Information
-
Patent Grant
-
6705028
-
Patent Number
6,705,028
-
Date Filed
Tuesday, September 10, 200222 years ago
-
Date Issued
Tuesday, March 16, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 037 241
- 037 246
- 037 247
- 037 249
- 037 254
- 037 257
- 037 261
- 037 244
- 037 348
- 037 382
- 192 358
- 192 564
- 192 34
- 701 50
- 172 2
-
International Classifications
-
Abstract
A self-propelled snowplow vehicle includes a vehicle frame equipped with an auger at a front end portion thereof and pivotally connected to a propelling frame equipped with driving wheels, and a frame lift mechanism for lifting the front end portion of the vehicle frame up and down relative to the propelling frame. The frame lift mechanism comprises an electro-hydraulic cylinder actuator having a piston rod and an electric motor rotatably driven to produce a fluid pressure for reciprocating the piston rod in response to operation of a manual operating switch. The snowplow vehicle also includes a control unit arranged to forcibly stop the electric motor when a predetermined time has elapsed after the operation switch is activated, the predetermined time being equal to an operating time of the cylinder actuator which is required to extend or contract the piston rod over a maximum stroke defined between a fully extended position and a fully contracted position of the piston rod.
Description
FIELD OF THE INVENTION
The present invention relates to a self-propelled snowplow vehicle having a driving wheel for driving the snowplow vehicle and an auger for removing snow.
DESCRIPTION OF THE RELATED ART
In a snowplow vehicle equipped with a snow-removing anger, a system is employed to ensure that the vertical level or height of the auger can be changed in view of snow-removing conditions. When the snowplow vehicle moves from one place to another, the auger is preferably kept in a raised position to facilitate smooth movement of the snowplow vehicle. On the other hand, when a snow-removing operation is to be achieved, the auger is preferably moved to a lower position to achieve the snow-removing operation with improved efficiency. During the snow-removing operation, the auger is frequently raised and lowered in harmony with angulations on the ground surface. Frequent rising and lowering operation of the auger, when achieved manually, is laborious. To lighten the load on the human operator, an improved self-propelled snowplow vehicle has been proposed, which is equipped with a power-operated vertically swingable auger, as disclosed in Japanese Patent Laid-open Publication No. HEI 4-194109.
The disclosed snowplow vehicle includes a propelling frame equipped with left and right crawler belts, a vehicle frame equipped with an auger and pivotally connected to the propelling frame, and a lift control device operable to lift a front end portion of the vehicle frame up and down relative to the propelling frame. The lift control device is comprised of a cylinder actuator operable, under the control of a control unit, to extend or contract its piston rod to thereby lift the vehicle frame front end portion and the auger in an upward or a downward direction in response to pivotal movement of a manual operating lever provided on an operating part of the snowplow vehicle.
The cylinder actuator constituting the lift control device needs a power source for operation thereof. In the case where the cylinder actuator is an oil hydraulic cylinder actuator, a separate hydraulic power unit must be provided. Accordingly, the overall size of the lift control device is relatively large. Thus, the use of the oil hydraulic cylinder actuator is quite disadvantageous when the snowplow vehicle is relatively small in size.
In order to achieve downsizing of the lift control device, use of an electro-hydraulic cylinder actuator may be considered. The electro-hydraulic cylinder actuator has an electric motor drivable to produce a hydraulic pressure used for reciprocating a piston rod of the cylinder actuator. The electric motor and a hydraulic power unit such as a pump are assembled with a cylinder of the cylinder actuator, so that the electro-hydraulic cylinder actuator is relatively small in size. The electric motor is controlled to extend or contract the piston rod of the cylinder actuator to thereby raise or lower the auger in response to on-off operation of an operation switch.
Since the height of the auger is changed in view of snow-removing conditions, it may occur that the operation switch is kept in the activated state even after the piston rod arrives at its fully extended or fully contracted position. On this occasion, the electric motor is subjected to a heavy load for a long time. Additionally, during snow-removing operation, since the height of the auger is frequently changed in harmony with angulations of the ground surface, the electro-hydraulic cylinder actuator is forced to operate repeatedly with high frequencies. Under such condition, the duty cycle of the electric motor is very high and generation of heat from the electric motor is promoted.
To deal with this problem, use of a continuously operable electric motor may be considered. The continuously operable electric motor is, however, expensive and hence increases the cost of the snowplow vehicle. As an alternative measure, use of a thermo-breaker may be considered for the purpose of protecting the motor from overheating. The thermo-breaker is generally built in the electric motor and operates to cut off or open a power supply circuit to the electric motor when the electric motor heats up above a given temperature.
The thermo-breaker is designed to continue the “open” state of the power supply circuit until the electric motor cools to a satisfactory operating temperature. Accordingly, a downtime occurs each time the thermo-breaker operates. In case where the operating temperature of the thermo-breaker is set to a relatively low value, the power supply circuit to the electric motor may be frequently cut off by the thermo-breaker. Alternatively, when the operating temperature of the thermo-breaker is set to a relatively high value, the power supply circuit to the electric motor may be cut off infrequently. In the latter case, however, the thermo-breaker requires a relatively long time to recover its original inoperating state. To enable smooth snow-removing operation, the frequency of operation of the thermo-breaker should preferably be reduced
To this end, an arrangement may be considered, in which a detection switch is associated with the electro-hydraulic cylinder actuator such that when arrival of the piston rod of the cylinder actuator at its fully extended or fully contracted position is detected by the detection switch, the detection switch generates a signal to stop operation of the electric motor. This arrangement may reduce the occurrence of overloaded condition of the electric motor. However, use of the detection switch necessarily increases the number of parts of the cylinder actuator and requires an electric wiring system, leading to an increased cost of the snowplow vehicle.
FIGS. 16A
to
16
C are diagrammatical views illustrative of the operation of a conventional self-propelled snowplow vehicle
500
. In
FIG. 16A
, the snowplow vehicle
500
is shown with a snow-removing auger
503
disposed in a lowermost horizontal position. The snowplow vehicle
500
is moving forward by the action of crawlers
501
(one being shown) while removing snow by means of the auger
503
and a blower
504
rotatably driven by an engine
502
. The auger
503
collects snow and the blower
504
blows the collected snow away from the snowplow vehicle
500
through a shooter
505
. In this instance, a travel control lever
511
provided on a control board
510
is disposed in an “F” (forward) position, and an auger lift control lever
512
also provided on the control board
510
is disposed in a “DN” (down) position.
Due to a large amount of snow to be removed or in order to change the advancing direction of the snowplow vehicle
500
, the snowplow vehicle
500
is occasionally moved backward. In this instance, as shown in
FIG. 16B
, the travel control lever
511
on the control board
510
is shifted from the “F” (forward) position to an “N” (neutral) position as indicated by the arrow {circle around (
1
)} whereupon the snowplow vehicle
500
stops moving in the forward direction. Then, the auger lift control lever
512
is shifted from the “DN” (down) position to an “UP” (up) position as indicated by the arrow {circle around (
2
)} whereupon lift cylinder actuators
506
(one being shown) operate to extend their piston rods to thereby lift a front end portion of a vehicle frame
508
upward relative to a propelling frame
507
on which the crawlers
501
(
FIG. 16A
) are mounted. The auger
503
is thus raised to an uppermost elevated inclined position.
Then as shown in
FIG. 16C
, the travel control lever
511
on the control board
510
is shifted from the “N” (neutral) position to an “R” (reverse) position as indicated by the arrow {circle around (
3
)} whereupon the snowplow vehicle
500
moves backward. As described above, in order to reverse the snowplow vehicle while moving in the forward direction, the conventional snowplow vehicle requires three consecutive steps of manual operation as indicated by the arrows {circle around (
1
)}-{circle around (
3
)}. Conversely, when the snowplow vehicle while moving backward is to be moved in the forward direction, the snowplow vehicle is first stopped from moving backward. Then, the auger is lowered from the uppermost inclined position to the lowermost horizontal position. Finally, the snowplow vehicle is moved in the forward direction. Thus, three consecutive steps of manual operation are also required. Due to complicated manual operations of the two levers
511
,
512
to be done in a correct order, the maneuverability of the conventional snowplow vehicle is relatively low.
To deal with this problem, an improved snowplow vehicle has been proposed, wherein a snow-removing unit such as an auger is automatically raised when a reversing operation of the snowplow vehicle is selected, as disclosed in Japanese Utility Model Laid-open Publication No. SHO 64-28416. As shown in
FIG. 17A
, when a travel control lever
611
on a control board
610
is shifted to an “F” (forward) position, the snowplow vehicle
600
moves forward as indicated by the arrow while, at the same time, an auger
603
rotates to thereby achieve snow-removing operation. When the travel control lever
611
on the control board
610
is shifted to an “R” (reverse) position, as shown in
FIG. 17B
, the auger
603
is moved upward from the lowermost horizontal position of
FIG. 17A through a
neutral position (not shown) to an uppermost inclined position of FIG.
17
B. Upon arrival of the auger
603
at the uppermost inclined position, rotation of the auger
603
is stopped by disengaging an auger clutch (not shown) disposed between the auger
603
and an engine (not designated). At the same time, the snowplow vehicle
600
is driven to move in the reverse direction as indicated by the arrow shown in FIG.
17
B.
Since the auger
603
is lifted up to the uppermost inclined position each time the reverse position is selected by the travel control lever
611
, this means that when the snowplow vehicle
600
is then to be moved forward to achieve a snow-removing operation, the auger
603
needs to be lifted down from the uppermost inclined position to the lowermost horizontal position. Due to a long downward stroke of the auger
603
, an interruption occurs in the snow-removing operation each time the “F” (forward) position is selected immediately after the reversing mode of the snowplow vehicle. In other words, lifting of the auger
603
to the uppermost inclined position in preparation for the backward movement of the snowplow vehicle will lower the efficiency of the snow-removing operation. Due to this difficulty, the snowplow vehicle
500
shown in
FIGS. 16A-16C
is normally used notwithstanding the fact that the snowplow vehicle
500
is not satisfactory in terms of the maneuverability and lightening of load on the operator.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a self-propelled snowplow vehicle, which can be manufactured at a relatively low cost, is able to lighten the load on an electric motor of a electro-hydraulic cylinder actuator used to raise or lower a snow-removing member such as an auger, and is capable of achieving a snow-removing operation smoothly and efficiently.
According to the present invention, there is provided a self-propelled snowplow vehicle comprising: a propelling frame equipped with driving wheels for driving the snowplow vehicle; a vehicle frame equipped with an auger at a front end portion thereof for removing snow, the vehicle frame being pivotally connected to the propelling frame; a frame lift mechanism for lifting the front end portion of the vehicle frame up and down relative to the propelling frame, the frame lift mechanism including an electro-hydraulic cylinder actuator having a piston rod and an electric motor rotatably driven to produce a fluid pressure for reciprocating the piston rod between a fully contracted position and a fully extended position; an operation switch adapted to be manually activated to drive the electric motor in either direction; and a control unit for controlling operation of the electric motor thereby to control operation of the frame lift mechanism.
In one preferred form of the present invention, the control unit is arranged to forcibly stop the electric motor when a predetermined time has elapsed after the operation switch is activated, the predetermined time being equal to an operating time of the cylinder actuator which is required to extend or contract the piston rod over a maximum stroke defined between the fully extended position and fully contracted position.
By thus forcibly stopping the electric motor, it is possible to cut down the operating time of the electric motor. Since the electric motor is released from a heavily loaded condition soon after the arrival of the piston rod at its fully extended or contracted position, the load on the frame lift mechanism including the electric motor is lessened and the durability of the frame lift mechanism is increased.
Additionally, since the electric motor is stopped when the piston rod moves over the maximum stroke, generation of heat from the electric motor can be suppressed. The thermo-breaker built in the electric motor does not operate, so that the operator is allowed to continue snow-removing operation of the snowplow vehicle without considering a downtime of the snowplow vehicle which may occur when the thermo-breaker operates. The snow-removing operation can, therefore, be achieved smoothly and efficiently. Furthermore, the electro-hydraulic cylinder actuator (frame lift mechanism) can operate smoothly and reliably without requiring detection switches provided for detecting the piston rod arrived at the fully extended position and the fully contracted position. The snowplow vehicle is, therefore, formed by a reduced number of parts used and has a relatively simple electric wiring system. This achieves cost cutting of the snowplow vehicle.
It is preferable that the control unit continues to stop the electric motor when the operation switch is still in the activated state even after the lapse of the predetermined time.
When the operation switch is still in the activated state even after the electric motor is forcibly stopped upon the lapse of the preset reference time (which is equal to an operating time required for the electro-hydraulic cylinder actuator to move the piston rod over the maximum stroke), the control unit continues to stop the electric motor. Thus, a heavily loaded condition of the electric motor does not recur with the result that the total load exerted on the frame lift mechanism including the electric motor is reduced and the durability of the frame lift mechanism is increased. Additionally, since the thermo-breaker is kept in the off or inactivated state, a downtime does not occur. Thus, the snow-removing operation can be continued smoothly and efficiently.
In another preferred form of the present invention, the control unit is arranged to add up running times of the electric motor during which the electric motor is rotating and forcibly stop the electric motor when a total sum of the running times reaches a predetermined reference value. The predetermined reference value corresponds to a time which is required for the electric motor to heat up above a predetermined temperature. By forcibly stopping the electric motor, it is possible to protect the electric motor from overheating and eventually improve the durability of the electric motor. Additionally, the electric motor is stopped rapidly without operating the thermo-breaker built in the electric motor The control of the electric motor depends on time and does not rely on the thermo-breaker which requires a relatively long time for recover its original inoperating state. It is, therefore, possible to resume rotation of the electric motor in a relatively short period of time. Since snow-removing operation of the snowplow vehicle can be continued without considering a downtime which may occur when the thermo-breaker operates, the efficiency of the snow-removing operation is very high.
It is preferable that the total sum (Tm) of the running times is obtained by the expression
Tm=Tr−Ts
where Tr represents an accumulated total of the running times during which the electric motor is rotating, and Ts represents an accumulated total of the rest times during which the electric motor is at a standstill.
It may be considered that the cumulative running time Tr is a total sum of the running times of the motor during which the electric motor heats up while it is rotating, and the cumulative rest time Ts is a total sum of the rest times of the motor during which the electric motor cools down while it is at a standstill. By using the integrated value or total sum Tm of rotating times which is represented by the expression Tm=Tr−Ts, control of the electric motor is achieved in close match with actual heat-developing and -releasing conditions of the electric motor. Since the cumulative rest time (heat-releasing time) Ts of the electric motor is subtracted from the cumulative running time (heat-developing time) Tr, it is possible to elongate the time during which the integrated value or total sum Tm of running times reaches the preset reference value. This means that the time period during which the motor continues to rotate before it is forcibly stopped can be extended. The snow-removing operation of the snowplow vehicle can be achieved with improved efficiency.
It is further preferable that the control unit continues to stop the electric motor until a preset fixed time has passed after forcible stop of the electric motor. Since the heat developed in the electric motor is further released, the electric motor is protected from overheating with higher safeness and hence has a higher degree of durability.
Preferably, the running times of the electric motor have a fixed value and are added up at the lapse of a unit time, and the rest times of the electric motor have a fixed value and are added up at the lapse of the unit time, and wherein the fixed value of the running times is larger than the fixed value of the rest times.
In still another preferred form of the present invention, the snowplow vehicle has three modes of operation including a manual-up mode in which the auger is raised manually, a manual-down mode in which the auger is lowered manually, and an auto-up mode in which the auger is automatically raised, wherein the control unit is arranged such that when the manual-down mode is selected, the control unit determines and stores an amount of contraction of the piston rod achieved in the selected manual-down mode, and when the manual-down mode is followed by the auto-up mode and information representing reversing of the direction of rotation of the driving wheels is received, the control unit performs an auto-up control of the piston rod in which the piston rod is extended by an amount equal to the amount of contraction of the piston rod determined with respect to the preceding manual-down mode.
The travel condition of the snowplow vehicle, which may occur immediately before the manual-down mode is selected, is considered to be a road traveling condition in which the snowplow vehicle travels on a road surface with the auger held in an uppermost position, or a reversing condition in which the snowplow vehicle travels backwards on a snow-covered road surface with the auger held in an elevated position intermediate between the uppermost inclined position and a lowermost horizontal position. The auger, as it is in the elevated intermediate position, does not interfere with snow while the snowplow vehicle is moving backward. From this, it is preferable that when the auto-up mode is selected, the auger is raised to the elevated intermediate position. The auger is thus automatically returned to the previous position, so that there is no possibility of interference occurring between the auger and snow when the snowplow vehicle is moving backward. Furthermore, at the time of forward movement of the snowplow vehicle, the auger is lifted down from the elevated intermediate position to the lowermost horizontal position. Thus, the time required for lowering the auger is reduced to one-half of the conventional snowplow vehicle discussed above with reference to
FIGS. 17A and 17B
, so that the efficiency of the snow-removing operation is increased correspondingly. In addition, since the auger is automatically lifted to the elevated intermediate position, the operator is not subjected to undue load or pressure.
It is preferable that the piston rod of the electro-hydraulic cylinder actuator is extended and contracted at the same speed, and the amount of contraction of the piston rod is determined depending on time. This arrangement obviates the need for a stroke sensor provided for measuring the amount of extension or contraction of the piston rod, which sensor is expensive, is susceptible to malfunction due to adhesion of snow or dirt, and requires wire harnesses.
Preferably, the self-propelled snowplow vehicle further includes an auger clutch disposed between a power source and the auger for transmitting rotational power from the power source to the auger, wherein when the auger clutch is in an disengaged state, the control unit disables the auto-up control of the piston rod of the cylinder actuator.
The above and other objects, features and advantages of the present invention will become manifest to those versed in the art upon making reference to the following description and accompanying sheets of drawings in which certain preferred structural embodiments incorporating the principle of the invention are shown by way of illustrative examples.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side view of a walk behind self-propelled crawler snowplow vehicle according to an embodiment of the present invention;
FIG. 2
is a diagrammatical plan view of the snowplow vehicle, showing a propelling power transmission line extending from electric motors to crawler belts and a snow-removing power transmission line extending from an engine to a snowplow mechanism;
FIG. 3
is a view in the direction of the arrow
3
shown in
FIG. 1
;
FIG. 4
is an exploded perspective view of a frame lift mechanism;
FIGS. 5A and 5B
are diagrammatical side views illustrative of the operation of the frame lift mechanism;
FIG. 6
is a circuit diagram including a control unit and related parts thereof;
FIG. 7
is a flowchart showing a control procedure achieved by a control unit of the snowplow vehicle;
FIG. 8
is a time chart explanatory of the operation of the control unit;
FIG. 9
is a flowchart showing a modified control procedure achieved by the control unit;
FIG. 10
is a circuit diagram showing the control unit and related parts thereof according to a modification of the present invention;
FIG. 11
is a diagrammatic plan view of a walk behind self-propelled crawler snowplow according to another embodiment of the present invention;
FIGS. 12A and 12B
are diagrammatical views illustrative of the operation of an auger clutch equipped in the snowplow vehicle shown in
FIG. 11
;
FIG. 13
is an enlarged plan view of a control board;
FIG. 14
is a flowchart showing a control procedure achieved by a control unit of the snowplow vehicle shown in
FIG. 11
;
FIG. 15
is a flowchart similar to
FIG. 14
, but showing a modified control procedure of the control unit;
FIGS. 16A
to
16
C are diagrammatical views illustrative of the operation of a conventional snowplow vehicle; and
FIGS. 17A and 17B
are diagrammatical views illustrative of the operation of another conventional snowplow vehicle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description is merely exemplary in nature and is in no way intended to limit the invention or its application or use.
Referring to the drawings and
FIG. 1
in particular, there is shown a walk behind self-propelled crawler snowplow vehicle
10
according to an embodiment of the present invention. The snowplow vehicle
10
generally comprises a propelling frame
12
carrying thereon left and right crawler belts (only the left crawler belt
11
L being shown), a vehicle frame
15
carrying thereon a snowplow mechanism
13
and an engine (prime motor)
14
for driving the snowplow mechanism
13
, a frame lift mechanism
16
operable to lift a front end portion of the vehicle frame
15
up and down relative to the propelling frame
12
, and a pair of left and right operation handlebars
17
L and
17
R extending from a rear portion of the propelling frame
12
obliquely upward in a rearward direction of the snowplow vehicle
10
. The operation handlebars
17
L,
17
R each have a grip
18
L,
18
R at the distal end (free end) thereof The propelling frame
12
and the vehicle frame
15
jointly form a vehicle body
19
. The propelling frame
12
also carries thereon left and right drive wheels
23
L,
23
R and left and right driven wheels
24
L,
24
R.
The operation handlebars
17
L,
17
R are adapted to be gripped by a human operator (not shown) walking behind the snowplow vehicle
10
in order to maneuver the snowplow vehicle
10
. In the illustrated embodiment, a control board
41
, a control unit
28
and batteries
28
are arranged in a vertical space defined between the left and right handlebars
17
L,
17
R and they are mounted to the handlebars
17
L,
17
R in the order named when viewed from the top to the bottom of FIG.
1
.
The engine
14
serves as a power source for the snowplow mechanism
13
and generates motive power which is transmitted via a snowplow power transmission mechanism
34
to the snowplow mechanism
13
. The snowplow power transmission mechanism
34
is arranged such that power from an output shaft (crankshaft)
35
of the engine
14
can be transmitted via a driving pulley
36
and a power transmission belt
37
to the snowplow mechanism
13
. To this end, an electromagnetic clutch
45
is mounted on the output shaft
35
of the engine
14
. The driving pulley
36
is freely rotatably mounted on the output shaft
35
of the engine
14
and is connected in driven relation to the output shaft
35
when the electromagnetic clutch
45
is actuated or placed in the engaged state.
The snowplow mechanism
13
has an auger
31
, a blower
32
and a discharge duct or shooter
33
that are mounted to a front portion of the vehicle frame
15
. The auger
31
and the blower
32
are rotatably mounted on a rotating shaft
39
. The rotating shaft
39
has a driven pulley
38
connected in driven relation to the driving pulley
36
by means of the power transmission belt
37
.
In operation, the power from the engine output shaft
35
is transmitted via the electromagnetic clutch
45
to the driving pulley
36
, and rotation of the driving pulley
36
is transmitted via the power transmission belt
37
to the driven pulley
38
. The driven pulley
38
is thus rotated. Rotation of the driven pulley
38
causes the rotating shaft
39
to rotate the auger
31
and the blower
32
concurrently. The auger
31
cuts snow away from a road surface, for example, and feeds the snow into the blower
32
. The blower
32
blows out the snow through the discharge duct or shooter
33
to a distant place.
In
FIG. 1
, reference numeral
26
a
denotes an auger case, numeral
26
b
denotes a blower case, numeral
26
c
denotes a scraper formed integrally with a lower edge of the auger case
26
a,
numeral
26
d
denotes a charging generator for charging the batteries
29
, numeral
26
e
denotes a lamp, numeral
26
f
denotes a cover for protecting the generator
26
d
and the electromagnetic clutch
50
, and numeral
26
g
denotes a stabilizer for urging each crawler belt
11
L,
11
R downward against the ground surface.
As diagrammatically shown in
FIG. 2
, the left and right crawler belts
11
L,
11
R are driven by left and right electric motors
21
L,
21
R, respectively. The crawler belts
11
L,
11
R are each entrained around the driving wheel
23
L,
23
R and the driven wheel
24
L,
24
R provided in pair. The driving wheel
23
L,
23
R is disposed on a rear side of the crawler belt
11
L,
11
R, and the driven wheel
24
L,
24
R is disposed on a front side of the crawler belt
11
L,
11
R.
Power from each electric motor
21
L,
21
R is transmitted through a propelling power transmission mechanism
22
L,
22
R to the corresponding driving wheel
23
L,
23
R to thereby drive the associated crawler belt
11
L,
11
R. The propelling power transmission mechanism
21
L,
22
R comprises a speed reducer
22
L,
22
R assembled integrally with the electric motor
21
L,
21
R. The speed reducer
22
L,
22
R has an output shaft that forms a rear axle on which each driving wheel
23
L,
23
R is fixed. Thus, the left and right crawler belts
11
L,
11
R are separately drivable with power from the corresponding electric motors
21
L,
21
R. Reference numeral
25
denotes a front axle on which the left and right driven wheels
24
L,
24
R are rotatably mounted.
In order to drive the charging generator
26
d
, a generator driving pulley
27
a
is mounted to the engine output shaft (crankshaft)
35
, and a generator driven pulley
27
b
is mounted to a shaft of the charging generator
26
d
. The driving and driven pulleys
27
a
,
27
b
are connected by a V-belt
27
c
, so that rotation of the engine output shaft
35
is transmitted to the charging generator
26
d.
FIG. 3
shows the general arrangement of an operating part
40
of the snowplow vehicle. The operating part
40
generally comprises the control board
41
disposed between the left and right handlebars
17
L,
17
R, a travel-ready lever
43
and a left turn control lever
44
L that are mounted to the left handlebar
17
L in the proximity of the grip
18
L, and a right turn control lever
44
R mounted to the right handlebar
17
R in the proximity of the grip
18
R. The travel-ready lever
43
is operated to place the snowplow vehicle
10
in a ready-to-travel condition.
The control board
41
is composed of a box-shaped body
45
extending between the left and right handlebars
17
L,
17
R, and a control panel
46
covering an upper opening of the box-shaped control board body
45
. The body
45
is provided with an auger switch (clutch switch)
45
A for switching on-off operation of the electromagnetic clutch
50
(FIG.
1
), a main switch (key switch)
45
B, a choke knob
45
C that may be used when the engine
14
(
FIG. 1
) is started, a light button
45
D for turning on and off the lamp
26
e
(FIG.
1
), and a failure lamp
45
D designed to be turned on when a failure occurs.
The control panel
46
is provided with a lift control lever
46
A for controlling operation of the frame lift mechanism
16
(FIG.
1
), a shooter control lever
46
B for changing the direction of the shooter
33
(FIG.
1
), a throttle lever
46
C for controlling speed (revolutions per minute) of the engine
14
, and a forward/reverse speed control lever
76
for controlling the direction and speed of the electric motors
21
L,
21
R (FIG.
1
). The control panel
46
has a generally flat body portion
47
a
forming a major part of the control panel
46
, a cover portion
47
b
of an inverted U-shaped cross section for covering the travel-ready lever
43
, and a guide groove
48
formed in the body portion
47
a
for guiding movement of the forward/reverse speed control lever
76
.
The lift control lever
46
A has an auto-return mechanism so that when the lift control lever
46
A is released from the human operator, it automatically returns to the original neutral position shown in FIG.
3
. When the lift control lever
46
A is pulled or tilted rearward of the snowplow vehicle, the frame lift mechanism
16
(
FIG. 1
) operates to raise the snowplow mechanism
13
(FIG.
1
). Conversely, when the lift control lever
46
A is pushed or tilted forward of the snowplow vehicle, the frame lift mechanism
16
operates to lower the snowplow mechanism
13
.
As shown in
FIG. 4
, the propelling frame
12
is composed of a pair of parallel spaced left and right side members
61
,
61
extending in the longitudinal direction of the vehicle body
19
, a front cross member
62
interconnecting respective front portions of the side members
61
,
61
, and a rear cross member
63
interconnecting respective rear portions of the side members
61
,
61
. The propelling frame
12
further has a pair of side brackets
64
,
64
connected to left and right end portions of the rear cross member
63
adjacent to the side members
61
, and a central bracket
65
connected to a central portion of the rear cross member
63
which corresponds in position to a widthwise central portion of the propelling frame
12
.
The electric motors
21
L,
21
R assembled integrally with the speed reducers (not designated) are mounted to respective rear end portions of the side members
61
,
61
. The rear axles (not designated) that are formed by output shafts of the speed reducers are rotatably supported by the rear end portions of the side members
61
,
61
. Respective front end portions of the side members
61
,
61
have a longitudinal slot (not designated) for receiving therein a longitudinal portion of the front axle
25
so that the front axle
25
is rotatably supported on the front end portions of the side members
61
,
61
.
The left and right side brackets
64
are each comprised of a vertically extending channel member having a U-shaped cross section. The left and right handlebars
17
L,
17
R have respective lower end portions bolted to the opposite outer sides of the left and right side brackets
64
. The side brackets
64
each have a horizontal through-hole
64
a
formed in an upper end portion thereof
The vehicle frame
15
is comprised of a pair of parallel spaced left and right side members
71
,
71
extending in the longitudinal direction of the vehicle body
19
, and a horizontal mount base
72
extending between the side members
71
,
71
astride a rear half of the side members
71
for mounting the engine
14
. The vehicle frame
15
also has a support arm
73
connected to a central portion of the front edge of the mount base
72
. The side members
71
each have a horizontal through-hole
71
a
formed in a rear end portion thereof
The vehicle frame
15
is pivotally connected to the propelling frame
12
by means of pivot pins
74
(one being shown) inserted successively through the horizontal through-holes
64
a
in the side brackets
64
and the horizontal through-holes
71
a
in the side members
71
. With this pivotal connection, a front end portion of the vehicle frame
15
is movable up and down in a vertical plane relative to the propelling frame
12
.
The frame lift mechanism
16
is comprised of a cylinder actuator having a cylinder tube
81
and a piston rod
82
reciprocally movable to project from or retract into the cylinder tube
81
. The cylinder actuator is of the electro-hydraulic type, in which the piston rod
82
is reciprocated by a fluid pressure generated from a pump (not shown) driven by an electric motor
85
(FIG.
2
). The electric motor
85
is mounted on one side of the cylinder tube
81
.
The front end of the rod
82
is pivotally connected by a pin
84
to the support arm
73
of the vehicle frame
15
, and the rear end of the cylinder tube
81
is pivotally connected by a pin
83
to the central bracket
65
of the propelling frame
12
. With this arrangement, the vehicle frame
15
is movable to swing up and down in the vertical plane about the pivoted rear end portion thereof in response to extending and contracting movement of the cylinder actuator (frame lift mechanism)
16
.
The frame lift mechanism
16
of the foregoing construction operates as follows. As shown in
FIG. 5A
, when the cylinder actuator (frame lift mechanism)
16
of the snowplow vehicle
10
is in the fully contracted state (in which the piston rod
82
shown in
FIG. 4
is disposed in a fully contracted position), the auger
31
of the snowplow mechanism
13
and the front portion of the vehicle frame
15
are disposed in a lowest horizontal position.
Conversely, as shown in
FIG. 5B
, when the cylinder actuator (frame lift mechanism)
16
is in the fully extended state (in which the piston rod
82
shown in
FIG. 4
is disposed in a fully extended position), the auger
31
of the snowplow mechanism
13
and the front portion of the vehicle frame
15
are disposed in a highest inclined position.
Since the crawler belts
11
L,
11
R carried on the propelling frame
12
are in contact with the ground surface Gr, the height of the propelling frame
12
is always constant. On the other hand, the vehicle frame
15
, which is pivotally connected by the pivot pins
74
to the propelling frame
12
, is pivotally movable to swing up and down about the pivot pins
74
relative to the propelling frame
12
.
It will be appreciated that by properly manipulating the lift control lever
46
A (
FIG. 3
) so as to extend or contract the cylinder actuator (frame lift mechanism)
16
, the vehicle body
15
swings up and down relative to the propelling frame
12
to thereby raise or lower the auger
31
of the snowplow mechanism
13
mounted to the front portion of the vehicle frame
15
. When the snowplow vehicle
10
is to be moved from one place to another, the auger
31
is preferably disposed in the highest inclined position of
FIG. 5B
so as to enable the snowplow vehicle
10
to travel smoothly. During snow-removing operation of the snowplow vehicle
10
, the auger
31
is preferably disposed in the lowest horizontal position of
5
A so as to insure highly efficient snow-removing operation by the snowplow
31
. It is preferable that during the snow-removing operation, the vertical position of the auger
31
is adjusted to accommodate angulations of the ground surface Gr.
The frame lift mechanism
16
and lift control lever
46
A (
FIG. 3
) are operatively connected together so that when the lift control lever
46
A (
FIG. 3
) returns to its original neutral position, the cylinder actuator (frame lift mechanism)
16
retains its length given at that time, thereby keeping a swing angle of the auger
31
and the vehicle frame
15
relative to the propelling frame
12
.
FIG. 6
is a circuit diagram showing an electric circuit
90
including the control unit
28
and related parts thereof. The electric circuit
90
also includes an operation switch
100
connected directly to the control unit
28
. In the electric circuit
90
, the control unit
28
, a control relay
110
, an auger-up relay
120
, an auger-down relay
130
and a control lamp
140
are connected via a main switch
45
b
to the batteries
29
.
The operation switch
100
comprises a lift control switch composed of the lift control lever
46
A and a switch mechanism
101
that are assemble together so as to control operation of the electric motor
85
of the frame lift mechanism
16
.
The switch mechanism
101
of the lift control switch (operation switch)
100
has the function of a three-position toggle switch having a movable contact
102
and two fixed contacts
103
,
104
. The switch mechanism
101
and the lift control lever
46
A are operatively connected together such that when the lift control lever
46
A is in the neutral position Ne, the movable contact
102
of the operation switch
100
is also disposed in the neutral position where the movable contact
102
does not engage either of the two fixed contacts
103
,
104
. In this instance, the operation switch
100
is in the off state and no signal is generated from the operation switch
100
. When the lift control lever
46
A is pulled or tilted rearward (rightward in
FIG. 6
) to an up position Up, the movable contact
102
comes in contact with the first fixed contact
103
. This makes the operation switch
100
turn on and an “on” signal is generated from the operation control switch
100
. Similarly, when the lift control lever
46
A is pushed or tilted forward (leftward in
FIG. 6
) to a down position Dw, the movable contact
102
comes in contact with the second fixed contact
104
. This makes the operation switch
100
turn on and an “on” signal is generated from the operation switch
100
.
The control unit
28
has a first function of forcibly stopping the electric motor
85
when a preset reference time T1 has passed after the operation switch
100
is turned on or activated (or when activation of the operation switch
100
continues till a lapse of the reference tim t1). The control unit
28
also has a second function of continuing stopping the electric motor
85
when the operation switch
100
is still in the activated state after a lapse of the reference time t1. The reference tim t1 is equal to an operating time of the cylinder actuator (frame lift mechanism)
16
which is required to move the piston rod
82
over a maximum stroke between the fully extended position and the fully contacted position.
The control unit
28
performs various control operations, as enumerated below.
(1) When the operation switch
100
is in the off state (i.e., in the absence of an “on” signal from the operation switch
100
), an excitation coil
111
of the control relay
110
is kept de-energized to maintain the original “off” position of a normally open contact
112
. The control relay
110
is thus kept in the off state.
(2) When the operation switch
100
is turned on or activated (that is, when an “on” signal is produced from the operation switch
100
), the excitation coil
111
of the control relay
110
is energized to move the normally open contact
112
to an “on” or dosed position. The control relay
110
is thus turned on or activated.
(3) When the “on” signal from the operation switch
100
continues to present until the reference time T1 has elapsed after the operation switch
100
is turned on or activated, the excitation coil
111
of the control relay
110
is forcibly de-energized to return the normally open contact
112
to the original “off” or open position. The control relay
110
is thus forcibly turned off or deactivated
(4) When the “on” signal from the operation switch
100
is still present even after the lapse of the reference time T1, the de-energized state of the excitation coil
111
is continued to thereby keep the “off” or open position of the contact
112
. The control relay
110
is continuously held in the de-activated state.
(5) When the control relay
110
is in the on or activated state, this means that the electric motor
85
is operating or rotating. Under such condition, the control lamp
141
is in the on or activated state.
The auger-up relay
120
and the auger-down relay
130
are disposed between the control relay
110
and the operation switch
100
so that they operate under the control of the control relay
110
and the operation switch
100
. Furthermore, the electric motor
85
and a thermo-breaker
86
for protection of the electric motor
85
are also disposed between the auger-up relay
120
and the auger-down relay
130
so that they operate also under the control of the control relay
110
and the operation switch
100
.
The thermo-breaker
86
is a protection member incorporated in the electric motor
85
for protecting the electric motor from overheating. The thermo-breaker
86
is designed to cut off supply of electric current to the electric motor
85
when the electric motor
85
heats up to a given (overheat) temperature due to continued activation or frequent on-off operations of the operation switch
100
.
When the left control lever
46
A is in the neutral position Ne, or when the control relay
110
is in the off state (with the normally open contact
112
disposed in the original “off” or open position), the auger-up relay
120
and the auger-down relay
130
are both placed in the off condition. Under such condition, the electric motor
85
connected between the auger-up relay
120
and the auger-down relay
130
is in the off or de-energized state.
When the lift control lever
46
A is pulled or tilted down toward the “Up” side to bring the movable contact
12
into contact with the first fixed contact
103
and, at the same time, the control switch
110
is in the on state (with the normally open contact
112
disposed in the “on” or activated position), the auger-up relay
120
is turned on or activated whereupon the electric motor
85
starts rotating in a forward direction.
Conversely, when the lift control lever
46
A is pushed or tilted down toward the “Dw” side to bring the movable contact
12
into contact with the second fixed contact
104
and, at the same time, the control switch
110
is in the on state (with the normally open contact
112
disposed in the “on” or activated position), the auger-down relay
120
is turned on or activated whereupon the electric motor
85
starts rotating in a reverse direction.
The control unit
28
shown in
FIG. 6
is comprised of a microcomputer and can operate to achieve a control procedure as illustrated in the flowchart shown in FIG.
7
. The control procedure achieved in the microcomputer (control unit)
28
will be described below in conjunction with the circuit diagram shown in FIG.
6
.
The control procedure shown in
FIG. 1
begins when the main switch
45
B (
FIG. 6
) is turned on. At a first step ST
01
, a timer in a central processing unit of the microcomputer (control unit)
28
is reset to zero (Tc=0). Then ST
02
reads a signal from the operation switch
100
. Subsequently, ST
03
judges whether or not the count in the timer has not exceeded the preset reference time T1. If the result of judgment is “YES” (Tc≦T1), this means that the preset reference time has not elapsed after activation of the operation switch
100
. In this condition, the control procedure goes on to ST
04
. Alternatively, if the judgment result at ST
03
is “NO” (Tc>T1), this means that the preset reference time T1 has passed after activation of the operation switch
100
. Under such condition, the control procedure branches to ST
13
.
ST
04
, which follows ST
03
, makes a judgment to determine whether or not the “on” signal from the operation switch
100
is present. If, the result of judgment is “YES”, this means that the lift control lever
46
A has been tilted down toward the “Up” side or the “Dw” side. Under such condition, the control procedure advances to ST
05
, which turns on the control relay
110
to thereby rotate the electric motor
85
. Alternatively, if the judgment result at ST
04
is “NO”, this means that the lift control lever
46
A is in the neutral position “Ne”. The control procedure then branches to ST
14
, which turns off the control relay
110
to thereby stop the electric motor
85
.
ST
05
is followed by ST
06
. At ST
06
, a judgment is made to determine whether or not the timer is still operating. If the result of judgment is “YES”, the control procedure advances to ST
09
. Conversely, if the judgment result is “NO”, the control procedure branches to ST
07
. At ST
07
, the timer is reset to zero (Tc=0). The timer is subsequently started at ST
08
. After ST
08
, the control procedure advances to ST
09
.
ST
09
judges whether or not the count in the timer Tc has exceed the preset reference time T1 (Tc>T1). If the result of judgment is “YES”, this means that the preset reference time T1 has elapsed after activation of the operation switch
100
. Under such condition, the control goes on to ST
10
and turns off the control relay
100
to thereby forcibly stop the electric motor
85
. Alternatively, if the judgment result at ST
09
is “NO”, this means that the preset reference time T1 has not elapsed after activation of the operation switch
100
. The control procedure then returns to ST
02
.
ST
10
is followed by ST
11
where the timer in the control unit
28
is stopped. Subsequently, the control procedure advances to ST
12
, which makes a judgment to determine whether or not the control procedure is to be terminated. If the result of judgment is “YES”, the control procedure is stopped. Alternatively, if the judgment result is “NO”, the control procedure returns to ST
02
.
At ST
13
, which is branched off from ST
03
, a judgment is made to determine whether or not the “on” signal from the operation switch
100
is present. If the result of judgment is “YES”, this means that the lift control lever
46
A is still tilted down toward the “Up” side or the “Dw” side even after the lapse of the preset reference time T1. Under such condition, the control procedure goes on to ST
14
where the control relay
110
is turned off or deactivated to thereby stop the electric motor
85
. ST
14
is followed by ST
12
described previously. Alternatively, if the judgment result at ST
13
is “NO”, this means that the lift control lever
46
A is in the neutral position Ne after the lapse of the preset reference time T1. The control procedure then jumps to ST
12
where, as previously described, judgment is made to determine whether or not the control procedure is to be terminated.
It will be appreciated from the foregoing description that when the operation switch
100
(
FIG. 6
) is turned on or activated to rotate the electric motor
85
in the forward or the reverse direction, the electro-hydraulic cylinder actuator frame lift mechanism)
16
generates a fluid pressure to extend or contract the piston rod
82
. By virtue of the extending or contracting movement of the piston rod
82
, the front end portion of the vehicle frame
15
and the auger
31
mounted thereto are lifted up and down, as illustrated in
FIGS. 5A and 5B
.
When the preset reference time T1 has elapsed after activation of the operation switch
100
(T1 being equal to an operating time of the electro-hydraulic cylinder actuator
16
which is required to move the piston rod
82
over a maximum stroke defined between the fully extended position and the fully contracted position of the piston rod
82
), the control unit
28
forcibly stops the electric motor
85
even if the operation switch
100
in the “on” or activated state. By thus forcibly stopping the electric motor
85
, it is possible to cut down the operating time of the electric motor. Since the electric motor
85
is released from a heavily loaded condition soon after the arrival of the piston rod
82
at its fully extended or contracted position, the load on the frame lift mechanism
16
including the electric motor
85
is lessened and the durability of the frame lift mechanism
16
is increased.
Additionally, since the electric motor
85
is stopped when the piston rod
82
moves over the maximum stroke, generation of heat from the electric motor
85
can be suppressed The thermo-breaker
85
built in the electric motor
86
does not operate, so that the operator is allowed to continue snow-removing operation of the snowplow vehicle
10
without considering a downtime of the snowplow vehicle
10
which may occur when the thermo-breaker
86
operates. The snow-removing operation can, therefore, be achieved smoothly and efficiently.
Furthermore, the electro-hydraulic cylinder actuator (frame lift mechanism)
16
can operate smoothly and reliably without requiring detection switches provided for detecting the piston rod
82
arrived at the fully extended position and the fully contracted position. The snowplow vehicle
10
is, therefore, formed by a reduced number of parts used and has a relatively simple electric wiring system. This achieves cost cutting of the snowplow vehicle
10
.
Additionally, when the operation switch
100
is still in the activated state even after the electric motor
85
is forcibly stopped upon the lapse of the preset reference time T1 (which is equal to an operating time required for the electro-hydraulic cylinder actuator
16
to move the piston rod
82
over the maximum stroke), the control unit
28
continues to stop the electric motor
85
. Thus, a heavily loaded condition of the electric motor
85
does not recur with the result that the total load exerted on the frame lift mechanism
16
including the electric motor
85
is reduced and the durability of the frame lift mechanism
16
is increased. Additionally, since the thermo-breaker
86
is kept in the off or inactivated state, a downtime does not occur. Thus, the snow-removing operation can be continued smoothly and efficiently.
When the stroke of the piston rod
82
is changed due to the influence of snow, dirt, mud and other foreign matter, the control unit
28
forcibly stops the electric motor
85
upon the lapse of the predetermined reference time T1 regardless of the operation switch
100
being in the on or activated state. As a result, a heavily loaded condition of the electric motor
85
is immediately removed. This ensures that the total load applied to the frame lift mechanism
16
including the electric motor
85
is reduced and the durability of the frame lift mechanism
16
is increased. Additionally, by virtue of the forcible stop of the electric motor
85
, generation of heat from the electric motor
85
can be suppressed. The thermo-breaker
85
built in the electric motor
65
does not operate.
The control unit
28
shown in
FIG. 6
may be modified to have a function of integrating or adding up the running time Trα of the electric motor
85
during which the electric motor
85
is rotating and forcibly stopping the electric motor
85
when the integrated value (total sum of the running times) Tm reaches a predetermined reference value (reference time) T2. The predetermined reference value T2 corresponds to a time which is required for the electric motor
85
to heat up above a predetermined temperature. For instance, if the cumulative running time and cumulative rest time of the electric motor are represented by Tr and Ts, respectively, the integrated value (total sum) Tm of the running times is obtained by Tm=Tr−Ts.
The modified control unit, designated by
28
a
in
FIG. 6
for purposes of explanation, further has a function of continuing stopping of the electric motor
85
until a predetermined fixed time (reference time) T3 has passed.
More specifically, the modified control unit
28
a
performs various control operations, as enumerated below
(1) When the main switch
45
B (
FIG. 6
) is turned on or activated, the control relay
110
is turned on or activated.
(2) Time periods during which the “on” state signal from the operation switch
100
is present (i.e., running times Trα of the electric motor
85
during which the electric motor
85
is rotating) are integrated or added up, and when an integrated value (total sum) Tm of the running times Trα reaches the reference value T2, the control relay
100
is forcibly turned off or deactivated.
(3) After forcible de-activation of the control relay
110
, the “off” or deactivated state of the control relay
110
is continuously maintained until the reference time T3 has passed.
(4) When the control relay
110
is in the “on” state, this means that the electric motor
85
is running or rotating. Under such condition, the control lamp
141
is kept in the on or activated state.
Stated in more concretely, the cumulative running time Tr is updated each time a predetermined time has passed. That is, each time the predetermined time has passed, a running time Trα is added to the accumulated total Tr of the running times during the preceding interval (Tm=Tr+Trα). The running time Trα has a predetermined value such as 11 milliseconds (ms), which is added up, at an interval of 100 milliseconds (ms).
On the other hand, the cumulative rest time Ts is updated each time a predetermined time has passed. That is, each time the predetermined time has passed, a rest time Trβ during which the electric motor
85
is stopping or not rotating is added to the accumulated total Ts of the rest times during the preceding interval (Ts=Ts+Trβ). The rest time Trβ has a predetermined value such as 10 ms, which is added up, at an interval of 100 ms.
The thus obtained cumulative rest time Ts is subtracted from the cumulative running time Tr to thereby obtain an integrated value or total sum Tm of the rotating times (Tm=Tr−Ts).
The running time Trα (i.e., 11 ms) which is added up at intervals of 100 ms is set to be larger than the rest time (i.e., 10 ms) which is also added up at intervals of 100 ms, the reason for which is as follows.
In general, a heat-developing time, which is required for the electric motor
85
to heat up from the room temperature to a predetermined elevated temperature while it is rotating, is shorter than a heat-releasing time which is required for the electric motor
85
to cool down from the elevated temperature to the room temperature while it is at a standstill. If the running time Trα is set to be equal to the rest time Trβ, it may occur that the integrated value or total sum Tm of the running times becomes zero even though the electric motor
85
has not cooled down to the room temperature. To preclude the occurrence of this problem, the running time Trα added up at intervals of 100 ms is set to be longer than the rest time Trβ added up at intervals of 100 ms.
FIG. 8
is a timing chart illustrative of operation of the modified control unit
28
a
(FIG.
6
). In FIG.
8
(
a
), the horizontal axis represents time (ms), and the vertical axis represents the state of the operation switch
100
(FIG.
6
). In FIG.
8
(
b
), the horizontal axis represents time (ms), and the vertical axis represents an integrated value or total sum Tm (ms) of running times of the electric motor
85
. Similarly, in FIG.
8
(
c
), horizontal axis represents time (ms), and the vertical axis represents the state of the control relay
110
(FIG.
6
).
As shown in FIG.
8
(
b
), the integrated value or total sum Tm of running times of the electric motor
85
increases gradually as long as a signal indicative of the “on” or activated state of the operation switch
100
is present (namely, when the electric motor
85
is rotating). Alternatively, when the “off” or deactivated state of the operation switch
100
is present (namely, when the electric motor
85
is at rest), the integrated value or total sum Tm of running times of the electric motor
85
decreases gradually. When the total sum Tm of running times reaches the reference value T2, the control relay
110
is forcibly changed or shifted from the “on” or activated state to the “off” or de-activated state.
As shown in FIG.
8
(
c
), after forcible stopping of the control relay
110
, the “off” or deactivated state of the control relay
110
is maintained until the reference time T3 has passed. During that time, the electric motor
85
continues to stop even when the “on” state signal is received from the operation switch
100
. Thus, the total sum Tm of running times gradually decreases until the reference time T3 has passed.
FIG. 9
is a flowchart showing a control procedure achieved by the CPU incorporated in the modified control unit
28
a
shown in FIG.
6
.
At a first step ST
101
, all the values are initialized. Namely, the cumulative running time Tr, cumulative rest time Ts and the integrated value or total sum Tm of running times are all reset to zero. Then, a signal from the operation switch
100
is read in at ST
102
and, subsequently, ST
103
judges whether or not the signal from the operating switch
100
is in the “on” or activated state. If the result of judgment is “YES”, this means that the lift control lever
46
A (
FIG. 6
) has been tilted down toward the “Up” side or the “Dw” side. Under such condition, the control procedure advances to ST
104
where the control relay
110
is turned on or activated to thereby rotate the electric motor
85
. Alternatively, if the judgment result at ST
103
is “NO”, this means that the lift control lever
46
A is in the neutral position “Ne”. The control procedure then branches to ST
106
where the control relay
110
is turned off or deactivated to thereby stop the electric motor
85
.
ST
104
is followed by ST
105
where a cumulative running time Tr is determined by adding a running time Trα of the electric motor
85
to the accumulated total Tr of running times during the preceding interval (Tr=Tr+Trα). ST
106
is followed by ST
107
where a cumulative rest time Ts is determined by adding a rest time Tsβ of the electric motor
85
is added to the accumulated total Ts of rest times during the preceding interval (Ts=Ts+Tsβ). The thus determined cumulative rest time Ts is subtracted from the cumulative running time Tr so that an integrated value or total sum Tm of running times (Tm=Tr−Ts) is obtained at ST
108
.
Subsequently, ST
109
judges whether or not the total sum Tm of running times has reached the predetermined value T2 (Tm≧T2). If the result of judgment is “YES”, the control procedure goes on to ST
110
where the control relay
110
is forcibly turned off to thereby stop rotation of the electric motor
85
. Alternatively, if the judgment result at ST
109
is “NO”, the control procedure branches to ST
115
.
ST
110
is followed by ST
111
where the total sum Tm of running times is reset to zero (Tm=0). The control procedure goes on to ST
112
where the internal timer of the control unit
28
is reset to zero (Tc=0). The internal timer is started again at ST
113
, and at the next following step ST
114
a judgment is made to determine whether or not a count TC of the timer has exceeded the reference time T3 (Tc>T3). If the result of judgment is “YES”, the control procedure goes on to ST
115
Alternatively, if the judgment result at ST
114
is “NO”, ST
114
will repeat the same judgment process until Tc exceeds T3.
At ST
115
, a judgment is made to determine whether or not the control procedure is to be stopped. If the result of judgment is “ES” (for instance, when the main switch
45
B has been turned off), the control procedure is terminated. Alternatively, if the result of judgment at ST
115
is “NO”, the control procedure returns to ST
102
.
It will be appreciated from the foregoing description that in the modified arrangement shown in
FIGS. 5
,
6
,
8
and
9
, when the operation switch
100
(
FIG. 6
) is turned on or activated to rotate the electric motor
85
in the forward or the reverse direction, a hydraulic pressure is produced, and by the hydraulic pressure, the piston rod
82
of the electro-hydraulic cylinder actuator (frame lift mechanism)
16
is extended or contracted. By thus extending or contracting the piston rod
82
, the front end portion of the vehicle frame
15
and the auger
31
mounted thereto are lifted up and down, as illustrated in
FIGS. 5A and 5B
.
While the electric motor
85
is rotating, the running time Trα of the electric motor
85
is added up at uniform intervals of time, and when an integral value or total sum Tm of the running times reaches the predetermined reference time T2, the electric motor
85
is forcibly stopped by the control unit
28
a
regardless of the operation switch
100
being in the “on” or activated state. By thus forcibly stopping the electric motor
85
, the motor
85
is protected from overloading and thus has a higher degree of durability.
Additionally, the electric motor
85
is stopped rapidly without operating the thermo-breaker
86
built in the electric motor
85
. The control of the electric motor
85
depends on time and does not rely on the thermo-breaker
86
which requires a relatively long time to recover its original in operating state. It is, therefore, possible to resume rotation of the electric motor
85
in a relatively short period of time. Since snow-removing operation of the snowplow vehicle
10
can be continued without considering a downtime, which may occur when the thermo-breaker
86
operates, the efficiency of the snow-removing operation is very high.
In the arrangement using the control unit
28
a
shown in
FIG. 6
, the cumulative running time Tr and the cumulative rest time Ts of the electric motor
85
are represented by Tr and Ts, respectively, so that we can obtain an integrated value or total sum Tm of the running times of the motor
85
from the expression Tm=Tr−Ts.
It may be considered that the cumulative running time Tr is a total sum of the running times of the motor during which the electric motor
85
heats up while it is rotating, and the cumulative rest time Ts is a total sum of the rest times of the motor
85
during which the electric motor
85
cools down while it is at a standstill. By using the integrated value or total sum Tm of rotating times which is represented by the expression Tm=Tr−Ts, control of the electric motor
85
is achieved in dose match with actual heat-developing and -releasing conditions of the electric motor
85
. Since the cumulative rest time (heat-releasing time) Ts of the electric motor
85
is subtracted from the cumulative running time (heat-developing time) Tr, it is possible to elongate the time during which the integrated value or total sum Tm of running times reaches the preset reference value T2. This means that the time period during which the motor
85
continues to rotate before it is forcibly stopped can be extended The snow-removing operation of the snowplow vehicle can be achieved with improved efficiency.
Furthermore, after forcible stop of the electric motor
85
, the control unit
28
a
continues to stop the electric motor
85
until the preset reference time T3 has passed. During that time, heat developed in the electric motor
85
is released. The electric motor
85
is thus prevented from overheating and hence has an improved degree of durability.
FIG. 10
is a circuit diagram showing a control unit
28
b
and related parts thereof according to a further modification of the present invention;
The electric circuit
90
A shown in
FIG. 10
differs from the electric circuit
90
shown in
FIG. 6
only in that the control relay
110
is omitted, and the control unit
28
b
performs on-off control of the auger-up relay
120
and auger-down relay
130
by directly energizing or de-energizing the excitation coils
121
,
131
of the relays
120
,
130
. These parts which are identical to those shown in
FIG. 6
are designated by the same reference characters, and a further description thereof can be omitted.
The control unit
28
b
is designed to perform various control operations as enumerated below.
(1) When the “on” state signal from operation switch
100
is not present, the auger-up relay
120
and the auger-down relay
130
are kept in the off or deactivated state.
(2) When the lift control lever
46
A is tilted down toward the “Up” side, an “on” state signal from the operation switch
100
is received whereupon the auger-up relay
120
is turned on or activated.
(3) When the lift control lever
46
A is tilted down toward the “Dw” side, an “on” state signal from the operation switch
100
is received whereupon the auger-down relay
130
is turned on or activated.
(4) As to the function of controlling the auger-up relay
120
and the auger-down relay
130
, which is achieved through the control relay
110
in the case of the control unit
28
,
28
a
shown in FIG.
6
and described above with reference to
FIGS. 7 and 9
, the control unit
28
b
has substantially the same function even though the relays
120
,
130
are directly controlled by the control unit
28
b.
(5) when the control relay
110
is in the “on” state, this means that the electric motor
85
is running or rotating. Under such condition, the control lamp
141
is kept in the on or activated state.
The control procedure shown in the flowchart of FIG.
7
and the control procedure shown in the flowchart of
FIG. 9
may be combined to attain the advantageous effects achieved by the two control procedures. The control procedures thus combined can be achieved by appropriately modifying the control unit
28
,
28
a
or
28
b.
FIG. 11
schematically shows in plan view a walk behind self-propelled crawler snowplow vehicle according to another embodiment of the present invention.
The snowplow vehicle
210
includes a propelling body
220
having a propelling frame
221
, and a vehicle frame
230
pivotally connected at
228
,
228
to the propelling frame
221
. A snow removing unit or mechanism including an auger
231
and a blower
232
is mounted on a front end portion of the vehicle frame
230
.
The propelling body
220
further has a pair of left and right driving wheels
222
L,
222
R and a pair of left and right driven wheels
223
L,
223
R mounted to the propelling frame
221
. A pair of left and right crawler belts
224
L,
224
R is entrained around a pair of driving and driven wheels
222
L and
223
L or
222
R and
223
R on either side of the propelling frame
221
. Each of the driving wheels
222
L,
222
R is connected to an electric motor
226
L,
226
R via a speed reducer
225
L,
225
R. The vehicle frame
230
carries thereon an engine
235
, an auger clutch
236
and a rotating shaft
237
connected in driven relation to the engine
235
via the auger clutch
236
. The rotating shaft
237
is connected in driving relation to an auger shaft
238
of the auger
231
. The auger
231
and the blower
232
are housed in an auger housing
239
mounted on the front end portion of the vehicle frame
230
.
Left and right lift cylinder actuator
233
L,
233
R are disposed on opposite outer sides of the vehicle frame
230
and connected between the vehicle frame
230
and the propelling frame
221
such that in response to extending and contracting movements of respective piston rods
234
L,
234
R of the cylinder actuators
233
L,
233
R, the front end portion of the vehicle frame
230
and the auger
231
are lifted up and down relative to the propelling frame
221
Preferably, the lift cylinder actuators
233
L,
233
R comprise an electric linear actuator or an electro-hydraulic cylinder actuator that can perform extending and contracting motions at the same speed. The electric linear actuator comprises an electric motor as a power source, and a ball-screw mechanism composed of a screw rotatably driven by the electric motor within a cylinder and a nut threaded with the screw and connected at one end of an actuator rod slidably received in the cylinder. When the electric motor is driven to rotate the screw in one direction, rotary motion of the screw is converted by the nut into an extending or contracting movement of the actuator rod relative to the cylinder. The motor is designed to rotate in the forward and reverse directions at the same speed, so that the actuator rod can perform extending and contracting motions at the same speed. The electro-hydraulic cylinder actuator is formed by a combination of a hydraulic cylinder actuator and a motor-driven hydraulic pump. The pump is driven by an electric motor to produce a fluid pressure used for reciprocating a piston rod of the cylinder actuator. The electro-hydraulic cylinder actuator is designed such that an extending motion and a contacting motion occur at the same speed. In the illustrated embodiment, the lift cylinder actuators
233
L,
233
R are of the electro-hydraulic type including an electric motor for driving a hydraulic pump to produce a fluid pressure for reciprocating the piston rod
234
L,
234
R of the cylinder actuator. The electric motor and the hydraulic pump are not shown in
FIG. 11
but they are assembled with a cylinder of each cylinder actuator
233
L,
233
R in the same manner as described above with respect to the embodiment shown in
FIGS. 1-10
.
In
FIG. 11
, reference character
41
denotes a battery for supplying electric power to the electric motors
226
L,
226
R. Reference characters
42
L,
42
R denote left and right handlebars extending from a rear portion of the vehicle frame
230
obliquely upward in a rearward direction of the snowplow vehicle
210
. Reference numeral
244
denotes a control board, and reference numeral
245
denotes a control unit disposed in the control board
244
. The snowplow vehicle may be a wheeled vehicle having front and rear wheels wearing tires, or a half-crawler vehicle having front wheels wearing tires and intermediate and rear wheels connected by a crawler belt. The snow removing mechanism may include a dozer blade.
FIGS. 12A and 12B
are diagrammatical views illustrative of the arrangement and operation of the auger clutch
236
. The auger clutch
236
comprises a first or driving pulley
246
firmly connected to an output shaft (not designated) of the engine
235
, a second or driven pulley
247
firmly connected to the rotating shaft
237
, an endless belt
248
entrained around the driving and driven pulleys
246
,
247
, and a clutch actuator
249
disposed on one side of the belt
248
for applying a tension to the belt
248
. The clutch actuator
249
is preferably comprised of a solenoid-operated plunger.
As shown in
FIG. 12A
, when the clutch actuator
249
operates to tension the belt
248
, rotational motion of the driving pulley
246
is transmitted via the belt
248
to the driven pulley
247
, thereby rotating the rotating shaft
237
The auger
231
and the blower
232
that are coupled to the rotating shaft
237
are thus rotated The auger clutch
236
shown in
FIG. 12A
is in the ON or engaged state.
When the clutch actuator
249
is disposed in its original inoperating position shown in
FIG. 12B
, the belt
248
is in a free or loose state and hence has no function of transmitting rotational motion of the driving pulley
246
to the driven pulley
247
. Since the driven pulley
247
is thus isolated from rotation of the driving pulley
246
, the rotating shaft
237
does not rotate. The auger
231
and the blower
232
that are coupled to the rotating shaft
237
do not rotate. The auger clutch
236
shown in
FIG. 12B
is in the OFF or disengaged state.
FIG. 13
is a top plan view of the control board
244
of the snowplow vehicle
210
shown in FIG.
11
. As shown in
FIG. 13
, the control board
244
is equipped with an auger lift control lever (hereinafter referred to, for brevity, as “lift control lever”)
251
for raising or lowering the auger
231
(
FIG. 11
) by extending or contracting the lift cylinder actuators
233
L,
233
R (FIG.
11
), an auger clutch lever
252
for engaging or disengaging the auger clutch
236
by activating or deactivating the clutch actuator
249
(FIGS.
12
A and
12
B), a travel control lever
253
for making or breaking a power line from the batteries
241
to the electric motors
226
L,
226
R to allow or prevent rotation of the electric motors
226
L,
226
R, and a direction/speed control lever
255
for controlling the direction and speed of rotation of the electric motors
226
L,
226
R.
The lift control lever
251
is movable between a first position (auto-up position) in which an auto-up mode is selected, a second position (manual-up position) in which a manual-up mode is selected, and a third position (manual-down position) in which a manual-down mode is selected. The direction/speed control lever
254
is operatively connected with a potentiometer (variable resistor)
255
that produces a voltage signal continuously variable within a range corresponding to a range of movement of the direction/speed control lever
254
defined between a forward high speed position and a forward low speed position, and a voltage signal continuously variable within a range corresponding to a range of movement of the direction/speed control lever
254
defined between a reverse high speed position and a reverse low speed position. Based on the variable voltage signals from the potentiometer
255
, the direction and speed of travel of the snowplow vehicle
210
(FIG.
11
).
A control procedure achieved by the control unit
245
will be described below with reference to the flowchart shown in FIG.
14
.
The control procedure begins at ST
201
where a judgment is made to determine the current position of the lift control lever
251
. When the lift control lever
251
is disposed in the manual-up position and, hence, the manual-up mode of operation is selected, the control procedure advances to ST
202
where the lift cylinder actuators
233
L,
233
R are extended with the result that the auger
231
is raised to an elevated position.
When the result of judgment at ST
201
indicates that the lift control lever
251
is disposed in the manual-down position and, hence, the manual-down mode of operation is selected, the control procedure branches to ST
204
where the lift cylinder actuators
233
L,
233
R are contracted. ST
204
is followed by ST
205
where the measurement of operating time of the lift cylinder actuators
233
L,
233
R is started by using a clock friction of the control unit
245
. Stated more specifically, a motor current flowing through the electric motor of one lift cylinder actuator
233
L or
233
R is monitored, and when the motor current exceeds a predetermined value, the internal clock of the control unit
245
starts to measure time (operating time of the lift cylinder actuators
233
L,
233
R). As a result of contracting movement of the lift cylinder actuators
233
L,
233
R, the auger
231
is moved downward at ST
206
. When the lift control lever
251
is shifted from the manual-down position to the auto-up position or the manual-up position, downward movement of the auger
231
is stopped. At this time, ST
207
determines an operating time Td of the lift cylinder actuators
233
L,
233
R, which starts when the motor current exceeds the predetermined value and is ended when the auto-up position or the manual-up position is selected by the lift control lever
251
. The operating time Td thus determined is stored in the control unit
245
at ST
208
. The stored operating time Td is updated each time a shift from the manual-down mode to another operation mode occurs.
When the result of judgment at ST
201
indicates that the lift control lever
251
is disposed in the auto-up position and, hence, the auto-up operation mode is selected, the control procedure branches to ST
209
where a judgment is made to determine whether or not the direction/speed control lever
254
is disposed in the reverse position. If the result of judgment is “NO”, the control procedure goes to an end. Alternatively, if the judgment result is “YES”, the control procedure advances to ST
210
where the lift cylinder actuators
233
L,
233
R are extended for a time which is equal the operating time Td stored in the control unit
245
. By thus extending the lift cylinder actuators
233
L,
233
R, the auger
231
is raised to an elevated position at ST
211
. It is important to note that the amount of upward movement of the auger
231
(corresponding to the amount of extension of the lift cylinder actuators
233
L,
233
R) achieved by ST
210
to ST
211
in the auto-up operation mode is set to be equal to the amount of downward movement of the auger
231
(corresponding to the amount of contraction of the lift cylinder actuators
233
L,
233
R) achieved by ST
204
to ST
207
in the manual-down operation mode.
The travel condition of the snowplow vehicle
210
, which may occur immediately before the manual-down mode is selected, is considered to be a road traveling condition in which the snowplow vehicle travels on a road surface with the auger
231
held in an uppermost position, or a reversing condition in which the snowplow vehicle travels backwards on a snow-covered road surface with the auger
231
held in an elevated position intermediate between the uppermost inclined position and a lowermost horizontal position. The auger
231
, as it is in the elevated intermediate position, does not interfere with snow while the snowplow vehicle
210
is reversing. From this, according to the present invention, when the auto-up mode is selected, the auger
231
is raised to the elevated intermediate position. The auger
231
is thus automatically returned to the previous position, so that there is no possibility of interference occurring between the auger
231
and snow when the snowplow vehicle is moving backwards.
FIG. 15
is a flowchart showing a modified form of the control procedure shown in FIG.
14
. The modified control procedure makes a judgment at ST
301
so as to determine the position of the lift control lever
251
(FIG.
13
), which may take one position among the auto-up position, the manual-up position and the manual-down position. When the lift control lever
251
is disposed in the manual-up position and, hence, the manual-up mode of operation is selected, the control procedure advances to ST
302
where the lift cylinder actuators
233
L,
233
R are extended with the result that the auger
231
is raised to an elevated position.
When the result of judgment at ST
301
indicates that the lift control lever
251
is disposed in the manual-down position and, hence, the manual-down mode of operation is selected, the control procedure branches to ST
304
where the lift cylinder actuators
233
L,
233
R are contracted. ST
304
is followed by ST
305
where the measurement of operating time of the lift cylinder actuators
233
L,
233
R is started by using a dock function of the control unit
245
. Stated more specifically, a motor current flowing through the electric motor of one lift cylinder actuator
233
L or
233
R is monitored, and when the motor current exceeds a predetermined value, the internal dock of the control unit
245
starts to measure time (operating time of the lift cylinder actuators
233
L,
233
R). As a result of contracting movement of the lift cylinder actuators
233
L,
233
R, the auger
231
is moved downward at ST
306
. When the lift control lever
251
is shifted from the manual-down position to the auto-up position or the manual-up position, downward movement of the auger
231
is stopped. At this time, ST
307
determines an operating time Td of the lift cylinder actuators
233
L,
233
R, which starts when the motor current exceeds the predetermined value and is ended when the auto-up position or the manual-up position is selected by the lift control lever
251
. The operating time Td thus determined is stored in the control unit
245
at ST
308
. The stored operating time Td is updated each time a shift from the manual-down mode to another operation mode occurs.
When the result of judgment at ST
301
indicates that the lift control lever
251
is disposed in the auto-up position and, hence, the auto-up operation mode is selected, the control procedure branches to ST
309
where a judgment is made to determine whether or not the auger clutch
236
is in the “on” or engaged state. When the result of judgment is “NO”, this means that the auger clutch
236
is in the “off” or disengaged state. In this condition, the auger
231
and the blower
232
are not rotating and, hence, they do not exert any load on the engine
235
. Accordingly, from the viewpoint of engine load, there is no difficulty caused from the forward or reverse movement of the snowplow vehicle with the auger kept in the lowermost horizontal position. Thus, the control procedure is terminated.
When the judgment result at ST
309
is “YES”, this means that the auger clutch
236
is in the “on” or engaged state. In this condition, since the auger
231
and the blower
232
are rotating, they may exert influences on the engine load. Accordingly, the control procedure goes to ST
310
where a judgment is made to determine whether or not the travel control lever
253
(
FIG. 13
) is in the “DRIVE” position. When the result of judgment is “NO”, this means that the travel control lever
253
is in the “STOP” position. In this condition, since the snowplow vehicle
210
is not moving in either direction, the rotating auger
231
does not give any influence on the engine load even when it is disposed in the lowermost horizontal position. Thus, the control procedure is terminated.
When the judgment result at ST
310
is “YES”, this means that the travel control lever
253
is in the “DRIVE” position. In this condition, since the snowplow vehicle
210
is running in either direction, the rotating auger
231
may exert negative influence on the engine load if it is disposed in the lowermost horizontal position. Thus, the control procedure further advances to ST
311
where a judgment is made to determine whether or not the direction/speed control lever
254
(
FIG. 13
) is in the “REVERSE” position. If the result of judgment is “NO”, this means that the direction/speed control lever
254
is in the “FORWARD” position. In this condition, since the snowplow vehicle
210
is moving forward to achieve, for example, the snow-removing operation, automatic rising of the rotating auger
231
is not necessary. Accordingly, the control procedure is terminated.
When the judgment result at ST
311
is “YES”, this means that the direction/speed control lever
254
is in the “REVERSE” position. In this condition, since the snowplow vehicle
210
is to be moving backward while rotating the auger
231
, the auger
231
will excessively increase engine load if it is disposed in the lowermost horizontal position. To preclude the occurrence of this problem, the control procedure goes on to ST
312
where the lift cylinder actuators
233
L,
233
R are extended for a time which is equal the operating time Td stored in the control unit
245
at ST
308
. By thus extending the lift cylinder actuators
233
L,
233
R, the auger
231
is raised to the elevated intermediate position at ST
313
. The auger
231
is thus automatically returned to the previous position, so that there is no fear of interference occurring between the auger
231
and snow when the snowplow vehicle is moving backwards.
In the control procedure shown in the flowchart of
FIG. 15
, the order or sequence of ST
309
to ST
311
may be changed. It will be appreciated from the foregoing description that the lift cylinder actuators
233
L,
233
R are operated to raise the auger
213
when at least three items of information have been received in the control units
245
. The first information item is obtained at ST
301
and represents that the set-up operation mode has been selected. The second information item is obtained at ST
311
and represents that the snowplow vehicle
210
is to be moved backward. The third information item is obtained at ST
309
and represents that the auger clutch
236
disposed between the power source or engine
235
and the snow-removing mechanism
231
,
232
is in the “on” or engaged state. In the auto-up operation mode, the auger
231
is raised to the elevated intermediate position and not to the uppermost inclined position. Accordingly, when the auto-up operation mode is followed by the manual-down operation mode, the auger
231
can be lowered to the lowermost horizontal position in a relatively short time. This will increase the efficiency of the snow-removing operation.
Furthermore, according to the modified control procedure shown in
FIG. 15
, when the auto-up operation mode is selected, if the anger clutch
236
is in the “off” or disengaged state, the auger
231
and the blower
232
are not raised even though the snowplow vehicle is to be moved backward. There is no difficulty caused from the snowplow vehicle
210
moving backward with the auger
231
and the blower
232
disposed in the lowermost horizontal position so long as the auger
231
and the blower
232
are not operating. As a result, in the snowplow vehicle involving frequently repeated forward and reverse movements, it is possible to reduce the number of operations required to automatically raise the auger
231
and the blower
232
to the elevated intermediate position. This will reduce the number of on-off operations of the auger clutch
236
and elongate the service life of the auger clutch
236
, correspondingly. The auto-up operation necessarily reduces the load on the human operator.
The auger clutch
236
should by no means be limited to the belt clutch structure shown in
FIGS. 12A and 12B
but may include an electromagnetic clutch, a mechanical gear teeth clutch and the like. Furthermore, the power source used for driving the auger
231
and the blower
232
is in the form of an engine
235
. The engine
235
may be replaced by an electric motor. Similarly, the power source used for propelling the snowplow vehicle
210
is comprised of electric motors
226
L,
226
R. The electric motors
226
L,
226
R may be replaced with an engine.
In the embodiment shown in
FIG. 11
, the lift cylinder actuators
233
L,
233
R are designed to extend and contract at the same speed, so that the amount of upward movement of the auger
231
and the amount of downward movement of the auger
231
can be made equal to each other by determining an operating time Td of these cylinder actuators
233
L,
233
R. In the case where the speed of extension and the speed of contraction of the cylinder actuators
233
L,
233
R are different from each other, a stroke sensor (not shown) may be associated with one of the cylinder actuators
233
L,
233
R so as to determine the amounts of extension and contraction of the cylinder actuators
233
L,
233
R.
Obviously, various minor changes and modifications of the present invention are possible in the light of the above teaching. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.
The present disclosure relates to the subject matters of Japanese Patent Applications Nos. 2001-276075, 2001-301013, and 2001-301228, filed Sep. 12, 2001, Sep. 28, 2001 and Sep. 28, 2001, respectively, the disclosures of which are expressly incorporated herein by reference in their entireties.
Claims
- 1. A self-propelled snowplow vehicle comprising:a propelling frame equipped with driving wheels for driving the snowplow vehicle; a vehicle frame equipped with an auger at a front end portion thereof for removing snow, the vehicle frame being pivotally connected to the propelling frame; a frame lift mechanism for lifting the front end portion of the vehicle frame up and down relative to the propelling frame, the frame lift mechanism including an electro-hydraulic cylinder actuator having a piston rod and an electric motor rotatably driven to produce a fluid pressure for reciprocating the piston rod between a fully contracted position and fully extended position; an operation switch manually activated to drive the electric motor in either direction; and a control unit for controlling operation of the electric motor thereby to control operation of the frame lift mechanism, the control unit being arranged to add up running times of the electric motor when a total sum of the running times reaches a predetermined reference value.
- 2. A self-propelled snowplow vehicle according to claim 1, wherein the total sum (Tm) of the running times is obtained by the expressionTm=Tr−Ts where Tr represents an accumulated total of the running times during which the electric motor is rotating, and Ts represents an accumulated total of the rest times during which the electric motor is at a standstill.
- 3. A self-propelled snowplow vehicle according to claim 2, wherein the control unit continues to stop the electric motor until a preset fixed time has passed after forcible stop of the electric motor.
- 4. A self-propelled snowplow vehicle according to claim 3, wherein the running times of the electric motor have a fixed value and are added up at the lapse of a unit time, and the rest times of the electric motor have a fixed value and are added up at the lapse of the unit time, and wherein the fixed value of the running times is larger than the fixed value of the rest times.
- 5. A self-propelled snowplow vehicle according to claim 2, wherein the running times of the electric motor have a fixed value and are added up at the lapse of a unit time, and the rest times of the electric motor have a fixed value and are added up at the lapse of the unit time, and wherein the fixed value of the running times is larger than the fixed value of the rest times.
- 6. A self-propelled snowplow vehicle according to claim 1, wherein the control unit continues to stop the electric motor until a preset fixed time has passed after forcible stop of the electric motor.
- 7. A self-propelled snowplow vehicle according to claim 6, wherein the running times of the electric motor have a fixed value and are added up at the lapse of a unit time.
- 8. A self-propelled snowplow vehicle according to claim 1, wherein the running times of the electric motor have a fixed value and are added up at the lapse of a unit time.
- 9. A self-propelled snowplow vehicle comprising:a propelling frame equipped with driving wheels for driving the snowplow vehicle; a vehicle frame equipped with an auger at a front end portion thereof for removing snow, the vehicle frame being pivotally connected to the propelling frame; a frame lift mechanism for lifting the front end portion of the vehicle frame up and down relative to the propelling frame, the frame lift mechanism including an electro-hydraulic cylinder actuator having a piston rod and an electric motor rotatably driven to produce a fluid pressure for reciprocating the piston rod between a fully contracted position and a fully extended position; an operation switch manually activated to drive the electric motor in either direction; and a control unit for controlling operation of the electric motor thereby to control operation of the frame lift mechanism; wherein the snowplow vehicle has three modes of operation including a manual-up mode in which the auger is raised manually, a manual-down mode in which the auger is lowered manually, and an auto-up mode in which the auger is automatically raised, and wherein the control unit is arranged such that when the manual-down mode is selected, the control unit determines and stores an amount of contraction of the piston rod achieved in the selected manual-down mode, and when the manual-down mode is followed by the auto-up mode and information representing reversing of the direction of rotation of the driving wheels is received, the control unit performs an auto-up control of the piston rod in which the piston rod is extended by an amount equal to the amount of contraction of the piston rod determined with respect to the preceding manual-down mode.
- 10. A self-propelled snowplow vehicle according to claim 9, wherein the piston rod of the electro-hydraulic cylinder actuator is extended and contracted at the same speed, and the amount of contraction of the piston rod is determined depending on time.
- 11. A self-propelled snowplow vehicle according to claim 10, wherein when the piston rod of the cylinder actuator is in the fully extended position, the auger is disposed in an uppermost inclined position, and when the piston rod of the cylinder actuator is in the fully contracted position, the auger is disposed in a lowermost horizontal position, and wherein in the auto-up mode, the auger is raised to an elevated position located intermediately between the uppermost inclined position and the lowermost horizontal position.
- 12. A self-propelled snowplow vehicle according to claim 11, further including a power source for supplying rotational power to the auger and an auger clutch disposed between the power source and the auger for transmitting the rotational power from the power source to the auger, wherein when the auger clutch is in a disengaged state, the control unit disables the auto-up control of the piston rod of the cylinder actuator.
- 13. A self-propelled snowplow vehicle according to claim 10, further including a power source for supplying rotational power to the auger and an auger clutch disposed between the power source and the auger for transmitting the rotational power form the power source to the auger, wherein when the auger clutch is in a disengaged state, the control unit disables the auto-up control of the piston rod of the cylinder actuator.
- 14. A self-propelled snowplow vehicle according to claim 9, wherein when the piston rod of the cylinder actuator is in the fully extended position, the auger is disposed in an uppermost inclined position, and when the piston rod of the cylinder actuator is in the fully contracted position, the auger is disposed in a lowermost horizontal position, and wherein in the auto-up mode, the auger is raised to an elevated position located intermediately between the uppermost inclined position and the lowermost horizontal position.
- 15. A self-propelled snowplow vehicle according to claim 14, further including a power source for supplying rotational power to the auger and an auger clutch disposed between the power source and the auger for transmitting the rotational power from the power source to the auger, wherein when the auger clutch is in a disengaged state, the control unit disables the auto-up control of the piston rod of the cylinder actuator.
- 16. A self-propelled snowplow vehicle according to claim 9, further including a power source for supplying rotational power to the auger and auger clutch disposed between the power source and the auger for transmitting the rotational power from the power source to the auger, wherein when the auger clutch is in a disengaged state, the control unit disables the auto-up control of the piston rod of the cylinder actuator.
- 17. A self-propelled snowplow vehicle comprising:a propelling frame equipped with driving wheels for driving the snowplow vehicle; a vehicle frame equipped with an auger at a front end portion thereof for removing snow, the vehicle frame being pivotally connected to the propelling frame; a frame lift mechanism for lifting the front end portion of the vehicle frame up and down relative to the propelling frame, the frame lift mechanism including an electro-hydraulic cylinder actuator having a piston rod and an electric motor rotatably driven to produce a fluid pressure for reciprocating the piston rod between a fully contracted position and a fully extended position; an operation switch manually activated to drive the electric motor in either direction; and a control unit for controlling operation of the electric motor thereby to control operation of the frame lift mechanism, the control unit being arranged to forcibly stop the electric motor when a predetermined time has elapsed after the operation switch is activated, the predetermined time being equal to an operating time of the cylinder actuator which is required to extend or contract the piston rod over a maximum stroke defined between the fully extended position and fully contracted position.
- 18. A self-propelled snowplow vehicle according to claim 17, wherein the control unit continues to stop the electric motor when the operation switch is still in the activated state even after the lapse of the predetermined time.
Priority Claims (3)
Number |
Date |
Country |
Kind |
2001-276075 |
Sep 2001 |
JP |
|
2001-301013 |
Sep 2001 |
JP |
|
2001-301228 |
Sep 2001 |
JP |
|
US Referenced Citations (12)
Foreign Referenced Citations (1)
Number |
Date |
Country |
04194109 |
Jul 1992 |
JP |