Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2002-04-11
2004-02-10
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C701S108000, C123S568230
Reexamination Certificate
active
06688294
ABSTRACT:
TECHNICAL FIELD
This invention relates to an apparatus for controlling an Exhaust Gas Recirculation (hereinafter referred to as EGR) valve which is disposed in an exhaust gas recirculation system.
BACKGROUND ART
FIG. 1
is a schematic arrangement diagram in which a control valve
11
serving as an EGR valve is disposed in an exhaust gas recirculation passage c which communicates an exhaust passage “a” of an engine E and an intake passage b together. In such an apparatus for controlling the EGR valve, the driving of a direct current (DC) motor (hereinafter referred to as electric motor M) is controlled by an engine controller unit (hereinafter referred to as ECU)
51
. The opening and closing of the control valve
11
is controlled by the electric motor M. By controlling the electric motor M, the opening degree of the control valve
11
can be adjusted.
Incidentally, in the conventional apparatus for controlling the EGR valve, a predetermined return torque is given to the control valve
11
in the valve-closing direction by an urging means, and a motor torque to vary the control valve
11
in the valve-opening direction is given by the driving of the electric motor M in the valve-opening direction. The control valve
11
is thus opened and closed by the balance of these torque.
As this kind of control apparatus, a description is made for example in JP-A 11-159405(1999) about an arrangement which is provided with: an open loop control system which controls the above-described electric motor M in an open loop manner so as to generate a motor torque depending on a target opening-closing position of the above-described control valve
11
; and a feedback control system which controls the electric motor M in a feedback manner based on a deviation between input data corresponding to a targeted opening-closing position of the control valve
11
and detected data of the present opening-closing position of the control valve
11
.
A description is first given of the driving method using this electric motor M. In case the opening degree of the control valve
11
is feedback-controlled by the electric motor M, the generated torque of the electric motor M is continuously controlled by feeding back the opening degree of the control valve
11
through continuous detection thereof with a position sensor such as of a sliding resistor type. Thus, the resolution of the adjusting opening degree of the control valve
11
can be infinitely minimized in theory.
The apparatus for controlling the EGR valve using this kind of electric motor M employs a so-called torque balance system. By a spring as an urging means, a predetermined return torque in the valve-closing direction is given and, by driving the electric motor M in the valve-opening direction, a variable motor torque in the valve-opening direction is given. Based on these torque balance, the valve-opening position is determined.
In this kind of control apparatus, since the EGR valve is constantly given the return torque, the opening-closing position (shift amount) varies with the inclination of lines A, B having a hysteresis due to friction as shown in FIG.
2
.
Here, line A represents an operating characteristic at the time of opening the control valve
11
by increasing the motor torque, and line B represents an operating characteristic at the time of closing the control valve
11
by decreasing the motor torque. Depending on the spring constant of the spring to give the return torque, the inclination of the operating characteristics A, B change and, depending on the magnitude of the set torque, the operating characteristics A, B shift to right and left in FIG.
2
.
Now, in order to control the control valve
11
with this kind of operating characteristics, suppose that there is employed a method in which the electric motor M is subject to a proportional (P) integral (I) control based on a deviation between the input data corresponding to the target opening-closing position of the control valve
11
and the detected data of the present opening-closing position of the control valve. In this case, from the relationship of the operating characteristics A, B as shown in
FIG. 2
, it becomes difficult to stabilize the control valve
11
in the target opening position.
In other words, in order to open the control valve
11
to the target opening position by increasing the motor torque, the motor torque is increased in order to perform the control along the operating characteristic A in FIG.
2
. In this kind of control, in case the valve-opening position has exceeded the target value under the influence of an inertia, interference, or the like, the driving direction is reversed. However, if the hysteresis is present, the movement will not be reversed immediately, but will give rise to a delay. Should the P gain and the I gain be set without considering the delay due to hysteresis, vibrations will occur as shown in FIG.
3
. Therefore, if no correction is made to the hysteresis, the P gain and the I gain are restricted, resulting in impairing of the response.
Considering the above-described situation, a description is now given, with reference to
FIGS. 4 and 5
, about an apparatus for controlling the control valve
11
in a so-called torque balance drive system using the electric motor M. In
FIG. 4
, reference numeral
1
denotes a valve body having formed therein a passage which forms a part of an exhaust gas recirculation passage c interposed in a recirculation system of the exhaust gas. By an upward movement of the control valve
11
(as illustrated) to thereby contact a valve seat
12
, the exhaust gas recirculation passage c is closed and, by a downward movement of the control valve
11
to thereby depart from the valve seat
12
, the exhaust gas recirculation passage c is opened.
Reference numeral
2
denotes a motor case for housing therein an electric motor M. In the electric motor M, reference numeral
21
denotes a rotor around which is wound by a coil
22
, and reference numeral
23
denotes a yoke provided with a magnet
24
. The lower end portion of the rotor
21
is rotatably supported on the valve body
1
by a bearing
27
.
Inside the rotor
21
, there is threadedly engaged a motor shaft
31
. The motor shaft
31
is prevented from relatively rotating by a guide bush
13
on the body
1
. Therefore, it follows that the motor shaft
31
moves upward and downward depending on the amount of rotation of the rotor
21
. A valve shaft
14
is provided in contact with the lower end of the motor shaft
31
, and an intermediate portion of the valve shaft
14
is guided by a guide seal
15
and a guide plate
16
so as to be movable upward and downward. The control valve
11
is attached to the lower end of the valve shaft
14
.
Reference numeral
17
denotes a guide seal cover. Between a spring sheet
18
mounted on the upper end of the valve shaft
14
and the guide plate
16
, there is interposed a return spring
19
for urging the valve shaft
14
in an upward direction, i.e., for urging the control valve
11
in a valve-closing direction.
The control valve
11
constituted as described above is driven by a torque balance system as described above. In other words, the control valve
11
is given a predetermined return torque in the valve-closing direction of the control valve
11
by the return spring
19
serving as the urging means, and is also given a variable motor torque in the valve-opening direction by the driving of the electric motor M. By the balance of these torque, the open/close of the control valve
11
is controlled.
FIG. 5
is a circuit block diagram showing an engine controller unit (ECU)
51
which supplies the electric motor M with a driving signal. Reference numeral
50
denotes a control part in the form of a microcomputer which determines the driving force of the electric motor M. Reference numeral
52
denotes a battery. Reference numeral
53
denotes a motor driving force converting part which converts the output of the control part
50
for supplying to the electric motor M, and is made up of: a Zener diode
53
a
Fujita Youichi
Kawamura Satoshi
Miyake Toshihiko
Miyoshi Sotsuo
Castro Arnold
Yuen Henry C.
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