Hybrid construction equipment

Details Hybrid construction equipment Hybrid construction equipment

2002-02-25

2004-03-23

Johnson, Brian L. (Department: 3618)

Motor vehicles

Motor as source of power for other machine

Other machine is vehicle accessory

C037S348000

Reexamination Certificate

active

06708787

ABSTRACT:

TECHNICAL FIELD
The present invention relates to hybrid construction equipment.
BACKGROUND ART
As for conventional construction equipment, a hydraulic drive type is mainstream. For example, a hydraulic shovel performs driving of a working machine, revolving of an upper revolving superstructure and traveling of a lower traveling unit with a hydraulic actuator (for example, a hydraulic cylinder, a hydraulic motor and the like). An operation is carried out by controlling pressure oil discharged from a hydraulic pump with an engine as a driving source and supplied to the hydraulic actuator as described above.
Operations of the hydraulic shovel include not only operations always requiring 100% of a capacity of an engine, but also many operations that only require, for example, 90% or 80% of its capacity. Specifically, as shown in an engine torque characteristic diagram in
FIG. 3
, in regard to a point PH of “a heavy load mode” in which a heavy load operation with 100% of its output is performed, operation modes such as a point PS of “an ordinary load mode” in which an ordinary load operation is performed, and a point PL of “a light load mode” in which a light load operation is performed are set. At each of the points PH, PS and PL, an equal horsepower control is performed so that absorption torque of a hydraulic pump matches with output torque of the engine, whereby the output of the engine is effectively utilized to improve fuel economy. Here, “equal horsepower control for matching” means controlling the discharge amount of the hydraulic pump according to a PQ curve (an equal horsepower curve) so as to be able to obtain the absorption torque at the matching point. Further, the absorption torque of the hydraulic pump means torque required of the engine by the hydraulic pump to drive a hydraulic actuator.
In the above-described hydraulic shovel, mounted is an engine having output power corresponding to the maximum required horsepower when a vehicle performs operations, that is, an engine with a rated output point PH of the engine torque curve corresponding onto a maximum required horsepower line L shown in FIG.
3
.
FIG. 4
is a graph showing a transition of absorption horsepower of the hydraulic pump in one cycle when “an excavating and loading operation” in which excavated earth and sand are rotated and loaded into a damp vehicle is carried out in “the ordinary load mode” in which matching is achieved with 90% of rated output power of the engine. Load change of the hydraulic shovel is very sharp as compared with a passenger car and the like. However, as shown in
FIG. 4
, there is an allowance in the engine horsepower, and an average load rate with respect to the maximum horsepower of the engine in one cycle is about 80%, and the average load rate of the engine when measured with a day's operation including traveling, waiting for damp vehicles and the like is about 60%. When the operation by “the heavy load mode” is performed, the average load rate does not become 100% because of a load change. Specifically, in a hydraulic shovel equipped with the engine having output power corresponding to the maximum required horsepower, the output power that the engine can produce cannot be effectively used.
As an art of eliminating the disadvantage, so-called hybrid construction equipment disclosed in, for example, Japanese Patent Laid-open No. 10-103112, which includes an engine, a generator driven by the engine, a battery for charging electric power generated thereby, and an electric motor driven by the electric power of this battery, is proposed. Using
FIG. 5
, a hybrid hydraulic shovel in the above-described Japanese Patent Laid-open No. 10-103112 will be explained.
Pressure oil discharged from a variable displacement type of hydraulic pump
52
driven by an engine
51
is supplied to a hydraulic cylinder
54
a
for driving a working machine and a hydraulic motor
54
b
for driving to travel, via a control valve
53
. Pressure oil of an accumulator
56
held at fixed or higher pressure by pressure accumulation aiding means
55
is supplied to a hydraulic pump motor
58
for revolution via the control valve
57
. As a result, the hydraulic cylinder
54
a
, the hydraulic motor
54
b
and the hydraulic pump motor
58
are driven, which makes it possible to drive the working machine, make a lower traveling unit travel, and revolve an upper revolving superstructure. When revolution is braked, the hydraulic pump motor
58
is switched into a pump operation, and following the rotation of the hydraulic pump motor
58
, inertia energy is regenerated in the accumulator
56
as pressure energy.
The hydraulic pump
52
is equipped with a first electric motor
60
also serving as a generator, for which a controller
61
performs a switching control between a generating operation and an assisting operation and a torque control in each of them. Similarly, the hydraulic pump motor
58
is equipped with a second electric motor
62
also serving as a generator, for which a revolution controller
63
performs a switching control between a generating operation and an assisting operation and a torque control in each of them. A battery
64
is connected to the controller
61
and the revolution controller
63
, and it accumulates electric energy obtained from the generating operations of the first and second electric motors
60
and
62
and discharges electric energy necessary for the assisting operations of the first and second electric motors
60
and
62
.
The engine
51
the speed of which is governed by a governor
51
a
normally drives at a fixed engine speed. When an operation load is small, and absorption torque of the hydraulic pump
52
is smaller than output torque of the engine
51
, the controller
61
switches the first electric motor
60
into a generating operation, performs a torque control of the first electric motor
60
so as to generate electric power by surplus torque, and charges electric energy generated from the surplus torque in the battery
64
. When an operation load is large, and absorption torque of the hydraulic pump
52
is larger than output torque of the engine
51
, the controller
61
switches the first electric motor
60
into an assisting operation, and performs a torque control of the first electric motor
60
so as to generate an amount of shortage of torque from discharge energy from the battery
64
.
Based on a command value by a revolution operating lever
65
and a detection value by a rotation sensor
66
, the revolution controller
63
performs (1) a torque control of the second electric motor
62
so as to carry out an assisting operation for speeding-up rotation during a motor operation of the hydraulic pump motor
58
, or (2) a torque control of a generating operation of the second electric motor
62
so as to convert inertia energy exceeding a capacity of the accumulator
56
and regenerate it during a pump operation of the hydraulic pump motor
58
.
According to the above-described constitution, power generation is carried out by surplus torque of the engine
51
when an operation load is small, thus making it possible to effectively use the engine
51
, and energy regeneration is carried out at the time of braking revolution. When the operation load is large, absorption torque of the hydraulic pump
52
is increased by the assisting operation by discharge from the battery
64
, and therefore an operation can be carried out with larger absorption torque than the maximum generation torque of the engine
51
. Specifically, the engine
51
can be effectively used while energy conservation is achieved.
However, in the art disclosed in the above-described Laid-open Patent, the hydraulic pump motor
58
for revolution is driven by pressure oil supply from the accumulator
56
, and therefore a hydraulic circuit including the pressure accumulation assisting means
55
(for example, an electric motor and a hydraulic pump), the control valve
57
and the accumulator
56
, which makes a system complicated. Further, since part of energy generated by the engine
51

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