Shift control for automatic transmission with manual shift mode

A vehicle drive train includes an automatic transmission, which has an automatic shift mode and a manual shift mode. The transmission is operable in the automatic shift mode and also operable in the manual shift mode. An input device has a manual select lever. A controller receives an operator mode change demand from the input device and conditions the automatic transmission for operation in one of the automatic and manual shift modes in accordance with the operator mode change demand after a predetermined condition has been met. The predetermined condition is met when the pending shift that is in progress is completed.

FIELD OF THE INVENTION 
The present invention relates to a vehicle drive train including an engine 
and a transmission that is operable in a manual shift mode. More 
particularly, it relates to a shift control for such automatic 
transmission. 
BACKGROUND OF THE INVENTION 
In a vehicle drive train, various gear ratios may be established in an 
automatic transmission. A shift point map stores data that relates the 
transmission gear ratios to various magnitudes of vehicle speed signal and 
engine load signal. Ordinarily, an appropriate one of the gear ratios to 
the current vehicle speed and engine load signals is established in the 
transmission automatically in accordance with the shift point map. A 
vehicle operator can hardly recognize what gear ratio is established in 
the transmission, since shift shocks are reduced to an unnoticeable level. 
Recently, automatic transmissions have been developed, which are operable 
in a manual shift mode. In such automatic transmissions, the vehicle 
operator can manually shift from the current gear ratio up or down to the 
adjacent next gear ratio. 
In such manually ratio controlled automatic transmissions, a manually 
operable select lever has a manual shift mode in addition to an automatic 
shift mode. This select lever in its manual shift mode has an upshift 
position and a downshift position. An operator moves the select lever to 
the manual shift mode and presses the level to the upshift position to 
produce an upshift demand or to the downshift position to produce a 
downshift demand. A transmission controller receives the operator upshift 
or downshift demand and controls a shift from the current gear ratio to 
the adjacent next gear ratio. 
SUMMARY OF THE INVENTION 
In such automatic transmissions, there occur cases where an operator 
selects a manual shift (M) mode through a select lever while a shift in 
gear ratio is in progress in an automatic shift (D) mode. In such cases, 
it is necessary to avoid occurrence of shocks due to an unintentional 
shift in gear ratio. The operator and/or vehicle passenger may feel 
uncomfortable upon occurrence of such shocks. 
Accordingly, an object of the present invention is to provide a smooth 
change in shift mode even when a gear ratio shift is in progress in an 
automatic transmission upon occurrence of an operator mode change demand. 
According to the present invention, there is provided a vehicle drive 
train, comprising: 
an automatic transmission having an automatic shift mode and a manual shift 
mode, said automatic transmission having a plurality of gear ratios and 
being operable in the automatic shift mode, said automatic transmission 
being operable in the manual shift mode; 
an input device; and 
a controller receiving an operator mode change demand from said input 
device and conditioning said automatic transmission for operation in one 
of the automatic and manual shift modes in accordance with the operator 
demand after a predetermined condition has been met.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates an automobile drive train including an engine 1 with a 
throttle valve which opens in degrees as an operator depress a gas or an 
accelerator pedal. A torque converter 2 has an input element in the form 
of a pump impeller 2P, an output element in the form of a turbine runner 
2T and a stator 2S. The pump impeller 2P is connected to an output shaft 
of the engine 1 to be driven thereby. An oil pump O/P is connected to the 
pump impeller 2P to be driven thereby. The turbine runner 2T is connected 
to an input shaft 4 of an automatic transmission 3. Oil is disposed 
between the pump impeller 2P and the turbine runner 2T to provide a 
hydraulic drive between them. This hydraulic drive provides a slip between 
the pump impeller 2P and the turbine runner 2T. 
A torque converter lock-up clutch 2L is situated between the engine output 
shaft and the input shaft 4. In this example, the lock-up clutch 2L forms 
a part of the torque converter 2. When the lock-up clutch 2L is engaged, 
the torque converter 2 locks up, providing mechanical drive without any 
slip. The lock-up clutch 2L defines on one side a lock-up release chamber 
2R and on the opposite side a lock-up application chamber 2A. When oil is 
discharged from the lock-up release chamber 2R, the lock-up clutch 2L is 
engaged. In response to pressure build-up within the lock-up release 
chamber 2R, the lock-up clutch 2L is disengaged toward its release 
position. 
The automatic transmission 3 provides four forward gear ratios and one 
reverse gear ratio between the input shaft 4 and an output shaft 5. The 
drive train including the engine 1, torque converter 2 and the automatic 
transmission 3 is described in JP-A 62-159839 and U.S. Pat. No. 4,680,992 
(issued Jul. 21, 1987 to Hayasaki et al.) that has been incorporated by 
reference in its entirety. 
Briefly explaining, two planetary gear sets, namely a front planetary gear 
set 6 and a rear planetary gear set 7, are situated between the input and 
output shafts 4 and 5. 
Torque transmitting friction units include a forward clutch F/C, a high 
clutch H/C, a band brake B/B, a low one-way clutch L/OWC, a forward 
one-way clutch F/OWC and a reverse clutch R/C. For effective engine 
braking, a low reverse brake LR/B is arranged in parallel with respect to 
the low one-way clutch L/OWC and an overrunning clutch OR/C is arranged in 
parallel with respect to the forward one-way clutch F/OWC. 
The table in FIG. 2(b) shows which one or ones of the torque transmitting 
units should be engaged for each of gear ratios. In this table, the circle 
.smallcircle. indicates engagement and the cross X indicates release. Each 
of the bracketed circle (.smallcircle.) below the low reverse brake LR/B 
and the overrunning clutch OR/C indicates engagement required for 
effective engine braking. Upon demand for engine braking through 
manipulation of an overdrive (OD) inhibitor switch 13, the overrunning 
clutch OR/C is engaged for the third gear ratio. Upon demand for engine 
braking through selection of a II or I range position by a select lever 
15, the overrunning clutch OR/C is engaged for the second gear ratio and 
the low reverse brake LR/B is also engaged for the first gear ratio. 
The automatic transmission provides a gear train for the fourth gear ratio. 
This gear train provides effective engine braking, requiring no additional 
overrunning clutch for effective engine braking. 
For distribution of oil under line pressure, the control valve assembly 8 
includes a shift solenoid A, a shift solenoid B and an overrunning clutch 
solenoid 10. The control valve assembly 8 also includes a lock-up solenoid 
11 for controlling the lock-up clutch 2. The detailed description of the 
control valve assembly 8 with the solenoids A, B, 10 and 11 may be found 
in description from column 5 line 49 to column 29 line 11 of the 
incorporated U.S. Pat. No. 4,680,992. In this description, shift solenoids 
42 and 44 corresponds to the shift solenoids A and B, a solenoid 34 
corresponds to the lock-up solenoid 11, and a solenoid 60 corresponds to 
the overrunning clutch solenoid 10. 
The table in FIG. 2(a) illustrates which one or ones of shift solenoids A 
and B should be energized for each of the four forward gear ratios. In the 
table, the symbol "ON" indicates energized state, and the symbol "OFF" 
indicates de-energized state. 
When the lock-up solenoid 11 is in the state of "ON", the lock-up clutch 2L 
is engaged, causing occurrence of a lock-up application in the torque 
converter 2. When the lock-up solenoid 11 is in the state of "OFF", the 
lock-up clutch 2L is released, causing occurrence of a lock-up release in 
the torque converter 2. The lock-up solenoid 11 is operative to take "ON" 
in response to the presence of a lock-up signal or "OFF" in response to 
the absence of the lock-up signal. 
The solenoids A, B, 10 and 11 are under the control of a controller 14. The 
controller 14 includes an input interface, an output interface, a 
microprocessor unit (MPU), a memory, preferably in the form of a read only 
memory (ROM) and a random access memory (RAM). The memory includes an 
ordinary drive shift point map for a drive range in automatic shift mode 
and a manual drive shift point map for a manual range in manual shift 
mode. The memory also includes a II range engine braking shift point map 
for a II range in automatic shift mode and a I range engine braking shift 
point map for a I range in automatic shift mode. The microprocessor inputs 
appropriate one of the shift point maps to manipulation of the select 
lever 15 of an input device. The select lever 15 has an automatic shift 
(D) mode and a manual shift (M) mode. In the illustrated position in FIG. 
1, the select lever 15 is placed at a D (drive) range in the D mode. In 
the D mode, the select lever 15 has II range and I range, both being 
selected for effective engine braking. In the D mode, the select lever 15 
has a N (neutral) range, a R (reverse) range and a P (park) range. In the 
M mode, the select lever 15 has an upshift "+" position and a downshift 
"-" position. The input device is equipped with a selector switch 16. The 
selector switch 16 produces a selected range signal indicative of a range 
in the D mode, which the select lever 15 is placed at. It also produces an 
engine braking demand signal indicative of an operator engine braking 
demand through the OD inhibitor switch 13. Further, it produces an 
operator upshift demand signal when, in the M mode, the select lever 15 is 
pressed to the upshift "+" position or an operator downshift demand signal 
when, in the M mode, the select lever 15 is pressed to the downshift "-" 
position. 
The selector switch 16 includes a set of M mode selecting switches 19 and 
20 to sense which one of the D mode and M mode the select lever 15 is 
placed at. Each of the M mode selecting switches 19 and 20 produces a 
two-level signal. As shown in FIG. 3, when the select lever 15 is placed 
at the M mode, the signal of the M mode selecting switch 19 takes an ON 
level and the signal of the M mode selecting switch 20 takes an OFF level. 
When the select lever 15 is placed at the D mode and thus not at the M 
mode, the signals of the M mode selecting switches 19 and 20 takes OFF and 
ON levels, respectively. 
A manually operable cancel switch 21 is provided. Through the cancel switch 
21, the operator may cancel the pending shift mode in which the automatic 
transmission 3 operates. The cancel switch 21 produces a two-level signal. 
The controller 14 receives signals from the selector switch 16, the M mode 
selecting switches 19, 20, and the cancel switch 21. 
The controller 14 is connected to an engine load sensor in the form of a 
throttle sensor 17 and a vehicle speed sensor 18. 
The vehicle speed sensor 18 senses, as a first operating parameter 
indicative of vehicle speed, a speed of the transmission output shaft 5 
and produces a vehicle speed signal VSP. The engine load sensor 17 senses, 
as a second operating parameter indicative of the magnitude of engine 
load, an opening degree of the throttle valve of the engine 1 and produces 
an engine load signal TVO. The operator may instruct an engine braking 
demand in the third gear ratio through the OD inhibitor switch 13. 
In the M mode, the select lever 15 is spring biased toward a position away 
from the upshift "+" position and the downshift "-" position. When the 
operator wishes an upshift from the current gear ratio to the next 
adjacent gear ratio, what one has to do is to move the select lever 15 to 
the upshift "+" position. When the operator wishes a downshift from the 
current gear ratio to the next adjacent gear ratio, one has to move the 
select lever 15 to the downshift "-" position. 
In response to selection of the M mode, the controller 14 conditions the 
overrunning clutch solenoid 10 to one of "ON" or "OFF" state to cause 
engagement of the overrunning clutch OR/C for each of the first to third 
gear ratios. The engagement of the overrunning clutch OR/C is released for 
the fourth gear ratio by conditioning the overrunning clutch solenoid 10 
to the other state. For the first gear ratio, the manual valve distributes 
oil under line pressure to the low reverse brake LR/B. Thus, the low 
reverse brake LR/B is engaged in addition to the overrunning clutch OR/C. 
During operation in the manual shift mode, the overrunning clutch OR/C is 
engaged. This provides increased response of the vehicle drive train to 
manipulation of the accelerator pedal by the operator. In comparison with 
the automatic shift mode, the lock-up clutch 2L is engaged over increased 
operating area during operation in the manual shift mode. 
Automatic shift in the D range in the automatic shift mode is briefly 
explained. The controller 14 controls the shift solenoids A and B to 
accomplish a desired gear ratio that has been given after retrieving data 
from the shift point map for the D range using the vehicle speed signal 
VSP and engine load signal TVO. The controller 14 may control the lock-up 
solenoid 11 such that, during operation with the fourth gear ratio, the 
lock-up clutch 2L is engaged when the vehicle speed signal VSP is higher 
than a predetermined vehicle speed and the engine load signal TVO is lower 
than a predetermined engine load. 
In response to the engine braking demand from the OD inhibitor switch 13, 
the controller 14 prohibits an upshift to the fourth gear ratio and 
engages the overrunning clutch OR/C through the solenoid 10 to effect 
engine braking during operation with the third gear ratio. 
When the operator selects the II range through the selector lever 15, the 
controller 14 prohibits an upshift to the third gear ratio and engages the 
overrunning clutch OR/C through the solenoid 10 to effect engine braking 
during operation with the second gear ratio. 
When the operator selects the I range through the selector lever 15, the 
controller 14 prohibits upshift to the second gear ratio and engages the 
overrunning clutch OR/C through the solenoid 10. At the same time, oil 
under line pressure is supplied to the low reverse brake LR/B from the 
manual valve that has been set to the "I" range position. Thus, engine 
braking is effected during operation with the first gear ratio. 
The flow chart of FIG. 4 illustrates a control routine of the preferred 
implementation of the present invention. 
In step S21, the MPU initializes a shift mode flag M.sub.FLG. 
In step 522, the MPU determines whether or not the select lever 15 is 
placed in the M mode. This determination is made based on the levels of 
the signals from the mode selecting switches 19 and 20. If the M mode is 
selected, the routine proceeds to step S23. If this is not the case, the 
routine proceeds to step S27. 
In step S23, the MPU determines whether or not the mode flag MFLG in the 
last cycle was reset to indicate that the automatic shift mode was 
selected in the last cycle. If this is the case, the routine proceeds to 
step S24. If this is not the case, the routine proceeds to step 526. 
In step S24, the MPU determines whether or not a shift in gear position is 
in progress. If this is the case, the routine proceeds to step S25. If 
this is not the case, the routine proceeds to step S26. With regard to the 
procedure to determine whether or not a shift is in progress, reference 
should be made to U.S. Pat. No. 5,119,696 (Yamaguchi) or U.S. Pat. No. 
5,577,979 (lizuka). 
In step 525, the MPU conditions the automatic transmission for operation in 
the automatic shift mode and resets the shift mode flag M.sub.FLG 
(M.sub.FLG =0). 
In step S26, the MPU conditions the automatic transmission 3 for operation 
in the manual shift mode and sets the shift mode flag M.sub.FLG (M.sub.FLG 
=1). 
If, in step 522, the MPU determines that the select lever is not in the M 
mode and thus in the D mode, the routine proceeds to step S27. 
In step 527, the MPU determines whether or not the mode flag MFLG was set 
in the last cycle to indicate that the manual shift mode was selected in 
the last cycle. If this is the case, the routine proceeds to step S28. If 
this is not the case, the routine proceeds to step S30. 
In step S28, the MPU determines whether or not a shift in gear position is 
in progress. If this is the case, the routine proceeds to step S29. If 
this is not the case, the routine proceeds to step S30. 
In step S29, the MPU conditions the automatic transmission for operation in 
the manual shift mode and sets the shift mode flag M.sub.FLG (M.sub.FLG 
=1). 
In step S30, the MPU conditions the automatic transmission 3 for operation 
in the automatic shift mode and resets the shift mode flag M.sub.FLG 
(M.sub.FLG =0). 
The automatic transmission 3 operates in the automatic shift mode when the 
select lever 15 is held in the D mode (steps S22, S27 and S30). 
If now the select lever 15 moves from the D mode to the M mode, it is 
determined whether or not a shift is in progress in the automatic shift 
mode since the shift mode flag M.sub.FLG indicates that the automatic 
shift mode was selected in the last cycle. While the shift is in progress, 
the automatic shift mode is maintained. Even if the operator presses the 
select lever 15 to the upshift "+" or downshift "-" position, the operator 
upshift or downshift demand is disregarded. Thus, the shift proceeds 
without any interference. Since the operator upshift or downshift demand 
is disregarded, the overrunning clutch OR/C or the lock-up clutch 2L will 
not be engaged. 
Upon or immediately after completion of the shift in gear ratio, the 
automatic transmission 3 is conditioned for operation in the manual shift 
mode. 
If, subsequently, the select lever 15 moves back to the D mode, it is 
determined whether or not a shift is in progress in the manual shift mode 
since the shift mode flag M.sub.FLG indicates that the manual shift mode 
was selected in the last cycle. While the shift is in progress, the manual 
shift mode is maintained. Even if there is a shift demand in the automatic 
shift mode, this shift demand is disregarded. Thus, the shift proceeds 
without any interference. Besides, the overrunning clutch OR/C or the 
lock-up clutch 2L will not be disengaged since this mode change is 
disregarded. 
Upon or immediately after completion of the shift in gear ratio, the 
automatic transmission 3 is conditioned for operation in the automatic 
shift mode. 
From the preceding description, it will now be appreciated that a shift in 
progress is completed without any interference even if the select lever 15 
moves to initiate a change in mode between the D mode and M mode. Thus, 
there is no possibility that great shock occur due to establishment of the 
new shift mode while a shift is in progress in the old shift mode. 
The flow chart of FIG. 5 illustrates a modification of the control routine 
shown in FIG. 4. 
The modified control routine in FIG. 5 is substantially the same as the 
control routine illustrated in FIG. 4 except the provision of new steps 
540 and S50. Step S40 is disposed between steps S23 and S24, and step S50 
is disposed between step S27 and step S28. In step S40, the MPU determines 
whether or not the signal from the cancel switch 21 is at ON level. If 
this is the case, the routine proceeds to step S26. If this is not the 
case, the routine proceeds to step S24. In step S50, the MPU determines 
whether or not the signal from the cancel switch 21 is at ON level. If 
this is the case, the routine proceeds to step S30. If this is not the 
case, the routine proceeds to step S28. 
The determination made in steps 540 and 550 may be programmed into main 
control routine of the controller 14. 
From this description, it will be appreciated that the operator can cancel 
the pending shift mode and initiate the new shift mode even if a shift is 
in progress. 
The content of disclosure of Japanese Patent Application No. 10-102568 
(filed Apr. 14, 1998) is hereby incorporated by reference in its entirety. 
The above-described implementation of the present invention is an example 
implementation. Moreover various modifications to the present invention 
may occur to those skilled in the art and will fall within the scope of 
the present invention as set forth below.