Internal combustion engine speed stabilization

Abstract

Vehicle comprising: an internal combustion engine (20); and a control unit (38) configured to start, in response to an actuation of an accelerator pedal (40) during engine braking, a timer (120) having a timer duration (122) defined by a charge limit of a traction battery (36) during which engine braking is maintained and a predetermined limit of a change rate of rotational speed of the internal combustion engine (20) is reduced; and, in response to the expiry of the timer (120), to increase the predetermined limit of the change rate of rotational speed of the internal combustion engine (20).

Description

TECHNICAL AREA

[0001] The present disclosure relates to engine speed stabilization. BACKGROUND

[0002] Vehicles can use engine braking to supplement friction or regenerative braking. The negative torque provided by engine braking can be proportional to, or otherwise related to, the engine speed. Actuation of the accelerator pedal can cause a vehicle system control unit to reduce engine braking torque by lowering the engine speed, which can alter audible engine noise perceived by vehicle occupants. This change in perceived noise can be disturbing to vehicle occupants, especially if engine braking and engine propulsion sound similar. SUMMARY

[0003] A vehicle includes an engine. The vehicle includes a control unit configured to start a timer with a duration defined by a traction battery charge limit, during which engine braking is maintained and a predetermined rate-of-change engine speed limit is reduced. The timer is started in response to accelerator pedal input during engine braking. The control unit is further configured to increase the predetermined rate-of-change engine speed limit, so that engine braking is predicted based on the battery limit, in response to accelerator pedal input during engine braking.

[0004] A vehicle includes an engine. The vehicle includes a control unit configured to start a timer with a duration defined by a traction battery charge limit. The control unit is configured to decrease a predetermined rate-of-change limit for the engine speed. The control unit can start the timer and decrease the rate in response to the release of the accelerator pedal during engine acceleration. The control unit is further configured to increase the predetermined rate of change of the limit as the timer expires.

[0005] A vehicle comprises an engine. The vehicle comprises a control unit configured to start a timer with a duration defined by the charge limit of a traction battery. The control unit is configured to maintain an engine speed using the vehicle's wheel torque and the response force of an alternator associated with the vehicle. The control unit is further configured to increase the predetermined rate of change of the engine speed in response to the expiration of the timer. List of characters Fig. Figure 1 is a schematic diagram of a hybrid vehicle; Fig. Figure 2 is a graph that includes an accelerator pedal tip-in, an engine speed reduction, and a timer; Fig. Figure 3 is a graph that includes an accelerator pedal tip-out, an engine speed reduction, and a timer; Fig. Figure 4 is a graph that includes a timer duration and charging limits of a traction battery; and Fig. Figure 5 is a flowchart of a timer used to reduce the rate of change of motor speed for a predetermined duration. DETAILED DESCRIPTION

[0006] Embodiments of the present disclosure are described herein. However, it is understood that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of certain components. Consequently, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art the various uses of the present invention. As those skilled in the art understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not expressly illustrated or described.The combination of features presented provides representative embodiments for typical applications. However, different combinations and modifications of the features, consistent with the teachings of this disclosure, might be desirable for specific applications or implementations.

[0007] Internal combustion engines in hybrid electric vehicles can be used to slow the vehicle through engine braking. Various types of engine braking are available and can be used in hybrid electric vehicles. Engine braking can utilize self-compression caused by the piston stroke and intrinsic frictional forces to resist engine rotation, thereby imparting negative torque to the powertrain.

[0008] The engine's rotation can provide vehicle occupants with an audible indication of vehicle operation. This means that occupants can discern vehicle acceleration characteristics from the sounds produced by the engine. Hybrid vehicles that employ engine braking, as discussed above, can confuse occupants because noises caused by engine speed do not correspond to torque delivered to the powertrain or to vehicle acceleration and deceleration. A timer can be implemented to reduce irregular engine speeds and lessen confusion for vehicle occupants. The timer can be based on engine braking prediction. Engine braking prediction can be based on road gradient, battery charge limits, and other factors. Battery charge limits specify the amount of regenerative braking available. As charge limits decrease based on the battery's state of charge, regenerative braking capacity is reduced.With reduced regenerative braking capacity, unstable engine speeds can be predicted because engine braking, along with reduced regenerative braking capacity, will be used to maintain vehicle speed when descending a downhill road with a gradient that requires vehicle speed management.

[0009] A powertrain for a hybrid electric vehicle is in Fig. 1. Schematically represented. The powertrain comprises an internal combustion engine. 20 , which can be powered by a planet carrier 22 connected to an alternator 24 , which can be driven by a sun wheel 26 is connected, and an output shaft 28 , which can be driven by a ring gear 30is connected. Elements are connected in a driveable manner if a mechanical energy flow path exists between them such that the rotational speeds of the elements are restricted to be essentially proportional. The planetary carrier 22 supports a set of planetary gears 32 , so that each planetary gear meshes continuously with the sun gear 26 and the ring gear 30 is. The output shaft 28 It drives the vehicle wheels directly or indirectly, for example by means of a differential arrangement.

[0010] A traction engine 34 It can be driven by the output shaft 28 connected. Both the alternator 24 as well as the traction motor 34These are reversible electrical machines capable of converting electrical energy into mechanical rotational energy or vice versa. The terms alternator and motor should be considered merely as designations for easier description and do not restrict the function or operation of any of these electrical machines. The alternator 24 and the traction motor 34 Both are electrically powered by a battery 36 tied together.

[0011] The rotational speed of the sun gear 26 , of the carrier 22 and the ring gear 30 They behave linearly with each other, so that the rotational speed of the carrier 22 a weighted average of the rotational speed of the sun gear 26 and the ring gear 30 is. Therefore, the engine speed is 20 in this arrangement not restricted to being proportional to the rotational speed of the output shaft 28to be. Instead, the engine speed can be selected or controlled independently of the vehicle speed by adjusting the alternator speed accordingly. Energy flows from the engine to the output shaft through a combination of mechanical and electrical energy transmission. In some operating conditions, the engine 20 generate more energy than is supplied to the output shaft 28 is supplied, with the difference, neglecting efficiency losses, being sent to a battery. 36 is supplied. Under other operating conditions, the battery may 36 in combination with the alternator 24 and / or the traction motor 34 to supplement the energy supplied by the engine 20 is delivered so that more energy is sent to the output shaft. 28 will be delivered.

[0012] The engine 20 , the alternator 24 and the traction motor 34They all respond to control signals from a control unit. 38 These control signals determine the amount of torque generated. The control unit also receives speed signals from the engine. 20 , the alternator 24 and the traction motor 34 and a charge level signal from the battery 36 The control unit receives input signals indicating a driver's intention from an accelerator pedal. 40 and a road gradient detection system 46 to.

[0013] Fig. 2 represents a vehicle accelerator pedal position 102 , an engine speed 110 and a timekeeper status 120 This shows the curve of the accelerator pedal position. 102 shows a tip-in event 104 on, while the vehicle 10is on a downhill slope and a speed assist system is activated. The accelerator pedal indicates that the driver may require acceleration. The tip-in event 104 can be based on a percentage change or a rate of change of the accelerator pedal position 102 The control unit determines which indicate a change in the driver's requirements. 38 can be configured to react to changes in pedal position 102 the engine speed 110 in normal operation to point 116 as shown, to lower the engine speed. During normal operation, the engine speed can be reduced. 110 a rate of change 112 exhibit. In response to the tip-in event 104 can a timer 120 to point 124 with a duration 122 to be initiated. The timer 120 can the rate of change 112 decrease, so that the engine speed110 is maintained, as in curve 114 shown. The engine speed 110 can result in a reduced rate of change 112 exhibit, so that the curve 114 is not horizontal. The curve 114 The curve can be positively or negatively linear. 114 It can be concave, convex, or a completely different function. The reduced rate of change 112 can depend on the time cue duration 122 depend on or on the tip-in event duration 106 depend on it, which would increase over time.

[0014] Fig. 3 represents a vehicle accelerator pedal position 202 , an engine speed 210 and a timekeeper status 220 This shows the curve of the accelerator pedal position. 202 shows a tip-out event 204 on, while the vehicle 10The vehicle is on a downhill slope and a speed assist system is activated. The driver may have been accelerating down the slope and is now taking their foot off the accelerator. This is the tip-out event. 204 can be based on a percentage change or a rate of change of the accelerator pedal position 202 The control unit determines which indicate a change in the driver's requirements. 38 can be configured to react to changes in pedal position 202 the engine speed 210 in normal operation to point 216 as shown, to lower the engine speed. During normal operation, the engine speed can be reduced. 210 a rate of change 212 exhibit. In response to the tip-out event 204 can a timer 220 to point 124 with a duration 222 to be initiated. The timer 220 can the rate of change 212decrease, so that the engine speed 210 is maintained, as in curve 214 shown. The engine speed 210 can result in a reduced rate of change 212 exhibit, so that the curve 214 is not horizontal. The curve 214 The curve can be positively or negatively linear. 214 It can be concave, convex, or a completely different function. The reduced rate of change 212 can depend on the time cue duration 222 depend.

[0015] Fig. 4 represents a graph 300 a timer 304 and of loading limits 306 This represents the zeitgeber limit curve. 302 reveals time cue durations 304 against loading limits 306 The loading limits 306 can be determined by the charge level of the traction battery 36 based on the loading limits 306 can be based on thermal limits. As shown, the charging limit can be on an order of magnitude306 inversely proportional to the duration of the time cue 304 be. The duration of the time cue 304 is zero when the load limit 306 a maximum charging limit or charging limit threshold associated with the traction battery 36 is associated and can vary depending on the battery manufacturer and model.

[0016] Fig. 5 represents a flowchart 400 The flowchart begins at the start. 402 The control unit 38 determined in step 404 , whether the engine 20 turns. In step 406 determines the control unit 38 , whether an accelerator pedal 40 The determination of whether the accelerator pedal was pressed or released. 40The response, whether the accelerator pedal has been pressed or released, can depend on a percentage change in the accelerator pedal position, an absolute pedal position exceeding a limit, or a combination thereof. When the accelerator pedal... 40 in step 406 was activated or released, can be in step 408 a timer 304 The start of the timer can be adjusted or delayed to compensate for other environmental factors.

[0017] During the specified time period 302 can the control unit 38 in step 410 a rate of change of the engine speed limit 110 , 210 decrease. This means that the rate of change 112 , 212 the engine speed 20is limited. In other words, it can be maintained in certain configurations. For example, the motor can have a specific speed determined by a torque setting of the control unit. 38 is driven. The torque setting can be determined by the accelerator pedal position or environmental factors. In a situation with speed control, the engine speed can be adjusted. 110 , 210 familiarize yourself with the position of the accelerator pedal 40 change. For example, engine braking torque can be adjusted at a specific speed. 110 , 210 based on the engine. If the engine speed 110 , 210 As the engine braking torque increases, so does the engine braking torque. Pressing the accelerator pedal in this situation can cause the engine speed to increase. 110 , 210 decreases, which reduces the negative torque from the engine 20 would lower it. Under conditions with a low load limit. 306(e.g., a high battery charge level) can be used to anticipate engine braking during a downhill drive with vehicle speed control activated. Consequently, the engine speed can be adjusted. 110 , 210 maintained while engine torque is reduced to anticipate future engine braking. Maintaining the rotational speed 110 , 210 The engine's noise level can reduce driver confusion caused when vehicle speed is maintained and engine speed varies, because drivers generally associate engine noise with vehicle speed. 110 , 210 the engine can last for a certain period of time 122 , 222 of the timer 304 be maintained. The rate of change of rotational speed 110 , 210 the engine can last for a certain period of time 122 , 222 of the timer 304 will be reduced. If the timer is in step412 As the process unfolds, the rate of change of the motor's rotational speed can be measured in step 414 can be changed. The process can be changed in step 416 end or run continuously.

[0018] The words used in the specification are descriptive rather than limiting, and it is understood that various modifications may be made without altering the meaning and scope of the disclosure. As previously described, features of different embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. Although different embodiments may have been described as providing advantages over other embodiments or implementations of the prior art with respect to one or more desired characteristics, those skilled in the art will recognize that one or more features or characteristics can be combined to achieve desired overall system attributes, which depend on the specific application and implementation.These attributes may include, but are not limited to, cost, strength, durability, life-cycle costs, marketability, appearance, packaging, size, usability, weight, manufacturability, ease of assembly, etc. Examples described as less desirable than other embodiments or implementations of the prior art with respect to one or more characteristics are not, as such, outside the scope of protection of the disclosure and may be desirable for certain applications.

Claims

[1] Vehicle, comprising: an engine; and a control unit configured to in response to the activation of an accelerator pedal during engine braking, to start a timer with a duration defined by a traction battery charge limit, during which engine braking is maintained and a predetermined rate-of-change-speed limit of the engine is reduced; and to increase the predetermined rate of change speed limit in response to the expiration of the timer. [2] Vehicle according to claim 1, wherein the charging limit is based on a state of charge of the traction battery. [3] Vehicle according to claim 2, wherein the magnitude of the loading limit is inversely proportional to the duration. [4] Vehicle according to claim 3, wherein the duration is zero when the charging limit is greater than a charging limit limit associated with the traction battery. [5] Vehicle according to claim 1, wherein an output torque of the motor increases during the duration. [6] Vehicle according to claim 5, wherein the output torque of the motor is canceled during the period by an electric motor associated with a drive train of the vehicle. [7] Vehicle according to claim 6, wherein the electric motor accelerates the vehicle during the duration. [8] Vehicle according to claim 1, wherein the predetermined rate of change speed limit is reduced so that a speed of the engine is maintained during the duration. [9] Vehicle according to claim 8, wherein the speed is maintained by a wheel torque of the vehicle and a reaction force of an alternator. [10] Vehicle according to claim 1, wherein the predetermined rate of change speed limit is negative. [11] Vehicle, comprising: an engine; and a control unit configured to in response to the release of an accelerator pedal during engine acceleration, to start a timer with a duration defined by a traction battery charge limit, and to reduce a predetermined rate-of-change limit of the engine speed; and to increase the predetermined rate of change threshold in response to the expiration of the timer. [12] Vehicle according to claim 11, wherein the charging limit is based on a state of charge of the traction battery. [13] Vehicle according to claim 11, wherein the magnitude of the loading limit is inversely proportional to the duration. [14] Vehicle according to claim 13, wherein the duration is zero when the charging limit is a maximum charging limit associated with the traction battery. [15] Vehicle according to claim 11, wherein an output torque of the motor decreases during the duration.

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