Diagnostic procedure for relay-controlled multi-speed electric fan

Abstract

A method for a relay-controlled multi-speed cooling fan system coupled to an engine (10), comprising: if other electrical loads are stable: Measuring a current when a fan speed changes; and Indicate fan system degradation based on a relative change in current.

Description

[0001] The present application relates to the diagnosis of a multi-speed engine cooling fan system of a vehicle cooling system.

[0002] Vehicle cooling systems can include various cooling components such as radiators, cooling fans and blowers, condensers, coolants, etc. An electric engine cooling fan can be driven by an electric motor, either variable-speed or relay-controlled. An electric fan controlled by a variable-speed motor can be diagnosed by intelligent controllers connected to the powertrain control module (PCM).

[0003] Another exemplary approach is shown by Wiltsch (US 2011 / 0 199 036 A1), where a cooling fan is diagnosed by measuring a current after the fan is controlled by a predefined signal. A current measuring device is coupled to a fan, which can be controlled to the "on," "off," or intermediate positions. After the fan is controlled, the device detects a current signal, which is then compared to a predefined threshold. Any deviation from the predefined threshold leads to a determination of a malfunctioning fan.

[0004] US 2008 / 0 100 237 A1 is known from the prior art. This describes a multi-motor system in which a relay circuit enables the motors to be switched on and off, allowing the system to operate at different power levels.

[0005] Also known is US 2005 / 0 118 029 A1. This describes the diagnosis of a cooling fan by comparing a measured current of the cooling fan with a specified upper and lower threshold value and then determining whether the cooling fan is malfunctioning.

[0006] US 4 658 595 A is also known from the prior art. This describes a cooling system for a radiator and a condenser using two fans, one of which can be switched on and off as required by a relay circuit.

[0007] However, the inventors have identified potential problems with the above approaches. In the example of a relay-controlled fan, the diagnostic capability is limited due to the lack of intelligent controls. This problem is particularly exacerbated in a multi-speed fan system containing multiple relays. Accordingly, the current measurement approach can also introduce errors into the vehicle's electrical system due to the presence of other electrical loads that may draw current from the same voltage source as the fan, as well as unexpected or unknown transitions in such loads. Interference from such electrical loads can therefore lead to incorrect current measurements for the fan and, consequently, to a misdiagnosis of the cooling fan's degradation.

[0008] The inventors have recognized the above problem and devised an approach to at least partially address the problem. In one exemplary approach, a diagnostic method for a relay-controlled multi-speed fan system is provided. The method includes measuring the change in current drawn from a battery-alternator system as the fan speeds are varied while the vehicle is traveling at low speed while maintaining other electrical loads in a more stable state. Further, the difference between the current drawn before and after a modification of the fan speed is compared to an expected difference, and a degradation is indicated if the absolute value of a relative current change is above an expected error threshold.

[0009] For example, a fan diagnostic may be activated while the vehicle is traveling at low speed and major electrical loads such as an air conditioner or rear window defogger are in a steady state. The PCM may command a change in the fan speed, and once the speed has stabilized, several current draw readings are taken. For example, the fan speed may be changed from a stop or "off" position to a "low" speed state. Before changing the speed, the current drawn from the battery-alternator system when the fan system is in an "off" position may be measured. Once the fan speed has stabilized in the "low" speed position, the current drawn from the battery-alternator system may be measured.The difference between the current drawn in an "off" position and the current drawn at "low" speed can be calculated and compared to an expected difference to obtain a relative error based on an expected change. If the calculated absolute error exceeds an expected threshold, a fan degradation may be detected. After multiple degradation detections, a malfunction indicator light may illuminate on the instrument panel.

[0010] In this way, a multi-speed cooling fan system powered by relay-controlled motors can be tested for degradation without requiring additional modifications to existing hardware or additional sensors, thus minimizing costs. By running the diagnostics when other electrical loads are under more stable conditions, or by delaying requested changes to the other electrical loads, any change in the current drawn from the battery-alternator system can be attributed to the cooling fan system. Furthermore, the cooling fan diagnostics can be disabled when other electrical loads are fluctuating to minimize noise and errors.

[0011] It should be understood that the above summary is provided to introduce, in a simplified form, a selection of concepts further described in the detailed description. It is not intended to identify principal or essential features of the claimed subject matter, the scope of which is defined solely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve the disadvantages noted above or elsewhere in this disclosure. Fig. 1 is a schematic representation of a cooling system in a motor vehicle. Fig. 2 shows an example block diagram of a fan diagnostic logic. Fig. 3A, Fig. 3B and Fig. 3C show schematic diagrams for single-speed, dual-speed, and triple-speed fans, respectively. Fig. Figure 4 is an example flowchart illustrating a diagnostic routine for a relay-controlled cooling fan. Fig. 5 is an example of how a fan diagnosis works based on vehicle conditions.

[0012] The following description relates to systems and methods for diagnosing a cooling fan system in a vehicle cooling system such as that in Fig. 1. Multi-speed fans using relay-controlled electric motors, such as those in Fig. 3A, Fig. 3B and Fig. 3C can be replaced by an example fan diagnostic logic as shown in Fig. 2, be diagnosed for a functional impairment. A controller may be configured to execute a routine such as the exemplary routine of Fig. 4 to detect a cooling fan degradation based on a relative current drawn from the battery-alternator system. The diagnosis is activated when certain vehicle conditions are met, in particular that other electrical loads are stable ( Fig. 5).

[0013] Fig. 1 is a schematic representation of one embodiment of a vehicle cooling system 100 in a motor vehicle 102. The vehicle 102 includes drive wheels 106, a passenger compartment 104, and an engine compartment 103. The engine compartment 103 may house various engine compartment components under the hood (not shown) of the motor vehicle 102. For example, an internal combustion engine 10 may be housed in the engine compartment 103. The internal combustion engine 10 includes a combustion chamber that may receive intake air via an intake passage 44 and expel combustion gases via an exhaust passage 48. In one example, the intake passage 44 may be configured as a ram air intake, wherein the dynamic pressure generated by the moving vehicle 102 may be utilized to increase a static air pressure in the engine's intake manifold.This may therefore allow for greater air mass flow through the engine, thereby increasing engine power. The engine 10 illustrated and described herein may be included in a vehicle, such as a road vehicle, among other vehicle types. Although the exemplary applications of the engine 10 are described with respect to a vehicle, it should be understood that engines and vehicle propulsion systems of various types may be used, including passenger cars, trucks, etc.

[0014] The engine compartment 103 may also include a cooling system 100 that circulates coolant through the internal combustion engine 10 to absorb waste heat and distributes the heated coolant to the radiator 80 and / or heater core 55 via coolant lines 82 and 84, respectively. In one example, the cooling system 100 may be coupled to an engine 10, as shown, and circulates engine coolant from the engine 10 to the radiator 80 via an engine-driven water pump 86 and back to the engine 10 via the coolant line 82. The engine-driven water pump 86 may be coupled to the engine via a front end accessory drive (FEAD) 36 and rotate via a belt, chain, etc., in proportion to engine speed. In particular, the engine-driven pump 86 may circulate coolant through passages in the engine block, head, etc.to absorb engine heat, which is then transferred to the ambient air via the radiator 80. In an example where the engine-driven water pump 86 is a centrifugal pump, the pressure (and resulting flow) generated by the pump may be proportional to the crankshaft speed, which in the example of . Fig. 1 may be directly proportional to the engine speed. The temperature of the coolant may be controlled by a thermostatic valve 38 disposed in the coolant line 82, which may be kept closed until the coolant reaches a threshold temperature.

[0015] The coolant may flow through the coolant line 82, as described above, and / or through the coolant line 84 to the heater core 55, where heat may be transferred to the passenger compartment 104 and the coolant may flow back to the engine 10. In some examples, the engine-driven pump 86 may be operated to circulate the coolant through both coolant lines 82 and 84.

[0016] One or more blowers (not shown) and cooling fans may be included in cooling system 100 to provide airflow assistance and increase cooling airflow through the underhood components. For example, cooling fans 91 and 95, coupled to radiator 80, may be operated when the vehicle is moving and the engine is running to provide cooling airflow assistance through radiator 80. Cooling fans 91 and 95 may draw a cooling airflow into engine compartment 103 through an opening at the front end of vehicle 102, such as through grille 112. Such cooling airflow may then be utilized by radiator 80 and other underhood components (e.g., fuel system components, batteries, etc.) to keep the engine and / or transmission cool. Further, the airflow may be utilized to expel heat from a vehicle air conditioning system.Additionally, the airflow may be used to improve the performance of a turbocharged / supercharged engine equipped with intercoolers that reduce the temperature of the air entering the intake manifold / engine. While this embodiment describes two cooling fans, other examples may use only a single cooling fan.

[0017] Cooling fans 91 and 95 may be coupled to a battery-powered motor 93 and 97, respectively. During engine operation, the torque generated by the engine may be transmitted along a driveshaft (not shown) to the alternator 72 and then utilized by the alternator 72 to generate electrical power, which is stored in an electrical energy storage device such as the system battery 74. The battery 74 may then be used to activate cooling fan electric motors 93 and 97 via relays (not shown). Operating the cooling fan system may therefore include electrically driving the cooling fan rotation from the engine rotation input through the alternator and the system battery, for example, when the engine speed is below a threshold (for example, when the engine is idle-stop).In further embodiments, the cooling fan may be operated by activating a variable-speed electric motor coupled to the cooling fan. In further embodiments, cooling fans 91 and 95 may be mechanically coupled to engine 10 via a clutch (not shown), and operating the cooling fans may include mechanically driving their rotation from the rotational output of the engine via the clutch.

[0018] The engine compartment 103 may also include an air conditioning (AC) system including a condenser 88, a compressor 87, a liquid receiver with dryer core 83, an expansion valve 89, and an evaporator 85 coupled to a blower (not shown). The compressor 87 may be coupled to the engine 10 via the FEAD 36 and an electromagnetic clutch 76 (also known as a compressor clutch 76), which allows the compressor to engage or disengage from the engine based on the AC system's on / off cycles. The compressor 87 may pump pressurized refrigerant to the condenser 88, which is mounted at the front of the vehicle. The condenser 88 may be cooled by cooling fans 91 and 95, which cool the refrigerant as it flows through.The high-pressure refrigerant exiting the condenser 88 may flow through the liquid receiver with dryer core 83, where any moisture in the refrigerant may be removed by dehumidifiers. The expansion valve 89 may then depressurize the refrigerant and allow it to expand before entering the evaporator 85, where it may be vaporized into a gaseous state while cooling the passenger compartment 104. The evaporator 85 may be coupled to a forced draft fan driven by a motor (not shown) operable by the system voltage.

[0019] The system voltage can also be used to power an entertainment system (radio, speakers, etc.), electric heaters, windshield wiper motors, a rear window defogger, and headlights, among other systems.

[0020] Fig. 1 also shows a control system 14. The control system 14 may be communicatively coupled to various components of the engine 10 to perform the control routines and operations described herein. For example, the control system 14 may be configured as shown in Fig. 1, an electronic digital controller 12. The controller 12 may be a microcomputer having a microprocessor unit, input / output ports, an electronic storage medium for executable programs and calibration values, random access memory, retention memory, and a data bus. As shown, the controller 12 may receive inputs from a plurality of sensors 16, which may include inputs from users and / or sensors (such as transmission gear position, accelerator pedal input, brake input, transmission selector position, vehicle speed, engine speed, ambient temperature, intake air temperature, etc.), cooling system sensors (such as coolant temperature, fan speed, passenger compartment temperature, ambient humidity, etc.), and others (such as Hall-effect current sensors from the alternator and battery, system voltage regulators, etc.).Additionally, the controller 12 may communicate with various actuators 18, which may include engine actuators (such as fuel injectors, an electronically controlled intake air throttle, spark plugs, etc.), cooling system actuators (such as engine switching relays, etc.), and others. In some examples, the storage medium may be programmed with computer-readable data representing instructions executable by the processor to perform the methods described below, as well as other variations that are anticipated but not specifically listed.

[0021] The engine controller 12 may adjust the operation of the cooling fans 91 and 95 based on vehicle cooling demand, vehicle operating conditions, and in coordination with engine operation. In one example, during a first vehicle motion condition, when the engine is operating and vehicle cooling and airflow assistance from the fan is desired, the cooling fans 91 and 95 may be driven by activating battery-powered electric motors 93 and 97 to provide airflow assistance for cooling underhood components. The first vehicle motion condition may include, for example, an engine temperature being above a threshold.In another example, during a second vehicle motion state, when airflow assistance is not desired (for example, due to sufficient airflow through the engine compartment caused by airflow), fan operation may be interrupted by deactivating the fan motor. In another example, during a third vehicle motion state, when an air conditioning system is operating, cooling fans 91 and 95 may be activated to facilitate cooling of the air conditioning system's condenser 88.

[0022] Now on Fig. Referring to Figure 2, schematic diagnostic logic for detecting a degraded cooling fan is shown in block diagram 200. An engine controller may be configured to use logic such as that shown at 200 to determine when conditions for performing a diagnostic are met and to initiate the cooling fan system diagnostics once they are met.

[0023] Before starting the diagnostics, the controller 202 may receive inputs from various sensors to determine whether necessary diagnostic preconditions are met. For example, the controller 12 may receive information from a vehicle speed sensor at 212. The controller 12 may confirm whether the vehicle speed is below a threshold to avoid measuring the fan current when the fan is rotated by airflow from the vehicle's wind. The controller 12 may also check whether the charging system voltage 206 is maintained within a specified range using an analog-to-digital converter (ADC) to measure the system voltage at the controller. A charging voltage that is above or below a threshold, for example, may cause the fan to operate outside of its characteristic range, and the diagnostics may therefore be unable to predict the expected current.

[0024] Additionally, the controller 12 may also receive signals from sensors regarding the status of other electrical loads 216, such as an air conditioning system, rear window defogger, headlights, etc., which may draw power from the battery-alternator system. For example, when an air conditioning system is activated, cooling fan speeds may be increased to allow cooling of the condenser and refrigerant. Furthermore, the electromagnetic clutch connecting the compressor to the engine may also draw power from the battery-alternator system. Therefore, the controller 12 may deactivate the cooling fan diagnostics when the status of the air conditioning system changes.

[0025] Once the controller 12 determines that diagnostic preconditions are met, it may communicate with low-side drivers 218 to activate relays via fan control signals FC1, FC2, and FC3. Relays may be controlled based on desired fan speed commands 204 to operate the fan system at "low," "medium," or "high" speed, or to shut down the entire system. The controller 12 may receive data about current drawn from the system from the battery current sensor 208 and alternator current sensor 210. Current measurements may be obtained using Hall-effect current sensors coupled to power lines from the alternator and battery. The total battery-alternator system current may be determined by summing current measurements from the battery and alternator.

[0026] In another example for a vehicle with a simpler configuration, the duty cycle of the alternator excitation field can be used to estimate the alternator current while neglecting the battery current.

[0027] Diagnostic test results may be transmitted to the Diagnostic Trouble Code (DTC) Manager 214 if a malfunction indicator lamp on the instrument panel needs to be turned on.

[0028] Now Fig. 3A, Fig. 3B and Fig. 3C, where example relay configurations are shown for a single-speed fan, a dual-speed fan, and a triple-speed fan, respectively. Fig. Figure 3A shows a circuit diagram for a single speed fan 92 driven by a motor 94 controlled by a relay 31. Relay 31 may be a normally open (NO) switch, as in Fig. 3A, where the switch closes to complete a circuit when the relay coil is energized. In another example, relay 31 may be a normally closed (NC) switch that breaks a circuit when the electromagnetic coil is energized. Relay 31 may be remotely activated by a fan control signal FC1 from the controller (also known as the powertrain control module (PCM)) when fan operation is required. The electromagnetic coil in relay 31 may be energized via the system voltage VPWR (also known as vehicle current VPWR), as shown in Fig. 3A, or in other examples, may be coupled to the ignition circuit (not shown). Thus, relay 31 allows a large load, such as motor 94 connected to fan 92, to be driven by a lower current circuit.

[0029] Fan 92 and motor 94 form a single-speed fan system controlled by a single relay. Upon receipt of signal FC1 from the PCM, relay 31 is energized, and the normally open switch closes the circuit to enable operation of fan 92 via motor 94, which draws power from battery 74.

[0030] Now Fig. 3B, which shows a two-speed fan system operated by three relays 31, 33, and 35. Fans 91 and 95, coupled to motors 93 and 97, respectively, may be connected to battery 74 in various ways depending on which relay is energized. Relay 35 is shown as a changeover (CO) or double throw (DT) contact controlling two circuits with a normally open (NO) switch and a normally closed switch, while relays 31 and 33 have NO switches. Relays 31, 33, and 35 may be controlled by signals FC1 and FC2 received from the PCM, whereupon the electromagnetic coils may be energized via system voltage VPWR. For example, relay 31 may be energized upon receipt of signal FC1, completing a circuit with fans 91 and 95 in series with battery 74.Because fans 91 and 95 are arranged sequentially in a series circuit, there is greater resistance in the circuit, resulting in low-speed fan operation. In another example, the fan system may receive signals FC1 and FC2 simultaneously, causing all relays to switch and complete a circuit in which fans 91 and 95 are arranged in a parallel circuit. In a parallel circuit, each fan is arranged in its own circuit, which presents less resistance to current flow and thereby allows the fan system to rotate at a higher speed. In this way, a system with three relays and two fan motors can provide dual-speed fan operation.

[0031] Now Fig. 3C, where a three-speed fan system is shown, comprising 2 fan motors and 5 relays. The Fig. The circuit shown in Figure 3C includes relays 31, 33, 35, 37, and 39, of which relays 31 and 37 comprise NO switches, while relays 33, 35, and 39 comprise CO switches. In their de-energized state, relays 35 and 39 are connected to resistors 51 and 53, respectively. The circuit also includes fuses 23, 25, and 27 to protect the circuit and components from excessive current flow. Relay 31 is controlled by a signal FC1, relays 33 and 37 are controlled by a signal FC2, and relays 35 and 39 are activated by a signal FC3 from the controller. Finally, fans 91 and 95, coupled to motors 93 and 97, respectively, can receive power from battery 74 when the circuits are closed by the operation of various relay combinations.

[0032] For example, fans 91 and 95 can be caused to operate at low speed by issuing signals FC1 and FC3 to activate relays 31 and 35, respectively, thereby connecting fan 95 via motor 97 and fan 91 via motor 93 in series with battery 74. Note that signal FC3 also activates relay 39 to remove resistor 53, but relay 37 remains inactivated, and motor 93 receives power only via the series circuit. As previously discussed on Fig. 3B, with two fans arranged sequentially in this circuit, there is more resistance to the current flow, which allows for low-speed fan operation.

[0033] In another example, relays 31, 33, and 37 may be activated simultaneously by signals FC1 and FC2. Relays 31 and 37 are energized to close the circuit to battery 74, while activation of relay 33 allows resistors 51 and 53 to be connected in series with motors 97 and 93, respectively. The closed circuit therefore now includes fans 91 and 95, each connected in series with a single reduction resistor. By energizing relays 31, 33, and 37, fans 91 and 95 are connected in parallel with each other, allowing greater current flow and therefore a comparatively higher fan system speed through fan motors 93 and 97. However, resistors 51 and 53 increase the resistance value, and therefore the overall fan system speed when receiving signals FC1 and FC2 can be referred to as "medium" speed.

[0034] In another example, the fan system can be controlled by signals FC1, FC2, and FC3, which energize all relays simultaneously. Here, fans 91 and 95 are connected in parallel when relays 31 and 37 are activated to close the two circuits. Additionally, resistors 51 and 53 are removed from each circuit when relays 35 and 39 are activated, allowing higher current flow and thus "high speed" operation of the fan system.

[0035] In this way, by using a combination of relays coupled to one or more fan motors, a multi-speed fan system can be operated to assist in cooling the engine. Depending on the coolant temperature and the desired level of cooling, the controller can activate various relays to change the fan speed from "low" to "medium" or "high." Furthermore, the current drawn by the system when various relays are activated can be measured to estimate any degradation of the fan system. Fig. 3C For example, if medium speed operation is desired and signals FC1 and FC2 are issued to activate relays 31, 33, and 37 to change the fan speed from off to medium, the current drawn will increase by a certain amount. If the fan speed is to be reduced to low, relays 33 and 37 are deactivated, relays 35 and 39 are activated, and the current drawn will decrease from the previous speed. At each speed change, an expected current draw can be known depending on which plurality of relays are activated. If the measured current change deviates from an expected change, it can be determined which relay or combination of relays may be degraded.

[0036] In another example, with reference to Fig. 3B, activating relay 31 results in a low-speed fan system, and a change in current is measured and compared with an expected change. If the change in absorbed current deviates from an expected change, a degradation in relay 31 and, to a lesser extent, in relay 35 may be indicated. On the other hand, by activating relays 31, 33, and 35 and comparing the changes in absorbed current with an expected change, the condition of these three relays can be diagnosed. By comparing the results with the previous measurement, a degradation in function can be isolated to specific relays. For example, if the change in absorbed current measured in the previous measurement is comparable to an expected change in absorbed current, it is very likely that relay 31 is robust.If the change in the current drawn, measured in the subsequent measurement, deviates from an expected current change, it can be inferred that relay 33 or, to a lesser extent, relay 35 is defective.

[0037] Now on Fig. Referring to Figure 4, an exemplary diagnostic routine 400 is illustrated that may be executed by a controller to check for cooling fan degradation in a relay-controlled system. Fan speeds may be varied, and the current draw at each speed may be measured. The change in current draw when varying the fan speed may then be compared to an expected change to diagnose the presence of fan degradation.

[0038] At 402, the routine includes estimating whether the vehicle operating conditions necessary to perform the fan diagnostics are met. These conditions may include vehicle speed, battery state of charge, ambient temperature, module voltage, etc. For example, the diagnostics are only enabled at a vehicle speed below a threshold. If it is determined that the vehicle speed is higher than a threshold, the controller may delay the diagnostics due to significant airflow associated with the higher vehicle speed causing the fan to rotate due to the airflow, thereby reducing power requirements and introducing unaccounted-for error into the calculation.

[0039] In another example, the controller may wait until the voltage regulator can maintain the system voltage between a minimum and a maximum. If the regulated system voltage is outside a voltage window, the expected fan current may not be characteristic at that operating voltage, and therefore the expected current change may not be accurately known.

[0040] If it is determined at 402 that the preconditions are not met, the routine returns to start. Once the preconditions are met, the controller may confirm at 404 that electrical loads other than the fan system that draw current from the battery-alternator system have stabilized. For example, it may determine whether or not the air conditioning system is operating. If the air conditioning system has just been activated, the current drawn from the system may change when the electromagnetic compressor clutch is engaged. However, once the current has stabilized, the controller may proceed to perform the fan diagnostics. In one example, the current drawn by the air conditioning system from a battery-alternator system may be considered stabilized if it varies by less than 3%.In other examples, the variance threshold for determining that other loads are stable may be set to 5%; the other loads may include, for example, an air conditioning compressor load. In any case, the controller may wait to activate the diagnostic until such loads are either further stabilized or ineffective.

[0041] If it is determined that other major electrical loads are unstable or in transient states, or an expected change is pending due to driver input, the diagnostic may be deactivated at 406, and the routine may return to the start. On the other hand, if it is confirmed that other electrical loads are steady, the routine proceeds to 408, where the controller actively limits changes to other electrical loads to prevent transient states. Thus, not only does the controller detect conditions in which the electrical loads do not change by more than a threshold, but the controller may also delay requests from other systems to change the electrical loads. For example, even if an HVAC system requests deactivation of the air conditioning compressor, the routine may delay deactivation until the diagnostic routine identifies the change in current due to a change in fan speed.

[0042] To continue with routine 400, the current drawn from the battery-alternator system is determined at 410 as C premeasured. This current may be current drawn at a given time by electrical loads, including the cooling fan, if the cooling fan is already operating. For example, if the air conditioner is running, the fans may be operated at a "medium" speed to facilitate cooling of the condenser. In another example, the cooling fans may be turned off and out of operation, and the current measurement may include all electrical loads except the fan. At 412, the controller may command a change in fan speed. For example, if the fan system is already at a "medium" speed, the fans may be accelerated to a "high" position or decelerated to a "low" position. In another example, the fan system may be commanded from an "off" position to a "low" speed position.

[0043] Once a speed change has been executed and the fan speeds have stabilized, current drawn from the battery-alternator system is measured at 414 as Cpost. Next, at 416, a difference in the current drawn before and after the fan speed change is calculated as ΔCurrent_actual. The net current change when varying the fan system speed at lower vehicle speeds may be programmed into the controller's memory as ΔCurrent_command. An expected change in the current drawn by the fan system may be based not only on the commanded fan speed state but also on the system voltage. The system voltage may change at different fan speed states, so the voltage before and after the commanded change in the fan speed state can be measured to correctly estimate the expected current before and after changing the fan speed state.Lookup tables can store the fan current change expected at each fan speed state as a function of system voltage.

[0044] At 418, ΔCurrent_actual is compared with ΔCurrent_desired, and a relative error may be determined. At 420, the routine may confirm whether the absolute error is greater than a maximum allowable error threshold. If it is determined that the absolute error is not greater than the allowable threshold, the routine may determine at 424 that no degradation exists in the fan system and return to startup. However, if it is determined that the absolute error is greater than the allowable threshold, the routine increments a degradation counter by one at 422 and proceeds to 426, where it may confirm whether the number of detected degradations is greater than a threshold. F If the number is lower than threshold F, the routine returns to the start and can run the diagnosis again if the preconditions are met. If it is determined that the number of detected functional impairments is greater than the threshold F , the routine indicates a fan degradation at 428 and may illuminate a malfunction indicator lamp (MIL) on the instrument panel and / or set a diagnostic code flag in memory indicating the type of degradation detected. Therefore, a fan degradation is only indicated after multiple indicators have been identified.

[0045] It should be understood that the above example routine illustrates a diagnostic that is being completed; however, in other examples, the routine may be interrupted and terminated when changes in other electrical loads occur. For example, if a change in fan speed was initiated above at 414 and the current draw is measured, an additional load may be applied to the battery-alternator system, affecting the fan diagnostic routine when the driver turns on the rear window defogger. The diagnostic may be disabled due to the expected change in current draw due to the rear window defogger, a counter may not be incremented, and any current draw measurement prior to this interruption may be discarded.Furthermore, the diagnostics may not indicate a degradation of the fan system even if changes in the current drawn from the battery when other electrical loads are in operation deviate significantly from the expected current draw.

[0046] In another embodiment, by characterizing the current draw expected during changes in fan speed as a function of both system voltage and vehicle speed, the precondition that the vehicle speed must be below a threshold may be eliminated.

[0047] In another embodiment, a cooling fan system in an electric vehicle that includes an engine-driven powertrain and a DC-DC converter (instead of an alternator) for charging the vehicle's battery may be diagnosed in a similar manner.

[0048] An exemplary operation of an input condition-based fan diagnostic according to the present disclosure is described in Fig. 5. The Fig. Plot 502 represents the fan diagnosis, plot 504 represents the absolute relative error in current draw, plot 506 represents the expected current draw from the battery-alternator system, plot 508 represents the measured current draw, plot 510 represents the fan speed, plot 512 represents the air conditioning operation, and plot 514 represents the vehicle speed. In addition, line 503 represents the allowable absolute error threshold for changes in current draw, and line 513 corresponds to the vehicle speed threshold.

[0049] Before t1, the vehicle speed is above threshold 513, and sufficient airflow is available to cool the engine. Furthermore, as previously explained, the controller is programmed with expected current draws at lower vehicle speeds and can wait to execute the fan diagnostics until the vehicle speed drops below threshold 513. Therefore, if the vehicle speed decreases at t1 and remains below threshold 513 and no large electrical loads, such as the air conditioning system, are drawing power from the electrical system, the fan diagnostics can be activated by switching the fan from an "off" position to a "low" speed position. The current draw measured between t1 and t2 corresponds to the expected current draw, and no degradation is signaled.At t2, the air conditioning system is activated, possibly by the driver, and the fan speed is increased to medium, placing additional load on the system until t3. In addition to the change in fan speed, the electromagnetic compressor clutch may also increase the load on the battery-alternator system. Diagnostics are therefore interrupted and terminated at t2. All data collected before t2 is discarded, and the controller waits until the preconditions are met again, which does not occur until t4.

[0050] Between t3 and t4, the air conditioning system is shut down and the current draw stabilizes, while the vehicle speed remains below the threshold. Therefore, at t4, it is determined that the diagnostic preconditions are met. At t4, the fan speed is increased to a "low" position, and once the fan speed stabilizes, several current draw readings are obtained. The current draw measured at plot 508 between t4 and t5 corresponds to an expected current draw (plot 506), and since the absolute error is below threshold 503, no degradation flag is set.

[0051] At t5, the vehicle speed exceeds the threshold, and the diagnostics terminate. At t6, the diagnostics can be reactivated because the preconditions are met, and the fan speed is increased from "off" to the "low" position, followed by an increase to the "medium" speed position at t7 and then to a "high" speed position at t8. Because the diagnostic preconditions are still met, the fan speed is decreased from the "high" position to "medium" at t9, and at t10 the fan speed is decreased to "low." At each speed change, multiple readings of the change in current draw are taken and compared to the expected current draw.Plot 508, which shows the measured current consumption, is higher between t7 and t10 than the expected current consumption shown in plot 506, indicating an absolute relative error above the allowable threshold 503 and a subsequent degradation indication between t7 and t10 (plot 502).

[0052] It should be noted that plots 502 and 504 begin a short time after the start of the diagnosis and the fan speed changes at t1, t4, t6, t7, t8, t9, t10 to indicate that the diagnosis must allow a transition time before calculating a fault or analyzing the fault.

[0053] Although the illustrated example includes additional electrical loads in the form of an air conditioning system, it should be understood that other electrical loads may include the rear window defogger, headlights, etc. Furthermore, the system voltage may be maintained within a predetermined range to enable the implementation of fan diagnostics.

[0054] In this way, cooling fan diagnostics can be performed during a vehicle's normal operating conditions. By ensuring that other major electrical loads are stable and unchanging during the diagnostics, changes in the current drawn from the battery-alternator system can be attributed to the cooling fan system. Fan degradation due to degradation in relay circuits can be diagnosed by comparing the measured change in current with an expected change when varying the fan speeds. In addition, relay-controlled cooling fan systems can be tested for degradation using existing hardware without additional sensors, resulting in cost savings.

[0055] In another example, a method is provided for a relay-controlled multi-speed cooling fan system of a vehicle. The method includes delaying requests to change accessory current draw while commanding a modification in cooling fan speed by actuating a fan relay, and correlating a change in current drawn from a battery with a degradation of the cooling fan system based on which fan relay was activated. The request to change accessory current draw (for example, a request to increase or decrease a compressor speed) may be delayed until after the fan relays have been actuated and the change in current has been identified. In this way, the degradation may be better detected and indicated without interference from the changing accessory current drawn.

[0056] It should be noted that the example control and estimation routines included herein are usable with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory. The specific routines described herein may include one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Therefore, various illustrated acts, operations, and / or functions may be performed in the illustrated sequence, performed in parallel, or in some cases, omitted. Accordingly, the processing order is not required to achieve the features and advantages of the embodiments described herein, but is provided merely for convenience of illustration and description.One or more of the depicted processes, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the depicted processes, operations, and / or functions may graphically represent code to be programmed into non-volatile memory of the computer-readable storage medium in the engine control system.

[0057] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technology may be applied to various cooling system configurations. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and / or characteristics disclosed herein.

[0058] The following claims particularly point out certain combinations and sub-combinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be understood as including the inclusion of one or more of these elements, neither requiring nor excluding two or more of these elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether their scope is broader, narrower, the same, or different with respect to the original claims, are also considered to be included within the subject matter of the present disclosure. LIST OF REFERENCE SYMBOLS 10 internal combustion engine 12 Engine control 14 Tax system 16 sensors 18 actuators 23 Security 25 Fuse 27 Security 31 relays 33 relays 35 relays 36 Front End Accessory Drive (FEAD) 37 relays 38 Thermostatic valve 39 relays 44 Inlet channel 48 exhaust channel 51 Resistance 53 Resistance 55 heating heat exchangers 72 alternator 74 System battery 76 electromagnetic clutch 80 coolers 82 coolant lines 83 Liquid container with dryer insert 84 coolant line 85 evaporators 86 engine-driven water pump 87 compressors 88 Condenser 89 Expansion valve 91 Radiator fan 92 fans 93 engine 94 engine 95 Radiator fan 97 engine 100 vehicle cooling system 102 Motor vehicle / vehicle 103 Engine compartment 104 Passenger compartment 106 drive wheels 112 Radiator grille

Claims

[1] A method for a relay-controlled multi-speed cooling fan system coupled to an engine (10), comprising: if other electrical loads are stable: Measuring a current when a fan speed changes; and Indicate fan system degradation based on a relative change in current. [2] The method of claim 1, wherein the measured current is taken from a battery-alternator system, the method further comprising terminating the measurement if the other electrical loads change by more than a threshold value. [3] The method of claim 2, further comprising: Calculating an error between a measured change in current and an expected change in current drawn from the battery-alternator system, the expected current drawn being based on which of a plurality of relays (31, 33, 35, 37, 39) is activated. [4] The method of claim 3, wherein the indication of the degradation is based on the calculated error. [5] The method of claim 1, wherein the current is only measured when the other electrical loads are stable and a vehicle speed is below a threshold. [6] The method of claim 1, further comprising: Disable fan current sensing when changes in other electrical loads are expected due to driver inputs. [7] The method of claim 1, wherein the fan speed is adjusted by adjusting an actuation of a plurality of relays (31, 33, 35, 37, 39). [8] A method for a relay-controlled multi-speed cooling fan system of a vehicle (102), comprising: if all electrical loads remain unchanged: Commanding a modification in a fan speed by actuating one or more fan relays (31, 33, 35, 37, 39); and Correlating a change in current drawn from a battery-alternator system with a degradation of the cooling fan system based on which fan relay (31, 33, 35, 37, 39) was actuated. [9] A method according to claim 8, wherein the change in the current consumed is compared with an expected change, the method further comprising indicating the degradation. [10] The method of claim 8, wherein the electrical loads include an air conditioning compressor (87), a vehicle entertainment system, and a rear window defogger. [11] The method of claim 10, wherein the modification is commanded only when a vehicle speed is below a threshold. [12] The method of claim 10, wherein the modification is commanded only when a charging system voltage is greater than a minimum threshold but less than a maximum voltage threshold. [13] A system for a vehicle (102), comprising: a plurality of cooling fans (91, 95) coupled to a prime mover (10); and a controller with computer-readable instructions stored in non-volatile memory to: if the vehicle (102) moves slower than a threshold value: during a first state when other electrical loads are kept constant; change one or more cooling fan speeds and indicate a degradation of the cooling fan system based on a change in current drawn from a battery-alternator system; and during a second condition when other electrical loads vary; to disable a cooling fan diagnostic. [14] The system of claim 13, wherein disabling the cooling fan diagnostics comprises not indicating a degradation of the fan system even if, when changing the fan speed, a change in current during the varying electrical loads deviates from an expected change in current by more than a threshold. [15] The system of claim 14, wherein an engine cooling fan motor (93, 97) coupled to one of the cooling fans (91, 95) is relay controlled. [16] The system of claim 12, further comprising, during the first state, comparing differences in current drawn from a battery-alternator system as the fan speed varies with an expected change in current draw. [17] The system of claim 16, further comprising estimating an error based on the relative change between the measured current draw and the expected current draw. [18] The system of claim 17, further comprising comparing the absolute relative change with an allowable threshold. [19] The system of claim 18, wherein degradation of the cooling fan system is indicated when the absolute error is above a threshold.

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