Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2000-08-22
2001-10-16
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C318S696000, C251S129110
Reexamination Certificate
active
06302090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve device and valve control method. The valve is mounted in an engine system and reduces the concentration of exhaust gases by recirculating engine exhaust gases to the engine combustion chamber.
2. Description of the Related Art
FIG. 1
shows an engine system mounting a conventional Valve device. In the figure, reference numeral
1
denotes an air cleaner which removes particulate matter contained in external air and transfers such air to an air intake
3
.
2
is an injector which injects fuel (for example gasoline) into the air intake
3
.
3
is an air intake which supplies a gaseous mixture and fuel to the engine
5
.
4
is a throttle valve which regulates the amount of the gaseous mixture supplied to the engine
5
.
5
is an engine of an automobile which transmits drive force to the drive system by the combustion of the gaseous mixture.
5
a
is a combustion chamber of the engine
5
,
5
b
is an intake valve closing the communication of the combustion chamber
5
a
with the air intake
3
,
5
c
is an exhaust valve which closes the communication of the combustion chamber
5
a
and the exhaust outlet
6
,
5
d
is a piston which displaces vertically in the combustion chamber
5
a.
6
is an exhaust outlet which exhausts a gaseous mixture (exhaust gas) which has been combusted in the engine
5
.
7
is a purification device which allows emission of exhaust gases to the atmosphere after their purification.
8
is a re-circulation pipe which circulates a part of the exhaust gases exhausted from the engine
5
to the engine combustion chamber
5
a.
9
is an EGR valve which is disposed in the re-circulation pipe
8
and which is a valve device which regulates an re-circulated amount of exhaust gases.
10
is a control unit which controls the aperture of the EGR valve
9
in response to an operational state of the vehicle.
FIG. 2
is a cross sectional view of a conventional valve device (EGR valve). In the FIG.,
11
is a housing of an EGR valve
9
,
12
is a through passage connected with the re-circulation pipe
8
on the exhaust outlet
6
side.
13
is a through passage connected with the re-circulation pipe
8
on the air intake
3
side.
14
is a valve disposed between the through passage
12
and the through passage
13
.
14
a
is an abutting member which abuts with the valve
14
.
15
is a valve rod which supports the valve
14
.
16
is a spring support member,
17
is a spring which compresses the valve rod
15
upwardly.
18
is a step motor which displaces the drive rod
19
vertically when regulating the aperture of the valve
14
.
19
is a drive rod which displaces a valve rod
15
upwardly together with the rotation of the step motor
18
.
The operation of the invention will be described below.
When the engine
5
receives a gaseous mixture of fuel and air from the air intake
3
, drive force is transmitted to the drive system by the reciprocal motion of the piston
5
d
by combustion of the gaseous mixture. Exhaust gases which result from the combustion of the gaseous mixture are output to the exhaust outlet
6
from the combustion chamber
5
a.
The majority of the exhaust gases are emitted into the atmosphere after purification by the purification device
7
. In order to reduce the concentration of the exhaust gases, a part of the exhaust gases is re-circulated to the combustion chamber
5
a
of the engine
5
through the re-circulation pipe
8
.
The amount of re-circulation of exhaust gases re-circulated to the combustion chamber
5
a
of the engine
5
is regulated by the EGR valve
9
disposed in the re-circulation pipe
8
and depends on an operational condition of the vehicle.
Hereafter control of the re-circulated amount of exhaust gases by the EGR valve
9
will be described.
Firstly when the engine is stopped, the valve rod
15
and the drive rod
19
are in an opposed state. Although the valve rod
15
does not receive a downward depressing force from the drive rod
19
, since an upward force is applied by the spring
17
, the valve rod
15
abuts with the abutting member
14
a
and the re-circulation of the exhaust gases is stopped.
On the other hand, when the engine
5
is started in order to regulate an amount of engine exhaust gases balanced with the vehicle operational condition, the control unit
10
controls the aperture of the valve
14
in the EGR valve
9
by outputting a valve lift control signal (a valve signal which commands the opening or closing of the valve
14
) to the EGR valve
9
based on the temperature of the engine coolant, the engine rotation speed, the injection pump aperture and the like.
For example, when the EGR valve
9
receives a pulse signal for opening the valve
14
, the coil of the step motor
18
is excited and the step motor is rotated in a direction in which the drive rod
19
is depressed. In order for the step motor
18
to maintain a large drive torque, the excitation mode of the step motor
18
adopts a 2-phase excitation.
In this way, when the drive rod
19
is depressed and abuts with the valve rod
15
, the valve rod
15
is depressed downwardly, the valve
14
of the EGR valve
9
is opened and the re-circulation of exhaust gases commences.
When the re-circulation amount of exhaust gases is balanced with the operational conditions of the vehicle, that is to say, when the aperture of the valve
14
equals a target value, a valve lift control signal (a pulse signal which commands the opening of the valve
14
) received from the control unit
10
is terminated. When a pulse signal commanding the closure of the valve
14
is repeated, the aperture of the valve
14
approaches a target value and the rotation of the step motor is terminated.
The step motor
18
is required to maintain a fixed aperture in the valve
14
by resisting the pressing force of the spring
17
even when rotation is terminated (hereafter referred to as “not driven”). Thus the coils remain in an excited state (2-phase) with a continuous electricity supply (when the motor is driven, the supply of electricity is interrupted when receiving a pulse signal).
Since the conventional valve device is constructed as above, as the coils of the step motor
18
must be excited even when the step motor
18
is not driven and thus the excitation of the coils requires constant supply of electricity, the calorific value and electricity consumption of the coils is greater when the step motor is not driven than when the step motor is driven. Thus cost increases are incurred by the necessity to provide heat resistance with respect to high calorific values while the step motor is not driven. (In particular, when high-speed operation is required, the coil may be operated at low resistance and thus there is a tendency for temperature differentials between driven and non-driven periods to be great).
SUMMARY OF THE INVENTION
The present invention is proposed to solve the above problems and has the object of providing a valve device and valve control method which can suppress electricity consumption and calorific values in coils when a step motor is not driven.
The valve device of the present invention comprises an aperture regulation means which regulates an aperture of a valve by exciting a 2-phase motor which drives the valve on receiving a valve drive command and a switching means which switches a 2-phase excitation mode to 1-phase excitation when a fixed time elapses after the completion of aperture regulation by the aperture regulation means.
In this way, since it is possible to suppress calorific values and consumption of electricity in the coil when the step motor is not driven, it is possible to avoid cost increases due to restrictions imposed by heat resistance contingencies.
The valve control method of the present invention comprises the steps of regulating an aperture of a valve by exciting a 2-phase motor which drives the valve on receiving a valve drive command and switching the motor from 2-phase to 1-phase when a fixed time elapses after the complet
Kawamura Satoshi
Miyake Toshihiko
Miyoshi Sotsuo
Yokoyama Hisashi
Castro Arnold
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
Yuen Henry C.
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