Internal-combustion engines – Starting device – Having fluid-driven starting motor
Reexamination Certificate
2002-04-17
2003-09-09
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Starting device
Having fluid-driven starting motor
C074S00700R, C074S00700R, C060S626000
Reexamination Certificate
active
06615786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a starter system for an internal combustion engine, for starting the engine by a hydraulic actuator driven by hydraulic pressure.
2. Description of the Prior Art
Conventionally, a starter system of this kind has been proposed e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 2001-82202.
FIG. 12
schematically shows the arrangement of the starter system. This starter system
350
, which is a hydraulic motor-driven type, is comprised of an electric motor
351
, an oil pump
352
driven by the electric motor
351
, an accumulator
353
for storing hydraulic pressure boosted by the oil pump
352
, a hydraulic motor
355
connected to the accumulator
353
via an oil passage
354
, and a solenoid valve
356
arranged in the oil passage
354
. A drive shaft
355
a
of the hydraulic motor
355
is connected to a drive shaft
359
a
of a timing pulley
359
via a reduction gear
357
and a one-way clutch
358
. The timing pulley
359
is connected to a timing pulley
362
of an internal combustion engine (hereinafter referred to as “the engine”)
361
via a synchronous timing belt
360
. Further, the timing pulley
362
is mounted to one end of a crankshaft
363
.
According to the above construction, when the engine
361
is started, the solenoid valve
356
opens the oil passage
354
, whereby hydraulic pressure is supplied from the accumulator
353
to the hydraulic motor
355
to drive the same for rotation. Then, the rotation of the hydraulic motor
355
is transmitted to the crankshaft
363
via the reduction gear
357
, the one-way clutch
358
and the synchronous timing belt
360
to thereby start the engine
361
. During operation of the engine
361
after the start thereof, transmission of torque from the crankshaft
363
to the hydraulic motor
355
is inhibited by action of the one-way clutch
358
.
In general, if an engine stops halfway in a compression stroke when the operation of the engine is stopped or when the start of the same has failed, the crankshaft of the engine can be urged by pressure of the compressed air to rotate reversely to a stable position. In this case, since the direction of torque is reversed from the normal direction thereof, the one-way clutch
358
of the above starter system
350
transmits reverse torque to the hydraulic motor
355
. This causes the hydraulic motor
355
to rotate in the reverse direction to act as a hydraulic pump. On the other hand, the oil passage
354
is held in a closed state by the solenoid valve
356
except when the engine is started. As a result, the hydraulic fluid pressurized to a high pressure level when the operation of the engine is stopped flows into the closed portion of the oil passage
354
between the hydraulic motor
355
and the solenoid valve
356
, thereby developing high impact pressure within the oil passage
354
. The high impact pressure causes the drive shaft
355
a
of the hydraulic motor
355
to generate large impact torque which can adversely affect a torque-transmitting system including the hydraulic motor
355
and the one-way clutch
358
as well as a hydraulic circuit system including the solenoid valve
356
and the oil passage
354
. Similarly, when the start of the engine has failed, although the oil passage
54
is held open by the solenoid valve
356
, high impact pressure can be generated e.g. due to a pressure loss in the solenoid valve
356
.
Further, another starter system of the above-mentioned kind has been proposed e.g. by Japanese Laid-Open Utility Model Publication (Kokai) No. 59-73579. This starter system includes an electric motor, and a hydraulic motor, and is capable of starting an engine by selectively using the two motors. The electric motor has a pinion gear splined to a rotational shaft thereof. At the start of the engine, a plunging mechanism causes the pinion gear to axially slide toward the engine, for meshing engagement with a ring gear integrally formed with a crankshaft of the engine. On the other hand, the hydraulic motor is arranged on an opposite side to the pinion gear with respect to the electric motor, and serially connected to the electric motor via a one-way clutch arranged coaxially with the rotational shaft of the hydraulic motor. The hydraulic motor is driven by hydraulic pressure accumulated within the accumulator. The operation or stoppage of the hydraulic motor is controlled according to the hydraulic pressure accumulated in the accumulator, by opening and closing of a solenoid valve arranged between the accumulator and the hydraulic motor. The pressure accumulation is carried out by utilizing regenerative energy under conditions that the hydraulic pressure within the accumulator is equal to or lower than a predetermined value and that the vehicle is decelerating.
According to this starter system, when the engine is started, the pinion of the electric motor is brought into meshing engagement with the ring gear by the plunging mechanism, and when the hydraulic pressure within the accumulator is equal to or higher than the predetermined value, the hydraulic motor is driven. As a result, torque of the hydraulic motor is transmitted to the rotational shaft of the electric motor via the one-way clutch, and then further transmitted from the pinion gear to the ring rear, whereby the engine is started. On the other hand, when the hydraulic pressure within the accumulator is lower than the predetermined value, the hydraulic motor is stopped, and the electric motor is driven to start the engine. In this case, the electric motor and the hydraulic motor are disconnected from each other by the one-way clutch, which prevents the hydraulic motor from applying rotational load to the electric motor.
Normally, the hydraulic motor and the electric motor have respective different torque characteristics. More specifically, the hydraulic motor provides larger output torque than the electric motor, and the rise of rotational speed of the hydraulic motor is more rapid than that of the electric motor. Therefore, the hydraulic motor is characterized by being capable of starting the engine quickly. The quick starting of the engine is advantageous in reducing a time period during which the pinion gear and the ring gear are engaged with each other, thereby suppressing generation of noise due to the engagement between the two gears, as well as in ensuring smooth startability when the engine is frequently stopped and started by application of “idle stop” e.g. in traffic congestion. The “idle stop” is an engine operation control technique for stopping the operation of the engine when the engine speed is low under predetermined operating conditions of the engine including a fully warmed-up condition thereof. This technique has come to be increasingly valued as measures of environmental protection and fuel economy.
However, in the above conventional starter system, since the hydraulic motor is serially connected to the rotational shaft of the electric motor, when the engine is to be started by the electric motor, transmission of torque from the electric motor to the hydraulic motor is inhibited by free or idle rotation of the one-way clutch, whereas when the engine is to be started by the hydraulic motor, the torque of the hydraulic motor is transmitted to the electric motor via the one-way clutch, whereby the electric motor is caused to rotate at the same rotational speed as the hydraulic motor. This makes a brush in constant contact with the rotational shaft of the electric motor prone to wear or abrasion. This wear of the brush is particularly conspicuous when the high torque characteristic of the hydraulic motor is utilized for restarting the engine in an idle stop mode, so as to start the engine quickly, because the starting rotational speed of the engine is higher than when the electric motor is used. As the brush wears to a larger degree, the rotational resistance due to friction is increased, whereby transmission efficiency in transmitting torque from the hydraulic motor to the engine is
Fushimi Koichi
Mori Ryuichi
Tachikawa Junya
Arent Fox Kintner & Plotkin & Kahn, PLLC
Castro Arnold
Honda Giken Kogyo Kabushiki Kaisha
Yuen Henry C.
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