BACKGROUND OF THE INVENTION
RELATED APPLICATIONS
[0001] This application is related to copending U.S. Serial No. 09/573,873 filed
05/17/00 and assigned to EATON CORPORATION, assignee of this application.
FIELD OF THE INVENTION
[0002] The present invention relates to a control method/system for controlling
upshifting in an at least partially automated mechanical transmission system. In
particular, the present invention, in one preferred embodiment, relates to the
control of upshifting in a vehicular automated mechanical transmission system
wherein the system senses conditions indicative of a requirement for an upshift
from a currently engaged gear ration (GR) and evaluates, in sequence, the
desirability of unaided upshifts and then upshift brake-assisted upshifts and
commands upshifts deemed desirable.
[0003] The present invention thus provides a control method/system for
controlling upshift brakes in potential upshift brake-aided upshifts as a function
of one or more of the thermal characteristics of the upshift brake, the estimated
current temperature of the brake, the period of time since the previous upshift
brake-aided upshift and/or the expected heat energy generated by the previous
upshift brake-aided upshift and/or the by the upshift under consideration at
differing levels of brake caused retardation.
DESCRIPTTION OF THE PRIOR ART
[0004]Fully or partially automated mechanical transmission systems for vehicular
use are known in the prior art, as may be seen by reference to U.S.Pats. No.
4,361,060; 4,648,290; 4,722,248; 4,850,236;5,389,053;5,487,004; 5,435,212
and 5,755,639, the disclosures of which are incorporated herein by reference.
The use of engine brakes (also known as compression brakes, exhaust brakes or
Jake brakes) and transmission controls utilizing same are
known in the prior art, as may be seen by reference to U.S. Pats. No. 5,409,432
and 5,425,689, the disclosures of which are incorporated herein by reference.
The use of friction devices to retard transmission input shaft rotation,
such as inertia brakes (also known as upshift brakes or input shaft brakes) and
actuators therefor, for providing quicker upshifts is known in the prior art, as r
may be seen by reference to U.S. Pats. No. 5,086,659 and 5,713,445, the '
disclosures of which are incorporated herein by reference.
Controls for automated mechanical transmission systems, especially
wherein shifting is accomplished while maintaining the master clutch engaged,
wherein single and/or skip shift feasibility is evaluated are known in the prior art,
as may be seen by reference to U.S. Pats. No. 4,576,065; 4,916,979;
5,335,566; 5,425,689; 5,272,939; 5,479,345; 5,533,946; 5,582,069;
5,620,392; 5,489,247; 5,490,063; 5,509,867, and 6,149,545, the disclosures
of which are incorporated herein by reference.
Controls for automated mechanical transmission systems including control
of friction upshift brakes are known in the prior art as may be seen by reference
to U.S. Patent No. 6,123,643, the disclosure of which is incorporated herein by
reference.
In the system described inJJ.S. Patent No. 6,149,545, a control for a I
vehicular automated mechanical transmission system will sense conditions
indicative of upshifting from a currently engaged gear ratio, will evaluate, in
sequence, the desirability of large skip upshifts, then single skip upshifts,
unaided single upshifts and then upshift brake-aided single upshifts, and will
command an upshift to the first target ratio deemed to be feasible under current
vehicle operating conditions.
The upshift feasibility rules comprise a two-part test, (a) can the upshift
be completed above a minimum engine speed? and (b) when completed, will the
engine, in the target ratio, provide sufficient torque at the drive wheels to allow
at least a minimum vehicle acceleration? Feasibility of skip and/or single upshifts
also may require that an upshift is expected to be completed within a period of
time less than a maximum acceptable time (T < TMAX?).
SUMMARY OF THE INVENTION
The control of the present invention relates to controlling a friction upshift
brake which may be operated at two or more levels of retardation to provide
variable additional deceleration, during a shift with the master clutch engaged, to
a transmission input shift and the engine crank shaft and master clutch rotating
therewith. This retardation is additive to the natural rate of deceleration of the
engine called "engine speed decay" due to friction and the like. Actuation of the
upshift brake will apply an added retarding force to the input shaft, clutch and,
engine assembly to provide an additional deceleration of the input shaft.
To prevent undue wear and/or damage of friction-type upshift brakes, the
predicted maximum deceleration available from the upshift brake without
causing the brake to overheat (TEMPP < TEMPMAX) is estimated or simulated.
This maximum deceleration is then compared to the deceleration necessary to
complete a potential downshift.
If the additional deceleration needed to complete a shift above a minimal
engine speed and/or within a maximum acceptable time exceeds the maximum
additional deceleration the upshift brake can provide without damage, usually
thermal damage, an upshift into the target gear is not commanded.
an upshift is feasible, the upshift brake will be utilized to provide a
degree of deceleration to allow the shift to occur above the minimum engine
speed, and , if possible, within a desirable period of time (such as, for example,
within 1.2 seconds for a heavy-duty truck).
Accordingly, an improved upshift control for automated mechanical
transmissions is provided which will automatically evaluate and command an
acceptable level of upshift brake actuation for a proposed upshift brake-aided
upshifts and which provides thermal protection for the friction-type upshift
brake.
rpjMSffhis and other objects and advantages of the present invention will
become apparent from a reading of the following description of the preferred
embodiment taken in connection with the attached drawings.
BRIEF DESCRIPTION OF THe/drAWINGS
Fig. 1 is a schematic illustration, in block diagram format, of an automated
mechanical transmission system utilizing the control of the present invention.
Fig. 2 is a schematic illustration, in graphical format, illustrating shift point
profiles for the transmission system of Fig. 1 according to the present invention.
Figs. 3A and 3B are schematic illustrations, in flow chart format, of the
control of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An at least partially automated mechanical transmission system intended
for vehicular use is schematically illustrated in Fig. 1. The automated
transmission system 10 includes a fuel-controlled engine 12 (such as a well-
known diesel engine or the like), a multiple-speed, change-gear transmission 14,
and a non-positive coupling 16 (such as a friction master clutch) drivingly
interposed between the engine and the input shaft 18 of the transmission. The
transmission 14 may be of the compound type comprising a main transmission
section connected in series with a splitter- and/or range-type auxiliary section.
Transmissions of this type, especially as used with heavy-duty vehicles, typically
have 9, 10, 12, 13, 16 or 18 forward speeds. Examples of such transmissions ^
may be seen by reference to U.S. Pats. No. 5,390,561 and 5,737,978, the
disclosures of which are incorporated herein by reference.
A transmission output shaft 20 extends outwardly from the
Transmission 14 and is drivingly connected with the vehicle drive axles 22,
usually by means of a prop shaft 24. The illustrated master friction clutch 16
includes a driving portion 16A connected to the engine crankshaft/ flywheel and
a driven portion 1 6B coupled to the transmission input shaft 18 and adapted to
frictionally engage the driving portion 16A. An upshift brake 26 (also known as
an input shaft brake or inertia brake) may be used for selectively decelerating the
rotational speed of the input shaft 18 for more rapid upshifting, as is well
known. Upshift brake 26 may have two or more selectable levels of retardation
or may be actuated to provide infinitely variable levels of retardation. Friction
type input shaft or upshift brakes are known in the prior art, as may be seen by
reference to U.S. Pats. No. 5,655,407 and 5,713,445.
A microprocessor-based electronic control unit (or ECU) 28 is provided for
receiving input signals 30 and for processing same in accordance with
predetermined logic rules to issue command output signals 32 to various system
actuators, such as upshift brake actuator 26A, and the like. ECU 28 may
include a clock or other timing device 28A. Microprocessor-based controllers of
this type are well known, and an example thereof may be seen by reference to
U.S. Pat. No. 4,595,986.
System 10 includes a rotational speed sensor 34 for sensing rotational
speed of the engine and providing an output signal (ES) indicative thereof, a
rotational speed sensor 36 for sensing the rotational speed of the input shaft 1 6
and providing an output signal (IS) indicative thereof, and a rotational speed
sensor 38 for sensing the rotational speed of the output shaft 20 and providing
an output signal (OS) indicative thereof. A sensor 40 may be provided for
sensing the displacement of the throttle pedal and providing an output signal
(THL) indicative thereof. A shift control console 42 may be provided for
allowing the operator to select an operating mode of the transmission system
and for providing an output signal (GRT) indicative thereof.
Asis known, if the clutch 16 is engaged without slip, the rotational speed
of the engine may be determined from the speed of the input shaft and/or the
speed of the output shaft and the engaged transmission ratio (ES = IS =
0S*GR). Also, with the clutch engaged, input shaft 18, clutch 16 and the
engine flywheel and crankshaft will rotate as a unit.
System 10 also may include sensors 44 and 46 for sensing manual
operation of the vehicle foot brake (also called service brakes) and/or engine
compression brakes (ECB), respectively, and for providing signals FB and EB,
respectively, indicative thereof.
The master clutch 1 6 may be controlled by a clutch pedal 48 or by a
clutch actuator 50 responding to output signals from the ECU 28. Alternatively,
an actuator responsive to control output signals may be provided, which may be
overridden by operation of the manual clutch pedal. In the preferred
//
embodiment, the clutch is manually controlled and used only to launch the
vehicle (see U.S. Pats. No. 4,850.236; 5.272.939 and 5,425,689). The
transmission 14 may include a transmission actuator 52, which responds to
output signals from the ECU 28 and/or which sends input signals to the ECU 28
indicative of the selected position thereof. Shift mechanisms of this type, often
of the so-called X—Y shifter type, are known in the prior art, as may be seen by
reference to U.S. Pats. No. 5,305,240 and 5,219,391. Actuator 52 may shift
the main and/or auxiliary section of transmission 14. The engaged and
disengaged condition of clutch 16 may be sensed by a position sensor (not
shown) or may be determined by comparing the speeds of the engine (ES) and
the input shaft (IS).
Fueling of the engine is preferably controlled by an electronic engine
controller 54, which accepts command signals from and/or provides input
signals to the ECU 28. Preferably, the engine controller 54 will communicate
with an industry standard data link DL which conforms to well-known industry
protocols such as SAE J1922, SAE 1939 and/or ISO 11898. The ECU 28 may
be incorporated within the engine controller 54.
For automated shifting, the ECU 28 must determine when upshifts and
downshifts are required and if a single or skip shift is desirable (see U.S. Pats,
No.4,3361,060;4,576,065;4,916,976;4,947,331 and 6,149,545).
Fig. 2 is a graphical representation of shift point profiles utilized to
determine when shift commands should be issued by the ECU 28 to system
actuators including the shift actuator 52. Line 60 is the default upshift profile,
while line 62 is the default downshift profile. Shift profile 60 is a graphical
representation of the engine speeds at which upshifts from a currently engaged
ratio (GR) are indicated (ESU/S) for various degrees of throttle displacement {i.e.,
demand). As is known, if the vehicle is operating to the right of upshift
profile 60, an upshift of transmission 14 should be commanded, while if the
vehicle is operating to the left of downshift profile 62, a downshift should be
commanded. If the vehicle is operating in between profiles 60 and 62, no
shifting of the transmission is then required.
According to the control of a preferred embodiment of the present
invention, if an upshift from a currently engaged ratio (GR) is required [i.e., if at
current throttle displacement engine speed (ES) is greater than the upshift engine
speed (ESU/S) on shift point profile 60), a sequence is initiated for identifying the
desirable upshift target ratio (GRTARGET), if any. In a preferred embodiment, the
control, in sequence, will evaluate unaided and/or aided skip upshifts and then
unaided single upshifts and then upshift brake-aided single upshifts for
desirability and command an upshift to the first potential target ratio deemed
desirable.
ln a preferred embodiment, a maximum time for completion of an upshift
is established based upon considerations for shift quality, vehicle performance,
etc. For heavy-duty trucks, by way of example, this time value may have a
value of about 0.8 to 2.0 seconds.
A two-part feasibility test is established:
(1) Will the engine speed be at a synchronous value above a
preselected minimum engine speed ESMIN, given current/assumed
engine and vehicle deceleration rates? The ESMiN, by way of
example, is selected at about 1100 to 1300 rpm, which for a
typical heavy-duty diesel engine is at or near a peak torque rpm.
The engine deceleration rate may be evaluated with or without the
use of engine braking. This logic may be appreciated by reference
by U.S. Pats. No. 5,335,566 and 5,425,689, the disclosures of *
which are incorporated herein by reference. The friction upshift
brake 26 may be used separately or in addition to an engine brake.
Use of engine brakes (also called exhaust and Jake brakes) to
enhance upshifting is known, as may be seen by reference to U.S.
Pat_No. 5.409,432; and
(2) At completion of a proposed upshift, will torque at the drive
wheels provide sufficient torque for at least minimal vehicle
acceleration? (See U.S. Pats. No. 5,272,939 and 5,479,345, the *
disclosures of which are incorporated herein by reference.
[0/732] Feasibility also may require that a potential upshift be expected to be
completed in a time (T) less than the maximum acceptable time (T < TMAX). If
one or more of these parts of the feasibility test are not satisfied, the proposed
upshift to an evaluated target ratio (GR + 1,2, 3,...) is not feasible and will not
be commanded.
To provide a maximized upshift braking effect, while thermally protecting
the friction-type upshift brake, the maximum additional input shift deceleration
available using the friction upshift brake 26 is calculated using a simulation
technique wherein the expected brake temperature (TEMPP) at completion of a
potential shift is set equal to a maximum allowable temperature to determine a
maximum additional input shaft deceleration value. For example, as disclosed in
copending application SN 09/573,873, TEMPP , the predicted temperature may
be a calculated or simulated from a relationship such as:
TEMPMAX = TEMPP = TEMP; + TEMPb - TEMPC
where: '
TEMPP = predicted brake temperature at completion of an
upshift brake-aided upshift;
TEMP; = initial (present) brake temperature;
TEMPb = temperature rise due to brake-aided upshift; and
TEMPC = temperature decline during brake-aided upshift.
TEMPi, the simulated initial or present temperature of the brake, is the
greater of (i) a minimum value (about 200°F.) or (ii) the last predicted value
decreased at a selected cooling rate since the last brake actuation (such as -7°F.
per second).
TEMPb, the expected temperature rise due to brake actuation, is a function
of one or more of (i) a target engine deceleration, (ii) the natural engine decay
rate, (iii) engine inertia (I), often available on the data link, (iv) present engine
speed (RPM), (v) step of proposed shift; (vi)t he rate of engine deceleration; and
(vii) a constant.
[QjB36]TEMPc, the cooling during the assisted shift, is a function of (i) a
transmission sump temperature (TEMPS), (ii) an expected shift time and (iii) a
second constant.

As may be seen, the expected temperature of the brake at completion of a
proposed shift (TEMPP) may be simulated using various system parameters and
may be compared or set equal to a maximum reference value (TEMPMAX) (such as
about 350°F.) to determine if upshift brake assist for a particular upshift is
allowable and/or the maximum level of added retardation that the brake can
provide without risk of undue wear or damage.
The parameters used to simulate the predicted temperature (TEMPP) may
include one or more of (i) a simulated initial brake temperature, (ii) time since last
brake actuation, (iii) an estimated brake cooling rate when not active, (iv)
temperature at completion of last assisted upshift, (vi) a desired engine
deceleration rate, (vii) an engine decay rate, (viii) present engine speed, (ix)
synchronous engine speed, (x) engine inertia, (xi) ratio step, (xii) calculated shift
time, (xiii) cooling rate during brake actuation and/or (xiv) various assumed
constants. Of course, less than or more than the above parameters may be
used to estimate or simulate an expected brake temperature (TEMPP). A prior art
temperature simulation technique may be seen by reference to U.S. Pat.
No. 4,576,263, the disclosure of which is incorporated herein by reference.
The "additional deceleration" provided by the upshift brake is deceleration
in addition to the natural decay rate of the engine. The input brake 26 may have
several levels of engine rotational speed retardation or may provide infinitely
valuable levels of retardation.
As used herein, deceleration is taken as a positive quantity, i.e. a greater
retarding force will result in a more positive or greater deceleration. For
example, -5RPM/sec2 is a smaller deceleration then -10RPM/sec2.
ln addition to calculating the maximum allowable additional engine speed
deceleration available from the upshift brake (MAX Decel), the control logic will
also calculate or determine;
a) the additional engine speed deceleration necessary to complete
the shift in a desirable time (Desired Decel). The desirable time
may be, for example, between 1.0 and 1.2 seconds; and
b) the additional engine deceleration necessary to complete the
proposed upshift at above a selected speed engine (Required
Decel).
control logic will then issue command output signals to the
transmission shifter 52, the engine controller 54 and/or the input brake actuator
26A according to the following logic.
If an upshift is required, i.e. if , for a given throttle position, ES is to the
right of upshift profile 60, shifts to a potential target gear ration GRt are
evaluated as follows:
a) if the desired deceleration is less then zero (Desired Decel <0),
then the shift to GRt is initiated without the use of the inertia or
upshift brake 26.
b) if the maximum deceleration is less than the required
deceleration (Max Decel < Required Decel), then the proposed
upshift to GRt is not initiated.
c) if the desired deceleration is greater than zero (Desired Decel
>0) and required deceleration is less than maximum deceleration
(Required Decel < Max Decel) and desired deceleration is greater
than required deceleration (Desired Decel > Required Decel), then
initiate the shift to GRt using the upshift brake 26 at the retardation
level for desired deceleration; and
(d) if the desired deceleration is greater than zero (Desired Decel
>0), and the required deceleration is less than maximum
deceleration (Required Decel < Max Decel) and desired deceleration
is less than required deceleration (Desired Decel < Required Decel)
then initiate the upshift to GRt using the upshift brake 26 at the
retardation level providing required deceleration.
is logic differs from logic utilized for evaluating potential upshifts aided
by engine brakes, as using the engine brake (usually an engine compression
brake) for upshifts is not a first option due to potentially objectionably noisy
and/or slower and/or rough shifting, other than for wear, no such drawback is
associated with use of the friction upshift brake 26.
3A and 3B illustrate the present invention in a flow chart format.
Although the present invention has been described with a certain degree
of particularity, it is understood that the description of the preferred embodiment
is by way of example only and that numerous changes to form and detail are
possible without departing from the spirit and scope of the invention as
hereinafter claimed.
WE CLAIM
1. A method for controlling automatic upshifting in a vehicular automated
mechanical transmission system (10) for a vehicle comprising a fuel-
controlling engine (12), a multiple-speed mechanical transmission (14)
having an input shaft (18) driven by said engine, a friction upshift brake
(26) for selectively retarding rotation of said input shaft, and a controller
(28) for receiving input signals (30) comprising one or more of signals
indicative of engine speed (ES), input shaft speed (IS), engaged gear ratio
(GR) and vehicle speed (OS), and to process said input signals in
accordance with logic rules to issue command output signals (32) to
transmission system actuators comprising a transmission actuator (52)
effective to shift said transmission and a brake actuator (26A) effective to
operate said brake, said brake selectively actuated to provide selected
degrees of retardation to said input shaft for varying input shaft
deceleration, said logic rules comprising rules for:
(a) establishing upshift feasibility criteria whereby upshifts into a
target gear ratio are considered feasible only if, under sensed
vehicle operating conditions, said criteria is satisfied, and
(b) determining if upshifts under consideration are feasible, said
method characterized by the steps of:
(i) establishing a maximum allowable temperature (TEMPMAX) for
said brake;
(ii) determining an expected input shaft declaration (DECAY DECEL)
in the absence of brake actuation;
(iii) determining under current vehicle operating conditions, a
maximum additional input shaft deceleration (MAX DECEL), in
addition to said expected input shaft deceleration, available
without causing brake temperature to exceed said maximum
temperature at completion of an upshift;
(iv) determining a required additional input shaft deceleration (REQ
DECEL), in additional to said expected input shaft deceleration,
required to complete an upshift under current vehicle operating
condition; and satisfying said criteria;
(v) if said maximum additional deceleration is less than said required
additional deceleration (MAX DECEL REQ DECEL), then
initiate said upshift using said brake to provide said desired
additional deceleration;
3. The method as claimed in claim 1, comprising the step of:
(ix) if said desired additional deceleration is less than said required
additional deceleration (DESIRED DECEL < REQ DECEL), then
initiate said upshift using said brake to provide said required
additional deceleration.
4. The method as claimed in claim 1 wherein said reference time is about 0.8
to 1.5 seconds.
5. The method as claimed in claim 1 wherein said reference time is about 1.2
seconds.
6. The method as claimed in claim 1 wherein the determination of said
maximum additional shaft deceleration of step (b) (iii) is determined as a
function of system operating parameters comprising two or more of (a) a
simulated current brake temperature (TEMPj); (b) time since last brake
actuation (t); (c) inertia of engine (I); (d) transmission sump temperature
(TEMPS); (e) ratio step ® of upshift under consideration; and (f) time in
which upshift under consideration is expected to be completed (s).
7. The method as claimed in claim 1 wherein said criteria comprise at least
two of:
(a) upshifts can be accomplished within a time no greater than a
predetermined maximum available time (T