaporator 22B, the calibrated oil flushing position of expansion valve 16A can be within that range.

[0044] After shifting expansion valve 16A to the calibrated oil flushing position, system 10 operates in flushing mode or condition, thereby limiting the refrigerant flow through evaporator 22A and increasing the refrigerant flow through evaporator 22B, thereby flushing oil from evaporator 22B. During the flushing operation, system 10 can be configured to monitor one or more parameters of system 10 to determine whether the thermal performance of main evaporator 22 has deteriorated to an unacceptable level. For example, if evaporator 22A is used to supply cool air to the passenger compartment of a vehicle, system 10 can be configured to return to normal control 42 if the temperature of the air supplied to the compartment rises above an acceptable level. Acceptable levels can be determined by testing to determine which levels are considered unacceptable by the user. Alternatively, step 38 may include determining whether the temperature of the refrigerant leaving outlet 24A of evaporator 22A is above a threshold temperature, whereby if the temperature of the refrigerant leaving evaporator 22A is above the threshold, control returns to normal control mode 42.

[0045] However, if the decrease in cooling performance at step 38 does not exceed a predefined threshold / standard, the process continues to step 40, and the system determines whether the oil flush timer has expired. The oil flush timer may include the time period since the expansion valve was shifted to the calibrated oil flush position at step 36. If the oil flush timer has not expired, the process returns to step 36, and system 10 continues to operate in oil flush mode. However, if the oil flush timer has expired at step 40, the process returns to normal expansion valve control 42.

[0046] Method 30 may include checking at step 34 whether an ingress condition for oil flushing is possible, and then starting a timer (e.g., 5 minutes) if an oil flushing cycle is required. As discussed above, the ingress condition defines when oil trapping is most severe (most likely to occur). The oil flushing routine (mode) will run for 5 minutes per hour or other time periods, wherein these time periods are adjustable. This avoids running the flushing routine unnecessarily. For example, if the post-HVAC system 7 has been shut down for an extended period, flushing the evaporator 22B is unnecessary. The system is also configured to reset or stop the timer if the ingress condition (step 34) is removed. For example, a low compressor speed could be an ingress condition for starting the timer because this reduces the mass flow rate. If compressor 12 increases its speed, this tends to have an oil flushing effect, thus eliminating the need to restrict the flow through expansion valve 16A, and therefore stopping the timer when the compressor speed is higher (i.e., above a predefined speed).

[0047] Typically, flushing cycle or method 30 may involve restricting the passage through expansion valve 16A without adjusting the position of expansion valve 16B. Figure 2 The refrigerant flow rate (or an additional expansion valve associated with an additional evaporator) is controlled by the controller 6. However, if the expansion valve is controlled by the controller 6, the position of the expansion valve 16B can also be adjusted to provide an increased refrigerant flow rate through the evaporator 22B while limiting the flow rate through the expansion valve 16A. If the system 10 includes additional auxiliary evaporators, the expansion valves of these additional auxiliary evaporators can optionally be adjusted to provide sufficient refrigerant mass flow rate through a particular evaporator as needed to flush oil from it.

[0048] It should be understood that changes and modifications may be made to the foregoing structure without departing from the concept of the invention, and it should also be understood that such concept is intended to be covered by the appended claims unless those claims expressly state otherwise in their language.

[0049] According to the present invention, a refrigerant system for a vehicle is provided, the refrigerant system comprising: a compressor; a condenser receiving refrigerant from the compressor; a first expansion valve and a second expansion valve receiving refrigerant from the condenser; a first evaporator receiving refrigerant from the first expansion valve and returning refrigerant to the compressor; a second evaporator receiving refrigerant from the second expansion valve and returning refrigerant to the compressor; and a controller configured to: 1) utilize a main control mode to control the position of the first expansion valve as needed through a range of operating positions to meet the heat demand during normal operation of the refrigerant system; and 2) utilize a flushing mode to adjust the position of the first expansion valve to reduce the refrigerant flow through the first evaporator and increase the refrigerant flow through the second evaporator to a position sufficient to flush oil from the second evaporator.

[0050] According to an embodiment: the controller is configured to revert from the flushing mode to the main control mode if the cooling performance of the first evaporator has decreased according to a predefined criterion during the flushing mode.

[0051] According to an example: the predefined standard includes the temperature of the refrigerant.

[0052] According to an embodiment: the predefined criterion includes the temperature of the refrigerant leaving the first evaporator, which is higher than a predefined temperature.

[0053] According to an embodiment: the controller is configured to return from the flushing mode to the main control mode after a predefined time period.

[0054] According to an embodiment: the controller is configured to recover from the flushing mode even if the cooling performance of the first evaporator has not decreased according to the predefined criteria during the flushing mode.

[0055] According to an example: the predefined criteria include the time period since the previous flushing mode.

[0056] According to an embodiment: the controller is configured to alternate between the main control mode and the flushing mode.

[0057] According to an embodiment: the first evaporator includes a main evaporator configured to cool air or coolant supplied to the passenger compartment or battery of a motor vehicle.

[0058] According to an embodiment: a first fluid line and a second fluid line fluidly connect the first expansion valve and the second expansion valve to the outlet of the condenser, respectively, thereby adjusting the position of the first expansion valve to reduce the refrigerant flow through the first fluid line and increase the refrigerant flow through the second refrigerant line.

[0059] According to an embodiment: the controller is configured to revert from the flushing mode to the main control mode if a predefined oil flushing criterion is met.

[0060] According to an embodiment: the predefined oil flushing standard is determined at least in part by testing the refrigerant system to determine a combination of operating parameters that indicate a satisfactory oil flush from the second evaporator.

[0061] According to the present invention, a method for flushing oil from an auxiliary evaporator of a refrigerant system having a main evaporator and an auxiliary evaporator receiving refrigerant from a compressor comprises: adjusting an expansion valve to increase the refrigerant flow through the auxiliary evaporator if oil may be trapped in the auxiliary evaporator, thereby flushing the oil from the auxiliary evaporator.

[0062] In one aspect of the invention, the method includes: after adjusting the expansion valve to increase the refrigerant flow through the auxiliary evaporator, adjusting the expansion valve to reduce the refrigerant flow through the auxiliary evaporator if a predefined criterion is met.

[0063] In one aspect of the invention: the predefined criterion includes the temperature of the refrigerant leaving the main evaporator, the temperature being greater than a threshold temperature.

[0064] In one aspect of the invention, the predefined criterion includes a time period since the expansion valve has been adjusted to increase the refrigerant flow through the auxiliary evaporator.

[0065] In one aspect of the invention: the refrigerant system includes a first expansion valve and a second expansion valve, the first expansion valve and the second expansion valve respectively controlling the refrigerant flow from the compressor to the main evaporator and the auxiliary evaporator, and wherein: the first expansion valve is adjusted to increase the refrigerant flow through the auxiliary evaporator by reducing the refrigerant flow through the main evaporator.

[0066] According to the present invention, a motor vehicle is provided, the motor vehicle including a refrigerant system configured to heat and / or cool the passenger compartment of the motor vehicle, the refrigerant system including: a compressor; a condenser receiving refrigerant from the compressor; a first expansion valve and a second expansion valve receiving refrigerant from the condenser; a first evaporator receiving refrigerant from the first expansion valve and returning refrigerant to the compressor; and a second evaporator receiving refrigerant from the second expansion valve and returning refrigerant to the compressor; and a controller configured to: 1) utilize a main control mode to control the position of the first expansion valve through a range of operating positions as needed to meet the heat demand during normal operation of the refrigerant system; and 2) utilize a flushing mode to adjust the position of the first expansion valve to a position outside the lower limit of the range of operating positions if oil accumulation may occur in the second evaporator according to a predefined criterion, thereby reducing the refrigerant flow through the first evaporator and increasing the refrigerant flow through the second evaporator to flush the oil in the second evaporator.

[0067] In one aspect of the invention: the first evaporator is configured to cool air or coolant supplied to the passenger compartment or battery of the motor vehicle.

[0068] In one aspect of the invention, the controller is configured to revert from the flushing mode to the main control mode if the cooling performance of the first evaporator has been sufficiently reduced according to a predefined criterion.

Claims

1. A refrigerant system for a vehicle, the refrigerant system comprising: compressor; A condenser that receives refrigerant from the compressor; A first expansion valve and a second expansion valve, wherein the first expansion valve and the second expansion valve receive refrigerant from the condenser; A first evaporator receives refrigerant from the first expansion valve and returns the refrigerant to the compressor; The second evaporator receives refrigerant from the second expansion valve and returns the refrigerant to the compressor; as well as The controller is configured to: 1) The position of the first expansion valve is controlled within a certain range of operating positions using the main control mode to meet the heat demand during normal operation of the refrigerant system. as well as 2) Use the flushing mode to adjust the position of the first expansion valve to reduce the refrigerant flow through the first evaporator and increase the refrigerant flow through the second evaporator so as to flush the oil from the second evaporator.

2. The refrigerant system as claimed in claim 1, wherein: The controller is configured to revert from the flushing mode to the main control mode if the cooling performance of the first evaporator has decreased according to a predefined criterion during the flushing mode.

3. The refrigerant system as described in claim 2, wherein: The predefined standard includes the temperature of the refrigerant.

4. The refrigerant system as claimed in claim 2 or claim 3, wherein: The predefined criterion includes the temperature of the refrigerant leaving the first evaporator, which is higher than a predefined temperature.

5. The refrigerant system as claimed in claim 2, wherein: The controller is configured to return from the flushing mode to the main control mode after a predefined time period.

6. The refrigerant system according to any one of claims 1 to 5, wherein: The controller is configured to recover from the flushing mode even if the cooling performance of the first evaporator has not decreased according to the predefined criteria during the flushing mode.

7. The refrigerant system according to any one of claims 1 to 6, wherein: The predefined criteria include the time period since the previous flushing mode.

8. The refrigerant system according to any one of claims 1 to 7, wherein: The controller is configured to alternate between the main control mode and the flushing mode.

9. The refrigerant system according to any one of claims 1 to 8, wherein: The first evaporator includes a main evaporator configured to cool air and / or coolant supplied to the passenger compartment and / or battery of a motor vehicle.

10. The refrigerant system according to any one of claims 1 to 9, wherein: A first fluid line and a second fluid line fluidly connect the first expansion valve and the second expansion valve to the outlet of the condenser, respectively, thereby adjusting the position of the first expansion valve to reduce the refrigerant flow through the first fluid line and increase the refrigerant flow through the second refrigerant line.

11. The refrigerant system according to any one of claims 1 to 10, wherein: The controller is configured to revert from the flushing mode to the main control mode if a predefined oil flushing criterion is met.

12. The refrigerant system of claim 11, wherein: The predefined oil flushing standard is determined, at least in part, by testing the refrigerant system to determine a combination of operating parameters that indicate a satisfactory oil flush from the second evaporator.

13. A method for flushing oil from an auxiliary evaporator of a refrigerant system, the refrigerant system having a main evaporator and an auxiliary evaporator that receive refrigerant from a compressor, the method comprising: If oil may be trapped in the auxiliary evaporator, the expansion valve is adjusted to increase the refrigerant flow through the auxiliary evaporator, thereby flushing the oil out of the auxiliary evaporator.

14. The method of claim 13, wherein the method comprises: After adjusting the expansion valve to increase the refrigerant flow through the auxiliary evaporator, if a predefined criterion is met, the expansion valve is then adjusted to reduce the refrigerant flow through the auxiliary evaporator.

15. The method of claim 14, wherein: The predefined criteria include: 1) the temperature of the refrigerant leaving the main evaporator, which is greater than a threshold temperature, or 2) the time period since the expansion valve has been adjusted to increase the refrigerant flow through the auxiliary evaporator.

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