Full clutch slip power shift of a dual clutch transmission

A system for operating a dual clutch transmission, including launch/creep controller, shift logic, and a clutch control assembly. The shift logic is configured to intercept a torque command including a target clutch torque from the launch/creep controller as it transmits the target clutch torque to the clutch assembly. The shift logic engages a preparation phase that increases torque on an on-coming clutch to a prefill torque. The shift logic then engages a torque phase that transfers torque between the off-going clutch and the on-coming clutch by simultaneously decreasing the off-going clutch torque and increasing the on-coming clutch torque. The off-going clutch and the on-coming clutch remain in a slipping state that maintains the target clutch torque during the transfer.

BACKGROUND

Vehicles incorporating automatic transmissions shift automatically between gears in the transmission in response to changes in a throttle input, often associated with adjustments to a linked accelerator pedal. When a driver adjusts the accelerator pedal, these changes affect the throttle input, and in turn results in adjusting automatic transmission operationally connected to an engine and responding to the throttle inputs to find the appropriate gear. There are different types of shifting scenarios including power on/off upshifting and power on/off downshifting. Power On shifting refers to shifting into a higher gear (upshifting) or a lower gear (downshifting) when the accelerator pedal is depressed. Power Off shifting refers to shifting into a higher gear (upshifting) or a lower gear (downshifting) when the accelerator pedal is released.

One form of automatic transmission utilizes a dual clutch in order to shift between gears. In these dual clutch transmissions, there is commonly an off-going clutch that is engaged to and driving the present gear and an on-coming clutch that is used to engage the gear to be shifted into (upshifting or downshifting). Complications in smooth shifting can arise during difficult shifting scenarios. Launch shifting occurs when a vehicle is accelerated from idle and a drive gear shift occurs during the launch itself. When the clutch overheats during a launch or an less than optimum gear is initially selected at launch, a power shift must typically disconnect on off-going gear and activate an on-coming gear. This may result in a torque disturbance to the transmission between the disconnect of the off-going clutch and the re-engagement of the on-coming clutch. This torque disturbance can result in a rough shift and undesirable performance. Similar torque disturbances may result when coming to a stop on a grade with the throttle on and a gear shift is necessitated. In such a situation, while the vehicle is creeping forward it may be necessary to downshift into a lower gear while still powering forward. Again, the disturbance in torque may result in a rough shift and undesirable performance.

It may be desirable for a solution that would reduce the disturbance in transmission torque during power launch shifting situations where environmental conditions or improper gear selection necessitate a gear shift. It would additionally be desirable for a technique that would further reduce transmission torque disturbances during situations where a vehicle may be creeping to a stop on a grade and a change in gear is indicated.

DETAILED DESCRIPTION

A dual clutch transmission in a commercial vehicle is disclosed with the capability to power shift between gears without breaking the output transmission torque while both clutches are in a continuously slipping state. Moreover, the disclosed shifting provides a quick and smooth shift quality even when shifting during a launch or when shifting when coming to a stop on a grade. To accomplish this, the dual clutch transmission may employ exemplary preparation phase techniques. In addition, the dual clutch transmission may employ exemplary power shift torque phase techniques in communication with a launch/creep controller to transfer from an off-going clutch to an on-coming clutch without breaking transmission torque.

A launch/creep controller generates a torque command that includes a target clutch torque. The shift logic intercepts this target clutch torque. The shift logic may implement an exemplary preparation phase technique that includes a pre-fill loading of the on-coming clutch to a pre-fill torque. The exemplary preparation phase may also include unlocking the off-going clutch. The shift logic may also employ an exemplary torque phase technique. The exemplary torque phase technique may increase torque to the on-coming clutch while simultaneously decreasing torque to the off-going clutch. The combination of the off-going clutch torque and the on-coming clutch torque is used to maintain the target clutch torque during the torque handover that transfers torque from the off-going clutch to the on-coming clutch. Both the off-going clutch and the on-coming clutch are maintained in a slipping state during the torque handover. This allows a quick and smooth transition between the off-going clutch and the on-coming clutch without a break in the target clutch torque during launch and creep shift scenarios.

Referring now toFIG. 1, an engine driveline assembly100for a vehicle is shown. The driveline assembly100generally may include an engine102connected to a dual clutch transmission assembly104by way of a crankshaft106. In an exemplary arrangement, the dual clutch transmission assembly104includes a clutch case108housing a first clutch110and a second clutch112. In this exemplary example, the first clutch110communicates with a first (outer) transmission shaft114and the second clutch112communicates with a second (inner) transmission shaft116. It should be understood that the illustrated first and second transmission shaft114,116arrangements are illustrative only and do not limit the present disclosure. A plurality of transmission gears118are in communication with the first and second transmission shafts114,116as well as a drivetrain120in order to selectively transfer drive from the engine102to the drivetrain120. In at least one exemplary illustration, even transmission gears122are in communication with the first transmission shaft114and therefore the first clutch110and the odd transmission gears124are in communication with the second transmission shaft116and therefore the second clutch112. A clutch control assembly126, including an integrated shift logic128, is in communication with the dual clutch transmission assembly104and with the engine102to control operation of the engine drive assembly and the selection of specific transmission gears118.

The shift logic128is in communication with a launch/creep controller130. The launch/creep controller130contains inputs from vehicle sensors such as a pedal sensor132and an engine speed sensor134. The launch/creep controller130utilizes inputs from the pedal sensor132and the engine speed sensor134in order to implement a target torque command136to engine controller138and the clutch control assembly126which is intercepted by the shift logic128to execute a power launch shift or a powered creep shift. The engine controller138utilizes this torque command136to control the engine102. Additionally, the engine controller138receives information from the engine102and sends a feedback signal140back to the launch/creep controller130. The torque command136and feedback signal140together form a torque command loop142from which a continuous and adaptive control of the engine102may be accomplished. The shift logic128is in communication with the launch/creep controller130to intercept the torque command136and/or the torque command loop142. The shift logic128intercepts the torque command136,142in order to receive a target clutch torque144embedded therein. The launch/creep controller130may implement power launch shifts or power creep shifts using a variety of decision making arrangements. In an exemplary approach the torque command loop142may be designated a creep loop when the pedal sensor132indicates a pedal depression less than a predetermined amount such as 25% with an engine speed sensor134indicating an engine speed above idle. A creep loop is a command loop142that moves a vehicle slowly forward on an incline as opposed to moving forward with intent to accelerate. Similarly, in another exemplary approach the torque command loop142may be designated a launch loop when the pedal depression is greater than a predetermined amount such as 25% and the engine speed sensor134indicates an accelerating engine102. A launch loop is a command loop142that is indicative of a vehicle moving forward with the intent to accelerate to speed.

In addition to the target clutch torque144, the shift logic128may also receive information from additional signals such as a clutch temperature signal146and a gear selection signal148from a gear selection logic149. The launch/creep controller130, the shift logic128and the gear selection logic149may be a portion of a transmission controller150in one exemplary example. The shift logic128utilizes these signals to allow instruct the clutch control assembly126on how and when to effectuate a shift between transmission gears122,124. In launch situations, the need to shift may arise when the on clutch (the clutch temperature signal146) starts to exceed a temperature threshold (e.g., beginning to overheat) and it is desirable for the transmission assembly104to launch on the other clutch. Additionally, in launch situations when a less than optimum gear is selected (in one example too high a gear initially selected) the need to shift may arise to move into a more appropriate gear. This may be important if the shift during launch is needed when the vehicle is on a steep grade. Also, during creeping to a halt on a steep grade it may be necessary to shift while the driver is still on the throttle. The shift logic128utilizes these inputs136,142,144,146,148in order to direct the clutch control assembly126. Although a selection of inputs have been identified for the shift logic128and launch/creep controller130, a plurality of additional inputs may be utilized in addition to those identified.

When the system recognizes a power launch or a power creep situation and the shift logic128indicates the necessity for a shift of gears, the clutch control assembly126must facilitate the transition between an off-going clutch and an on-coming clutch. In the above exemplary example, if an upshift from first gear to second gear is needed during a launch acceleration, the clutch control assembly126must transition from the first clutch (off-going)110to the second clutch (on-coming)112. This is accomplished by removing the torque from the off-going clutch and increasing torque on the on-coming clutch. However, during power launch shifts or powered creep shifts it is desirable to maintain a constant transmission torque on the drivetrain120. An exemplary method is provided that provides a quick and smooth transition between an off-going clutch and an on-coming clutch and maintains a torque on the drivetrain120.

Referring now toFIGS. 2, 3 and 4, the exemplary method for dual clutch transmission200is provided. For the purposes of simplicity, method steps (200) will refer toFIG. 2, elements (300) will refer toFIG. 3, and elements (400) will refer toFIG. 4.FIG. 3is an exemplary illustration of a shift from a first gear into second gear during a powered launch shift.FIG. 4is an exemplary illustration of a shift from second gear down to first gear during a powered creep shift. The method includes generating a torque command from a launch/creep controller202. The method further includes generating a gear selection command203. The torque command136includes a target clutch torque144indicative of the present torque provided to the driveline120. The method intercepts the torque command using the shift logic204. The shift logic than implements a preparation phase206. The preparation phase206increases torque on the on-coming gear to a pre-fill torque208. In the powered launch shift inFIG. 3, this adds pre-fill torque (302) to on-coming clutch112(300). In the powered creep shift inFIG. 4, this adds pre-fill torque (402) to on-coming clutch112(400). The pre-fill torque (302,402) maybe any value of baseline torque to prepare the on-coming clutch112. In an exemplary approach the pre-fill torque is contemplated to be a plate-touch-point torque which is the torque necessary for the plates on the clutch to touch. The preparation phase206also includes torque balancing210the off-going clutch110and the on-coming clutch112(400) relative to the engine torque (301,401). In the powered launch shift this unlocks off-going clutch110(304). In the powered creep shift this unlocks off-going clutch110(404).

The exemplary method200then has the shift logic204implement a torque phase212transferring toque from the off-going clutch to the on-coming clutch. The torque phase212increases torque on the on-coming clutch (300,400) towards the target clutch torque (306,406)214. Simultaneously, the torque phase212decreases torque on the off-going clutch (304,404)216. Both the on-coming clutch (300,400) and the off-going clutch (304,404) remain unlocked and in a slipping state during the torque phase212. The combination of the torque on the on-coming clutch (300,400) and the torque on the off-going clutch (304,404) maintains the target clutch torque (306,406) throughout the torque phase212. This allows the drivetrain120to be supplied with unbroken torque during the handover from the off-going clutch (304,404) to the on-coming clutch (300,400).

The exemplary method may also include a post phase218implemented by the shift logic. The post phase218increases torque on the on-coming clutch (300,400) until it matches the target clutch torque (306,406)220. In one exemplary approach, this is accomplished by generating a torque command loop from the launch/creep controller222and continuously intercepting the torque command loop to update the target clutch torque224. The torque on the on-coming clutch (300,400) is continuously adjusted to match the updated target clutch torque226. The off-going clutch (304,404) is decreased in torque until it disconnects228. This allows the on-coming clutch (300,400) to continuously adjust to the target clutch torque (306,406) as the vehicle continued on the launch or creep in the new gear.

The exemplary method set forth above provides a way to shift without significantly disturbing the torque to the driveshaft during launches and creeping to a stop on a grade. It accomplishes this by allowing both on-coming and off-going clutches to slip during the transfer such that their combined torques maintain a smooth and consistent transmission torque during the handover.

It should be understood that the shift logic128, the launch/creep controller130, and the engine controller138may include computer-executable instructions such as the instructions of the software applications on a processor, where the instructions may be executable by one or more computing devices. In general, a processor (e.g., a microprocessor) receives instructions, e.g., from a memory, a non-transitory computer-readable medium, etc., and executes these instructions, thereby performing one or more processes, including one or more of the processes described herein. Such instructions and other data may be stored and transmitted using a variety of computer-readable media. Computing systems and/or devices generally include computer-executable instructions, where the instructions may be executable by one or more devices such as those listed below. Computer-executable instructions may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java™, C, C++, Visual Basic, Java Script, Perl, etc. The shift logic129, the launch/creep controller130, and the engine controller138may take many different forms and include multiple and/or alternate components and facilities. Indeed, additional or alternative components and/or implementations may be used, and thus the above controller examples should not be construed as limiting.