U.S. patent application number 13/721992 was filed with the patent office on 2013-07-11 for engine control system for construction machine.
This patent application is currently assigned to HITACHI CONSTRUCTION MACHINERY CO., LTD.. The applicant listed for this patent is HITACHI CONSTRUCTION MACHINERY CO., LTD. Invention is credited to Yasushi ARAI, Masanori EZAWA, Shouhei KAMIYA.
Application Number | 20130174539 13/721992 |
Document ID | / |
Family ID | 47602948 |
Filed Date | 2013-07-11 |
United States Patent
Application |
20130174539 |
Kind Code |
A1 |
EZAWA; Masanori ; et
al. |
July 11, 2013 |
Engine Control System for Construction Machine
Abstract
Disclosed is an engine control system for a construction machine
having an engine and a control device for controlling, via a
directional control valve, a flow of pressure oil to be fed to a
hydraulic actuator. The system is provided with a controller, which
includes a manipulation state determination unit for the control
device and an idle stop control unit for performing idle stop
control when the control device is determined to have remained
unmanipulated. The system also includes a temperature sensing
device for a fluid relevant to the operation of the engine. The
controller includes a unit for determining whether or not the
temperature of the fluid is not higher than a predetermined
temperature. When the temperature of the fluid is determined to be
not higher than the predetermined temperature, the controller
disables the idle stop control.
Inventors: |
EZAWA; Masanori;
(Tsuchiura-shi, JP) ; ARAI; Yasushi;
(Tsuchiura-shi, JP) ; KAMIYA; Shouhei;
(Tsuchiura-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI CONSTRUCTION MACHINERY CO., LTD; |
Tokyo |
|
JP |
|
|
Assignee: |
HITACHI CONSTRUCTION MACHINERY CO.,
LTD.
Tokyo
JP
|
Family ID: |
47602948 |
Appl. No.: |
13/721992 |
Filed: |
December 20, 2012 |
Current U.S.
Class: |
60/431 |
Current CPC
Class: |
F02D 41/042 20130101;
Y02T 10/40 20130101; E02F 9/2296 20130101; F02N 2200/023 20130101;
Y02T 10/48 20130101; F02D 2200/0606 20130101; E02B 1/00 20130101;
F02D 2200/021 20130101; E02F 9/2246 20130101; F02D 31/001 20130101;
F02N 11/0837 20130101; F02D 2200/023 20130101 |
Class at
Publication: |
60/431 |
International
Class: |
E02B 1/00 20060101
E02B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 11, 2012 |
JP |
2012-003295 |
Claims
1. An engine control system for a construction machine provided
with an engine, a hydraulic pump drivable by the engine, a
hydraulic actuator drivable by pressure oil delivered from the
hydraulic pump, a directional control valve for controlling a flow
of pressure oil to be fed from the hydraulic pump to the hydraulic
actuator, and a control device for switchingly controlling the
directional control valve, and said engine control system being
provided with a controller, which includes a manipulation state
determination unit for determining a manipulation state of the
control device and an idle stop control unit for performing idle
stop control to stop an operation of the engine when the control
device is determined to have remained unmanipulated for a
predetermined time at the manipulation state determination unit,
wherein the engine control system is provided with a temperature
sensing device for detecting a temperature of a fluid relevant to
the operation of the engine, the controller comprises a temperature
determination unit for determining whether or not the temperature
of the fluid as detected by the temperature sensing device is not
higher than a predetermined temperature set beforehand, and, when
the temperature of the fluid is determined to be not higher than
the predetermined temperature at the temperature determination
unit, the controller performs processing to disable the idle stop
control by the idle stop control unit.
2. The engine control system according to claim 1, wherein: the
controller is provided with an idle operation control unit for
holding an rpm of the engine at an idle rpm, which is a
predetermined low rpm, when the control device is determined by the
manipulation state determination unit to have been brought from a
manipulated state to an unmanipulated state, and the idle stop
control unit performs processing to stop the operation of the
engine when the control device is determined by the manipulation
state determination unit to have been unmanipulated for a
predetermined time from a start of idle operation control by the
idle operation control unit.
3. The engine control system according to claim 1, wherein: the
fluid comprises working oil for driving the hydraulic actuator, and
the temperature sensing device comprises a temperature sensor for
detecting a temperature of the working oil.
4. The engine control system according to claim 1, wherein: the
fluid comprises engine coolant for cooling the engine, and the
temperature sensing device comprises a temperature sensor for
detecting a temperature of the engine coolant.
5. The engine control system according to claim 1, wherein: the
fluid comprises fuel for the engine, and the temperature sensing
device comprises a temperature sensor for detecting a temperature
of the fuel.
6. The engine control system according to claim 1, wherein: the
fluid comprises air in a work environment where the construction
machine is placed, and the temperature sensing device comprises a
temperature sensor for detecting a temperature of the air to be
introduced into an intake pipe of the engine.
7. The engine control system according to claim 2, wherein: the
fluid comprises working oil for driving the hydraulic actuator, and
the temperature sensing device comprises a temperature sensor for
detecting a temperature of the working oil.
8. The engine control system according to claim 2, wherein: the
fluid comprises engine coolant for cooling the engine, and the
temperature sensing device comprises a temperature sensor for
detecting a temperature of the engine coolant.
9. The engine control system according to claim 2, wherein: the
fluid comprises fuel for the engine, and the temperature sensing
device comprises a temperature sensor for detecting a temperature
of the fuel.
10. The engine control system according to claim 2, wherein: the
fluid comprises air in a work environment where the construction
machine is placed, and the temperature sensing device comprises a
temperature sensor for detecting a temperature of the air to be
introduced into an intake pipe of the engine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority of Japanese Patent
Application 2012-003295 filed Jan. 11, 2012, which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to an engine control system for a
construction machine such as a hydraulic excavator, which after a
predetermined time from the commencement of an idle operation
state, can perform idle stop control that automatically stops an
operation of an engine.
[0004] 2. Description of the Related Art
[0005] As a conventional technology of this kind, an engine control
system for a working machine is disclosed in JP-A-2003-65097. This
conventional technology is equipped with a controller. This
controller automatically stops an operation of an engine when a
single-touch operation pushbutton switch, that is, an idle stop
switch is operated during idling of the engine, and also performs
idle stop control to automatically stop the operation of the engine
when a state in which a control lever remains unmanipulated has
continued longer than a predetermined time.
SUMMARY OF THE INVENTION
[0006] With the above-mentioned conventional technology, a problem
however tends to arise when the working machine is placed under a
work environment of low temperature to perform work. Under such a
work environment of low temperature, the temperature of air is low,
and as a consequence, the temperature of working oil for driving a
hydraulic actuator, the temperature of engine coolant for cooling
the engine and the temperature of fuel for the engine are lowered,
so that the engine is prone to cooling. When the idle stop switch
is operated and the control lever is returned from a manipulated
position, where work is being performed, to a neutral position to
temporarily stop the work, the above-mentioned conventional
technology brings the engine to an idle operation state in which
the rpm of the engine is a predetermined low rpm, and after an
elapse of a predetermined time, performs idle stop control to stop
the operation of the engine even under such a work environment of
low temperature.
[0007] Under a work environment of low temperature, however, an
engine is hard to start when an attempt is made to start the engine
for the resumption of work after a while from stopping an operation
of the engine as mentioned above, because the engine has been
cooled. Therefore, a longer cranking time is needed from an
operation of a starter switch by an engine key until a start-up of
the engine. Moreover, working oil of low temperature has a high
viscosity, and therefore, needs a greater torque for driving a
hydraulic pump so that a greater load is exerted on the engine. In
addition, fuel of low temperature leads to solidification of wax
components contained in the fuel, thereby inducing such wax
components to deposit on a fuel filter, and hence, lowering the
feed capability of fuel to the engine. Due to these causes, the
engine becomes hard to start as mentioned above.
[0008] With the conventional technology, a longer cranking time is
needed as mentioned above when desired to resume the discontinued
work under a work environment of low temperature after idle stop
control was performed. Therefore, a greater power consumption is
needed in connection with this start-up of the engine, and an
economical problem arises. Furthermore, a longer cranking time is
required until the work can be resumed, leading to problems that a
sense of uncertainty is given to the operator and the work
efficiency tends to decrease.
[0009] With the above-mentioned actual situation of the
conventional technology in view, the present invention has as an
object thereof the provision of an engine control system for a
construction machine, which can save a power consumption relevant
to a start-up of an engine under a work environment of low
temperature and can also promptly resume work after the work is
once stopped temporarily.
[0010] To achieve the above-described object, the present invention
is characterized in that in an engine control system for a
construction machine provided with an engine, a hydraulic pump
drivable by the engine, a hydraulic actuator drivable by pressure
oil delivered from the hydraulic pump, a directional control valve
for controlling a flow of pressure oil to be fed from the hydraulic
pump to the hydraulic actuator, and a control device for
switchingly controlling the directional control valve, and said
engine control system being provided with a controller, which
includes a manipulation state determination unit for determining a
manipulation state of the control device and an idle stop control
unit for performing idle stop control to stop an operation of the
engine when the control device is determined to have remained
unmanipulated for a predetermined time at the manipulation state
determination unit, the engine control system is provided with a
temperature sensing device for detecting a temperature of a fluid
relevant to the operation of the engine, the controller comprises a
temperature determination unit for determining whether or not the
temperature of the fluid as detected by the temperature sensing
device is not higher than a predetermined temperature set
beforehand, and, when the temperature of the fluid is determined to
be not higher than the predetermined temperature at the temperature
determination unit, the controller performs processing to disable
the idle stop control by the idle stop control unit.
[0011] According to the present invention constructed as described
above, the controller performs processing to forcibly disable idle
stop control when the construction machine has performed work under
a work environment of low temperature that is considered to pose a
problem on a start-up of the engine, the control device is
determined to have remained unmanipulated for the predetermined
time at the manipulation state determination unit of the controller
and a temperature detected by the temperature sensing device is
determined to be not higher than the predetermined temperature at
the temperature determination unit of the controller, although
under such conditions, idle stop control is about to be
performed.
[0012] Even when the control device is returned to a neutral
position to once stop work temporarily from a manipulated position
where the work is being performed, the operation of the engine,
therefore, continues without stopping. As a consequence, the
present invention obviates restarting the engine, and moreover,
guides working oil, engine coolant and engine fuel into circuits,
whereby the engine is kept warm to prevent cooling of the engine
which would otherwise occur due to the environment of low
temperature. In other words, the present invention does not require
to restart the engine upon resumption of work subsequent to its
discontinuation even under a work environment of low temperature
that is considered to pose a problem on a start-up of the engine,
and therefore, can save a power consumption associated with an
operation of a starter switch and can also promptly resume work
after it is once stopped temporarily.
[0013] The present invention may also be characterized in that in
the above-described invention, the controller is provided with an
idle operation control unit for holding an rpm of the engine at an
idle rpm, which is a predetermined low rpm, when the control device
is determined by the manipulation state determination unit to have
been brought from a manipulated state to an unmanipulated state,
and the idle stop control unit performs processing to stop the
operation of the engine when the control device is determined by
the manipulation state determination unit to have been
unmanipulated for a predetermined time from a start of idle
operation control by the idle operation control unit.
[0014] According to the present invention constructed as described
immediately above, when the control device is returned to the
neutral position to once stop work temporarily from a manipulated
position where the work is being performed, the engine moves to an
idle operation by the idle operation control unit of the
controller, and the idle operation is continued until the work is
resumed next. When the control device is manipulated again from the
neutral position in such a situation, the actual rpm of the engine
promptly increases according to a target rpm for the engine,
thereby making it possible to perform work as desired.
[0015] The present invention may also be characterized in that in
the above-described invention, the fluid comprises working oil for
driving the hydraulic actuator, and the temperature sensing device
comprises a temperature sensor for detecting a temperature of the
working oil.
[0016] The present invention may also be characterized in that in
the above-described invention, the fluid comprises engine coolant
for cooling the engine, and the temperature sensing device
comprises a temperature sensor for detecting a temperature of the
engine coolant.
[0017] The present invention may also be characterized in that in
the above-described invention, the fluid comprises fuel for the
engine, and the temperature sensing device comprises a temperature
sensor for detecting a temperature of the fuel.
[0018] The present invention may also be characterized in that in
the above-described invention, the fluid comprises air in a work
environment where the construction machine is placed, and the
temperature sensing device comprises a temperature sensor for
detecting a temperature of the air to be introduced into an intake
pipe of the engine.
[0019] The present invention is constructed such that the
temperature sensing device is provided for detecting the
temperature of the fluid relevant to the operation of the engine,
the controller includes the temperature determination unit for
determining whether or not the temperature of the fluid as detected
by the temperature sensing device is not higher than the
predetermined temperature set beforehand and considered to pose a
problem on a start-up of the engine, and, when the temperature of
the fluid is determined to be not higher than the predetermined
temperature at the temperature determination unit, the controller
performs processing to disable the idle stop control by the idle
stop control unit. Owing to this construction, the present
invention can save a power consumption relevant to a start-up of
the engine under a work environment of low temperature, can assure
excellent economy compared with before, can promptly resume work
after the work is once stopped temporarily, can eliminate a sense
of uncertainty conventionally tended to be given to the operator,
and compared with before, can also improve the efficiency of work
to be performed by the construction machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a side view showing a hydraulic excavator
mentioned as one example of a construction machine on which an
embodiment of the engine control system according to the present
invention is arranged.
[0021] FIG. 2 is an electrical and hydraulic circuit diagram
illustrating the embodiment of the engine control system according
to the present invention.
[0022] FIG. 3 is a flowchart depicting primary processing steps to
be executed at a controller arranged in the embodiment.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0023] The embodiment of the engine control system according to the
present invention for the construction machine will hereinafter be
described with reference to the accompanying drawings.
[0024] The construction machine on which the engine control system
according to this embodiment is arranged is, for example, a
hydraulic excavator shown in FIG. 1. This hydraulic excavator is
provided with a travel base 1, a revolving upperstructure 2 mounted
on the travel base 1, and working equipment 3 attached pivotally in
an up-and-down direction to the revolving upperstructure 2. The
working equipment 3 includes a boom 4 attached to the revolving
upperstructure 2, an arm 5 connected to a free end of the boom 4,
and a bucket 6 connected to a free end of the arm 5. The working
equipment 3 also includes a boom cylinder 4a for actuating the boom
4, an arm cylinder 5a for actuating the arm 5, and a bucket
cylinder 6a for actuating the bucket 6. An operator' s cab 7 is
arranged at a front-side position of the revolving upperstructure
2, a counterweight 8 is arranged at a rear-side position of the
revolving upperstructure 2, and an engine compartment 9 is arranged
between the operator's cab 7 and the counterweight 8.
[0025] The engine control system according to this embodiment,
which is arranged on the hydraulic excavator shown in FIG. 1, is
provided with an engine 11 arranged in the engine compartment 9 and
a hydraulic pump 12 drivable by the engine 11. Also provided are a
working oil reservoir 13 for storing working oil to be fed to the
hydraulic pump 12, a hydraulic actuator 14 collectively
representing the above-mentioned boom cylinder 4a, arm cylinder 5a
and the like all of which are drivable by pressure oil delivered
from the hydraulic pump 12, and a directional control valve 15 for
controlling a flow of pressure oil to be fed from the hydraulic
pump 12 to the hydraulic actuator 14.
[0026] In the operator's cab 7, a control device 16 is arranged.
The control device 16 has a control lever 16a to switchingly
operate the directional control valve 15. This embodiment is also
provided with a temperature sensing device for detecting a
temperature of a fluid relevant to an operation of the engine 11,
for example, a temperature sensor 20 for detecting a temperature of
the working oil, a pressure sensor 21 for detecting whether or not
the control lever 16a of the control device 16 has been
manipulated, an instruction unit for outputting an instruction
signal that indicates performance or non-performance of idle stop
control to be mentioned subsequently herein, for example, an idle
stop switch 22, and an rpm instructing device 23 for instructing a
target rpm for the engine 11.
[0027] This embodiment is further provided with a control unit to
be inputted with signals outputted from the temperature sensor 20,
pressure sensor 21, idle stop switch 22 and rpm instructing device
23, specifically a controller 17.
[0028] As illustrated in FIG. 2, the controller 17 includes a
neutral determination unit 17a, an idle operation control unit 17b,
a manipulation determination unit 17c, and an idle stop control
unit 17d. The neutral determination unit 17a determines, based on a
signal outputted from the pressure sensor 21, whether or not the
control device 16 has been returned from a manipulated position to
a neutral position. The idle operation control unit 17b holds the
rpm of the engine 11 at an idle rpm, which is a predetermined low
rpm, when the control device 16 is determined to have been returned
to the neutral position at the neutral determination unit 17a.
Based on signals outputted from the pressure sensor 21 during a
predetermined time from a commencement of idle operation control by
the idle operation control unit 17b, the manipulation determination
unit 17c determines whether or not the control device 16 has been
manipulated. The idle stop control unit 17d performs processing to
stop the operation of the engine 11 when the control device 16 is
determined to have remained unmanipulated during the predetermined
time at the manipulation determination unit 17c. It is to be noted
that the manipulation state determination unit, which determines
the manipulation state of the control device 16, is made up by the
above-mentioned neutral determination unit 17a and manipulation
determination unit 17c.
[0029] The controller 17 also includes an idle stop determination
unit 17e for determining, according to a signal outputted from the
idle stop switch 22, performance or non-performance of idle stop
control by the idle stop control unit 17d.
[0030] The controller 17 further includes a temperature
determination unit 17f . When the performance of idle stop control
by the idle stop control unit 17d has been determined at the idle
stop determination unit 17e and the control device 16 is determined
to have been returned to the neutral position at the neutral
determination unit 17a, the temperature determination unit 17f
determines whether or not the temperature of the working oil as
detected by the temperature sensor 20 is not higher than the
predetermined low temperature set beforehand and considered to pose
a problem on a start-up of the engine 11, for example, 0.degree. C.
When the temperature of the working oil is determined to be not
higher than the predetermined low temperature at the temperature
determination unit 17f, the controller 17 performs processing to
disable idle stop control by the idle stop control unit 17d.
[0031] With reference to FIG. 3, a description will be made of
primary processing steps to be executed at the controller 17 in
this embodiment, which is constructed as described above.
[0032] Upon performing digging work or the like by the hydraulic
excavator, the idle stop switch 22 is held OFF or is switched to
ON. According to a signal outputted from the idle stop switch 22,
the idle stop determination unit 17e of the controller 17
determines whether the performance or non-performance of idle stop
control has been instructed (step S1). When the idle stop switch 22
is OFF and the non-performance of idle stop control has been
instructed, normal operation control is performed (step S2).
Described specifically, when the control lever 16a of the control
device 16 is returned from a manipulated position to the neutral
position, the idle operation control unit 17b controls, based on
the determination by the neutral determination unit 17a, to bring
the rpm of the engine 11 to an idle rpm, and in this idle operation
state, the operation of the engine 11 is continued. At this time,
the idle stop control unit 17d is held to remain
non-functioning.
[0033] When the above-mentioned determination in step S1 finds that
the idle stop switch 22 is set ON and the performance of idle stop
control has been instructed, the manipulation determination unit
17c determines, based on signals outputted from the pressure sensor
21, whether or not the control device 16 was manipulated during a
predetermined time from the commencement of idle operation control
by the idle operation control unit 17b (step S3). When the control
device 16 is determined to have been manipulated, the routine moves
to step S2, where normal operation control is performed. Described
specifically, the engine 11 is operated such that the actual rpm of
the engine 11 is brought to a target rpm for the engine 11 as
instructed by the rpm instructing device 23. At this time, the
directional control valve 15 is switched according to manipulation
of the control device 16. Accordingly, pressure oil delivered from
the hydraulic pump 12 is fed to the hydraulic actuator 14 via the
directional control valve 15. The hydraulic actuator 14 is hence
actuated to drive, for example, the working equipment 3 shown in
FIG. 1 so that digging work or the like of earth or sand is
performed. When the control lever 16a of the control device 16 is
returned to the neutral position from such a manipulated position,
the rpm of the engine 11 drops to an idle operation state and this
idle operation state is continued, as mentioned above.
[0034] When by the above-mentioned determination in step S3, the
control device 16 is determined to have remained unmanipulated, it
is determined at the temperature determination unit 17f whether or
not the temperature of the working oil as detected by the
temperature sensor 20 is not higher than the predetermined low
temperature, for example, 0.degree. C. (step S4) . When, the
temperature of the working oil is determined to be higher than the
predetermined low temperature, that is, 0.degree. C., the routine
moves to step S5. In step S5, the idle stop control unit 17d
functions to perform processing that stops the operation of the
engine 11. In other words, idle stop control is performed. In this
case, resumption of the work needs to restart the engine 11. As
this restart of the engine 11 is performed in a work environment
that the temperature of the working oil is held relatively high,
the cranking time from an operation of the starter switch until a
start-up of the engine 11 can be shortened so that no problem is
imposed on the start-up of the engine 11.
[0035] When by the above-mentioned determination in step S4, the
temperature of the working oil is determined to be not higher than
the predetermined low temperature, for example, 0.degree. C., it is
indicated that the hydraulic excavator is placed under a work
environment of low temperature to perform work. The routine then
moves to step S2 to perform normal operation control. Described
specifically, when the control lever 16a of the control device 16
is returned from the manipulated position to the neutral position,
the rpm of the engine 11 is controlled to an idle rpm by the idle
operation control unit 17b, and under this idle operation control,
the operation of the engine 11 is continued. In other words,
although the idle stop switch 22 is set ON to perform idle stop
control, the idle stop control is forcibly disabled.
[0036] According to the embodiment constructed as described above,
when the hydraulic excavator is under a work environment of low
temperature and the control lever 16a is returned from a
manipulated position, where work is being performed, to the neutral
position to once stop the work temporarily, the engine 11 moves to
an idle operation by the idle operation control unit 17b of the
controller 17, and this idle operation is continued until the work
is resumed next time. As a consequence, this embodiment can
obviates restarting the engine 11, and moreover, can guide the
working oil, engine coolant and fuel for the engine 11 into
circuits, whereby cooling of the engine 11 due to the environment
of low temperature is reduced. When the control lever 16a is
manipulated again from the neutral position, the actual rpm of the
engine 11, therefore, promptly increases according to a target rpm
for the engine 11 so that desired work can be performed. Therefore,
this embodiment does not require to restart the engine 11 upon
resuming work after its temporary stop even under a work
environment of low temperature that is considered to pose a problem
on a start-up of the engine 11, and therefore, can save a power
consumption associated with an operation of the starter switch and
can assure excellent economy. Further, this embodiment can promptly
resume work after it is once stopped temporarily, can eliminate a
sense of uncertainty that is tended to be given to the operator,
and can improve the efficiency of work to be performed by the
hydraulic excavator.
[0037] In the above-described embodiment, the temperature sensor 20
for detecting the temperature of the working oil is arranged as the
temperature sensing device for detecting the temperature of the
fluid relevant to the operation of the engine 11. This invention
shall, however, not be limited to such a construction. The present
invention maybe constructed, for example, such that idle stop
control is disabled irrespective of an ON operation of the idle
stop switch 22 when a temperature sensor for detecting that the
temperature of the engine coolant is not higher than the
predetermined low temperature, for example, 0.degree. C. is
arranged as the temperature sensing device, the temperature of the
engine coolant is determined at the temperature determination unit
17f of the controller 17 as to whether or not it is not higher than
the predetermined low temperature, and the temperature of the
engine coolant is determined to be not higher than the
predetermined low temperature.
[0038] The present invention may also be constructed such that as
the temperature sensing device, a temperature sensor for detecting
that the temperature of the fuel for the engine 11 is not higher
than the predetermined low temperature, for example, 0.degree. C.
is arranged, the temperature of the fuel is determined at the
temperature determination unit 17f of the controller 17 as to
whether or not it is not higher than the predetermined low
temperature, and idle stop control is disabled irrespective of an
ON operation of the idle stop switch 22 when the temperature of the
fuel is determined to be not higher than the predetermined
temperature.
[0039] The present invention may also be constructed such that as
the temperature sensing device, a temperature sensor for detecting
that the temperature of air to be guided to an intake pipe of the
engine 11, that is, the air in a work environment where the
hydraulic excavator is placed is not higher than the predetermined
low temperature, for example, 0.degree. C. is arranged, the
temperature of the air is determined at the temperature
determination unit 17f of the controller 17 as to whether or not it
is not higher than the predetermined low temperature, and idle stop
control is disabled irrespective of an ON operation of the idle
stop switch 22 when the temperature of the air is determined to be
not higher than the predetermined temperature.
* * * * *