U.S. patent application number 14/499243 was filed with the patent office on 2015-04-23 for control apparatus for automatic transmission and control method for automatic transmission.
This patent application is currently assigned to HONDA MOTOR CO., LTD.. The applicant listed for this patent is HONDA MOTOR CO., LTD.. Invention is credited to Takashi SATOYOSHI.
Application Number | 20150112561 14/499243 |
Document ID | / |
Family ID | 52826893 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150112561 |
Kind Code |
A1 |
SATOYOSHI; Takashi |
April 23, 2015 |
CONTROL APPARATUS FOR AUTOMATIC TRANSMISSION AND CONTROL METHOD FOR
AUTOMATIC TRANSMISSION
Abstract
A control apparatus for an automatic transmission that
selectively engages a plurality of frictional engaging elements for
shift control includes a shift instruction device, a temperature
calculator, an engageability determiner, an engagement delay
device, a load calculator, a cumulative load calculator, and a
threshold temperature changer. The engageability determiner is
configured to determine whether at least one of the plurality of
frictional engaging elements is engageable or not based on a
comparison between a temperature of the at least one of the
plurality of frictional engaging elements calculated by the
temperature calculator and a predetermined threshold temperature in
a case where the shift instruction device outputs a shift
instruction. The threshold temperature changer is configured to
change the predetermined threshold temperature in a case where a
cumulative load calculated by the cumulative load calculator
reaches a value greater than or equal to a predetermined value.
Inventors: |
SATOYOSHI; Takashi; (Wako,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HONDA MOTOR CO., LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
HONDA MOTOR CO., LTD.
Tokyo
JP
|
Family ID: |
52826893 |
Appl. No.: |
14/499243 |
Filed: |
September 29, 2014 |
Current U.S.
Class: |
701/65 |
Current CPC
Class: |
F16H 61/68 20130101;
F16H 59/72 20130101; F16H 59/14 20130101; F16H 61/0213
20130101 |
Class at
Publication: |
701/65 |
International
Class: |
F16H 61/02 20060101
F16H061/02; F16H 61/68 20060101 F16H061/68 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2013 |
JP |
2013-220128 |
Claims
1. A control apparatus for an automatic transmission that
selectively engages a plurality of frictional engaging elements for
shift control, the control apparatus comprising: a shift
instruction section that issues a shift instruction; a temperature
calculator that calculates a temperature of at least one of the
frictional engaging elements; an engageability determiner that
determines whether the at least one of the frictional engaging
elements is engageable or not on the basis of a comparison between
the temperature of the at least one of the frictional engaging
elements calculated by the temperature calculator and a
predetermined threshold temperature when the shift instruction
section issues the shift instruction; an engagement delay section
that, if the engageability determiner determines that the one of
the frictional engaging elements is non-engageable, delays
engagement of the at least one of the frictional engaging elements
until the at least one of the frictional engaging elements is
determined to be engageable; a load calculator that calculates a
load input to each of the frictional engaging elements when the
automatic transmission performs shift operation; and a cumulative
load calculator that calculates a cumulative load of accumulated
loads calculated by the load calculator, wherein the engageability
determiner changes a threshold temperature for determining whether
the at least one of the frictional engaging elements is engageable
or not when the cumulative load calculated by the cumulative load
calculator reaches a value greater than or equal to a predetermined
value.
2. The control apparatus of claim 1, wherein the threshold
temperature is set at a lower temperature as the cumulative load
calculated by the cumulative load calculator increases.
3. The control apparatus of claim 1, wherein the threshold
temperature is calculated on the basis of a cumulative load at an
operation limit of the at least one of the frictional engaging
elements, a mileage of a vehicle at the operation limit of the at
least one of frictional engaging elements, and an amount of change
of the cumulative load with respect to an actual mileage of the
vehicle.
4. A control apparatus for an automatic transmission that
selectively engages a plurality of frictional engaging elements for
shift control, the control apparatus comprising: a shift
instruction device configured to output a shift instruction; a
temperature calculator configured to calculate a temperature of at
least one of the plurality of frictional engaging elements; an
engageability determiner configured to determine whether the at
least one of the plurality of frictional engaging elements is
engageable or not based on a comparison between the temperature of
the at least one of the plurality of frictional engaging elements
calculated by the temperature calculator and a predetermined
threshold temperature in a case where the shift instruction device
outputs the shift instruction; an engagement delay device
configured to delay engagement of the at least one of the plurality
of frictional engaging elements until the at least one of the
plurality of frictional engaging elements is determined to be
engageable in a case where the engageability determiner determines
that the at least one of the plurality of frictional engaging
elements is non-engageable; a load calculator configured to
calculate a load input to each of the plurality of frictional
engaging elements in a case where the automatic transmission
performs shift operation; a cumulative load calculator configured
to calculate a cumulative load of the load calculated by the load
calculator; and a threshold temperature changer configured to
change the predetermined threshold temperature in a case where the
cumulative load calculated by the cumulative load calculator
reaches a value greater than or equal to a predetermined value.
5. The control apparatus of claim 4, wherein the threshold
temperature is set at a lower temperature as the cumulative load
calculated by the cumulative load calculator increases.
6. The control apparatus of claim 4, wherein the threshold
temperature is calculated based on a cumulative load at an
operation limit of the at least one of the plurality of frictional
engaging elements, a mileage of a vehicle at the operation limit of
the at least one of the plurality of frictional engaging elements,
and an amount of change of the cumulative load with respect to an
actual mileage of the vehicle.
7. A control apparatus for an automatic transmission that
selectively engages a plurality of frictional engaging elements for
shift control, the control apparatus comprising: shift instruction
means for outputting a shift instruction; temperature calculating
means for calculating a temperature of at least one of the
plurality of frictional engaging elements; engageability
determining means for determining whether the at least one of the
plurality of frictional engaging elements is engageable or not
based on a comparison between the temperature of the at least one
of the plurality of frictional engaging elements calculated by the
temperature calculating means and a predetermined threshold
temperature in a case where the shift instruction means outputs the
shift instruction; engagement delay means for delaying engagement
of the at least one of the plurality of frictional engaging
elements until the at least one of the plurality of frictional
engaging elements is determined to be engageable in a case where
the engageability determining means determines that the at least
one of the plurality of frictional engaging elements is
non-engageable; load calculating means for calculating a load input
to each of the plurality of frictional engaging elements in a case
where the automatic transmission performs shift operation;
cumulative load calculating means for calculating a cumulative load
of the load calculated by the load calculating means; and threshold
temperature changing means for changing the predetermined threshold
temperature in a case where the cumulative load calculated by the
cumulative load calculating means reaches a value greater than or
equal to a predetermined value.
8. A control method for an automatic transmission that selectively
engages a plurality of frictional engaging elements for shift
control, the control method comprising: outputting a shift
instruction; calculating a temperature of at least one of the
plurality of frictional engaging elements; determining whether the
at least one of the plurality of frictional engaging elements is
engageable or not based on a comparison between the temperature of
the at least one of the plurality of frictional engaging elements
calculated by the calculating of the temperature and a
predetermined threshold temperature in a case where the shift
instruction is output; delaying engagement of the at least one of
the plurality of frictional engaging elements until the at least
one of the plurality of frictional engaging elements is determined
to be engageable in a case where the at least one of the plurality
of frictional engaging elements is determined to be non-engageable;
calculating a load input to each of the plurality of frictional
engaging elements in a case where the automatic transmission
performs shift operation; calculating a cumulative load of the load
calculated by the calculating of the load; and changing the
predetermined threshold temperature in a case where the cumulative
load calculated by the calculating of the cumulative load reaches a
value greater than or equal to a predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to Japanese Patent Application No. 2013-220128, filed
Oct. 23, 2013, entitled "Control Apparatus for Automatic
Transmission." The contents of this application are incorporated
herein by reference in their entirety.
BACKGROUND
[0002] 1. Field
[0003] The present disclosure relates to a control apparatus for an
automatic transmission and a control method for an automatic
transmission.
[0004] 2. Description of the Related Art
[0005] Automatic transmissions that automatically perform shifting
by switching power transmission paths each composed of a plurality
of shift gear trains through selective engagement of frictional
engaging elements, such as shift clutches, have been widely
employed for vehicles. In recent automatic transmissions, in order
to increase the power of engines and the shifting performance of
the automatic transmissions, for example, shift operation
(engagement of frictional engaging elements) of the automatic
transmissions tends to be frequently performed. Accordingly, the
automatic transmissions tend to suffer from an increased calorific
value in engaging the frictional engaging elements during shifting.
The increased calorific value of the frictional engaging elements
might cause seizing (burning) of the frictional engaging elements
and other problems. Thus, there is a need for protection control
for protecting the frictional engaging elements against thermal
damage.
[0006] Regarding such protection control, Japanese Patents Nos.
4913535 and 4913848 describe control devices for automatic
transmissions. In the control device described in Japanese Patent
No. 4913535, the temperature of at least one of frictional engaging
elements to be engaged in shifting is computed. In a case where the
computed temperature is higher than a reference temperature, if a
shift operation to a target gear position is an upshift operation
using the frictional engaging element to be engaged, the time of
the upshift operation is delayed by a predetermined time. On the
other hand, if the shift operation to the target gear position is a
downshift operation, the downshift operation is allowed without a
delay.
[0007] In the control device described in Japanese Patent No.
4913848, the temperature of a frictional engaging element is
calculated, and the rotational difference between an input and an
output of the frictional engaging element is calculated. Based on
the calculated temperature and rotational difference of the
frictional engaging element and a pattern of a speed change
instruction, it is determined whether the frictional engagement
element is engageable or non-engageable. If there is a possibility
of burning of the frictional engaging element, the frictional
engagement element is determined to be non-engageable, and
engagement thereof is delayed until the frictional engagement
element is determined to be engageable. In this manner, an
appropriate cooling period is selected, and thus, engagement can be
controlled with protection of the frictional engaging element
against thermal damage.
SUMMARY
[0008] According to one aspect of the present invention, a control
apparatus for an automatic transmission that selectively engages a
plurality of frictional engaging elements for shift control
includes a shift instruction section, a temperature calculator, an
engageability determiner, an engagement delay section, a load
calculator, and a cumulative load calculator. The shift instruction
section issues a shift instruction. The temperature calculator
calculates a temperature of at least one of the frictional engaging
elements. The engageability determiner determines whether the at
least one of the frictional engaging elements is engageable or not
on the basis of a comparison between the temperature of the at
least one of the frictional engaging elements calculated by the
temperature calculator and a predetermined threshold temperature
when the shift instruction section issues the shift instruction.
The engagement delay section, if the engageability determiner
determines that the one of the frictional engaging elements is
non-engageable, delays engagement of the at least one of the
frictional engaging elements until the at least one of the
frictional engaging elements is determined to be engageable. The
load calculator calculates a load input to each of the frictional
engaging elements when the automatic transmission performs shift
operation. The cumulative load calculator calculates a cumulative
load of accumulated loads calculated by the load calculator. The
engageability determiner changes a threshold temperature for
determining whether the at least one of the frictional engaging
elements is engageable or not when the cumulative load calculated
by the cumulative load calculator reaches a value greater than or
equal to a predetermined value.
[0009] According to another aspect of the present invention, a
control apparatus for an automatic transmission that selectively
engages a plurality of frictional engaging elements for shift
control includes a shift instruction device, a temperature
calculator, an engageability determiner, an engagement delay
device, a load calculator, a cumulative load calculator, and a
threshold temperature changer. The shift instruction device is
configured to output a shift instruction. The temperature
calculator is configured to calculate a temperature of at least one
of the plurality of frictional engaging elements. The engageability
determiner is configured to determine whether the at least one of
the plurality of frictional engaging elements is engageable or not
based on a comparison between the temperature of the at least one
of the plurality of frictional engaging elements calculated by the
temperature calculator and a predetermined threshold temperature in
a case where the shift instruction device outputs the shift
instruction. The engagement delay device is configured to delay
engagement of the at least one of the plurality of frictional
engaging elements until the at least one of the plurality of
frictional engaging elements is determined to be engageable in a
case where the engageability determiner determines that the at
least one of the plurality of frictional engaging elements is
non-engageable. The load calculator is configured to calculate a
load input to each of the plurality of frictional engaging elements
in a case where the automatic transmission performs shift
operation. The cumulative load calculator is configured to
calculate a cumulative load of the load calculated by the load
calculator. The threshold temperature changer is configured to
change the predetermined threshold temperature in a case where the
cumulative load calculated by the cumulative load calculator
reaches a value greater than or equal to a predetermined value.
[0010] According to further aspect of the present invention, in a
control method for an automatic transmission that selectively
engages a plurality of frictional engaging elements for shift
control, A shift instruction is output. A temperature of at least
one of the plurality of frictional engaging elements is calculated.
Whether the at least one of the plurality of frictional engaging
elements is engageable or not is determined based on a comparison
between the temperature of the at least one of the plurality of
frictional engaging elements calculated by the calculating of the
temperature and a predetermined threshold temperature in a case
where the shift instruction is output. Engagement of the at least
one of the plurality of frictional engaging elements is delayed
until the at least one of the plurality of frictional engaging
elements is determined to be engageable in a case where the at
least one of the plurality of frictional engaging elements is
determined to be non-engageable. A load input to each of the
plurality of frictional engaging elements is calculated in a case
where the automatic transmission performs shift operation. A
cumulative load of the load calculated by the calculating of the
load is calculated. The predetermined threshold temperature is
changed in a case where the cumulative load calculated by the
calculating of the cumulative load reaches a value greater than or
equal to a predetermined value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings.
[0012] FIG. 1 is a block diagram schematically illustrating a power
transmission system and a control system of a vehicle including a
control device for an automatic transmission according to an
embodiment of the present application.
[0013] FIG. 2 is a block diagram illustrating a functional
configuration of the control device for the automatic transmission
of the embodiment of the present application.
[0014] FIGS. 3A to 3C are flowcharts showing an example in which
the functions of the control device for the automatic transmission
of the embodiment of the present application are obtained by a
computer program.
[0015] FIG. 4 is a table showing a shift restriction rule for
defining a criterion for determining clutch engageability depending
on a combination of a pattern of a shift instruction and a
rotational difference in each temperature range.
[0016] FIGS. 5A and 5B are flowcharts showing processes of
engageability determination and control in accordance with a
specific shift restriction rule.
[0017] FIG. 6 is a flowchart for describing a process of changing a
threshold value of a plate temperature of a clutch for use in shift
restriction.
[0018] FIG. 7 is a flowchart showing a calculation process of a
clutch load.
[0019] FIG. 8 is a graph showing a relationship between a mileage
of a vehicle and a clutch load.
[0020] FIGS. 9A and 9B are graphs showing changes with time of a
plate temperature and a gear position of a clutch in shift
control.
DESCRIPTION OF THE EMBODIMENTS
[0021] The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various
drawings.
[0022] An embodiment of the present application will be described
in detail with reference to the drawings. FIG. 1 is a block diagram
schematically illustrating a power transmission system and a
control system of a vehicle including a control device for an
automatic transmission according to an embodiment of the present
application. The power transmission system of the vehicle includes:
an engine 1 serving as a power source; a torque converter 2 serving
as a fluid coupling for transmitting a rotation output of the
engine 1 to a shift gear mechanism 3; the shift gear mechanism 3
that receives the rotation output from the torque converter 2,
changes the speed of the rotation output with a predetermined speed
ratio, and outputs the resulting rotation output; and a
differential gear mechanism 4 that distributes the output rotation
from the shift gear mechanism 3 to left and right wheels (e.g.,
rear wheels) 5. A hydraulic pressure control device 6 is attached
to the torque converter 2 and the shift gear mechanism 3. The
hydraulic pressure control device 6 locks up the torque converter 2
and sets the input/output speed ratio in the shift gear mechanism 3
at a required gear position by engaging or releasing a
predetermined combination of frictional engaging elements of a
hydraulic pressure control type (e.g., clutches) provided in the
torque converter 2 and the shift gear mechanism 3. The automatic
transmission of the vehicle is composed of the torque converter 2,
the shift gear mechanism 3, and the hydraulic pressure control
device 6, for example.
[0023] A control system for controlling the power transmission
system of the vehicle includes sensors located at various positions
of the vehicle, an electronic control unit (ECU) 10 that receives
outputs from the sensors, and the hydraulic pressure control device
6 controlled by the electronic control unit 10, for example. A
rotation sensor 11 detects the number of revolutions per a unit
time (engine speed) Ne of the input shaft of the torque converter
2. A rotation sensor 12 detects the number of revolutions Ni per a
unit time of the input shaft of the shift gear mechanism 3. A
rotation sensor 13 detects the number of revolutions No of the
output shaft of the shift gear mechanism 3. A vehicle speed sensor
14 detects a vehicle speed Nv. A throttle sensor 15 detects the
opening degree of the throttle of the engine 1 that is determined
depending on the degree of depression of an accelerator pedal. An
ATF temperature sensor 16 detects a temperature (ATF temperature)
of hydraulic fluid in the hydraulic pressure control device 6. A
coolant temperature sensor 17 detects the temperature of an engine
coolant.
[0024] The power transmission system and control system of the
vehicle illustrated in FIG. 1 may employ known configurations. The
control device for the automatic transmission of the present
application is included in the electronic control unit 10, and is
implemented as one of various control functions that can be
performed by the electronic control unit 10. In the following
example, the control device for the automatic transmission of the
present application is operated by a computer program included in
the electronic control unit 10. The control device for the present
application is not operated only by a computer program, and may be,
of course, operated by dedicated electronic circuit hardware.
[0025] FIG. 2 is a block diagram illustrating a functional
configuration of the control device for the automatic transmission
of the present application. The functions illustrated in FIG. 2 are
specifically executed by the electronic control unit 10.
[0026] A shift controller 20 determines an optimum gear position in
accordance with the operating state of the vehicle, and generates a
shift instruction for instructing a gear shift to the determined
gear position. The shift controller 20 may employ any configuration
that is known in the field of automatic shifting control of
vehicles.
[0027] A temperature calculator 21 performs an operation for
calculating the temperature of at least one of frictional engaging
elements (specifically clutch plates) concerning shifting. As a
specific method for calculating the temperature, a known technique
described in Japanese Patent No. 4913535 may be employed, for
example.
[0028] A rotational difference calculator 22 performs an operation
for calculating a rotational difference between the input and
output of at least one of the frictional engaging elements
(clutches) concerning shifting. As a specific method for
calculating the rotational difference, a known technique described
in Japanese Patent No. 4913535 may be employed, for example.
[0029] A determiner 23 determines whether a frictional engaging
element instructed with a shift instruction generated by the shift
controller 20 is engageable or not, on the basis of the calculated
temperature of the frictional engaging element (i.e., the clutch),
the calculated rotational difference, and a pattern of the shift
instruction. The pattern of the shift instruction herein is a
shifting mode to be currently performed, e.g., upshift, downshift,
downshift skipping one or more positions, or sequential downshift
in two or more positions. If the determiner 23 determines that the
frictional engaging element is non-engageable upon generation of
the shift instruction by the shift controller 20, a clutch
engagement control signal for shifting is not issued to the
hydraulic pressure control device 6, and clutch engagement is not
performed (i.e., engagement is suspended). In this manner, it is
possible to prevent seizing of the clutch facing due to heat
generation caused by engagement. When the clutch is cooled with the
suspension of engagement, the temperature calculated by the
temperature calculator 21 in real time or the rotational difference
calculated by the rotational difference calculator 22 in real time
decreases. Thus, the determiner 23 determines that the frictional
engaging element is engageable, and a clutch engagement control
signal for shifting is issued to the hydraulic pressure control
device 6, thereby performing clutch engagement for shifting. In
this manner, engagement operation of the clutch can be
appropriately delayed.
[0030] FIGS. 3A to 3C are flowcharts showing an example in which
the functions of the shift controller, the calculator 21, the
rotational difference calculator 22, and the determiner 23 are
obtained by a computer program included in the electronic control
unit 10. A "clutch calorific value estimation" routine at step S1
and a "clutch plate temperature estimation" routine at step S2 in
FIG. 3A correspond to the function of the temperature calculator
21. The "clutch calorific value estimation" routine at step S1 is
specifically shown in FIG. 3B. The "clutch plate temperature
estimation" routine at step S2 is specifically shown in FIG. 3C. A
"clutch rotational difference computation" at step S12 in FIG. 3B
corresponds to the function of the rotational difference calculator
22. These functions are known functions, and will be briefly
explained in the following description. A "clutch plate,
temperature range determination" routine at step S3 and a "shift
restriction" routine at step S4 in FIG. 3A correspond to the
functions of the determiner 23. The process routines shown in FIGS.
3A to 3C are repeatedly performed by a timer interrupt, and
processing such as temperature calculation, rotational difference
calculation, and determination is performed in real time.
[0031] In FIG. 3A, in the "clutch calorific value estimation"
routine at step S1, an operation of estimating the calorific value
generated by each clutch concerning shifting, i.e., a clutch (an ON
clutch) to be newly engaged and a clutch (an OFF clutch) to be
disengaged, is performed in real time.
[0032] Specifically, as shown in FIG. 3B, in the "clutch calorific
value estimation" routine, first, an operation of estimating a
clutch torque TCL of a target clutch is performed at "clutch torque
estimation" step S11. For example, on the basis of a clutch
engagement instruction gauge pressure and other necessary
parameters, an oil filler factor of the clutch is computed. On the
basis of the obtained oil filler factor, a clutch torque TCL is
calculated.
[0033] Next, in "clutch rotational difference computation" step
S12, an input/output rotational difference .DELTA..omega. of the
clutch is calculated. This input/output rotational difference
.DELTA..omega. is calculated on the basis of the number of input
revolutions Ni, the number of output revolutions No, and the gear
ratio of the transmission.
[0034] Then, in "clutch calorific value computation" step S13, a
clutch calorific value .DELTA.Q of the clutch in a unit time is
calculated as a product of the clutch torque TCL and the rotational
difference .DELTA..omega. (i.e., .DELTA.Q=TCL.DELTA..omega.), for
example. The unit time herein corresponds to an interrupt cycle of
repetitive processing routines shown in FIGS. 3A to 3C by a timer
interrupt.
[0035] In FIG. 3A, in the "clutch plate temperature estimation"
routine at step S2, an operation of estimating the clutch plate
temperature of each clutch is performed. In this step, the current
clutch plate temperatures of all the clutches are estimated, and
managed. Specifically, in a case where a temperature rise due to
heat generation occurs in an engaged clutch but a temperature
decrease due to cooling after disengagement proceeds in every
clutch in real time so that the disengaged clutch is the next
target for engagement by shifting, the current clutch plate
temperatures of all the clutches need to be estimated and managed
in order to calculate the current clutch plate temperatures of all
the clutches promptly.
[0036] As shown in FIG. 3C, in the "clutch plate temperature
estimation" routine, first, at "temperature rise computation" step
S21, the temperature rise Hp of a target clutch is calculated on
the basis of the clutch calorific value .DELTA.Q. The temperature
rise Hp refers to the degree of a temperature rise that is
estimated as a temperature rise in one timer interrupt cycle in the
processing routine that is repeatedly performed in FIGS. 3A to 3C.
The temperature rises Hp of clutches not concerning the current
shifting may be assumed to be substantially zero.
[0037] In "cooling temperature computation" step S22, the cooling
temperature Cp of each clutch is calculated. The cooling
temperature Cp herein refers to the degree of a temperature
decrease that is estimated as a temperature decrease in one timer
interrupt cycle. For example, the cooling temperature Cp is
calculated by using, as parameters, the amount and temperature of
lubricating oil of the clutch, which cause the temperature
decrease.
[0038] In "plate temperature computation" step S23, a current
clutch plate temperature Tp of each clutch is calculated. The
current clutch plate temperature Tp is obtained by adding or
reducing the temperature rise Hp and the cooling temperature Cp to
or from a clutch plate temperature Tp_prev that was obtained in the
previous operation for the clutch. That is, the current clutch
plate temperature Tp is obtained by:
Tp=Tp_prev+Tp+Cp
where the sign of Cp is negative.
[0039] In FIG. 3A, in the "clutch plate temperature range
determination" routine at step S3, it is determined which one of
temperature ranges the current clutch plate temperature Tp of each
clutch belongs to. For example, as shown in FIG. 4, which will be
described later, two temperature ranges are used as clutch plate
temperature ranges. Specifically, a first temperature range (an
allowed range) is a range where the plate temperature Tp is less
than a threshold temperature Tth, and a second temperature range
(an inhibited range) is a range where the plate temperature Tp is
greater than or equal to the threshold temperature Tth.
[0040] In the "shift restriction" routine at step S4, referring to
a predetermined shift restriction rule (table) for defining the
engageablility of a clutch, it is determined whether engagement is
allowed or not in a temperature range to which the current clutch
plate temperature Tp of the clutch belongs.
[0041] The shift restriction rule (table) is used for defining the
criterion for determining whether clutch engagement is allowed or
not depending on a combination of a pattern of a shift instruction
and a rotational difference in each of the temperature ranges
determined as described above, as shown in FIG. 4. In FIG. 4,
.largecircle. (circle) indicates engageable, x (cross) indicates
non-engageable, and .DELTA. (triangle) indicates non-engageable if
the rotational difference is larger than a predetermined threshold
value or partially engageable under specific conditions. The symbol
(#1) added to .DELTA. (triangle) indicates that the mode of
engagement control when the rotational difference is larger than
the predetermined threshold value varies depending on the pattern
of the shift instruction.
[0042] For example, in a case where the pattern of the shift
instruction is "upshift," it is determined which temperature range
the current clutch plate temperature Tp of a clutch for obtaining a
gear position (a target position) after shifting belongs to. This
is because the clutch (i.e., the clutch to be engaged) after
shifting (to the target position) generates a larger amount of heat
in the case of upshift. As shown in the column of "upshift" in FIG.
4, if the current clutch plate temperature Tp of the clutch belongs
to the first temperature range (the allowed range), engagement of
the clutch is allowed. On the other hand, if the current clutch
plate temperature Tp belongs to the second temperature range (the
inhibited range), engagement of the clutch is not allowed.
[0043] A case where the pattern of the shift instruction is
"downshift" will be now described. In the case of "downshift," it
is determined which temperature range the current clutch plate
temperature Tp of a clutch (a clutch to be disengaged) that has
attained a gear position before shifting belongs to. This is
because the clutch (i.e., the clutch to be disengaged) before
shifting (at the current gear position) generates a larger amount
of heat in the case of downshift.
[0044] As shown in the column of "one-stage downshift" in FIG. 4,
in a case where the pattern of the shift instruction is "one-stage
downshift," if the current clutch plate temperature Tp of a clutch
belongs to the first temperature range (the allowed range), it is
determined that the clutch is engageable (indicated as
.largecircle.), and disengagement of the clutch and engagement of
the clutch after shifting (to a target gear position) are allowed.
On the other hand, if the current clutch plate temperature Tp
belongs to the second temperature range (the inhibited range),
engageability is determined in consideration of the rotational
difference .DELTA..omega. of the clutch (indicated as .DELTA.).
FIG. 5A schematically shows a flowchart for determining
engageability concerning ".DELTA.." Specifically, if the current
clutch plate temperature Tp belongs to the second temperature range
(the inhibited range) and the rotational difference .DELTA..omega.
of the clutch is greater than or equal to a predetermined threshold
value .omega.1, it is determined that the gear position is
non-shiftable (YES in step S31). On the other hand, if the
rotational difference .DELTA..omega. of the clutch is less than the
predetermined threshold value .omega.1 although the current clutch
plate temperature Tp belongs to the second temperature range (the
inhibited range), it is determined that the gear position is
shiftable (NO in step S31). In this case, if it is determined that
the gear position is non-shiftable, engagement of a clutch (at the
current gear position) before shifting (i.e., a clutch to be
disengaged) is maintained. Then, when the rotational difference
.DELTA..omega. of the clutch decreases below the predetermined
threshold value .DELTA..omega. or below the first temperature range
(the allowed range), it is determined that the gear position is
shiftable, and downshift in accordance with the shift instruction
is executed. In this manner, in a range in which the shift
restriction is received, shifting (engagement of the clutch) is
delayed until it is determined that the gear position is
shiftable.
[0045] As shown in the column of "downshift" and "multi-stage
direct shift" in FIG. 4, in a case where the pattern of the shift
instruction is "multi-stage direct shift (i.e., so-called skip
downshift)," if the current clutch plate temperature Tp of the
clutch (at the current gear position) before shifting (i.e., the
clutch to be disengaged) belongs to the second temperature range
(the inhibited range), it is determined that the clutch is
non-engageable (indicated as x). On the other hand, if the current
clutch plate temperature Tp belongs to the first temperature range
(the allowed range), engageability determination and control are
performed in consideration of the rotational difference
.DELTA..omega. of the clutch (indicated as .DELTA.#1).
[0046] In this conditional shift restriction (.DELTA.#1),
non-engageability is not simply determined if the rotational
difference .DELTA..omega. of the clutch is greater than or equal to
the predetermined threshold value in the first temperature range
(the allowed range). Instead, direct shift from the previous stage
(e.g., the sixth gear position) to a subsequent stage (e.g., the
fourth gear position) with a step of one or more stages is not
allowed, the shift instruction is changed to step-by-step
sequential downshift by way of the intermediate gear position
(e.g., the fifth gear position), then engagement is allowed, and
engagement is performed. FIG. 5B is a schematic flowchart for
engageability determination and control in the case of
".DELTA.(#1)." Specifically, if the rotational difference
.DELTA..omega. of the clutch is greater than or equal to the
predetermined threshold value .omega.2, the shift instruction is
changed to step-by-step sequential downshift by way of the
intermediate gear position, and then it is determined that the gear
position is shiftable (processing from YES at step S32 to step
S33). Thereafter, disengagement of the clutch at the intermediate
gear position (e.g., the fifth gear position) is instructed, the
subsequent stage (e.g., the fourth gear position) is indicated as a
target position of downshift, and a clutch at the subsequent stage
(e.g., the fourth gear position) is engaged. In this manner, the
instruction is switched to step-by-step sequential downshift, and
downshift is performed. This change not to the direct shift with a
step of one more stages but to the step-by-step sequential
downshift places a workload of the clutch at the previous gear
position on the clutch at the intermediate gear position. Thus, the
workload of the clutch at the previous gear position can be
reduced, and the calorific value decreases accordingly. In this
manner the clutch at the previous gear position is protected
against burning. In the conditional shift restriction (.DELTA.#1),
even if the temperature of the clutch belongs to the first
temperature range (the allowed range), it is determined that the
gear position is shiftable (NO at step S32) as long as the
rotational difference .DELTA..omega. of the clutch is less than the
predetermined threshold value.
[0047] As described above, in the control of this embodiment, in
order to prevent thermal damage such as seizing of a clutch,
protection control that inhibits engagement of the clutch in
principle is performed when the temperature (the plate temperature)
Tp of the clutch becomes greater than or equal to the threshold
temperature Tth.
[0048] In the control of this embodiment, a cumulative load (i.e.,
a clutch load K, which will be described later) input to the clutch
is calculated, and depending on the accumulated load, the threshold
temperature Tth of the plate temperature Tp for performing
(starting) protection control of the clutch is changed. That is,
the threshold temperature Tth, which is a fixed value in a typical
control device, is a variable value depending on the status of use
of the clutch. Specifically, as shown in FIG. 2, the control device
for the automatic transmission of the present application includes,
as its functional configuration, a load calculator 24 that
calculates a load input to a clutch in each shift operation and a
cumulative load calculator 25 that calculates a cumulative load
that is accumulated values calculated by the load calculator. On
the basis of the cumulative load calculated by the cumulative load
calculator 25, the determiner 23 changes the temperature threshold
value Tth for determining whether the clutch is engageable or not.
A process of changing the threshold temperature Tth will now be
specifically described.
[0049] FIG. 6 is a flowchart for describing the process of changing
the threshold temperature Tth of the plate temperature Tp of a
clutch in the above-described shift restriction. First, accumulated
loads (hereinafter referred to as a "clutch load K") input to the
clutch by engagement of the clutch in shift operation is calculated
(step S51). The clutch load K is calculated in accordance with a
flowchart (subroutine shown in FIG. 7). Specifically, first, it is
determined whether shift operation is being performed by the
automatic transmission or not (step S511). If the shift operation
is not being performed (NO), the process is finished without any
additional process. On the other hand, if the shift operation is
being performed (YES), the clutch load K is calculated (step
S512).
[0050] The clutch load K is expressed in the following Equation
1:
K=.SIGMA.F(T,P,Q,N)/F(T0,P0,Q0,N0) (Equation 1)
[0051] where (T, T0) is a plate temperature (Tp) of a clutch, (P,
P0) is a clutch pressure, (Q, Q0) is a calorific value of the
clutch in the shift operation, and (N, N0) is the number of
operations (i.e., the number of engagements) of the clutch. In
addition, each of T0, P0, and Q0 is an initial value in a situation
where the clutch does not deteriorate. That is, the cumulative load
(the degree of damage) input to the clutch is calculated on the
basis of the temperature, the number of shift operations, and the
calorific value of the clutch. As the clutch load K, accumulated
loads input to each of clutches are individually calculated. In
Equation 1, F(T, P, Q, N) are functions of T, P, Q, and N.
[0052] In this example, a stage (0<K.ltoreq.K1) before the
calculated clutch load K reaches a predetermined first value K1 is
an initial stage for protection control of the clutch, a stage
(K1<K.ltoreq.K2) from when the calculated clutch load K exceeds
the first value K1 to when the calculated clutch load K reaches a
predetermined second value K2 (K1<K2) is a first stage for the
protection control of the clutch, and a stage (K2<K.ltoreq.K3)
from when the calculated clutch load K exceeds the second value K2
to when the calculated clutch load K reaches a predetermined third
value K3 (K2<K3) is a second stage for the protection control of
the clutch.
[0053] In the initial stage (0<K.ltoreq.K1) for the clutch
protection control, the threshold temperature Tth for determining
shiftability (engageability of the clutch) is T1. In the first
stage (K1<K.ltoreq.K2), the threshold temperature Tth for
determining shiftability is T2. In the second stage
(K2<K.ltoreq.K3), the threshold temperature Tth for determining
shiftability is T3. In this example, T1 and T2 are predetermined
temperatures (constant values), and T3 is a temperature calculated
depending on situations of the first stage and the second stage. A
calculation method of T3 will be described later. The threshold
temperature T1 may be set at 290.degree. C., and the threshold
temperature T2 may be set at 275.degree. C., for example.
[0054] Specifically, as shown in the flowchart of FIG. 6, the
clutch load K is calculated at step ST51, and then, it is
determined whether the calculated clutch load K is larger than K1
or not. If the clutch load K is less than or equal to K1 (NO), the
threshold temperature Tth is kept at T1, and the process is
finished. On the other hand, if the clutch load K is larger than K1
(K>K1) (YES), the threshold temperature Tth for the protection
control of the clutch is changed from T1 to T2 (switching).
Subsequently, it is determined whether the clutch load K is larger
than K2 or not (step S54). Then, if the clutch load K is less than
or equal to K2 (NO), the threshold temperature Tth is kept at T2,
and the process is finished. On the other hand, if the clutch load
K is larger than K2 (K>K2) (YES), the threshold temperature T3
for the clutch protection control to be used in the second stage is
calculated (step S55).
[0055] A process of calculating the threshold temperature T3 will
now be described. FIG. 8 is a graph showing a relationship between
a mileage (a cumulative mileage) L of a vehicle and a clutch load
K. As shown in the graph, a mileage L of the vehicle is L1 when the
clutch load K is K1, and the mileage L of the vehicle is L2 when
the clutch load K is K2. A guaranteed distance (a mileage at which
the clutch reaches the working limit) L of the clutch is L3, and
the clutch load K corresponding to the guaranteed distance L3 is
K3. In the initial stage (0<K.ltoreq.K1) of the clutch
protection control, an amount of change .alpha.1 of clutch load
K=K1 with respect to the mileage L=L1 of the vehicle is expressed
by the following Equation 2:
.alpha.1=K1/L1 (Equation 2)
[0056] In the first stage (K1<K.ltoreq.K2) of the clutch
protection control, an amount of change .alpha.2 of a clutch load
K=K2-K1 with respect to a mileage L=L2-L1 of the vehicle is
expressed by the following Equation 3:
.alpha.2=(K2-K1)/(L2-L1) (Equation 3)
[0057] In the second stage (K2<K.ltoreq.K3) of the clutch
protection control, an amount of change .alpha.3 of a clutch load
K=K3-K2 with respect to a mileage L=L3-L2 of the vehicle is
expressed by the following Equation 4:
.alpha.3=(K3-K2)/(L3-L2) (Equation 4)
[0058] Thus, the threshold temperature T3 to be used in the second
stage of the clutch protection control is calculated from the
following Equation 5:
T3=T2-{.alpha.3/(.alpha.1-.alpha.2)}(T1-T2) (Equation 5)
[0059] In this manner, the threshold temperature T3 can be
calculated on the basis of the clutch load K3 at the operation
limit of the clutch, the mileage (the cumulative mileage) L3 of the
vehicle at the operation limit of the clutch, and the amounts of
change .alpha.1 to .alpha.3 of the clutch load K with respect to an
actual mileage L of the vehicle. In a case where T1=290.degree. C.
and T2=275.degree. C., the calculated threshold temperature T3 is a
temperature T3 of about 250.degree. C., for example.
[0060] Referring back to the flowchart of FIG. 6, after the
threshold temperature T3 has been calculated at step ST55, the
threshold temperature Tth for protection control of the clutch is
switched from T2 to T3.
[0061] A shift control performed on the basis of the switched
threshold temperature Tth will now be described. FIGS. 9A and 9B
are graphs showing changes with time in plate temperature Tp and
gear position n of the clutch in shift control. FIG. 9A shows a
case where the threshold temperature Tth for shift restriction is
changed from a temperature T1 to a temperature T2. FIG. 9B shows a
case where the threshold temperature Tth for shift restriction is
changed from the temperature T2 to a temperature T3. In the graph
of FIG. 9A, the chain lines indicate the threshold temperature T1
and a change in plate temperature Tp corresponding to the threshold
temperature T1, and dotted lines indicate the threshold temperature
T2 and a change in plate temperature Tp corresponding to the
threshold temperature T2. The gear positions indicated by the
dotted lines show switching of gear positions corresponding to the
threshold temperature T1, and changes in gear position indicated by
the continuous lines show switching of gear positions corresponding
to the threshold temperature T2. Similarly, in the graph of FIG.
9B, the dotted lines show the threshold temperature T2 and a change
in plate temperature Tp corresponding to the threshold temperature
T2, and the long dashed double-short dashed lines show the
threshold temperature T3 and a change in plate temperature Tp
corresponding to the threshold temperature T3. The gear positions
indicated by the dotted lines show switching of gear positions
corresponding to the threshold temperature T2, and a change in gear
position indicated by the continuous lines shows switching of gear
positions corresponding to the threshold temperature T3.
[0062] In the example of FIG. 9A, in the case of changing the
threshold temperature Tth for the shift control from T1 to T2, in a
normal shift control (switching of gear position indicated by
dotted lines), switching (upshift) of the gear position from the
third gear position to the fourth gear position stage indicated by
A in FIG. 9A might cause the plate temperature Tp to exceed the
threshold temperature T2 temporarily (indicated by B). In a case
where the threshold temperature T is expected to exceed T2 as
described above, switching of the gear position at this timing is
not allowed (indicated by C), and switching of the gear position is
delayed until it is determined that the threshold temperature does
not exceed T2 (shift hold control). In this manner, the plate
temperature Tp is controlled within a range in which the plate
temperature Tp does not exceed the threshold temperature T2
(indicated by D).
[0063] Similarly, in the example of FIG. 9B, in the case of
changing the threshold temperature Tth for the shift control from
T2 to T3, in a normal shift control (switching of the gear position
indicated by dotted lines), skip shifting (skip downshift) from the
sixth gear position to the third gear position indicated b E in
FIG. 9B might cause the plate temperature Tp to exceed the
threshold temperature T3 temporarily (indicated by F). In this
manner, in a case where the plate temperature Tp is expected to
exceed the threshold temperature T3, skip shifting at this time is
not allowed (indicated by G), and sequential switching of the gear
position is performed. In this manner, the plate temperature Tp is
controlled within a range in which the plate temperature Tp does
not exceed the threshold temperature T3 (indicated by H).
[0064] As described above, in protection control of a clutch by the
control device of this embodiment, when a shift instruction of the
automatic transmission is issued, a calculated plate temperature Tp
of the clutch and the threshold temperature Tth previously
determined on the basis of a rotational difference of the clutch
and a pattern of the shift instruction are compared with each
other, thereby determining engageability of the clutch. If the
clutch is determined to be non-engageable, engagement of the clutch
(shift operation) is delayed until the clutch is determined to be
engageable. In such a control, a cumulative load (a clutch load K)
input to each clutch when shift operation by the automatic
transmission is performed is calculated. When the calculated clutch
load K becomes greater than or equal to a predetermined value, the
threshold temperature Tth for determining engageability of the
clutches changed.
[0065] In this manner, the temperature range for protection control
of the clutch can be changed step by step depending on the
cumulative load. Thus, protection control can be appropriately
performed depending on actual application of clutches. As a result,
performance of the clutches can be maintained in a guarantee period
of the automatic transmission.
[0066] Specifically, in typical protection control of clutches, a
threshold temperature for determining engageability of the clutch
is determined only in order to prevent damage by, for example,
seizing on the clutches. In this typical control, the threshold
temperature is constant (at a fixed value) during the entire
service period of the clutch. On the other hand, in clutch
protection control of this embodiment, the threshold temperature,
which is constant in typical control, is variable depending on a
value (i.e., a clutch load K) calculated depending on actual
application of a clutch.
[0067] Specifically, if the threshold temperature Tth in clutch
protection control is set at a lower temperature, a smaller load is
applied to the clutch. However, shift restriction in shift control
increases, and this increase might adversely affect running
performance of a vehicle. Thus, setting the threshold temperature
Tth at a low temperature during the entire service period of the
clutch is not advantageous in view of obtaining excellent running
performance of the vehicle. On the other hand, the threshold
temperature Tth needs to be set at a lower temperature after
long-term use of clutches in order to obtain durability of the
clutches. In view of this, in the control of this embodiment, the
threshold temperature Tth for protection control is varied
depending on the period of use and the cumulative load of clutches.
In this manner, both excellent running performance of the vehicle
in an initial stage of use of the clutches and durability after
long-term use of the clutches can be achieved.
[0068] In addition, in the protection control of this embodiment,
the threshold temperature Tth is set at a lower temperature as the
cumulative load K increases. That is, it is determined that a
clutch deteriorates as the cumulative load K of the clutch
increases. Thus, in such a case, the threshold temperature Tth for
protection control of the clutch is set at a lower temperature. In
this manner, the threshold temperature is optimized in
consideration of durability of the vehicle in long-term use of the
clutches. This ensures protection of the clutches, thereby
maintaining performance of the clutches in a guarantee period of
the automatic transmission.
[0069] Further, in the control device of this embodiment, in
calculating the threshold temperature T3 to be used in the second
stage of clutch protection control, the threshold temperature T3 is
calculated (determined) on the basis of the total load (cumulative
load) (K3), which is an operation limit of a clutch, the mileage
(L3) of the vehicle with which performance of the clutches is
guaranteed, and the amount of change in cumulative load calculated
on the basis of the clutch cumulative load (K) of the clutches and
the mileage (L) of the vehicle.
[0070] With this configuration, the threshold temperature can be
set at an appropriate value depending on actual application of the
clutches. Thus, performance of the clutches in the guarantee period
of the automatic transmission can be maintained.
[0071] The foregoing description has been made on an embodiment of
the present application. However, the present application is not
limited to the foregoing embodiment, and various changes or
modifications may be made within the scope of the appended claims,
description, and drawings.
[0072] In an aspect of the present application, a control device
for an automatic transmission selectively engages a plurality of
frictional engaging elements for shift control, and includes: a
shift instruction section that issues a shift instruction; a
temperature calculator that calculates a temperature of at least
one of the frictional engaging elements; an engageability
determiner that determines whether the at least one of the
frictional engaging elements is engageable or not on the basis of a
comparison between the temperature (Tp) of the at least one of the
frictional engaging elements calculated by the temperature
calculator and a predetermined threshold temperature (Tth) when the
shift instruction section issues the shift instruction; an
engagement delay section that delays, if the engageability
determiner determines that the one of the frictional engaging
elements is non-engageable, engagement of the at least one of the
frictional engaging elements until the at least one of the
frictional engaging elements is determined to be engageable; and a
cumulative load calculator that calculates a cumulative load (K) of
accumulated loads input to each of the frictional engaging elements
when the automatic transmission performs shift operation, and the
engageability determiner changes a threshold temperature (Tth) for
determining whether the at least one of the frictional engaging
elements is engageable or not when the cumulative load (K)
calculated by the cumulative load calculator reaches a value
greater than or equal to a predetermined value (K1, K2, K3).
[0073] In the control device for the automatic transmission that
performs protection control of inhibiting engagement of at least
one of the frictional engaging elements when the at least one of
the frictional engaging elements reaches a temperature greater than
or equal to the threshold temperature, the cumulative load input to
the frictional engaging element is calculated, and depending on the
cumulative load, the threshold temperature for performing
(starting) protection control of the frictional engaging element is
changed. That is, the range of protection control for the
frictional engaging element can be changed step by step in
accordance with the cumulative load. In this manner, protection
control appropriate for application of the frictional engaging
elements can be performed, and thus performance of the frictional
engaging elements can be maintained in a guarantee period of the
automatic transmission.
[0074] In the control device, the threshold temperature (Tth) is
preferably set at a lower temperature as the cumulative load (K)
calculated by the cumulative load calculator increases. That is, it
is determined that the frictional engaging elements deteriorate as
the cumulative loads of the frictional engaging elements increase.
Thus, in this case, the threshold temperature for protection
control of the frictional engaging elements is set at a lower
temperature. In this manner, the threshold temperature is optimized
in consideration of durability of the frictional engaging elements
and the vehicle in long-term use. This ensures protection of the
frictional engaging elements and maintains performance of the
frictional engaging elements in a guarantee period of the automatic
transmission.
[0075] In the control device, the threshold temperature (Tth) may
be calculated on the basis of a cumulative load (K3) at an
operation limit of the at least one of the frictional engaging
elements, a mileage (L3) of a vehicle at the operation limit of the
at least one of the frictional engaging elements, and an amount of
change (.alpha.1 to .alpha.3) in the cumulative load (K) with
respect to an actual mileage (L) of the vehicle.
[0076] With this configuration, the threshold temperature
appropriate for the operation limit and actual application of the
frictional engaging elements can be selected. This configuration
further ensures maintenance of performance of the frictional
engaging elements in the guarantee period of the automatic
transmission. The characters in the brackets described above are an
example of components of an embodiment that will be described above
as an example of the present application.
[0077] In the control device for the automatic transmission of the
present application, the threshold temperature for protection
control of frictional engaging elements is optimized in view of
durability. Thus, the frictional engaging elements can be protected
against thermal damage upon a temporary increase in temperature of
the frictional engaging elements. In addition, performance of the
frictional engaging elements in the guarantee period of the
automatic transmission can be maintained.
[0078] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *