Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
2003-02-07
2004-11-02
Lazo, Thomas E. (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C060S422000, C060S429000, C060S430000
Reexamination Certificate
active
06810663
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control system for a hydraulic circuit for operating a plurality of actuators simultaneously.
BACKGROUND OF THE INVENTION
As shown in
FIG. 39
, a hydraulic excavator, which is a construction machine, has an undercarriage
51
and an upper structure
53
, which is mounted on the undercarriage
51
and adapted to be rotated by a turning actuator
52
. The base end of a boom
55
, which is adapted to be swung by boom actuators
54
, is secured to the upper structure
53
by a shaft. The base end of a stick
57
, which is adapted to be swung by a stick actuator
56
, is secured to the fore end of the boom
55
by a shaft. An attachment
59
or a bucket, either of which is adapted to be pivoted by a bucket actuator
58
, is secured to the fore end of the stick
57
by a shaft. The attachment
59
is a working tool to be operated by an attachment actuator
60
.
Such a hydraulic excavator as described above is provided with two pumps so that hydraulic pressures and flow rates are supplied to the actuators
52
,
54
,
56
,
58
,
60
through parallel passages by control valves that are connected to the two pumps.
Some of these actuators
52
,
54
,
56
,
58
,
60
operate by confluent flows of hydraulic oil from the two pumps, while there are those that operate solely by hydraulic oil supplied from either pump.
In the case of a hydraulic excavator, the boom actuators
54
, the stick actuator
56
, and the attachment actuator
60
operate by confluent flows of hydraulic oil from the two pumps. Examples of the actuators that operate solely by hydraulic oil supplied from either pump include the turning actuator
52
and the bucket actuator
58
.
The attachment actuator
60
, which requires a high flow rate exceeding the delivery rate of a single pump, must be driven by joining the flows of hydraulic oil from both pumps.
When operating the attachment actuator
60
, which has a feature described above, simultaneously with an actuator of a 2-pump confluent type, such as the boom actuators
54
or the stick actuator
56
, there arises a problem characteristic to parallel connection of actuators; the hydraulic oil tends to concentrate in the actuator with the lowest working pressure, thereby drastically slowing operation of the other actuators.
For example, when using an open/close breaker or the like as the attachment
59
, the working pressure for the attachment actuator
60
to open or close the breaker is lower than the working pressure for the boom actuators
54
or the stick actuator
56
to raise the boom
55
or the stick
57
. Therefore, when an operating device is operated to raise the boom
55
and/or the stick
57
while opening or closing the attachment
59
, neither the boom actuators
54
nor the stick actuator
56
is actuated until the attachment actuator
60
with the lower working pressure reaches the end of its stroke. It is thus difficult to operate these actuators in optimal synchronization.
In order to solve the above problem, an object of the present invention is to improve the function of the machine when operating a specific actuator which requires a high flow rate simultaneously with other actuators.
DISCLOSURE OF THE INVENTION
A hydraulic circuit control system according to the invention includes one or more specific control valves for controlling hydraulic fluid supplied from one or more pumps to a specific actuator, one or more other control valves for controlling hydraulic fluid supplied from said pump(s) to one or more other actuators, discriminating means for distinguishing between control conditions for operating said specific actuator alone and control conditions for operating the same simultaneously with any of the other actuators, and a controller for controlling control characteristics of the specific control valve(s) based on discriminated control conditions.
With the configuration as above, the discriminating means is capable of distinguishing the mode of operating the specific actuator by hydraulic fluid supplied from the pump(s) between operating it alone and operating it simultaneously with any of the other actuators. Therefore, when the specific actuator is operated in the combined operation mode, the specific control valve(s) and the other control valve(s) are controlled to effect optimal balance between these valves so that combined operatability of the specific actuator and the other actuator(s) is improved. When the specific actuator is operated alone, a high flow rate required by the specific actuator is ensured.
A hydraulic circuit control system according to another feature of the invention is characterized in that said one or more pumps are comprised of a plurality of pumps; said one or more specific control valves are comprised of a plurality of control valves respectively corresponding to said plurality of pumps; said one or more other control valves are comprised of a plurality of control valves respectively corresponding to said plurality of pumps; and that the controller has functions of storing control characteristics for each respective control valve and choosing the characteristics most suitable for the control conditions from among a plurality of control characteristics stored therein.
Therefore, upon receiving control conditions from the discriminating means, the controller is capable of controlling the specific control valves, which are respectively associated with the plural number of pumps, with the characteristics that have been selected from a plurality of control characteristics stored beforehand so as to be most suitable for the control conditions. As a result, the actuator is ensured of superior operatability in the combined operation mode and a high flow rate in the single operation mode.
A hydraulic circuit control system according to yet another feature of the invention is characterized in that two each pumps and specific control valves are provided and that the controller has such a function that when ascertaining combined operation of the specific actuator with any of the other actuators, the controller automatically adjusts control signals to be output to the two specific control valves so as to switch the source of hydraulic fluid to the specific actuator from the two pumps to either one of the two pumps according to pump-selecting criteria for the combined operation mode, which criteria have been set beforehand with respect to the other actuators.
With the configuration as above, when the specific actuator is operated together with any of the other actuators, one of the lines of the hydraulic fluid discharged from the two pumps is closed off by one of the two specific control valves, and the hydraulic fluid in the closed line is fed through the other control valves to the other actuators. Therefore, even when the specific actuator is operated at a pressure lower than that applied to the other actuators, combined operatability of the specific actuator and the other actuators can be improved.
A hydraulic circuit control system according to yet another feature of the invention is characterized in that the controller has a function of storing a plurality of control patterns consisting of a plurality of grouped control characteristics of the specific control valves and that the hydraulic circuit control system includes a control pattern selecting device for selecting from these control patterns the pattern most appropriate for the specific actuator.
When the specific actuator is replaced by an actuator of another kind, the control pattern selecting device permits the collective setting of a plurality of control characteristics by merely selecting the appropriate pattern for the kind of the specific actuator to be used. By thus eliminating the complication of re-setting control characteristics for each attachment individually, adjusting operation that is necessary when changing the specific actuators is facilitated.
The controller of a hydraulic circuit control system according to yet another feature of the invention is provided with a control pattern that includes such contr
Akiyama Seiichi
Konishi Hideo
Tanaka Masayuki
Darby & Darby
Lazo Thomas E.
Shin Caterpillar Mitsubishi Ltd.
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