CHARGE-STATE-BASED ENGINE START / STOP CONTROL

Abstract

Method for controlling a power machine (12) comprising the following: by means of a processor, from a state (302) - in response to a power machine start condition occurring while a SOC is within a first predetermined range, a running (304) of the power machine (12) until the power machine start condition is no longer present or the SOC reaches a setpoint - whichever occurs first, and then a power machine control system transitions to state (302) in which the power machine (12) is off and the power machine (12) is automatically startable, as well as - in response to a power machine start condition occurring while the SOC is within a second predetermined range lower than the first, the power machine (12) is allowed to run (308) until the SOC reaches the setpoint and then the power machine control system enters state (302).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to methods and systems for controlling starting and stopping of an engine. BACKGROUND

[0002] A vehicle's engine can be automatically started or stopped to meet the vehicle's ongoing energy demands. Control schemes have been used to start and stop the engine to meet such demands. One energy requirement met by the engine in hybrid electric vehicles is maintaining a battery's state of charge. Certain control schemes require the engine to start automatically below a threshold and stop automatically above a threshold. Constantly cycling the engine on and off to meet battery state-of-charge demands can cause unnecessary wear on the engine and starter motor or reduce fuel economy.

[0003] DE 10 2011 116 132 A1 discloses a method for operating a hybrid-powered vehicle. DE 100 38 280 A1 discloses an automatic engine start / stop control device.

[0004] The object of the invention is to provide an improved method for operating a prime mover. SUMMARY

[0005] The problem is solved by the features of the independent patent claim. Advantageous developments of the invention are described in the subclaims.

[0006] A method of operating an engine includes, via a processor, from a state in response to an engine start condition occurring while a state of charge (SOC) is within a first predetermined range, running the engine until either the engine start condition is no longer met or the SOC reaches a target, whichever occurs first, and then an engine control system transitions to a state in which the engine is off and the engine is automatically startable, and in response to an engine start condition occurring while the SOC is within a second predetermined range that is lower than the first, running the engine until the SOC reaches the target and then the engine control system transitions to the state.

[0007] A vehicle includes an engine, a battery, and a controller. The controller, in response to an engine start condition occurring while a battery SOC falls within a first predetermined range, runs the engine until the engine start condition no longer exists or the SOC reaches a target, whichever occurs first, and, in response to an engine start condition occurring while the SOC falls within a second predetermined range that is lower than the first, runs the engine until the SOC reaches the target.

[0008] In one embodiment, the present disclosure includes, in response to the SOC falling below the second predetermined range, running the engine until the SOC reaches the target. The engine start condition may include activation of an electrical load. In a preferred embodiment, the first predetermined range and the second predetermined range are numerically adjacent to each other. The controller may be configured to inhibit engine start when the SOC falls below a minimum threshold. The target may have a value that is higher than values ​​within the first and second predetermined ranges. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a hybrid vehicle; Fig. 2 is a diagram of engine status relative to time before, during, and after an engine start / stop event; Fig. 3 is a flowchart of a control algorithm for determining whether to automatically start or automatically stop an engine; Fig. 4 is a diagram of a battery state of charge with respect to time before, during, and after an engine start / stop event; Fig. 5 is a state diagram of an engine control system. DETAILED DESCRIPTION

[0009] Vehicles can be powered by battery power (BEVs - Battery Electric Vehicles) for propulsion and other electrical loads, such as heating and cooling. The battery can be recharged using a secondary energy source (e.g., a charging station, internal combustion engine, or solar panel). The battery can be arrayed with other batteries to provide additional voltage or longevity, and any type of battery can be used. Any type of battery, including different combinations of electrolyte, anode material, cathode material, or combinations thereof, can power BEVs. Capacitors can also be used to replace or supplement battery arrays. Some common batteries in BEVs include nickel-metal hydride, lead-acid, and lithium-ion.

[0010] Vehicles can also be powered by a combination of battery power and the internal combustion engine. These vehicles, known as hybrid electric vehicles, typically use a combination of battery and engine power and draw on these sources to power auxiliary electrical loads. Electrical loads can include heated windshields, interior heaters, interior cooling, auxiliary blowers, sound systems, power windows, wireless communication links, turn signals, or other electrical devices necessary for using and occupying a vehicle. To replace withdrawn electrical energy, the engine can be used to recharge the battery via a mechanically coupled electrical generator.There are many known designs used in hybrid vehicles to mechanically couple the engine to a generator (e.g., a power split design using a planetary gear set). All of these designs are contemplated in this disclosure. The vehicle may also utilize multiple engines or power generators. Any combination or types of engines, power generators, and alternators are also contemplated in this disclosure. One example includes a gasoline internal combustion engine and an integrated starter generator (ISG). An integrated starter generator may provide engine cranking while generating electricity after the engine has started.

[0011] A hybrid vehicle controller may include multiple controllers used to control multiple vehicle systems (referred to herein as a controller). For example, a controller may be a Vehicle System Controller / Powertrain Control Module (VSC / PCM). In this regard, the vehicle engine stop / start control portion of the VSC / PCM may be software embedded within the VSC / PCM, or it may be a separate hardware device. A controller would generally include any number of processors, ASICs, ICs, memory (e.g., Flash, ROM, RAM, EPROM, and / or EEPROM), and software code that cooperate to perform a series of operations. A microprocessor within a controller may further include a clock to provide timing and synchronization.A controller can communicate with other components via a CAN bus or a controller area network or using other communication protocols.

[0012] A controller may be designed with an optimal battery state of charge (SOC), which is generally below the maximum battery charge. Batteries within an array may have different maximum charge levels. The battery (array) target may be set to 70% of a hypothetical maximum charge because the maximum charge of each individual battery may be uncertain. This 70% target may be set higher or lower depending on manufacturer specifications or requirements. This disclosure contemplates that the target may be set to the actual maximum battery charge or could be set to a lower value. The controller may allow an auto-stop or initiate an auto-stop when the battery SOC is equal to or greater than the target.An auto-stop of the engine would then stop the generation of electricity, which can prevent the battery from being overcharged.

[0013] The controller may be designed with a first predetermined range that is numerically adjacent to or lower than the target. For example, the target may be an SOC of 70%, and the first predetermined range would be an SOC between 70% and 68%. The 68% SOC may vary based on a calibration of the battery before leaving the factory, or the 68% SOC may be calibrated based on ambient conditions during use. This design data may be set by a user or set via communication links with the factory. No exact thresholds are inherent in this disclosure. The controller may be designed so that when the SOC is within the first predetermined range, the engine may automatically stop or automatically start when an engine stop / start condition exists.

[0014] The controller may be configured with a second predetermined range that is numerically adjacent to or lower than the first predetermined range. For example, the first predetermined range may be set for SOCs between 70%-68%, and the second predetermined range may be set for SOCs between 68%-67% (i.e., the first and second predetermined ranges are numerically adjacent to each other). Each range may include the threshold number. The controller may be configured such that when the SOC is within the second predetermined range, the engine may automatically start when an engine start condition exists. The controller may further be configured such that when an auto-start occurs within the second predetermined range, the controller prevents an auto-stop from occurring until the target is reached.

[0015] The controller may start the engine when an engine start condition occurs while the SOC is within a first predetermined range. The controller may run the engine until the condition no longer exists or the SOC reaches a desired SOC, whichever occurs first.

[0016] The controller may start the engine when an engine start condition occurs while the SOC is within a second predetermined range. The second predetermined range may be lower than the first. The controller may run the engine until the SOC reaches a desired SOC.

[0017] The controller may be configured to automatically start the engine when the SOC falls below the second predetermined range, even if no condition exists. A deadband may exist between the lower threshold of the second predetermined range and the unconditional engine autostart, despite the presence of an engine autostart condition. This means that the controller may be configured such that the lower threshold of the predetermined range is set to 67%, and the engine autostart occurs without a condition when the SOC falls below 65%.

[0018] The controller may also be configured to prohibit an autostart if the SOC falls below a minimum threshold. An engine start requires a high cranking current, which places a significant strain on the battery. A controller may prevent an engine from automatically starting below this threshold and require a user-initiated cold start. This prevents additional battery drain caused by attempts to restart the engine when an engine start failure is present. An example setting for this minimum threshold is an SOC of 60%.

[0019] Referring to Fig. 1, a hybrid vehicle 10 may include an engine 12, an ISG 14, a battery 16, electrical loads 18, and a controller 20. The engine may have a direct mechanical connection to the ISG 14. The ISG may be electrically connected to the battery 16 and the electrical loads 18. The battery 16 may be connected to the electrical loads 18. The controller 20 may be in communication with the engine 12, the ISG 14, and the battery 16.

[0020] Referring to Fig. 2, an engine auto-stop event can include multiple stages. "Auto-Stop Inception" marks the onset of the engine auto-stop event. "Prepare for Engine Auto-Stop" is the period during which vehicle systems, including the engine, prepare for the impending engine stop. "Fuel Shutoff" marks the point at which fuel flow to the engine is stopped. "Engine Stops" is the period during which engine speed decreases to 0. "Below Fuel Restart" marks the point at which, if a restart is requested during the "Engine Stops" stage, the starter motor may need to be engaged to crank the engine (if a restart is requested before "Below Fuel Restart" and during the "Engine Stops" stage, the engine can be restarted by restoring fuel flow)."Engine Speed ​​= 0" marks the point at which the engine speed is near or equal to 0. "Engine Auto Stop Executed" marks the period of time when the engine is off. "Starter Engage" marks the point at which the starter motor begins to crank the engine in an effort to start the engine (in response to detecting an engine auto-start condition). "Starter Cranks Engine" is the period of time when the engine is unable to turn over under its own power. "Starter Disengage" marks the point at which the engine is able to crank under its own power. "Engine Speed ​​Increasing" is the period of time when the engine speed increases up to its operating speed (a speed at or above the desired idle speed). Finally, "Auto Start End" marks the point at which the engine speed reaches its operating speed.

[0021] In at least one case, the controller may allow an autostart when the SOC falls below a minimum threshold if the engine has not reached "below fuel restart." This may be because additional cranking by the starter motor is not required and the engine can simply restart with a re-injection of fuel if the engine does not fall below fuel restart.

[0022] Now referring to Fig. 3, a method 100 is illustrated whereby a vehicle controller performs an embodiment of this disclosure. The method 100 is intended to operate continuously. In step 101, the controller receives a battery voltage and determines the battery SOC. In step 102, the controller receives an engine status and determines the engine status. In step 104, the controller determines whether an engine is on. If the engine is on, the controller determines whether the SOC is less than a desired value in step 106.

[0023] In step 108, if the SOC is not lower than the target and the engine is on, the controller may automatically stop the engine.

[0024] In step 110, if the SOC is lower than the target, control may determine whether the engine was automatically started due to a condition within the first predetermined range. If step 110 is false, control may loop back and restart the process.

[0025] If step 110 is true, control may determine whether an autostart condition exists in step 112. If the determination in step 112 indicates that an autostart condition exists, control may return and restart the process.

[0026] In step 114, if the determination in step 112 indicates that no autostart condition exists, the controller may automatically stop the engine and restart the process.

[0027] Further referring to Fig. 3, if control determined that the engine was off in step 104, control may determine whether the SOC is lower than the target in step 116. If the SOC is not lower than the target, control may loop back and restart the process.

[0028] If control determined in step 116 that the SOC is lower than the target, control determines in step 118 whether the SOC is lower than the minimum threshold for disabling an engine auto-start. After determining that the SOC is lower than the minimum threshold for disabling an engine auto-start, control may disable an engine auto-start and require an engine cold start in step 120.

[0029] If the result of step 118 is false, control may determine whether an autostart condition exists in step 122. If an autostart condition exists in step 122, the engine automatically starts in step 124, and control may loop back and restart the process.

[0030] If the result of step 122 is false, control may determine whether the SOC is lower than the minimum desired battery level in step 126. If the SOC is lower than the minimum desired battery level in step 126, control may automatically start the engine in step 128. Otherwise, control may loop back and restart the process.

[0031] Now referring to Fig. 4, a diagram 200 is shown whereby a vehicle controller implements an embodiment of this disclosure. Starting on the left of the diagram and moving to the right, the controller determines the SOC of the battery at point 202. If the SOC begins to decrease due to activation of electrical loads, the SOC drops below the second predetermined range. The controller then automatically starts the engine at point 204 without an auto-start condition. Automatic stopping of the engine is inhibited until the SOC is higher than the target. If the SOC is higher than the target, the engine is automatically stopped at point 206, causing the SOC to decrease. At point 208, the SOC then drops into the first predetermined range. At point 208, an engine auto-start condition is met, and the engine automatically starts to increase the SOC of the battery.At point 210, the engine auto-start condition is no longer met, and the engine automatically stops. The SOC begins to fall back into the first predetermined range until another engine auto-start condition is met at point 212. The engine charges the battery until the battery SOC is not lower than the target. When the SOC reaches the target, the engine automatically stops at point 214, even if the condition is met. The SOC begins to decrease and passes through the first predetermined range without an auto-start condition being met. The SOC falls into the second predetermined range, and the SOC continues to decrease until an auto-start condition is met at point 216. The engine is automatically started, and the SOC begins to increase. At point 218, the engine auto-start is maintained even though the auto-start condition is no longer met.The SOC then reaches the target and the engine is automatically stopped.

[0032] Now referring to Fig. 5 illustrates a state diagram 300 illustrating at least one embodiment of this disclosure. Beginning in state 302, the engine is off and the engine may automatically start. If the SOC is within the first predetermined range lower than the target and an auto-start condition exists, the engine may automatically start and the system may transition to state 304. The system may return to state 302 if the auto-start condition no longer exists or the SOC is greater than or equal to the target. The system may transition to state 306 if the SOC is below a minimum threshold. The system may return to state 302 if the SOC is greater than or equal to the minimum threshold.

[0033] From state 302, if the SOC is lower than the second predetermined range, the system may start the engine and prevent an engine auto-stop while transitioning to state 308. The system may then return to state 302 if the SOC is higher than or equal to the target. The system may also transition to state 308 if the SOC is lower than the target within the second predetermined range and an auto-start condition exists. The system may then remain in state 308 until the SOC is higher than or equal to the target.

[0034] The processes, methods, or algorithms disclosed herein may be deliverable to or implemented by a processing device, a controller, or a 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 data and instructions executable by a controller or computer in many forms, including, but not limited to, information permanently stored on non-writable storage media, such as read-only devices, and information modifiably stored on writable storage media, such as floppy disks, magnetic tapes, compact discs, random access memory 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 implemented 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.

[0035] It is further described: A. A method of operating a prime mover comprising: by means of a processor, in response to an engine start condition occurring while a SOC is within a first predetermined range, running the engine until the engine start condition is no longer met or the SOC reaches a target, whichever occurs first, and in response to an engine start condition occurring while the SOC is within a second predetermined range that is lower than the first, running the engine until the SOC reaches the target. B. The method of A, further comprising, in response to the SOC falling below the second predetermined range, running the engine until the SOC reaches the target. C. The method of A, wherein the engine start condition comprises activation of an electrical load. D. The method of A, wherein the first predetermined region and the second predetermined region are numerically adjacent to each other. E. The method of A, further comprising, in response to the SOC falling below a minimum threshold, inhibiting engine start. F. The method of A, wherein the target has a value that is higher than values ​​within the first and second predetermined ranges. G. The method of A, further comprising adjusting the first predetermined range according to design data. H. Vehicle comprising: a power machine; a battery; and a control system designed to in response to an engine start condition occurring while a SOC of the battery falls within a first predetermined range, run the engine until the engine start condition is no longer met or the SOC reaches a target, whichever occurs first, and in response to an engine start condition occurring while the SOC falls within a second predetermined range that is lower than the first, running the engine until the SOC reaches the target. I. The vehicle of H, wherein the controller is further configured to, in response to the SOC falling below the second predetermined range, run the engine until the SOC reaches the target. J. The vehicle of claim 1, wherein the engine start condition includes activation of an electrical load. K. Vehicle according to H, wherein the first predetermined area and the second predetermined area are numerically adjacent to each other. L. Vehicle comprising: a power machine; a battery; and a controller configured to terminate an engine on-cycle with an auto-stop when an engine start condition is no longer met or a battery SOC reaches a target, whichever occurs first, in response to the engine on-cycle beginning with an auto-start, which is triggered by the engine start condition occurring while the SOC is in a first predetermined range that is lower than the target. M. The vehicle of L, wherein the controller is further configured to end the engine on-cycle with an auto-stop when the SOC reaches the target, in response to the engine on-cycle beginning with an auto-start triggered by the engine start condition occurring while the SOC is in a second predetermined range that is lower than the first predetermined range. N. Vehicle according to M, wherein the controller is further configured to inhibit autostart in response to the SOC falling below a minimum threshold. O. Vehicle according to L, wherein the engine start condition comprises a presence of an electrical load.

Claims

[1] A method for controlling a prime mover (12) comprising: by means of a processor, from a state (302) - in response to an engine start condition occurring while an SOC is within a first predetermined range, running (304) the engine (12) until the engine start condition is no longer met or the SOC reaches a target, whichever occurs first, and then an engine control system transitions to the state (302) in which the engine (12) is off and the engine (12) is automatically startable, and - in response to an engine start condition occurring while the SOC is within a second predetermined range that is lower than the first, running (308) the engine (12) until the SOC reaches the target and then the engine control system transitions to state (302). [2] The method of claim 1, further comprising, in response to the SOC falling below the second predetermined range, running the engine (12) until the SOC reaches the target. [3] The method of claim 1, wherein the engine start condition comprises activation of an electrical load (18). [4] The method of claim 1, wherein the first predetermined area and the second predetermined area are numerically adjacent to each other. [5] The method of claim 1, further comprising, in response to the SOC falling below a minimum threshold, inhibiting engine start. [6] The method of claim 1, wherein the target has a value that is higher than values ​​within the first and second predetermined ranges. [7] The method of claim 1, further comprising setting the first predetermined range according to design data.

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