DE102013208858B4 - Method of commanding a synchronous gear shift in a vehicle powertrain - Google Patents

Abstract

A method for commanding a synchronous gear shift in a vehicle powertrain including an engine (12) and a transmission (16) having a plurality of ordered gears, the method comprising:receiving a request to shift from a third gear to a first gear and for skipping a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear;reducing a torque command to a predetermined value;opening a clutch (74, 76) arranged on the input shaft (18) of the transmission (16). ) to decouple the transmission (16) from the engine (12); transitioning the engine (12) from a torque control mode to a speed control mode; commanding the engine (12) while in the speed control mode to be at a through the movement of the vehicle and dictated by the gear ratio of the first gear rotates at that speed;closing the clutch to couple the transmission (16) and the engine (12); and transitioning the engine (12) back to the torque control mode.

Description

TECHNICAL AREA

The present invention relates generally to torque control methods for achieving synchronous gear shifting in a vehicle having an engine and a transmission coupled to the engine via an input clutch.

In principle, jump gear downshifts without an intermediate gear stage in connection with an engine torque reduction control are known, see, for example, FIG DE 101 55 603 A1 . Skip downshifts are also known in the area of dual clutch transmissions, which take place within a sub-transmission, see, for example, DE 10 2010 011 241 A1 and the DE 10 2006 000 380 A1 . Jump downshifts are also known, the shifting method of which begins with a torque reduction, see the DE 692 13 813 T2 .

BACKGROUND

Modern vehicles are often equipped with multi-speed dual clutch transmissions (multi-speed DCTs) as part of the vehicle's powertrain. Such DCTs are preferred because of their increased mechanical efficiency compared to typical torque converter equipped automatic transmissions. Additionally, DCTs are often preferred over typical automated manual transmissions because of the ability of DCTs to provide higher quality gear shifts.

A typical DCT uses two friction clutches to shift between its forward speed ratios and achieves these shifts by alternately engaging one and the other of the two friction clutches. Such a multi-speed dual clutch transmission can be used in a hybrid vehicle, i. H. in a vehicle that uses two or more different power sources, such as an engine and an electric motor to transmit propulsion energy to the driven wheels of the respective vehicle.

SUMMARY

A method of commanding a synchronous gear shift begins by receiving a request to shift from a third gear to a first gear and to skip a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear. As will be appreciated, first, second, and third gears can be any gears within an automatic transmission gear set such that they are distinct gears. The method may further include: reducing a torque command to a predetermined value; opening a clutch disposed on the input shaft of the transmission to decouple the transmission from the engine; transitioning the engine from a torque control mode to a speed control mode; commanding the engine to rotate at a speed dictated by movement of the vehicle and by the gear ratio of the first gear; closing the clutch to couple the transmission and the engine; and transitioning the engine back to the torque control mode.

In one configuration, reducing a torque command to a predetermined value may include reducing engine torque via an immediate torque request. The immediate torque request may cause a change in spark timing and/or an amount of fuel delivered to a cylinder. During this control, the torque command and engine speed may be independently controllable through adjustment of spark timing, fueling, and further by changing airflow delivery.

The torque command may be configured to saturate at an immediate torque maximum during speed control mode. Likewise, the immediate torque maximum may include a maximum amount of torque that can be produced by an engine at a fixed airflow (i.e., above the immediate torque request).

Before closing the clutch to couple the transmission and the engine, the torque command may approach zero to ensure a smooth transition. Additionally, during speed control mode, the engine controller may ignore any driver-supplied axle torque request. When the shift sequence is complete, the controller may gradually transition the engine back into torque control mode over a period of time. As can be appreciated, when the engine is in a torque control mode, the torque command may be largely a function of a driver acceleration request.

The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

character list

• 1 1 is a schematic diagram of a vehicle powertrain in conjunction with an engine control module and with a transmission control module.
• 2 12 is a schematic, partial cross-sectional view of a dual clutch transmission.
• 3 1 is a functional schematic diagram of an embodiment of an engine control module in conjunction with a transmission control module.
• 4 12 is a schematic graph of a synchronous transmission shift in a dual clutch transmission initiated by a transmission control module after a hard acceleration request.
• 5 Figure 12 is a schematic graph of a synchronous transmission shift to a lower gear in a dual clutch transmission, the shift being initiated by a driver through an electronically controlled manual shift selector.
• 6 Figure 12 is a schematic graph of a synchronous transmission shift to a higher gear in a dual clutch transmission where the shift is initiated by a driver via an electronically controlled manual shift selector.
• 7 1 is a schematic diagram of a method for commanding a synchronous gear shift in a vehicle powertrain including an engine and a transmission.

DETAILED DESCRIPTION

In the drawings, wherein like reference characters refer to like components throughout the several views 1 a vehicle 10 having a powertrain including an engine 12 and a transmission 16 . The engine 12 is a spark-ignition internal combustion engine. In another embodiment, engine 12 may be a diesel engine without the spark actuation discussed herein. The transmission 16 may be an automatic transmission having a plurality of intermeshing gears and selectively engageable clutches that establish various speed ratios between a transmission input member 18 and a transmission output member 20 . A crankshaft 22 of the engine 12 is rotatably connectable to the transmission input member 18 to provide torque from the input member 18 to the output member 20 at a gear ratio established by the transmission 16 . Torque from the output member 20 is delivered to vehicle wheels 26 via a final drive mechanism 24 . In some embodiments, vehicle 10 may be a hybrid vehicle that includes one or more electric motors/generators. For example, a motor/generator 28 may be coupled to the crankshaft 22 by a belt and pulley arrangement or otherwise and for providing torque to increase torque at the crankshaft 22 or decrease torque at the crankshaft 22, such as when operating as a generator in a regenerative braking mode.

The vehicle 10 includes a control system 30 that includes at least an engine control module (ECM) 32 and a transmission control module (TCM) 34 . The ECM 32 may be referred to as a first controller and the TCM 34 may be referred to as a second controller. The ECM 32 and TCM 34 are operatively connected to coordinate control of the engine 12 and transmission 16 . Alternatively, the ECM 32 and the TCM 34 may be configured as a single powertrain control module having the functionality of both the ECM 32 and the TCM 34 .

As described further below, the ECM 32 and the TCM 34 may be configured to work together to control smooth operation of the vehicle powertrain. For example, the TCM 34 may communicate with the ECM 32 to coordinate shifting of gears within the transmission 16 by temporarily reducing torque at the crankshaft 22 (i.e., crankshaft torque) during the shift. Likewise, the TCM 34 may be configured to limit the maximum torque provided by the engine to protect transmission components.

The ECM 32 includes a processor 36 configured to control engine functions. The processor 36 can e.g. B. may have a stored algorithm that the torque commanded by the ECM 32 at the crankshaft 22 based on vehicle operating conditions, driver input and, as described herein, requests from the TCM 34 for torque management before and during Transmission shifts determined. As further described below, the algorithm may also determine different torque capacities at the crankshaft 22 that are available when different torque actuators are controlled to be in different states. As used herein, a “torque actuator” is a system that changes an engine parameter to affect crankshaft torque. For example, some of the torque actuators that may be controllable by the ECM 32 to change the torque at the crankshaft 22 include: B. an airflow actuator or module 50 that controls airflow to engine cylinders 46, a spark actuator or module 52 that controls spark ignition timing, and a fuel actuator or module 56 that controls controls fuel to the engine cylinders 46 .

The TCM 34 may also include a processor 38 having an algorithm operable to control the timing and duration of transmission shifts. The TCM processor 38 may also be configured to determine a range of crankshaft 22 torque reduction requested by the ECM 32 during a transmission 16 shift, such as during an upshift. The range of requested torque reduction is based at least in part on the torque capacities determined by the ECM 32 .

A request for torque, or for an amount of torque reduction, or for removal of the torque reduction via spark, fuel, or electric motor/generator control is referred to as an immediate torque request, or an immediate torque request, while a torque or amount request of torque reduction during airflow control is referred to as a predicted torque request or a predicted torque request. Changes in spark timing and changes in fuel delivery such as fuel cut (also referred to as fuel cut) occur relatively quickly compared to a change in airflow. Thus, airflow is referred to as a relatively slow torque actuator, while spark timing and fuel cut-off are referred to as relatively fast torque actuators.

The airflow actuator provided by the engine 12 affects torque at the crankshaft 22 because of the control of airflow through the throttle 40, such as by opening or closing the throttle 40 to a greater or lesser degree, because of the control of the airflow through turbo booster or supercharger 42, to affect the air pressure in the engine 12, and because of the control of air flow by cam phasers 44, which control the timing of the intake valves and the exhaust valves for the engine cylinders 46. The airflow actuator may be part of the airflow actuator module 50 that sends actuation signals to the throttle 40, the turbocharger and/or supercharger 42, and the phaser 44. Controlling torque through changes in airflow has an inherent lag between actuation or implementation of the airflow torque request and the effect of the request on crankshaft torque. Thus, such a request is referred to as a predicted request because it relates to an effect of crankshaft torque that is predicted to occur some delay after the actuation occurs. For example, a change in throttle position does not have a full effect on crankshaft torque until air currently in the manifold and cylinders 46 is pushed through the engine 12 . The timing response of crankshaft torque to a predicted torque request can vary based on many factors due to the nature of air flow control. One such factor is engine speed. Executing shifts with a predicted torque reduction and with an immediate torque reduction may provide more overall reduction than the immediate torque reduction alone. However, due to the nature of the response to predicted torque requests on spark-ignition gasoline engines, more coordination of the timing of the torque requests may be necessary.

The spark actuator may be part of the spark actuation module 52 that sends actuation signals to control the timing of the spark produced by spark plugs 54 (one shown) relative to the top dead center (TDC) of the pistons within the cylinders 46 . For a given engine combustion mixture, there is an optimal spark timing setting that is a function of engine speed, amount of combustible air in the mixture, charge temperature, and other factors. Timing the spark later than this optimal spark timing is referred to as spark retardation because it causes combustion within the cylinder 46 generated at the crankshaft 22 less torque.

The spark actuator may be part of a fuel actuation module 56 that sends actuation signals to control fuel flow, such as through a fuel injector 58 for each of the cylinders 46 (one shown). When the fuel torque command signal is used to cause fuel cutoff to occur, no combustion occurs in the cylinders 46 and crankshaft torque is significantly reduced.

The axle torque provided at the transmission output member 20 is fundamentally determined in part based on an operator requested axle torque and on torque intervention requests received from other vehicle systems, the torque intervention requests being subject to limitations imposed by the TCM 34 and by the ECM 32 which opposes propulsion in one direction of motion to the intended direction of movement and for the most part prevented, and which also prevents excessive deceleration of the vehicle 10. The operator may be a driver, in which case the axle torque requested by the operator is the axle torque desired by the driver. In one configuration, the control algorithms executed by the TCM 34 and/or the ECM 32 may be based on either a desired crankshaft torque or axle torque.

A driver operated accelerator pedal device 60 , such as an accelerator pedal, is operable to provide a driver requested axle torque signal 62 to the ECM 32 . The driver-demanded axle torque signal 62 may be an electrical signal representing the position of the accelerator pedal assembly 60 , which may be correlated to a driver-demanded axle torque at the transmission output member 20 . The axle torque request is the sum of the torque on all axles. In an all-wheel drive application, a 400 Nm requirement can be achieved with 200 Nm on both axles, or with 300 Nm on one axle and 100 Nm on the other axle.

A driver operated braking device 64 , such as a brake pedal, is operable to provide a driver requested braking torque signal 66 to the TCM 34 . The driver-demanded braking torque signal 66 represents the position of the braking device 64, which may be correlated to a driver-demanded braking torque applied to one or more of the vehicle wheels 26 via a braking system. The braking torque is an axle torque in a direction opposite to that of the driver-requested axle torque associated with the accelerator pedal device 60 .

2 illustrates a schematic cross-sectional view of in 1 offered transmission 16. As shown, the transmission 16 may be a dual clutch transmission (DCT) and may include a clutch subsystem 70 located within a clutch housing 72 and includes dry clutches 74 and 76. As shown, the clutch 74 is an even ratio clutch and clutch 76 is an odd ratio clutch. The clutches 74, 76 are configured to select the particular drive ratio in the DCT 16. Specifically, clutch 74 includes clutch disc 80 with friction facings 80-1, while clutch 76 includes clutch disc 82 with friction facings 82-1. The DCT 16 also includes a clutch cover 84 having a portion 86 utilized to actuate the clutch 74 via a spring 88 and a portion 90 utilized to actuate the clutch 76 via a spring 92 . In addition, clutch 74 includes a pressure plate 94 while clutch 76 includes a pressure plate 96 .

In addition, clutches 74 and 76 share a center plate 98, with each of pressure plates 94 and 96 clamping respective friction pads 80-1 and 82-1 at a predetermined rate against center plate 98 by the action of springs 88 and 92 to secure the respective engage the clutch. During normal operation of the DCT 16, when one of the clutches 74, 76 is transferring engine torque in any particular gear ratio, the other of the two clutches may preselect an appropriate oncoming gear ratio synchronizer. A valve body can control the selective engagement of the clutches 74, 76 by directing control fluid to various solenoids (not shown), which in turn regulate the flow of control fluid to the appropriate clutch.

well in 3 A functional block diagram of an example engine control system is presented. An example implementation of an ECM 32 includes an axle torque arbitration module 104. The axle torque arbitration module 104 arbitrates between a driver input 62 from a driver input module (eg, from the accelerator pedal device 60) and other axle torque requests 105. The drivers gift 62 can e.g. B. based on a position of an accelerator pedal. Driver input 62 may also be based on cruise control, which may be adaptive cruise control that maintains a predetermined following distance.

Torque requests may include torque target values as well as increase/decrease requests, such as a request for torque to decrease to a minimum engine off torque or for torque to increase from the minimum engine off torque. Axle torque requests 105 may include a torque reduction requested by a traction control system during wheel slip. Additionally, axle torque requests 105 may include torque request increases to counteract negative wheel slip, where a tire of the vehicle is slipping relative to the road surface because the axle torque is negative.

Additionally, axle torque requests 105 may include brake management requests, vehicle overspeed torque requests, and/or low speed vehicle creep requests. Brake management requests may reduce engine torque to ensure engine torque output does not exceed the ability of the brakes to hold the vehicle when the vehicle is stopped. Vehicle overspeed torque requests may reduce engine torque output to prevent the vehicle from exceeding a predetermined speed. Axle torque requests 105 may also be generated by body stability control systems. Further, axle torque requests may include engine shutdown requests, such as may be generated when a critical failure is detected.

The axle torque decision module 104 outputs a predicted torque and an immediate torque based on the results of the decision between the received torque requests. The predicted torque is the amount of torque that the ECM 32 prepares to produce, and may often be based on the driver's torque request. The immediate torque is the amount of currently desired torque, which may be less than the predicted torque.

To provide torque reserves and to meet current torque reductions, as described in more detail below, the immediate torque may be less than the predicted torque. For example only, temporary torque reductions may be requested as a vehicle speed approaches an overspeed threshold when the traction control system detects wheel slip.

The immediate torque may be achieved by changing engine actuators that respond quickly while using slower engine actuators to prepare for the predicted torque. As described above, z. For example, spark advance may be adjusted quickly, while cam phaser position and airflow may respond more slowly because of the mechanical lag time. Furthermore, changes in air flow are subject to air transport delays in the intake manifold. In addition, changes in airflow do not appear as changes in torque until air has been drawn into a cylinder, compressed within it, and combusted.

By adjusting slower engine actuators to produce a predicted torque while adjusting faster engine actuators to produce an immediate torque that is less than the predicted torque, a torque reserve may be created. For example, a throttle may be opened, thereby increasing airflow and preparing for generation of the predicted torque. Meanwhile, the spark advance may be reduced (in other words, the spark timing may be retarded), thereby reducing the actual engine torque output to the immediate torque.

The difference between the predicted torque and the immediate torque can be called the torque reserve. When there is a torque reserve, the engine torque may be quickly increased from the immediate torque to the predicted torque by changing a faster actuator. This achieves the predicted torque without waiting for a change in torque to result from an adjustment to one of the slower actuators.

The axle torque decision module 104 outputs the predicted torque and the immediate torque to a propulsion torque decision module 106 . In various hybrid implementations (ie, those that include a motor/generator 28), axle rotation torque decision module 104 output the predicted torque and the immediate torque to a hybrid optimization module 108 . The hybrid optimization module 108 determines how much torque should be produced by an engine and how much torque should be produced by a motor/generator 28 . The hybrid optimization module 108 then outputs to the propulsion torque decision module 106 modified values of the predicted torque and the immediate torque.

The predicted torque and immediate torque received from the propulsion torque decision module 106 may be converted from an axle torque range (torque at the wheels) to a propulsion torque range (torque at the crankshaft). This conversion may occur before, after, as part of, or in place of the hybrid optimization module 108 .

The propulsion torque arbitration module 106 may arbitrate between propulsion torque requests including the implicit predicted torque and the implicit implicit torque. The propulsion torque arbitration module 106 may generate an arbitrated predicted torque and an arbitrated immediate torque. The arbitrated torques can be generated by selecting the winning request from among the received requests. Alternatively or additionally, the arbitrated torques may be generated by changing one of the received requests based on another one or more of the received requests.

Other propulsion torque requests 109 may include torque reductions for engine overspeed protection, torque increases for stall prevention, and torque reductions requested by the TCM 34 to accommodate gear shifts. In addition, propulsion torque requests 109 may result from clutch fuel cutoff, which may reduce engine torque output when the driver depresses the clutch pedal in a manual transmission vehicle.

Additionally, propulsion torque requests 109 may include an engine shutdown request, which may be initiated when a critical failure is detected. For example only, critical faults may include detection of vehicle theft, a stuck starter motor, problems with electronic throttle control, and unexpected torque increases. For example only, engine shutdown requests may always win the arbitration and thereby be output as the arbitrated torques, or bypass the arbitration altogether, simply shutting down the engine regardless of the torque. The propulsion torque decision module 106 may continue to receive these shutdown requests such that e.g. B. suitable data can be fed back to other torque request devices. For example, all other torque request devices may be informed that they have lost arbitration.

An RPM control module 110 , also referred to as a vehicle idle module 110 , may also output predicted torque requests and immediate torque requests to the propulsion torque decision module 106 . When the ECM 32 is in RPM mode, the torque requests from the RPM control module 110 may prevail in the arbitration. RPM mode may be selected when the driver takes their feet off the accelerator pedal, such as when the vehicle is idling or coasting from a higher speed. Alternatively or additionally, the RPM mode may be selected when the predicted torque requested by the axle torque decision module 104 is less than a calibratable torque value.

The RPM control module 110 may receive a desired RPM from an RPM trajectory module 112 and may control the predicted torque and immediate torque requests to reduce the difference between the desired RPM and the actual RPM. For example only, the RPM trajectory module 112 may output a linearly decreasing desired RPM for vehicle coasting until engine RPM reaches an idle RPM. The RPM trajectory module 112 may then continue to output the idle RPM as the desired RPM. Alternatively, the RPM control module 110 may operate in low speed conditions as directed by the TCM 34 . In addition to the RPM control module, the ECM 32 may include a speed control module 111 that may receive a speed command from the TCM 34 and that may operate in a closed loop manner to regulate engine output speed in a non-idle scenario such that it matches a requirement.

A reserves/loads module 120 may receive the arbitrated predicted torque requests and immediate torque requests from the propulsion torque decision module 106 received. Various engine operating conditions may affect engine torque output. The reserves/loads module 120 may generate a torque reserve in response to these conditions by increasing the predicted torque request.

For example only, a catalyst light off process or a cold start emissions reduction process may directly alter spark advance for an engine. Thus, the reserves/stresses module 120 may increase the predicted torque request to counteract the effect of this spark advance on the engine torque output. In another example, engine air/fuel ratio and/or mass airflow may be altered directly, such as through diagnostic intrusive equivalence ratio testing and/or by purging a new engine. Corresponding predicted torque increases may be made to compensate for changes in engine torque output during these processes.

The reserves/loads module 120 may also generate a reserve in anticipation of a future load such as air conditioning compressor clutch engagement or power steering pump operation. The reserve for A/C clutch engagement may be created when the driver initially requests air conditioning. When the A/C clutch is then engaged, the reserves/loads module 120 may add the expected load on the A/C clutch to the immediate torque request.

An actuation module 124 receives the predicted torque and immediate torque requests as an output by the reserves/loads module 120. The actuation module 124 may determine how to achieve the predicted torque requests and the immediate torque requests. The actuation module 124 may be engine type specific with different control schemes for gasoline engines versus diesel engines. In various implementations, the actuation module 124 may define the boundary between modules upstream of the actuation module 124 that are engine independent and modules that are engine dependent.

For example, in a gasoline engine, the actuation module 124 may change the opening of the throttle 40, allowing for a wide range of torque control. However, opening and closing the throttle 40 can result in a relatively slow change in torque. Cylinder deactivation also offers a wide range of torque control, but may be relatively slow and may present additional driveability and emissions concerns. Changing the spark advance is relatively quick but does not offer a large range of torque control. Also, the amount of torque control possible with the spark (referred to as spark capacity) changes as the air per cylinder changes.

In various implementations, the actuation module 124 may generate an air torque request 125 based on the predicted torque request. The air torque request may be equal to the predicted torque request, causing the airflow to be adjusted so that the predicted torque request can be achieved simply through changes to other actuators.

An air control module 128 may determine desired actuator values for slow actuators based on the air torque request. The air control module 128 can z. B. control the desired manifold absolute pressure (MAP), the desired throttle area and/or the desired air per cylinder (APC). Desired MAP may be used to determine desired boost pressure and desired APC may be used to determine desired cam phaser positions.

In gasoline systems, the actuation module 124 may also generate a spark torque request 129 , a cylinder deactivation torque request 130 , and a fuel mass torque request 131 . The spark torque request may be used by a spark control module 132 to determine how much to retard spark from a calibrated spark advance (which reduces engine torque output). The spark control module 132 controls the spark actuator module 52. In diesel systems, fuel mass may be the primary actuator for controlling engine torque output.

The cylinder deactivation torque request may be used by a cylinder control module 136 to determine how many cylinders to deactivate. The cylinder control module 136 may be a fuel control module 138 to stop providing fuel to deactivated cylinders and may command the spark control module 132 to stop providing spark to deactivated cylinders.

The fuel mass torque request 131 may be used by the fuel control module 138 to change the amount of fuel provided to each cylinder 46 . For example only, the fuel control module 138 may determine a fuel mass that, when combined with the current amount of air per cylinder 46, provides stoichiometric combustion. The fuel control module 138 may command the fuel actuator module 56 to inject this mass of fuel for each activated cylinder 46 . During normal engine operation, the fuel control module 138 may attempt to maintain a stoichiometric air/fuel ratio.

The fuel control module 138 may increase fuel mass above stoichiometric to increase engine torque output and may decrease fuel mass to decrease engine torque output. In various implementations, the fuel control module 138 may receive a desired air/fuel ratio that differs from stoichiometry. The fuel control module 138 may then determine a fuel mass for each cylinder 46 that achieves the desired air/fuel ratio.

A torque estimation module 140 may estimate the torque output of the engine. This estimated torque may be used by the air control module 128 to perform closed-loop control of engine airflow parameters such as MAP, throttle area, and phaser positions. For example only, a torque relationship such as that where torque (T) is a function of air per cylinder (APC), spark advance (S), intake cam phaser position (I), exhaust cam phaser position may be defined (E), air/fuel ratio (AF), oil temperature (OT) and number of activated cylinders (#). Additional variables, such as the degree of opening of an exhaust gas recirculation (EGR) valve, may be considered.

This relationship can be modeled by an equation and/or can be stored as a look-up table. The torque estimation module 140 may determine the APC based on the measured mass air flow (MAF) and the current RPM, thereby facilitating air control based on the actual air flow. The intake and exhaust cam phaser positions used may be based on actual positions, while the phasers may move toward the desired positions. In addition, a calibrated spark advance value may be used. This estimated torque can be referred to as an air torque - i.e. H. as an estimate of how much torque could be produced at the current airflow regardless of actual engine torque output changing based on spark advance.

The air control module 128 may generate a desired manifold absolute pressure (MAP) signal that is output to a boost scheduling module 142 . The boost scheduling module 142 may use the desired MAP signal to control the one or more turbochargers and/or superchargers 42 .

The air control module 128 may generate a desired area signal that is used to regulate the throttle plate 40 to generate the desired throttle opening area. The air control module 128 may use the estimated torque and/or the MAF signal to perform feedback control. For example, the desired area signal may be controlled based on a comparison of the estimated torque and the air torque request.

The air control module 128 may also generate a desired air per cylinder (APC) signal that is output to a phaser scheduling module 144 . The phaser scheduling module 144 may control positions of the intake and/or exhaust cam phasers 44 based on the desired APC signal and the desired RPM signal.

Again based on 2 For example, as discussed, the DCT 16 can perform gear shifts during normal operation using a so-called asynchronous shift. During an asynchronous shift, the DCT 16 begins to apply a next-gear clutch (ie, the on-coming clutch) while the present-gear clutch (ie, the off-going clutch) still retains some torque-carrying capability, albeit dropping. This is done in such a way that torque can be transmitted from the engine to the axles throughout the shift. An asynchronous shift minimizes the perception of loss of acceleration (ie, sag) during a shift. However, can the transmission input speed cannot simultaneously be at the speed required for both the current and next gears due to the changing gear ratios of the various transmission gears, hence the term "asynchronous".

However, in certain scenarios, an asynchronous shift cannot be performed. If the driver uses the accelerator pedal device 60 e.g. B. engages quite vigorously, downshifting several gears may be necessary. In this case, the TCM 34 has the option to shift into one or more intermediate gears in an asynchronous manner before arriving at the final target gear. However, this can take an undesirable amount of time. Another option may be disengaging the engine 14 from the transmission 16 by opening the input clutch while then preparing the gear train for the desired gear. This may take less time but could result in a temporary loss of acceleration. Such a gear shift may be referred to as a "synchronous" shift because the engine speed would be controlled to match the transmission input shaft speed for the desired gear. Synchronous shifting may also be required should the driver manually tap through multiple gears, such as using an electronic gear selector (commonly referred to as "paddle shifters").

4-6 schematically represent three types of synchronous circuits. As shown, represents 4 a synchronous shift initiated by the TCM 34 when the driver energetically engages the accelerator pedal device 60 . 5 represents a synchronous shift initiated when the driver manually taps down through multiple gears, and 6 represents a synchronous shift initiated when the driver manually taps up through multiple gears. It should be recognized that other potential scenarios are possible.

4 Figure 12 illustrates several graphs all coordinated in time 200. From top to bottom, the graphs represent: the driver requested axle torque signal 62 (ie, from an accelerator pedal 60); an engine speed/angular rate 202 and a transmission input shaft angular rate 204; an input clutch engagement pressure 206 (ie, torque-carrying capacity); and an engine torque (generally at 208).

As shown, a driver may engage the accelerator pedal device 60 at a first time 210 . Within a short period of time after initial onset, the TCM 34 may recognize that a multi-speed shift is required. Such a decision may be based on the degree or on the slope of the torque signal 62 adjustment. The TCM 34 may send a torque reduction request 212 to the axle torque decision module 104 in anticipation of clutch disengagement to rapidly reduce the torque output of the engine 12 . When the predicted engine output torque 214 approaches a predetermined value to minimize disturbance when the input clutch is opened (generally at 216), the TCM 34 may the input clutch of the transmission 16 (ie, at time 218), as indicated by the clutch engagement state 206 seen at 220, disengage. The predetermined value may be a value lower than the previously applied torque. This lower value can provide a more gradual change in acceleration rather than a jerk like the clutch suddenly releasing.

After disengaging the clutch at time 218 , the TCM 34 may command a speed control mode for the ECM 32 via the speed control module 111 . In the speed control module, under speed control of the ECM 32, the engine speed 202 is increased to a higher level to match a lower gear. During this phase, the ECM 32 may increase torque up to a saturated maximum (generally at 222). The ECM 32 may increase the predicted torque produced 214 in response to the speed control request from the TCM 34, albeit with a slight time delay. As the engine speed increases, a gear change may occur within the transmission 16, with the gear change in 4 by the increase in transmission input shaft angular velocity 204 (generally at 224).

As the engine speed 202 approaches the desired output speed 226, the required torque may decrease back to a lower value (generally at 228). At this point, the ECM speed controller may make an immediate request along with the predicted request to establish a torque reserve. This requirement provides the speed controller with the ability to rapidly increase torque to tightly control the target speed. As engine speed approaches target, it can then tightly control overshoot and undershoot using the torque reserve provided by the instantaneous actuators.

During the speed control mode between time 218 and time 228, the ECM 32 may ignore any torque requests made by the TCM 34 (such as requests passing through the axle torque decision module 104). Prior to 228, the TCM 34 provides a torque request equal to the ECM's estimated torque for an initialization point upon exiting cruise control mode. When the clutch is re-engaged, the transmission controls disable speed control mode and use this pending torque request to command the ECM 32. The TCM torque reduction request 212 may be increased (less reduction from driver) and gradually returned to driver control (generally at 230). 4 further illustrates the ideal steady-state torque profile 232 that, along with the engine speed 202, would not produce noticeable power sags/swells to the driver. However, such a profile may be unattainable due to the need for low or zero output torque during the shift. Nonetheless, it can serve as the baseline that the TCM 34 achieves before and after the shift.

During the entire period that the clutch is disengaged (ie, during period 234), the ECM 32 is intended to be in a controlled speed mode where it attempts to change the engine speed to a new target value as quickly as possible while certain specified limit values are not exceeded.

5 and 6 illustrate the corresponding graphs for a manual tap down through the gears ( 5 ) and for a manual tap up through the gears ( 6 ).

How out 4-6 and as can be seen from the discussion above, the TCM 34 should control the input clutch load to 0 Nm (open clutch) while the speed request is active (i.e. when the engine is changed up or down to match the speed of the new gear ). As such, the TCM 34 may need to be changed from the steady state torque 232 to a desired value before the speed control request to the ECM 32 is enabled. At the end of the speed control event (ie, ramp up or ramp down), the engine torque produced is typically near 0 Nm since there is no load from the transmission 16 on the engine 14 and the engine speed 202 is accelerating to the target value. However, the driver demand (or the result of arbitration with intervention demand devices other than the transmission) typically commands the desired torque (e.g., desired steady-state torque 232) to be different than speed controlled torque. Thus, the TCM 34 is to provide a change from the torque resulting from the cruise control mode back to the desired steady-state torque 232 .

If a synchronous shift is not available, the TCM 34 may revert to a mode in which asynchronous shifts are performed to cycle through the various gears until the desired gear is reached.

When the TCM 34 requests a synchronous shift, the ECM 32 is commanded into a speed control mode from the ECM standpoint at the speed control module 111 . To ensure engine speed 202 does not drop below engine idle speed, a minimum RPM limit may be set. In one configuration, engine speed may be maintained above engine idle speed by a certain offset. If an engine speed request from the TCM 34 would cause the engine speed to overshoot past the offset and approach idle speed, the ECM 32 may artificially delay the response to the request to minimize any such overshoot. Likewise, the RPM may be limited by a maximum to prevent any excessive engine speeds that may cause damage to engine component hardware.

Thus, the TCM 34 may be configured to open the input clutch to the transmission, enable the speed control mode within the ECM 32, and send a request of the desired engine speed to the ECM 32 such that the engine speed at the target gear matches the input clutch speed .

The ECM 32 may include an engine RPM control module 110 that may be distinct from the idle speed control system used to control system minimum limits and zero pedal torque. The use of two control modules can be useful so that the driver demand system can generate a demand as if the shift were not in progress and apply torque intervention requesting devices can transmit their desired axle torque to the TCM 34 via the non-trans regulated torque.

Prior to the speed adjustment request, the TCM 34 may make a torque request to the ECM 32 such that it transitions the torque to a more neutral point that may optimize axle torque feel while the clutch opens. During the speed adjust request, the TCM 34 sets a torque request equal to the engine torque reported by the ECM and, when subsequently transitioning from the speed adjust, transitions that torque to the non-transmission regulated steady-state torque. During the speed adapt operation, the ECM 32 may ignore the torque requests of the TCM in order to complete the shift at the end of the event.

The ECM 32 may apply a directional limit to the intervening speed controller torque that may be requested. Likewise, if above a target torque amount, the TCM 34 may apply a maximum torque limiter.

The TCM 34 may include an abort system if the engine speed does not converge to the target value in an appropriate amount of time and controls the torque to the driver with his torque request and applies the input clutch more slowly.

7 FIG. 3 illustrates a method 300 for commanding a synchronous gear shift in a vehicle powertrain, in the manner described above. As shown, the method 300 begins upon receipt of a request to shift from a third gear to a first gear (step 302). As will be appreciated, the terms "third" and "first" are used as generic numeric designations referring to any two gears within the powertrain that are separated by at least one intermediate gear having a gear ratio between that of first and third Has gangs can relate. After the request in step 302, the TCM 34 may reduce a commanded torque to a predetermined value in preparation for a shift (step 304). The TCM 34 may open a clutch disposed on the input shaft of the transmission 16 to decouple the transmission 16 from the engine 12 (in step 306). The TCM 34 may then transition the engine 12 from a torque control mode to a speed control mode indicating this to the speed control module 111 of the ECM 32 (step 308). The TCM 34 may command the engine 12 to rotate at a speed dictated by vehicle motion and the first gear ratio, such that the engine speed would then match the input shaft speed of the transmission 16 in first gear (Step 310). The TCM 34 may then close the clutch to couple the transmission 16 to the engine 12 (step 312). Finally, the TCM 34 may transition the engine 12 back into torque control mode (step 314) and gradually transition the torque intervention to the driver requested pedal torque.

Although the techniques and methodologies disclosed herein have been described generally with reference to a dual clutch transmission, they are equally applicable and can be used with any manual transmission (MTA) or other similarly configured transmission that may rely on synchronous speed-adapting gear shifts these are used.

Claims (9)

A method of commanding a synchronous gear shift in a vehicle powertrain including an engine (12) and a transmission (16) having a plurality of ordered gears, the method comprising: receiving a request to shift from a third gear to a first gear and to skip a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear; reducing a torque command to a predetermined value; opening a clutch (74,76) disposed on the input shaft (18) of the transmission (16) to decouple the transmission (16) from the engine (12); transitioning the engine (12) from a torque control mode to a speed control mode; commanding the engine (12), while in the speed control mode, to rotate at a speed dictated by movement of the vehicle and by the first gear ratio; closing the clutch to couple the transmission (16) and the engine (12); and transitioning the engine (12) back to torque control mode. procedure after claim 1 , wherein the prime mover (12) while in the torque control mode operates in response to a driver torque request; and wherein closing the clutch to couple the transmission (16) and the engine (12) includes closing the clutch for a period of time such that a torque of the input shaft (18) of the transmission (16) transitions to a torque that matches the driver torque request. procedure after claim 2 further comprising receiving the driver torque request continuously throughout the synchronous gear shift. procedure after claim 3 , further comprising arbitrating between the driver torque request and a transmission input shaft speed request. procedure after claim 1 wherein the torque command increases to a saturated intermediate torque maximum at an intermediate torque maximum during the speed control mode, and wherein the intermediate torque maximum includes a maximum amount of torque that can be produced by an engine (12) at a fixed airflow. procedure after claim 1 , wherein the torque command approaches zero prior to closing the clutch to couple the transmission (16) and the engine (12). procedure after claim 1 , further comprising ignoring an axle torque request during speed control mode. procedure after claim 1 wherein transitioning the engine (12) back into the torque control mode includes gradually transitioning the engine (12) back into the torque control mode over a period of time. procedure after claim 1 , wherein the torque command is a function of a driver acceleration request when the engine (12) is in the torque control mode.

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