Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
2000-08-09
2002-05-21
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S329000, C060S452000
Reexamination Certificate
active
06389808
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control unit for a construction machine, and more particularly, to a control unit for a construction machine capable of operating while switching operation mode between a low-speed operation mode and a high-speed operation mode.
2. Description of Relevant Art
A conventional control unit for a construction machine of this kind will be explained with reference to
FIGS. 2
,
3
and
7
.
FIG. 2
is a diagram showing performance of a pump,
FIG. 3
is a diagram showing performance of an engine. These drawings are used also for explaining an embodiment of the present invention.
FIG. 7
is a diagram of a control circuit of mainly a hydraulic shovel.
In
FIG. 7
, a reference number
12
represents a first hydraulic pump
12
, and a reference number
13
represents a second hydraulic pump. Control valves
1
to
8
for various actuators such as a boom, an arm a bucket and a cylinder are connected to oil paths of the first and second hydraulic pumps
12
and
13
. The first and second hydraulic pumps
12
and
13
are driven by an engine
19
. A fuel-injection amount and a fuel-injection timing of the engine
19
are adjusted by a control actuator
20
of an engine governor. The control actuator
20
of the engine governor is operated by a command signal from a controller
21
. Discharged oil from the first and second hydraulic pumps
12
and
13
is controlled by an actuator
15
comprising a solenoid proportional valve. The actuator
15
is operated by a command signal from the controller
21
.
The construction machine is constructed such that it can be operated while switching operation mode between a low-speed operation mode and a high-speed operation mode. The switching operation is carried out by manually operating, by an operator, an operation-mode selecting switch
26
connected to the controller
21
. In the drawing, a reference number
14
represents a pilot pump, and a reference number
22
represents a battery.
As shown in
FIGS. 2 and 3
, the operation mode comprises A mode having excellent speed and power (which will be referred to as “high-speed operation mode” hereinafter), and B mode suitable for low fuel-consumption and fine operation (which will be referred to as “low-speed operation mode” hereinafter). The operator manually operate the operation-mode selecting switch
26
to select desired either one of the operation modes. The controller
21
recognizes ON and OFF of the operation-mode selecting switch
26
. When the operation-mode selecting switch
26
is ON for example, the controller
21
judges that the high-speed operation mode was selected, the controller
21
sends a command signal to the actuator
20
of the engine governor which controls the engine
19
, thereby switching the engine
19
to the high-speed operation mode. At the same time, the controller
21
also sends a command signal to the actuator
15
which controls discharging oil of the first and second hydraulic pumps
12
and
13
, and the discharge oil of the first and second hydraulic pumps
12
and
13
is switched, by the actuator
15
, to high output state which is suitable for the high-speed operation mode.
When the operation-mode selecting switch
26
was switched to OFF manually by the operator, the controller
21
sends a command signal to the actuators
20
and
15
so that the engine
19
as well as the first and second hydraulic pumps
12
and
13
are switched to the low-speed operation mode, and the operation in the low-speed operation mode is carried out.
When the operation-mode selecting switch is switched to the high-speed operation mode by the operator's manual operation, since the high-speed operation mode is excellent in speed and power, the mode is suitable for operation requiring high speed or great load. However, during a series of operation in the high-speed operation mode, even when the construction machine is operating with low load or under fine control, such an operation is carried out while keeping the high engine output and thus, fuel is consumed wastefully. In order to avoid such a wasteful fuel consumption, the operation-mode selecting switch must be switched to the low-speed operation mode by the manual operation whenever it is required. Such a switching operation is troublesome. Generally, the operator does not carry out the switching operation, and fuel is consumed wasteful as described above.
When the operator switches the operation-mode selecting switch
26
to carry out operation in the low-speed operation mode, the low-speed operation mode is excellent for fine operation by the operator and reduction in fuel, but when it is desired to operate the machine faster during the series of operation in the low-speed operation mode, or when greater power is required, speed and power of this mode are insufficient, and this mode can not satisfy the speed and power that the operator requires. It is extremely troublesome to manually switch the operation-mode selecting switch to avoid this each time.
SUMMARY OF THE INVENTION
In the construction machine which is operated while selecting either one of the high-speed operation mode and the low-speed operation mode, there is a technical problem to be solved for satisfying both the low fuel consumption of the engine and appropriate operation speed without troublesome switching operation of the operation-mode selecting switch by manual operation of the operator as in the convention technique, and it is an object of the present invention to solve the problem.
The present invention has been proposed to achieve the above object, and the invention provides a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the low-speed operation mode and when a pressure sensor detects an operating speed of an operating lever of the remote-control valve and the detection value exceeded a predetermined value, the operation mode is automatically switched from the low-speed operation mode to the high-speed operation mode by a command signal from a controller: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the low-speed operation mode and when the sum of detection values detected by pressure sensors respectively provided for detecting pressures of the first and second hydraulic pumps exceeded a predetermined value for a predetermined time or longer, the operation mode is automatically switched from the low-speed operation mode to the high-speed operation mode by a command signal from a controller: a control unit for a construction machine comprising a first hydraulic pump and a second hydraulic pump driven by an engine, in which control valves for various actuators are connected to oil paths of the hydraulic pumps, the control valves are operated by a remote-control valve, an operation mode of the construction machine can be switched to either one of a low-speed operation mode and a high-speed operation mode, wherein when the construction machine is operated in the high-speed operation mode and when a pressure sensor detects a hydraulic pressure of the hydraulic pump connected to a boom and the detection value becomes equal to or lower than a predetermined value, the operation mode is automatically switched from the high-speed
Fattibene Arthur T.
Fattibene Paul A.
Fattibene & Fattibene
Lazo Thomas E.
Look Edward K.
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