FULL CLUTCH SLIP POWER SHIFT OF A DUAL CLUTCH TRANSMISSION
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This Application claims the benefit of U.S. Provisional Application No.
611938,317 filed on February 11,2014 and U.S. Utility Application No. 141590,324 filed
January 6,2015 which are hereby incorporated by reference in their entirety.
BACKGROUND
[0002] 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 odoff
upshifting and power odoff downshifting. Power On shifting refers to shifting into a higher
gear (upshifting) or a lowcr gear (downshifting) whcn the accelerator pedal is depresscd.
Power Off shifting refers to shifting into a higher gear (upshifting) or a lower gear
(downshifting) when the accelerator pedal is released.
[0003] 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 thc prescnt gear and an on-coming clutch that is uscd to engagc 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 a 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 pcrformancc. Similar torque disturbanccs may rcsult 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 fonwd it may be necessary to downshift into a lower gear while still
powcring fonvard. Again, the disturbancc in torquc may rcsult in a rough shift and
undesirable performance.
(00041 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 vchicle may bc creeping to a stop on a gradc and a change in gcar is indicated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Refemng now to the drawings, exemplary illustrations are shown in detail.
Although the drawings represent representative examples, the drawings are not necessarily to
scalc and certain features may bc cxaggcrated to bcttcr illustrate and cxplain an innovative
aspect of an illustrative example. Further, the exemplary illustrations described herein are
not intended to be exhaustive or otherwise limiting or restricting to the precise fonn and
configuration shown in the drawings and disclosed in the following detailed description.
Exemplary illustrations are described in detail by referring to the drawings as follows:
I00061 FIG. 1 is an exemplary illustration of a dual clutch transmission;
[0007] FIG. 2 is a diagram illustrating an exempla~m ethod of controlling a dual clutch
transmission;
100081 FIG. 3 is a graphical illustration of the exemplw method shown in Figure 2
indicating a power launch shift; and
(0009) FIG. 4 is a graphical illustration of the exemplary method shown in Figure 2
indicating a creep downshift.
DETAILED DESCRIPTION
I00101 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 prcparation phase tcchniqucs. In addition, the dual clutch transmission may
employ exemplary power shift torque phase techniques in communication with a
launchtcreep controller to transfer from an off-going clutch to an oncoming clutch without
breaking transmission torque.
1001 11 A launchtcreep 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 cxcmplv prcparation phasc technique that includes a prc-fill loading of thc
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 thc targct clutch torque
during launch and creep shift scenarios.
[0012] Referring now to FIG. 1, an engine driveline assembly 100 for a vehicle is shown.
The driveline assembly 100 generally may include an engine 102 connected to a dual clutch
transmission assembly 104 by way of a crankshaft 106. In an exemplary arrangement, the
dual clutch transmission assembly 104 includes a clutch case 108 housing a first clutch 1 10
and a second clutch 112. In this exemplary example, the first clutch 110 communicates with
a first (outer) transmission shafi 114 and thc second clutch 112 communicates with a sccond
(inner) transmission shaft 116. It should be understood that the illustrated first and second
transmission shaft 114, 116 arrangements are illustrative only and do not limit the present
disclosure. A plurality of transmission gears 1 18 are in communication with the first and
second transmission shafts 114, 116 as well as a drivetrain 120 in order to selectively transfer
drive from the engine 102 to the drivetrain 120. In at least one exemplary illustration, even
transmission gears 122 are in communication with the first transmission shaft 114 and
therefore the first clutch 1 10 and the odd transmission gears 124 are in communication with
the second transmission shaft 1 16 and therefore the second clutch 112. A clutch control
assembly 126, including an intcgrated shift logic 128, is in communication with the dual
clutch transmission assembly 104 and with thc engine 102 to control operation ofthe enginc
drive assembly and the selection of specific transmission gears 1 18.
I00131 The shift logic 128 is in communication with a launch/creep controller 130. The
launchkreep controller 130 contains inputs from vehicle sensors such as a pedal sensor 132
and an engine speed sensor 134. The 1auncWcreep controller 130 utilizes inputs from the
pedal sensor 132 and the engine speed sensor 134 in order to implement a target torque
command 136 to enginc controller 138 and thc clutch control assembly126 which is
intercepted by the shift logic 128 to execute a power launch shift or a powered creep shift.
The engine controller 138 utilizes this torque command 136 to control the engine 102.
Additionally, the engine controller 138 receives information from the engine 102 and sends a
feedback signal 140 back to the 1auncWcreep controller 130. The torque command 136 and
feedback signal 140 together form a torque command loop 142 from which a continuous and
adaptive control of the engine 102 may be accomplished. The shlft logic 128 is in
communication with the 1auncWcreep controller 130 to intercept the torque command 136
and/or the torque command loop 142. The shift logic 128 intercepts the torque command
136,142 in order to receive a target clutch torque 144 embcddcd therein. Thc launch/crcep
controller 130 may implement power launch shifts or power creep shifts using a variety of
decision making arrangements. In an exemplary approach the torque command loop 142 may
be designated a creep loop when the pedal sensor 132 indicates a pedal depression less than a
predetermined amount such as 25% with an engine speed sensor 134 indicating an engine
speed above idle. A creep loop is a command loop 142 that 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 loop 142 may be designated a launch loop when the
pedal depression is greater than a predetermined amount such as 25% and the engine speed
sensor 134 indicates an accelerating engine 102. A launch loop is a command loop 142 that
is indicative of a vehicle moving fonvard with the intent to accelerate to speed.
[0014] In addition to the target clutch torque 144, the shift logic 128 may also receive
information from additional signals such as a clutch temperature signal 146 and a gear
selection signal 148 from a gear selection logic 149. The launch/creep controller 130, the
shift logic 128 and the gear selection logic 149 may be a portion of a transmission controller
150 in one exemplary example. The shift logic 128 utilizes these signals to allow instruct the
clutch control asscmtly 126 on how and when to effcctuatc a shift between transmission
gears 122,124. In launch situations, the necd to shift may arise when the on clutch (thc clutch
temperature signal 146) starts to exceed a temperature threshold (e.g., beginning to overheat)
and it is desirable for the transmission assembly 104 to 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 necessan to shift
while the driver is still on the throttle. The shift logic 128 utilizes these inputs 136. 142, 144,
146, 148 in order to direct the clutch control assembly 126. Although a selection of inputs
have been idcntificd for the shift logic 128 and launch/creep controller 130, a pluralih of
additional inputs may be utilized in addition to those identified.
[015] When the system recognizes a power launch or a power creep situation and the
shift logic 128 indicates the necessity for a shift of gears, the clutch control assembly 126
must facilitate the transition behveen an off-going clutch and an on-coming clutch. In the
above exemplar)l example, if an upshift fiom first gear to second gear is needed during a
' launch acceleration, thc clutch control assembly 126 must transition from the first clutch (offgoing)
1 10 to the second clutch (on-corning) 1 12. 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 drivetrain 120. An exemplary method is provided that provides a
quick and smooth transition behveen an off-going clutch and an on-coming clutch and
maintains a torque on the drivetrain 120.
[0016] Rcfcrring now to FIGS. 2,3 and 4, the cxemplary method for dual clutch
transmission 200 1s provided. For the purposes of simplicity, method steps (200) will refer to
Figure 2, elements (300) will refer to Figure 3, and elements (400) will refer to Figure 4.
Figure 3 is an exempla~il lustration of a shift from a first gear into second gear during a
powered launch shift. Figure 4 is an esemplary 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 launchfcreep controller 202. The method further includes generating a gear
selection command 203. The torque command 136 includes a target clutch torque 144
indicative of the present torque procided to the driveline 120. The method intercepts the
torque command using the shift logic 204. The shift logic than implcmcnts a preparation
phasc 206. Thc preparation phasc 206 incrcascs torquc on the on-corning gcar to a prc-fill
torque 208. In the powercd launch shift in Figure 3, this adds pre-fill torque (302) to oncoming
clutch 112 (300). In the powered creep shift in Figure 4, this adds pre-fill torque
(402) to on-coming clutch 112 (400). The pre-fill torque (302,402) maybe any value of
baseline torque to prepare the on-coming clutch 112. 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 phase 206 also includes torque balancing 210
the off-going clutch 1 10 and the on-coming clutch 1 12 (400) relative to the engine torque
(301,401). In the powered launch shift this unlocks off-going clutch 110 (304). In the
powercd creep shift this unlocks off-going clutch 1 10 (404).
[0017] The exemplary method 200 then has the shift logic 204 implement a torque phase
2 12 transferring toque from the off-going clutch to the on-corning clutch. The torque phase
2 12 increases torque on the on-corning clutch (300.400) towards the target clutch torque
(306,406) 214. Simultaneously, the torque phase 212 decreases torque on the off-going
clutch (304,404) 216. Both the on-corning clutch (300,400) and the off-going clutch (304,
404) remain unlocked and in a slipping statc during thc torquc phase 2 12. Thc 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 phase 212. This
allows the drivetrain 120 to be supplied with unbroken torque during the handover from the
off-going clutch (304,404) to the on-coming clutch (300,400).
[0018] The exemplary method may also include a post phase 2 18 implemented by the
shift logic. The post phase 21 8 increases torque on the on-coming clutch (300,400) until it
matches the targct clutch torque (306,406) 220. In onc exemplary approach, this is
accomplished by generating a torque command loop from the launch/crcep controller 222 and
continuously intercepting the torque command loop to update the target clutch torque 224.
The torque on the on-corning clutch (300,400) is continuously adjusted to match the updated
target clutch torque 226. The off-going clutch (304,404) is decreased in torque until it
disconnects 228. 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.
[0019] Thc cscmplary 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.
[0020] Accordingly, it is to be understood that the above description is intended to be
illustrativc and not rcstrictivc. Many embodiments and applications other than the cxamplcs
provided would be apparent upon reading the above description. The scope should be
determined, not with reference to the above description, but should instead be determined
with reference to the appended claims, along with the full scope of equivalents to which such
claims are entitled. It is anticipated and intended that future developments will occur in the
technologies discussed herein, and that the disclosed systems and niethods will be
incorporated into such future embodiments. In sum, it should be understood that the
application is capable of modification and variation.
(00211 All terms used in the claims are intended to be given their broadest reasonable
constructions and their ordinary meanings as understood by those knowledgeable in the
technologies described herein unless an explicit indication to the contraq is made herein. In
particular, use of the singular articles such as "'a," "'the," "said," etc. should be read to recite
one or more of the indicated elements unless a claim recites an explicit limitation to the
contrap.
100221 It should be understood that the shift logic 128, the launchlcreep controller 130,
and the engine controller 138 may 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 computerreadable
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 andlor devices generally include computer-executable instructions,
where the instructions may bc executable by one or more devices such as thosc listed below.
Computer-executable instructions may be compiled or interpreted from computer programs
creatcd using a varicty of programming languages and/or technologies, including, without
limitation, and either alone or in combination, Javar*, C, C++, Visual Basic, Java Script,
Perl, etc. The shift logic 129, the IaunchJcreep controller 130, and the engine controller 138
may take many different forms and include multiple andlor 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.
I00231 The Abstract of thc Disclosurc is provided to allow the readcr to quickly ascertain
the nature of the technical disclosure. It is submitted with the understanding that it will not
be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing
Detailed Description, it can be seen that various features are grouped together in various
embodiments for the purpose of streamlining the disclosure. This method of disclosure is not
to be interpreted as reflecting an intention that the claimed embodiments require more
features than are expressly recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single disclosed embodiment. Thus,
the following claims are hereby incorporated into the Detailed Description, with each claim
standing on its own as a separately claimcd subject matter.

We claim:
I . A method of controlling a dual clutch transmission, including an on-coming clutch
and an off-going clutch, comprising:
gcncrating a torque command from a launch/crecp controller, the torquc command
including a target clutch torque;
intercepting the torque command using a shift logic;
implementing a preparation phase comprising:
increasing torque on the on-coming clutch to a prefill torque:
implementing a torque phase transfening torque from the off-go~ngc lutch to the oncoming
clutch, the torque phase comprising:
increasing torque on the on-coming clutch towards the target clutch torque,
said oncoming clutch remaining unlocked during the transfer; and
decreasing torque on the off-going clutch, said off-going clutch remaining
unlocked during the transfer,
wherein as the off-going clutch torque is decreasing. the combination of the
on-coming clutch torque added to the off-going clutch torque maintains the target clutch
torquc.
2. A method of controlling a dual clutch transmission as described in claim 1, further
comprising:
implementing a post phase comprising:
increasing torque on the on-coming clutch until it matches the target clutch
torque; and
decreasing torquc on thc off-going clutch until thc off-going clutch
disconnects.
3. A method of controlling a dual clutch transmission as described in claim 2: wherein
the post phase comprises:
generating a torque command loop fiom the launchlcreep controller;
continuously intercepting the torque command loop to update the target clutch
torque by thc shift logic; and
continuously adjusting torque on the on-coming clutch to match the updated target
clutch torque.
4. A method of controlling a dual clutch transmission as described in claim 1, wherein
the off-going clutch and the on-coming clutch remain in a slipping state during the torque
phase.
5. A method of controlling a dual clutch transmission as described in claim 1, wherein
the shift logic is in commuilication with a clutch temperature signal, said shift logic
implementing the torque phase in response to the clutch temperature signal.
6. A method of controlling a dual clutch transmission as described in claim 1, wherein
the shift logic is in communication with a gear selection signal, said shift logic implementing
the torque phase in response to the gear selection signal.
7. A mcthod of controlling a dual clutch transmission as dcscribcd in claim 3: whcrcin
the torque command loop comprises a creep loop when a pedal signal is bclow a
predetermined value.
8. A method of controlling a dual clutch transmission as described in claim 3, wherein
the torque command loop comprises a launch loop when a pedal signal is above a
predetermined value.
9. A dual clutch transmission comprising:
a launchlcreep controller configured to generate torque a command including a target
clutch torque;
a first clutch;
a second clutch;
a clutch control assembly in communication with said launchlcreep controller, said
first clutch, and said second clutch, said clutch control assembly including a shift logic
configured to intercept said torque command from said launchlcreep controller, said shift
logic configured to power shift by:
implement a torque phase transfening torque from the first clutch to the second
clutch, the torque phase comprising:
increasing torque on the second clutch towards the target clutch torque; and
simultaneously decreasing torque on the first clutch;
wherein the first clutch and the second clutch are both in a slipping state that
maintains the target clutch torque during the transfer.
10. A dual clutch transmission as described in claim 9, wherein said shift logic is fiirther
configured to:
implementing a preparation phase prior to said torque phase comprising:
increasing torque on the second clutch to a prefill torque.
11. A dual clutch transmission as described in claim 10, wherein said preparation phase
hrther comprises:
torque balancing thc first clutch and thc second clutch.
12. A dual clutch transmission as described in claim 9, wherein said prefill torque
comprises a plate-touch-point torque.
13. A dual clutch transmission as described in claim 9, wherein said shift logic is further
configured to:
implcmcnt a post phase comprising:
increasing torque on the second clutch until it matches the target clutch torque;
and
decreasing torque on the first clutch until the first clutch disconnects.
14. A dual clutch tmsmission as described in claim 13, wherein the post phase
comprises:
generating a torque command loop from the launch/creep controller;
continuously intercepting the torque command loop to update the target clutch
torque; and
continuously adjusting torquc on thc sccond clutch to match the updatcd targct
clutch torque.
15. A dual clutch transmission as described in claim 9, wherein said shift logic is in
communication with a clutch temperature signal, said shift logic implementing said torque
phase in response to said clutch temperature signal indicating an overheating transmission.
16. A dual clutch transmission as described in claim 9, whcrcin said shift logic is in
communication with a gear selection signal, said shift logic implementing said torque phase
in response to said gear selection signal indicating a wrong gear selection.
17. A dual clutch transmission as described in claim 13, wherein said first clutch and said
second clutch remain unlocked during said post phase.
18. A system for operating a dual clutch transmission, including 1aunchJcreep controller
and a clutch control assembly including a shift logic. the clutch control assembly configured
to:
intercept a torque command from the launch/creep controller using the shift logic, the
torque command including a target clutch torque, ;
engage a preparation phase comprised of
increasing torque on an on-corning clutch to a prefill torque;
engage a torque phase comprising:
transferring torque between said off-going clutch and said on-corning clutch
by simultaneously decreasing the off-going clutch torque and increasing the oncoming
clutch torquc, whcrcin said off-going clutch and said on-coming clutch arc
both in a slipping state that maintains the target clutch torque during the transfer.
19. A system as described in claim 18, wherein said clutch control assembly is further
configured to:
implement a post phase comprising:
increasing torque on the on-coming clutch until it matches the target clutch
torquc: and
decreasing torque on the off-going clutch until the off-going clutch
disconnects.
20. A system as described in claim 19, wherein the post phase further comprises:
generating a torque command loop from the launch/creep controller:
continuously intercepting the torque command loop to update the target clutch
torquc; and
continuously adjusting torque on the on-coming clutch to match the updated
target clutch torque.