Method and system for low charge detection

Abstract

The present disclosure provides a method and system for low charge detection. Methods and systems for accessing operation of a cooling system of an electric vehicle are described. In one example, a superheat temperature at an inlet of a compressor may be generated via only a temperature sensor and a pressure sensor. The superheat temperature may be compared to a threshold superheat temperature to determine if the amount of refrigerant in the cooling system is as expected.

Description

Technical Field

[0001] The present description relates to methods and systems for diagnosing the operation of a cooling system of a vehicle. The methods and systems may be particularly useful for vehicles that include refrigerant-based cooling. Background Art

[0002] The vehicle may include a cooling system. The cooling system may cool the passenger compartment and the battery that provides power to propel the vehicle. Specifically, the cooling system may include a refrigerant, and the refrigerant may be used to cool the battery and the passenger compartment. The refrigerant may be compressed and condensed into a liquid before it expands in a cooler or evaporator. The cooler may cool the liquid coolant, and the liquid coolant may circulate within the battery, thereby cooling the battery. The evaporator may cool the air that passes through the evaporator and returns to the passenger compartment. Thus, the cooling system may apply the refrigerant as a medium for cooling liquids and gases.

[0003] It is understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims attached to the detailed description. In addition, the claimed subject matter is not limited to implementations that address any disadvantages mentioned above or in any part of this disclosure. Summary of the invention

[0004] The present specification relates to diagnosing the operation of a cooling system of a vehicle. The cooling system may provide cooling to a traction battery and a vehicle passenger compartment or cabin. In one example, the cooling system may include a refrigerant to move heat from a first location to a second location. The cooling system may be such as Figure 1 Alternatively, the cooling system may be part of a hybrid vehicle or a fuel cell vehicle. The cooling system may be as shown. Figure 2 The cooling system may be configured as shown or in another arrangement. The cooling system may use a refrigerant as a cooling medium. The cooling system may be configured as Figure 3 Proceed as shown to diagnose the cooling system. Figure 4 A method for operating a cooling system is shown in FIG. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Advantages described herein will be more fully understood when examples, referred to herein as examples of the detailed description, are read alone or with reference to the accompanying drawings, in which:

[0006] Figure 1 is a schematic diagram of a non-restrictive electric vehicle;

[0007] Figure 2 A vehicle cooling system is shown that can cool the battery and passenger compartment of the vehicle;

[0008] Figure 3 Shown according to Figure 4 Methods and Figure 1 and Figure 2 An exemplary sequence of operations of the system; and

[0009] Figure 4 A flow chart illustrating an exemplary method for diagnosing operation of a cooling system of a vehicle is shown. DETAILED DESCRIPTION

[0010] A vehicle may include a cooling system based on a refrigerant (e.g., R410A) to cool the passenger area and components of the vehicle. The cooling system may be configured as a heat pump that may exchange the functionality of a heat exchanger in the heat pump during varying operating conditions. The cooling system of the vehicle may provide cooling to different areas of the vehicle and devices within the vehicle simultaneously. For example, the cooling system may cool the traction battery and the passenger compartment of the vehicle simultaneously. The cooling system may adjust the speed of the refrigerant compressor or pump and the position of one or more valves (e.g., an expansion valve) to provide different levels of cooling capacity to the devices and passenger area of ​​the vehicle. However, if refrigerant is lost from the cooling system, the lubrication of the compressor may be reduced and the compressor may deteriorate. One way to determine whether refrigerant has been lost from the cooling system is to monitor the pressure on the inlet side of the compressor and the outlet side of the compressor. However, measuring the refrigerant pressure at the inlet and outlet of the compressor may only respond to a large amount of refrigerant loss. Therefore, there may be less opportunity to implement corrective measures before more significant mitigation techniques may have to be applied to reduce the possibility of compressor degradation. Therefore, it may be desirable to provide a way to detect smaller refrigerant losses from the cooling system.

[0011] The inventors of this document have recognized the above-mentioned shortcomings and have developed a method for operating a cooling system of a vehicle, the method comprising: generating an estimate of the superheat temperature of the refrigerant based on the pressure at the inlet side of the compressor and the temperature at the inlet side of the compressor; and deactivating the compressor in response to the estimate of the superheat temperature of the refrigerant exceeding an overheat threshold temperature.

[0012] By estimating the superheat temperature at the compressor inlet and comparing the superheat temperature to a threshold superheat temperature, it can be determined whether the cooling system has lost a small or large amount of refrigerant, so that less significant mitigation actions can be taken before implementing larger mitigation actions. Less significant mitigation actions can allow cooling of the vehicle to be maintained for a period of time so that the vehicle user can plan to service the vehicle. In addition, mitigation actions can reduce the likelihood of compressor degradation.

[0013] The present description may provide several advantages. Specifically, the method may reduce the likelihood of compressor degradation. Furthermore, the method may also provide a higher confidence level for detecting refrigerant loss in a cooling system. Additionally, the method may be implemented during cold or warm ambient temperatures and is independent of whether the heat pump is operating in a cooling mode or a heating mode.

[0014] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when taken alone or in conjunction with the accompanying drawings.

[0015] refer to Figure 1 , a non-limiting exemplary vehicle propulsion system 100 for a vehicle 121 is shown. The front of the vehicle 121 is indicated at 110, and the rear of the vehicle 121 is indicated at 111. The vehicle propulsion system 100 includes at least two propulsion sources, including a front motor 125 and a rear motor 126. However, in other examples, the vehicle 121 may include only one motor. The motors 125 and 126 may consume or generate electricity depending on their operating mode. Figure 1 , the mechanical connections between the various components are shown as solid lines, while the electrical connections between the various components are shown as dashed lines.

[0016] The vehicle propulsion system 100 includes a front axle 133 and a rear axle 122. In some examples, the rear axle may include two half shafts, such as a first half shaft 122a and a second half shaft 122b. Similarly, the front axle 133 may include a first half shaft 133a and a second half shaft 133b. The vehicle propulsion system 100 also has front wheels 130 and rear wheels 131. In this example, the front wheels 130 may be selectively driven via the motor 125. The rear wheels 131 may be driven via the motor 126.

[0017] The rear axle 122 is coupled to the motor 126. The rear drive unit 136 can transfer power from the motor 126 to the axle 122, resulting in rotation of the drive wheels 131. The rear drive unit 136 may include a low gear set 175 and a high gear 177 coupled to the motor 126 via the output shaft 126a of the rear motor 126. The low gear 175 can be engaged via a fully closed low gear clutch 176. The high gear 178 can be engaged via a fully closed high gear clutch 178. The high gear clutch 178 and the low gear clutch 176 can be opened and closed via commands received by the rear drive unit 136 via the CAN 299. Alternatively, the high gear clutch 178 and the low gear clutch 176 can be opened and closed via a digital output or pulse width provided by the control system 14. The rear drive unit 136 may include a differential 128 so that torque can be provided to the axle 122a and the axle 122b. In some examples, an electronically controlled differential clutch (not shown) may be included in rear drive unit 136 .

[0018] The front axle 133 is coupled to the motor 125. The front drive unit 137 can transfer power from the motor 125 to the axle 133, thereby causing the drive wheel 130 to rotate. The front drive unit 137 may include a low gear group 170 and a high gear 173 coupled to the motor 125 via the output shaft 125a of the front motor 125. The low gear 170 can be engaged via a fully closed low gear clutch 171. The high gear 173 can be engaged via a fully closed high gear clutch 174. The high gear clutch 174 and the low gear clutch 171 can be opened and closed via commands received by the front drive unit 137 through the CAN 299. Alternatively, the high gear clutch 174 and the low gear clutch 171 can be opened and closed via a digital output or pulse width provided by the control system 14. The front drive unit 137 may include a differential 127 so that torque can be provided to the axle 133a and the axle 133b. In some examples, an electronically controlled differential clutch (not shown) may be included in front drive unit 137 .

[0019] The motors 125 and 126 may receive power from an onboard electrical energy storage device 132 (e.g., a traction battery or a battery that provides power for the vehicle's propulsion). In addition, the motors 125 and 126 may provide a generator function to convert the vehicle's kinetic energy into electrical energy, where the electrical energy may be stored at the electrical energy storage device 132 for later use by the motors 125 and / or 126. The first inverter system controller (ISC1) 134 may convert alternating current (AC) generated by the rear motor 126 into direct current (DC) for storage at the electrical energy storage device 132, and vice versa. The second inverter system controller (ISC2) 147 may convert alternating current (AC) generated by the front motor 125 into direct current for storage at the electrical energy storage device 132, and vice versa. The electrical energy storage device 132 may be a battery, a capacitor, an inductor, or other electrical energy storage device.

[0020] In some examples, electrical energy storage device 132 can be configured to store electrical energy that can be supplied to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning systems, engine starting systems, headlight systems, cabin audio and video systems, and the like.

[0021] The control system 14 may communicate with one or more of the motor 125, the motor 126, the energy storage device 132, etc. The control system 14 may receive sensory feedback information from one or more of the motor 125, the motor 126, the energy storage device 132, etc. In addition, the control system 14 may send control signals to one or more of the motor 125, the motor 126, the energy storage device 132, etc. in response to such sensory feedback. The control system 14 may receive an indication of an operator-requested output of the vehicle propulsion system from the human operator 102 or the autonomous controller. For example, the control system 14 may receive sensory feedback from a pedal position sensor 194 in communication with a pedal 192. The pedal 192 may schematically refer to a propulsion force pedal. Similarly, the control system 14 may receive an indication of an operator-requested vehicle braking via the human operator 102 or the autonomous controller. For example, the control system 14 may receive sensory feedback from a pedal position sensor 157 in communication with a brake pedal 156.

[0022] Energy storage device 132 may periodically receive electrical energy from a power source residing external to the vehicle (e.g., not part of the vehicle), such as a stationary power grid (not shown). As a non-limiting example, vehicle propulsion system 100 may be configured as a plug-in electric vehicle (EV), whereby electrical energy may be supplied to energy storage device 132 via a power grid (not shown).

[0023] The energy storage device 132 includes an energy storage device controller 139 and a power distribution module 138. The energy storage device controller 139 can provide charge balancing between energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., controller 12). The power distribution module 138 controls the flow of power into and out of the energy storage device 132.

[0024] One or more wheel speed sensors (WSS) 195 may be coupled to one or more wheels of the vehicle propulsion system 100. The wheel speed sensor may detect the rotational speed of each wheel. Such an example of a WSS may include a permanent magnet type sensor.

[0025] The controller 12 may constitute part of a control system 14. In some examples, the controller 12 may be a single controller for the vehicle. The control system 14 is shown as receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). As an example, the sensors 16 may include tire pressure sensors (not shown), wheel speed sensors 195, etc. In some examples, sensors associated with the motor 125, the motor 126, the wheel speed sensors 195, etc. may transmit information about various states of motor operation to the controller 12. The controller 12 includes a non-transitory memory (e.g., read-only memory) 165, a random access memory 166, a digital input / output 168, and a microcontroller 167.

[0026] The vehicle propulsion system 100 may also include an onboard navigation system 17 (e.g., a global positioning system) on the dashboard 19, with which the operator of the vehicle can interact. The navigation system 17 may include one or more position sensors for assisting in estimating the location of the vehicle (e.g., geographic coordinates). For example, the onboard navigation system 17 may receive signals from GPS satellites 33 and identify the geographic location of the vehicle from the signals. In some examples, the geographic location coordinates may be transmitted to the controller 12. The navigation system may also divide the driving route into actual total number of road segments so that vehicle operation in the road segments may be predicted. The navigation system 17 may transmit data from the driving route to the controller 12.

[0027] The instrument panel 19 may also include a display system 18 configured to display information to the vehicle operator. As non-limiting examples, the display system 18 may include a touch screen or a human-machine interface (HMI), i.e., a display that enables the vehicle operator to view graphical information and input commands. In some examples, the display system 18 may be wirelessly connected to the Internet (not shown) via a controller (e.g., 12). Thus, in some examples, the vehicle operator may communicate with an Internet website or software application (app) via the display system 18.

[0028] The instrument panel 19 may also include an operator interface 15, via which the vehicle operator can adjust the operating state of the vehicle. Specifically, the operator interface 15 may be configured to initiate and / or terminate the operation of the vehicle driveline (e.g., motor 125 and motor 126) based on operator input. Various examples of the operator ignition interface 15 may include an interface that requires a physical device (such as an active key) that can be inserted into the operator interface 15 to start the motors 125 and 126 and turn on the vehicle, or can be removed to turn off the motors 125 and 126 to turn off the vehicle. Other examples may include a passive key that is communicatively coupled to the operator interface 15. The passive key may be configured as an electronic key fob or a smart key that does not have to be inserted into the interface 15 or removed from the interface to operate the vehicle motors 125 and 126. Instead, the passive key may need to be located inside the vehicle or near the vehicle (e.g., within a threshold distance of the vehicle). Other examples may additionally or alternatively use a start / stop button that is manually pressed by an operator to start or stop motors 125 and 126 to turn the vehicle on or off. In other examples, remote motor starting may be initiated by a remote computing device (not shown), such as a cell phone or smartphone-based system, where the user's cell phone sends data to a server, and the server communicates with controller 12 to start the engine.

[0029] refer to Figure 2 , a schematic diagram of a vehicle 10 having a non-limiting cooling system 200 is shown. Solid flow direction arrows (e.g., 204) represent conduits and illustrate the direction of coolant and refrigerant flow in the cooling system 200 when the cooling system 200 is operating in a cooling mode. The vehicle 10 may have any suitable drive train and may include one or more electric machines (e.g., such as electric motors) that may be used to propel the vehicle 10 and / or power vehicle components. Figure 1 125 shown in FIG. 125). Alternatively, the vehicle may be a hybrid vehicle. The vehicle 10 may include a passenger compartment 250 and a cooling system 200. The device and fluid passage or conduit are Figure 2 The electrical connections are shown as solid lines. Figure 2 is shown as a dashed line.

[0030] The cooling system 200 includes a coolant loop 260 in which a cooled coolant can be circulated as indicated by a coolant flow arrow (e.g., 201). The coolant loop 260 includes the electric energy storage device 132, other devices 202 (e.g., power converters, etc.) that can be cooled by the coolant that has been cooled by the cooler 206 (e.g., an air-to-liquid heat exchanger), a coolant pump 218, the cooler 206, and a coolant temperature sensor 233. The coolant that has been cooled by the cooler can cool the electric energy storage device 132 and the other devices 202. The coolant pump 218 can circulate the coolant in the coolant loop 260.

[0031] The cooling system 200 also includes a refrigerant circuit 262, in which the refrigerant can be circulated as indicated by the refrigerant flow arrows (e.g., 203). The refrigerant circuit 262 includes a cooler 206, an evaporator 208, an electrically driven compressor 214, an integrated temperature and pressure sensor 230, a pressure sensor 244, a water-cooled condenser 216, an external heat exchanger 212, a first expansion valve 232, and a second expansion valve 234. The refrigerant that has been compressed via the electrically driven compressor 214 can be condensed and cooled by the water-cooled condenser and the external heat exchanger 212 before the refrigerant expands at the first expansion valve 232 or the second expansion valve 234. The expanded refrigerant can cool the liquid coolant in the cooler 206. In addition, the expanded refrigerant can cool the air in the passenger compartment 250 via the evaporator 208. The evaporator sensor 242 can provide an indication of the temperature at the fins of the evaporator 208. The air is cooled by passing the air through the fins.

[0032] The controller 12 (e.g., a vehicle system controller) can adjust the speed of the electrically driven compressor 214 by controlling the current flowing to the electrically driven compressor 214. The integrated temperature and pressure sensor 230 can provide the controller 12 with the refrigerant temperature on the inlet side 214a of the electrically driven compressor 214. The integrated temperature and pressure sensor 230 is positioned downstream of the cooler 206 and upstream of the electrically driven compressor 214 according to the direction of the refrigerant flow. The pressure sensor 244 can provide an indication of the refrigerant pressure on the outlet side 214b of the electrically driven compressor 214 to the second controller 220. The controller 12 can also adjust the position of the first expansion valve 232 and the second expansion valve 234 via the power controlled by the controller 12.

[0033] The second controller 220 may adjust the position of the vehicle grille shutter 222 and the speed of the cooling fan 224 via the electric power controlled by the second controller 220. For example, as the refrigerant pressure on the outlet side of the electrically-driven compressor 214 increases, the second controller 220 may increase the opening amount of the vehicle grille shutter 222 and increase the speed of the cooling fan 224.

[0034] Figure 1 and Figure 2 A system provides a vehicle system, the vehicle system comprising: a cooling system, the cooling system comprising a compressor, an evaporator, a cooler, an external heat exchanger, and a water-cooled condenser; and a controller, the controller comprising executable instructions stored in a non-transitory memory, the executable instructions causing the controller to adjust the speed of the compressor in response to the superheat temperature of the refrigerant being greater than the superheat temperature threshold. In a first example, the vehicle system further comprises additional executable instructions stored in the non-transitory memory, the additional executable instructions causing the controller to estimate the superheat temperature of the refrigerant based on the temperature and pressure of the refrigerant. In a second example that may include the first example, the vehicle system comprises wherein adjusting the speed of the compressor comprises adjusting the speed of the compressor to zero speed. In a third example that may include one or both of the first and second examples, the vehicle system further comprises additional executable instructions stored in the non-transitory memory, the additional executable instructions causing the controller to reduce the speed of the compressor in response to the superheat temperature of the refrigerant being greater than the superheat temperature threshold. In a fourth example, which may include one or more of the first to third examples, the vehicle system further includes additional executable instructions stored in a non-transitory memory, the additional executable instructions causing the controller to count an actual total number of executable instruction cycles that have been executed when the superheat temperature is greater than the superheat temperature threshold. In a fifth example, which may include one or more of the first to fourth examples, the vehicle system includes wherein the controller adjusts the speed of the compressor after a predetermined amount of time has passed since the last time the superheat temperature of the refrigerant changed from less than the superheat temperature threshold to greater than or equal to the superheat temperature threshold. In a sixth example, which may include one or more of the first to fifth examples, the vehicle system includes wherein the superheat temperature is based only on the temperature and pressure upstream of the compressor and downstream of the cooler.

[0035] Reference now Figure 3 , showing that according to Figure 4 An exemplary predictive cooling system operation sequence of a method is provided. Figure 3 The graphs are aligned in time. Figure 3 The sequence can be Figure 1 and Figure 2 system and Figure 4 The vertical line from time t0 to t2 represents the time of interest in the curve graph.

[0036] from Figure 3The first graph from the top of FIG. 3 is a graph of cooling system diagnostic status versus time. The vertical axis represents cooling system diagnostic status, and when trace 302 is at a lower level near the horizontal axis, cooling system diagnostics is not active. When trace 302 is at a higher level near the vertical axis arrow, cooling system diagnostics is active. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace 302 represents cooling system diagnostic status.

[0037] from Figure 3 The second graph from the top of FIG. 3 is a graph of compressor speed versus time. The vertical axis represents compressor speed, and compressor speed increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Horizontal line 350 represents a threshold compressor speed. Line 304 represents compressor speed.

[0038] from Figure 3 The third graph from the top of is a graph of superheat temperature values ​​of the refrigerant in the cooling system. The superheat temperature value can be represented as the current refrigerant temperature minus the boiling point temperature of the refrigerant when the refrigerant is in a liquid state. The superheat temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. The horizontal line 352 represents the threshold superheat temperature value. Line 306 represents the superheat temperature value of the refrigerant in the cooling system.

[0039] from Figure 3 The fourth graph from the top of is a graph of timer value versus time. The vertical axis represents the timer value, and the timer value increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Line 308 represents the timer value. Horizontal line 354 represents a threshold amount of time.

[0040] At time t0, the compressor diagnostic is not activated and the compressor speed is above the threshold compressor speed 350. The superheat temperature of the refrigerant in the cooling system is greater than the superheat temperature threshold and the timer value is zero because the diagnostic has not yet started and because

[0041] At time t1, cooling system diagnostics are activated. Cooling system diagnostics may be activated during predetermined conditions (e.g., the vehicle has been operating for a threshold amount of time, the cooling system has been activated for a threshold amount of time, etc.). Since the compressor speed is greater than a threshold compressor speed and since the superheat temperature of the refrigerant is above a superheat temperature threshold, the compressor speed is commanded to a lower speed shortly after time t1. The timer is not activated.

[0042] At time t2, the cooling system diagnostic continues to be active and the compressor speed drops below the compressor threshold speed. This causes the timer to begin accumulating time. Even though the compressor speed has decreased, the superheat temperature remains above the threshold superheat temperature. This may indicate that there may be less refrigerant in the cooling system than expected and / or desired.

[0043] At time t3, the timer value exceeds the timer threshold, but the superheat temperature is still above the superheat temperature threshold, which may indicate a low refrigerant (charge) level. Therefore, the diagnostic ends. In this example, the compressor speed is reduced to zero speed to reduce the possibility of compressor degradation. In addition, other mitigation actions may be taken in response to the superheat temperature value being greater than the superheat temperature threshold. After the compressor speed is reduced, the timer stops counting and the superheat value begins to decrease.

[0044] In this way, the diagnostic can determine whether the cooling system may be degraded. Specifically, an overheat temperature greater than a threshold temperature can indicate that there is less refrigerant in the refrigerant circuit than might be expected. If a low level of refrigerant is detected, the electric compressor can be deactivated to reduce the likelihood of electric compressor degradation.

[0045] Reference now Figure 4 , a method for operating a cooling system of a vehicle is shown. Figure 4 The method may be included as executable instructions stored in a non-transitory memory. Figure 1 and Figure 2 Furthermore, Figure 4 The parts of a method can be actions that the controller takes in the physical world.

[0046] At 402, method 400 judges whether there is no indication of existing cooling system degradation (e.g., no electric air conditioning (eAC) degradation) and no pressure and temperature sensor (PTS) degradation. If there is no cooling system degradation and no pressure and temperature sensor degradation, the answer is yes and method 400 proceeds to 404. Otherwise, the answer is no and method 400 proceeds to 440. The timer and counter values ​​mentioned below may be reset to zero upon entry into the diagnostic or after the diagnostic is completed.

[0047] At 440, method 400 operates the air conditioning (AC) system or heat pump according to basic operation or normal operation. For example, method 400 may adjust the compressor speed according to the cooling load and regardless of the superheat temperature of the refrigerant. Method 400 proceeds to exit.

[0048] At 404, method 400 determines a commanded speed for the AC compressor. In one example, method 400 may command and adjust the speed of the AC compressor based on a difference between a requested passenger cabin temperature and an actual or measured passenger cabin temperature. Additionally, compressor speed may be commanded and adjusted based on a difference between a requested traction battery temperature and an actual traction battery temperature. After commanding and adjusting the electric drive compressor speed according to the basic electric drive compressor speed control routine, method 400 proceeds to 406.

[0049] At 406, method 400 determines whether the speed of the electrically-driven compressor is greater than a first threshold speed of the electrically-driven compressor. In one example, the first threshold speed of the electrically-driven compressor is based on empirically determined data collected while varying ambient temperature, compressor speed, refrigerant charge, etc. If method 400 determines that the current speed of the electrically-driven compressor is greater than the first compressor speed threshold, the answer is yes and method 400 proceeds to 408. Otherwise, the answer is no and method 400 proceeds to 420.

[0050] At 408, method 400 determines whether the superheat temperature of the refrigerant is below a first superheat temperature threshold. If so, the answer is yes, and method 400 proceeds to 410. Otherwise, the answer is no, and method 400 proceeds to 430. In one example, the superheat temperature of the refrigerant may be determined via the following equation:

[0051] Overheat = f(compintemp,compinpress)-refboiltmp

[0052] Where superheat is the estimated superheat temperature of the refrigerant, f is a function of an empirically determined value return temperature based on the electric drive compressor inlet temperature and the electric drive compressor inlet pressure, and refboiltmp is the boiling point temperature of the refrigerant from the liquid phase to the gas phase. By considering both the refrigerant temperature at the compressor inlet and the refrigerant pressure at the compressor inlet, the superheat temperature estimate can be improved. The first superheat temperature threshold is based on empirically determined data collected when the refrigerant amount varies, the compressor speed varies, and the ambient air temperature varies.

[0053] At 410 , method 400 determines whether the superheat temperature of the refrigerant is below a first superheat temperature threshold minus a hysteresis temperature Hyst. If so, the answer is yes and method 400 proceeds to 412. Otherwise, the answer is no and method 400 returns to 404.

[0054] At 412, method 400 decrements a counter and returns to 404. The counter may be included as an instruction stored in a non-transitory memory and used as a basis for reducing the likelihood of compressor degradation. The threshold counter value at 420 may be selected to reduce the impact of noise factors in the system and reduce the risk of system degradation. Method 400 returns to 404.

[0055] At 430, method 400 increments a counter and proceeds to 432. At 432, method 400 reduces the speed of the compressor to a predetermined speed (Speed ​​2). If the amount of refrigerant in the cooling system is greater than a threshold amount (e.g., sufficient not to be considered low), the predetermined speed may be a compressor speed that results in an expected superheat temperature. Method 400 returns to 406.

[0056] At 420 , method 400 determines if the superheat temperature of the refrigerant is greater than a second superheat temperature threshold. If so, the answer is yes and method 400 proceeds to 422 . Otherwise, the answer is no and method 400 returns to 404 .

[0057] At 422 , method 400 maintains the speed of the electrically-driven compressor less than a first threshold speed. Method 400 proceeds to 424 .

[0058] At 424 , method 400 increments a timer (Timer 2 ) and allows the accumulated time to increase. Method 400 proceeds to 426 .

[0059] At 426, method 400 determines whether the value of the timer (Timer 2) is greater than a threshold amount of time. If so, the answer is yes, and method 400 proceeds to 468. Otherwise, the answer is no, and method 400 returns to 420.

[0060] At 428, method 400 may indicate that the refrigerant (charge) is low, and method 400 may perform mitigation actions. The indication of low charge may be displayed via a human-machine interface. Mitigation actions may include, but are not limited to, adjusting the speed of the electrically driven compressor to zero (deactivating the compressor), reducing the load on the cooling system (such as closing one or more expansion valves), and limiting vehicle torque to reduce the load on the chiller, etc. Method 400 proceeds to exit.

[0061] In this way, the method 400 can detect low refrigerant levels without using the temperature and / or pressure upstream of the compressor in the refrigerant circuit. In addition, if a low refrigerant level is detected, the method 400 can take mitigation actions so that the possibility of compressor degradation can be reduced.

[0062] Figure 4A method for operating a cooling system of a vehicle is provided, the method comprising: generating an estimate of a superheat temperature of a refrigerant based on a pressure at an inlet side of a compressor and a temperature at the inlet side of the compressor; and deactivating the compressor in response to the estimate of the superheat temperature of the refrigerant exceeding an overheat threshold temperature. In a first example, the method may include wherein the compressor is deactivated when the estimate of the superheat temperature of the refrigerant exceeds the overheat threshold temperature for a predetermined amount of time. In a second example that may include the first example, the method includes wherein the overheat threshold temperature is based on an ambient temperature and a rotation speed of the compressor. In a third example that may include one or both of the first and second examples, the method includes wherein the superheat temperature is a current temperature of the refrigerant minus a boiling point temperature of the refrigerant in a liquid state. In a fourth example that may include one or both of the first to third examples, the method includes wherein the estimate of the superheat temperature is determined in the absence of a pressure downstream of the compressor and upstream of an expansion valve. In a fifth example that may include one or both of the first to fourth examples, the method includes wherein the temperature and pressure are downstream of a cooler and upstream of a compressor. In a sixth example, which may include one or more of the first to fifth examples, the method further includes commanding the compressor to a certain speed based on a temperature difference. In a seventh example, which may include one or more of the first to sixth examples, the method includes wherein the temperature difference is a difference between a requested passenger cabin temperature and a measured passenger cabin temperature.

[0063] Figure 4The method of also provides a method for operating a cooling system of a vehicle, the method comprising: adjusting a speed of a compressor in response to a user requested temperature; generating an estimate of a superheat temperature of a refrigerant based on a pressure at an inlet side of the compressor and a temperature at the inlet side of the compressor; reducing the speed of the compressor to a reduced speed in response to the superheat temperature of the refrigerant being above an overheat threshold temperature; generating the estimate of the superheat temperature of the refrigerant based on the pressure at the inlet side of the compressor and the temperature at the inlet side of the compressor; and deactivating the compressor in response to the compressor being at the reduced speed and the estimate of the superheat temperature of the refrigerant exceeding the overheat threshold temperature. In a first example, the method includes wherein deactivating the compressor includes reducing the speed of the compressor to zero. In a second example that may include the first example, the method also includes providing an indication of a loss of refrigerant in response to the superheat temperature of the refrigerant exceeding an overheat threshold temperature. In a third example, which may include one or both of the first and second examples, the method further includes cooling a battery and a passenger compartment of the vehicle via the cooling system while generating the estimate of the superheat temperature of the refrigerant. In a fourth example, which may include one or more of the first to third examples, the method includes wherein the battery is a traction battery.

[0064] As will be understood by one of ordinary skill in the art, Figure 4 The methods described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threaded processing strategies, etc. Thus, the various steps or functions shown may be performed in the sequence shown, may be performed in parallel, or may be omitted in some cases. Likewise, the processing order is not necessarily required to achieve the objectives, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly shown, one of ordinary skill in the art will recognize that one or more of the steps or functions shown may be repeatedly performed depending on the specific strategy used. In addition, the methods described herein may be a combination of actions taken by a controller in the physical world and instructions within the controller. At least a portion of the control methods and programs disclosed herein may be stored as executable instructions in a non-transitory memory and may be executed by a control system including a controller in combination with various sensors, actuators, and other system hardware.

[0065] This description ends here. Many variations and modifications will occur to those skilled in the art after reading this description without departing from the spirit and scope of this description. For example, the systems and methods described herein can be applied to all-electric vehicles and vehicles that include an engine and an electric motor for propulsion.

Claims

1. A method for operating a cooling system of a vehicle, comprising: generating an estimate of a superheat temperature of the refrigerant based on a pressure at an inlet side of a compressor and a temperature at the inlet side of the compressor; as well as In response to the estimate of the superheat temperature of the refrigerant exceeding a superheat threshold temperature, the compressor is deactivated. 2 . The method of claim 1 , wherein the compressor is deactivated when the estimated value of the superheat temperature of the refrigerant exceeds the superheat threshold temperature for a predetermined amount of time. 3 . The method of claim 2 , wherein the overheat threshold temperature is based on an ambient temperature and a rotational speed of the compressor.

4. The method of claim 3, wherein the superheat temperature is the current temperature of the refrigerant minus the boiling point temperature of the refrigerant in a liquid state.

5. The method of claim 1 wherein said estimate of said superheat temperature is determined in the absence of a pressure downstream of said compressor and upstream of an expansion valve.

6. The method of claim 1 wherein the temperature and pressure are downstream of a cooler and upstream of the compressor.

7. The method of claim 1 further comprising commanding the compressor to a speed based on a temperature differential. 8 . The method of claim 7 , wherein the temperature difference is a difference between a requested passenger cabin temperature and a measured passenger cabin temperature.

9. A vehicle system comprising: a cooling system comprising a compressor, an evaporator, a cooler, an external heat exchanger and a water-cooled condenser; and A controller includes executable instructions stored in a non-transitory memory, the executable instructions causing the controller to adjust a speed of the compressor in response to a superheat temperature of the refrigerant being greater than a superheat temperature threshold.

10. The vehicle system of claim 9 further comprising additional executable instructions stored in non-transitory memory, the additional executable instructions causing the controller to estimate the superheat temperature of the refrigerant based on the temperature and pressure of the refrigerant.

11. The vehicle system of claim 9, wherein adjusting the speed of the compressor comprises adjusting the speed of the compressor to zero speed.

12. The vehicle system of claim 9 further comprising additional executable instructions stored in non-transitory memory, the additional executable instructions causing the controller to reduce the speed of the compressor in response to the superheat temperature of the refrigerant being greater than the superheat temperature threshold.

13. The vehicle system of claim 9 further comprising additional executable instructions stored in non-transitory memory, the additional executable instructions causing the controller to count an actual total number of executable instruction cycles that have been executed while the superheat temperature is greater than the superheat temperature threshold.

14. The vehicle system of claim 9, wherein the controller adjusts the speed of the compressor after a predetermined amount of time has passed since a last time the superheat temperature of the refrigerant changed from less than the superheat temperature threshold to greater than or equal to the superheat temperature threshold.

15. The vehicle system of claim 9, wherein the superheat temperature is based only on temperature and pressure upstream of the compressor and downstream of the cooler.

Images