U.S. patent application number 16/531627 was filed with the patent office on 2020-10-01 for shifting control method for vehicle with dct.
This patent application is currently assigned to Hyundai Motor Company. The applicant listed for this patent is Hyundai Motor Company, Kia Motors Corporation. Invention is credited to Sung Hyun Cho, Su Hwan Lee.
Application Number | 20200307601 16/531627 |
Document ID | / |
Family ID | 1000004259579 |
Filed Date | 2020-10-01 |
United States Patent
Application |
20200307601 |
Kind Code |
A1 |
Cho; Sung Hyun ; et
al. |
October 1, 2020 |
SHIFTING CONTROL METHOD FOR VEHICLE WITH DCT
Abstract
A shift control method of a vehicle with a dual clutch
transmission (DCT) may include: a first preparing step of, by a
controller, controlling a torque of an N-th stage clutch to a
predetermined minimum torque and increasing a torque of an N-1-th
stage clutch to a predetermined standby torque; a first handover
step of releasing the torque of the N-th stage clutch and
increasing the torque of the N-1-th stage clutch; a gear changing
step of releasing an N-th stage gear and then initiating an
engagement of an N-2-th stage gear; a synchronization maintaining
step of maintaining a synchronized state by adjusting the torque of
the N-1-th stage clutch; a second preparing step of increasing the
torque of the N-2-th stage clutch to the standby torque; and a
second handover step of releasing the torque of the N-1-th clutch
and increasing the torque of the N-2-th stage clutch.
Inventors: |
Cho; Sung Hyun; (Yongin-si,
KR) ; Lee; Su Hwan; (Hwaseong-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Motors Corporation |
Seoul
Seoul |
|
KR
KR |
|
|
Assignee: |
Hyundai Motor Company
Seoul
KR
Kia Motors Corporation
Seoul
KR
|
Family ID: |
1000004259579 |
Appl. No.: |
16/531627 |
Filed: |
August 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16H 2306/54 20130101;
B60W 2710/027 20130101; B60W 30/19 20130101; B60Y 2300/19 20130101;
B60W 10/02 20130101; F16H 61/682 20130101; F16H 61/0403 20130101;
F16H 61/0437 20130101; B60W 2510/0638 20130101; F16H 2059/462
20130101; B60W 10/113 20130101; F16H 59/46 20130101; F16H 2306/48
20130101; B60W 2710/1005 20130101 |
International
Class: |
B60W 30/19 20060101
B60W030/19; B60W 10/02 20060101 B60W010/02; B60W 10/113 20060101
B60W010/113; F16H 61/04 20060101 F16H061/04; F16H 61/682 20060101
F16H061/682; F16H 59/46 20060101 F16H059/46 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 26, 2019 |
KR |
10-2019-0034206 |
Claims
1. A shift control method of a vehicle mounted with a dual clutch
transmission (DCT), the shifting control method comprising: a first
preparing step of, by a controller, controlling a torque of an N-th
stage clutch to a predetermined minimum torque and increasing a
torque of an N-1-th stage clutch to a predetermined standby torque,
in a response that a same-shaft power on down shift is initiated
and an engagement of an N-1-th stage gear is completed; a first
handover step of, by the controller, releasing the torque of the
N-th stage clutch and increasing the torque of the N-1-th stage
clutch, in a response that the torque of the N-1-th stage clutch
reaches the predetermined standby torque and a rotation speed of an
engine is equal to or greater than a speed of the N-1-th stage
clutch; a gear changing step of, by the controller, releasing an
N-th stage gear and then initiating an engagement of an N-2-th
stage gear; a synchronization maintaining step of, by the
controller, maintaining a synchronized state by adjusting the
torque of the N-1-th stage clutch in a response that it is
determined by the controller that the rotation speed of the engine
is synchronized with a speed of the N-2-th stage clutch; a second
preparing step of, by the controller, increasing the torque of the
N-2-th stage clutch to the predetermined standby torque in a
response that the engagement of the N-2-th stage gear is completed;
and a second handover step of, by the controller, releasing the
torque of the N-1-th clutch and increasing the torque of the N-2-th
stage clutch, in a response that the torque of the N-2-th stage
clutch reaches the predetermined standby torque.
2. The shifting control method of claim 1, wherein the controller
is configured to determine when an inter-stage ratio between an
N-th stage, which is a current stage, and an N-2-th stage, which is
a final target stage, is equal to or greater than a predetermined
reference inter-stage ratio, before the first preparing step, and
is configured to perform the first preparing step in a response
that the inter-stage ratio is equal to or greater than the
predetermined reference inter-stage ratio.
3. The shifting control method of claim 1, wherein the controller
is configured to determine when a current shifting is a shifting
situation during shifting before the first preparing step, and is
configured to perform the first preparing step in a response that
the current shifting is not the shifting situation during
shifting.
4. The shifting control method of claim 1, wherein in the first
handover step, the controller is configured to increase the torque
of the N-1-th stage clutch at a predetermined first slope while
releasing the torque of the N-th stage clutch during a
predetermined first target time.
5. The shifting control method of claim 1, wherein in the gear
changing step, the controller is configured to release the N-stage
gear and initiates the engagement of the N-2-th gear, after
completely releasing the torque of the N-th stage clutch.
6. The shifting control method of claim 5, wherein the controller
is configured to increase the torque of the N-1-th stage clutch in
succession to the first handover step during the gear changing
step.
7. The shifting control method of claim 1, wherein in the
synchronization maintaining step, the controller is configured to
feedback-control the torque of the N-1-th stage clutch to maintain
the synchronized state.
8. The shifting control method of claim 1, wherein the controller
is configured to verify when the rotation speed of the engine
maintains a state synchronized with the speed of the N-2-th stage
clutch for a predetermined time in a response that the torque of
the N-2-th stage clutch reaches the predetermined standby torque,
and is configured to perform the second handover step in a response
that the synchronized state is maintained.
9. The shifting control method of claim 1, wherein in the second
handover step, the controller is configured to increase the torque
of the N-2-th stage clutch at a predetermined second slope while
releasing the torque of the N-1-th stage clutch during a
predetermined second target time.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority to Korean Patent
Application No. 10-2019-0034206, filed Mar. 26, 2019, the entire
contents of which is incorporated herein for all purposes by this
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a shifting control method
for a vehicle with a dual clutch transmission (DCT), and more
particularly, to a technology for a control method of same-shaft
shifting.
Description of Related Art
[0003] In a dual clutch transmission (DCT), one of two clutches is
mounted to implement an odd-numbered shifting stage of a series of
shifting stages and the other is mounted to implement an
even-numbered shifting stage. In a state in which a gear of a
target shifting stage is previously engaged, shifting is performed
by engaging a clutch (hereinafter, referred to as a coupling
clutch) for the target shifting stage while releasing a clutch
(hereinafter, referred to as a releasing clutch) for a current
shifting stage, preventing torque interruption and improving
shifting quality during the shifting. This is called so-called
"different-shaft shifting".
[0004] In a case of "same-shaft shifting" in which two shift stags
are to be shifted at once in the DCT as described above, i.e., a
case in which the shifting is to be performed from the odd-numbered
shifting stage to the odd-numbered shifting stage, or from the
even-numbered shifting stage to the even-numbered shifting stage,
the shifting to the target shifting stage is not directly performed
due to a hardware structure as described above, and the shifting is
performed by sequentially performing the above-mentioned
different-shaft shifting in which the shifting is performed from
the odd-numbered shifting stage to the even-numbered shift stage,
or from the even-numbered shifting stage to the odd-numbered
shifting stage.
[0005] Therefore, since the same-shaft shifting of the DCT is
always implemented by sequentially performing different-shaft
shifting, responsiveness thereof is lower than that of an automatic
transmission using a conventional planetary gear train and friction
elements.
[0006] Meanwhile, a power on down shift means that the shifting is
performed to a lower shifting stage in a state in which a driver
steps on an accelerator pedal.
[0007] The information included in this Background of the Invention
section is only for enhancement of understanding of the general
background of the invention and may not be taken as an
acknowledgement or any form of suggestion that this information
forms the prior art already known to a person skilled in the
art.
BRIEF SUMMARY
[0008] Various aspects of the present invention are directed to
providing a shifting control method of a vehicle with a dual-clutch
transmission (DCT) configured for ultimately improving a commercial
value of a vehicle by improving shifting responsiveness to minimize
disadvantages of the DCT at the time of a same-shaft power one down
shift by an accelerator pedal operation of a driver in a
DCT-provided vehicle.
[0009] According to an exemplary embodiment of the present
invention, a shift control method of a vehicle with a dual clutch
transmission (DCT) may include: a first preparing step of, by a
controller, controlling a torque of an N-th stage clutch to a
predetermined minimum torque and increasing a torque of an N-1-th
stage clutch to a predetermined standby torque, when a same-shaft
power on down shift is initiated and an engagement of an N-1-th
stage gear is completed; a first handover step of, by the
controller, releasing the torque of the N-th stage clutch and
increasing the torque of the N-1-th stage clutch, when the torque
of the N-1-th stage clutch reaches the standby torque and a
rotation speed of an engine is equal to or greater than a speed of
the N-1-th stage clutch; a gear changing step of, by the
controller, releasing an N-th stage gear and then initiating an
engagement of an N-2-th stage gear; a synchronization maintaining
step of, by the controller, maintaining a synchronized state by
adjusting the torque of the N-1-th stage clutch when it is
determined that the rotation speed of the engine is synchronized
with a speed of the N-2-th stage clutch; a second preparing step
of, by the controller, increasing the torque of the N-2-th stage
clutch to the standby torque when the engagement of the N-2-th
stage gear is completed; and a second handover step of, by the
controller, releasing the torque of the N-1-th clutch and
increasing the torque of the N-2-th stage clutch, when the torque
of the N-2-th stage clutch reaches the standby torque.
[0010] The controller may be configured to determine whether an
inter-stage ratio between an N-th stage, which is a current stage,
and an N-2-th stage, which is a final target stage, is equal to or
greater than a predetermined reference inter-stage ratio, before
the first preparing step, and perform the first preparing step only
when the inter-stage ratio is equal to or greater than the
predetermined reference inter-stage ratio.
[0011] The controller may be configured to determine whether or not
a current shifting is a shifting situation during shifting before
the first preparing step, and perform the first preparing step only
when the current shifting is not the shifting situation during
shifting.
[0012] In the first handover step, the controller may increase the
torque of the N-1-th stage clutch at a predetermined first slope
while releasing the torque of the N-th stage clutch during a
predetermined first target time.
[0013] In the gear changing step, the controller may release the
N-stage gear and initiate the engagement of the N-2-th gear, after
completely releasing the torque of the N-th stage clutch.
[0014] The controller may increase the torque of the N-1-th stage
clutch in succession to the first handover step during the gear
changing step.
[0015] In the synchronization maintaining step, the controller may
feedback-control the torque of the N-1-th stage clutch to maintain
the synchronized state.
[0016] The controller may confirm whether or not the rotation speed
of the engine maintains a state synchronized with the speed of the
N-2-th stage clutch when the torque of the N-2-th stage clutch
reaches the standby torque, and perform the second handover step
only when the synchronized state is maintained.
[0017] In the second handover step, the controller may increase the
torque of the N-2-th stage clutch at a predetermined second slope
while releasing the torque of the N-1-th stage clutch during a
predetermined second target time.
[0018] The methods and apparatuses of the present invention have
other features and advantages which will be apparent from or are
set forth in more detail in the accompanying drawings, which are
incorporated herein, and the following Detailed Description, which
together serve to explain certain principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a schematic diagram of a DCT-provided vehicle to
which an exemplary embodiment of the present invention may be
applied;
[0020] FIG. 2 is a flowchart illustrating an exemplary embodiment
of a shift control method of a vehicle with a DCT according to an
exemplary embodiment of the present invention; and
[0021] FIG. 3 is a diagram representing, as a graph, the shift
control method of a vehicle with a DCT according to an exemplary
embodiment of the present invention.
[0022] It may be understood that the appended drawings are not
necessarily to scale, presenting a somewhat simplified
representation of various features illustrative of the basic
principles of the present invention. The specific design features
of the present invention as included herein, including, for
example, specific dimensions, orientations, locations, and shapes
will be determined in part by the particularly intended application
and use environment.
[0023] In the figures, reference numbers refer to the same or
equivalent portions of the present invention throughout the several
figures of the drawing.
DETAILED DESCRIPTION
[0024] Reference will now be made in detail to various embodiments
of the present invention(s), examples of which are illustrated in
the accompanying drawings and described below. While the present
invention(s) will be described in conjunction with exemplary
embodiments of the present invention, it will be understood that
the present description is not intended to limit the present
invention(s) to those exemplary embodiments. On the other hand, the
present invention(s) is/are intended to cover not only the
exemplary embodiments of the present invention, but also various
alternatives, modifications, equivalents and other embodiments,
which may be included within the spirit and scope of the present
invention as defined by the appended claims.
[0025] FIG. 1 is a configuration example of a vehicle with a dual
clutch transmission (DCT) to which the present invention may be
applied. Power of an engine E may be provided to driving wheels W
through the DCT. An odd-numbered clutch CL1 and an even-numbered
clutch CL2, which are two clutches configuring the DCT, are
controlled by an odd-numbered clutch actuator CA1 and an
even-numbered clutch actuator CA2, respectively, and shifting gears
forming the each shifting stage are shifted by a shift actuator SA
that selects and drives the synchronizers.
[0026] The actuators are controlled by a controller 5, and the
controller 5 is connected to an accelerator position sensor (APS) 7
for receiving an operation amount of an accelerator pedal, and is
connected to a brake pedal sensor (BPS) 9 for receiving an
operation amount of a brake pedal.
[0027] In addition to this, the controller 5 receives information
such as a transmission range selection state, an engine torque, an
engine speed, and the like.
[0028] Meanwhile, the engine is controlled by a separate engine
management system (EMS), and the controller 5 communicates with the
EMS to receive information related to the engine. When the engine
requests the EMS to adjust torque of the engine in accordance with
a running situation and a shifting situation of the vehicle, the
EMS controls the engine in a response to the request.
[0029] For reference, the controller 5 as described above may be
configured as a transmission management system (TMS). In some
cases, the controller 5 may be configured as an integrated control
system that integrates the EMS and the TMS.
[0030] Here, the "controller" simply means a controller that is
configured to control the DCT.
[0031] During the shifting, one of the odd-numbered clutch CL1 and
the even-numbered clutch CL2 performs a releasing action and the
other thereof performs a coupling action. Therefore, depending on a
shifting situation, one of the two clutches is a releasing clutch
and the other thereof is a coupling clutch.
[0032] However, since the shifting is performed from an N-th stage,
which is a current stage, to a final target stage, which is an
N-2-th stage, and an N-1-th stage, which is an intermediate target
stage, is present, there is a possibility of confusion when using
terms of the coupling clutch and the releasing clutch as described
above. Therefore, hereinafter, a clutch that transfers the power
when running in the N-th stage will be referred to as an N-th stage
clutch, a clutch that transfers the power when running in the
N-1-th stage will be referred to as an N-1-th stage clutch, and a
clutch that transfers the power when running in the N-2-th stage
will be referred to as an N-2-th stage clutch.
[0033] For example, when the current shifting stage is a third
stage, the N-th stage means the third stage, and the N-th stage
clutch means an odd-numbered clutch that transfers the driving
force to the driving wheels by transferring the power of the engine
to the DCT when the vehicle drives in the third stage. The N-1-th
stage is the second stage, which is the intermediate target stage,
and the N-1-th stage clutch means the even-numbered clutch that
transfers the power when the vehicle drives in the second stage.
The N-2-th stage is the first stage, which is the final target
stage, and the N-2-th stage clutch is the odd-numbered clutch.
[0034] That is, the N-th stage clutch and the N-2-th stage clutch
are the same odd-numbered clutch.
[0035] Furthermore, a clutch speed is hereinafter mentioned. The
clutch speed has the same meaning as a speed of an input shaft to
which the corresponding clutch is connected. That is, for example,
a speed of the N-th stage clutch means a speed of an odd-numbered
input shaft, which is an input shaft implementing the third stage
in the example.
[0036] Referring to FIG. 2 and FIG. 3, a shifting control method of
a vehicle with a dual-clutch transmission (DCT) according to an
exemplary embodiment of the present invention includes a first
preparing step (S10) of, by a controller, controlling a torque of
an N-th stage clutch to a predetermined minimum torque and
increasing a torque of an N-1-th stage clutch to a predetermined
standby torque, when a same-shaft power on down shift is initiated
and an engagement of an N-1-th stage gear is completed; a first
handover step (S20) of, by the controller, releasing the torque of
the N-th stage clutch and increasing the torque of the N-1-th stage
clutch, when the torque of the N-1-th stage clutch reaches the
standby torque and a rotation speed of an engine is equal to or
greater than a speed of the N-1-th stage clutch; a gear changing
step (S30) of, by the controller, releasing an N-th stage gear and
then initiating an engagement of an N-2-th stage gear; a
synchronization maintaining step (S40) of, by the controller,
maintaining a synchronized state by adjusting the torque of the
N-1-th stage clutch when it is determined that the rotation speed
of the engine is synchronized with a speed of the N-2-th stage
clutch; a second preparing step (S50) of, by the controller,
increasing the torque of the N-2-th stage clutch to the standby
torque when the engagement of the N-2-th stage gear is completed;
and a second handover step (S60) of, by the controller, releasing
the torque of the N-1-th clutch and increasing the torque of the
N-2-th stage clutch, when the torque of the N-2-th stage clutch
reaches the standby torque.
[0037] That is, according to an exemplary embodiment of the present
invention, when the same-shaft power on down shift is initiated, a
faster increase in the rotation speed of the engine is achieved by
controlling the torque of the N-th stage clutch to the minimum
torque through the first preparing step (S10). When the rotation
speed of the engine is equal to or greater than the speed the
N-1-th stage clutch, the rotation speed of the engine is controlled
to be smoothly synchronized with the speed of the N-2-th stage
clutch, which is the final target stage, by reducing a slope of the
increase in the rotation speed of the engine with the N-1-th
clutch. As a result, a fast and smooth same-shaft power on down
shift may be performed.
[0038] For reference, when the power on down shift is initiated,
the N-1-th stage gear engagement is basically initiated.
[0039] The controller may be configured to determine whether an
inter-stage ratio between the N-th stage, which is the current
stage, and the N-2-th stage, which is the final target stage, is
equal to or greater than a predetermined reference inter-stage
ratio, before the first preparing step (S10), and perform the first
preparing step (S10) only when the inter-stage ratio is equal to or
greater than the predetermined reference inter-stage ratio.
[0040] A transmission of the vehicle has a tendency that the
inter-stage ratio becomes larger as it goes to a lower stage, and
the inter-stage ratio becomes smaller as it goes to a higher stage.
The large inter-stage ratio means that a speed difference at which
the rotation speed of the engine is to be changed is as great as
during the shifting. When the speed difference at which the
rotation speed of the engine is to be changed is large, the time
required for the shifting becomes longer, so that the inter-stage
ratio between the current stage and the final target stage is large
and the speed difference at which the rotation speed of the engine
is to be changed is large during the shifting. Therefore, a faster
shifting is achieved by performing the present invention from the
first preparing step (S10) only when the time required for shifting
becomes too long, and a conventional same-shaft power on down shift
is performed otherwise.
[0041] Therefore, the predetermined reference inter-stage ratio is
determined to be designed by experiment and analysis according to
the above-mentioned purpose. For example, in a case of forward
8-speed DCT, since the present invention may be applied to the
same-shaft power on down shift between the shifting stages of a
fourth stage or less, the predetermined reference inter-stage ratio
may be determined as a value slightly smaller than an inter-stage
ratio between the fourth stage and a second stage, or an
inter-stage ratio between a third stage and a first stage.
[0042] For reference, the inter-stage ratio is expressed as a ratio
of shifting ratios, and for example, the inter-stage ratio between
the fourth stage and the second stage means a second stage shifting
ratio/fourth stage shifting ratio.
[0043] Meanwhile, as described above, instead of determining a
level of the inter-stage ratio between the N-th stage, which is the
current stage, and the N-2-th stage, which is the final target
stage, it may be replaced with determining whether or not the speed
difference between the speed of the N-th stage clutch and the speed
of the N-2-th stage clutch is equal to or greater than the
predetermined reference speed. This is because the speed difference
between the two input shafts is large as the inter-stage ratio is
large.
[0044] The controller may be configured to determine whether or not
the current shifting is a shifting situation during shifting before
the first preparing step (S10), and perform the first preparing
step (S10) only when the current shifting is not the shifting
situation during shifting.
[0045] The shifting situation during shifting refers to a case in
which the shiftings are overlapped due to separate shifting
requests occurring at different points in time but adjacent to each
other, for example, a case in which the shifting to the second
stage is initiated again while the shifting from the fifth stage to
the third stage proceeds. Since an unstable control situation may
occur in such a shifting situation during shifting, the control
according to an exemplary embodiment of the present invention is
not performed and the conventional same-shaft power one down shift
is performed in such a situation.
[0046] In the first preparing step (S10), the minimum torque which
is the control target of the torque of the N-th stage clutch has a
value which is as small as possible so that the rotation speed of
the engine increases faster than that in the case of the common
same-shaft power on down shift, and is set to a level which may
affect the rotation speed of the engine to prevent the rotation
speed of the engine from rising excessively and causing a problem
such as an impact. Therefore, the minimum torque may be determined
to be designed by a plurality of experiments and analyses to be
determined according to a vehicle speed and a shifting progress
rate.
[0047] For example, as the vehicle speed is lower, the minimum
torque has a smaller value, achieving a faster increased in the
rotation speed of the engine. As the shifting progress rate is
larger, the minimum torque has a larger value, suppressing an
excessive increase in the rotation speed of the engine.
[0048] For example, the shifting progress rate may be determined as
(Speed of Engine-Speed of Releasing Clutch)/(Speed of Coupling
Clutch-Speed of Releasing Clutch).
[0049] Meanwhile, the standby torque is substantially 0 Nm, which
means that the clutch is controlled to be in the vicinity of a
touch point, so that when the torque of the clutch is to be
increased, the torque of the clutch may be immediately
increased.
[0050] That is, in the first preparing step (S10), the increasing
of the torque of the N-1-th stage clutch to the standby torque
means that the clutch actuator is driven in a direction in which
the clutch is engaged from a state in which the N-1-th stage clutch
is completely separated before the touch point and the clutch is
moved to the vicinity of the touch point.
[0051] In the first handover step (S20), the controller increases
the torque of the N-1-th stage clutch at a predetermined first
slope while releasing the torque of the N-th stage clutch during a
predetermined first target time.
[0052] The first target time may be set according to the vehicle
speed and the torque of the engine. For example, as the vehicle
speed is lower, the first target time is set to be shorter, and as
the torque of the engine is larger, the first target time is set to
be shorter. Accordingly, as the vehicle speed is lower and the
torque of the engine is larger, the first handover step (S20) may
be more rapidly completed. The first target time is set to be
designed by a plurality of experiments and analyses.
[0053] The first slope may be set according to the vehicle speed
and the shifting progress rate. For example, as the shifting
progress rate is lower and the vehicle speed is lower, the first
slope is set to be larger, increasing more rapidly the torque of
the N-1-th stage clutch. The first slope is also set to be designed
by a plurality of experiments and analyses.
[0054] In the gear changing step (S30), the controller releases the
N-stage gear and initiates the engagement of the N-2-th gear, after
completely releasing the torque of the N-th stage clutch.
[0055] That is, in performing the gear changing step (S30) after
the first handover step (S20) is completed, after the N-th stage
clutch is completely farther away from the touch point by
completely releasing the torque of the N-th stage clutch, the N-th
stage gear is released and the engagement of the N-2-th gear is
attempted so that a more smooth releasing of the N-th stage gear
and a smooth engagement of the N-2-th stage gear are achieved.
[0056] During the gear changing step (S30), the controller
increases the torque of the N-1-th stage clutch in succession to
the first handover step.
[0057] That is, the increase in the torque of the N-1-th stage
clutch at the first slope in the first handover step (S20) also
continues continuously during the gear changing step.
[0058] In the synchronization maintaining step (S40), the
controller feedback-controls the torque of the N-1-th stage clutch
to maintain the synchronized state.
[0059] If the engagement of the N-2-th stage gear is completed
while the rotation speed of the engine maintains a state
synchronized with the speed of the N-2-th stage clutch, the
controller performs the second preparing step (S50) to increase the
torque of the N-2-th stage clutch to the standby torque.
[0060] If the torque of the N-2-th stage clutch reaches the standby
torque, the controller performs the second handover step (S60). In
the instant case, only when the rotation speed of the engine
maintains the state synchronized with the speed of the N-2-th stage
clutch for a predetermined time, the controller performs the second
handover step (S60) thereby achieving a stable shifting finish.
[0061] That is, when the rotation speed of the engine does not
temporarily maintain the state synchronized with the speed of the
N-2-th stage clutch and a speed difference occurs, even in a state
in which the torque of the N-2-th stage clutch reaches the standby
torque, when the second handover step (S60) is performed, a problem
such as an abnormal increase in the rotation speed of the engine or
the like may occur. Therefore, the synchronized state of the
rotation speed of the engine is further confirmed so that the
shifting may be completed more reliably.
[0062] In the second handover step (S60), the controller increases
the torque of the N-2-th stage clutch at a predetermined second
slope while releasing the torque of the N-1-th stage clutch during
a predetermined second target time.
[0063] The second target time may also be determined by a
functional relationship between the vehicle speed and the torque of
the engine. For example, as the vehicle speed is lower, the second
target time is set to be shorter, and as the torque of the engine
is larger, the second target time is set to be shorter.
Accordingly, as the vehicle speed is lower and the torque of the
engine is larger, the second handover step (S20) may be more
rapidly completed. The second target time is set to be designed by
a plurality of experiments and analyses.
[0064] The second slope may be set according to the torque of the
engine and the vehicle speed. For example, as the torque of the
engine is larger and the vehicle speed is lower, the second slope
is set to be larger, increasing more rapidly the torque of the
N-2-th stage clutch. The second slope is also set to be designed by
a plurality of experiments and analyses.
[0065] As described above, when the second handover step (S60) is
completed, the same-shaft power on down shift according to an
exemplary embodiment of the present invention is completed.
[0066] According to an exemplary embodiment of the present
invention, a commercial value of a vehicle may be ultimately
improved by improving shifting responsiveness to minimize
disadvantages of the DCT with faster same-shaft down shift at the
time of the same-shaft power on down shift by an accelerator pedal
operation of a driver in a DCT-provided vehicle.
[0067] For convenience in explanation and accurate definition in
the appended claims, the terms "upper", "lower", "inner", "outer",
"up", "down", "upwards", "downwards", "front", "rear", "back",
"inside", "outside", "inwardly", "outwardly", "internal",
"external", "inner", "outer", "forwards", and "backwards" are used
to describe features of the exemplary embodiments with reference to
the positions of such features as displayed in the figures. It will
be further understood that the term "connect" or its derivatives
refer both to direct and indirect connection.
[0068] The foregoing descriptions of specific exemplary embodiments
of the present invention have been presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the present invention to the precise forms
disclosed, and obviously many modifications and variations are
possible in light of the above teachings. The exemplary embodiments
were chosen and described to explain certain principles of the
present invention and their practical application, to enable others
skilled in the art to make and utilize various exemplary
embodiments of the present invention, as well as various
alternatives and modifications thereof. It is intended that the
scope of the present invention be defined by the Claims appended
hereto and their equivalents.
* * * * *