Valve timing control device for use in an internal...

Details Valve timing control device for use in an internal... Valve timing control device for use in an internal...

2000-03-20

2001-04-10

Lo, Weilun (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090170

Reexamination Certificate

active

06213069

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine having a variable valve timing mechanism (hereinafter simply referred to as VVT) that variably controls the open/close timing (hereinafter simply referred to as valve timing) of an intake valve and an exhaust valve of the internal combustion engine in response to the operating state of an engine, and more particularly to a valve timing control device for controlling the operation of the VVT in its abnormal state.
2. Description of the Related Art
A conventional valve timing control device for use in an internal combustion engine includes, as shown in
FIG. 9
, an oil pump
1
for forcedly feeding a lubricating oil to a valve timing control system, a cam shaft
2
that is coupled to a crank shaft (not shown) of an engine by means of a power transmission mechanism such as a timing belt and is driven to rotate in synchronism with the rotation of the crank shaft to cause the intake valve and the exhaust valve to open and close through a valve operating mechanism, and a variable valve timing control hydraulic actuator
3
(hereinafter simply referred to as “VVT actuator”) for varying the rotational phase of the cam shaft with respect to the crankshaft. The conventional valve timing control device also includes an oil control valve
4
for adjusting the amount of lubricating oil in the form of an operating oil supplied to the VVT actuator
3
, a crank angle detector
5
for detecting the rotational phase of the crank shaft, a cam angle detector
6
for detecting the rotational phase of the cam shaft, and an engine operating state detector
7
for detecting the operating state of the internal combustion engine. The conventional valve timing control device further includes an oil control valve control circuit
8
that electrically drives the oil control valve
4
, an electronic control unit (ECU)
10
that gives an instruction or command to the oil control valve control circuit
8
, an oil temperature detector
14
for detecting the temperature of the lubricating oil supplied to the oil control valve
4
, and a hydraulic pressure detector
15
for detecting the hydraulic pressure of the lubricating oil.
Subsequently,. the operation of the above-described conventional valve timing control device will be described. The ECU
10
calculates the current open/close timing (hereinafter simply referred to as “valve timing”) of the intake and exhaust valves on the basis of an output of the engine operating state detector
7
that detects the operating state of the internal combustion engine. The ECU
10
calculates the operating amount of the oil control valve
4
in accordance with the hydraulic pressure of the lubricating oil so as to reduce a deviation between an optimum valve timing and the current valve timing, and outputs an instruction or command to the oil control valve control circuit
8
. The oil control valve control circuit
8
adjusts the supply voltage or current to the oil control valve
4
so that the operating amount instructed by the ECU
10
and the electric behavior of the oil control valve
4
coincide with each other.
The lubricating oil forcedly fed from the oil pump
1
is controlled by the oil control valve
4
and then supplied to any one of a spark retarding chamber
3
a
and a valve timing advancing chamber
3
b
of the VVT actuator
3
by an appropriate amount in a desired direction. On the other hand, the lubricating oil, filled in the other chamber to which the lubricating oil is now not being supplied, is returned to an oil pan
12
through a drain
11
of the oil control valve
4
.
When the oil is supplied to the spark retarding chamber
3
a
or to the valve timing advancing chamber
3
b
of the VVT actuator
3
, a rotor
3
c
within the VVT actuator
3
is driven to rotate in a direction toward a valve timing advancing side or a spark retarding side due to hydraulic pressure. The cam shaft
2
is coaxially connected to the rotor
3
c
, and the rotation of the rotor
3
c
allows the rotational phase of the cam shaft
2
to vary with respect to the rotational phase of the crank shaft to thereby change the valve timing.
Subsequently, a control method or operation of the control device or ECU
10
that estimates the drive force of the VVT actuator
3
on the basis of the operating state of the engine and controls the valve timing in response to the drive force will be described with reference to a flowchart shown in FIG.
10
.
First, the ECU
10
reads various sensor signals from the operating state detector
7
, the crank angle detector
5
that detects the rotational phase of the crank angle and the cam angle detector
6
that detects the rotational phase of the cam shaft
2
(step S
1
), and calculates the current valve timing &thgr; from the rotational phase of the crank angle and the rotational phase of the cam shaft
2
thus read (step S
2
).
Also, in step S
3
, an optimal valve timing &thgr;T (hereinafter referred to as “target valve timing”) in the engine operating state is calculated from the sensor signals (for example, the number of revolutions per minute (rpm) or rotational speed of the engine, the throttle opening degree, the charging efficiency, the temperature of an engine coolant or cooling water, etc.) indicative of the engine operating state as read in step S
1
.
In addition, the ECU
10
reads an oil temperature from the oil temperature detector for detecting the temperature of the lubricating oil (hereinafter referred to as “oil temperature”) and estimates the viscosity of the lubricating oil from the oil temperature thus read in (step S
4
).
Subsequently, in step S
5
, the ECU
10
calculates a deviation &thgr;e of the current valve timing with respect to the target valve timing and estimates a force (hereinafter referred to as “an operating force Fc of the cam shaft
2
”) necessary for operating the cam shaft
2
in order to set the deviation &thgr;e to zero, from the viscosity of the lubricating oil as estimated in step S
4
and the rotational speed (rpm) of the engine.
In step S
6
, the hydraulic pressure is read from the hydraulic pressure detector
15
that detects the supply pressure of the lubricating oil (hereinafter referred to as “hydraulic pressure”) and then a cam shaft drive force Fp for driving the cam shaft
2
to rotate is determined from the hydraulic pressure supplied to the VVT actuator
3
, to thereby estimate a force (hereinafter referred to as “ACT drive force Fa”) by which the VVT actuator
3
changes the rotational phase of the cam shaft
2
with respect to the rotational phase of the crank shaft, where Fa=Fp−Fc.
In step S
7
, the operation of opening (when |&thgr;e|>&thgr;D) or closing (when |&thgr;e|≧&thgr;D) of the oil control valve
4
is determined on the basis of the relation in magnitude between the deviation &thgr;e and a dead zone &thgr;D. The dead zone &thgr;D may b set to “0”.
Then, In step S
8
, the operating amount for opening the oil control valve
4
is determined. The operating amount is determined on the basis of the deviation &thgr;e calculated in step S
5
and the ACT drive force Fa estimated in step S
6
. For example, if PID control is applied in the determination of the operating amount, respective gains are set in accordance with the ACT drive force Fa.
In step S
9
, the operating amount for closing the oil control valve
4
is determined through the same operation as in step S
8
.
In step S
10
, the operating amount determined in step S
8
or S
9
is converted into an electric signal by means of the oil control valve control circuit
8
to thereby drives the oil control valve
4
.
In the control device that estimates the ACT drive force Fa and controls the valve timing in response to the ACT drive force Fa as described above, the operating amount of the oil control valve
4
is determined by multiplying the deviation between the target valve timing advancing amount and the actual valve timing advancing amount by a control gain which is

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