System and method for controlling a powertrain

Abstract

Vehicle (10), comprising: a controller (40) which is programmed to to operate a powertrain (12) in hybrid mode; and in response to a request to operate the powertrain (12) in electric mode, to switch the powertrain operation from hybrid mode to electric mode without shifting gears until a change in the accelerator pedal position exceeds a threshold value after the switch, wherein the control unit (40) is further programmed to switch the powertrain operation from electric mode to recuperation mode in response to a request to operate the powertrain (12) in a recuperation mode and to a brake pedal tip-in while the powertrain (12) is operating in electric mode, without shifting gears, until a change in the brake pedal position exceeds a threshold value after the switch.

Description

TECHNICAL AREA

[0001] The present disclosure relates to techniques for controlling a powertrain and planning transmission shifting operations. BACKGROUND

[0002] Vehicles may be equipped with a transmission designed to operate with a discrete number of fixed gear ratios. The available gear ratios may be referred to as gears or gear stages, even though there is no direct correspondence between each ratio and a specific physical gear position in the transmission. Typically, the ratios are numbered, starting with the highest ratio and proceeding down to lower ratios. For example, first gear may have a ratio of 4.5, second gear a ratio of 3.0, third gear a ratio of 2.3, and so on. At low vehicle speeds, the transmission is usually operated at a high gear ratio, allowing the transmission to amplify the engine torque for improved acceleration.At high vehicle speeds, the transmission is usually operated with a low gear ratio, which allows a power engine speed that is associated with smooth and fuel-efficient driving.

[0003] A specific gear ratio can be selected from the set of available gear ratios by engaging certain switching elements, such as clutches, brakes, or the like. Switching elements can include actively controlled devices and passively controlled devices, such as freewheel clutches. If the currently selected gear ratio is not optimal, the transmission shifts to a different gear ratio by disengaging one or more switching elements and engaging one or more switching elements. For example, if the currently selected gear ratio results in a power engine speed higher than an optimal or efficient power engine speed, the transmission can shift up to a lower gear ratio.On the other hand, if the currently selected gear ratio results in an engine speed that is not optimal or efficient, the transmission may downshift to a higher gear ratio. During this shift, vehicle occupants may notice fluctuations in output torque and changes in engine noise.

[0004] Modern automatic transmissions use control units both to decide when to shift gears and to control the shifting elements to execute the shift as smoothly as possible. Sometimes a control unit schedules a shift as a direct response to a driver action, such as an abrupt change in accelerator pedal position. In these circumstances, the driver may expect the transmission to shift and will be pleased to feel a shift. At other times, a control unit schedules a shift due to a gradual change in vehicle speed or pedal position. When a vehicle is traveling at a constant speed over level ground, the occupants expect the transmission to remain in the currently selected gear.

[0005] DE 10 2015 113 713 A1 discloses a hybrid electric vehicle with a gear-shift transmission that switches between different operating modes according to individual shift patterns. DE 10 2010 005 532 A1 discloses a method for determining a target gear ratio for a hybrid vehicle that can be operated in different modes. JP 2014 - 40 218 A discloses a vehicle control device that makes it possible to improve the recovery rate of renewable energy. BRIEF SUMMARY OF THE REVELATION

[0006] A vehicle can contain a power unit, a transmission, and a control unit. The transmission can be configured for selective coupling with the power unit. The control unit can be programmed to drive the transmission to maintain an actual gear in response to a request to decouple the power unit from the transmission, received when the traction battery charge level is greater than a threshold charge level, when the vehicle speed decreases below a threshold reduction, and when the accelerator pedal position is within a predetermined range. The actual gear level can be maintained so that the transmission does not shift after the power unit decouples from the transmission, as long as the vehicle speed remains essentially constant and the traction battery charge level remains greater than the threshold charge level.

[0007] A vehicle contains a control unit programmed to operate a powertrain in hybrid mode. Furthermore, the control unit is programmed to switch the powertrain operation from hybrid mode to electric mode in response to a request to operate the powertrain in electric mode, without shifting gears, until a change in the accelerator pedal position exceeds a threshold after the switch.

[0008] A method for controlling a powertrain may include operating the powertrain in a hybrid mode while in first gear. Furthermore, in response to a request to operate the powertrain in an electric mode associated with an accelerator pedal tip-out, while the traction battery state of charge (SOC) is greater than a threshold SOC, the method may include switching operation from hybrid mode to electric mode while maintaining first gear until an accelerator pedal position changes. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic representation of a powertrain of a hybrid vehicle with a step-change transmission. Fig. 2 is a flowchart that describes the changes within a set of switching diagrams. Fig. Figure 3 is a graphical representation of a circuit diagram for a hybrid electric operating mode. Fig. Figure 4 is a graphical representation of a circuit diagram of a purely electrical operating mode. Fig. 5A and Fig. 5B are flowcharts that depict a procedure for controlling a vehicle. DETAILED DESCRIPTION

[0009] Detailed embodiments of the present invention are disclosed here as required; however, it is understood that the disclosed embodiments are purely exemplary of the invention, which can be implemented in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed herein should therefore not be interpreted as limiting, but merely as a representative basis for teaching a person skilled in the art how the present invention can be used in various ways.

[0010] With reference to Fig. Figure 1 shows a schematic diagram of a vehicle 10 according to an embodiment of the present disclosure. The physical placement and orientation of the components within the vehicle may vary. Although the powertrain of Fig. As described in particular in Section 1, the strategies according to embodiments of the present disclosure can also be applied to other powertrain configurations.

[0011] The vehicle 10 may contain a powertrain 12. The powertrain 12 may contain a power machine 14 coupled to a transmission 16. The power machine 14 may be configured to drive the transmission 16. As described in more detail below, the transmission 16 may contain a disconnect clutch 18, an electric machine, such as an electric motor / generator (M / G) 20, an associated traction battery 22, a transmission input shaft 24, a starting clutch or torque converter 26, and a multi-stage automatic transmission or gear transmission 28 of the transmission.

[0012] The power unit 14 can be selectively coupled to the M / G 20 via the disconnect clutch 18. Both the power unit 14 and the M / G 20 are capable of providing drive power to the vehicle 10 by supplying torque to the gear unit 28 of the transmission.

[0013] The disconnect clutch 18 can disengage to decouple the power unit 14 from the rest of the drivetrain 12, allowing the M / G 20 to act as the sole power source for the vehicle 10. Power flow from the power unit 14 to the M / G 20 or from the M / G 20 to the power unit 14 is possible when the disconnect clutch 18 is at least partially engaged. When the disconnect clutch 18 is engaged, the M / G can, for example, act as a generator to convert rotational energy supplied by a crankshaft into electrical energy to be stored by the traction battery 22.

[0014] The M / G 20 can be implemented by any of several types of electric machines. For example, the M / G 20 can be a permanent magnet synchronous motor. Power electronics can condition a direct current supplied by the traction battery 22 according to the requirements of the M / G 20. For example, the power electronics can provide a three-phase alternating current for the M / G 20.

[0015] A transmission output shaft 30 can be connected to a differential 32. The differential 32 can drive a pair of wheels 34 via axles 36 connected to the differential 32. The differential 32 can transmit torque to each wheel 34 while allowing slight speed differences, such as when the vehicle 10 turns or corners.

[0016] Various types of differentials or similar devices can be used to distribute torque from the drivetrain to one or more wheels. In some applications, the torque distribution can vary depending on, for example, the specific operating mode or operating condition.

[0017] The transmission 16 can be configured as a multi-stage transmission using several friction elements for changing gear ratios. The transmission 16 can be configured to generate multiple forward and reverse gears via multiple gear elements in the gear train 28 of the transmission.

[0018] The gearbox 28 can contain several gear sets (not shown) which are selectively engaged in different gear stages by the selective engagement of friction elements, such as shift elements, including clutches with clutch elements and brakes (not shown). The different gear stages provided by the gear sets produce several gear ratios corresponding to different overall gearbox gear stages.

[0019] A control unit 40 may be provided and configured to control the friction elements of the transmission 16, in particular the gear set 28 of the transmission. The control unit 40 may be equipped with a transmission shift scheme. The transmission shift scheme may determine the operating conditions or the timing of gear changes of the transmission by engaging and / or disengaging friction elements of the gear sets in the gear set 28 of the transmission. The transmission shift scheme may determine the gear changes of the transmission based on vehicle acceleration, vehicle speed, engine speed, motor / generator speed, powertrain torque / power, or a driver request provided by an accelerator pedal 42, a brake pedal 44, or a gear selector.

[0020] The control unit 40 can be configured to specify the operating states of the vehicle 10 or the powertrain 12, in addition to the transmission shift patterns. In at least one embodiment, a larger control system can contain multiple control units. The individual control units or the control system can be influenced by various other control units throughout the vehicle 10 by operating a vehicle system controller (VSC) with a higher hierarchy over other subordinate control units. The VSC output can directly or indirectly specify or influence several vehicle functions, such as starting / stopping the engine 14, operating the motor / gear unit 20 to provide wheel torque or charge the traction battery 22, or starting the engine 14, selecting or scheduling transmission gear shifts, etc.

[0021] For example, the VSC can receive data from a transmission control module (TCM) that is directly connected to components of the transmission 16 and issue commands to it. Examples of other subordinate controllers that can operate lower in a control hierarchy compared to the VSC include a brake system control module (BSCM), a battery energy control module (BECM), and other controllers responsible for various vehicle functions. The VSC can also be used to verify data received from other controllers.

[0022] Any of the controllers mentioned above may contain a microprocessor or central processing unit (CPU) that interacts with various types of computer-readable storage devices or media. Computer-readable storage devices or media can include volatile and non-volatile storage in, for example, read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables while the CPU is powered off.The computer-readable storage devices or media can be implemented using any of a number of known storage devices, such as PROMs (programmable read-only memories), EPROMs (electrical PROMs), EEPROMs (electrically erasable PROMs), flash memory, or any other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which represent executable instructions used by the controller in controlling the power machine or vehicle.

[0023] The VSC and other controllers communicate with various power unit / vehicle sensors and actuators via an input / output interface (I / O interface). This interface can be implemented as a single integrated interface providing various raw data or signal conditioning, processing, and / or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips can be used to condition and process specific signals before they are fed to the CPU. The VSC can communicate signals to and / or from the TCM. Furthermore, as discussed above, the VSC can communicate with other vehicle controllers or directly with vehicle sensors and / or components, including the power unit 14 and the power electronics.

[0024] Although not explicitly shown, the average person will recognize various functions or components that can be controlled by the VSC within each of the subsystems listed above. Representative examples of parameters, systems, and / or components that can be actuated directly or indirectly using the control logic executed by the controller include fuel injection timing, rate, and duration; throttle position; spark plug ignition timing (in spark-ignition engines); intake / exhaust valve timing and duration; front-end accessory drive (FEAD) components, such as an alternator, air conditioning compressor, battery charging, regenerative braking, operation of a motor / gearbox (M / G), clutch pressures for the disconnect clutch 18, the torque converter lock-up clutch, and the transmission's gear train 28, and the like.

[0025] Representative examples of parameters, systems and / or components that can be actuated directly or indirectly using the control logic executed by the controller include fuel injection timing, rate and duration, throttle position, spark plug ignition timing (in spark-ignition engines), intake / exhaust valve timing and duration, front-end accessory drive (FEAD) components such as an alternator, an air conditioning compressor, battery charging, regenerative braking, operation of an M / G, clutch pressures for the disconnect clutch 18, the starting clutch and the gearbox gear 28, and the like.Sensors communicating input via the I / O interface can be used to indicate, for example, turbocharger boost pressure, crankshaft position (PIP), engine speed (RPM), wheel speeds (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), manifold absolute pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle valve position (TP), ambient air temperature (TPM), exhaust oxygen (EGO) or other exhaust component concentration or presence, intake airflow (MAF), transmission gear, ratio or mode, transmission oil temperature (TOT), transmission turbine speed (TS), torque converter lock-up clutch status (TCC), and deceleration or shift mode (MDE). The controller 40 can be equipped with control logic configured to operate the powertrain 12.The control logic can control the amount of torque supplied to the wheels 34 by controlling a gear ratio of the transmission between the transmission input shaft 24 and the transmission output shaft 30 based on driver requirements. The driver requirement can be a gear selection (PRNDL) input via a gear selector, accelerator pedal position input via an accelerator pedal 42, brake pedal position input via a brake pedal 44, traction battery temperature, traction battery voltage, traction battery current, and traction battery state of charge (SOC).

[0026] The control unit 40 can interpret the driver request from the accelerator pedal 42 to determine the driver's intention for a requested drivetrain torque or power to propel the vehicle 10. The control unit 40 can assign torque-splitting commands between the power unit 14 and / or the motor unit 20 to fulfill the driver request. In general, pressing and releasing the accelerator pedal 42 can generate an accelerator pedal position signal that can be interpreted by the control unit 40 as a request for increased power / increased torque or decreased power / decreased torque to propel the vehicle 10.

[0027] The controller 40 can interpret the driver request from the brake pedal 44 to determine the driver's intention to apply braking torque to reduce the vehicle speed or stop the vehicle 10. The controller 40 can assign the braking torque between a friction braking system 50 and the powertrain 12 by means of regenerative braking. In general, pressing and releasing the brake pedal 44 can generate a brake pedal position signal that the controller 40 can interpret as a request for braking torque or reduced power / torque to reduce the vehicle speed or stop the vehicle 10. Based at least on input from the accelerator pedal 42 or the brake pedal 44, the controller 40 can operate the powertrain 12 in various ways to fulfill the driver request.

[0028] The control unit 40 can be configured to operate the drive train 12 in a first mode. The disconnect clutch 18 can be at least partially engaged to operationally couple the power unit 14 with the M / G 20 while the drive train 12 is operating in first mode. The coupling can transmit a portion of the power unit torque through the disconnect clutch 18 to the M / G 20 and then from the M / G 20 through the torque converter 26 and the gearbox 28. Combustion in the power unit 14 can be activated or otherwise engaged during first mode.

[0029] The control unit 40 can issue commands to the power electronics so that, in the first mode, the M / G 20 can assist the power unit 14 by providing additional torque to the transmission input shaft 24. The control unit 40 can issue commands to assign a torque output from both the power unit 14 and the M / G 20, so that the combination of both torque outputs fulfills an input from the driver via an accelerator pedal 42. The first operating mode of the powertrain operation can be referred to as the "hybrid mode".

[0030] The control unit 40 can be configured to operate the powertrain 12 in a second mode. While the powertrain 12 is operating in the second mode, the disconnect clutch 18 can disconnect the power unit 14 from the rest of the powertrain 12. Combustion in the power unit 14 can be deactivated or otherwise switched off during the second mode to save fuel. The traction battery 22 can transfer stored electrical energy through the power electronics to the M / G 20, so that the M / G 20 acts as the sole power source for propelling the vehicle 10.

[0031] The control unit 40 can issue commands to the power electronics, activating the M / G 20 in the second mode to provide positive or negative torque to the transmission input shaft 24. The second powertrain operating mode, in which the M / G 20 is the sole drive unit, can be referred to as "electric mode".

[0032] The control unit 40 can be configured to operate the drivetrain in a third mode. The M / G 20 can be used to convert kinetic energy from the drivetrain 12 during braking events into electrical energy, which can be stored in the traction battery 22. The rotational energy of the M / G 20 from the rotation of the output shaft 38 by the gear train 28 of the transmission is converted into electrical energy for storage in the traction battery 22.

[0033] The control unit 40 can issue commands to the M / G 20 to selectively apply a drag or negative torque ("recuperation torque") and thus contribute to the vehicle's deceleration during a recuperation braking event. The third mode of powertrain operation, in which recuperation torque is applied, can also be referred to as "recuperation mode".

[0034] The M / G 20 can receive input torque from the wheels through the gearbox's gear train 28 and generate electricity to charge the traction battery 22 and recover energy that would otherwise be lost as heat during friction braking. The controller 40 can be configured to reduce the applied recuperative braking torque in response to the traction battery's state of charge falling below a threshold, a traction battery charging or discharging limit being exceeded, and / or a speed or torque limit of the M / G 20 being exceeded. The distribution of the wheel braking torque between friction braking torque and recuperative braking torque can be calculated and coordinated by the controller 40 to provide a target total braking torque to meet the driver's braking request.

[0035] Near the end of a recuperation braking event, when the vehicle 10 decelerates to a speed below a threshold or comes to a stop, the recuperation braking torque supplied by the M / G 20 can be transferred to the friction brake system 50 to avoid a torque spike when the torque converter lock-up clutch disengages.

[0036] The operating modes of the vehicle 10 or the powertrain 12, for example, hybrid mode, electric mode, recuperation mode, can have an associated transmission shift pattern that determines a suitable transmission ratio relating the vehicle speed and the rotational speed of the motor / gearbox 20. The transmission ratio can determine a relationship between vehicle speed and motor speed when the disconnect clutch 18 is engaged. The control unit 40 can schedule transmission shifts to optimize the rotational speeds of the motor / gearbox 20 and the motor 14 for the current operating mode. A transmission ratio can be selected that ensures the motor / gearbox 20 and the motor 14 can generate sufficient power when the power demand associated with an accelerator pedal position exceeds a threshold or when it is anticipated that it will soon become high.A transmission ratio can be selected that optimizes the efficiency of the M / G 20 and / or the motor 14 when the power demand associated with an accelerator pedal position is below a threshold or when it is expected to decrease soon. Different shift patterns can be used in hybrid, electric, or recuperation mode. The transmission shift pattern associated with recuperation mode, for example, when the driver applies the brakes to decelerate, can optimize the level of power recovered by the M / G 20 and supplied to the traction battery 22.

[0037] Fig. Figure 2 shows exemplary changes between transmission shift patterns. For example, while vehicle 10 is operating in hybrid mode with the M / G 20 coupled to the power unit 14 via the disconnect clutch 18, transmission shifts can be planned according to a hybrid mode shift pattern, as shown in block 70. Various conditions or events can lead to a change to a different operating mode with a different associated transmission shift pattern.For example, if the traction battery charge level increases above a threshold, a power demand is lower than a threshold, the position of an accelerator pedal 42 (or a change thereof) is greater than a threshold, or the position of a brake pedal 44 (or a change thereof) is lower than a threshold and a power demand is lower than a threshold, the control unit 40 can switch from hybrid mode to electric mode by releasing the disconnect clutch 18 at block 72 and stopping the motor 14. As another example, if the braking torque allocated to recuperation braking (as opposed to friction braking) exceeds a threshold, or the position of the brake pedal 44 (or a change thereof) is greater than a threshold, then the vehicle 10 can switch from hybrid mode to recuperation mode by releasing the disconnect clutch 18 at block 74 and stopping the motor 14.

[0038] For example, if the vehicle 10 is operating in electric mode while the power unit 14 is operationally disconnected from the M / G 20, gear selections can be planned according to an electric mode shift scheme, as shown in Block 76. The M / G 20 can be operated more efficiently at higher speeds compared to the power unit 14. The electric mode shift scheme can select a gear with a lower number (higher gear ratio) than the hybrid mode shift scheme. If the traction battery state of charge (SOC) falls below a threshold SOC during operation in electric mode, or if the position of an accelerator pedal 42 (or a change thereof) exceeds a threshold, the vehicle 10 can switch from electric mode to hybrid mode by starting the power unit 14 and engaging the disconnect clutch 18 at Block 78.If, in electric mode, the braking torque assigned to recuperation exceeds a threshold value, or if the position of a brake pedal 44 (or a change thereof) is greater than a threshold value, switching to recuperation mode may not change the operating state of the power unit 14 or the engagement state of the disconnect clutch 18. Scheduling for the transmission 16 can be performed according to a recuperation mode switching scheme, as shown in block 80, while the vehicle 10 is operating in recuperation mode. The vehicle 10 can switch from recuperation mode to electric mode while the vehicle speed falls below a threshold value, or if the position of a brake pedal 44 (or a change thereof) is greater than a threshold value.

[0039] Fig. Figure 3 represents an exemplary hybrid mode switching scheme for operating vehicle 10 in hybrid mode. Although the hybrid mode switching scheme of Fig. Figure 3 shows four forward gear stages; embodiments may employ different numbers of forward and reverse gear stages. The horizontal axis represents the vehicle speed, and the vertical axis represents the accelerator pedal position. The accelerator pedal position may represent power or torque requested by the driver. In some embodiments, the vertical axis may directly represent the driver request. When changing the current operating condition from the left side of line 82 to the right side of line 82, an upshift from 1st gear to 2nd gear may be planned. This may occur as a result of an increase in vehicle speed, a decrease in torque demand, a decrease in accelerator pedal position, or a combination of both.

[0040] When changing the operating condition from the right side of line 84 to the left side of line 84, a downshift from 2nd gear to 1st gear may be scheduled. These lines may be spaced apart to avoid overly frequent shifting between adjacent gears when the operating point varies near a shift transition line. Similarly, lines 86 and 88 control upshifts from 2nd gear to 3rd gear and downshifts from 3rd gear to 2nd gear, respectively. Lines 90 and 92 control upshifts from 3rd gear to 4th gear and downshifts from 4th gear to 3rd gear, respectively. Under low torque demand, the hybrid mode shift scheme tends to upshift as soon as the engine speed is above a minimum in the higher gear.When high torque is required, upshifts are delayed until the engine speed reaches its maximum or until the engine is capable of generating more power in a higher gear (lower gear ratio). The control strategy can include modifiers to account for parameters other than vehicle speed and torque demand, such as acceleration rate or battery charge level.

[0041] Fig. Figure 4 shows an exemplary electric mode shift diagram for operating vehicle 10 in electric mode. Lines 82', 86', and 90' control upshifts from 1st to 2nd, 2nd to 3rd, and 3rd to 4th gear, respectively. Similarly, lines 84', 88', and 92' control downshifts from 2nd to 1st, 3rd to 2nd, and 4th to 3rd gear, respectively. These lines are directed towards higher vehicle speeds than the corresponding lines in Figure 4. Fig. 3. This could be due to the increased efficiency of the M / G 20 at higher engine speeds, which makes lower-numbered gear ratios more desirable when the power unit 14 is disconnected from the M / G 20. When the vehicle 10 switches from hybrid mode to electric mode while operating at point 94, the vehicle 10 may, if no precautions are taken, shift from 3rd gear to 2nd gear. Since neither the pedal position nor the vehicle speed has changed, the driver may not expect the gear to shift.

[0042] During regenerative braking, a different switching pattern can be used. As in electric mode, the switching pattern for regenerative braking can be optimized to keep the M / G 20 operating at an efficient point. For example, the controller 40 can use the regenerative braking switching pattern to change gear, i.e., to downshift, as the M / G 20 approaches the M / G torque limit and the traction battery power limit with decreasing vehicle speed. Changing gear can increase the M / G torque as the M / G speed decreases, while maintaining a substantially constant traction battery output or M / G output power. Multiple shifts as the speed decreases to avoid bumping to the M / G 20's torque limit is sometimes referred to as "operating at the power limit" of the M / G 20 and / or the traction battery 22.During braking events, the controller 40 can determine the requested torque, which is negative, based on the position of a brake pedal 44, to reduce the vehicle speed. The controller 40 can allocate a portion of the requested torque to the friction braking system 50 and a portion to the powertrain 12. For example, the friction braking system 50 can be used more intensively when the traction battery charge level exceeds a threshold, or during traction control events that require very rapid changes in braking torque. The regenerative braking transmission shift scheme can control multi-stage downshifts, thus avoiding the need for multiple shifts to be executed in rapid succession when the vehicle deceleration rate exceeds a threshold.Since each shifting operation requires some time, single-stage shifting operations can result in an M / G speed that is lower than desired, even if they were performed in rapid succession.

[0043] Each transmission shift pattern assigned to a vehicle operating mode 10 can attempt to position the power unit 14 and / or the M / G 20 at the most efficient or optimal performance operating point for the operating conditions. Changes to the transmission shift pattern can occur automatically without intervention or selection by the driver. These changes can be based on the position or a change in position of the accelerator pedal 42 or the brake pedal 44, or they can be based on an energy management strategy. The energy management strategy can be controlled by the controller 40 and may involve decisions related to the power unit being switched off or on, the traction battery being charged or discharged, or powertrain loads.

[0044] The controller 40 can switch between transmission shift patterns by performing a look-ahead function. Based on current operating conditions, the controller 40 can anticipate a new transmission shift pattern to determine the desired gear ratio. Using the target gear ratio associated with the new shift pattern and the actual gear ratio associated with the current shift pattern, the look-ahead function attempts to make decisions to switch between the transmission shift patterns. The controller 40 can switch to the new transmission shift pattern if the target gear ratio associated with the new shift pattern is substantially similar to or equal to the actual gear ratio associated with the current shift pattern.Control unit 40 can remain in the current transmission shift pattern and switch to the target transmission gear stage if the target transmission gear stage assigned to the new transmission shift pattern is not the same as, or different from, the actual transmission gear stage assigned to the current transmission shift pattern. The transmission gear stage change can be delayed until after the transmission shift pattern change from the current to the new transmission shift pattern, based on the accelerator pedal position and / or brake pedal position.

[0045] The control unit 40 can operate the vehicle 10 according to the current transmission shift pattern, at least until a driver event occurs, such as a change in accelerator pedal position or a change in brake pedal position that exceeds a predefined threshold. This allows transmission gear changes to be mitigated or prevented to improve passenger comfort, even when the operating mode of the vehicle 10 or powertrain 12 changes.

[0046] Fig. 5A and Fig.5B are flowcharts that show a procedure for controlling a vehicle. At block 100, the vehicle 10 can be operated in a first mode at an actual gear position according to a first shift pattern. At block 102, the procedure can determine whether a request to operate the vehicle 10 in a second mode has been received, which may be associated with an accelerator pedal tip-out following an accelerator pedal tip-in. The accelerator pedal tip-out following the accelerator pedal tip-in may indicate that an operator of the vehicle 10 desired aggressive acceleration of the vehicle and that the operator released the accelerator pedal 42 when approaching or reaching a target vehicle speed in order to avoid exceeding or falling below the target vehicle speed.In at least one embodiment, accelerator pedal tip-out may not be associated with the request to operate the vehicle 10 in the second mode, and the transition from the first mode to the second mode may be controlled asynchronously. The transition from the first mode to the second mode may be controlled asynchronously in response to a traction battery charge exceeding a threshold traction battery charge level, or another powertrain parameter indicating that operation of the power unit 14 may not be necessary to meet driver requirements. In response to the request, the method may anticipate a new gear stage according to a second shift pattern associated with the second mode.If the new gear position according to the second shift pattern associated with the second mode is the same as, or substantially similar to, the current gear position according to the first shift pattern associated with the first mode, the procedure can continue with block 104. If the new gear position according to the second shift pattern associated with the second mode differs from the current gear position according to the first shift pattern associated with the first mode, the procedure can end. At the end of the procedure, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the first mode.

[0047] In block 104, the procedure can maintain the current gear and operate the vehicle 10 in the current gear according to the second shift pattern associated with the second mode. The procedure can operate the vehicle 10 in the current gear according to the second shift pattern during the transition from the first mode to the second mode and thereafter, provided that the traction battery charge level is greater than a threshold, the vehicle speed decrease is less than a threshold decrease, and the accelerator pedal position falls within a predetermined range. The transmission 16 cannot shift out of the current gear while the vehicle speed remains substantially constant, the traction battery charge level remains greater than a threshold, and the accelerator pedal position remains substantially constant or within the predetermined range.In at least one embodiment, the transmission 16 cannot shift out of the current gear position, at least until a vehicle condition changes, for example until an accelerator pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0048] In block 106, the method can determine whether a request to operate the vehicle 10 in a third mode, which may be associated with a brake pedal tip-in of less than a threshold, has been received. In at least one embodiment, the method can determine whether a request to operate the vehicle 10 in a third mode, which may be associated with a brake pedal tip-out of less than a threshold following a brake pedal tip-in of more than a threshold, sometimes referred to as "abrupt application of the brake," has been received. The brake pedal tip-out following the brake pedal tip-in may indicate that an operator of the vehicle 10 desired aggressive deceleration of the vehicle, and that the operator released the brake pedal 44 when approaching or reaching a target vehicle speed in order to avoid exceeding or falling below the target vehicle speed.In response to the request, the procedure can anticipate a new gear position according to a third shift pattern associated with the third mode. If the new gear position according to the third shift pattern associated with the third mode is the same as, or substantially similar to, the current gear position according to the second shift pattern associated with the second mode, the procedure can proceed to block 108. If the new gear position according to the third shift pattern associated with the third mode differs from the current gear position according to the second shift pattern associated with the second mode, the procedure can terminate. Upon termination of the procedure, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the second mode.

[0049] In block 108, the procedure can maintain the current gear and operate the vehicle 10 in the current gear according to the third shift pattern associated with the third mode. The procedure can continue to operate the vehicle 10 in the current gear according to the third shift pattern during the transition from the second to the third mode and thereafter, as long as the traction battery charge level is below a threshold and the brake pedal position remains within a predetermined range. The transmission 16 cannot shift out of the current gear while the traction battery charge level remains below a threshold and the brake pedal position remains substantially constant or within the predetermined range.In at least one embodiment, the transmission 16 cannot shift out of the current gear position, at least until a vehicle condition changes, for example until a brake pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0050] Referring again to block 104, the procedure can anticipate further inputs while the vehicle 10 is operating in the second mode with an actual gear according to a second shift pattern. At block 110, the procedure can determine if there is a request to operate the vehicle 10 in the first mode, associated with a brake pedal tip-out above a threshold or an accelerator pedal tip-in above a threshold. In response to the request, the procedure can anticipate a new gear according to the first shift pattern associated with the first mode. If the new gear according to the first shift pattern associated with the first mode is the same as, or substantially similar to, the actual gear according to the second shift pattern associated with the second mode, the procedure can proceed to block 112.If the new gear position according to the first shift pattern associated with the first mode differs from the current gear position according to the second shift pattern associated with the second mode, the procedure can end. Once the procedure is complete, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the second mode.

[0051] In block 112, the procedure can maintain the current gear and operate the vehicle 10 in the current gear according to the first shift pattern associated with the first mode. The procedure can operate the vehicle 10 in the current gear according to the first shift pattern during the change from the second mode to the first mode and thereafter, as long as the accelerator pedal position or brake pedal position remains within a predetermined range. The transmission 16 cannot shift out of the current gear while the accelerator pedal position or brake pedal position remains substantially constant or within a predetermined range.In at least one embodiment, the transmission 16 cannot shift out of the current gear position, at least until a vehicle state changes, for example until an accelerator pedal position or a brake pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0052] Referring again to block 100, the procedure can anticipate further inputs while the vehicle 10 is operating in the first mode with an actual gear according to a first shift pattern. At block 114, the procedure can determine whether there is a request to operate the vehicle 10 in a third mode, associated with a brake pedal tip-in of less than a threshold. In response to the request, the procedure can anticipate a new gear according to the third shift pattern associated with the third mode. If the new gear according to the third shift pattern associated with the third mode is the same as, or substantially similar to, the actual gear according to the first shift pattern associated with the first mode, the procedure can proceed to block 116.If the new gear position, according to the third shift pattern associated with the third mode, differs from the current gear position, according to the first shift pattern associated with the first mode, the procedure can be terminated. Upon termination of the procedure, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the second mode.

[0053] In block 116, the method can maintain the current gear and operate the vehicle 10 in the current gear according to the third shift pattern associated with the third mode. The method can operate the vehicle 10 in the current gear according to the third shift pattern during the transition from the first mode to the third mode and thereafter, while a brake pedal position remains within a predetermined range. The transmission 16 cannot shift out of the current gear while the brake pedal position remains substantially constant or within the predetermined range. In at least one embodiment, the transmission 16 cannot shift out of the current gear at least until a vehicle condition changes, for example, until a brake pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0054] In block 118, the method can determine whether a request to operate the vehicle 10 in a second mode, which may involve a brake pedal tip-out or an accelerator pedal tip-in below a threshold, has been received. In at least one embodiment, the method can determine whether a request to operate the vehicle 10 in a second mode, which may involve a brake pedal tip-in above a threshold following a brake pedal tip-in below a threshold, sometimes referred to as "soft braking", has been received.A brake pedal tap-in above a threshold following a brake pedal tap-in below a threshold may indicate that an operator of vehicle 10 desired gradual deceleration of the vehicle and, to assist in reaching a target vehicle speed, increased the degree of brake pedal depressurization. In response to this request, the procedure may anticipate a new gear according to a second shift pattern associated with the second mode. If the new gear according to the second shift pattern associated with the second mode is equal to or substantially similar to the current gear according to the third shift pattern associated with the third mode, the procedure may proceed to block 120.If the new gear position, according to the third shift pattern associated with the third mode, differs from the current gear position, according to the second shift pattern associated with the second mode, the procedure can end. Once the procedure is complete, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the second mode.

[0055] In block 120, the procedure can maintain the current gear and operate vehicle 10 in the current gear according to the second shift pattern associated with the second mode. The procedure can continue to operate vehicle 10 in the current gear according to the second shift pattern during the transition from the third mode to the second mode and thereafter, as long as the traction battery charge level is above a threshold and the brake pedal position or accelerator pedal position remains within a predetermined range. The transmission 16 cannot shift out of the current gear while the traction battery charge level is above a threshold and the brake pedal position or accelerator pedal position remains within a predetermined range.In at least one embodiment, the transmission 16 cannot shift out of the current gear position, at least until a vehicle state changes, for example until an accelerator pedal position or a brake pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0056] Referring again to block 116, the procedure can anticipate further inputs while the vehicle 10 is operating in the third mode with an actual gear according to a third shift pattern. At block 122, the procedure can determine whether there is a request to operate the vehicle 10 in the first mode, associated with a brake pedal tip-in above a threshold. In response to the request, the procedure can anticipate a new gear according to the first shift pattern associated with the first mode. If the new gear according to the first shift pattern associated with the first mode is the same as, or substantially similar to, the actual gear according to the third shift pattern associated with the third mode, the procedure can proceed to block 124.If the new gear position, according to the first shift pattern associated with the first mode, differs from the current gear position, according to the third shift pattern associated with the third mode, the procedure can be terminated. Upon termination of the procedure, the gear position can be changed from the current gear position to the new gear position while the vehicle continues to operate in the third mode.

[0057] In block 124, the method can maintain the current gear and operate the vehicle 10 in the current gear according to the first shift pattern associated with the first mode. The method can operate the vehicle 10 in the current gear according to the first shift pattern during the change from the third mode to the first mode and thereafter, while the accelerator pedal position remains within a predetermined range. The transmission 16 cannot shift out of the current gear while the accelerator pedal position remains substantially constant or within the predetermined range. In at least one embodiment, the transmission 16 cannot shift out of the current gear at least until a vehicle condition changes, for example, until the accelerator pedal position changes, the traction battery charge level changes, or the vehicle speed changes.

[0058] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Instead, the terms used in the description serve to describe rather than to limit the scope, and it is understood that various modifications can be made without departing from the concept and scope of the invention. Furthermore, the features of different implementation embodiments can be combined to form further embodiments of the invention.

[0059] It is further described as follows: A. Vehicle, including: a power machine; a transmission configured for selective coupling with the power unit; and A control system programmed to control the transmission to maintain an existing gear after decoupling the motor from the transmission, in response to a request to decouple the motor from the transmission received while the traction battery state of charge (SOC) is greater than a threshold SOC, a reduction in vehicle speed below a threshold reduction, and an accelerator pedal position within a predetermined range, so that the transmission does not shift after decoupling the motor from the transmission while the vehicle speed remains essentially constant and the SOC remains greater than the threshold SOC. B. Vehicle according to A, wherein the control is further programmed to delay a shift of the transmission into a new gear stage, at least until a brake pedal position changes by more than a predefined amount, while the engine remains decoupled from the transmission. C. Vehicle according to B, wherein the control is further programmed to control the transmission to maintain the current gear stage in response to a reduction in the brake pedal position. D. Vehicle according to A, wherein the control is further programmed to control the transmission to maintain the current gear stage in response to a request to decouple the engine from the transmission and to increase the brake pedal position above a threshold, so that the transmission does not shift after the engine has been decoupled from the transmission, at least until a brake pedal position changes. E. Vehicle to A, wherein the control is further programmed to, in response to a request to disengage the engine from the transmission, which is received while the SOC is below the threshold SOC, and to a reduction in vehicle speed from below the threshold reduction, control the transmission to shift into a new gear and control the transmission to maintain coupling with the engine. F. Vehicle according to A, wherein the control is further programmed to control the transmission to maintain the current gear stage in response to a request to couple the engine with the transmission and to an increase in the accelerator pedal position above the threshold, so that the transmission does not shift after the engine has been coupled with the transmission, at least until an accelerator pedal position changes. G. Vehicle, including: a controller that is programmed to to operate a powertrain in hybrid mode; and In response to a request to operate the powertrain in electric mode, the powertrain operation will switch from hybrid mode to electric mode without shifting gears until a change in the accelerator pedal position exceeds a threshold after the switch. H. Vehicle according to G, wherein the control is further programmed to switch the powertrain operation from electric mode to recuperation mode in response to a request to operate the powertrain in a recuperation mode and to a brake pedal tip-in while the powertrain is operating in electric mode, without shifting gears, until a change in the brake pedal position exceeds a threshold value after the switch. I. Vehicle according to H, wherein the control is further programmed to switch the powertrain operation from recuperation mode to hybrid mode in response to a request to operate the powertrain in hybrid mode and to a brake pedal tip-out while the powertrain is operating in recuperation mode, without shifting gears, until a change in a brake pedal position and / or an accelerator pedal position exceeds a threshold value after the switch. J. Vehicle according to H, wherein the control is further programmed to switch the powertrain operation from electric mode to hybrid mode without shifting gears in response to a request to operate the powertrain in hybrid mode and to an accelerator pedal tip-in greater than a threshold while the powertrain is operating in electric mode, until a change in the accelerator pedal position exceeds a threshold after the switch. K. Vehicle according to H, wherein the control is further programmed to switch the powertrain operation from recuperation mode to electric mode without shifting gears in response to a request to operate the powertrain in electric mode and to a brake pedal tip-out while the powertrain is operating in recuperation mode, until a change in the brake pedal position exceeds a threshold value after the switch. L. Vehicle to H, wherein the control is further programmed to switch the powertrain operation from recuperation mode to electric mode in response to a request to operate the powertrain in electric mode and to an accelerator pedal tip-in while the powertrain is operating in recuperation mode, without shifting gears, until a change in the accelerator pedal position exceeds a threshold value after the switch. M. Method for controlling a powertrain, comprising: Operating the powertrain in a hybrid mode while in first gear; and in response to a request to operate the powertrain in an electric mode associated with an accelerator pedal tip-out, while a traction battery state of charge (SOC) is greater than a threshold SOC, to switch the operation of the powertrain from hybrid mode to electric mode while maintaining first gear until an accelerator pedal position changes. N. Method according to M, further comprising, in response to a request to operate the powertrain in a recuperation mode associated with a brake pedal tip-in of less than a threshold, while the powertrain is operated in hybrid mode with the first gear stage, switching the operation of the powertrain from hybrid mode to recuperation mode while maintaining the first gear stage until a brake pedal position changes. O. Method according to N, further comprising, in response to a request to operate the powertrain in hybrid mode, which is associated with a brake pedal tip-out of below a threshold, while the powertrain is operated in recuperation mode with the third gear stage, switching the operation of the powertrain from hybrid mode to recuperation mode while maintaining the third gear stage until a brake pedal position changes. P. Method according to N, further comprising, in response to a request to operate the powertrain in hybrid mode associated with an accelerator pedal tip-in of above a threshold, while the powertrain is operated in recuperation mode with a third gear stage, switching the operation of the powertrain from recuperation mode to hybrid mode while maintaining the third gear stage until an accelerator pedal position changes. Q. Method according to N, further comprising, in response to a request to operate the powertrain in a recuperation mode associated with a brake pedal tip-in of less than a threshold, while the powertrain is operated in electric mode with a second gear stage, switching the operation of the powertrain from electric mode to recuperation mode while maintaining the second gear stage until a brake pedal position changes.

Claims

[1] Vehicle (10), comprising: a controller (40) which is programmed to to operate a powertrain (12) in hybrid mode; and in response to a request to operate the powertrain (12) in electric mode, to switch the powertrain operation from hybrid mode to electric mode without shifting gears until a change in the accelerator pedal position exceeds a threshold value after the switch, wherein the control unit (40) is further programmed to switch the powertrain operation from electric mode to recuperation mode in response to a request to operate the powertrain (12) in a recuperation mode and to a brake pedal tip-in while the powertrain (12) is operating in electric mode, without shifting gears, until a change in the brake pedal position exceeds a threshold value after the switch. [2] Vehicle (10) according to claim 1, wherein the control unit (40) is further programmed to switch the powertrain operation from recuperation mode to hybrid mode in response to a request to operate the powertrain (12) in hybrid mode and to a brake pedal tip-out while the powertrain (12) is operating in recuperation mode, without shifting gears, until a change in a brake pedal position and / or an accelerator pedal position exceeds a threshold value after the switch. [3] Vehicle (10) according to claim 1, wherein the control unit (40) is further programmed to switch the powertrain operation from electric mode to hybrid mode in response to a request to operate the powertrain (12) in hybrid mode and to an accelerator pedal tip-in greater than a threshold value while the powertrain (12) is operating in electric mode, without shifting gears until a change in the accelerator pedal position exceeds a threshold value after the switch. [4] Vehicle (10) according to claim 1, wherein the control unit (40) is further programmed to switch the powertrain operation from recuperation mode to electric mode in response to a request to operate the powertrain (12) in electric mode and to a brake pedal tip-out while the powertrain (12) is operating in recuperation mode, without shifting gears, until a change in the brake pedal position exceeds a threshold value after the switch. [5] Vehicle (10) according to claim 1, wherein the control unit (40) is further programmed to switch the powertrain operation from recuperation mode to electric mode in response to a request to operate the powertrain (12) in electric mode and to an accelerator pedal tip-in while the powertrain (12) is operating in recuperation mode, without shifting gears, until a change in the accelerator pedal position exceeds a threshold value after the switch.

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