Prime-mover dynamo plants – Electric control – Starting and generating dynamo
Reexamination Certificate
2001-03-15
2002-09-24
Waks, Joseph (Department: 2834)
Prime-mover dynamo plants
Electric control
Starting and generating dynamo
C192S04100R
Reexamination Certificate
active
06455946
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an alternating-current generating apparatus for an automotive vehicle comprising an alternator which is driven by an internal combustion engine via a one-way clutch.
Conventionally, from the view point of global environmental protection, reduction of emission gas and reduction of fuel consumption are essential targets to be attained. When driving, automotive vehicles are often in idling conditions where the engine does not contribute to drive. In view of the above, there is a tendency that the engine rotational speed in this idling condition (hereinafter referred to as idling speed) is set to a relatively low value. However, reducing the idling speed will encounter with the difficulty in stabilizing the engine rotation due to increase of friction. This problem is remarkable in the diesel engines. Furthermore, long-term cyclic fluctuation of the engine rotation will appear due to delay caused in the control system of the internal combustion engine.
The low idling speed condition causing undesirable fluctuation in the engine rotation may be referred to as an idle hunting state.
FIG. 4
shows the behavior of the automotive alternator in such a low idling speed condition.
It is now assumed that, in the idle hunting state, the engine rotational speed is decreasing. In this case, the rotational speed of the automotive alternator reduces correspondingly with reducing engine speed. However, under a condition that the automotive alternator is working for a constant electric load, a required driving torque of the automotive alternator increases with reducing engine speed. As a result, the increased driving torque of the automotive alternator will undesirably promote the reduction of the engine speed. On the contrary, when the engine speed is increasing, the required driving torque of the automotive alternator decreases with increasing engine speed. As a result, the decreased driving torque of the automotive alternator will undesirably promote the increase of the engine speed.
To solve the above-described troublesome hunting promotion appearing in the engine rotational speed of this kind of automotive alternator, the published Japanese patent No. 7-72585 discloses a one-way clutch disposed in a driving pulley of the alternator. The one-way clutch equipped pulley operates in the following manner.
When the rotational speed of the internal combustion engine is decreasing (i.e., in a deceleration condition), large-small relationship between an inertia torque of the alternator and an output torque generated from the engine torque is inversed momentarily. In this case, the one-way clutch is brought into a disengaged state so that the degree of engine speed reduction can be suppressed. The undesirable fluctuation of engine rotation can be suppressed correspondingly.
However, the research and tests conducted by the inventor of this application have revealed that the above-described one-way clutch equipped pulley does not bring satisfactory effects in the suppression of engine rotational fluctuation appearing in the automotive alternator.
Hereinafter, the problem of the one-way clutch equipped automotive alternator will be explained in more detail with reference to FIG.
7
.
An external wheel
33
of a one-way clutch is entrained by a crank pulley (not shown) via a belt. A clutch portion, comprising sprag and roller members and a spring member (which are not shown), selectively engages or disengages an internal wheel
31
and the external wheel
33
.
A driving torque &tgr;
1
of the internal combustion engine acts on the external wheel
33
. A driving torque &tgr;
2
of the automotive alternator, which is referred to as power generation torque, acts on the internal wheel
31
in a direction opposed to the engine driving torque &tgr;
1
. Furthermore, inertial of an alternator rotor causes an inertial torque &tgr;
3
which also acts on the internal wheel
31
. The inertial torque &tgr;
3
changes its direction in accordance with change of rotation of the internal wheel
31
. The direction of the inertial torque &tgr;
3
is identical with that of the alternator driving torque &tgr;
2
when the rotational speed of the internal wheel
31
is increasing and is opposed when decreasing. Engagement and disengagement of the one-way clutch is designed so as to be determined according to the large and small relationship among these three torques.
The directions of torques &tgr;
1
, &tgr;
2
, and &tgr;
3
shown in
FIG. 7
are now assumed to be positive, while &ohgr;
1
represents the rotational speed of the internal wheel
31
and &ohgr;
2
represents the rotational speed of the external wheel
33
. The one-way clutch is engaged when &tgr;
1
≧&tgr;
3
−&tgr;
2
(where &ohgr;
1
=&ohgr;
2
) and is disengaged when &tgr;
1
<&tgr;
3
−&tgr;
2
.
At a moment the engine speed starts decreasing from accelerating or constant speed rotation, the torque &tgr;
1
decreases correspondingly. In this case, the inertial torque &tgr;
3
of the automotive alternator will exceed the engine driving torques &tgr;
1
which acts in the same direction as that of the inertial torque &tgr;
3
. The above condition &tgr;
1
<&tgr;
3
−&tgr;
2
is established. Thus, the one-way clutch is disengaged.
Subsequently, the rotational speed of the automotive alternator decreases due to power generation torque &tgr;
2
as well as friction loss at the bearing portion and wind loss at the cooling fan.
When the rotational speed of the automotive alternator starts decreasing, the above-described power generation torque &tgr;
2
increases correspondingly. This will forcibly and promptly decrease the rotational speed of the alternator. The composite torque acting on the internal wheel
31
will soon be equalized with the torque acting on the external wheel
33
. Thus, the one-way clutch is engaged shortly.
According to recent compact high power automotive alternators, the power generation torque &tgr;
2
is larger than the inertia torque &tgr;
3
during the disengaged state of the one-way clutch. Therefore, the rotational speed of the alternator rotor decreases quickly and the one-way clutch is again engaged within a short period of time after the one-way clutch is once disengaged, even when the engine speed is decreasing or in the very beginning of acceleration from its lowest rotational speed (where the increasing rate of the rotational speed is small).
As a result, the above-described conventional automotive alternator cannot bring satisfactory effect, although the one-way clutch is intentionally provided to release the internal combustion engine from the load torque of the automotive alternator when the internal combustion engine is decreasing.
Increasing the inertia mass of the automotive alternator is effective to solve the above-described problem since the rotational speed of the automotive alternator will not decrease so quickly. However, increased size and weight of the automotive alternator will induce another problem to be solved.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the prior art, the present invention has an object to provide an alternating-current generating apparatus for an automotive vehicle which is capable of adequately suppressing the fluctuation of engine speed without increasing the size and weight of a one-way clutch equipped automotive alternator installed on an internal combustion engine.
To accomplish the above and other related objects, the present invention provides an alternating-current generating apparatus for an automotive vehicle comprising a one-way clutch, an automotive alternator driven by an internal combustion engine via the one-way clutch, and control means for controlling a power generation amount of the automotive alternator. A detecting means is provided for detecting a rotational speed of either the internal combustion engine or the automotive alternator as well as an electric amount relating to a on-off state of the one-way clutch. The control means performs at least one of two power controls
Denso Corporation
Waks Joseph
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