U.S. patent application number 14/512499 was filed with the patent office on 2016-04-14 for method for detecting a nonoperational shift element in an automatic transmission.
The applicant listed for this patent is ZF Friedrichshafen AG. Invention is credited to Jorg Arnold, Georg Mihatsch, Klaus Steinhauser, Jens Weller.
Application Number | 20160102758 14/512499 |
Document ID | / |
Family ID | 55655152 |
Filed Date | 2016-04-14 |
United States Patent
Application |
20160102758 |
Kind Code |
A1 |
Steinhauser; Klaus ; et
al. |
April 14, 2016 |
Method for Detecting a Nonoperational Shift Element in an Automatic
Transmission
Abstract
A method for detecting a malfunctioning shift element in an
automatic transmission is provided. The method includes operating
the automatic transmission in an intermediate gear. A selected
shift element of the automatic transmission is commanded to a
disengaged configuration in the intermediate gear. The method also
includes measuring a gear ratio of the automatic transmission while
the automatic transmission is operating in the intermediate gear,
and determining whether the selected shift element of the automatic
transmission is malfunctioning based at least in part on the gear
ratio of the automatic transmission in the intermediate gear.
Inventors: |
Steinhauser; Klaus;
(Kressbron, DE) ; Weller; Jens; (Konstanz, DE)
; Mihatsch; Georg; (Lindau, DE) ; Arnold;
Jorg; (Immenstaad, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ZF Friedrichshafen AG |
Friedrichshafen |
|
DE |
|
|
Family ID: |
55655152 |
Appl. No.: |
14/512499 |
Filed: |
October 13, 2014 |
Current U.S.
Class: |
701/62 |
Current CPC
Class: |
F16H 2061/168 20130101;
F16H 2059/706 20130101; F16H 2061/1276 20130101; F16H 61/12
20130101; F16H 2061/1208 20130101 |
International
Class: |
F16H 61/12 20060101
F16H061/12 |
Claims
1. A method for detecting a malfunctioning shift element in an
automatic transmission, comprising: terminating a power flow from
the automatic transmission; operating the automatic transmission in
an intermediate gear after said step of terminating, a selected
shift element of the automatic transmission being commanded to a
disengaged configuration when the automatic transmission is in the
intermediate gear; measuring a gear ratio of the automatic
transmission in the intermediate gear; determining whether the
selected shift element of the automatic transmission is
malfunctioning based at least in part on the gear ratio of the
automatic transmission in the intermediate gear; and shifting the
automatic transmission to a subsequent gear if the selected shift
element of the automatic transmission is not malfunctioning at said
step of determining or continuing to operate the automatic
transmission in the intermediate gear if the selected shift element
of the automatic transmission is malfunctioning at said step of
determining.
2. The method of claim 1, further comprising operating the
automatic transmission in an initial gear prior to said step of
terminating, the selected shift element of the automatic
transmission being in an engaged configuration when the automatic
transmission is in the initial gear.
3. The method of claim 2, wherein said step of terminating
comprises shifting the automatic transmission from the initial gear
to a neutral gear or an extended-neutral gear.
4. (canceled)
5. The method of claim 1, wherein at least one non-positive
shifting element of the automatic transmission is commanded to an
engaged configuration in the intermediate gear.
6. The method of claim 5, wherein at least one positive shifting
element of the automatic transmission is commanded to the engaged
configuration in the intermediate gear.
7. The method of claim 1, wherein said step of determining
comprises: comparing the gear ratio of the automatic transmission
in the intermediate gear to a predetermined gear ratio; and
establishing that the selected shift element of the automatic
transmission is malfunctioning if the gear ratio of the automatic
transmission in the intermediate gear is about equal to the
predetermined gear ratio or establishing that the selected shift
element of the automatic transmission is not malfunctioning if the
gear ratio of the automatic transmission in the intermediate gear
is not about equal to the predetermined gear ratio.
8. The method of claim 7, wherein said step of operating the
automatic transmission in the intermediate gear comprises
commanding all shifting elements of automatic transmission that are
necessary for the intermediate gear to an engaged configuration
except for the selected shift element of the automatic
transmission.
9. The method of claim 8, wherein the predetermined gear ratio is
an expected gear ratio for the intermediate gear with the selected
shift element in the engaged configuration.
10. A method for detecting a malfunctioning shift element in an
automatic transmission, comprising: operating the automatic
transmission in an initial gear, a selected shift element of the
automatic transmission being in an engaged configuration when the
automatic transmission is in the initial gear; terminating a power
flow from the automatic transmission after said step of operating
the automatic transmission in the initial gear; shifting the
automatic transmission to an intermediate gear after said step of
terminating, the selected shift element of the automatic
transmission being commanded to a disengaged configuration when the
automatic transmission is in the intermediate gear; measuring a
gear ratio of the automatic transmission while the automatic
transmission is operating in the intermediate gear; determining
whether the selected shift element of the automatic transmission is
malfunctioning based at least in part on a difference between the
gear ratio of the automatic transmission in the intermediate gear
from said step of measuring and a predetermined gear ratio; and
shifting the automatic transmission to a subsequent gear if the
selected shift element of the automatic transmission is not
malfunctioning at said step of determining or continuing to operate
the automatic transmission in the intermediate gear if the selected
shift element of the automatic transmission is malfunctioning at
said step of determining.
11. The method of claim 10, wherein said step of terminating
comprises shifting the automatic transmission from the initial gear
to a neutral gear or an extended-neutral gear.
12. The method of claim 10, wherein the selected shift element of
the automatic transmission is a dog clutch of the automatic
transmission.
13. The method of claim 10, wherein at least one non-postive
shifting element of the automatic transmission is commanded to the
engaged configuration in the intermediate gear.
14. The method of claim 13, wherein at least one positive shifting
element of the automatic transmission is commanded to the engaged
configuration in the intermediate gear.
15. The method of claim 10, wherein said step of determining
comprises: comparing the gear ratio of the automatic transmission
in the intermediate gear from said step of measuring to the
predetermined gear ratio; and establishing that the selected shift
element of the automatic transmission is malfunctioning if the gear
ratio of the automatic transmission in the intermediate gear from
said step of measuring is about equal to the predetermined gear
ratio or establishing that the selected shift element of the
automatic transmission is not malfunctioning if the gear ratio of
the automatic transmission in the intermediate gear from said step
of measuring is substantially greater or less than the
predetermined gear ratio.
16. The method of claim 15, wherein said step of operating the
automatic transmission in the intermediate gear comprises
commanding all shifting elements of automatic transmission that are
necessary for the intermediate gear to the engaged configuration
except for the selected shift element of the automatic
transmission.
17. The method of claim 16, wherein the predetermined gear ratio is
an expected gear ratio for the intermediate gear with the selected
shift element in the engaged configuration.
18. A method for detecting a malfunctioning shift element in an
automatic transmission, comprising: terminating a power flow from
the automatic transmission; operating the automatic transmission in
an intermediate gear after said step of terminating; measuring a
gear ratio of the automatic transmission in the intermediate gear;
step for determining whether the selected shift element of the
automatic transmission is malfunctioning; and shifting the
automatic transmission to a subsequent gear if the selected shift
element of the automatic transmission is not malfunctioning or
continuing to operate the automatic transmission in the
intermediate gear if the selected shift element of the automatic
transmission is malfunctioning.
Description
FIELD OF THE INVENTION
[0001] The present subject matter relates generally to automatic
transmissions, such as nine-speed automatic transmissions.
BACKGROUND OF THE INVENTION
[0002] Automatic transmissions generally include at least one
planetary gear set and a plurality of shift elements. The shift
elements selectively engage components of the planetary gear sets
in order to hinder or prevent rotation of the components. Selective
actuation of the shift elements adjusts the gear ratio of the
automatic transmission and shifts the automatic transmission
between its various gears.
[0003] Proper actuation of the shift elements provides smooth
shifting between gears and improves performance of the automatic
transmission. Thus, shift elements preferably adjust between
engaged states and disengaged states in a reliable manner. However,
shift elements can fail to adjust between the engaged and
disengaged states for a variety of reasons. For example, splines of
a shifting element may lock together and hold the shifting element
in the engaged state.
[0004] If a shift elements sticks or does not operate properly,
performance of the automatic transmission can be negatively
affected. For example, if a shift element sticks in an engaged
configuration, the automatic transmission can be overdetermined in
gears that do not require the shift element. However, detecting
proper actuation of the shift elements in order to avoid
overdetermining the automatic transmission can be difficult or
expensive. For example, adding an additional sensor to the
automatic transmission can increase a cost and manufacturing time
of the automatic transmission.
[0005] Accordingly, a method for detecting a nonoperational or
malfunctioning shift element in an automatic transmission would be
useful. In particular, a method for detecting a nonoperational or
malfunctioning shift element in an automatic transmission that does
not require a dedicated sensor for each shifting element of the
automatic transmission would be useful. In addition, a method for
detecting a nonoperational or malfunctioning shift element in an
automatic transmission that also includes steps for operating the
automatic transmission if the shift element is nonoperational or
malfunctioning would be useful.
BRIEF DESCRIPTION OF THE INVENTION
[0006] The present subject matter provides a method for detecting a
malfunctioning shift element in an automatic transmission. The
method includes operating the automatic transmission in an
intermediate gear. A selected shift element of the automatic
transmission is commanded to a disengaged configuration in the
intermediate gear. The method also includes measuring a gear ratio
of the automatic transmission while the automatic transmission is
operating in the intermediate gear, and determining whether the
selected shift element of the automatic transmission is
malfunctioning based at least in part on the gear ratio of the
automatic transmission in the intermediate gear. Additional aspects
and advantages of the invention will be set forth in part in the
following description, or may be apparent from the description, or
may be learned through practice of the invention.
[0007] In a first exemplary embodiment, a method for detecting a
malfunctioning shift element in an automatic transmission is
provided. The method includes terminating a power flow from the
automatic transmission and operating the automatic transmission in
an intermediate gear after the step of terminating. A selected
shift element of the automatic transmission is commanded to a
disengaged configuration when the automatic transmission is in the
intermediate gear. The method also includes measuring a gear ratio
of the automatic transmission in the intermediate gear, and
determining whether the selected shift element of the automatic
transmission is malfunctioning based at least in part on the gear
ratio of the automatic transmission in the intermediate gear.
[0008] In a second exemplary embodiment, a method for detecting a
malfunctioning shift element in an automatic transmission is
provided. The method includes operating the automatic transmission
in an initial gear. A selected shift element of the automatic
transmission is in an engaged configuration when the automatic
transmission is in the initial gear. The method also includes
terminating a power flow from the automatic transmission after the
step of operating the automatic transmission in the initial gear
and shifting the automatic transmission to an intermediate gear
after the step of terminating. The selected shift element of the
automatic transmission is commanded to a disengaged configuration
when the automatic transmission is in the intermediate gear. The
method further includes measuring a gear ratio of the automatic
transmission while the automatic transmission is operating in the
intermediate gear and determining whether the selected shift
element of the automatic transmission is malfunctioning based at
least in part on a difference between the gear ratio of the
automatic transmission in the intermediate gear from the step of
measuring and a predetermined gear ratio.
[0009] In a third exemplary embodiment, a method for detecting a
malfunctioning shift element in an automatic transmission is
provided. The method includes terminating a power flow from the
automatic transmission, operating the automatic transmission in an
intermediate gear after the step of terminating, and measuring a
gear ratio of the automatic transmission in the intermediate gear.
The method also includes step for determining whether the selected
shift element of the automatic transmission is malfunctioning.
[0010] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following description and appended claims. The accompanying
drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the invention and,
together with the description, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] A full and enabling disclosure of the present invention,
including the best mode thereof, directed to one of ordinary skill
in the art, is set forth in the specification, which makes
reference to the appended figures.
[0012] FIG. 1 provides a schematic view of an automatic
transmission according to an exemplary embodiment of the present
subject matter.
[0013] FIG. 2 illustrates a table of an exemplary shifting scheme
as may be used with the exemplary automatic transmission of FIG.
1.
[0014] FIG. 3 illustrates a method for detecting a malfunctioning
shifting element of an automatic transmission according to an
exemplary embodiment of the present subject matter.
[0015] FIGS. 4 and 5 illustrate plots of shifting element actuation
for the exemplary automatic transmission of FIG. 1 during the
exemplary method of FIG. 3.
DETAILED DESCRIPTION
[0016] Reference now will be made in detail to embodiments of the
invention, one or more examples of which are illustrated in the
drawings. Each example is provided by way of explanation of the
invention, not limitation of the invention. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present invention without departing
from the scope or spirit of the invention. For instance, features
illustrated or described as part of one embodiment can be used with
another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0017] FIG. 1 provides a schematic view of an automatic
transmission 10 according to an exemplary embodiment of the present
subject matter. Automatic transmission 10 may be constructed or
arranged in a similar manner to the automatic transmission
described in U.S. Pat. No. 8,398,522 to Bauknecht et al., which is
hereby incorporated by reference for all purposes. Automatic
transmission 10 may be used in any suitable vehicle. For example,
automatic transmission 10 may be used in a passenger vehicle, such
as a car, truck or sport utility vehicle (SUV). Automatic
transmission 10 is configured for selectively adjusting a gear
ratio of automatic transmission 10, as will be understood by those
skilled in the art, in order to provide a suitable mechanical
advantage to propel the associated vehicle.
[0018] As may be seen in FIG. 1, automatic transmission 10 includes
an input shaft 12 and an output shaft 14. Input shaft 12 may be
coupled to a turbine of a torque converter in order to link
automatic transmission 10 to a motor of an associated vehicle.
Output shaft 14 may be coupled a front axle drive shaft of the
associated vehicle. Automatic transmission 10 may change gears in
order to adjust the gear ratio between the motor and front axle
drive shaft of the associated vehicle, as will be understood by
those skilled in the art.
[0019] Automatic transmission 10 also includes four planetary gear
sets: a first planetary gear set 20; a second planetary gear set
22; a third planetary gear set 24 and a fourth planetary gear set
26. In certain exemplary embodiments, as shown in FIG. 1, third and
fourth planetary gear sets 24, 26 may be a Simpson planetary gear
set, e.g., such that third and fourth planetary gear sets 24, 26
share a joint sun gear or sun gears of third and fourth planetary
gear sets 24, 26 are coupled or fixed together. The sun gear of
second planetary gear set 22 may also constitute the ring gear of
first planetary gear set 20, and planet gears of first and second
planetary gear sets 20, 22 may be mounted to a joint planet carrier
that is also coupled or fixedly connected to the ring gear of third
planetary gear set 24. The planet carrier of third planetary gear
set 24 may also be coupled or fixedly connected to the ring gear of
fourth planetary gear set 26.
[0020] As may be seen in FIG. 1, automatic transmission 10 further
includes a plurality of shifting elements. In particular, automatic
transmission 10 includes a plurality of non-positive shift elements
and at least one positive shifting element. The non-positive shift
elements may be any suitable type of non-positive shift elements.
For example, the non-positive shift elements may be multidisc
friction shift elements or friction bands. In the exemplary
embodiment of FIG. 1, the non-positive shifting elements includes a
multidisc clutch B, a multidisc brake C, a multidisc brake D and a
multidisc clutch E. The positive shifting elements may also be any
suitable type of positive shifting elements, e.g., that provide a
form fit or torque proof connection. For example, the positive
shifting elements may be dog clutches, dog brakes or claw clutches.
In the exemplary embodiment of FIG. 1, the at least one positive
shifting element includes a dog clutch A and a dog clutch or brake
F. As used herein, the term "clutch" may refer to mechanism for
coupling or connecting two rotating components and the term "brake"
may refer to a mechanism for coupling or connecting a rotating
component to a non-rotating or static component.
[0021] The shifting elements of automatic transmission 10
selectively adjust between an open or disengaged configuration and
a closed or engaged configuration. In the disengaged configuration,
the shifting elements do not engage an associated component of the
four planetary gear sets, e.g., and do not or negligibly interfere
with rotation of the associated component of the four planetary
gear sets relative to the shifting elements. Conversely, in the
engaged configuration, the shifting elements engage the associated
component of the four planetary gear sets, e.g., and hinder or
prevent rotation of the associated component of the four planetary
gear sets relative to the shifting elements. As may be seen in FIG.
1, dog clutch A selectively connects or couples input shaft 12 to
the sun gear of second planetary gear set 22 and the ring gear of
first planetary gear set 20. Multidisc clutch B selectively
connects or couples input shaft 12 to the sun gear of first
planetary gear set 20. Multidisc brake C selectively connects or
couples a transmission housing 16 to the sun gear of first
planetary gear set 20. Multidisc brake D selectively connects or
couples transmission housing 16 to the ring gear of second
planetary gear set 22. Multidisc clutch E selectively connects or
couples input shaft 12 to the planet carrier of third planetary
gear set 24 and the ring gear of fourth planetary gear set 26. Dog
clutch F selectively connects or couples transmission housing 16 to
the sun gear of third and fourth planetary gear sets 24, 26.
[0022] Automatic transmission 10 also includes an electronic
control unit 28, an input speed sensor 30 and an output speed
sensor 32. Electronic control unit 28 is in operative communication
with various components of automatic transmission 10, including
input speed sensor 30 and output speed sensor 32, to regulate
operation of automatic transmission 10. Electronic control unit 28
may include a memory and microprocessor, such as a general or
special purpose microprocessor operable to execute programming
instructions or micro-control code associated with operating of
automatic transmission 10. The memory may represent random access
memory such as DRAM, or read only memory such as ROM or FLASH.
Alternatively, electronic control unit 28 may be constructed
without using a microprocessor, e.g., using a combination of
discrete analog and/or digital logic circuitry (such as switches,
amplifiers, integrators, comparators, flip-flops, AND gates, and
the like) to perform control functionality instead of relying upon
software.
[0023] Electronic control unit 28 may be mounted on an exterior of
transmission housing 16. Electronic control unit 28 is in operative
communication with solenoid valves of the shifting elements of
automatic transmission 10. Thus, electronic control unit 28 may
selectively adjust the shifting elements between the engaged
configuration and the disengaged configuration, e.g., by
selectively opening and closing the associated solenoid valves of
the shifting elements. In such a manner, electronic control unit 28
may shift automatic transmission 10 between gears during operation
of automatic transmission 10, e.g., based at least in part on
signals from input speed sensor 30 and output speed sensor 32, as
will be understood by those skilled in the art.
[0024] Input speed sensor 30 is configured for measuring a speed,
e.g., rotations per minute (RPM), of input shaft 12. Input speed
sensor 30 may be positioned adjacent input shaft 12 or a turbine of
an associated torque coupling. Input speed sensor 30 may be any
suitable type of sensor. For example, input speed sensor 30 may be
a Hall effect sensor, an optical sensor, etc. Electronic control
unit 28 may receive a signal from input speed sensor 30
corresponding to the speed of input shaft 12.
[0025] Output speed sensor 32 is configured for measuring a speed,
e.g., rotations per minute (RPM), of output shaft 14. Output speed
sensor 32 may be positioned adjacent output shaft 14. Output speed
sensor 32 may be any suitable type of sensor. For example, output
speed sensor 32 may be a Hall effect sensor, an optical sensor,
etc. Electronic control unit 28 may receive a signal from output
speed sensor 32 corresponding to the speed of output shaft 14.
[0026] FIG. 2 illustrates a table 200 of an exemplary shifting
scheme as may be used with automatic transmission 10. As may be
seen in FIG. 2, automatic transmission 10 includes nine forward
gears and one reverse gear. The forwards gears include: first gear
"1", second gear "2", third gear "3", fourth gear "4", fifth gear
"5", sixth gear "6", seventh gear "7", eighth gear "8", and ninth
gear "9". The reverse gear is labeled "R". In table 200, cells
filled with "x" indicate the engaged configuration, and blank cells
indicate the disengaged configuration. Thus, e.g., dog clutch A,
multidisc brake D and dog clutch F are in the engaged configuration
in first gear, and multidisc clutch B, multidisc brake C and
multidisc clutch E are in the disengaged configuration in first
gear. As another example, dog clutch A, multidisc brake C and dog
clutch F are in the engaged configuration in second gear, and
multidisc clutch B, multidisc brake D and multidisc clutch E are in
the disengaged configuration in second gear. In the fourth gear,
dog clutch A, multidisc clutch E and dog clutch F are in the
engaged configuration. It should be understood that in certain
exemplary embodiments, dog clutch A need not be in the engaged
configuration to operate automatic transmission 10 in fourth gear.
Thus, multidisc clutch E and dog clutch F may be the only shifting
elements of automatic transmission 10 in the engaged configuration
to operate automatic transmission 10 in fourth gear, in certain
exemplary embodiments.
[0027] As discussed above, automatic transmission 10 includes nine
forward gears and one reverse gear. Thus, automatic transmission 10
is generally referred to as a "nine-speed automatic transmission."
However, it should be understood that automatic transmission 10 is
provided by way of example only and that the present subject matter
may be used in or with any suitable automatic transmission. Thus,
the present subject matter is not intended to be limited to use
with automatic transmission 10. As an example, the present subject
matter may be used in automatic transmissions having five forward
gears, six forward gears, eight forward gears, etc.
[0028] FIG. 3 illustrates a method 300 for detecting a
malfunctioning shifting element of an automatic transmission
according to an exemplary embodiment of the present subject matter.
Method 300 may be used in or with any suitable transmission. For
example, method 300 may be used with automatic transmission 10
(FIG. 1) to detect malfunctioning of one of the shifting elements
of automatic transmission 10, such as dog clutch F or dog clutch A.
The electronic control unit 28 of automatic transmission 10 may be
programmed or configured to implement method 300. Utilizing method
300, a malfunctioning shifting element of automatic transmission 10
may be detected or identified, e.g., without a dedicated sensor,
and ameliorative steps may be taken to continue operating automatic
transmission 10 with any malfunctioning shifting elements.
[0029] FIGS. 4 and 5 illustrate plots of shifting element actuation
for automatic transmission 10 during method 300. FIG. 4 provides a
plot of shifting element actuation, including actuation of dog
clutch F, with dog clutch F functioning properly by shifting
between the engaged configuration and the disengaged configuration.
FIG. 5 provides a plot of shifting element actuation, including
actuation of dog clutch F, with dog clutch F malfunctioning and
stuck in the engaged configuration such that dog clutch F does not
shift to the disengaged configuration. Method 300 is described in
greater detail below with reference to FIGS. 4 and 5.
[0030] In FIGS. 4 and 5, lines labeled "p_A", "p_F", "p_B" and
"p_E" correspond to a command pressure supplied to dog clutch A,
dog clutch F, multidisc clutch B and multidisc clutch E,
respectively. Electronic control unit 28 may selectively adjust the
command pressure to dog clutch A, dog clutch F, multidisc clutch B
and multidisc clutch E as shown in FIGS. 4 and 5, e.g., by
selectively opening and closing the associated solenoid valves of
the shifting elements. The line labeled "gear ratio" corresponds to
the gear ratio of automatic transmission 10, e.g., measured with
input speed sensor 30 and output speed sensor 32. The time period
labeled "N" corresponds to a period of time when automatic
transmission 10 is operated in a neutral or extended neutral gear,
e.g., and power flow from automatic transmission 10 is interrupted
or terminated. The time period labeled "monitoring" corresponds to
a period of time when automatic transmission 10 is operated in an
intermediate gear.
[0031] At step 310, automatic transmission 10 is operated in an
initial gear. The initial gear may be any suitable gear of
automatic transmission 10. For example, as shown in FIGS. 4 and 5,
the initial gear may be the fourth gear of automatic transmission
10. Thus, dog clutch A, multidisc clutch E and dog clutch F may be
in the engaged configuration at step 310, and multidisc clutch B,
multidisc brake C and multidisc brake D may be in the disengaged
configuration at step 310.
[0032] At step 320, power flow from automatic transmission 10 is
interrupted or terminated, e.g., by shifting automatic transmission
10 to a neutral or extended neutral gear. As an example, at least
one of the non-positive shift elements of automatic transmission 10
may be opened at step 320 in order to interrupt or terminate the
power flow from automatic transmission 10. In particular, if
automatic transmission 10 is in fourth gear at step 310, multidisc
clutch E may be opened to the disengaged configuration at step 320
to terminate or interrupt the power flow from automatic
transmission 10, as shown in FIGS. 4 and 5. Automatic transmission
10 does not deliver power or delivers negligible power to output
shaft 14 of automatic transmission 10 when power flow from
automatic transmission 10 is interrupted or terminated at step 320.
Dog clutch A and dog clutch F may also be commanded to the
disengaged configuration at step 320, as shown in FIGS. 4 and 5,
e.g., in order to assist with interrupting or terminating the power
flow from automatic transmission 10.
[0033] At step 330, automatic transmission 10 is shifted to an
intermediate gear. In the intermediate gear, a selected shift
element of automatic transmission 10 is commanded to the disengaged
configuration. As an example, electronic control unit 28 may close
a solenoid valve of dog clutch F such that a command line pressure
supplied to dog clutch F is reduced, e.g., to zero, in order to
command dog clutch F to adjust to the disengaged configuration at
step 330, as shown in FIGS. 4 and 5. In addition, at step 330, all
shifting elements of automatic transmission 10 that are necessary
for the intermediate gear are actuated to the engaged
configuration. Thus, as shown in FIGS. 4 and 5, multidisc clutch E
may be closed in the intermediate gear at step 330.
[0034] At step 340, a gear ratio of automatic transmission 10 is
measured while automatic transmission 10 is operating in the
intermediate gear. As an example, electronic control unit 28 may
receive speed measurements of input shaft 12 and output shaft 14
from input speed sensor 30 and output speed sensor 32,
respectively, to measure the gear ratio of automatic transmission
10 at step 340. In particular, the ratio of the speed of the input
shaft 12 measured with input speed sensor 30 to the speed of the
output shaft 14 measured with output speed sensor 32 may directly
correspond to the gear ratio of automatic transmission 10.
[0035] Method 300 also includes steps for determining whether the
selected shifting element of automatic transmission 10 is
malfunctioning, e.g., based at least in part on the gear ratio of
automatic transmission 10 in the intermediate gear from step 340,
and for operating manual transmission 10 with a malfunctioning
shift element. Such steps are discussed in greater detail below. At
step 350, the gear ratio of automatic transmission 10 in the
intermediate gear measured at step 340 is compared to a
predetermined gear ratio. The predetermined gear ratio may be any
suitable gear ratio. For example, the predetermined gear ratio may
be an expected gear ratio for the intermediate gear with the
selected shift element in the engaged configuration. Thus, in FIGS.
4 and 5, the predetermined gear ratio may correspond to the
expected gear ratio for fourth gear, e.g., about 1.382:1. In
alternative exemplary embodiments, the predetermined gear ratio may
be an expected gear ratio for the intermediate gear with the
selected shift element in the disengaged configuration.
[0036] At step 350, electronic control unit 28 may determine
whether the gear ratio of automatic transmission 10 in the
intermediate gear measured at step 340 is about (e.g., within five
percent of) equal to the predetermined gear ratio in order to
determine whether the selected shifting element of automatic
transmission 10 is malfunctioning. If the gear ratio of automatic
transmission 10 in the intermediate gear measured at step 340 is
not about equal to the predetermined gear ratio, the selected
shifting element of automatic transmission 10 is not
malfunctioning. As shown in FIG. 4, dog clutch F is commanded to
the disengaged configuration in the intermediate gear. Thus,
because the gear ratio of automatic transmission 10 in the
intermediate gear is substantially different than the predetermined
gear ratio that corresponds to the expected gear ratio for the
intermediate gear with the selected shift element in the engaged
configuration in FIGS. 4 and 5, dog clutch F is in the disengaged
configuration. Conversely, if the gear ratio of automatic
transmission 10 in the intermediate gear measured at step 340 is
about equal to the predetermined gear ratio, the selected shifting
element of automatic transmission 10 is malfunctioning. As shown in
FIG. 5, dog clutch F is commanded to the disengaged configuration
in the intermediate gear. Thus, because the gear ratio of automatic
transmission 10 in the intermediate gear is equal to the
predetermined gear ratio, dog clutch F is stuck in the engaged
configuration and is malfunctioning.
[0037] At step 360, automatic transmission 10 continues to operate
in the intermediate gear if the selected shifting element of
automatic transmission 10 is malfunctioning. Thus, as shown in FIG.
4, automatic transmission 10 continues to operate in the
intermediate gear, e.g., fourth gear, because the dog clutch F is
stuck in the engaged configuration. Conversely, at step 370,
automatic transmission 10 shifts to a subsequent gear if the
selected shifting element of automatic transmission 10 is not
malfunctioning. Thus, as shown in FIG. 5, dog clutch F may be
opened to the disengaged configuration to shift automatic
transmission 10 to fifth gear if dog clutch F is not
malfunctioning.
[0038] In such a manner, method 300 may assist with identifying or
detecting malfunctioning or inoperative shifting elements of
automatic transmission 10. By detecting malfunctioning or
inoperative shifting elements of automatic transmission 10,
operating automatic transmission 10 while automatic transmission 10
is overdetermined can be avoided or prevented. For example, if dog
clutch F is stuck in the engaged configuration, method 300 may
avoid shifting automatic transmission 10 from fourth gear where dog
clutch F is closed to fifth gear where dog clutch F is open. In
particular, automatic transmission 10 may normally shift from
fourth gear to fifth gear when an associated vehicle is moving
downhill. However, if dog clutch F is stuck in the engaged
configuration, method 300 may avoid shifting automatic transmission
10 to fifth gear in order to avoid overdetermining automatic
transmission 10 and potentially damaging automatic transmission
10.
[0039] It should be understood that while described in the context
of automatic transmission 10, method 300 may be used to detect
malfunctioning shifting elements in any suitable transmission. In
addition, while described in the context of detecting
malfunctioning of dog clutch F, method 300 may be used to detect
malfunctioning of any suitable shifting element of automatic
transmission 10. For example, method 300 may be used to detecting
malfunctioning of dog clutch A or multidisc brake C, in alternative
exemplary embodiments.
[0040] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they include structural elements that do not
differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
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