U.S. patent application number 09/816228 was filed with the patent office on 2001-10-18 for speed change control system for automatic transmission.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Hanawa, Atsushi, Miyamoto, Koichi.
Application Number | 20010032044 09/816228 |
Document ID | / |
Family ID | 18627965 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010032044 |
Kind Code |
A1 |
Hanawa, Atsushi ; et
al. |
October 18, 2001 |
Speed change control system for automatic transmission
Abstract
A speed change control system for an automatic transmission, for
selectively switching a plurality of speed change control modes of
different speed change control contents to control a gear ratio of
an automatic transmission disposed on an output side of a prime
mover. A first speed change control mode is selected if an output
demand for the prime mover is in a predetermined state, and the
first speed change control mode is switched to a second speed
change control mode, if a physical quantity relating to a speed of
the prime mover is in a predetermined state when the first speed
change control mode is selected.
Inventors: |
Hanawa, Atsushi;
(Nishikamo-gun, JP) ; Miyamoto, Koichi;
(Toyota-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
277 S. WASHINGTON STREET, SUITE 500
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
|
Family ID: |
18627965 |
Appl. No.: |
09/816228 |
Filed: |
March 26, 2001 |
Current U.S.
Class: |
701/51 ; 701/55;
701/95 |
Current CPC
Class: |
F16H 59/14 20130101;
F16H 2061/0227 20130101; F16H 61/0213 20130101 |
Class at
Publication: |
701/51 ; 701/55;
701/95 |
International
Class: |
F16H 061/00; G06F
017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2000 |
JP |
2000-116509 |
Claims
What is claimed is:
1. A speed change control system for an automatic transmission, for
selectively switching a plurality of speed change control modes of
different speed change control contents to control a gear ratio of
an automatic transmission disposed on an output side of a prime
mover, comprising: speed change control mode selecting means for
selecting a first speed change control mode, if an output demand
for said prime mover is in a predetermined state; and speed change
control mode switching means for switching said first speed change
control mode to a second speed change control mode, if a physical
quantity relating to a speed of said prime mover is in a
predetermined state when said first speed change control mode is
selected.
2. A speed change control system for an automatic transmission
according to claim 1, wherein said speed change control mode
selecting means includes means for switching said first speed
change control mode to said second speed change control mode, if
the output demand for said prime mover is the maximum.
3. A speed change control system for an automatic transmission
according to claim 2, wherein said speed change control mode
switching means includes means for inhibiting leaning control means
to correct speed change control contents of said first speed change
control mode, when switching said first speed change control mode
to said second speed change control mode.
4. A speed change control system for an automatic transmission
according to claim 1, wherein said second speed change control mode
has speed change control contents which are easily set to a higher
gear ratio than that in said first speed change control mode.
5. A speed change control system for an automatic transmission
according to claim 1, wherein said second speed change control mode
has speed change control contents which are easily set to a high
gear ratio so that a time period for holding said physical quantity
for a predetermined time period is longer than a time period for
said first speed change control mode.
6. A speed change control system for an automatic transmission
according to claim 1, further comprising: learning control means
for comparing such a target value of said physical quantity at the
time of starting a speed change of said automatic transmission,
which is estimated before the speed change is actually started in
said automatic transmission, and an actual value of said physical
quantity at the time of starting an actual speed change of said
automatic transmission, to correct the speed change control
contents of said first speed change control mode, on the basis of a
comparison result, so that the actual value of said physical
quantity approaches the target value of said physical quantity,
when said first speed change control mode is selected.
7. A speed change control system for an automatic transmission
according to claim 1, wherein the predetermined state of said
physical quantity is generated in a running vehicle, if said
running vehicle pulls another vehicle and runs uphill.
8. A speed change control system for an automatic transmission
according to claim 1, further comprising: estimation means for
estimating said physical quantity at the time of starting the
actual speed change, if the output demand for said prime mover is
in the predetermined state and if said physical quantity is in the
predetermined state, before a speed change decision based on said
first speed change control mode is made, wherein said speed change
control mode switching means includes means for setting the speed
change control contents of said second speed change control mode on
the basis of the physical quantity estimated by said estimation
means.
9. A speed change control system for an automatic transmission
according to claim 1, wherein said speed change control mode
switching means includes means for switching said first speed
change control mode to said second speed change control mode, if
the predetermined state of said physical quantity occurs
consecutively predetermined times within a predetermined time
period.
10. A speed change control system for an automatic transmission
according to claim 1, further comprising: precondition deciding
means for deciding whether or not preconditions for switching said
first speed change control mode to said second speed change control
mode are satisfied.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a system for controlling
the gear ratio of an automatic transmission disposed on the output
side of a prime mover and, more particularly, to a speed change
control system for an automatic transmission, for selectively
switching control modes to control the gear ratio.
[0003] 2. Related Art
[0004] Generally, an automatic transmission having a gear
transmission mechanism is constructed to include: frictional
engagement elements to be applied/released for switching torque
transmission lines of the gear transmission mechanism; a hydraulic
control unit for controlling an oil pressure to be fed to and
discharged from the frictional engagement elements; and an
electronic control unit for controlling the hydraulic control unit.
This electronic control unit is stored with a shift map for
providing references for deciding the switching of a gear ratio of
the automatic transmission. This shift map determines an upshift
line or a downshift line, i.e., shift lines for controlling the
gear ratio of the automatic transmission with parameters indicating
the running state of a vehicle, such as a vehicle speed or an
accelerator depression or opening.
[0005] When a signal indicating the running state of the vehicle is
inputted to the electronic control unit, moreover, a speed change
is decided on the basis of the input signal and the shift map. When
the decision to switch the gear ratio of the automatic transmission
is made, a shift signal is outputted from the electronic control
unit so that the frictional engagement elements are
applied/released to execute the speed change by the hydraulic
control unit.
[0006] On the other hand, the shift map determines the gear ratio
in accordance with the running state, as represented by the vehicle
speed or the accelerator opening, so that the characteristics of
the vehicle change in various ways according to the manner to set
the region of the gear ratio. If the region of a higher gear ratio
is set so far to a running state of a relatively high vehicle
speed, more specifically, the power performance improves. If the
region of a low gear ratio is set to a running state of a
relatively low vehicle speed, on the other hand, the increase in
the speed of the prime mover can be suppressed to take an advantage
for improving the fuel economy. In the prior art, therefore, there
is known a technique, in which there are prepared: a shift map
constructed to have characteristics thinking much of the fuel
economy of the prime mover; and a shift map constructed to have
characteristics thinking much of the power performance of the
vehicle, so that the shift maps are changed by the manual operation
of the driver. In the prior art, moreover, there is proposed a
technique for switching the shift maps of different control
contents automatically according to the change in the running load
on the vehicle.
[0007] One example of the speed change control system for the
automatic transmission, for switching the maps of different speed
change control contents automatically according to the change in
the running load on the vehicle has been disclosed in Japanese
Patent Application Laid-Open No. 6-147304 or 11-51169. In the speed
change control system disclosed in Japanese Patent Application
Laid-Open No. 6-147304, the running load on the vehicle is
estimated on the basis of the vehicle weight, the output torque of
the engine and the vehicle acceleration, and a shift map is
selected on the basis of the estimation result of the running load
on the vehicle. The contents of the shift map thus selected are
different in the speed change control contents for either an
upshift or a downshift. For the upshift, for example, the speed
change control contents are such that the upshift line is set
toward the higher vehicle speed side for the larger vehicle weight
and the heavier load. For the downshift, on the other hand, the
speed change control contents are such that the downshift line is
moved toward the lower degree of throttle opening for the heavier
load. At the time of a heavy load and a large vehicle weight,
therefore, a relatively high gear ratio can be easily selected to
improve the power performance of the vehicle.
[0008] On the other hand, the speed change control system, as
disclosed in Japanese Patent Application Laid-Open No. 11-51169, is
applied to a vehicle such as a tractor for pulling a trailer.
Specifically, the speed control system of this Laid-Open employs a
shift map of such speed change characteristics that a relatively
low gear ratio is easily selected at a light-load time when the
tractor runs by itself. In a heavy-load state where the tractor
runs while pulling the trailer, on the other hand, there is
employed a shift map having contents in which a relatively high
gear ratio is fixed. Thus, shift maps of different kinds are
automatically interchanged on the basis of whether or not the
tractor pulls the trailer, to take advantages in the improvements
in the drivability and in the fuel economy of the prime mover.
[0009] In the control system of this kind for the automatic
transmission, however, the shift map to be used in the heavy-load
running state, i.e., with the accelerator being fully opened, is
prepared such that the upshift line is intrinsically set on the
higher speed side to set the higher gear ratio easily. Considering
the delay, i.e., the response delay of the oil pressure till the
speed change is actually started after the output of a shift
signal, more specifically, the shift map is set so that the engine
speed at the instant when the speed change is actually started may
become a value near the upper limit of an allowable speed. Where
the upshift line of the shift map is set to a higher vehicle speed
side so as to meet the heavy-load demand, as disclosed in the
Laid-Open, therefore, the vehicle speed may rise with the high gear
ratio to cause the so-called "over-rev state" in which the engine
speed exceeds the allowable value to reach the red zone.
[0010] On the other hand, there can be conceived a control, in
which shift maps of different vehicle speeds for setting the
upshift line are prepared for the non-pulling state and the pulling
state and are interchanged by a switching operation. If this
switching operation is mistaken to employ the shift map
corresponding to the tractive state in the non-pulling state,
however, the upshift is not effected till the engine speed exceeds
a predetermined value, and the over-rev state may be invited like
the above.
SUMMARY OF THE INVENTION
[0011] A main object of the invention is to provide a speed change
control system for an automatic transmission, for making a speed
change control of the automatic transmission of a running vehicle
into one suited for a heavy-load running state and for suppressing
the rise of the speed of a prime mover to a predetermined value,
when the running vehicle is in the heavy-load running state such as
when it pulls another vehicle.
[0012] According to the invention, there is provided a speed change
control system for an automatic transmission, for selectively
switching a plurality of speed change control modes of different
speed change control contents to control the gear ratio of an
automatic transmission disposed on the output side of a prime
mover. A first speed change control mode is selected if an output
demand for said prime mover is in a predetermined state, and said
first speed change control mode is switched to a second speed
change control mode if a physical quantity relating to the speed of
said prime mover is in a predetermined state when said first speed
change control mode is selected.
[0013] In the control system of the invention, therefore, the first
speed change control mode is selected if the output demand for the
prime mover is in the predetermined state, and the first speed
change control mode is switched to the second speed change control
mode if the physical quantity relating to the speed of the prime
mover is in a predetermined state when the first speed change
control mode is selected. Therefore, the gear ratio is controlled
according to the changing state of the physical quantity, as caused
by the change in the running load on the vehicle. Up to the vehicle
speed just before the physical quantity relating to the prime mover
speed reaches a predetermined large value, for example, the gear
ratio of the automatic transmission can be kept at a value as high
as possible. As a result, the drive region of the prime mover is so
widened that the power performance of the vehicle may be maximized,
to avoid shortage of the driving force in the case of a heavy-load
run thereby to improve the drivability.
[0014] The above and further objects and novel features of the
invention will more fully appear from the following detailed
description when the same is read with reference to the
accompanying drawings. It is to be expressly understood, however,
that the drawings are for the purpose of illustration only and are
not intended as a definition of the limits to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a flow chart showing one control example to be
used in speed change controls of an automatic transmission in the
invention;
[0016] FIG. 2 is a diagram showing an overall control system
according to the invention;
[0017] FIG. 3 is a diagram illustrating one example of shift maps
to be used in the speed change controls of the automatic
transmission in the invention; and
[0018] FIG. 4 is a diagram illustrating one example of a time chart
corresponding to control contents of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0019] The invention will be specifically described with reference
to the accompanying drawings. FIG. 2 is a block diagram showing an
overall control system of a vehicle to which the invention is
applied. In FIG. 2, the prime mover of the vehicle is exemplified
by an engine 1, which is connected on its output side to an
automatic transmission 2. As the engine 1, there can be used an
internal combustion engine such as a gasoline engine, a Diesel
engine or an LPG engine. This embodiment will be described on the
case in which the gasoline engine is used as the engine 1.
[0020] The engine 1 is provided at its intake pipe 3 with a
throttle valve 4, the opening rate of which is varied on the basis
of the operation of an accelerator pedal 5. There are further
provided a fuel injection control unit 6 for controlling the fuel
feed to the engine 1, and an ignition timing control unit 7 for
controlling the ignition of a mixture of a fuel and air.
[0021] On the other hand, a depression of the accelerator pedal 5,
i.e., an accelerator opening, as indicating an output demand for
the engine 1, is detected by an accelerator pedal switch 8, the
detection signal of which is inputted to an engine electronic
control unit 9. This engine electronic control unit 9 is
constructed of a microcomputer which is composed mainly of a
central processing unit (CPU), a memory unit (RAM, ROM) and an
input/output interface.
[0022] To this engine electronic control unit 9, there are inputted
control data including: a signal of an engine speed sensor 10 for
detecting an engine speed NE; a signal of an intake air flow rate
sensor 11 for detecting an intake air flow rate Q; a signal of an
intake air temperature sensor 12 for detecting an intake air
temperature; a signal of a throttle sensor 13 for detecting the
opening rate of the throttle valve 4; and a signal of an engine
water temperature sensor 14 for detecting an engine water
temperature.
[0023] On the other hand, the automatic transmission 2 is provided
with a gear speed change mechanism 15 constructed of a plurality of
planetary gear mechanisms, and frictional engagement elements 16
including clutches and brakes to be applied/released for switching
the torque transmission lines of the gear speed change mechanism
15. The automatic transmission 2 thus constructed can set a
plurality of forward stages (i.e., gear ratios). These forward
stages are exemplified by 1st to 5th gear stages. Here, a reverse
stage is fixed at a predetermined gear ratio. In other words, the
automatic transmission 2 is the so-called "step type automatic
transmission" capable of switching the gear ratios stepwise.
[0024] On the other hand, the gear ratios of the automatic
transmission 2 are controlled by applying/releasing the frictional
engagement elements 16. For controlling these frictional engagement
elements 16, there is provided a hydraulic control unit 17. This
hydraulic control unit 17 is provided with a manual valve 19, a
plurality of shift solenoids 20, a plurality of shift valves 21 and
a linear solenoid valve 22. The manual valve 19 is activated by the
operation of a shift lever 18 or a kind of the shift position
change-over device. The shift solenoids 20 are electrically
controlled ON/OFF to output signal pressures. On the basis of these
signal pressures outputted from the shift solenoids 20, the shift
valves 21 open/close the oil lines connecting the output port of
the manual valve 19 and the hydraulic chambers of the individual
frictional engagement elements 16, to control the
applications/releases of the individual frictional engagement
elements 16. The linear solenoid valve 22 controls a line pressure
in a hydraulic circuit in accordance with the accelerator opening
or the throttle opening.
[0025] With the hydraulic control unit 17, there is connected an
automatic transmission electronic control unit 23 constructed of a
microcomputer which is composed mainly of a central processing unit
(CPU), a memory unit (RAM, ROM) and an input/output interface. This
automatic transmission electronic control unit 23 and the engine
electronic control unit 9 are connected with each other for data
communications. To the automatic transmission electronic control
unit 23, moreover, there are inputted: a signal of a turbine speed
sensor 24 for detecting the turbine speed (or the input speed) of
the automatic transmission 2; a signal of an output speed sensor 25
for detecting the output speed of the automatic transmission 2; a
signal of an oil temperature sensor 26 for detecting the working
oil temperature of the hydraulic control unit 17; and a signal of a
shift position sensor 27 for detecting the operation of the shift
lever 18. Here, the vehicle speed is calculated on the basis of the
output speed sensor 25.
[0026] In the engine electronic control unit 9 and the automatic
transmission electronic control unit 23, moreover, the data, as
detected by the various sensors and switches, are processed to
decide the running state or the running load of the vehicle. On the
basis of these decision results, it is performed to control the
fuel injection rate by the fuel injection control unit 6, the
ignition timing by the ignition timing control unit 7 and the gear
ratio of the automatic transmission 2.
[0027] In this automatic transmission 2 thus constructed, the shift
lever 18 can be manually operated to selectively switch the
individual shift positions including a P (Parking) position, an R
(Reverse) position, an N (Neutral) position, a D (Drive) position,
a "4" position, a "3" position, a "2" position and an L (Low)
position. Of these shift positions, the D (Drive) position, the "4"
position, the "3" position, the "2" position and the L (Low)
position belong to the forward drive positions.
[0028] In the D-position, the gear stage can be selectively
switched within the speed range (i.e., the shift range) of the 1st
to the 5th speeds; in the "4" -position, the gear stage can be
selectively switched within the speed range of the 1st to the 4th
speeds; in the "3"-position, the gear stage can be selectively
switched within the speed range of the 1st to the 3rd speeds; in
the "2"-position, the gear stage can be selectively switched within
the speed range of the 1st and the 2nd speeds; and in the
L-position, the gear stage is fixed at the 1st speed. Here, it is
apparent that as the numeral indicating the gear stage becomes the
larger, the gear ratio becomes the lower.
[0029] On the other hand, the automatic transmission electronic
control unit 23 is stored with the well-known shift maps (although
not shown) for controlling the speed change of the automatic
transmission 2. In these shift maps, the running states of the
vehicle such as the accelerator opening and the vehicle speed are
used as parameters to set shift lines to be used as a decision
reference for switching the gear stage of the automatic
transmission 2, as specified by an upshift line and a downshift
line.
[0030] On the basis of both the data including the accelerator
opening and the vehicle speed, as inputted to the automatic
transmission electronic control unit 23, and the shift maps,
moreover, the speed change decision is made on whether or not the
gear stage of the automatic transmission 2 is to be switched. If
this speed change decision is satisfied, moreover, the shift signal
is outputted from the automatic transmission electronic control
unit 23 to control the ON/OFF of the individual shift solenoids 20,
and the applications/releases of the individual frictional
engagement elements 16 are controlled by the actions of the
individual shift valves 21, so that the speed change is executed.
In the corresponding relation between the aforementioned specific
construction and the construction of the invention, the engine 1
corresponds to the prime mover of the invention.
[0031] Here will be described controls to change the speed change
control mode of the automatic transmission 2 of a running vehicle,
where this vehicle is in a single running state and where the
vehicle is in a traction running state and in a heavy-load running
state. Here, the "single running state" means that the vehicle is
running without pulling another vehicle, namely, that the vehicle
is running in a light load. Moreover, the "single running state"
may be conveniently expressed by the "ordinary running state". On
the contrary, the "traction running state" means that the vehicle
is running while pulling another. Here, the "traction running
state" may be conveniently expressed simply by the "tractive
state". Moreover, the "heavy-load running state" means that the
vehicle is running uphill. Here in this specific embodiment, it is
enumerated as the heavy-load running state that the accelerator or
the throttle is fully opened in the traction running state.
[0032] FIG. 3 illustrates a portion of one example of the shift
maps which are used for controlling the speed changes of the
automatic transmission 2 in the tractive state. In FIG. 3, there
are inclusively illustrated: shift maps which are used in the
ordinary running state (as will be called the "first shift maps");
and shift maps which are used where the running state is tractive
and under a heavy load and where the changes in the physical
quantity relating to the engine speed are at a predetermined value
or lower (as will be called the "second shift maps"). The shift
maps of FIG. 3 are provided, by using the vehicle speed and the
accelerator opening as the parameters, with upshift lines (or
upshift points) for a decision reference for the upshift from the
1st to the 2nd speeds, and downshift lines (or downshift points)
for a decision reference for the downshift from the 2nd to the 1st
speeds.
[0033] In FIG. 3, the upshift line to be used in the ordinary
running state is illustrated by a broken line, and the downshift
line to be used in the ordinary running state is illustrated by
double-dotted line. On the other hand, the upshift line to be used
where the running state is under the heavy load and where the
changes in the physical quantity relating to the engine speed are
at the predetermined value or lower is illustrated by a solid line.
Moreover, the downshift line to be used where the vehicle is
running in the tractive state and under the heavy load and where
the changes in the physical quantity relating to the engine speed
are at the predetermined value or lower is indicated by the
single-dotted line.
[0034] As illustrated in FIG. 3, the upshift line of the second
shift map is set on the higher vehicle speed side than the upshift
line of the first shift map. Moreover, the downshift line of the
second shift map is set on the higher vehicle speed side than the
downshift line of the first shift map. In short, the second shift
map is so characterized that the higher gear ratio (i.e., the 1st
speed) is more easily set than the first shift map. Here, the shift
maps for the ordinary running state, as illustrated in FIG. 3, can
be used, if the changes in the physical quantity relating the
engine speed exceed a predetermined value even where the vehicle is
in the tractive state and under the heavy load.
[0035] Here, the shift maps illustrated in FIG. 3 correspond to the
state in which the D-position are selected, but shift maps similar
to those of FIG. 3 can be used if the shift position is at a
forward running one other than the L-position. Although not
illustrated, on the other hand, the first shift map and the second
shift map to be used in the case of an upshift or a downshift
between the gear stages of the 2nd to the 5th speeds can also be
set to characteristics similar to the first shift map and the
second shift map illustrated in FIG. 3. In other words, the first
shift map and the second shift map to be used in the case of the
upshift or the downshift between the 2nd to the 5th gear stages are
so determined on their upshift lines and downshift lines that the
second shift map may set the relatively higher gear ratio more
easily than the first shift map.
[0036] As the method of switching the first shift map and the
second shift map, there can be enumerated a method of storing the
two shift maps separately in advance in the automatic transmission
electronic control unit 23 so that the shift maps may be
interchanged, and a method of achieving the second shift map by
correcting the first shift map.
[0037] Here will be described the speed change control of the
automatic transmission 2 with reference to the flow chart of FIG.
1. First of all, it is decided (at Step S1) whether or not there
are satisfied preconditions for switching from the first shift map
corresponding to the ordinary running state of the driven car to
the second shift map corresponding to the traction running state of
the car. These preconditions are satisfied if it is affirmed that
the D-position is selected, that the 1st speed is set, that the
control of the engine torque is not inhibited, and that the systems
of the electronic control units 9 and 23, the hydraulic control
unit 17 and the various sensors and switches are normal. In short,
it is confirmed at Step S1 whether or not the system of the vehicle
is normal and the engine 1 has completed its warming-up to have a
stabilized combustion state. If the answer of Step S1 is NO, the
routine is returned.
[0038] If the answer of Step S1 is YES, it is decided (at Step S2)
whether or not the throttle or the accelerator is fully opened. If
the answer of Step S2 is NO, the running vehicle is under a light
load so that the routine is returned.
[0039] At the instant when the answer of Step S2 is YES, there is
selected the first shift map, as illustrated in FIG. 3. On the
basis of this first shift map, it is then decided (at Step S3)
whether or not the present vehicle speed is one just before the
upshift from the 1st speed to the 2nd speed. If the answer of Step
S3 is NO, the routine is returned as it is.
[0040] If the answer of Step S3 is YES, on the contrary, the
changing rate of the vehicle speed for a predetermined time period,
i.e., an acceleration is estimated (at Step S4) on the basis of the
changing state (i.e., the variation or the rate of change) of the
present vehicle speed. It is further decided (at Step S5) whether
or not the changing rate of the vehicle speed estimated at Step S4
is no more than a threshold value. This threshold value is stored
in advance in the automatic transmission electronic control unit
23. In other words, Step S5 decides, on the basis of the estimated
result of the changing rate of the vehicle speed, whether or not
the running vehicle is running uphill (i.e., in the heavy-load
running state). On the basis of this changing rate of the vehicle
speed, it is also possible to estimate the slope of the road on
which the vehicle runs uphill.
[0041] If the answer of Step S5 is YES, it is decided (at Step S6)
whether or not the state, in which the actual changing rate of the
vehicle speed is no more than the threshold value, occurs
consecutively more than times of reference number N within a
predetermined time period. This decision of Step S6 confirms
whether or not the heavy-load running state occurs
consecutively.
[0042] If the answer of Step S6 is YES, there is fixed (at Step S7)
the decision that the vehicle is in the traction running state and
in the heavy-load running state. At the same time, the speed change
control on the basis of the first shift map is quit and switched
(at Step S8) to the speed change control on the basis of the second
shift map, and this control routine is ended.
[0043] Here will be specifically described the controls of Step S8
by comparing the speed change control on the first shift map with
the speed change control on the second shift map. First of all, an
example of the speed change control of the automatic transmission 2
merely in the tractive state will be described with reference to
the time chart of FIG. 4. FIG. 4 illustrates the time changes of
the physical quantity (i.e., the physical quantity changing in
accordance with the change in the running load and relating to the
vehicle speed). These physical quantities are exemplified by the
engine speed, the turbine speed or the output speed, of which the
engine speed is conveniently adopted. In FIG. 4, the changing
characteristics corresponding to the first shift map are
illustrated by a broken line, and the changing characteristics
corresponding to the second shift map are illustrated by a solid
line.
[0044] Where the first shift map is selected, as described above,
before the decision of a speed change of the upshift from the 1st
to the 2nd speeds is made at time t1, the changing state of the
physical quantity at the instant when the speed change is actually
started is estimated, on the basis of the changing state (i.e., the
variation or the rate of change) of the physical quantity relating
to the engine speed at that instant.
[0045] On the basis of this decision result, moreover, there is
calculated the timing at which the shift signal is outputted. After
the shift signal was outputted and before the speed change is
actually started (i.e., before an inertia phase is started), there
arises a response delay time. By considering this response delay
time, therefore, the output timing of the shift signal is
calculated so that the engine speed at the instant when the upshift
is started may be slightly lower than the allowable speed of the
engine 1. Here, the response delay time is the delay time which is
based on the mechanical causes in the hydraulic circuit such as the
applications/releases of the frictional engagement elements 16 by
feeding/discharging the oil pressure.
[0046] Thus in the traction running state, there is determined the
time period after the upshift decision was made and before the
shift signal is outputted. Moreover: at time t1, the speed change
decision is made; at time t2, the shift signal is outputted; and at
time t4, the upshift is actually started. Then, the engine speed
begins to fall, but then gradually rises after the speed change is
completed at time t5.
[0047] Where the routine advances to Step S8, on the other hand,
the shift map is switched from the first to the second ones. Before
this switching of the shift maps, here will be described the
upshift line, as illustrated by the solid line in FIG. 3.
[0048] First of all, before the speed change decision on the basis
of the first shift map is made, on the basis of the changing state
of the physical quantity (i.e., at least one of the output shaft
speed, the engine speed and the turbine speed) relating to the
engine speed at that instant, there is estimated the physical
quantity at the instant when the speed change is actually started.
This estimation is made on the basis of the data of Step S4 as
described above. At the time of estimating the physical quantity,
on the other hand, there is considered the response delay time for
the period after the shift signal was outputted and before the
speed change is actually started. Then, the timing of outputting
the shift signal is calculated so that the engine speed at the time
of starting the speed change actually may be slightly lower than
the allowable speed.
[0049] Even where the second shift map is thus used, too, the time
period from the speed change decision to the output of the shift
signal is determined so that it may be longer than that in the
aforementioned case in which the speed change is executed on the
basis of the first shift map. Specifically, the upshift line is set
to a relatively higher speed side, as illustrated by the solid line
in FIG. 3. Thus, the timing for the upshift is delayed till the
vehicle speed rises, thereby to elongate relatively the time period
from the instant of the speed change decision to the output of the
shift signal.
[0050] Here will be described the contents of the speed change
control corresponding to the second shift map with reference to the
time chart of FIG. 4. Assuming the state in which the upshift
decision from the 1st to the 2nd speeds based on the first shift
map and the upshift decision from the 1st to the 2nd speeds based
on the second shift map are made at the identical time t1, FIG. 4
illustrates the two speed change control contents in contrast.
Since the broken upshift line and the solid upshift line have the
different vehicle speeds for the references to the speed change
decisions of the upshifts, as illustrated in FIG. 3, the engine
speeds at the time t1 when the upshift decision is made in FIG. 4
are different between in the ordinary running state and in the
traction running and the heavy-load running state. Since the time
period after the speed change decision in the traction running
state and in the heavy-load running state was made and before the
shift signal is outputted is set longer than the time period from
the speed change decision in the ordinary running state was made
and before the shift signal is outputted, as described
hereinbefore, the shift signal is outputted not at the time t2 but
at later time t3, when the vehicle is in the traction running state
and in the heavy-load running state.
[0051] Even in the case of the traction running state and the
high-load running state, too, the engine speed has risen for a
predetermined time period after the shift signal was outputted.
When the upshift is actually started at time t6 after the response
delay time elapsed from the output of the shift signal, the engine
speed has further fallen from the state of the speed of a red zone
NE1 or lower. On and after time t7 when the upshift is completed,
the engine speed gradually rises.
[0052] In this specific embodiment thus far described, on the basis
of the loss, i.e., the difference between the estimated value of
the changing state of the engine speed at the instant of starting
the speed change in the traction running state and the estimated
value of the changing state of the engine speed at the instant of
starting the speed change in the traction running state and in the
heavy-load running state, the output timing of the shift signal in
the traction running state and in the heavy-load running state is
delayed from the output timing of the shift signal in the ordinary
running state. This delay is equivalent to that the second output
speed, at which the shift signal is outputted in the traction
running state and in the heavy-load running state, is set to the
summed value of a predetermined speed .alpha. and the first output
speed, at which the shift signal is outputted in the ordinary
running state, if it is assumed, as shown in FIG. 4, that the
timing at which the speed change decision is made in the ordinary
running state is identical to the timing at which the speed change
decision is made in the traction running state and in the
heavy-load running state.
[0053] Here at the foregoing Steps S4, S5 and S8, the variation of
the output speed (i.e., the vehicle speed) can be replaced by other
data capable of making a highly precise decision on whether or not
the engine 1 becomes an over-rev, such as the variation of the
engine speed or the variation of the turbine speed. Specifically:
at Step S4, the variation of the engine speed is calculated; at
Step S5, it is decided whether or not the variation of the engine
speed, as calculated at Step S4, is less than the threshold value;
if the answer of Step S5 is YES, it is decided at Step S6 whether
or not the state of the variation of the engine speed less than the
threshold value occurs consecutive N times or more within the
predetermined time period; and if the answer of Step S6 is YES, the
routine advances via Step S7 to Step S8.
[0054] Where the variation of the turbine speed is used, on the
other hand: at Step S4, the variation of the turbine speed is
calculated; at Step S5, it is decided whether or not the variation
of the turbine speed, as calculated at Step S4, is less than the
threshold value; if the answer of Step S5 is YES, it is decided at
Step S6 whether or not the state of the variation of the turbine
speed less than the threshold value occurs consecutive N times or
more within the predetermined time period; and if the answer of
Step S6 is YES, the routine advances via Step S7 to Step S8.
[0055] Here in the control example thus far described, as
illustrated in FIG. 3, there is used the shift map in which the set
vehicle speeds of the upshift line are made different between the
ordinary running state, and the traction running state and the
heavy-load running state. At the same time, the time period after
the speed change decision was made and before the shift signal is
outputted is set longer in the traction running state and the
heavy-load running state than in the ordinary running state, so
that the output timing of the shift signal in the traction running
state and the heavy-load running state is delayed more than the
output timing of the shift signal in the ordinary running state. By
another control method, however, the output timing of the shift
signal in the traction running state and the heavy-load running
state can also be delayed more than the output timing of the shift
signal in the ordinary running state.
[0056] For example, at the time of executing the control example of
FIG. 1, the shift map to be used at Step S3 is made an identical
shift map for the case of the ordinary running state and for the
case of the traction running state and the heavy-load running
state. In short, the vehicle speeds for setting the upshift lines
are made identical. Where the speed change control of the automatic
transmission 2 is to be made on the basis of the common shift map,
moreover, if the answer of Step S6 is YES, the routine advances via
Step S7 to Step S8. At this Step S8, a delay timer is used so that
the time period after the speed change decision was made and before
the shift signal is outputted may be longer in the traction running
state and the heavy-load running state than in the ordinary running
state.
[0057] In this specific embodiment, as has been described
hereinbefore, before the speed change decision based on the first
shift map used in the ordinary running state is made, there is
estimated the changing state of the physical quantity relating to
the engine speed after the speed change decision was made
(specifically, after the shift signal was outputted and before the
speed change is actually started). Where the estimated result is no
less than the threshold value, there is processed the second shift
map in which the output timing of the shift signal in the traction
running state and the heavy-load running state is delayed more than
the output timing of the shift signal in the ordinary running
state. Thus, there is made the control to switch the first shift
map to the second shift map. Where the vehicle is in the traction
running state and in the heavy-load running state, therefore, the
gear stage of the automatic transmission 2 can be kept at the 1st
speed so long as to a high vehicle speed just before the engine
speed reaches a value corresponding to the red zone NE1. Therefore,
the running state, in which the drive region (at a predetermined
high speed) for a high engine output can be employed, is enlarged
to improve the power performance in the case in which the running
vehicle runs uphill while pulling another vehicle, so that the
drivability can be improved.
[0058] Where the vehicle runs on a highland, the density of the
intake air is lower than that in the case of running on a lowland.
Therefore, the air/fuel ratio changes to make the combustion state
of the engine unstable, and the engine output may fall. In the case
of running on the highland, too, the power performance of the
vehicle can be improved by making the control of FIG. 1.
[0059] In the state where the first shift map is selected, on the
other hand, at Step S4 of FIG. 1, the following learning control
can be made in addition to the aforementioned control (i.e., the
control to estimate the variation of the vehicle speed within the
predetermined time period on the basis of the changing state of the
prevailing vehicle speed). Specifically, before the speed change of
the automatic transmission 2 is started, the target value of the
physical quantity at the time of starting the speed change of the
automatic transmission 2 is set on the basis of the variation of
the vehicle speed estimated by the aforementioned control. Then,
the speed change decision is made to output the shift signal, and
the actual value of the physical quantity relating to the engine
speed at the time of starting the actual speed change of the
automatic transmission 2 is detected. Then, the target value of the
physical quantity and the actual value of the physical quantity are
compared, and a control is made to correct (or change) the set
vehicle speed of the upshift line of the first shift map on the
basis of that comparison result so that the actual value of the
physical quantity may approach the target value of the physical
quantity.
[0060] Where the learning control thus far described is made at
Step S4 and where the routine advances to Step S8 at which the
first shift map is switched to the second shift map, it is
inhibited to correct the speed change control contents of the first
shift map. In other words, the control to change the speed change
control mode, as based on whether the heavy-load running state is
or not, is preferred to the correction of the speed change control
contents by the learning control. By thus inhibiting the learning
control, it is made possible to avoid the interference between the
correction of the speed change control contents by the learning
control and the change in the speed change control mode based on
whether the heavy-load running state is or not. Thus, it is
possible to prevent the speed change control contents, as suited
for the traction running state and the heavy-load running state,
from being reflected on the speed change control contents of the
first shift map.
[0061] Where the answer of Step S5 or S6 is NO, the routine returns
to Step S1, at which the shift map corresponding to the ordinary
running state is continuously selected. Here, the preconditions of
Step S1 contain whether the D-position is or not, but may contain
the forward running position to be shifted from the 1st to 2nd
speeds, such as the "2"-position to "4" position in their decision
references.
[0062] Here will be described the relations between the specific
embodiment thus far described and the invention. The functional
means for executing the controls of Step S1 to Step S3 shown in
FIG. 1 corresponds to speed change control mode selecting means of
the invention; the functional means for executing the controls of
Step S4 to Step S8 shown in FIG. 1 corresponds to speed change
control mode switching means of the invention; the functional means
for executing the control of Step S1 shown in FIG. 1 corresponds to
precondition decision means of the invention; and the functional
means for executing the control of Step S4 shown in FIG. 1
corresponds to learning control means of the invention. On the
other hand: the speed change based on the first shift map
illustrated in FIG. 3 corresponds to the first speed change control
mode of the invention; the speed change based on the second shift
map illustrated in FIG. 3 corresponds to the second speed change
control mode of the invention; the upshift lines to be used in FIG.
3 for the decision of the upshift, the downshift lines to be used
for the decision of the downshift, and the time period after the
speed change decision based on the shift map illustrated in FIG. 3
and before the shift signal is outputted correspond to the speed
change control contents of the invention; "the state in which the
engine speed is slightly lower than the allowable speed of the
engine 1" corresponds to "the physical quantity is in the
predetermined state"; "the state in which the output demand is the
maximum" corresponds to "the output demand is in the predetermined
state"; and the engine 1 shown in FIG. 2 corresponds to the prime
mover of the invention.
[0063] Here, the foregoing embodiment has been described on the
so-called "step type automatic transmission" which can switch its
gear ratio stepwise, but the control example shown in FIG. 1 could
be applied to the continuously variable transmission which can vary
its gear ratio continuously (or steplessly).
* * * * *