U.S. patent application number 10/985296 was filed with the patent office on 2005-05-19 for ratio control method for a continuously variable transmission.
Invention is credited to Herbster, Kai-Uwe, Iden, Oliver, Sporl, Peter.
Application Number | 20050107935 10/985296 |
Document ID | / |
Family ID | 34559695 |
Filed Date | 2005-05-19 |
United States Patent
Application |
20050107935 |
Kind Code |
A1 |
Herbster, Kai-Uwe ; et
al. |
May 19, 2005 |
Ratio control method for a continuously variable transmission
Abstract
A method for adjusting a ratio of a continuously variable
automatic transmission where a nominal ratio is determined
according to an accelerator pedal signal value. The nominal ratio
is determined according to a modified accelerator pedal signal.
When the periodic curve of the accelerator pedal signal has a
relative extreme value to the modified accelerator pedal signal, a
starting value is assigned which is equal to this extreme value.
Until the value of the modified accelerator pedal signal is again
equal to the value of the unmodified accelerator pedal signal, the
value of the modified accelerator pedal signal is determined by a
transfer function.
Inventors: |
Herbster, Kai-Uwe;
(Friedrichshafen, DE) ; Sporl, Peter; (Ravensburg,
DE) ; Iden, Oliver; (Weissensberg, DE) |
Correspondence
Address: |
DAVIS & BUJOLD, P.L.L.C.
FOURTH FLOOR
500 N. COMMERCIAL STREET
MANCHESTER
NH
03101-1151
US
|
Family ID: |
34559695 |
Appl. No.: |
10/985296 |
Filed: |
November 10, 2004 |
Current U.S.
Class: |
701/51 |
Current CPC
Class: |
F16H 59/18 20130101;
F16H 61/66254 20130101 |
Class at
Publication: |
701/051 |
International
Class: |
G06F 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2003 |
DE |
103 53 978.6 |
Claims
1-6. (canceled)
7. a ratio control method for a continuously variable automatic
transmission having one adjustable variator for a motor vehicle
actuatable by a prime mover, one electronic transmission control
which comprises one control unit with one microcomputer which is
connected with one or more of sensors and external control units,
for detecting operating parameters and with adjusting means which,
depending on control signals of the electronic transmission control
adjusts on the variator, a certain ratio, to the control unit, is
fed an accelerator pedal signal and, depending on the accelerator
pedal signal in the control unit, one nominal ratio is determined,
which is adjusted by the adjusting means in the variator, from the
accelerator pedal signal in the control unit, a modified
accelerator pedal signal is determined, the nominal ratio being
determined according to the modified accelerator pedal signal,
testing whether a periodic curve of the accelerator pedal signal
has a relative extreme value and, in case the relative extreme
value is detected, to the modified accelerator pedal signal is
assigned, departing from a state in which the modified accelerator
pedal signal is assigned is equal to an unmodified accelerator
pedal signal, a starting value (f_start1) which is equal to the
extreme value and that the value of the modified accelerator pedal
signal is determined by a transfer function until the value of the
modified accelerator pedal signal is again the same as the value of
the unmodified accelerator pedal signal.
8. The method according to claim 7, wherein the modified
accelerator pedal signal value determined by the transfer function
is not greater than a sum of the unmodified accelerator pedal
signal value and a maximum positive divergence and not smaller than
a sum of the unmodified accelerator pedal signal value and a
maximum negative divergence.
9. The method according to claim 7, wherein the modified
accelerator pedal signal value determined by the transfer function
is equal to the starting value until one of a maximum positive or a
maximum negative divergence is reached or until the unmodified
accelerator pedal signal value is again equal to the starting
value.
10. The method according to claim 9, wherein the modified
accelerator pedal signal value is suddenly set again equal to the
unmodified accelerator pedal signal value when one of the maximum
positive or the maximum negative divergence is reached.
11. The method according to claim 8, wherein the modified
accelerator pedal signal value determined by the transfer function,
beginning with the starting value, changes rigidly monotonously in
direction of the unmodified accelerator pedal signal value until
the modified accelerator pedal signal value is again equal to the
unmodified accelerator signal value.
12. The method according to claim 11, wherein the modified
accelerator pedal signal value drops linearly with a presettable
gradient (.alpha.) when the modified accelerator pedal signal value
is greater than the unmodified accelerator pedal signal value and a
difference between the two accelerator pedal signal values is
smaller than the maximum positive divergence.
Description
[0001] According to the preamble of the main claim, the invention
concerns a ratio control method for a continuously variable
automatic transmission.
[0002] Both in continuously variable and in infinitely variable
automatic transmission, it is normal to adjust a certain gear or a
certain ratio of a transmission control depending on an accelerator
pedal signal which is fed to the electronic transmission control.
In case of infinitely variable automatic transmissions, any ratio
can be adjusted within a preset ratio range. This can result in any
change of the accelerator pedal signals, however small, leads to a
change of the adjusted ratio. Driving situations exist in which
this leads to undesired ratio adjustments and thus to undesired
rotational speed curves of the prime mover. A situation in which
such an undesired rotational speed variation often occurs is the
following.
[0003] In a drive at constant velocity, a driver continues to
depress the accelerator pedal in order to accelerate. At the end of
this accelerator pedal movement, the driver often goes light on the
gas, that is, he moves again the accelerator pedal in the other
direction so that a corresponding change of the accelerator pedal
signal is also produced. The consequence of this is that the
rotational speed curve of the prime mover has an overshoot not
plausible for the driver since the gas release occurs
involuntarily. Such an effect does not occur in continuously
variable automatic transmission since the gear is always the same
within a certain range of the accelerator pedal signal, that is,
the same transmission ratio.
[0004] Control methods for continuously variable automatic
transmission are known in which only discrete ratio steps are
inserted so as to simulate the behavior of a continuously variable
automatic transmission. Allowance must, of course, be made for the
disadvantage that the prime mover--the same as in multi-speed
automatic transmissions--often is not operated in the optimal
operating range.
[0005] The problem on which the invention is based is to outline a
method for adjusting a ratio of a continuously variable automatic
transmission in which the above mentioned undesired rotational
speed change of the prime mover does not occur without allowance
having to be made for the disadvantages of a system which simulates
the behavior of a multi-speed automatic transmission.
[0006] This problem is solved with a method having the features of
the main claim. Advantageous developments of the method are given
in the sub-claims.
[0007] In the method for ratio adjustment of a continuously
variable automatic transmission with an adjustable variator for a
motor vehicle actuatable by a prime mover with an electronic
transmission control which comprises a control unit with a
microcomputer which is connected with sensors and/or external
control units for detecting operating parameters and with
adjustment means which, depending on control signals of the
electronic transmission control, adjust a specific ratio in the
variator. An accelerator pedal signal is fed to the control unit
and, depending on the accelerator pedal signal in the control unit,
a nominal ratio is detected, which is adjusted by the adjustment
means on the variator, according to the invention. Therefore, from
the accelerator pedal signal in the control unit, a modified
accelerator pedal signal is determined on the basis of which the
nominal ratio is determined. It is tested whether the periodic
course of the accelerator pedal signal has a relative extreme
value, that is, a relative minimum or a relative maximum. In case
such a relative extreme value is detected, to the modified
accelerator pedal signal, departing from a start in which it is
equal to the unmodified accelerator pedal signal, a starting value
is assigned which is equal to the extreme value. The value of the
modified accelerator pedal signal is subsequently determined by a
transfer function until the value of the modified accelerator pedal
signal is again equal to the value of the unmodified accelerator
pedal signal.
[0008] In relation to the above described drive situation, it is
achieved that in case of a vehicle acceleration with subsequent gas
release, after a maximum value of the unmodified accelerator pedal
signal has been detected, the transmission ratio, at least briefly,
is determined not with reference to said unmodified accelerator
pedal signal value but with reference to the modified accelerator
pedal signal formed from the transfer function. The transfer
function can be configured so that there appears a desired
rotational speed change of the prime mover plausible for the
driver.
[0009] In an advantageous development of the invention, the
modified accelerator pedal signal value determined from the
transfer function is not greater than the sum of the unmodified
accelerator pedal signal value and a maximum positive divergence
and not smaller than the sum of the unmodified accelerator pedal
signal value and a maximum negative divergence. The consequence of
this is that great changes of the unmodified accelerator pedal
value, in every case, effect also a corresponding change of the
modified accelerator pedal signal value. Therefore, every
significant actuation of the accelerator pedal by the driver also
has a corresponding reflection upon the modified accelerator pedal
signal and thus upon the transmission ratio that appears while
small changes of the unmodified accelerator pedal signal value,
which are often produced by an involuntary slight actuation of the
accelerator pedal, do not have immediately to result in a change of
ratio.
[0010] In one development of the inventive method, the modified
accelerator pedal signal value determined by the transfer function
is set equal to the starting value--that is, to the detected
extreme value--until the maximum positive or maximum negative
divergence is reached or until the unmodified accelerator pedal
signal value is again equal to the starting value. An advantageous
possibility of again equating the modified accelerator signal value
with the unmodified accelerator pedal signal value is given by the
fact that the modified accelerator pedal signal value is again
suddenly set equal to the unmodified accelerator pedal signal value
when the maximum positive or the maximum negative divergence has
been reached.
[0011] In an alterative method, the modified accelerator pedal
signal value determined by the transfer function, beginning with
the starting value--that is, with the extreme value--changes
rigidly monotonously in direction of the unmodified accelerator
pedal signal value until the modified accelerator pedal signal
value is again equal to the unmodified accelerator pedal signal
value. Hereby a gradual approximation is reached and a jump is
prevented. The signal curve of the modified accelerator pedal
signal can assume the form of every rigidly monotonously ascending
or descending curve. Especially easily applicable is a linear curve
in which the modified accelerator pedal signal value drops linearly
with a presettable gradient when the modified accelerator pedal
signal value is greater than the unmodified accelerator pedal
signal value and the difference between the two accelerator pedal
signal values is smaller than the maximum positive divergence. The
maximum positive or negative divergence is not exceeded. Therefore,
when the maximum divergence is reached, the velocity of change of
the modified accelerator pedal signal value is determined by the
velocity change of the unmodified accelerator pedal signal
value.
[0012] The invention is explained in detail with reference to the
enclosed figures which show:
[0013] FIGS. 1 to 4 show signal curves of the unmodified and of the
modified accelerator pedal signal in a first transfer function;
and
[0014] FIGS. 5 to 7 show corresponding signal curves in a second
transfer function.
[0015] In each Figure, the curve of the unmodified accelerator
pedal signal is shown as solid lines and the curve of the modified
accelerator pedal signal as dotted line. At the moment t_10, the
driver begins to depress the accelerator pedal. Corresponding with
the movement of the accelerator pedal, the value of the accelerator
pedal signal also changes, that is, it rises. At the moment t_11, a
maximum value of the accelerator pedal signal is attained or
exceeded. This is detected by the electronic transmission control.
Departing from the state prevailing up to the moment t_11 in which
the value of the modified accelerator pedal signal is equal to the
value of the unmodified accelerator pedal signal, a starting value
f_start1 is assigned to the modified accelerator pedal signal value
which is equal to the detected extreme value. Up to the moment
t_12, the value of the modified accelerator pedal signal is
determined by a transfer function. The modified accelerator pedal
signal value determined by the transfer function is equal to the
starting value up to the moment t_12 when a maximum positive
divergence of the modified accelerator pedal signal value, compared
to the unmodified accelerator pedal signal value, is reached. At
this moment t_12, the modified accelerator pedal signal value is
suddenly set again equal to the unmodified accelerator pedal signal
value and, in the further curve between the moments t_12 and t_13,
the modified accelerator pedal signal value is again equal to the
unmodified accelerator pedal signal value. For the ratio adjusted
in the continuously variable transmission, the consequence of this
is that the actuation of the accelerator pedal involuntarily
occurring under certain circumstances between the moments t_11 and
t_12 remains without effects. Only when at the moment t_12, the
release of the accelerator pedal by the driver is significant
enough to conclude on its basis that it has been voluntarily
effected does there then also result a corresponding reaction of
the transmission. In this case, therefore, at the moment t_12, a
longer transmission ratio is introduced so that the rotational
speed drops. Beginning with the moment t_12, the reverse case is
shown in which the driver first releases the accelerator pedal and
then, at the t_13 moment, again depresses it. At the moment t_13,
the traversing of a relative minimum is also detected here and to
the modified accelerator pedal signal a transfer function assigns
the constant value f_start3 which is maintained up to the moment
t_14.
[0016] The signal curve, shown in FIG. 2, is equal in the first
phase to the curve shown in FIG. 1. After the maximum value at the
moment t_21 has been detected, the maximum positive divergence from
each other of the two signal values, of course, has not been
reached so that there results no sudden return of the modified
accelerator pedal signal value to the unmodified accelerator pedal
signal value as at the moment t_12 in FIG. 1. Instead of this, the
transfer function at the moment T-23 is terminated by the
unmodified accelerator pedal signal value being again equal to the
until then constantly issued modified accelerator pedal signal
value which corresponds to the starting value.
[0017] In the signal curve shown in FIG. 3, the unmodified
accelerator pedal signal is steadily equal to the modified
accelerator pedal signal, since the releasing phenomenon (the
detection of the relative extreme value) does not occur.
[0018] FIG. 4 shows the case opposite to FIG. 2 in which the driver
releases the accelerator pedal from the moment t_40 to the moment
t_41 and between t_41 and t_43 somewhat depresses it. The maximum
divergence is not attained here, so that between t_41 and t_43, the
constant starting value f_start1 is issued for the modified
accelerator pedal signal.
[0019] The signal curve, shown in FIG. 5, is based on another
transfer function in which the modified accelerator pedal signal
value, beginning with the starting value f_start1, drops linearly
with a presettable gradient a when the modified accelerator pedal
signal value is greater than the unmodified accelerator pedal
signal value and the difference between the two accelerator pedal
signal values is smaller than the maximum positive divergence. At
the moment t_52 is reached, this maximum positive divergence of the
modified accelerator pedal signal value vis-a-vis the unmodified
accelerator pedal signal value. During the phase between the
moments t_52 and t_53, the modified accelerator pedal signal value
is determined by the sum of the unmodified accelerator pedal signal
value and the maximum positive divergence. In the phase between the
moments t_53 and t_54, there always prevails a positive divergence
which, in turn, drops linearly with the gradient a until at the
moment t_54, the modified accelerator pedal signal value is again
equal to the unmodified accelerator pedal signal value.
[0020] The signal curve, shown in FIG. 6, differs from the signal
curve shown in FIG. 5 by the fact that, in the phase between the
moments t_61 and t_63, the positive divergence of the modified
accelerator pedal signal value remains smaller than the maximum
positive divergence. While the modified accelerator pedal signal
value diverges from the unmodified accelerator pedal signal value,
the modified accelerator pedal signal value drops linearly with the
gradient a.
[0021] Finally, FIG. 7 shows a signal curve in which, between the
moments t_72 and t_73, the accelerator pedal is kept constant by
the driver. The positive divergence existing at the moment t_72 is
reduced until the moment t_73 by the modified accelerator pedal
signal value dropping linearly with the gradient .alpha..
* * * * *