Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Reexamination Certificate
2001-07-09
2004-01-06
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
C060S452000
Reexamination Certificate
active
06672055
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a controller for a hydraulic pump, and more particularly to a hydraulic pump controller suitable for use with hydraulic construction machines.
BACKGROUND ART
Generally, the power unit system (hydraulic system) of a hydraulic construction machine is equipped with one or a plurality of variable displacement type hydraulic pumps which are driven by engine power. For example, a hydraulic system for a hydraulic shovel that is a typical hydraulic construction machine is equipped with first and second variable displacement type hydraulic pumps
9
and
10
which are driven by power from an engine
11
, as shown in FIG.
12
. The discharge pressure oil from these hydraulic pumps
9
and
10
is supplied to a plurality of hydraulic actuators
27
and
28
through direction switching valves
15
and
17
where the opening degree varies according to the amount that manipulation levers
19
and
20
are manipulated. To supply adequate amount of pressure oil to the hydraulic actuators
27
and
28
that are compositely manipulated, it is necessary to control absorbed pump torque in good balance against engine output so that an actual engine speed can follow a target engine speed.
Hence, the hydraulic system is equipped with a controller
30
to which sensor signals are input from an engine speed sensor
22
and a pressure switch
31
. In the controller
30
, the engine speed of an engine
11
is detected based on an input signal from the engine speed sensor
22
, and it is decided, based on an input signal from the pressure sensor
31
, whether or not the hydraulic pumps
9
and
10
are discharging pressure oil. And to control the absorbed torque (or absorbed horse power) of the hydraulic pumps
9
and
10
so that the engine speed follows the target engine speed, a control signal Ps is output to regulators
12
and
13
that regulate the discharge flow rates of the hydraulic pumps
9
and
10
. In an electromagnetic proportional pressure-reducing valve
14
, electro-oil conversion is performed on the control signal Ps, and the converted signal is input to the regulators
12
and
13
.
The aforementioned conventional hydraulic-pump controller, however, cannot predict changes in the discharge flow rates of the hydraulic pumps
9
and
10
caused by manipulation of the manipulation levers
19
and
20
. Because of this, when the discharge flow rates of the hydraulic pumps
9
and
10
are transiently changed, for example, immediately after manipulation of the manipulation levers
19
and
20
, or during slight manipulation, the balance between engine output and absorbed pump torque will be lost and a fluctuation in an actual engine speed relative to a target engine speed will become great. As a result, adequate amount of pressure oil cannot be supplied to the hydraulic actuators
27
and
28
, and operability is degraded.
Further, with the conventional hydraulic-pump controller, it is necessary to perform tuning of control parameters in accordance with the type of the hydraulic shovels. That is, there is a need to amend part of the control program for each hydraulic shovel type. Besides, there is an individual difference between hydraulic shovels, even if they are of the same type. Furthermore, there are cases where working environment varies, for example, between a cold district and a warm district, and where engine fuel is changed. Thus, if individual difference, working environment, and conditions vary, tuning of control parameters, performed before shipping hydraulic shovels, will no longer be adaptable and therefore a fluctuation in an actual engine speed relative to a target engine speed will become great and will degrade operability.
The present invention has been made in view of such problems. Accordingly, it is an object of the present invention to provide a hydraulic-pump controller that is capable of controlling absorbed pump torque in good balance against engine output at all times.
Another object of the invention is to provide a hydraulic-pump controller which eliminates the necessity of tuning control parameters and amending a control program, even in the case where there is an individual difference between hydraulic construction machines, or the case where working environment varies, or the case where it is installed in a different type of hydraulic construction machine.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, there is provided a hydraulic-pump controller which is equipped in a hydraulic system, in which hydraulic pumps are driven by an engine so that operating oil is supplied to hydraulic actuators manipulated by manipulation means, and which also controls regulators of the hydraulic pumps so that absorbed torque of the hydraulic pumps balances with an output of the engine, the hydraulic-pump controller comprising:
engine speed detection means for detecting engine speed of the engine;
discharge pressure detection means for detecting discharge pressure of the hydraulic pumps;
manipulation-amount detection means for detecting an amount that the manipulation means is manipulated, or a physical quantity correlating with the amount;
discharge flow rate predicting means for predicting discharge flow-rates of the operating oil which are discharged from the hydraulic pumps according to manipulation of the manipulation means, based on an output of the discharge pressure detection means and an output of the manipulation-amount detection means;
predictive engine speed computing means for calculating the absorbed torque of the hydraulic pumps, based on the discharge flow rates predicted by the discharge flow rate predicting means and an output of the discharge pressure detection means, and then computing a predictive engine speed of the engine from the calculated absorbed torque of the hydraulic pumps; and
regulator control means for controlling the regulators, based on a deviation between the predictive engine speed computed by the predictive engine speed computing means and an actual engine speed detected by the engine speed detection means.
With this construction, the discharge flow rates of the operating oil, that are discharged from the hydraulic pumps being operated can be predicted according to manipulation of the manipulation means, based on the discharge pressure of the hydraulic pumps, and based on the manipulation amount of the manipulation means, or a physical quantity correlating with the manipulation amount. Therefore, it is possible to make the actual engine speed of the engine follow the predictive engine speed, without losing the balance between the engine output and the absorbed pump torque, immediately after lever manipulation, or during slight manipulation. Thus, the hydraulic-pump controller of the present is capable to of preventing operability degradation due to engine speed fluctuations.
In a preferred form of the present invention, the regulator control means is a means for controlling the regulators by employing fuzzy reasoning. The regulator control means includes conformability computing means for setting a plurality of antecedent conditions in accordance with a range of operating states of the hydraulic system and then computing conformability of each antecedent condition relative to physical quantities representing the operating states, and learning-correction means for setting a plurality of control parameters for controlling the regulators, in accordance with the antecedent conditions, and for learning and correcting each of the control parameters, based on both the deviation between the predictive engine speed and the actual engine speed and the conformability of each antecedent condition computed by the conformability computing means, and then outputting the corrected control parameters to the regulators.
Thus, the hydraulic-pump controller is robust in control, because it employs fuzzy reasoning to control the regulators. In addition, based on the conformability of each antecedent condition relative to a quantity representing the operating state of the hydraulic system, and
Akiyama Seiichi
Arai Kenji
Konishi Hideo
Nomura Masumi
Leslie Michael
Look Edward K.
Morrison & Foerster / LLP
Shin Caterpillar Mitsubishi Ltd.
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