Valve timing control apparatus for internal combustion engine

Details Valve timing control apparatus for internal combustion engine Valve timing control apparatus for internal combustion engine

2001-06-25

2003-02-11

Denion, Thomas (Department: 3748)

Internal-combustion engines

Poppet valve operating mechanism

With means for varying timing

C123S090160, C123S090170, C123S090180, C123S090120, C123S090310

Reexamination Certificate

active

06516759

ABSTRACT:

This application is based on Application No. 2001-025747, filed in Japan on Feb. 1, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the valve timing control apparatus for an internal combustion engine for controlling the opening and/or closing timing of intake valves and/or exhaust valves of the internal combustion engine.
2. Description of the Related Art
In a valve timing control apparatus in which cam angles representative of the rotational positions of cams mounted on camshafts, respectively, for operating intake valves and exhaust valves are controlled to retard or advance with respect to the crank angle of a crankshaft of an internal combustion engine, it has been known in the past that when the amount of actual advanced angle is moving toward the amount of target advanced angle by more than a prescribed value, the calculation of an integral value is controlled to stop.
First, such known valve timing control will be described below.
FIG. 2
is an explanatory view illustrating the phase shift range of a known valve timing control apparatus for an internal combustion engine represented by the relation between the amount of valve lift and the crank angle position of the crankshaft. In addition,
FIGS. 4 through 6
are perspective views illustrating the internal structure, at a maximum retarded angle position, a locked position and a maximum advanced angle position, respectively, of a valve actuator provided with a variable valve timing mechanism (hereinafter referred to as a VVT mechanism) for individually varying the valve timing (i.e., opening or closing timing) of each of the intake valves and exhaust valves.
The valve timing is variable between a curve indicated by an alternate long and short dash line and another curve indicated by a broken line, as illustrated in FIG.
2
. Such a variable range of the valve timing is determined by an operable or movable range of vanes
152
of the valve actuator within a housing
151
, as illustrated in
FIG. 4
to FIG.
6
.
FIG. 4
is a maximum retarded angle position of the vanes
152
relative to the housing
151
, and
FIG. 6
is a maximum advanced angle position thereof. The actuator is mounted on the camshaft for making the cam angle (i.e., the rotational position of the camshaft) variable relative to the crank angle (i.e., the rotational position of the crankshaft).
Next, a basic operation of this known valve timing control apparatus will be described according to flow charts of
FIGS. 17 and 18
and a timing chart of FIG.
19
.
FIG. 17
illustrates a flow chart relating to the operation of the prior art. In
FIG. 17
, first in step
1701
, the amount of an actual advanced angle VTd is detected from outputs of a cam angle sensor, which detects the cam angle of the camshaft, and a crank angle sensor, which detects the crank angle of the crankshaft. Then in step
1702
, a proper target valve timing, i.e., the amount of a target advanced angle VTt suitable for engine operating conditions, is calculated. In step
1703
, the actual advanced angle amount VTd is subtracted from the target advanced angle amount VTt to provide a control deviation VTe.
Subsequently, in step
1704
, the control deviation VTe is multiplied by a proportional gain Pgain to provide a proportional value Ip. In step
1705
, a difference between the current control deviation VTe and the last control deviation VTe(i−1) is multiplied by a derivative gain Dgain to provide a derivative value Id. In step
1706
, an integral value Ii is calculated.
The calculation of the integral value Ii is performed according to the flow chart of FIG.
18
. That is, first in step
1801
, when an absolute value |VTe| of the control deviation VTe is greater than an absolute value |VTe(i−1)| of the last control deviation VTe(i−1), it is determined that the actual advanced angle amount VTd does not follow the target advanced angle amount VTt. Then, in step
1802
, the integral value Ii is added by the result of multiplication of the control deviation VTe and the integral gain Igain to provide an updated integral value Ii . Otherwise, when the absolute value |VTe| of the control deviation is less than the absolute value of the last deviation |VTe(i−1)| in step
1801
, nothing is done so the integral value Ii is not updated and the last value is maintained as it is.
Returning to
FIG. 17
, in step
1707
, it is determined whether the absolute value |VTe| of the control deviation is equal to or less than a reference value VTh for determination of whether the actual advanced angle amount is in a steady state. When it is determined that the absolute value |VTe| is greater than the reference value VTh, then in step
1708
, an output current value Iout is calculated by adding a holding current learned value Ih, the proportional value Ip, the derivative value Id, and the integral value Ii together. When it is determined in step
1707
that the absolute value |VTe| is less than the reference value VTh, the holding current learned value Ih and the integral value Ii are added to each other to provide an output current value Iout.
Thereafter in step
1710
, the output current value Iout is converted into a corresponding duty value, which are output to oil control valves (OCVs). The oil control valves (OCVs) cooperate with an oil pump to constitute a hydraulic pressure supply system for controlling the oil pressure of each valve actuator to adjust the phase or angle of each corresponding cam and hence camshaft. The OCVs are represented by reference numerals
19
and
20
in
FIG. 1
which will be later used to explain the present invention in detail. The internal structure of one of the OCVs is illustrated in
FIGS. 7 through 9
for controlling the current to be supplied to a coil
193
thereby to perform the switching of oil pressure by the OCV.
Next, an actual operation of the above-mentioned known valve timing control apparatus will be described according to the timing chart of FIG.
19
.
FIG. 19
illustrates changes in the actual advanced angle amount VTd, the target advanced angle amount VTt, the output current value Iout and the integral value Ii. The target advanced angle amount VTt changes to the maximum advanced angle position at a time point
1901
. Since a deviation between the target advanced angle amount VTt and the actual advanced angle amount VTd continues to be large until at a time point
1902
, the OCV is controlled by the output current value Iout calculated by the operational expression at the time point
1708
of FIG.
17
. At the time point
1902
, the actual advanced angle VTd cannot follow the target advanced angle amount VTt. However, the VVT actuator is in a state fixed to the most or maximum advanced angle side, and hence it cannot be moved toward the advanced angle side any further. As a result, there still remains the deviation between the actual advanced angle amount VTd and the target advanced angle amount VTt.
From the time point
1902
to a time point
1903
, the actual advanced angle amount VTd does not follow the target advanced angle amount VTt, so the integral value Ii is updated in a direction to increase. From the time point
1903
to a time point
1904
, the integral value Ii is fixed to a preset upper limit integral value and exists in a state unable to increase any more. When the target advanced angle amount VTt changes to the retarded angle side at the time point
1904
, the VVT actuator is controlled by the output current value Iout calculated in step
1708
of FIG.
16
. However, since the integral value Ii was updated by mistake to an increasing side with the target advanced angle amount VTt being at the maximum advanced angle position, the actual advanced angle amount VTd cannot follow the target advanced angle amount VTt from the time point
1904
to the time point
1905
, thus reducing the response.
Moreover, for example, J

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