Method for controlling the blower speed of an air conditioning blower for vehicles with a start-stop engine

Abstract

Method for controlling a blower speed of a blower (17) of an air conditioning system in a vehicle (10) with an automatic start-stop combustion engine (11), comprising the following: The occurrence of an automatic engine stop event in which the start-stop combustion engine (11) is automatically stopped; Measuring an outside ambient temperature and a second temperature of the air conditioning system; Determining a first reduction limit (43) in response to the outside ambient temperature and determining a second reduction limit (45) which is lower than the first reduction limit (43) ; Ramping of the fan speed to the first reduction limit (43) and Ramping of the fan speed to the second reduction limit (45) and Restarting the start-stop combustion engine (11) and restoring the blower speed to the speed that the blower (17) had before the engine stop event, in response to the second temperature reaching a restart threshold (47).

Description

[0001] The present invention relates generally to an automatic control of an HVAC blower speed during the shutdown of a start-stop engine in a motor vehicle.

[0002] Fuel economy in motor vehicles is a key attribute of vehicle performance and is determined by the technologies used in vehicle design, the driver's behavior and actions, and the conditions under which the vehicle is used (for example, speed, road design, weather, and traffic). Manufacturers are constantly striving to deliver better fuel economy. One technology that is becoming increasingly common is automatic start-stop technology, in which the combustion engine automatically shuts off when the vehicle comes to a stop or coasts and then restarts as needed to continue driving. Reducing the time the engine spends idling (for example, while waiting at a traffic light) results in improved fuel economy and reduced emissions.According to some estimates, start-stop technology can offer an improvement in fuel economy of 5% to 10% or more.

[0003] In addition to powering the vehicle, the internal combustion engine drives other vehicle systems, such as an air conditioning compressor. Passenger comfort must be maintained while the engine is off. Since the air conditioning compressor is typically driven by an engine-driven front-end accessory drive (FEAD) belt, the conventional compressor does not run when the engine is off. If the air conditioning is actively used and the engine is stopped under idling conditions, the cooling effect is interrupted, and the vehicle interior may become warmer. If the interior temperature increases by a certain amount, the engine is usually restarted, resuming cooling, but some of the fuel economy improvement may be lost. An example of a strategy for controlling the time the engine is off is presented in the document dated 30.The information is provided in the form of the company's own pending US application filed in July 2012, Ifd. No. 13 / 561,328, entitled "Engine Start-Stop Control Strategy for Optimization of Cabin Comfort and Fuel Economy", to which reference is hereby made in its entirety.

[0004] German patent application DE 699 35 833 T2 is known from the prior art. This describes a method for controlling the blower speed of an air conditioning system in a vehicle with an engine, comprising the following: occurrence of an automatic engine stop event, in which the engine is automatically stopped; measuring an outside ambient temperature and a second temperature of the air conditioning system; determining a first reduction limit in response to the outside ambient temperature; ramping the blower speed to the first reduction limit; restarting the engine; and restoring the blower speed in response to the second temperature reaching a restart threshold.

[0005] US 2008 / 0103635A1 describes a method for controlling the fan speed of an air conditioning system in a single-engine vehicle, which includes: the occurrence of an automatic engine stop event, at which the engine is automatically stopped; measuring an outside ambient temperature and a second air conditioning system temperature; determining a first reduction limit, ramping the fan speed to the first reduction limit, restarting the engine, and restoring the fan speed in response to the second temperature reaching a restart threshold.

[0006] US Patent 2009 / 0145141A1 describes a method for controlling an air conditioning system in a vehicle with an engine, which includes: the occurrence of an automatic engine stop event, in which the engine is automatically stopped; measuring an outside ambient temperature and a second temperature of the air conditioning system; determining a first reduction limit in response to the outside ambient temperature, ramping to the first reduction limit, and restarting the engine.

[0007] US 2013 / 0317728A1 describes a method for controlling an air conditioning system in a vehicle with an engine, which includes: the occurrence of an automatic engine stop event, in which the engine is automatically stopped; measuring an outside ambient temperature and a second temperature of the air conditioning system; restarting the engine.

[0008] In an attempt to extend the time before the air conditioning system needs to be restarted, the use of cold storage systems has been considered. In one type of cold storage system, an evaporator may contain a phase-transition material that, during normal operation, releases heat before a shutdown event (for example, freezes) and then absorbs heat by transitioning back to a liquid phase during the shutdown event. However, cold storage devices are expensive, difficult to install due to their larger size, and require additional controls. Furthermore, because they consume additional energy when the engine is running, the improvement in fuel economy is diminished.

[0009] Another approach to providing air conditioning when the combustion engine is off involves using an electric compressor powered by stored electrical energy from a battery. However, for a typical gasoline-powered vehicle, the cost of such an additional air conditioning system is usually prohibitive. Even in a hybrid vehicle (i.e., with a combustion engine connected to an electric drive system), the additional use of the electric compressor would result in a loss of fuel economy. Therefore, it would be desirable to maintain passenger comfort during extended engine shutdowns without relying on cold storage or standby cooling systems.

[0010] Methods with the features of the independent claims are provided. According to the invention, a method for controlling the blower speed of an air conditioning system in a vehicle with a start-stop engine is provided. A stop event is initiated, and an ambient temperature and a second air conditioning system temperature are measured. A first reduction limit is determined in response to the ambient temperature, and a second reduction limit, lower than the first, is determined. The blower speed is ramped down to the first reduction limit. Then, the blower speed is ramped down to the second reduction limit. In response to the temperature reaching a restart threshold, the engine is restarted, and the blower speed is restored to the speed it had before the engine stop event. Fig. Figure 1 is a block diagram showing a vehicle configured to use various embodiments of the present invention. Fig. Figure 2 is a diagram showing a modified fan speed during an auto-stop event for a first embodiment of the invention. Fig. Figure 3 shows a reference table for determining a reduced speed. Fig. 4 is a flowchart of a procedure according to Fig. 2. Fig. Figure 5 is a diagram showing modifications of the blower speed according to another embodiment of the present invention. Fig. 6 is a flowchart of a procedure according to Fig. 5. Fig. Figure 7 is a diagram showing modifications to the blower speed according to yet another embodiment of the invention. Fig. 8 is a flowchart of a procedure for providing the in Fig. 7 fan speed modifications shown.

[0011] Now on Fig. 1. Referring to the above, a vehicle 10 contains an internal combustion engine (start-stop engine) 11 equipped with start-stop features, whereby the engine can be automatically switched off during periods when it would otherwise be idling (for example, when the vehicle is not moving) and then automatically restarted as needed when the vehicle starts moving again or when it is necessary to operate auxiliary equipment (such as the air conditioning compressor) via the engine. An engine control unit 12 is connected to the engine 11 to perform the start-stop functions. The engine 11 drives a compressor 13, which, together with the engine 11 and the engine control unit 12, is housed in an engine compartment 14. The vehicle 10 contains a vehicle interior 15, which includes an evaporator 16 and a blower 17 of an automotive HVAC system.The blower 17 contains a speed-controlled electric motor with a fan wheel that generates a target airflow. A controller 20 is connected to the blower 17 for controlling a specific blower speed and to the compressor 13 (for example, for controlling a target stroke of a variable displacement compressor). The controller 20 is connected to several sensors and receives other input signals to coordinate the operation of the HVAC system (for example, determining a blower speed or a suitable value for the compressor stroke). A vehicle speed sensor 21 provides an instantaneous speed signal to the controller 20 and the engine control unit 12. An outside temperature sensor 22 (which may be located in the engine compartment 14) generates an outside temperature signal based on the temperature outside the vehicle and couples the resulting signal to the controller 20.Similarly, an internal comfort sensor 23 generates one or more signals that identify comfort parameters, such as an internal temperature signal and / or an internal humidity signal, and transmits the signal(s) to the controller 20. An evaporator temperature sensor 24, which is assigned to the evaporator 16, generates an evaporator temperature signal according to the actual temperature in the evaporator and transmits this to the controller 20.

[0012] An occupant control element or control head 25 is used by the driver or another vehicle occupant to set a desired temperature and / or fan speed for cooling the vehicle interior 15. The control element 25 generates an occupant request signal, which is sent to the controller 20 in the conventional manner. A solar load sensor 28, such as a light intensity sensor, provides a solar load signal to the controller 20. The controller 20 contains a lookup table 29. Based on the various inputs to the controller 20, it automatically controls the fan speed during a stop event according to the inputs that can be used to determine speed values ​​using the lookup table 29.

[0013] Under certain conditions, for example, when the vehicle slows to a standstill, the engine control unit 12 initiates an automatic stop event. Such an event can be partially detected as a reaction to the occurrence of deceleration. In one embodiment, the deceleration is detected by monitoring the position of a brake pedal 26 using an angle / position sensor 27, which supplies the control unit 20 with an angle signal representing the instantaneous brake pedal angle.

[0014] The decision to initiate a stop event can depend on whether the HVAC system is switched on and whether it has managed to approach the desired temperature setting. For example, if the air conditioning is switched on, but the temperature is more than a predetermined number of degrees above the desired setting because the HVAC system has only been running for a short time, then no automatic engine stop event will be initiated, even though the vehicle has come to a standstill. The control unit 20 can be coupled to the engine control unit 12 via a multiplex bus (not shown) to provide the necessary information for making a decision. If the HVAC system is in or near-steady-state operation, then the initiation of an automatic stop event would not be prevented.

[0015] After an automatic stop event is initiated with the HVAC system in air conditioning mode, the compressor 13 is no longer driven by the engine. Consequently, the evaporator 16 no longer receives cold refrigerant. Nevertheless, the evaporator 16 is sufficiently colder than the air in the vehicle interior, so it is advantageous to continue circulating the air from the blower and retain any remaining cooling potential. Eventually, however, the evaporator temperature rises to a point where it no longer cools the interior. The rising temperature leads to discomfort for the occupants. Furthermore, increased interior humidity and a musty odor may occur. Therefore, the evaporator temperature is monitored so that the engine can be restarted before the evaporator temperature becomes too high.

[0016] To reduce energy consumption during a stop event and to prevent the evaporator from heating up too quickly, the invention automatically uses a slower (i.e., reduced) speed for operating the blower during the stop event, as shown in Fig. 2 shown. Instead of always switching to a specific fixed speed value, the present invention detects climatic conditions and determines a suitable reduced speed that preserves passenger comfort while optimizing the engine stop time.

[0017] Line 30 shows an example of the fan speed profile between an initial fan speed and a reduced speed. The evaporator temperature is shown along line 31. The HVAC system maintains the evaporator temperature close to a set value during steady-state operation providing air conditioning cooling to the indoor air. [The text abruptly ends here, so the translation stops as well.] Fig. At the time shown in Figure 2, an engine stop event occurs, causing the air conditioning compressor to cease operation and the evaporator temperature to gradually begin to rise. In response to the auto-stop event, the fan speed is ramped down along a segment 32 to a reduced speed 33. Depending on the climatic conditions, the value selected for the reduced speed at 33a may be zero (fan off) or a relatively low speed at 33b. The reduced speed 33 is sufficient to maintain occupant comfort for a reasonable period while avoiding the rapid heating of the evaporator that would result from a faster fan speed. As the stop event continues, the evaporator temperature rises until it reaches a restart threshold (restart). schwell) 34 is reached, at which point a motor start event 35 occurs, so that compressor operation is restored and the evaporator temperature can begin to decrease, as shown in 36. When the motor restarts, the blower speed is returned to its original level via ramps at 37.

[0018] A suitable value for the reduced speed can be determined using reference table 29, as in Fig. Figure 3 shows the selection. Climatic conditions that determine how far the fan speed can be reduced without noticeably warming the occupants include the ambient temperature and solar heat gain. Higher ambient temperatures and stronger solar heat gain each contribute to faster warming of the vehicle interior. Calibrated values ​​for the reduced speed are stored in lookup table 29. During operation, the controller enters the measured ambient temperature and solar heat gain values ​​into table 29, resulting in an optimal reduced speed value.

[0019] A preferred method of the invention is described in Fig. Figure 4 shows that an auto-stop event occurs in step 90. Based on the ambient temperature and / or solar load, the HVAC control suggests a reduced speed in step 91 and begins ramping down the fan speed to this reduced speed. The ramp rate can be relatively slow so as not to disturb the occupants and to largely maintain airflow during a very brief stop event. In step 92, a check is performed to determine if the engine has restarted. If so, the original fan speed is restored in step 93. Otherwise, a check is performed in step 94 to determine if an air conditioning temperature (preferably the evaporator temperature T) has been reached. Verd ) to a restart threshold (restart schwell) has increased. If this is the case, a motor restart request is sent to the motor control in step 95, and the blower speed is restored in step 93.

[0020] If T Verd If the temperature is still cold enough, then in step 96 a check is performed to determine whether the reduced speed has been reached. If not, the ramping continues, and the procedure rechecks the conditions in steps 92 and 94. If the reduced speed has been reached, then in step 97 the ramping is stopped, or the reduced speed is maintained.

[0021] In Fig. Figure 5 shows the operation of an alternative embodiment of the invention with a graduated reduction of the fan speed, wherein graph 40 represents the fan speed and graph 41 represents the evaporator temperature. The fan speed is initially operated at an arbitrary speed (up to a maximum), which can be manually set by the driver or automatically controlled by the HVAC system. If the fan speed exceeds a first reduction limit 43 (Reduction 1), then, upon the occurrence of an engine stop event, the fan speed is ramped down along a segment 42 to the first reduction limit (Reduction 1). The speed is ramped down at a first ramp rate selected so that the change does not disturb the occupants.The first reduction limit (Reduction1) can be either 1) a predetermined fixed speed or 2) selected based on the ambient temperature and / or solar load. The fixed or selected speed is designed to prioritize occupant comfort over extended stop times, so that the cooling airflow is only moderately altered during short stop events.

[0022] With the engine off, the evaporator temperature gradually increases until it reaches an evaporator temperature threshold (evaporation). Schwell) 44 is reached. The controller detects the increase in evaporator temperature and consequently ramps down the fan speed to an even lower second reduction limit 45 (reduction2) at a second ramp limit along a segment 46. The second ramp rate can be the same as the first ramp rate, but it is preferably slower than the first ramp rate because the vehicle has likely stopped moving, thus requiring a more gradual change to avoid disturbances.

[0023] The second reduction limit (Reduction2) can, for example, correspond to a fan speed of zero or a very low fan speed. The present invention reduces the fan speed in stages to best preserve passenger comfort during shorter stops, while extending the evaporator heating time during longer stops. By maintaining the use of a more moderate reduction limit during a short initial period, an increased airflow during shorter stops, during which the evaporator temperature would not have sufficient time to reach the restart threshold (restart), is avoided. schwell ) (47) to reach, maintain. When the evaporator temperature reaches the evaporator threshold (evaporation) SchwellOnce the temperature reaches 44°C, a slower increase in evaporator temperature will be achieved by further reducing the fan speed. When the evaporator temperature finally reaches the restart threshold (restart) schwell ) 47 is reached, then the fan speed is ramped up again at segment 48.

[0024] Fig. 6 is a flowchart of a process that corresponds to the embodiment of Fig. 5 corresponds to this. In step 50, the engine control enters an auto-stop event. The first reduction limit (Reduction1) is applied to the fan speed in step 51 using the first ramp rate. In step 52, a check is performed to determine whether the ambient temperature is between a low-temperature threshold and a high-temperature threshold. The high-temperature threshold may indicate a hot external condition in which the occupants would quickly become uncomfortable without continuous operation of the air conditioning system. The low-temperature threshold can be useful in determining whether the HVAC system is primarily providing heating for the vehicle interior (i.e., is not in air conditioning mode). In one embodiment, the high-temperature threshold may be approximately 28°C, and the low-temperature threshold may be approximately 10°C.Preferably, the temperature range encompasses a comfortable room temperature of approximately 22°C. If the ambient temperature is outside this comfortable range, no further reduction in fan speed is initiated. Instead, a check is performed in step 53 to determine whether the evaporator temperature exceeds the restart threshold. If it does, the motor restarts, and the original fan speed is restored in step 54.

[0025] If, in step 52, the ambient temperature is found to be within the comfortable ambient temperature range, the fan speed is maintained at the first reduction limit (Reduction1), while in step 55, it is regularly checked whether the evaporator temperature has risen above the evaporator threshold. Once the evaporator threshold is reached, the fan speed is ramped down in step 56 to a second reduction limit (Reduction2) with the second ramp rate. The value of the second reduction limit (Reduction2) can be a fixed value (for example, zero or a very slow speed, or it can be determined based on climatic conditions). From then on, the evaporator temperature is compared to the restart threshold in step 53.

[0026] Fig. Figure 7 shows a third embodiment in which a plot 60 representing the fan speed can assume several different reduction limits. Upon the occurrence of the stop event, the fan speed at 61 can thus be reduced to the first reduction limit (Reduction 1). When the evaporator temperature reaches the evaporator threshold, the fan speed at 62 is reduced either to the second reduction limit (Reduction 2) or a third reduction limit (Reduction 3), shown at 63 and 64, respectively. Although it is particularly preferred to assume a reduction limit that is as low as possible (for example, zero at the third reduction limit (Reduction 3)), there may be climatic conditions under which even a very low degree of air circulation could be beneficial for occupant comfort.Thus, the subsequent reduction limit can be determined based on the detection of an occupant comfort parameter, such as interior humidity, interior temperature, ambient temperature, solar load, or any combination thereof. For example, if the interior humidity exceeds a predetermined threshold, a second, non-zero reduction limit (Reduction2) can be selected. The selected reduction limit can remain in effect until a restart event, at which point the fan speed is ramped up to the speed it had before the stop event. A ramp rate can be used with the slower ramp rate up to the first reduction limit, as shown in Figures 65 and 66, and then continuing with the higher ramp rate, as shown in Figures 67 and 68. Alternatively, a faster ramp rate can be used for the entire ramp-up time.Alternatively, changes in the occupant comfort parameter could be detected, leading to switching between reduction limits, as shown at 70.

[0027] In Fig.Figure 8 shows an alternative procedure with the graduated selection of reduction limits. In step 75, an auto-stop event is initiated, and the first reduction limit (reduction-1) is applied in step 76. In step 77, a check can optionally be performed to determine whether the air conditioner is in AC mode. If not, the first reduction limit (reduction-1) continues to be used, while in step 78 a check is performed to determine whether the evaporator temperature has reached the restart threshold. If the evaporator temperature rises above the restart threshold, then in step 79 an auto-stop event is terminated (that is, the motor is restarted and the fan speed is restored to its previous value).

[0028] In AC mode, a check is performed in step 80 to determine whether the ambient temperature is below the upper temperature threshold. If not, the first reduction limit (Reduction1) continues to be applied, while the evaporator temperature is compared to the restart threshold in step 78. Otherwise, a check is performed in step 81 to determine whether the solar load is greater than a solar load limit threshold (Son). Grenze Excessive solar heat gain indicates that occupant comfort can only be maintained by further applying the reduced-1 fan speed limit. In step 78, the procedure further checks the evaporator temperature against the restart threshold.

[0029] If the solar load is not excessive, the evaporator temperature is compared to the evaporator threshold in step 82. If the evaporator temperature reaches the evaporator threshold, one or more comfort parameters are detected in step 83, allowing a reduction limit to be selected in step 84 and the fan speed to be ramped down to the selected reduction limit. Using this lower reduction limit, the process returns to step 78 to monitor for the need for a restart.

[0030] In embodiments that use multiple reduction limits, one of the potential values ​​is preferably zero, while another value may preferably be equal to the lowest operating speed at which the blower can be sustained. Depending on the climatic conditions, the time until the evaporator temperature has risen to the restart threshold can thus be significantly extended, thereby increasing fuel economy.

Claims

[1] Method for controlling a blower speed of a blower (17) of an air conditioning system in a vehicle (10) with an automatic start-stop combustion engine (11), comprising the following: The occurrence of an automatic engine stop event in which the start-stop combustion engine (11) is automatically stopped; Measuring an outside ambient temperature and a second temperature of the air conditioning system; Determining a first reduction limit (43) in response to the outside ambient temperature and determining a second reduction limit (45) which is lower than the first reduction limit (43) ; Ramping of the fan speed to the first reduction limit (43) and Ramping of the fan speed to the second reduction limit (45) and Restarting the start-stop combustion engine (11) and restoring the blower speed to the speed that the blower (17) had before the engine stop event, in response to the second temperature reaching a restart threshold (47). [2] The method of claim 1, further comprising the following steps: after ramping the fan speed to the first reduction limit (43) comparing the second temperature with a second threshold (44); If the second temperature is above the second threshold (44), then further reduce the fan speed to the second reduction limit (45). [3] Method according to claim 2, wherein the air conditioning system includes an evaporator (16) and wherein the second temperature is connected to the evaporator (16). [4] Method according to claim 2, wherein the second reduction limit (45) consists of a fixed blower speed. [5] Method according to claim 4, wherein the specified blower speed is zero. [6] The method of claim 2, further comprising the step of determining the second reduction limit (45) in response to the outside ambient temperature. [7] The method of claim 2, further comprising the following steps: Measuring solar load and Determining the second reduction limit (45) in response to the solar load. [8] The method of claim 2, further comprising the following steps: Measuring an occupant comfort parameter and Determining the second reduction limit (45) in response to the occupant comfort parameter. [9] Method according to claim 1, further comprising the step of measuring a solar load, wherein the first reduction limit (43) is further determined in response to the solar load. [10] The method of claim 1, further comprising the following steps: after ramping the fan speed to the first reduction limit (43) comparing the second temperature with a second threshold (44); Measuring solar load; If the second temperature is above the second threshold (44) and the solar load is below a solar load threshold, then further reduce the fan speed to the second reduction limit (45). [11] Method for controlling a blower speed of a blower (17) of an air conditioning system in a vehicle (10) with an automatic start-stop combustion engine (11), comprising the following: The occurrence of an engine stop event in which the start-stop combustion engine (11) is automatically stopped; Ramping of the fan speed to a first reduction limit (43); Measuring an outside ambient temperature and a second temperature of the air conditioning system; Comparing the second temperature with a threshold value (44); if the second temperature rises above the threshold (44), then further reduce the fan speed to a second reduction limit (45) and Restarting the start-stop combustion engine (11) and restoring the blower speed to the speed that the blower (17) had before the engine stop event, in response to the second temperature reaching a restart threshold of 47. [12] Method according to claim 11, wherein the first reduction limit (43) consists of a predetermined fixed blower speed. [13] Method according to claim 11, wherein the step of further reducing the blower speed to a second reduction limit (45) comprises: Detecting an occupant comfort parameter and Selecting one value from several values ​​for the second reduction limit (45) of the blower speed in response to the occupant comfort parameter. [14] Method according to claim 13, wherein the occupant comfort parameter comprises a measured humidity and wherein one of the multiple values ​​is zero. [15] Method according to claim 13, wherein the occupant comfort parameter comprises a measured humidity and wherein one of the several values ​​is a lowest operating speed of the blower.

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