MILIATORING TRANSIENT CURRENT EFFECTS IN A VEHICLE WITH ENGINE AUTO START / STOP

Abstract

Vehicle, including: A control system programmed to prevent a power machine autostart in response to the activation of an electrical consumer until a predetermined duration has elapsed, as long as the difference between a post-activation battery current exceeding a predetermined autostart threshold for a portion of the duration and a pre-activation battery current is less than a predetermined difference, and to request the power machine autostart in response to the post-activation battery current exceeding the predetermined autostart threshold after the duration.

Description

TECHNICAL FIELD

[0001] This application generally relates to controlling an engine autostart / autostop in vehicles. BACKGROUND

[0002] A micro-hybrid vehicle can automatically stop its internal combustion engine for a period of time when certain conditions are met. Automatic engine stops can improve fuel economy by reducing the amount of time the engine idles while the vehicle is stationary or coasting to a stop.

[0003] US 2010 / 0 318 283 A1 discloses a vehicle with a control system that is programmed to prevent an engine autostart until a predetermined period of time has elapsed, in response to activation of an electrical consumer.

[0004] According to the invention, a vehicle according to claim 1, a vehicle according to claim 6, and a method according to claim 11 are proposed. Advantageous embodiments of the invention are specified in the dependent claims and the description. SUMMARY

[0005] In some embodiments, a vehicle includes a controller programmed to, in response to activation of an electrical load, prevent engine auto-start until a predetermined duration has elapsed as long as a difference between a post-activation battery current exceeding a predetermined auto-start threshold for a portion of the duration and a pre-activation battery current is less than a predetermined difference, and to request engine auto-start in response to the post-activation battery current exceeding the predetermined auto-start threshold after the duration.

[0006] Some embodiments may include one or more of the following features: The vehicle in which the pre-activation battery current is less than the predetermined auto-start threshold. The vehicle in which the predetermined duration is longer than an expected duration of a peak current caused by activation of the electrical load. The vehicle in which the predetermined difference is based on a maximum expected inrush current of the post-activation battery current. The vehicle in which the pre-activation battery current is a time-averaged current during a predetermined duration prior to activation of the electrical load. The vehicle in which the controller is further programmed to request an engine auto-start in response to the difference exceeding the predetermined difference during the duration.

[0007] In some embodiments, a vehicle includes an engine. The vehicle also includes an electrical load. The vehicle also includes a controller programmed to request an engine auto-start when a battery current exceeds a predetermined current, and in response to the battery current exceeding the predetermined current within a predetermined duration beginning with detection of a transition of the electrical load to an activated state, to prevent an auto-start of the engine until the predetermined duration elapses, as long as a difference between a battery current magnitude before and after the detection is less than a predetermined difference.

[0008] Some embodiments may include one or more of the following features. The vehicle in which the predetermined duration is longer than an expected duration of a peak current caused by the transient. The vehicle in which the controller is further programmed to request an auto-start of the engine in response to the difference exceeding the predetermined difference during the predetermined duration. The vehicle in which the predetermined duration is a period of time in which an inrush current caused by activation of an electrical load is expected to decay to a steady-state current. The vehicle in which the magnitude of the battery current prior to the detection is a time-averaged battery current over a predetermined period of time prior to the transient. The vehicle in which the magnitude of the battery current prior to the detection is less than the predetermined current.

[0009] In some embodiments, a control-based method includes, in response to activation of an electrical load, preventing an engine auto-start until a predetermined duration has elapsed, as long as a difference between a post-activation battery current exceeding a predetermined threshold for a portion of the duration and a pre-activation battery current is less than a predetermined difference. The method further includes, in response to the post-activation battery current exceeding the predetermined threshold after the duration has elapsed, requesting an engine auto-start.

[0010] Some embodiments may include one or more of the following features. The method may include requesting, by the controller, an engine auto-start in response to the difference exceeding the predetermined difference during the duration. The method wherein the predetermined duration is a period of time in which an inrush current is expected to decay to a steady-state current after activation of an electrical load. The method may include averaging, by the controller, a battery current over a predetermined period of time prior to activation of an electrical load to generate the pre-activation battery current. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram for a micro hybrid vehicle. Fig. Figure 2 is a graph of engine status versus time before, during, and after an engine stop / start event. Fig. Figure 3 is a possible flowchart for a sequence of operations for handling engine autostarts. DETAILED DESCRIPTION

[0011] Embodiments of the present disclosure are described herein. It should be understood, however, that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. The specific structural and functional details disclosed herein are therefore not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.As one of ordinary skill in the art will understand, various features illustrated and described with reference to any of the figures may be combined with features illustrated in one or more other figures to produce embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of this disclosure may be desirable for particular applications or implementations.

[0012] With reference to Fig. 1, a micro hybrid vehicle 110 may include: a prime mover 112, an electric machine 114, which may be referred to as a generator or integrated starter generator, a battery 116 (e.g., a 12V battery), electrical loads 118 (e.g., climate control system pumps, a power steering assist system, etc.) in communication with / controlled by one or more controllers 120 (as indicated by a dashed line). The prime mover 112 is mechanically connected to the electric machine 114 (as indicated by a thick line) such that the prime mover 112 can drive the electric machine 114 to generate electrical power. The electric machine 114 and the battery 116 are electrically connected to each other and to the electrical loads 118 (as indicated by a thin line) via a utility grid 122.The supply network 122 may be a series of conductors that electrically connect the components. The supply network 122 may include power and ground signals. Therefore, the electric machine 114 may charge the battery 116; the electrical loads 118 may consume electrical power provided by the electric machine 114 and / or the battery 116.

[0013] The controls 120 may initiate an auto-stop or auto-start of the engine 112. For example, when the vehicle 110 stops, the controls 120 may issue a command to begin the process of stopping the engine 112, thus preventing the electric machine 114 from supplying electrical power to the electrical loads 118. The battery 116 may supply electrical power to the electrical loads 118 while the engine 112 is stopped. Following an engine auto-stop, when a brake pedal (not shown) is released (and / or an accelerator pedal (not shown) is applied), the controls 120 may issue a command to begin the process of starting the engine 112, thus allowing the electric machine 114 to supply electrical power to the electrical loads 118.

[0014] The controller 120 may monitor conditions for starting and stopping the engine 112 during an ignition cycle. Conditions may include determining when the engine 112 should be automatically stopped to improve fuel economy. For example, during a braking application, the engine 112 may be automatically stopped. Other conditions may include determining when the engine 112 should be automatically started. For example, when an operator releases the brake pedal, the engine 112 may be automatically started. The controllers 120 may be coupled to the battery 116, the electrical loads 118, the electric machine 114, and the engine 112 via a control network 124. The control network 124 may include discrete hardware connections between modules. The control network 124 may include a communications network in which the modules can communicate serially.In some embodiments, controller 120 may coordinate the operation of multiple controllers to perform an auto-stop and auto-start of engine 112. For example, an engine controller may communicate with controller 120 via the communications network (e.g., Controller Area Network (CAN)).

[0015] With reference to Fig. 2, an engine auto-stop event may include several stages: "auto-stop initiation", which indicates the beginning of the engine auto-stop event; "prepare for engine auto-stop", which indicates the period of time during which vehicle systems as well as the engine are prepared for the impending engine stop (if an auto-stop prevention condition is detected during this stage, preparation for the impending engine stop is interrupted and the vehicle systems and the engine are returned to their normal operating modes); "fuel shutoff", which indicates the point at which fuel flow to the engine is stopped; "engine stop", which indicates the period of time during which engine speed is reduced to 0;"Under-Fuel Restart," which indicates the point after which, if a restart is requested during the "Engine Stop" stage, the starter motor may need to be engaged to crank the engine (if a restart is requested before the "Under-Fuel Restart" and during the "Engine Stop" stage, the engine may be restarted by turning the fuel flow back on); "Engine Speed ​​= 0," which indicates the point at which the engine speed is close to or equal to 0; "Engine Auto-Stopped," which indicates the period of time during which the engine is off; "Starter Engaged," which indicates the point at which the starter motor begins cranking the engine in an effort to start the engine (in response to detecting an engine auto-start condition);“Starter motor cranking,” which indicates the period of time during which the engine is unable to rotate under its own power; “starter motor disengaged,” which indicates the point at which the engine is able to rotate under its own power; “engine speed ramping,” which indicates the period of time during which the engine speed increases to its running speed (a speed at or above a desired idle speed); and “auto start end,” which indicates the point at which the engine speed reaches its running speed.

[0016] With further reference to Fig. 1, the electrical loads 118 may be operational while the engine 112 is off during an engine stop / start event. For example, pumps associated with a climate control system may be on during this period. Therefore, the battery 116 may need to provide power to support these loads. However, the power demands of the electrical loads 118 during an engine stop / start event may exceed the recommended capabilities of the battery 116. That is, the voltage of the battery 116 may drop below a recommended limit while the electrical loads 118 are being supported during an engine stop / start event. To prevent this situation from occurring, the controllers 120 may determine the power demands of the electrical loads 118 and compare them to a predetermined threshold.For example, current values ​​provided by the electric machine 114 and the battery 116 may be added to determine the total current demand of the electrical loads 118. If the total current demand exceeds the predetermined threshold, the controllers 120 may prevent any attempt to automatically stop the engine 112. The predetermined threshold may be determined and selected through testing, simulation, etc., to prevent the voltage of the battery 116 from falling below a desired level.

[0017] The power demand of certain of the electrical loads 118 may depend on whether the engine 112 is on or off. For example, the power demand of an engine cooling fan or fuel pump may drop to 0 while the engine 112 is off during an engine stop / start event. Similarly, the power demand of pumps associated with a climate control system may decrease while the engine 112 is off during an engine stop / start event. However, power demands of other subsystems may increase while the engine 112 is off during an engine stop / start event. Therefore, the net value of the power demands of the electrical loads 118 may either decrease or increase after the engine 112 is automatically stopped.

[0018] The controller 120 may be programmed to implement a variety of strategies for automatically starting and stopping the engine 112. For example, the engine 112 may be automatically stopped during braking events or when the vehicle 110 is in a park mode. Conditions for an auto-start of the engine 112 may include a case where the current drawn from the battery exceeds an auto-start current threshold. Conditions for an auto-stop of the engine 112 may include a case where the current drawn from the battery is less than an auto-stop current threshold. The auto-stop current threshold and the auto-start current threshold may be different to avoid rapid cycling of the engine 112.Such a strategy may successfully handle steady-state currents, but it may not be able to successfully handle transient current conditions. For example, the strategy may automatically start the engine 112 in response to transient current conditions that exceed the autostart current threshold. Because the transient currents may decay quickly, there may be no need to automatically start the engine 112. The result is a system that includes short engine cycles caused by transient current conditions.

[0019] One strategy to avoid these unnecessary stop-start cycles may be to introduce a wait time for automatic starting of the engine 112. The controllers 120 may be programmed to automatically start the engine 112 in response to the battery current being higher than the autostart current threshold for a duration greater than or equal to the wait time. This strategy may cause the engine autostart cycles to be delayed when steady-state power demands exceed the autostart current threshold.

[0020] The vehicle 110 may include a current sensor 130 configured to measure the current flowing to and from the battery 116. The current sensor 130 may provide a signal to the controller 120 indicating the battery current magnitude and direction. The controller 120 may include circuitry to filter the signal and convert the signal into a digital form for processing.

[0021] The electrical load 118 may be coupled to the controller 120 by a control signal or via the control network 124. The controller 120 may be programmed to control the operation of the electrical load 118. Controlling the electrical load 118 may include activating and deactivating the electrical load 118. When the electrical load 118 is in an activated state, it may draw power from the utility grid 122. A magnitude of the current may depend on the length of time after activation. For a period of time immediately following activation, the current may be in a transient phase. The transient phase includes an inrush current, which may be a transient current greater than a steady-state rated current value. Many electrical loads have an inrush current.For example, electric motors and transformers, incandescent lamps and power converters can have high inrush current.

[0022] After the transient phase, the current drawn by the electrical load 118 may be in a steady-state phase. During the steady-state phase, the current level may be at the steady-state rated current value. The steady-state rated current value may be the current value measured when the electrical load 118 remains activated after the transient phase.

[0023] Controller 120 may be programmed to request an autostart and autostop of engine 112 based on battery current. In some embodiments, an autostart cycle may be requested in response to the battery current being greater than a predetermined current threshold.

[0024] In some embodiments, the autostart cycle may be requested in response to the battery current being higher than a predetermined current threshold for a period of time longer than a predetermined duration. Adding the duration condition may help prevent unnecessary autostart cycles, but may delay some autostart cycles.

[0025] When transitioning from a deactivated state to an activated state, the electrical load 118 may draw an inrush current from the supply network 122 that is higher than the specified rated current. The inrush current may have a known duration. Different electrical loads 118 may have different inrush current durations.

[0026] When activating the electrical load 118, the current drawn by the electrical load 118 may be higher than the specified rated current for a period of time. The current may decay to the specified rated current of the electrical load 118 over the course of this period. The short-term effects of activating the electrical load 118 may differ from the steady-state effects of activating the electrical load 118. Due to the transient inrush current, the battery current may reach a higher peak immediately after activation than during the steady-state condition.

[0027] The effect of the transient component of the load current may cause the battery current to exceed the auto-start current threshold. As the transient component subsides, the battery current may then fall below the auto-start current threshold. The effect on the vehicle may be such that the engine 112 is started for a short period of time. This start / stop cycle may be unnecessary because the battery 116 may be able to handle the short-term transient condition.

[0028] To prevent these unnecessary engine start / stop cycles, it may be beneficial to detect when transient currents may be present. Controller 120 may be programmed to monitor an activation status of electrical loads 118 to determine when electrical loads 118 transition from a deactivated state to an activated state. If a transition from a deactivated state to an activated state is detected, controller 120 may modify the autostart transition criteria to prevent the transient current from causing an autostart cycle.

[0029] The activation status of the electrical load 118 may be communicated to the controller 120 via the control network 124. For example, a signal in a serial data message may indicate the on / off status of the electrical load. The controller 120 may receive a signal indicating an activation state of the electrical load 118. A value transition of this signal may indicate when the electrical load 118 has changed activation status. To detect a transition from a deactivated state to an activated state, the controller 120 may monitor this signal for the corresponding value change.

[0030] To improve the reliability of engine auto-start / auto-stop activation and deactivation, controller 120 may be programmed to detect transient current conditions when electrical loads 118 are activated. Knowing that a change in battery current due to transient currents during activation may allow for prevention of auto-start. Controller 120 may be programmed to detect a magnitude of the transient current condition. The magnitude of the transient current may be detected based on a difference between a pre-activation battery current measured before detecting activation of electrical load 118 and a post-activation battery current measured after detecting activation of electrical load 118.

[0031] The pre-activation battery current may be a current measured prior to receipt or detection of any signals indicating a transition of the electrical loads 118 to an activated state. The pre-activation battery current may represent a previous steady-state current value. The pre-activation battery current may be a low-pass filtered current during a period prior to detection of activation. The pre-activation battery current may be a time-averaged value over an interval prior to detection of activation.

[0032] The post-activation current can be a current measurement sampled after activation is detected. The post-activation current can be an instantaneous current value and represents the transient current. The difference between the post-activation battery current and the pre-activation battery current provides an indication of the transient current. The difference can be calculated for multiple time periods after activation to monitor the transient current. Under normal conditions, the transient current can be expected to rise rapidly after activation and decay to a steady-state value for a period of time after activation.

[0033] In some embodiments, upon detecting activation of an electrical load 118 known to have a significant transient current, engine autostarts may be prevented for a predetermined duration if the transient current is less than a predetermined duration. This may prevent the engine 112 from automatically starting due to a brief transient condition. The pre-activation current may be less than the predetermined autostart current threshold. The post-activation battery current may be greater than the predetermined autostart current threshold. In this case, engine autostarts may be prevented to avoid starting due to the transient condition. The predetermined duration for preventing engine autostarts may be based on an expected duration of the transient current condition.For example, tests may show that a transient current subsides within ten seconds of a load activation. After the specified duration, if the post-activation battery current is higher than the specified autostart current threshold, an engine autostart can be requested.

[0034] In some embodiments, an engine auto-start may be requested when the transient current magnitude is higher than the predetermined magnitude. For example, an inrush current magnitude may be much higher than expected. The predetermined magnitude may be based on a maximum expected inrush current magnitude for the electrical load 118. Under such conditions, the engine auto-start may be requested.

[0035] In some embodiments, engine autostarts may be prevented in response to the battery current exceeding the predetermined autostart current threshold within a predetermined duration immediately following detection of a transition of electrical load 118 to an activated state. If the battery current exceeds the predetermined autostart current threshold for a time longer than the predetermined duration, an engine autostart may be requested. Further, if the transient current during the predetermined duration is higher than a threshold, an engine autostart may be requested.

[0036] Fig.3 shows a possible flowchart for a sequence of operations for handling the described autostart logic. At operation 302, the engine 112 may have automatically stopped. That is, at a previous time, conditions were such that an engine autostop was initiated. At operation 304, the pre-activation battery current is measured or otherwise estimated. At operation 306, the pre-activation battery current is compared to the predetermined autostart current threshold. If the pre-activation current is greater than or equal to the threshold, then operation 322 may be executed to request an autostart. In some embodiments, the pre-activation current must be greater than the threshold for a predetermined time before operation 322 is executed.

[0037] If the pre-activation current is less than the threshold, then operation 308 is executed to determine whether the electrical load 118 has entered an activated state. If no activations are detected, execution may return to operation 304. If an activation is detected, operation 310 may be executed to determine the post-activation battery current. Operation 312 may be executed to determine the transient current. Operation 314 may be executed to update the duration since activation. This may be implemented as a counter that is reset upon entering the auto-stopped state.

[0038] Operation 316 may be executed to compare the transient current to the maximum expected transient current threshold. If the transient current is greater than or equal to the threshold, operation 322 may be executed to request an engine autostart. If the transient current is less than the threshold, operation 318 may be executed to compare the post-activation duration to a predetermined duration threshold. If the duration is less than the threshold, then operation 320 may be executed to prevent engine autostarts. After preventing autostarts, execution may return to operation 310 to check the post-activation current and monitor the post-activation duration.

[0039] If the duration is greater than or equal to the threshold, then operation 324 may be executed to compare the post-activation current to the predetermined autostart threshold. If the post-activation current is greater than or equal to the threshold, then operation 322 may be executed to request an engine autostart. If the post-activation current is less than the threshold, then execution may return to operation 304.

[0040] The system minimizes the time spent with the engine automatically stopped and eliminates annoying auto-start / auto-stop cycles that impact customer satisfaction. It also preserves fuel economy and battery energy by eliminating annoying auto-start cycles.

[0041] The processes, methods, or algorithms disclosed herein may be deliverable to / implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or a dedicated electronic control unit. Likewise, the processes, methods, or algorithms may be stored as controller- or computer-executable data or instructions in many forms, including, but not limited to, information permanently stored on non-writable storage media, such as read-only memory devices, and information modifiably stored on writable storage media, such as floppy disks, magnetic tapes, compact discs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software-executable object.Alternatively, the processes, methods, or algorithms may be embodied in whole or in part using suitable hardware components, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), state machines, controllers, or other hardware components or devices, or a combination of hardware, software, and firmware components.

[0042] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the description are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As described above, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated.Although various embodiments may have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, one of ordinary skill in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system properties depending on the specific application and implementation. These properties may include, but are not limited to, cost, robustness, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc.Therefore, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle comprising: a controller programmed to, in response to activation of an electrical load, prevent engine auto-start until a predetermined duration has elapsed as long as a difference between a post-activation battery current exceeding a predetermined auto-start threshold for a portion of the duration and a pre-activation battery current is less than a predetermined difference, and to request engine auto-start in response to the post-activation battery current exceeding the predetermined auto-start threshold after the duration. [2] The vehicle of claim 1, wherein the predetermined duration is longer than an expected duration of a peak current caused by the activation of the electrical load. [3] The vehicle of claim 1, wherein the predetermined difference is based on a maximum expected inrush current of the post-activation battery current. [4] The vehicle of claim 1, wherein the pre-activation battery current is a time-averaged current during a predetermined period of time prior to activation of the electrical load. [5] The vehicle of claim 1, wherein the controller is further programmed to request an engine auto-start in response to the difference exceeding the predetermined difference during the duration. [6] Vehicle comprising: a power machine, an electrical consumer, and a controller programmed to request an engine auto-start when a battery current exceeds a predetermined current, and in response to the battery current exceeding the predetermined current within a predetermined duration beginning with detection of a transition of the electrical load to an activated state, preventing an auto-start of the engine until the expiration of the predetermined duration as long as a difference between a magnitude of the battery current before and after the detection is less than a predetermined difference. [7] The vehicle of claim 6, wherein the predetermined duration is longer than an expected duration of a peak current caused by the transient. [8] The vehicle of claim 6, wherein the controller is further programmed to request an auto-start of the engine in response to the difference exceeding the predetermined difference for the predetermined duration. [9] A vehicle according to claim 6, wherein the predetermined duration is a period of time in which an inrush current caused by activation of an electrical load is expected to decay to a steady-state current. [10] The vehicle of claim 6, wherein the magnitude of the battery current prior to detection is a time-averaged battery current over a predetermined period of time prior to the transition. [11] A method comprising: by a control, in response to activation of an electrical load, preventing engine auto-start until a predetermined duration has elapsed, as long as a difference between a post-activation battery current that exceeds a predetermined threshold for a portion of the duration and a pre-activation battery current is less than a predetermined difference, and in response to the post-activation battery current exceeding the predetermined threshold after the duration has elapsed, requesting an engine auto-start. [12] The method of claim 11, further comprising requesting, by the controller, an engine auto-start in response to the difference exceeding the predetermined difference during the duration. [13] The method of claim 11, wherein the predetermined duration is a period of time in which an inrush current is expected to decay to a steady-state current after activation of an electrical load. [14] The method of claim 11, further comprising averaging, by the controller, a battery current over a predetermined period of time prior to activation of an electrical load to generate the pre-activation battery current.

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