Background of the Invention
Field of the Invention
The present invention relates generally to an automated vehicular
transmission system that includes an engine, a multiple ratio transmission, a
centrifiigally operated master friction clutch for drivingly coupling the engine to the
transmission and a control system for controlling engine output torque.
Description of the Related Art
Automated mechanical transmission systems not requiring the vehicle
driver to operate the vehicle master clutch (so called "two-pedal systems") are known
in the art. To reduce the complexity of these systems, it has been known to provide a
centrifiigally operated friction clutch for drivingly coupling a vehicle engine to the
transmission. Centrifugally operated friction clutches typically include weights
pivotable or rotatable with respect to an engine driven input member that, upon
rotation of an input member, will move radially outwardly under the effect of
centrifiigal force to cause the input member to frictionally engage an output member. When the centrifiigal master friction clutch is engaged and rotational
torque is being transmitted from the vehicle engine to the transmission, there
generally is a large torque load or "torque lock" holding the transmission gears in a
particular position. This torque load makes it quite difficult, if not impossible, to shift
the transmission to neutral or change gears without somehow significantly reducing
the torque load.
One way to relieve torque load is to disengage the master clutch, which
breaks the coupling between the input member and the output member. Disengaging
the master friction clutch permits the torque load to go to zero and allows the operator
or transmission system to shift into neutral or change gears. However, disengaging a
centrifugally operated clutch requires a substantial reduction in the engine speed. If
the engine is generating substantial, uninterrupted power at an engine speed above the
engagement speed of the centrifugally operated clutch, it may be difficult or
impossible to achieve neutral or shift gears in the transmission. Also, shifting the
transmission with the master friction clutch remaining engaged is preferred in many
situations, as such shifts tend to be of a higher shift quality and/or cause less wear on
the drive-line.
Accordingly, a control system and method of operating a vehicular
transmission system is required that breaks torque load between the engine and the
transmission when the engine is generating substantial, iminterrupted power.
Summary of the Invention A control system and method are provided for controlling a vehicular
automated transmission system having an internal combustion engine and a multiple
speed transmission. In accordance with a preferred embodiment of the present
invention, the control system includes an ignition having an output that issues an
ignition signal requesting operation of the engine. The control system also includes a
first control unit that operates the engine in response to receipt of the ignition signal.
A second control unit receives input signals from various system sensors and
processes the signals according to logic rules to issue a command output signal. A
relay disposed between the ignition and the first control unit interrupts transmission of
the ignition signal to the first control unit in response to either the absence or receipt
of the command output signal.
The method of controlling the vehicular automated transmission system
includes the steps of first determining if the automated transmission system is
operating abnonnally and second, interrupting transmission of the ignition signal to
the first control unit when it is determined the automated transmission system is
operating abnonnally.
The inventive control system and method of controlling a vehicular
automated transmission system provides a means of momentarily breaking torque
load to allow a transmission to achieve neutral or to permit a gear change. Among
other advantages, the break in torque load can be achieved independent of the control
of fiiel delivery to the engine. This and other features of the present invention are
particularly advantageous in automated transmission systems that employ a
centrifugally operated master friction clutch, which is generally incapable of being
disengaged when the engine is generating substantial, uninterrupted power.
-[0009]- Various additional aspects and advantages of this invention will become
apparent to those skilled in the art from the following detailed description of the
preferred embodiment, when read in light of the accompanying drawings.
Brief Description of the/drawings The features and inventive aspects of the present invention will become
more apparent upon reading the following detailed description, claims, and drawings,
of which the following is a brief description:
Fig. 1 is a schematic illustration of a vehicular automated transmission
system according to the present invention.
Fig. 2 is a schematic illustration of a preferred embodiment of a control
system for breaking torque load in the vehicular automated transmission system of
Fig. 1.
Figs. 3, 4 and 6 are schematic illustrations, in flowchart format, of the
control logic according to a preferred embodiment of the present invention. Figs. 5 and 7 are schematic illustrations, in flowchart format, of the control
logic according to an alternate embodiment of the present invention.
Description of the Preferred Embodiment Referring now to the drawings, the preferred embodiments of the present
invention are described in detail. An exemplary vehicular automated mechanical
transmission system 10 advantageously utilizing the control system and method of the
present invention is schematically illusfrated in Fig. 1. System 10 generally includes
a fliel-controlled engine 12, a centrifUgal master friction clutch 14 and a multiple-
speed mechanical transmission 16. Engine 12 generally includes a crankshaft 18,
which is attached to an input member 20 of centrifugal master friction clutch 14.
Input member 20 frictionally engages with, and disengages from, an output member
22, which is attached to an input shaft 24 of transmission 16.
Transmission 16 may be of the simple or compound type, having an output
shaft 26 that extends from transmission 16 for driving cormection to the vehicle drive
wheels through a drive axle 28 or transfer case. Transmission 16 may be fully
automated, partially automated, or manual with controller assist, all of which are well
known in the art.
The terms "engaged" and "disengaged," as used in connection with a
master friction clutch, refer to the capacity or lack of capacity, respectively, of the
clutch to transfer a significant amount of torque. Mere random contact of the friction
surfaces, in the absence of at least a minimal clamping force, is not considered
engagement.
As may be seen from Fig. 1, centrifugal clutch 14 requires no external
clutch actuator and is operated as a fiinction of the rotational speed of engine 12.
Centrifugal clutch 14 also requires no connections to operating linkages, command
signal inputs, power electronics and/or fluid power conduits. While the most
economical application of the present invention is with a dry friction clutch, the
present invention is also compatible with wet clutch technology. An engine controller 30, which is preferably electronically and
microprocessor-controlled, is preferably provided for controlling fuel delivery to
engine 12. One or more engine torque or torque limit values may be commanded on,
or read from, an industry standard data link (DL), such as an SAE J-1922, SAE J-
1939 or ISO 11898 compliant data link. By way of example, data links complying
with SAE J1939 or comparable protocol, allow engine controller 30 to issue
commands over the data link for the engine to be fueled in any one of several modes,
such as (i) in accordance with the operator's setting of the throttle, (ii) to achieve a
commanded or target engine speed (ES=ESt), (iii) to maintain engine speed and
engine torque below limits (ESTref, such as a.pproximately three seconds, as shown in steps 106 and 107. This
pause allows system 10 ample time to run a conventional "torque break" routine, such
as by reducing fuel delivery to engine 12 to break the torque load. Following this pause, transmission controller 32 re-evaluates the
operational status of transmission 16, step 108, to determine if the standard torque
interrupt routine allowed transmission 16 to shift to neutral or if the torque load is at a
level suitable for a gear change. Referring to Figs. 4 and 5, transmission controller
32 then proceeds to determine whether system 10 is operating abnormally, warranting
interruption of the ignition signal. As illustrated in the FIGS. 3-7, transition from one
figure to another is labeled with a letter, such as "A" and "B," which denotes the
transition from one schematic illustration to the next.
Referring to Fig. 4, as shown in step 110, transmission controller 32
compares the engine speed (ES) to a threshold value or values (ESref), such as the
engine idle speed, and determines operation of system 10 to be abnormal when the
engine speed exceeds the threshold, i.e., ES> ESref- Referring to Fig. 5, in an
alternate embodiment, transmission controller 32 evaluates the fimctional status of the
data link over which commands are issued for engine fijeling, as shown in step 110'.
A functional fault in the data link may be interpreted to indicate uncontrolled fueling
of engine 12, warranting a determination that operation of system 10 is abnormal. While the preferred system operating parameter and condition usefiil in
determining abnormal operation of system 10 are described above, the described
parameter and condition are not intended to be limited thereto. Alternatively, other
criteria may be evaluated in determining whether operation of system 10 is abnormal.
For example, transmission controller 32 can be programmed to determine whether
system 10, more particularly transmission 14, is operating in a "fallback" mode, as is
known in the art. Operating transmission 16 in a "fallback" mode is generally
indicative of uncontrolled operation of engine 12, particularly in engines whose
operation is not commanded over a data link. Alternatively, transmission controller
32 can be programmed to evaluate any combination of system operating parameters.
For example, the engine speed (ES), the ftmctional status of the data link and whether
transmission 16 is operating in a "fallback" mode may all be evaluated to determine
whether operation of system 10 is abnormal.
Refemng to Figs. 6, when a normally closed relay is employed in control
system 40, transmission controller 32 will issue a command output signal (step 112)
causing relay 42 to open, upon a determination that operation of system 10 is
abnormal. The command output signal is preferably issued only momentarily, such
as, for example, approximately one second or less, allowing relay 42 to briefly
interrupt the ignition signal. Referring to step 114, transmission controller 32 then
pauses a predetermined amount of time, e.g., Tref equal to approximately two to three
seconds, to await compliance with the requested transmission operating mode. The
cycle of issuing a command output signal to relay 42 is repeated, as required, until the
torque load has been relieved to a point were the transmission can be shifted to neutral
or the transmission gears can be changed, as shown in step 116. Referring to Fig. 7, a schematic illustration is shown, in flowchart format,
of the control logic according to an alternate embodiment of the present invention. In
this embodiment, the control logic is programmed to function with a normally open
relay, as opposed to the normally closed relay described above. Transmission
controller 32 is configured to continuously provide a command output signal to relay
42 during normal operation of system 10. Referring to step 112', when operation of
system 10 is determined to be abnormal, transmission controller 32 interrupts
transmission of the command output signal to relay 42. The command output signal
is preferably interrupted only momentarily, e.g., Tref equal to approximately one
second or less, allowing relay 42 to interrupt the ignition signal for a similar period of
time. The cycle of interrupting the command output signal to relay 42 is repeated, as
required, until the torque load has been relieved to a point were the transmission can
be shifted to neutral or the transmission gears can be changed, as shown in step 116'. Although certain preferred embodiments of the present invention have
been described, the invention is not limited to the illustrations described and shown
herein, which are deemed to be merely illustrative of the best modes of carrying out
the invention. A person of ordinary skill in the art will realize that certain
modifications and variations will come within the teachings of this invention and that
such variations and modifications are within its spirit and the scope as defined by the
claims.
WE CLAIM
1. A method for controlling a vehicular automated transmission system (10)
that comprises a torque generating output device, a control unit for
operating the output device in response to receipt of an ignition signal and
a multiple speed transmission (16) having an input member (24) driven by
said output device, the method comprising the steps of :
(a) determining if the automated transmission system (10) Is operating
abnormally by not responding to a command to reduce an output
speed of the torque generating output device; and
(b) reducing output torque by interrupting transmission of the ignition
signal to the control unit when the automated transmission system
is operating abnormally.
2. The method as claimed in claim 1, wherein the torque generating output
device is a fuel controlled internal combustion engine (12), and wherein
the step of determining if the automated transmission system (10) is
operating abnormally is defined by determining if the engine (12) is not
responding to a command to reduce fueling.
3. The method as claimed in claim 1, wherein when an engine controller (30)
for operating the engine (12) in response to receipt of an ignition signal is
provided, the method providing a torque break in the vehicular automated
transmission system (10) that allows the vehicle transmission to achieve
neutral or change gears.

4. The method as claimed in claim 1 or 3, comprising the step of determining
if a transmission neutral mode or a gear change has been selected but not
achieved prior to determining if the automated transmission system (10)
is operating abnormally.
5. The method as claimed in claim 1 or 3, wherein the step of determining if
the automated transmission system (10) is operating abnormally is further
defined by sensing at least one automated transmission system operating
parameter and comparing the operating parameter to a predetermined
reference.
6. The method as claimed in claim 2 or 5, wherein the step of determining if
the transmission system is operating abnormally is further defined by
sensing an operating speed of the output device and determining
operation of the automated transmission system (10) to be abnormally
when the sensed operating speed exceeds a predetermined reference
speed.
7. The method as claimed in claim 1 or 3, wherein the step of determining if
the automated transmission system is operating abnormally is further
defined by evaluating the fault status of a data link and determining
operation of the automated transmission system (10) to be abnormal
when a data link fault exists.
8. The method as claimed in claim 1, wherein the step of determining if the
automated transmission system (10) is operating abnormally is further
defined by sensing if output device control is available and determining
operating of the automated transmission system to be abnormally when
output device control is unavailable.
9. The method as claimed in claim 8, wherein the step of sensing if output
device control is unavailable comprises sensing if the transmission (16) in
a fallback mode.
10. The method as claimed in claim 3 and 4, comprising the step of pausing a
predetermined period of time after determining step to allow the engine
controller to perform a conventional torque break routine.
11.The method as claimed in claim 3, wherein the step of determining if the
automated transmission system is operating abnormally is further defined
by sensing if engine control is available and determining operation of the
automated transmission system to be abnormal when engine control is
unavailable.
12.The method as claimed in claim 11, wherein the step of sensing if engine
control is available comprises sensing if the transmission is in a fallback
mode.
13.A control system (10) for providing a torque break In a vehicular
automated transmission system comprising a fuel powered engine and a
multiple speed transmission (16) that follows a vehicle transmission to
achieve neutral or change gears, comprising:
an ignition(44) having an output that issues an ignition signal;
a first control unit (32) configured to received input signals and process
the signals according to logic rules to issue a command output signal;
a second control unit (30) that operates the engine in response to receipt
of the ignition signal; and
a relay (42) configured to interrupt transmission of the ignition signal
between the ignition and the second control unit in response to either the
absence or receipt of the command output signal.
14.The control system as claimed in 13, wherein the relay (42) is a normally
closed relay.
15.The control as claimed in claim 14, wherein the relay (42) interrupts
transmission of the ignition signal in response to receipt of the command
output signal.
16.The control as claimed in claim 13, wherein the relay (42) is a normally
open relay.
17. The control as claimed in claim 16, wherein the relay (42) interrupts
transmission of the ignition signal in response to the absence of the
command output signal.
IS.The control as claimed in claim 13, wherein a composite control unit
comprises the functionality of both the first and second control units (32,
30).
19. The control as claimed in claim 13, wherein the first control unit (32) is a
transmission controller and the second control unit is an engine controller
(30).
20.The control system as claimed in claim 13, wherein the logic rules are
effective for: issuing the command output signal when the automated
transmission system is (10) operating abnormally.
21.The control as claimed in claim 13, wherein the logic rules are effective
for: interrupting issuance of the command output signal when the
automated transmission system (10) is operating abnormally.

This invention relates to a method for controlling a vehicular automated
transmission system (10) that comprises a torque generating output device, a
control unit for operating the output device in response to receipt of an ignition
signal and a multiple speed transmission (16) having an input member (24)
driven by said output device, the method comprising the steps of; determining if
the automated transmission system (10) is operating abnormally by not
responding to a command to reduce an output speed of the torque generating
output device; and reducing output torque by interrupting transmission of the
ignition signal to the control unit when the automated transmission system is
operating abnormally.