Method and system for starting a hybrid vehicle

Abstract

The present disclosure describes a system and method for launching a hybrid vehicle including a motor / generator and an automatic transmission with a torque converter. The system and method can allow for increased vehicle acceleration to enhance hybrid vehicle performance during specific vehicle launch conditions. Launch conditions can be established based on brake pedal position and accelerator pedal position.

Description

Technical Field

[0001] The present invention relates to a method and system for operating a powertrain system of a hybrid vehicle. The method and system may be particularly useful for hybrid vehicles that emphasize performance. Background Art

[0002] Hybrid vehicles can save fuel and reduce greenhouse gases by using electric motors to provide propulsion. This feature may be well known, but hybrid vehicles can also provide performance advantages. For example, the torque of the motor can be combined with the torque of the internal combustion engine to provide a powertrain output and vehicle acceleration. The torque from the motor and the torque from the internal combustion engine can be input to the transmission or combined by the transmission and supplied to the vehicle wheels. If the internal combustion engine and the motor provide enough torque to make the wheels of the vehicle slip, the vehicle may not accelerate as fast as expected. In addition, the amount of torque required to produce wheel slip can be changed based on road surface, tires, and surrounding climate conditions. On the contrary, if the vehicle driver requests a higher vehicle acceleration rate, and the torque delivered to the wheels is less than the torque required to meet the higher vehicle acceleration rate, the vehicle may not run well. Therefore, it may be desirable to provide a method for starting a vehicle that provides a desired vehicle acceleration level without wasting energy to rotate the wheels. Summary of the invention

[0003] The inventors herein have recognized the above-identified problems and have developed a method of vehicle operation that includes adjusting the speed of a torque converter impeller from a first speed to a second speed in response to simultaneous application of a brake pedal and an accelerator pedal.

[0004] The start of a hybrid vehicle can be improved by adjusting the speed of the torque converter impeller before the vehicle starts in response to the simultaneous application of the brake pedal and the accelerator pedal. In particular, before the vehicle starts, the torque converter impeller speed can be adjusted to the stall speed of the torque converter, or alternatively adjusted to the speed at which the combined engine torque and motor torque are at a maximum, so that the time spent on transmitting the powertrain torque to the wheels can be shortened. In addition, the engine speed can be adjusted before starting so that the engine speed is the speed at which the engine torque can be maximized. Therefore, a larger amount of powertrain torque can be transmitted to the wheels faster to increase vehicle acceleration. If wheel slip is experienced during vehicle start-up, the motor can convert a portion of the engine output torque into electricity, thereby reducing the amount of power lost by wheel slip. Conversely, if the engine torque is not sufficient to cause wheel slip, the motor can increase the wheel torque, thereby approaching wheel slip and increasing vehicle acceleration.

[0005] According to the present invention, there is provided a vehicle operation method, the method comprising:

[0006] In response to the simultaneous application of the brake pedal and the accelerator pedal, the speed of the torque converter impeller is adjusted from the first speed to a second predetermined speed.

[0007] According to one embodiment of the present invention, the second predetermined speed in the method is a speed at which the engine and the motor are able to provide a combined first torque, which is greater than the combined torque that the engine and the motor can output when running at any speed different from the second speed.

[0008] According to one embodiment of the present invention, in the method, the second predetermined rotation speed is a function of the braking torque of the drive wheel, and the method further comprises:

[0009] The engine is started in response to the brake pedal and the accelerator pedal being simultaneously applied.

[0010] According to an embodiment of the present invention, the method further comprises adjusting the torque of the engine and the torque of the motor after starting the engine so that the torque converter impeller rotates at a second predetermined speed.

[0011] According to an embodiment of the invention, the method adjusts the torque of the engine and the torque of the electric machine in response to the battery state of charge.

[0012] According to an embodiment of the present invention, in the method, the first rotation speed is a rotation speed of the pump, and when the rotation speed is equal to or greater than the rotation speed of the pump, the pump provides a hydraulic line pressure greater than a threshold pressure.

[0013] According to one embodiment of the present invention, the method wherein the threshold pressure is a pressure sufficient to fully engage the transmission clutch.

[0014] The present description may provide several advantages. Specifically, the method may improve vehicle acceleration during a high-performance vehicle launch (e.g., acceleration from zero speed of the vehicle to a torque converter impeller speed within a threshold speed of the torque converter turbine speed). Additionally, the method may improve vehicle efficiency during a high-performance vehicle launch. Furthermore, the method may provide an optimal amount of wheel slip.

[0015] The above and other advantages, and features of the present invention will become apparent from the following detailed description alone or in conjunction with the accompanying drawings.

[0016] It should be understood that the above summary is provided to introduce selected concepts further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that address any disadvantages mentioned above or in any part of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The advantages described herein will be more fully understood by reading the exemplary embodiments, referred to herein as detailed description, either alone or with reference to the accompanying drawings, in which:

[0018] Figure 1 It is a schematic diagram of the engine;

[0019] Figure 2 is a schematic diagram of a powertrain system of a hybrid vehicle;

[0020] Figure 3 a graph showing an exemplary desired torque converter impeller speed;

[0021] Figure 4 shows the anticipated vehicle launch sequence; and

[0022] Figure 5 is a flow chart of a method for operating a powertrain or driveline of a hybrid vehicle. DETAILED DESCRIPTION

[0023] This embodiment is related to improving the starting of a hybrid vehicle. Figure 1 As shown, a hybrid vehicle may include an engine. Figure 1 The engine may be included in Figure 2 The power transmission system can be as shown in FIG. Figure 3 The speed shown is used to make the hybrid vehicle run as follows Figure 4 The operating timing of the prior art is Figure 4 The powertrain system can be based on Figure 5 to run the method shown in .

[0024] refer to Figure 1 Internal combustion engine 10, comprising a plurality of cylinders, is controlled by electronic engine controller 12, wherein one cylinder is Figure 1. The engine 10 is composed of a cylinder head 35 and a cylinder block 33, which includes a combustion chamber 30 and a cylinder wall 32. The piston 36 is disposed in the cylinder block 33 and reciprocates through a connection connected to the crankshaft 40. A flywheel 97 and a ring gear 99 are connected to the crankshaft 40. A starter 96 (e.g., a low voltage (operating at a voltage of less than 30 volts) motor) includes a pinion shaft 98 and a pinion 95. The pinion shaft 98 can selectively advance the pinion 95 to engage the ring gear 99. The starter 96 can be mounted directly to the front of the engine or the rear of the engine. In some examples, the starter 96 can selectively supply torque to the crankshaft 40 via a belt or chain. In one example, the starter 96 is in a basic state when not engaged to the engine crankshaft. The combustion chamber 30B is shown as being connected to the intake manifold 44B and the exhaust manifold 48B via corresponding intake valves 52 and exhaust valves 54. Each intake valve and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. The position of the intake cam 51 may be determined by an intake cam sensor 55. The position of the exhaust cam 53 may be determined by an exhaust cam sensor 57. The intake valve 52 may be selectively activated and deactivated by a valve actuation device 59. The exhaust valve 54 may be selectively activated and deactivated by a valve actuation device 58. The valve actuations 58 and 59 may be electromechanical devices.

[0025] Fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a high pressure dual stage fuel system may be used to generate higher fuel pressures.

[0026] In addition, the intake manifold 44 is shown to be in communication with the turbocharger compressor 162 and the engine air intake 42. In other examples, the compressor 162 may be a supercharger compressor. The shaft 161 mechanically connects the turbocharger turbine 164 to the turbocharger compressor 162. The optional electronic throttle 62 adjusts the position of the throttle plate 64 to control the air flow from the compressor 162 to the intake manifold 44. The pressure in the boost chamber 45 may be referred to as the throttle inlet pressure, because the inlet of the throttle 62 is located in the boost chamber 45. The throttle outlet is located in the intake manifold 44. In some examples, the throttle 62 and the throttle plate 64 may be disposed between the intake valve 52 and the intake manifold 44, so that the throttle 62 is an intake port throttle. The compressor recirculation valve 47 may be selectively adjusted to a plurality of positions between fully open and fully closed. Wastegate 163 may be adjusted via controller 12 to allow exhaust gases to selectively bypass turbine 164 to control the speed of compressor 162. Air filter 43 cleans air entering engine air intake 42.

[0027] Distributorless ignition system 88 provides an ignition spark to combustion chamber 30 via spark plug 92 in response to controller 12. Universal or wide-area exhaust gas oxygen (UEGO) sensor 126 is shown coupled to exhaust manifold 48 upstream of catalytic converter 70. Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor 126.

[0028] In one example, converter 70 may include multiple catalyst bricks. In another example, multiple emission control devices, each having multiple bricks, may be used. In one example, converter 70 may be a three-way type catalyst.

[0029] The controller 12 Figure 11 is shown as a conventional microcomputer including: a microprocessor unit (CPU) 102, input / output ports (I / O) 104, read-only memory (ROM) 106 (e.g., non-volatile memory), random access memory (RAM) 108, keep-alive memory (KAM) 110, and a conventional data bus. Controller 12 is shown receiving various signals from sensors connected to engine 10, including, in addition to those previously discussed, engine coolant temperature (ECT) from temperature sensor 112 connected to cooling sleeve 114; force applied by person 132 sensed by position sensor 134 connected to accelerator pedal 130; force applied by person 152 sensed by position sensor 154 connected to brake pedal 150; measurement of engine manifold pressure (MAP) from pressure sensor 122 connected to intake manifold 44; position of crankshaft 40 sensed by engine position sensor 118B; measurement of air mass entering the engine from sensor 120; and measurement of throttle position from sensor 68. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses per revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0030] During operation, each cylinder within engine 10 typically undergoes a four stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Generally, during the intake stroke, exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44, and piston 36 moves to the bottom of the cylinder to increase the volume within combustion chamber 30. The position of piston 36 near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber 30 is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC).

[0031] During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber 30 is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means (e.g., spark plug 92) to cause combustion.

[0032] During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts the piston motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown only as an example, and the intake and exhaust valve opening and / or closing timings may be varied to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0033] Figure 2 is a block diagram of a vehicle 225 including a powertrain 200 . Figure 2 The powertrain system includes Figure 1 The engine 10 shown. The powertrain system 200 is shown to include a vehicle system controller 255, an engine controller 12, a motor controller 252, a transmission controller 254, and a brake controller 250. The controllers can communicate via a controller area network (CAN) 299. Each controller can provide information to other controllers, such as torque output limits (e.g., torque output of a controlled device or component that is not exceeded), torque input limits (e.g., torque input of a controlled device or component that is not exceeded), sensor and actuator data, diagnostic information (e.g., information about a degraded transmission, information about a degraded engine, information about a degraded motor, information about a degraded brake). In addition, the vehicle system controller 225 can provide commands to the engine controller 12, the motor controller 252, the transmission controller 254, and the brake controller 141 to implement driver input requests and other requests based on vehicle operating conditions.

[0034] For example, the vehicle system controller 255 may request a desired wheel torque in response to the driver releasing the accelerator pedal and the vehicle speed decreasing to provide a desired vehicle deceleration rate. The desired wheel torque may be provided by the vehicle system controller requesting a first braking torque from the motor controller 252 and a second braking torque from the brake controller 250, the first torque and the second torque providing the desired braking torque at the vehicle wheels 216.

[0035] In other examples, the division of control of the powertrain devices may be different from Figure 2 For example, a single controller may replace vehicle system controller 255 , engine controller 12 , motor controller 252 , transmission controller 254 , and brake controller 250 .

[0036] In this example, powertrain 200 may be powered by engine 10 and motor 240. In other examples, engine 10 may be omitted. Figure 1The engine 10 may be started by the engine starting system shown, or via an integrated starter / generator (ISG) 240. ISG 240 (e.g., a high voltage (operating with a voltage greater than 30 volts) electric machine) may also be referred to as an electric machine, a motor, and / or a generator. In addition, the torque of engine 10 may be regulated via torque actuator 204 (e.g., a fuel injector, a throttle, etc.).

[0037] The engine output torque can be transmitted through the dual mass flywheel 215 to the input side of the powertrain disconnect clutch 236. The disconnect clutch 236 can be electrically or hydraulically actuated. The downstream side of the disconnect clutch 236 is shown as being mechanically connected to the input shaft 237 of the ISG.

[0038] ISG 240 may be operated to provide torque to powertrain 200 or, in a regenerative mode, convert powertrain torque to electrical energy for storage in electrical energy storage device 275. ISG 240 has a Figure 1 96 shown in the figure. In addition, the ISG 240 directly drives the powertrain 200 or is directly driven by the powertrain 200. The ISG 240 is not connected to the powertrain 200 by a belt, gear, or chain. Instead, the ISG 240 rotates at the same rate as the powertrain 200. The energy storage device 275 (e.g., a high voltage battery or power source) can be a battery, a capacitor, or an inductor. The downstream side of the ISG 240 is mechanically connected to the impeller 285 of the torque converter 206 via the shaft 241. The upstream side of the ISG 240 is mechanically connected to the disconnect clutch 236. The ISG 240 can provide positive torque or negative torque to the powertrain 200 by operating as a motor or a generator according to the instructions of the motor controller 252.

[0039] The torque converter 206 includes a turbine 286 for outputting torque to an input shaft 270. The input shaft 270 mechanically connects the torque converter 206 to the automatic transmission 208. The torque converter 206 also includes a torque converter bypass lockup clutch 212 (TCC). When the TCC is locked, torque is directly transferred from the impeller 285 to the turbine 286. The TCC is electrically operated by the controller 12. Alternatively, the TCC can be hydraulically locked. In one example, the torque converter can be referred to as a component of the transmission.

[0040] When the torque converter lockup clutch 212 is fully disengaged, the torque converter 206 transmits the engine torque to the automatic transmission 208 via the fluid transmitted between the torque converter turbine 286 and the torque converter impeller 285, thereby achieving torque multiplication. Conversely, when the torque converter lockup clutch 212 is fully engaged, the engine output torque is directly transmitted to the input shaft (not shown) of the transmission 208 through the torque converter clutch. Alternatively, the torque converter lockup clutch 212 can be partially engaged, so that the amount of torque directly transmitted to the transmission can be adjusted. The controller 12 can be configured to adjust the amount of torque transmitted by the torque converter 212 by adjusting the torque converter lockup clutch in response to various engine operating conditions or based on the engine operation request based on the driver.

[0041] The automatic transmission 208 includes a gear clutch (e.g., gears 1-10) 211 and a forward clutch 210. The automatic transmission 208 is a fixed gear ratio transmission. The gear clutch 211 and the forward clutch 210 can be selectively engaged to change the ratio of the actual total number of revolutions of the input shaft 270 to the actual total number of revolutions of the wheel 216. The gear clutch 211 can be engaged or disengaged by adjusting the supply to the clutch fluid via the shift control solenoid valve 209. The torque output of the automatic transmission 208 can also be relayed to the wheel 216 to propel the vehicle through the output shaft 260. Specifically, the automatic transmission 208 can transmit the input drive torque at the input shaft 270 in response to the vehicle driving conditions before the output drive torque is transmitted to the wheel 216. The transmission controller 254 selectively activates or engages the TCC 212, the gear clutch 211, and the forward clutch 210. The transmission controller also selectively deactivates or disengages the TCC 212, the gear clutch 211, and the forward clutch 210.

[0042] In addition, frictional forces may be applied to wheels 216 by engaging friction wheel brakes 218. In one example, friction wheel brakes 218 may be engaged in response to the driver placing his foot on a brake pedal (not shown) and / or in response to instructions within brake controller 250. In addition, brake controller 250 may apply brakes 218 in response to information and / or requests made by vehicle system controller 255. In the same manner, frictional forces applied to wheels 216 may be reduced by disengaging wheel brakes 218 in response to the driver releasing his foot from the brake pedal, brake controller instructions, and / or vehicle system controller instructions and / or information. For example, vehicle brakes may apply frictional forces to wheels 216 via controller 250 as part of an automatic engine stop process.

[0043] The vehicle system controller may obtain the driver demand torque from the accelerator pedal or other device in response to a request to accelerate the vehicle 225. The vehicle system controller 255 then distributes a portion of the requested driver demand torque to the engine and the remaining portion to the ISG. The vehicle system controller 255 requests the engine torque from the engine controller 12 and the ISG torque from the motor controller 252. If the ISG torque plus the engine torque is less than the transmission input torque limit (e.g., a threshold that is not exceeded), the torque is transmitted to the torque converter 206, which then relays at least a portion of the requested torque to the transmission input shaft 270. The transmission controller 254 selectively locks the torque converter clutch 212 and engages the gear via the gear clutch 211 in response to a shift schedule and a TCC lock schedule that may be based on the input shaft torque and vehicle speed. In some cases, when people may want to charge the electrical energy storage device 275, a charging torque (e.g., a negative ISG torque) may be requested while there is a non-zero driver demand torque. The vehicle system controller 255 may request increased engine torque to overcome the charging torque to meet the driver demand torque.

[0044] The vehicle system controller may provide a negative desired wheel torque based on the vehicle speed and brake pedal position in response to a request to decelerate the vehicle 225 and provide regenerative braking. The vehicle system controller 255 then allocates a portion of the negative desired wheel torque to the ISG 240 (e.g., desired powertrain wheel torque) and the remainder to the friction brake 218 (e.g., desired friction brake wheel torque). In addition, the vehicle system controller may notify the transmission controller 254 that the vehicle is in regenerative braking mode, so that the transmission controller 254 changes gears based on a unique shift schedule to improve regeneration efficiency. The ISG 240 supplies negative torque to the transmission input shaft 270, but the negative torque provided by the ISG 240 may be limited by the transmission controller 254 outputting a transmission input shaft negative torque limit (e.g., a threshold value that is not exceeded). In addition, the negative torque of the ISG 240 may be limited (e.g., limited to less than a threshold negative threshold torque) by the vehicle system controller 255 or the motor controller 252 based on the operating conditions of the electrical energy storage device 275. Any portion of the desired negative wheel torque that may not be provided by the ISG 240 due to transmission or ISG limitations may be allocated to the friction brakes 218 so that the desired wheel torque is provided by a combination of the negative wheel torques from the friction brakes 218 and the ISG 240 .

[0045] Thus, torque control of various powertrain components may be directed by a vehicle system controller, with local torque control of the engine 10 , transmission 208 , motor 240 , and brake 218 provided by engine controller 12 , motor controller 252 , transmission controller 254 , and brake controller 250 .

[0046] As an example, the engine torque output may be controlled by adjusting a combination of ignition timing, fuel pulse width, fuel pulse timing, and / or air charge, by controlling throttle opening and / or valve timing, valve lift and boost for a turbocharged or supercharged engine. In the case of a diesel engine, the controller 12 may control the engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. In all cases, engine control may be performed on a cylinder-by-cylinder basis to control the engine torque output.

[0047] As is known in the art, the motor controller 252 may control torque output and electrical power generation from the ISG 240 by regulating current flow into and out of the field and / or armature windings of the ISG.

[0048] The transmission controller 254 receives the transmission input shaft position via the position sensor 271. The transmission controller 254 can convert the transmission input shaft position to the input shaft speed by differentiating the signal from the position sensor 271. The transmission controller 254 can receive the transmission output shaft torque from the torque sensor 272. Alternatively, the sensor 272 can be a position sensor or a torque and position sensor. If the sensor 272 is a position sensor, the controller 254 differentiates the position signal to determine the transmission output shaft speed. The transmission controller 254 can also differentiate the transmission output shaft speed to determine the transmission output shaft acceleration.

[0049] The brake controller 250 receives wheel speed information via the wheel speed sensor 221 and a brake request from the vehicle system controller 255. The brake controller 250 may also receive a brake request from the vehicle system controller 255 directly or via the CAN 299. Figure 1The brake pedal sensor 154 shown in receives brake pedal position information. The brake controller 250 can provide braking in response to a wheel torque command from the vehicle system controller 255. The brake controller 250 can also provide anti-skid and vehicle stability braking to improve vehicle braking and stability. In this way, the brake controller 250 can provide a wheel torque limit (e.g., a threshold negative wheel torque that is not exceeded) to the vehicle system controller 255 so that the negative ISG torque does not cause the wheel torque limit to be exceeded. For example, if the controller 250 issues a negative wheel torque limit of 50N-m, the ISG torque is adjusted to provide a negative torque of less than 50N-m (e.g., 49N-m) at the wheel, including taking into account the transmission gear being engaged.

[0050] therefore, Figure 1 and 2 A system is provided, comprising: an engine; a motor / generator; a transmission mechanically connected to the engine and the motor / generator, the transmission including a torque converter impeller; and a controller, the controller including executable instructions stored in a non-transitory memory, the executable instructions for adjusting the speed of the impeller from a first speed to a second predetermined speed in response to simultaneously applying a brake pedal to provide a drive wheel braking torque greater than a threshold amount and applying an accelerator pedal to a position greater than a threshold. The system also includes additional instructions for operating the engine with a fully open throttle in response to releasing the applied brake pedal. The system also includes additional instructions for adjusting the torque of the motor in response to releasing the applied brake to control wheel slip. The system also includes additional instructions for offsetting the torque requested via the accelerator pedal in response to the torque requested via the brake pedal when the accelerator pedal is in a position less than a threshold. The system also includes additional instructions for adjusting the torque of the motor / generator to provide a desired torque converter impeller torque that rotates the torque converter impeller at a second predetermined speed.

[0051] Reference now Figure 3 , showing several different speeds to which the torque converter impeller can be adjusted. The graph has a vertical axis representing torque and a horizontal axis representing speed. The graph includes three traces 302-306 and four speeds N1-N4, which represent different desired torque converter impeller speeds when the hybrid vehicle is operating in the launch control mode.

[0052] Curve 302 represents the sum of the maximum engine torque and the maximum motor (e.g., ISG) torque for the speed shown when the engine and motor are connected and rotate at the same speed. Curve 304 represents the maximum engine torque curve for the speed range shown, and curve 306 represents the maximum motor torque curve for the speed range shown. The maximum sum of the engine torque and the motor torque occurs at speed N1. Thus, if the engine and the motor rotate at speed N1, they can provide positive torque ranging from zero to the torque at speed N1 at curve 302, and the torque at speed N1 at curve 302 is the maximum sum of the engine torque and the motor torque.

[0053] In one example, the desired torque converter impeller speed in the pre-launch phase of the launch mode is the speed at which curve 302 is at a maximum value (i.e., N1). By adjusting the torque converter impeller speed to speed N1, the engine speed and the motor speed are pre-adjusted to speeds at which maximum powertrain output can be provided, so that when the vehicle begins to accelerate from zero speed during vehicle launch, the engine speed does not have to accelerate before reaching speed N1. By operating the engine and the motor at speed N1, the combined or total torque capacity of the engine and the motor (e.g., the maximum torque that the engine and the motor can output together) is greater than the total or combined torque output capacity of the engine and the motor when operating at any speed other than speed N1. In this way, operating the engine and the motor at speed N1 while the vehicle is not moving and just before the vehicle brake is released can enable maximum powertrain torque output to be achieved more quickly after the brake pedal is released, thereby improving vehicle acceleration.

[0054] In another example, where N2 is the stall speed of the torque converter, the desired torque converter impeller speed in the pre-start phase of the start mode is a speed N3 that is within a threshold speed of the stall speed N2 of the torque converter for a threshold amount of braking torque applied to the drive wheels. The stall speed of the torque converter is the torque converter impeller speed at which the vehicle wheels begin to rotate, and the stall speed may be responsive to the amount of braking torque applied to the drive vehicle wheels (e.g., wheels supplied with torque by an engine or motor). For example, if the vehicle brakes are not applied, the vehicle may start moving from zero speed when the torque converter impeller speed is 800 RPM. On the other hand, if a braking torque of 50 N-m is applied to the drive wheels via the friction brakes, the torque converter stall speed may be increased to 900 RPM, and then the friction braking torque may be overcome by the torque transmitted via the torque converter, causing the vehicle wheels to begin moving. Therefore, by adjusting the torque converter impeller speed to a speed within a threshold speed of the torque converter stall speed, the powertrain system can be preconditioned to a condition of increased torque converter efficiency so that vehicle acceleration can be improved after the vehicle brakes are released.

[0055] In another example, in the case where N4 is the stall speed of the torque converter, the desired torque converter impeller speed in the pre-start phase of the start mode is a speed N1 that is within a threshold speed of the stall speed N4 of the torque converter for a threshold amount of braking torque applied to the drive wheels. Therefore, if the torque converter stall speed is greater than the speed at which the maximum powertrain torque can be obtained by adjusting the torque converter impeller speed to a speed within the threshold speed of the torque converter stall speed, the powertrain speed at which the maximum powertrain torque can be obtained can be the desired torque converter impeller speed, and the powertrain can be pre-adjusted to a condition where the torque converter efficiency is increased, so that the vehicle acceleration can be improved after the vehicle brakes are released.

[0056] Reference now Figure 4 , showing an exemplary hybrid vehicle start in high performance start mode. Figure 1 and Figure 2 The system is based on Figure 5 Method to provide runtime timing. Figure 4 The graphs are time aligned to show each parameter at the same instant in time. The vertical markers T0-T3 indicate the times of interest in the time series.

[0057] from Figure 4 The first graph starting at the top is a graph of brake pedal position versus time. The vertical axis represents brake pedal position, and brake pedal position (e.g., trace 402) increases in the direction of the vertical axis arrow. The braking torque applied to the drive wheels increases as the brake pedal position increases. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Horizontal line 403 represents a threshold brake pedal position, which provides a threshold braking torque to the drive wheels that must be exceeded to enter the high-performance launch mode. The threshold brake pedal position may vary depending on vehicle operating conditions.

[0058] from Figure 4 The second graph from the top of is a graph of accelerator pedal position versus time. The vertical axis represents accelerator pedal position, and accelerator pedal position (e.g., trace 404) increases (e.g., is further applied or depressed) in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Horizontal line 405 represents a threshold accelerator pedal position that requests a threshold torque at the drive wheels that must be exceeded to enter the high-performance launch mode. The threshold accelerator pedal position may vary depending on vehicle operating conditions.

[0059] from Figure 4The third graph from the top of FIG. 4 is a graph of engine operating status versus time. The vertical axis represents the engine operating status, and when the trace 406 is a higher level near the vertical axis arrow, the engine is started and burning air and fuel. When the trace 406 is close to the horizontal axis, the engine is not started. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0060] from Figure 4 The fourth graph from the top of is a graph of desired torque converter impeller speed (solid line 408), torque converter turbine speed (dotted line 412), and actual torque converter impeller speed (dashed line 410) versus time. When only the desired torque converter impeller speed is visible, the desired torque converter impeller speed and the actual torque converter impeller speed are equal. The vertical axis represents speed, and speed increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0061] from Figure 4 The fifth graph from the top of is a graph of engine torque (dotted line 414), desired torque converter impeller torque (dashed line 416), and motor torque (solid line 418) versus time. The vertical axis represents torque, and torque increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph. Trace values ​​above the horizontal axis are positive, and trace values ​​below the horizontal axis are negative.

[0062] from Figure 4 The sixth graph from the top of FIG. 4 is a graph of wheel slip (line 420) versus time. The vertical axis represents wheel slip, and wheel slip increases in the direction of the vertical axis arrow. The horizontal axis represents time, and time increases from the left side of the graph to the right side of the graph.

[0063] At time T0, the accelerator pedal is not applied and the brake pedal is applied to a level greater than threshold 403. Therefore, the vehicle is not in high-performance launch mode. The engine is not running and its rotation is stopped. The torque converter impeller rotates at a lower speed equal to the desired torque converter impeller speed. Since the engine is stopped, the torque converter is rotated by the motor. The torque converter turbine is not running. The desired torque converter impeller torque is at a low value so that the transmission pump can rotate and supply transmission fluid to the driveline disconnect clutch and the transmission clutch. The engine torque is zero because the engine is not started and the wheel slip is zero.

[0064] At time T1, a driver (not shown) applies the accelerator pedal to a position greater than threshold 405, thereby enabling the high-performance launch mode. The engine starts and it combusts air and fuel in response to enabling the high-performance launch mode. The desired torque converter impeller speed increases to a second speed in response to entering the high-performance launch mode, and the actual torque converter impeller speed is increased by increasing the desired torque converter impeller torque. The second speed may be Figure 2 The engine torque is increased and the motor torque is adjusted to a negative torque so that when the engine torque and the motor torque are added together, the desired torque converter impeller torque is provided. The torque converter turbine speed is zero and the vehicle is not moving (not shown). In addition, there is no wheel slip.

[0065] At time T2, the driver (not shown) releases the brake pedal while maintaining the accelerator pedal position. As a result, vehicle launch begins and the torque converter turbine speed begins to increase. The engine remains enabled and it supplies torque to the torque converter impeller. The negative motor torque is converted to positive motor torque in response to the desired torque converter torque increase. The engine torque remains at the same level it was before time T2. The desired torque converter impeller speed and the actual torque converter impeller speed remain unchanged. The wheels do not slip.

[0066] Between time T2 and time T3, the wheels begin to slip and the motor torque is adjusted to control the wheel slip, and the engine torque remains unchanged. The torque converter turbine speed continues to increase, and the desired torque converter impeller speed and the actual torque converter impeller speed remain unchanged. The engine torque changes by a small amount, and the brake, accelerator, and engine maintain their respective states.

[0067] At time T3, the torque converter turbine speed is within the threshold speed of the torque converter speed, which causes the vehicle to exit the launch mode and enter the drive mode. The engine and the electric machine provide the desired torque converter impeller torque, and the torque converter turbine speed continues to increase as the torque converter impeller speed increases. By time T3, wheel slip has ceased.

[0068] In this way, engine torque and electric motor torque can be adjusted to improve vehicle launch and performance. Adjusting the torque converter impeller speed allows the vehicle to be prepared for a high-performance mode launch. In this particular sequence, the electric motor torque is negative during the pre-launch phase, which allows the engine torque to be converted into electrical energy. However, during other launch conditions, the electric motor torque can be zero or positive.

[0069] Reference now Figure 5, a method for operating a vehicle powertrain system is shown. At least a portion of method 500 may be implemented as executable controller instructions stored in a non-transitory memory. Additionally, portions of method 500 may be actions taken in the physical world to convert an operating state of an actuator or device.

[0070] At 502, method 500 determines whether the vehicle is parked. Method 500 may determine that the vehicle is parked in response to controller input from one or more wheel speed sensors. The vehicle is parked when the vehicle is not moving. If the method determines that the vehicle is parked, the answer is yes and method 500 proceeds to 504, otherwise, the answer is no and method 500 proceeds to 540.

[0071] At 540, method 500 provides the requested driver demand torque via torque output from the engine and motor (e.g., ISG 240). In one example, the driver demand torque is a torque requested by a human or autonomous driver. If a human makes a driver demand torque request, the driver demand torque request can be a function of vehicle speed and accelerator pedal position. Specifically, the accelerator pedal position and vehicle speed can index or guide a table or function of driver demand values ​​determined empirically. The table or function outputs the driver demand. The driver demand torque can be a torque request at the torque converter impeller or vehicle wheel. Logic and functions referenced by battery state of charge, battery temperature, driver demand torque, and other parameters can allocate a first portion of the requested driver demand torque to the engine and a second portion of the requested driver demand torque to the motor. The motor and engine are commanded to provide the driver demand torque and a torque for charging the battery or providing power to other devices. Method 500 proceeds to exit.

[0072] At 504, method 500 determines whether to enable the high-performance mode launch control mode. In one example, the high-performance mode launch control can be enabled in response to the accelerator pedal position exceeding a threshold and the brake pedal position or the drive wheel braking request exceeding a threshold. Therefore, in order to enter the high-performance mode launch control, method 500 can request that the accelerator pedal and the brake pedal be applied simultaneously. The threshold drive wheel braking amount can be a braking torque greater than the maximum engine torque, a braking torque that provides a desired torque converter stall speed, or another predetermined braking torque amount. The accelerator pedal position threshold can be a position representing a threshold driver demand torque (e.g., 75% of the maximum engine torque). If method 500 determines that there are conditions to enter the high-performance launch mode, the answer is yes, and method 500 proceeds to 506. Otherwise, the answer is no, and method 500 proceeds to 530.

[0073] At 530 , method 500 judges whether the driver demand torque is greater than a threshold. If method 500 concludes that the driver demand torque is greater than a threshold, the answer is yes and method 500 proceeds to 532 . Otherwise, the answer is no and method 500 proceeds to 536 .

[0074] If the brake pedal and accelerator pedal are applied simultaneously, the torque requested through the accelerator pedal is offset by the torque requested via the brake pedal. For example, if the driver requests 100 Nm of torque through the accelerator pedal and 50 Nm of torque through the brake pedal, the powertrain will provide 50 Nm of torque and the brakes will not be applied. Similarly, if the driver requests 100 Nm of torque through the accelerator pedal and 150 Nm of torque through the brake pedal, 50 Nm of torque is applied to the wheels and the powertrain torque is zero or -50 Nm with the motor providing the braking torque.

[0075] At 532, method 500 starts the motor and rotates the torque converter impeller to rotate the transmission pump if the motor is not started. The transmission pump supplies fluid to the transmission clutch and the driveline is disengaged. When the motor is started, the engine may be off and stop rotating. However, if the battery state of charge is less than a threshold, the engine can be started to rotate the transmission pump and charge the battery through the motor. The transmission pump rotates at a speed equal to or greater than the speed at which the pump provides a hydraulic line pressure greater than a threshold pressure sufficient to fully engage the transmission clutch and the driveline disconnect clutch. Method 500 proceeds to 534.

[0076] At 534 , method 500 provides the driver demand torque via the electric machine. Thus, the electric machine turns the transmission pump and provides the driver demand torque to propel the vehicle. Method 500 proceeds to exit.

[0077] At 536, method 500 starts the engine if the engine is not started and provides the driver demand torque via the engine. In addition, if the driver demand torque is high enough, the motor and the engine can provide the driver demand torque. If the engine can provide the driver demand torque without the motor, the motor can be turned off. Method 500 proceeds to exit.

[0078] At 506 , method 500 starts the engine with the engine stopped. Prior to entering the high-performance start mode, the engine may be stopped during vehicle deceleration or when the vehicle is stopped to save fuel. Method 500 proceeds to 508 after the engine is started.

[0079] At 508, method 500 determines whether the brake pedal is still applied after entering the high-performance launch mode. Additionally, in some examples, method 500 determines whether the brake pedal is applied at a position equal to or greater than the position at which the brake pedal was applied to enter the high-performance launch mode. If method 500 determines that the brake pedal is still applied, or alternatively, applied to the level at which it was applied when entering the high-performance launch mode, the answer is yes and method 500 proceeds to 510. Otherwise, the answer is no and method 500 proceeds to 520.

[0080] At 520, method 500 provides the driver demand torque requested via the engine to the transmission impeller. If the requested driver demand torque is greater than the torque that can be provided by the engine alone, the torque from the motor is provided to the driveline to meet the driver demand torque. The engine torque can be increased by adjusting the throttle opening and the amount of fuel injection. The motor torque can be increased by supplying additional current to the motor. The engine can be operated with the throttle fully open to provide the desired engine torque. Method 500 proceeds to 522.

[0081] At 522, method 500 determines the slip of the drive wheels. In one example, method 500 determines the slip of the rear drive wheels according to the following equation:

[0082]

[0083] where Δω is the speed difference between the front non-driven wheels and the rear driven wheels, or the wheel slip of the driven wheels, is the speed of the rear wheels, and is the rotational speed of the front wheels. Alternatively, the wheel slip can be determined by the following equation:

[0084] Δω=ω whl -v veh / r

[0085] Where Δω is the wheel slip of the driving wheel, ω whl is the speed of the rear wheels, v veh is the vehicle speed, and r is the wheel radius. Method 500 proceeds to 524 after determining the drive wheel slip.

[0086] At 524, method 500 determines the torque of the motor. In one example, the motor torque is determined by the following equation:

[0087]

[0088]

[0089]

[0090] in, is the motor torque adjusted according to the wheel slip or the absence of wheel slip, Δω is the slip of the drive wheels, is the gain (real number) when the slip exceeds the threshold, is the gain (real number) when the slip is less than the threshold, is the commanded motor torque, and τ dsd is the desired motor torque based on the driver demand torque. Therefore, if the wheel slip is greater than the threshold, the motor torque is reduced to reduce the wheel slip. If the wheel slip is less than the threshold, the motor torque is increased to increase vehicle acceleration. Method 500 proceeds to exit.

[0091] At 510, method 500 determines a desired torque converter impeller speed. The desired torque converter impeller speed is predetermined and may be based on engine properties (e.g., maximum torque, engine speed at which the engine produces maximum torque, etc.), motor properties (e.g., maximum motor torque, base motor speed, etc.), and torque converter properties (e.g., torque converter stall speed).

[0092] In one example, the desired torque converter impeller speed in the pre-launch phase of the launch mode is when the combined maximum engine torque curve and the maximum electric machine torque curve are at a maximum value (eg, Figure 3 When the torque converter impeller speed is adjusted to the speed N1, the engine speed and the motor speed are pre-adjusted to the speeds at which the maximum powertrain output can be provided, so that when the vehicle begins to accelerate from zero speed during vehicle launch, the engine speed does not have to be accelerated before reaching the speed N1.

[0093] In another example, the desired torque converter impeller speed in the pre-launch phase of the launch mode is a speed within a threshold speed of the stall speed of the torque converter for a threshold amount of braking torque applied to the drive wheels (eg, Figure 3 N3 in ). In addition, since the torque converter stall speed can change with the braking torque of the drive wheel, the speed can be a function of the braking torque. In one example, a table or function of speed values ​​determined empirically is indexed or directed by the braking torque of the drive wheel. The table or function outputs the desired torque converter impeller speed.

[0094] In another example, the desired torque converter impeller speed in the pre-launch stage of the launch mode is a speed N1 at which the maximum powertrain torque can be generated when the torque converter stall speed is greater than the speed at which the maximum powertrain torque can be generated (eg, Figure 3 Method 500 proceeds to 512 after determining the desired torque converter impeller speed.

[0095] At 512, method 500 determines a desired torque converter impeller torque. In one example, the desired impeller torque for maintaining the desired torque converter impeller speed may be determined using a combination of a torque converter model and a feedback controller based on the current impeller speed and the target impeller speed by the following equation:

[0096]

[0097] where τ des is the desired torque converter impeller torque to maintain the impeller at the desired impeller speed, is the predicted torque required to keep the impeller rotating at the desired speed target of the torque converter model, ω des is the desired / target impeller speed, ω imp is the actual impeller speed, and K p and K i is the controller gain of the proportional / integral (PI) controller (e.g., a real number). The predicted torque to rotate the impeller when the vehicle is launched can be determined by the following equation:

[0098]

[0099]

[0100] where ω tur is the turbine speed, and SR is the torque converter speed ratio. Method 500 proceeds to 514 .

[0101] At 514, method 500 requests a driver demand torque for the transmission impeller via the engine. The engine is commanded for the driver demand torque. The engine torque may be increased by adjusting the throttle opening amount and the fuel injection amount. The engine torque may be adjusted in response to the battery state of charge to meet the driver demand torque. Method 500 proceeds to 516.

[0102] At 516 , method 500 determines the motor torque. The motor torque is determined by the following equation:

[0103]

[0104] in is the requested motor torque, and τ eng is the actual engine torque. The motor torque may be increased by supplying additional current to the motor. The motor torque may be adjusted in response to the battery state of charge to meet the driver demand torque. Method 500 returns to 508 after the motor is commanded to reach the desired motor torque.

[0105] therefore, Figure 5A method of vehicle operation is provided, comprising: adjusting the speed of a torque converter impeller from a first speed to a second predetermined speed in response to the simultaneous application of a brake pedal and an accelerator pedal. The method includes wherein the second predetermined speed is a speed at which the engine and the motor can provide a combined first torque, the combined first torque being greater than the combined torque that the engine and the motor can output when operating at any speed different from the second speed. The method includes wherein the second predetermined speed is a function of the braking torque of the drive wheels, and the method further includes: starting the engine in response to the simultaneous application of the brake pedal and the accelerator pedal.

[0106] In some examples, the method further includes adjusting the torque of the engine and the torque of the electric motor after starting the engine to rotate the torque converter impeller at a second speed. The method includes wherein the torque of the engine and the torque of the electric motor are adjusted in response to the battery state of charge. The method includes wherein the first speed is a speed of the pump below which the pump provides a hydraulic line pressure less than a threshold pressure. The method includes wherein the threshold pressure is a pressure sufficient to fully engage the transmission clutch.

[0107] Figure 5 The method also provides a vehicle operation method, which includes: adjusting the speed of the torque converter impeller from a first speed to a second predetermined speed in response to the simultaneous application of a brake pedal and an accelerator pedal; and adjusting the output torque of the engine in response to releasing the applied brake pedal to provide a threshold torque. The method includes wherein the threshold torque is greater than the engine torque for any engine speed different from the engine speed when the threshold torque is provided. The method includes wherein the second predetermined speed is a threshold speed based on the stall speed of the torque converter, and the stall speed is based on the drive wheel braking torque. The method includes wherein adjusting the speed of the torque converter impeller from the first speed to the second predetermined speed includes adjusting the speed of the torque converter impeller only when the accelerator pedal position exceeds the threshold, and the engine is included after the vehicle stops.

[0108] In some examples, the method includes wherein adjusting the speed of the torque converter impeller from the first speed to the second predetermined speed includes adjusting the speed of the torque converter impeller only after providing a threshold drive wheel braking torque by applying the brake pedal. The method also includes offsetting the torque based on the accelerator pedal via the brake pedal torque in response to the accelerator pedal position being less than the threshold. The method also includes limiting the wheel slip to less than the threshold by adjusting the torque of the motor after releasing the brake pedal. The method also includes adjusting the torque of the motor when the brake pedal and the accelerator pedal are applied simultaneously to provide a desired torque converter impeller torque, the desired torque converter impeller torque being a torque that causes the torque converter impeller to rotate at the second predetermined speed.

[0109] It should be noted that the exemplary control and estimation procedures included herein can be used with various engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific procedures described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. As such, the various actions, operations, and / or functions shown can be executed in the timing shown, executed in parallel, or can be omitted in some cases. Similarly, the timing of the process is not necessary to achieve the features and advantages of the exemplary embodiments described herein, but is set for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly executed according to the specific strategy used. In addition, at least part of the described actions, operations, and / or functions can be graphically represented as codes in a non-transitory memory of a computer-readable storage medium programmed into the control system. When the described actions are performed by executing instructions in a system including various engine hardware components combined with one or more controllers, the control action can also convert the operating state of one or more sensors or actuators in the physical world.

[0110] Thus ends the specification. Those skilled in the art will appreciate that many changes and modifications will occur without departing from the spirit and scope of the embodiments. For example, hybrid electric vehicles including engines running in natural gas, gasoline, diesel or alternative fuel configurations may advantageously use the present specification.

Claims

1. A vehicle operation method, comprising: In response to the simultaneous application of the brake pedal and the accelerator pedal, the speed of the torque converter impeller is adjusted from a first speed to a second predetermined speed, wherein the second predetermined speed is a speed when the engine and the motor are able to provide a combined first torque, and the combined first torque is greater than the combined torque that can be output by the engine and the motor operating at any speed different from the second predetermined speed.

2. The method according to claim 1, wherein the second predetermined rotational speed is a function of a braking torque of a drive wheel, and the method further comprises: An engine is started in response to simultaneously applying the brake pedal and the accelerator pedal. 3 . The method of claim 2 , further comprising adjusting the torque of the engine and the torque of the electric machine after starting the engine so that the torque converter impeller rotates at the second predetermined speed. 4 . The method of claim 3 , wherein the torque of the engine and the torque of the electric machine are adjusted in response to a battery state of charge. 5 . The method of claim 1 , wherein the first speed is a speed of a pump, and when equal to or greater than the speed of the pump, the pump provides a hydraulic line pressure greater than a threshold pressure. The method of claim 5 , wherein the threshold pressure is a pressure sufficient to fully engage a transmission clutch.

7. A vehicle operation method, comprising: adjusting the speed of the torque converter impeller from a first speed to a second predetermined speed in response to simultaneous application of a brake pedal and an accelerator pedal; adjusting the output torque of the engine to provide a threshold torque in response to releasing the applied brake pedal, Wherein adjusting the speed of the torque converter impeller from the first speed to the second predetermined speed includes adjusting the speed of the torque converter impeller only after the accelerator pedal position exceeds a threshold while the vehicle including the engine is stopped. 8 . The method of claim 7 , wherein the threshold torque is greater than the engine torque for any engine speed other than the engine speed at which the threshold torque is provided. 9 . The method of claim 7 , wherein the second predetermined speed is a threshold speed based on a stall speed of the torque converter, the stall speed being based on a braking torque of a drive wheel.

10. A system for a vehicle, comprising: engine; Motor / generator; a transmission mechanically connected to the engine and the motor / generator, the transmission including a torque converter impeller; and A controller comprising executable instructions stored in a non-transitory memory, the executable instructions being used to adjust the speed of the impeller from a first speed to a second predetermined speed in response to simultaneously applying a brake pedal to provide a drive wheel braking torque greater than a threshold amount and applying an accelerator pedal to a position greater than a threshold, wherein the second predetermined speed is a speed at which the engine and the motor are able to provide a combined first torque that is greater than the combined torque that the engine and the motor can output when operating at any speed different from the second predetermined speed.

11. The system of claim 10 further comprising additional instructions for operating the engine at a wide open throttle in response to releasing the applied brake pedal.

12. The system of claim 11 further comprising additional instructions for adjusting torque of the electric motor in response to releasing the applied brake pedal to control wheel slip.

13. The system of claim 10 further comprising additional instructions for counteracting torque requested via the accelerator pedal in response to torque requested via the brake pedal when the accelerator pedal is in a position less than the threshold.

14. The system of claim 10 further comprising additional instructions for adjusting torque of the motor / generator to provide a desired torque converter impeller torque to rotate the torque converter impeller at the second predetermined speed.

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