Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: TRANSMISSION SYSTEM
FIELD OF THE INVENTION
The present invention relates to an advantageous
structure of a switch used for mode selection and shift
operation at the time of stepping speed change, which
switch is used for a transmission system including an
automatic transmission capable of switching an automatic
speed change mode allowing continuously variable speed
change to or from a stepping speed change mode allowing
stepping speed change ratio control (hereinafter,
referred to as "stepping speed change control") like
manual type multistage transmission.
BACKGROUND OF THE INVENTION
Japanese Patent Laid-open No. Hei 9-
203460 discloses a transmission system including an
automatic transmission composed of a hydrostatic type
automatic transmission (hereinafter, sometimes referred
to as "HFT") and a sub-transmission connected to the
automatic transmission in series. The hydrostatic type
automatic transmission is configured such that a fixed
displacement swash plate type hydraulic pump is connected
to a variable displacement swash plate type hydraulic
motor via a hydraulic closed circuit. In this
transmission system, the automatic transmission includes
an automatic speed change mode allowing continuously
variable speed change and a stepping speed change mode
allowing multistage speed change, wherein stepping speed
change is started under the stepping speed change mode
which is switched from the automatic speed change mode by
a mode switch. This stepping speed change control can be
performed just as a manual type multistage transmission
by selecting a target speed change ratio from a plurality
of predetermined speed change ratios by means of a shift
switch.
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Japanese Patent Laid-open No. Hei 9-264416
discloses a transmission system in which a mode switch
and a shift switch are separately provided on a steering
handle. Further, there is known a transmission system
used for a handlebar type vehicle such as a buggy, in
which a shift switch is provided on the left side of the
handlebar, and a mode switch is provided on a handle
cover separated from the shift switch.
The above-described prior art transmissions of
the type in which the mode switch and the shift switch
are separately provided, however, has a problem. Since
switches specialized for mode selection and shift
operation must be provided, the number of parts becomes
large, and since the mode switch and the shift switch are
different from each other in terms of opportunity of
operation and operational manner, it is required to
prevent these switches from being erroneously used. The
transmission used for a handlebar type vehicle has
another problem. Since the mode switch is provided at a
location separated from the handlebar, a driver must
separate his or her hand from the handlebar for each mode
switching operation, with a result that the mode
switching operation becomes complicated. Accordingly, an
object of the present invention is to solve these
problems of the prior art transmissions.
SUMMARY OF THE INVENTION
To achieve the above object, according
to the present invention, there is provided a
transmission system including: an automatic transmission
including a plurality of speed change modes containing a
continuously variable speed change mode and a steeping
speed change mode; a sub-transmission connected to the
automatic transmission, the sub-transmission being
capable of switching one of a plurality of running ranges
containing a forward range, a neutral range, and a
reverse range to another; a mode switch for selectively
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switching either of the plurality of speed change modes
of the automatic transmission; and a shift switch for
switching one of speed change stages to another under the
stepping speed change mode, the transmission system being
characterized in that a function of the shift switch and
a function of the mode switch are collectively integrated
into a common switch, and the common switch is
selectively used as the shift switch or the mode switch.
In the above transmission system, the common
switch may be configured to be usually used as the shift
switch and used as the mode switch only when brake
operation is confirmed or only when the running range
becomes the neutral range; and further the forward
running side of the running ranges may be configured as
to include only one range.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention are
shown in the drawings, wherein:
FIG. 1 is a diagram showing a control system of
an entire hydrostatic continuously variable transmission.
FIG. 2 is a view showing a tilt angle control
mechanism.
FIG. 3 is a flowchart showing the control of
continuously variable speed change according to an
embodiment of the present invention.
FIG. 4 is a graph illustrating a method of
determining an RC (Riding Condition).
FIG. 5 is a speed change map.
FIG. 6 is a flowchart showing the control of
stepping speed change.
FIG. 7 is a diagram showing various modes.
FIG. 8 is a diagram showing the more detailed
control system of a control unit in the transmission
shown in FIG. 1.
FIG. 9 is a diagram showing a mode switching
order.
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FIG. 10 is a flowchart showing mode changing
control.
FIG. 11 is a view, similar to FIG. 1, showing
another embodiment.
FIG. 12 is a view, similar to FIG. 9, showing the
embodiment shown in FIG. 11.
FIG. 13 is a view, similar to FIG. 10, showing
the embodiment shown in FIG. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the present invention, since the
functions of the shift switch and the mode switch are
collectively integrated into the common switch and the
common switch can be selectively used as the shift switch
or the mode switch, it is not required to provide
switches specialized for mode selection and shift
operation, with a result that the number of parts can be
reduced, and since the shift switch and the mode switch
can be disposed at one location, the mounting and usage
of these switches become convenient.
According to a specific configuration in which
the common switch is usually used as the shift switch and
the common switch is changed into the mode switch only
when brake operation is confirmed, the shift switch can
be used as the mode switch under the condition that
manual control is not carried out, with a result that the
shift switch can be prevented from being erroneously used
as the mode switch even in a running range. According to
another specific configuration in which the common switch
is changed into the mode switch only when the running
range becomes the neutral range, the shift switch can be
also prevented from being erroneously used as the mode
switch.
According to a further specific configuration in
which the front running side of the running ranges
switched by the sub-transmission, which generally
includes two or more running ranges such as a low (L)
range and a drive (D) range, can be configured to include
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only one running range by setting the automatic
transmission such that the front running side is widened
to the low side. Accordingly, it is possible to
eliminate the need of switching one of the running ranges
on the forward side to another, that is, to eliminate the
laborious operation required for the conventional general
sub-transmission, in which the driver's hand must be
separated each time the L (low) range is switched to or
from the D (drive) range. Further, since the speed
change mode and the speed change stage under the stepping
speed change mode can be switched only by operating the
common switch, the speed change operation for running on
the forward side can be performed without separation of
the driver's hand from the handlebar.
Hereinafter, one embodiment of a transmission
system used for a vehicle provided with a handlebar, such
as a motorcycle or a four-wheeled buggy will be described
with reference to the drawings. FIG. 1 is a diagram
showing a control system of a control unit according to
this embodiment; FIG. 2 is a view showing a tilt angle
control mechanism portion of a movable swash plate of a
hydrostatic type automatic transmission according to this
embodiment; FIG. 3 is a flowchart showing the control of
continuously variable speed change; FIG. 4 is a graph
illustrating a method of determining an RC (Riding
Condition); FIG. 5 is a speed change map; FIG. 6 is a
flowchart showing the control of stepping speed change
control; FIG. 7 is a diagram showing various modes; FIG.
8 is a diagram showing the detailed control system of the
control unit; FIG. 9 is a diagram showing a mode
switching order; and FIG. 10 is a flowchart showing mode
changing control.
The control of a hydrostatic type automatic
transmission will be first schematically described with
reference to FIG. 1. A hydrostatic type automatic
transmission 1 is configured such that a fixed
displacement hydraulic pump 2 and a variable displacement
hydraulic motor 3 are integrally provided on a drive
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shaft 4 and are connected to each other via a hydraulic
closed circuit. The variable displacement hydraulic
motor 3 is speed-changeably rotated by a hydraulic
pressure generated by rotating a driven gear 8 of the
fixed displacement hydraulic pump 2 via a drive gear 7
provided on a crank shaft 6 of an engine 5. The speed-
changed rotation of the motor 3 is then outputted to a
drive shaft 4. At this time, the speed change ratio can
be freely varied by changing a tilt angle of a movable
swash plate (described later) built in the movable
displacement hydraulic motor 3 by using a tilt angle
control mechanism 10.
The tilt angle control mechanism 10 is configured
such that the output of a control motor 11 is transmitted
to a reduction gear 12, to change the tilt angle of the
movable swash plate built in the variable displacement
hydraulic motor 3 via a combination of a ball screw 13
and a slider 14. The speed-changed output of the
hydrostatic type automatic transmission 1 is transmitted
from an output gear 4a of the drive shaft 4 to a sub-
transmission 15 as a secondary reduction gear, and the
speed-changed output of the sub- transmission 15 is
transmitted from an output gear 17 on a speed-change
output shaft 16 to a final output gear 18a on a final
output shaft 18. The output of the final output shaft 18
is further transmitted from a bevel gear 18b provided at
the end of the final output shaft 18 to a bevel gear 19a
of an axle 19, to rotate drive wheels 19b.
The sub-transmission 15 switches a running range
by manually operating a sub-mission lever 20, thereby
driving a shifter 21. To be more specific, the sub
transmission 15 switches one of an L or D range ( forward
running side) , an R range (reverse running side) , and an
N position (neutral) to another. The L range is for low
speed running; the D range is for normal running; the N
position is for neutral; and the R range is for reverse
running. When the gear position is shifted to the R
range, the speed change ratio is fixed at a LOW ratio.
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The selection of one of running ranges L, D, and N by the
sub-transmission lever 20 is detected by a shift position
sensor 27 provided on the shifter 21, and a detection
signal from the sensor 27 is inputted in a control unit
22. The shift of the gear position to the R range is
detected by a reverse switch 20a, and a detection signal
from the reverse switch 20a is inputted to the control
unit 22.
Tn~hen the gear position is shifted to each of the
L and D ranges on the forward running side, one of speed
change modes previously set for various running modes to
be described later can be switchingly selected by
operating a mode map switch 29 provided on a handlebar.
The mode map switch 29 is equivalent to a mode switch of
the present invention. The running modes switchable by
the mode map switch 29 are basically classified into an
automatic speed change mode and a stepping speed change
mode. When the stepping speed change mode is selected,
the speed change ratio can be shifted up or shifted down
by manually operating a shift switch 28 provided on the
handlebar.
The shift switch 28 and the mode map switch 29 in
this embodiment are configured as a common switch to be
described later. The common switch is provided in the
vicinity of a left grip (not shown) of the handlebar and
can be operated with the driver's left hand with the grip
grasped by the left hand. A brake switch 50 is provided
in the vicinity of a right grip G. When the brake is
actuated by operating a brake lever L of the handlebar,
the braking operation is detected by the brake switch 50,
and a detection signal from the brake switch 50 is
inputted to the control unit 22.
FIG. 7 is a diagram illustrating various running
modes previously prepared. In the case of selecting the
L range by operating the sub-mission lever 20, an L range
auto-mode, which is a continuously variable speed change
mode specialized for the L range, is set by switching the
mode map switch 29 into the speed change mode D1 or D2;
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and an L range ESP mode, which is a manual mode
specialized for the L range and which allows manual speed
change at one of five speed stages on the forward running
side, is set by switching the mode map switch 29 into
ESP.
V~hen the D range is selected by operating the
sub-mission lever 20, a sport mode suitable for normal
running is set by switching the mode map switch 29 into
the speed change mode D1; a utility mode suitable for
traction or cruise running is set by switching the mode
map switch 29 into the speed change mode D2; and a manual
mode for normal running, which allows manual speed change
at one of five speed stages on the forward running side,
is set by switching the mode map switch 29 into ESP. In
addition, the mode map switch 29 is shown as a mechanical
type rotary switch in FIGS. 1 and 7 for convenience;
however, in actual, such a rotary switch is not present,
and as will be described later, the mode map switch 29 is
contained in the common button type switch shown as the
shift switch 28 in such a manner that the function of the
mode map switch 29 is collectively integrated with the
function of the shift switch.
In these continuously variable speed change mode
and stepping (manual) speed change mode, the speed change
is actually performed by tilt angle control. The tilt
angle control is performed by driving the control motor
11 of the tilt angle control mechanism 10 on the basis of
signals supplied from various sensors to the control unit
22. The control unit 22 outputs signals, which are to be
displayed on an indicator of an instrument panel M, to
the instrument panel M. Sensors will be described in
detail later.
The tilt angle control mechanism 10 will be
described with reference to FIG. 2. The control motor 11
of the tilt angle control mechanism 10 is supported by a
housing 30 of the fixed displacement hydraulic pump 2,
and an output from an output gear 31 is transmitted to a
ball screw drive gear 35 from a gear 34 via an input gear
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33 of a torque limiter 32. The ball screw drive gear 35
is rotated integrally with the ball screw 13. When the
ball screw 13 is normally or reversely rotated, the
slider 14 having a nut engaged with the ball screw 13 is
moved forward or backward in the axial direction. Both
ends of the ball screw 13 are supported by a housing 36
of the hydraulic motor 3.
One end of an arm 37 projecting outwardly from
the housing 36 of the variable displacement hydraulic
motor 3 is turnably mounted to the slider 14, and the
other end of the arm 37 is integrated with a swash plate
holder 38 supported in the housing 36. The swash plate
holder 38 is supported on a recessed curve surface
portion 39 formed on the inner surface of the housing 36
in such a manner as to be freely rolled thereon. When
the arm 37 is turned, the swash plate holder 38 is
turned, integrally with the arm 37, on the recessed curve
surface portion 39, whereby the angle of the swash plate
holder 38 is changed.
A movable swash plate 40 is rotatably supported
inside the swash plate holder 38 via bearings 41 and 42.
As the angle of the swash plate holder 38 is changed, a
tilt angle formed between a rotating plane of the movable
swash plate 40 and the axial line of the drive shaft 4 is
changed. Additionally, FIG. 2 shows a TOP state having a
speed change ratio of 1.0, in which the tilt angle is set
to 90°.
A plurality of hydraulic plungers 43 of the
variable displacement hydraulic motor 3 are disposed on a
drum-like rotator 44 in such a manner as to be arranged
in the circumferential direction. The hydraulic plungers
43 are pushed against the movable swash plate 40 by a
hydraulic pressure applied from the fixed displacement
hydraulic pump 2 side, to give a rotating force to the
rotator 44 according to the tilt angle of the movable
swash plate 40. An outer peripheral portion of the
rotator 44 is spline-connected (designated by reference
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numeral 45) to the drive shaft 4, so that the drive shaft
4 is rotated by rotation of the rotator 44.
The speed change control by the control unit 22
under the continuously variable speed change mode will be
described with reference to FIG. 3. First, an RC (Riding
Condition) is prepared from a throttle signal supplied
from a throttle sensor 23 (see FIG. 1). The RC is a
value increased/decreased according to a value of the
throttle signal. The basic relationship between the
throttle opening and the RC value is as follows:
increase in throttle opening ~ increase in RC
decrease in throttle opening ~ decrease in RC
This relationship is shown in FIG. 4, in which
the ordinate designates the throttle opening (o) and RC
(~) and the abscissa designates the time. In this
figure, character TH designates a throttle opening (o).
Referring again to FIG. 3, in addition to preparation of
the RC, a vehicle speed is calculated from a vehicle
speed signal supplied from a speed sensor 25.
Subsequently, on the basis of the RC and the
vehicle speed thus obtained, a target engine speed Ne is
determined by using a speed change map previously stored
in the control unit 22. One example of the speed change
map is shown in FIG. 5. In actual, several kinds of the
speed change maps specialized for the L range mode, sport
mode, utility mode, and the like are previously stored in
the control unit 22. A desired speed change map can be
selected from these speed change maps by the mode map
switch 29.
Referring again to FIG. 3, an actual engine speed
Ne is calculated on the basis of an engine speed Ne
signal supplied from a rotation sensor 24 (see FIG. 1),
and a rotational direction (normal or reverse direction)
of the control motor 11 and a DUTY value are determined
by comparing the actual engine speed Ne with the target
engine speed Ne. Concretely, the rotational direction of
the control motor 11 is determined by moving the movable
swash plate as follows:
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actual Ne target Ne ~ movement of movable swash plate on
TOP side actual Netarget Ne ~ movement of movable swash
plate on LOW side
The DUTY value is determined on the basis of the
following equation:
DUTY = Klxreal Ne target Ne (K1: coefficient)
Here, DUTY indicates a rate of a current applied
to the control motor 11, which is used for speed control
of the control unit 11. When DUTY = 1000, the rotational
speed of the control motor 11 is maximized, and when DUTY
- Oo, the control unit 11 is stopped.
Subsequently, the control motor 11 is controlled
according to a tilt angle of the movable swash plate
calculated on the basis of the rotational direction of
the control motor 11, DUTY, and a tilt angle signal
supplied from an angle sensor 26 (see FIG. 1). To be
more specific, the control motor 11 is driven on the
basis of the rotational direction of the control motor 11
and the DUTY value. On the other hand, the tilt angle of
the movable swash plate is measured, and if the detected
tilt angle is out of the TOP ratio side, the control
motor 11 is stopped.
According to this embodiment, stepping speed
change control under the stepping speed change mode can
be carried out. The stepping speed change control means
speed change control capable of manually switching the
speed change ratio just as the speed change control of a
manual type multistage transmission. Such stepping speed
change control is carried out by controlling the tilt
angle of the movable swash plate 40. The control of the
tilt angle of the movable swash plate 40 may be performed
by the control unit 22 in the same manner as that
described above except that the control content is not
continuously but stepwise changed.
The switching between the stepping speed change
mode and the automatic speed change mode is performed by
the mode map switch 29. When the stepping speed change
mode is selected, the stepping speed change operation can
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be performed by depressing the shift switch 28. The
shift switch 28 includes a shift-up button 28a and a
shift-down button 28b (see FIG. 1). The gear position is
shifted up or shifted down by one stage each time the
shift-up button or shift-down button is depressed.
FIG. 6 shows a control procedure of the control
unit 22 for carrying out the stepping speed change
control. First, a tilt angle is calculated on the basis
of a swash plate angle signal supplied from the angle
sensor 26, and a shift command indicating shift-up or
shift-down is determined on the basis of a shift signal
supplied from the shift switch 28. Additionally, the
shift-up command is generated when the shift-up button
28a of the shift switch 28 is depressed, and the shift-
down command is generated when the shift-down button 28b
of the shift switch 28 is depressed.
Subsequently, on the basis of the tilt angle and
the shift command thus determined, meter indication is
determined and also a target swash plate angle is
determined. The meter indication has contents of
determining the number of gear stages equivalent to the
number of shift stages of a manual transmission, and
determining a display signal to be displayed on the
indicator of the meter M and outputting the display
signal on the meter M to display the determined number of
gear stages on the indicator of the meter M.
When the shift command is inputted, the target
swash plate angle is determined with respect to the
present gear display signal under the following
condition:
shift-up command . shift-up by one stage
shift-down command . shift-down by one stage
Subsequently, the normal/reverse rotational
direction of the control motor 11 and the DUTY value are
determined by comparing the target swash plate angle thus
determined with an actual tilt angle, as follows:
(1) actual tilt angle target swash plate angle .
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movable swash plate 40 moved on LOW side
(2) actual tilt angle target swash plate angle .
movable swash plate 40 moved on TOP side
The DUTY value is determined on the basis of the
following equation:
DUTY = K2X real Ne target Ne (K2: coefficient)
Subsequently, on the basis of the rotational
direction of the control motor 11 and the DUTY value thus
determined, the control motor 11 is controlled to tilt
the movable swash plate 40 at a specific angle. In this
way, the hydrostatic type automatic transmission 1 can
carry out the stepping speed change equivalent to the
stepping speed change of a manual type multistage
transmission.
According to this embodiment, the shift switch 28
and the mode map switch 29 are configured as a common
switch. It is possible to use the common switch as the
shift switch 28 during running of the vehicle, and to use
the common switch as the mode map switch 29 by changing
the function thereof only under a specific condition. It
should be noted that the mode map switch 29 is one
specific example of the mode switch described in claims
of the present invention.
FIG. 8 is a diagram showing part of the control
system shown in FIG. 1 in more detail for illustrating a
configuration of switches and sensors for generating
signals inputted in the control unit 22 for speed change
control by the tilt angle control mechanism 10.
Referring to FIG. 8 in addition to FIG. 1, the
configuration will be described below. The above-
described gear position sensor 27, shift switch 28, and
brake switch 50 are connected to the input side of the
control unit 22.
Referring to FIG. 1, other input signals include
signals of a throttle opening detected by the throttle
sensor 23 provided on the intake side of the engine 5, of
an engine speed Ne detected by the rotation sensor 24
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provided in proximity to the crank shaft 6, of a vehicle
speed detected by the speed sensor 25 provided in
proximity to the final output gear 19, of a swash plate
angle detected by the angle sensor 26 provided in the
variable displacement hydraulic motor 3, and of a shift
position detected by the shift sensor 27 provided
integrally with the shift drum 21a of the shifter 21. In
addition, the throttle sensor 23 and the angle sensor 26
are each configured as a potentiometer.
The configuration of the motor power supply side
will be described below. A battery 51 is connected to
the control unit 22 via a fuse 52. A main switch 53 is
connected in parallel to the battery 51 via a fuse 54,
and is also connected to the control unit 22 via a fuse
52. In the figure, reference numeral 55 designates a
kill switch. The control motor 11 is connected to the
output side of the control unit 22, and the rotation of
the control motor 11 is controlled by the control unit
22.
The shift switch 28 is a switch capable of
selecting one of the shift-up switch 28a and the shift-
down switch 28b in a toggle manner. A shift-up command
or a shift-down command is outputted to the control unit
22 each time the shift-up switch 28a or the shift-down
switch 28b is depressed. As described above, it is
possible to use the shift switch 28 as the mode map
switch 29 by changing the function of the shift switch
28.
FIG. 9 shows speed change modes switchable by the
mode map switch 29 after the shift switch 28 is changed
into the mode map switch 29 by conversion of the
functions thereof, and a mode switching order of the
speed change modes. By depressing the shift-up switch
28a, the mode is changed in the circulating order of
ESP.D2.D1, and by depressing the shift-down switch 28b,
the mode is changed in the order D1.D2.ESP, which is
reversed to that described above.
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FIG. 10 is a flowchart showing the control of
switching the shift switch 28 and the mode map switch 29
from each other. After start of the program, on the
basis of a signal supplied from the speed sensor 25, it
is determined in step S.1 whether or not the vehicle is
stopped. If N0, which indicates that the shift switch 28
cannot be changed into the mode map switch 29, the
process goes on to step S7 in which the running mode is
established, and then the process is returned to the
start of the program. If YES in step S, on the basis of
a signal from the shift sensor 27, it is determined by
the shift position sensor 27 in step S2 whether or not
the gear position is located at the neutral (N). If YES,
the process is jumped to step S5, whereas if NO, it is
determined in step S3 whether or not the gear position is
turned into the running range ( D or L range ) . I f NO in
step S3, the process goes on to step S7, whereas if YES
in step S3, it is determined in step S4 whether or not
the brake switch is turned on, that is, brake operation
is performed.
If NO in step S4, which indicates that there is a
possibility that the vehicle starts running, that is, the
mode changing condition is not satisfied, the process
goes on to step S7. If YES in step S4, which indicates
that the mode changing condition is satisfied, it is
determined in step S5 whether or not either the shift-up
switch 28a or the shift-down switch 28b of the shift
switch 28 is depressed.
If NO in step S5, which indicates that the driver
do not want to change the mode, the process goes on to
step S7. If YES in step S5, which indicates that the
driver wants to change the mode, the process goes on to
step S6 in which the function of the shift switch 28 is
changed into that of the mode map switch 29 for allowing
selection of one of the running modes shown in FIG. 7,
and then the process is returned to the start of the
program.
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In this way, according to this embodiment, since
the shift switch 28 serves as the mode map switch 29, the
common switch is can be configured as a multi-function
switch, and therefore, since it is not required to
provide a plurality of switches specialized for mode
selection and shift operation, it is possible to reduce
the number of parts and to easily mount the common switch
to the vehicular body. In particular, in the case of
applying the present invention to a buggy, since the
shift switch 28 and the mode map switch 29 configured as
a common switch can be disposed at one location of the
handlebar, it is possible for a driver to operate the
common switch with one hand while gripping the handlebar
with the other hand.
If the common switch is provided on the left side
of the handlebar, a brake lever L (see FIG. 1) may be
provided on the right side of the handlebar. In this
case, the driver can operate the mode map switch 29
changed from the shift switch 28 with the left hand while
operating the brake lever with right hand. This makes it
possible to enhance the operability.
According to this embodiment, since the shift
switch 28 can be changed into the mode map switch 29 only
when the vehicle is stopped and the brake operation is
established, for example, by turning on the brake switch
50, the change of the shift switch 28 into the mode map
switch 29 is performed only in a condition with a very
small possibility that the shift switch 28 is used. As a
result, it is possible to certainly prevent the shift
switch 28 from being erroneously used as the mode map
switch 29.
Further, according to this embodiment, since the
shift switch 28 can be changed into the mode map switch
29 only when the vehicle is stopped and the gear position
is turned into the neutral (N), it is also possible to
certainly prevent the shift switch 28 from being
erroneously used as the mode map switch 29 during running
of the vehicle.
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FIGS. 11 to 13 show another embodiment. FIG. 11,
12, and 13 are equivalent to FIG. 1, FIG. 9, and FIG. 10,
respectively. In this embodiment, parts corresponding to
those in the previous embodiment are designated by the
same characters and the repeated description thereof is
omitted. This embodiment is characterized in that, of
the running ranges switchable by a sub-transmission 15,
the running range on the forward running side includes
only the drive (D) range, that is, does not include the
low (L) range.
As shown in FIG. 11, a sub-transmission lever 20
of the sub-transmission 15 switches one of running
ranges, a forward side D, a reverse side R, and a neutral
N to another. The running range on the forward side
includes only the D range for normal running; however,
the D range is widened to the low side so as to include
the L (low) range in the previous embodiment.
FIG. 12 shows speed change modes switchable by
the mode map switch 29 after the shift switch 28 is
changed into the mode map switch 29 by conversion of the
functions thereof, and a mode switching order of the
speed change modes. By depressing the shift-up switch
28a, the mode is changed in the circulating order of D1
D2 ESP L.ESP(L) D1, and by depressing the shift-down
switch 28b, the mode is changed in the order reversed to
that described above.
Of these modes, D1, D2, and ESP are the same as
those described with reference to FIG. 9, which are modes
allocated to the D range in the previous embodiment. The
L and ESP(L) are modes allocated to the L range in the
previous embodiment, wherein L is an auto (continuously
variable speed change) mode and ESP(L) is a manual mode
(see L range in FIG. 7).
FIG. 13 is a flowchart showing the control of
switching the shift switch 28 and the mode map switch 29
from each other. After start of the program, on the
basis of a signal supplied from the speed sensor 25, it
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is determined in step S11 whether or not the vehicle is
stopped. Then, it is determined in step S12 by the shift
sensor 27 whether or not the gear position is located at
the D range; it is determined in step S13 whether or not
the braking is performed by turn ON/OFF of the brake
switch 50; and it is determined in step S14 whether or
not the shift switch 28 is depressed. If YES at all of
steps 512, S13 and 514, the speed change mode is
switched. If NO at either of steps 512, S13 and 514,
which indicates that the shift switch 28 cannot be
changed into the mode map switch 29, the process goes on
to step S16 in which the speed change mode is
established, and then the process is returned to the
start of the program.
The function of this embodiment will be described
below. In this embodiment, since the running range on
the forward running side switchable by the sub-
transmission 15 includes only the D range by widening the
running range on the forward running side to the low
side, the speed change operation on the forward running
side can be performed, at the time of forward running,
only by switching the mode map switch 29 without manual
switching of the running range. On the other hand, in
the conventional general sub-transmission in which the
running range on the forward running side is not widened,
the running range must be manually switched to locate the
shift position at the D or L mode by the sub-transmission
lever.
According to this embodiment, therefore, it is
possible to eliminate the laborious operation required
for the conventional general sub-transmission, in which
the driver's hand must be separated each time the L (low)
range is switched to or from the D (drive) range. Also
since the speed change mode and the speed change stage
under the stepping speed change mode can be switched only
by operating the shift switch 28, the speed change
operation for running on the forward side can be
performed without separation of the driver's hand from
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the handlebar. As a result, it is possible to eliminate
the laborious operation and hence to realize comfort
operation.
The present invention is not limited to the
above-described embodiment, and it is to be understood
that various changes may be made without departing from
the spirit or scope of the present invention. Further,
the present invention can be applied not only to the
hydrostatic type automatic transmission system but also
to a CTV system, electronic control belt conveyor, or the
like.
Although various preferred embodiments of the
present invention have been described herein in detail,
it will be appreciated by those skilled in the art, that
variations may be made thereto without departing from the
spirit of the invention or the scope of the appended
claims.
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