U.S. patent application number 11/988502 was filed with the patent office on 2010-03-11 for variable valve operating apparatus.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Toshiyuki Maehara.
Application Number | 20100059006 11/988502 |
Document ID | / |
Family ID | 37899604 |
Filed Date | 2010-03-11 |
United States Patent
Application |
20100059006 |
Kind Code |
A1 |
Maehara; Toshiyuki |
March 11, 2010 |
Variable Valve Operating Apparatus
Abstract
The present invention relates to a variable valve operating
apparatus having a switching mechanism for switching between a dual
valve variable control mode and a single valve variable control
mode, and enhances the durability of the switching mechanism. In an
idle state prevailing before a vehicle starts moving, the operating
state of an internal combustion engine is in a single valve small
lift region (point A). In this instance, the single valve variable
control mode prevails. After the vehicle starts moving, the
operating state changes from point A through point B to point C and
switches to a dual valve great lift region. Subsequently, when an
accelerator pedal is released with a clutch disengaged for
upshifting, the operating state reverts to point A in the single
valve small lift region. In the above situation, as the operating
state remains in the dual valve great lift region for a short
period of time, a switch to the dual valve variable control mode
does not constitute a considerable advantage. Therefore, the switch
to the dual valve variable control mode is prohibited when the
operating state changes from point B to point C.
Inventors: |
Maehara; Toshiyuki;
(Susono-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
|
Family ID: |
37899604 |
Appl. No.: |
11/988502 |
Filed: |
September 22, 2006 |
PCT Filed: |
September 22, 2006 |
PCT NO: |
PCT/JP2006/318829 |
371 Date: |
January 9, 2008 |
Current U.S.
Class: |
123/90.17 |
Current CPC
Class: |
F01L 1/267 20130101;
F01L 1/053 20130101; F01L 13/0021 20130101; F01L 1/185 20130101;
F01L 1/2405 20130101 |
Class at
Publication: |
123/90.17 |
International
Class: |
F01L 1/34 20060101
F01L001/34 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2005 |
JP |
2005-281115 |
Claims
1-7. (canceled)
8. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; storage means for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; normal control means for causing the switching mechanism
to perform a switching operation in accordance with the rules; and
disable means which, when the operating state of the internal
combustion engine is changed from the dual valve variable control
region to the single valve variable control region or vice versa
within a predetermined period of time after a gear shift by a
transmission positioned between the internal combustion engine and
vehicle driving wheels, avoids the switching operation by disabling
the switching operation in anticipation that the operating state
will revert to the previous region within a short period of
time.
9. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; storage means for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; normal control means for causing the switching mechanism
to perform a switching operation in accordance with the rules;
condition judgment means for judging, when the operating state of
the internal combustion engine switches from the dual valve
variable control region to the single valve variable control region
or vice versa, whether a predefined condition is established for
anticipating that the operating state will revert to the previous
region within a short period of time; disable means for disabling
the switching operation when the predefined condition is
established; and enable means which, if the operating state of the
internal combustion engine does not revert to a previous region
within a predetermined period of time after a switch from the dual
valve variable control region to the single valve variable control
region or vice versa, enables the switching operation no matter
whether the predefined condition is established.
10. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; storage means for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; normal control means for causing the switching mechanism
to perform a switching operation in accordance with the rules;
condition judgment means for judging, when the operating state of
the internal combustion engine switches from the dual valve
variable control region to the single valve variable control region
or vice versa, whether a predefined condition is established for
anticipating that the operating state will revert to the previous
region within a short period of time; disable means for disabling
the switching operation when the predefined condition is
established; measurement means for measuring the number of times
the switching operation was disabled or the cumulative time during
which the switching operation was disabled; and permission means
which, when a predetermined value is exceeded by the number of
times the switching operation was disabled or the cumulative time
during which the switching operation was disabled, permits the
switching mechanism to perform a switching operation no matter
whether the predefined condition is established.
11. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; storage means for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; normal control means for causing the switching mechanism
to perform a switching operation in accordance with the rules;
condition judgment means for judging, when the operating state of
the internal combustion engine switches from the dual valve
variable control region to the single valve variable control region
or vice versa, whether a predefined condition is established for
anticipating that the operating state will revert to the previous
region within a short period of time; disable means for disabling
the switching operation when the predefined condition is
established; and valve opening amount limitation means for limiting
a target valve opening amount when the switching operation is
disabled by the disable means.
12. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; a storage device for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; a normal control device for causing the switching
mechanism to perform a switching operation in accordance with the
rules; and a disable device which, when the operating state of the
internal combustion engine is changed from the dual valve variable
control region to the single valve variable control region or vice
versa within a predetermined period of time after a gear shift by a
transmission positioned between the internal combustion engine and
vehicle driving wheels, avoids the switching operation by disabling
the switching operation in anticipation that the operating state
will revert to the previous region within a short period of
time.
13. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; a storage device for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; a normal control device for causing the switching
mechanism to perform a switching operation in accordance with the
rules; a condition judgment device for judging, when the operating
state of the internal combustion engine switches from the dual
valve variable control region to the single valve variable control
region or vice versa, whether a predefined condition is established
for anticipating that the operating state will revert to the
previous region within a short period of time; a disable device for
disabling the switching operation when the predefined condition is
established; and an enable device which, if the operating state of
the internal combustion engine does not revert to a previous region
within a predetermined period of time after a switch from the dual
valve variable control region to the single valve variable control
region or vice versa, enables the switching operation no matter
whether the predefined condition is established.
14. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; a storage device for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; a normal control device for causing the switching
mechanism to perform a switching operation in accordance with the
rules; a condition judgment device for judging, when the operating
state of the internal combustion engine switches from the dual
valve variable control region to the single valve variable control
region or vice versa, whether a predefined condition is established
for anticipating that the operating state will revert to the
previous region within a short period of time; a disable device for
disabling the switching operation when the predefined condition is
established; a measurement device for measuring the number of times
the switching operation was disabled or the cumulative time during
which the switching operation was disabled; and a permission device
which, when a predetermined value is exceeded by the number of
times the switching operation was disabled or the cumulative time
during which the switching operation was disabled, permits the
switching mechanism to perform a switching operation no matter
whether the predefined condition is established.
15. A variable valve operating apparatus comprising: a valve
mechanism having a switching mechanism for switching between a dual
valve variable control mode in which the valve opening amounts of a
first valve and a second valve, which are provided for the same
cylinder and of the same type, are varied continuously or in
multiple steps and a single valve variable control mode in which
the valve opening amount of the first valve is varied continuously
or in multiple steps with the valve opening amount of the second
valve fixed; a storage device for storing rules for dividing an
operating region of an internal combustion engine into a dual valve
variable control region, for which the dual valve variable control
mode should be selected, and a single valve variable control
region, for which the single valve variable control mode should be
selected; a normal control device for causing the switching
mechanism to perform a switching operation in accordance with the
rules; a condition judgment device for judging, when the operating
state of the internal combustion engine switches from the dual
valve variable control region to the single valve variable control
region or vice versa, whether a predefined condition is established
for anticipating that the operating state will revert to the
previous region within a short period of time; a disable device for
disabling the switching operation when the predefined condition is
established; and a valve opening amount limitation device for
limiting a target valve opening amount when the switching operation
is disabled by the disable device.
Description
TECHNICAL FIELD
[0001] The present invention relates to a variable valve operating
apparatus, and more particularly to a variable valve operating
apparatus that is capable of mechanically changing a valve opening
amount.
BACKGROUND ART
[0002] It is known that a conventional variable valve operating
apparatus described, for instance, in Patent Document 1
mechanically changes the lift amount and operating angle of a valve
in accordance with the operating state of an internal combustion
engine.
[0003] In the variable valve operating apparatus described in
Patent Document 1, two rotary cams are installed over a camshaft.
Two intake valves are provided for a single cylinder. A first
intake valve is opened and closed by a first rotary cam. A second
intake valve is opened and closed by a second rotary cam. A
variable valve transmission mechanism, which includes a four-joint
link mechanism, is positioned between the first rotary cam and the
first intake valve and between the second rotary cam and the second
intake valve.
[0004] The four-joint link mechanism of the above variable valve
operating apparatus includes an input arm, which has an input
section that abuts against the rotary cams; a transmission arm,
which is swingably coupled to the input arm; a swing arm, which is
swingably coupled to the transmission arm, can swing on a rotation
control shaft, and receives driving force from the rotary cams and
transmits it to an output section that opens/closes the intake
valves; and a control arm, which rotates on the rotation control
shaft and is swingably coupled to the input arm. The operating
angles and lift amounts of the intake valves can be mechanically
changed by controlling the posture of the four-joint link mechanism
to change the positional relationship between the rotary cams and
input section.
[0005] Further, the above variable valve operating apparatus
includes a coupling mechanism for coupling a first link mechanism,
which is a four-joint link mechanism related to the first intake
valve, to a second link mechanism, which is a four-joint link
mechanism related to the second intake valve, and a mechanism for
keeping the posture of the second link mechanism at the time of
uncoupling so as to maximize the operating angle of the second
intake valve. The coupling mechanism includes a through-hole, which
is made in the control arm of each four-joint link mechanism, and a
coupling pin, which is to be inserted into the through-hole. The
mechanism for keeping the posture of the second link mechanism at
the time of uncoupling includes a through-hole made in a fixed
plate, a through-hole made in a second control arm (the control arm
for the second link mechanism), and the aforementioned coupling
pin.
[0006] The coupling pin is constantly inserted in the through-hole
in the second control arm, and can move toward a first control arm,
which is the control arm for the first link mechanism, or toward
the fixed plate while being inserted in the through-hole in the
second control arm. When the coupling pin moves toward the first
control arm and goes into the through-hole in the first control
arm, the second control arm is coupled to the first control arm via
the coupling pin. When the control arms are coupled together, the
first and second link mechanisms maintain the same posture. In this
instance, control is exercised so that the valve opening amounts of
the first and second valves are equal.
[0007] When, on the contrary, the coupling pin moves toward the
fixed plate and goes into the through-hole in the fixed plate, the
second control arm is coupled to the fixed plate via the coupling
pin. When the second control arm is coupled to the fixed plate, the
second link mechanism maintains a predetermined posture. In this
instance, when the posture of the first link mechanism is
controlled to change the positional relationship between the rotary
cams and input section, only the valve opening amount of the first
valve can be mechanically changed while the valve opening amount of
the second valve is fixed.
[0008] In other words, the above variable valve operating apparatus
can select a mode in which the first and second intake valves have
the same valve opening amount or a mode in which the first and
second intake valves differ in the valve opening amount. The valve
opening amounts, particularly the lift amounts, of the first and
second intake valves can then be made different from each other.
Since this gives rise to different intake flow rates, a swirl flow
can be created within a combustion chamber to assure increased
combustion stability in the combustion chamber.
[0009] Patent Document 1: Japanese Patent Laid-open No.
2004-100555
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0010] As implied above, the above variable valve operating
apparatus can choose between a dual valve variable control mode in
which the valve opening amounts of the first and second intake
valves are varied and a single valve variable control mode in which
only the valve opening amount of the first intake valve is varied
with the valve opening amount of the second intake valve fixed.
When switching from the dual valve variable control mode to the
single valve variable control moved, it is necessary to perform two
operations, that is, extract the coupling pin from the pin hole in
the first control arm and insert the coupling pin into the pin hole
in the fixed plate. When, on the other hand, switching from the
single valve variable control mode to the dual valve variable
control mode, it is necessary to perform two operations, that is,
extract the coupling pin from the pin hole in the fixed plate and
insert the coupling pin into the pin hole in the first control
arm.
[0011] The internal combustion engine described above switches
between the dual and single valve variable control modes in
accordance with the operating state. In a low engine speed/low load
region, for instance, the single valve variable control mode is
selected because it is demanded that a swirl be created within a
cylinder to provide combustion improvement. In a high engine
speed/high load region, on the other hand, the dual valve variable
control mode is selected because it is demanded that a large amount
of air be taken in. More specifically, a control device for the
internal combustion engine stores rules for dividing an operating
region into a dual valve variable control region, for which the
dual valve variable control mode should be selected, and a single
valve variable control region, for which the single valve variable
control mode should be selected. When the operating state of the
internal combustion engine shifts from one region to another, the
control device switches between the dual and single valve variable
control modes accordingly.
[0012] However, if the control device frequently switches between
the dual and single valve variable control modes, it is likely that
the durability of a switching mechanism will be adversely affected
due to premature wear of the aforementioned coupling pin and pin
hole, which constitute the switching mechanism. Further, such
frequent switching might result in switching failure. If switching
failure should occur, proper valve opening characteristics will not
be obtained. This results in the failure to obtain expected fuel
efficiency and driveability.
[0013] The present invention has been made in view of the above
circumstances. An object of the present invention is to provide a
variable valve operating apparatus that includes a switching
mechanism for switching between the dual and single valve variable
control modes and improves the durability of the switching
mechanism.
ADVANTAGES OF THE INVENTION
Means for Solving the Problem
[0014] First aspect of the present invention is a variable valve
operating apparatus comprising:
[0015] a valve mechanism having a switching mechanism for switching
between a dual valve variable control mode in which the valve
opening amounts of a first valve and a second valve, which are
provided for the same cylinder and of the same type, are varied
continuously or in multiple steps and a single valve variable
control mode in which the valve opening amount of the first valve
is varied continuously or in multiple steps with the valve opening
amount of the second valve fixed;
[0016] storage means for storing rules for dividing an operating
region of an internal combustion engine into a dual valve variable
control region, for which the dual valve variable control mode
should be selected, and a single valve variable control region, for
which the single valve variable control mode should be
selected;
[0017] normal control means for causing the switching mechanism to
perform a switching operation in accordance with the rules;
[0018] condition judgment means for judging, when the operating
state of the internal combustion engine switches from the dual
valve variable control region to the single valve variable control
region or vice versa, whether a predefined condition is established
for anticipating that the operating state will revert to the
previous region within a short period of time; and
[0019] disable means for disabling the switching operation when the
predefined condition is established.
[0020] Second aspect of the present invention is the variable valve
operating apparatus according to the first aspect, wherein the
predefined condition denotes a condition where a predetermined
period of time has not elapsed since a gear shift by a transmission
positioned between the internal combustion engine and vehicle
driving wheels.
[0021] Third aspect of the present invention is the variable valve
operating apparatus according to the first aspect, wherein the
predefined condition denotes a condition where a transmission
positioned between the internal combustion engine and vehicle
driving wheels is shifted to neutral or park.
[0022] Fourth aspect of the present invention is the variable valve
operating apparatus according to any one of the first to the third
aspects, further comprising:
[0023] enable means for enabling the switching operation if the
operating state of the internal combustion engine does not revert
to a previous region within a predetermined period of time after a
switch from the dual valve variable control region to the single
valve variable control region or vice versa.
[0024] Fifth aspect of the present invention is the variable valve
operating apparatus according to any one of the first to the fourth
aspects, further comprising:
[0025] measurement means for measuring the number of times the
switching operation was disabled or the cumulative time during
which the switching operation was disabled; and
[0026] permission means which, when a predetermined value is
exceeded by the number of times the switching operation was
disabled or the cumulative time during which the switching
operation was disabled, permits the switching mechanism to perform
a switching operation no matter whether the predefined condition is
established.
[0027] Sixth aspect of the present invention is the variable valve
operating apparatus according to any one of the first to the fifth
aspect, further comprising:
[0028] valve opening amount limitation means for limiting a target
valve opening amount when the switching operation is disabled by
the disable means.
[0029] Seventh aspect of the present invention is the variable
valve operating apparatus according to the sixth aspect,
[0030] wherein the valve mechanism includes a main cam, which
drives both the first valve and the second valve in the dual valve
variable control mode and drives only the first valve in the single
valve variable control mode; and a sub-cam, which drives the second
valve in the single valve variable control mode; and
[0031] wherein the valve opening amount limitation means limits the
target valve opening amount so as to keep the sub-cam from leaving
a mating member for the sub-cam when the disable means disables a
switch from the single valve variable control mode to the dual
valve variable control mode to maintain the single valve variable
control mode.
EFFECTS OF THE INVENTION
[0032] According to the first aspect of the present invention, the
switching mechanism can switch between the dual valve variable
control mode and single valve variable control mode. This switching
operation is performed in accordance with rules for dividing the
operating region of the internal combustion engine into the dual
valve variable control region and single valve variable control
region depending on the operating state of the internal combustion
engine. However, the switching operation is disabled if, when the
operating state switches from the dual valve variable control
region to the single valve variable control region or vice versa, a
predefined condition is established for anticipating that the
operating state will revert to the previous region within a short
period of time. Therefore, the first aspect of the present
invention makes it possible to reduce the frequency of switching
operation by avoiding unnecessary switching operations.
Consequently, the durability of the switching mechanism can be
increased by avoiding undue wear and scratching of the switching
mechanism. Further, the possibility of switching failure can be
reduced to constantly implement valve opening characteristics
according to the operating state and properly obtain satisfactory
fuel efficiency characteristics, exhaust characteristics, and
driveability.
[0033] According to the second aspect of the present invention, it
is possible to absolutely avoid an unnecessary switching operation
that is likely to take place immediately after gear shifting by the
transmission. Therefore, the frequency of switching operation can
be reduced while the vehicle is moving.
[0034] According to the third aspect of the present invention, it
is possible to absolutely avoid an unnecessary switching operation
during a free acceleration (so-called racing) operation, which is
performed while the transmission is in neutral or parking position.
Therefore, the frequency of switching operation can be reduced
during free acceleration.
[0035] If the operating state of the internal combustion engine
does not revert to a previous region within a short period of time
after it is changed from the dual valve variable control region to
the single valve variable control region or vice versa, the fourth
aspect of the present invention can enable the switching operation
and perform the switching operation. Therefore, if the switching
operation is actually needed in a situation where it is assumed
that no switching operation is needed, the switching operation can
be performed to implement preferred valve opening
characteristics.
[0036] When a predetermined value is exceeded by the number of
times the switching operation was disabled or the cumulative time
during which the switching operation was disabled, the fifth aspect
of the present invention can perform the switching operation even
in a situation where a condition for anticipating that the
switching operation is unnecessary is established. Therefore, the
switching operation can be performed in any situation with
frequency required for maintaining the function of the switching
mechanism. This makes it possible to avoid problems, for instance,
by preventing the switching mechanism from binding due to long-term
inactivity.
[0037] When the operation for switching between the dual valve
variable control mode and single valve variable control mode is
disabled, the sixth aspect of the present invention can limit the
target valve opening amount. This makes it possible to absolutely
avoid noise and other problems that may arise when the switching
operation is disabled.
[0038] When the operation for switching from the single valve
variable control mode to the dual valve variable control mode is
disabled to maintain the single valve variable control mode in a
situation where the valve mechanism includes the main cam, which
drives both the first valve and the second valve in the dual valve
variable control mode and drives only the first valve in the single
valve variable control mode, and the sub-cam, which drives the
second valve in the single valve variable control mode, the seventh
aspect of the present invention can limit the target valve opening
amount so that the sub-cam does not leave its mating member. Since
this feature absolutely prevents the sub-cam from leaving the
mating member and coming back into contact (colliding) with it, it
is possible to absolutely avoid noise generation from collision and
prevent the surfaces of the sub-cam and its mating member from
being damaged.
BRIEF DESCRIPTION OF DRAWINGS
[0039] FIG. 1 illustrates the configuration of a system that
includes a variable valve operating apparatus according to a first
embodiment of the present invention.
[0040] FIG. 2 is a perspective view illustrating the configuration
of a valve mechanism included in the variable valve operating
apparatus according to the first embodiment of the present
invention.
[0041] FIG. 3 illustrates the configuration of a variable valve
mechanism included in the valve mechanism shown in FIG. 2.
[0042] FIG. 4 is an exploded perspective view illustrating variable
valve mechanisms and fixed valve mechanism shown in FIG. 2.
[0043] FIG. 5 is a schematic diagram illustrating the configuration
of a hydraulic system for operating a switching pin.
[0044] FIG. 6 shows a map for switching between a dual valve
variable control mode and a single valve variable control mode.
[0045] FIG. 7 shows a map for switching between the dual valve
variable control mode and the single valve variable control
mode.
[0046] FIG. 8 is a flowchart illustrating a routine that is
executed by the first embodiment of the present invention.
[0047] FIG. 9 is a flowchart illustrating a routine that is
executed by a second embodiment of the present invention.
[0048] FIG. 10 is a flowchart illustrating a routine that is
executed by a third embodiment of the present invention.
[0049] FIG. 11 shows valve lift curves of a first intake valve and
a second intake valve.
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment
System Configuration
[0050] FIG. 1 illustrates the configuration of a system that
includes a variable valve operating apparatus according to a first
embodiment of the present invention. The system shown according to
the first embodiment includes an internal combustion engine 1,
which is mounted in a vehicle as a driving source. The internal
combustion engine 1 includes a plurality of cylinders 2. FIG. 1
shows only one of the plurality of cylinders 2.
[0051] The internal combustion engine 1 also includes a cylinder
block 4. The cylinder block 4 houses a piston 3 within a cylinder.
The piston 3 is connected to a crankshaft 5 via a connecting rod. A
crank angle sensor 6 is installed near the crankshaft 5. The crank
angle sensor 6 is configured to detect the rotation angle of the
crankshaft 5.
[0052] A cylinder head 8 is attached to the top of the cylinder
block 4. A combustion chamber 10 is formed by the space between the
upper surface of the piston 3 and the cylinder head 8. The cylinder
head 8 is provided with an ignition plug 11, which ignites an
air-fuel mixture in the combustion chamber 10.
[0053] The cylinder head 8 has an intake port 12 that communicates
with the combustion chamber 10. The joint between the intake port
12 and combustion chamber 10 is provided with an intake valve 14. A
valve mechanism 18 is installed between the intake valve 14 and an
intake cam 16 on an intake camshaft 15. The valve mechanism 18 will
be described in detail later.
[0054] The intake port 12 is connected to an intake path 19. An
injector 20 is installed near the intake port 12 to inject fuel
into the intake port 12. A surge tank 21 is positioned in the
middle of the intake path 19.
[0055] A throttle valve 22 is installed upstream of the surge tank
21. The throttle valve 22 is an electronically-controlled valve
that is driven by a throttle motor 23. The throttle valve 22 is
driven in accordance with an accelerator opening AA, which is
detected by an accelerator opening sensor 24. A throttle opening
sensor 25 is installed near the throttle valve 22. The throttle
opening sensor 25 is configured to detect a throttle opening TA. An
air flow meter 26 is installed upstream of the throttle valve 22.
The air flow meter 26 is configured to detect an intake air amount
Ga. An air cleaner 27 is installed upstream of the air flow meter
26.
[0056] Further, the cylinder head 8 has an exhaust port 28 that
communicates with the combustion chamber 10. The joint between the
exhaust port 28 and combustion chamber 10 is provided with an
exhaust valve 29. The exhaust port 28 is connected to an exhaust
path 30. An air-fuel ratio sensor 31 is installed in the exhaust
path 30 to detect an exhaust air-fuel ratio.
[0057] The system according to the present embodiment also includes
an ECU (Electronic Control Unit) 60 as a control device. The output
end of the ECU 60 is connected, for instance, to a discharge valve
84 (see FIG. 5), which will be described later, in addition to the
ignition plug 11, valve mechanism 18, injector 20, and throttle
motor 23. The input end of the ECU 60 is connected, for instance,
to the crank angle sensor 6, throttle opening sensor 25,
accelerator opening sensor 24, air flow meter 26, and air-fuel
ratio sensor 31. In accordance with outputs generated by the
sensors, the ECU 60 exercises control over the entire internal
combustion engine such as fuel injection control and ignition
timing control.
[0058] A transmission (not shown) is positioned between the
internal combustion engine 1 and driving wheels of the vehicle. The
ECU 60 is also connected to a shift position sensor 62, which
detects the position to which the transmission is shifted. The
transmission may be of either a manual type or an automatic
type.
[Configuration of Variable Valve Train]
[0059] FIG. 2 is a perspective view illustrating the configuration
of the valve mechanism 18 included in the variable valve operating
apparatus according to the present embodiment.
[0060] As shown in FIG. 2, the intake camshaft 15 has two intake
cams (a first intake cam 16 and a second intake cam 17) for each
cylinder. Two intake valves (a first intake valve 14L and a second
intake valve 14R) are positioned so that the first intake valve 14L
and the second intake valve 14R are left-right symmetrical with
respect to the first intake cam 16. Variable valve mechanisms 40L,
40R, which coordinate the lifting motions of the intake valves 14L,
14R with the rotary motion of the first intake cam 16, are
respectively positioned between the first intake cam 16 and the
intake valves 14L, 14R. Meanwhile, the second intake cam 17 is
positioned so that the second intake valve 14R is sandwiched
between the second intake cam 17 and the first intake cam 16. A
fixed valve mechanism 70 is positioned between the second intake
cam 17 and the second intake valve 14R to coordinate the lifting
motion of the second intake valve 14R with the rotary motion of the
second intake cam 17. The valve mechanism 18 is configured to
select either the variable valve mechanism 40R or the fixed valve
mechanism 70 as a coordination destination for the lifting motion
of the second intake valve 14R.
(1) Detailed Configuration of Variable Valve Mechanism
[0061] FIG. 3 illustrates the configuration of a variable valve
mechanism 40 in the valve mechanism 18 shown in FIG. 2. More
specifically, FIG. 3 shows the variable valve mechanism 40 as
viewed in the axial direction of the intake camshaft 15. Since the
left- and right-hand variable valve mechanisms 40L, 40R are
basically symmetrical with respect to the first intake cam 16,
their configuration will be described without distinguishing
between the left- and right-hand variable valve mechanisms 40L,
40R. In this document and accompanying drawings, the term "variable
valve mechanism 40" is used when there is no need to distinguish
between the left- and right-hand variable valve mechanisms 40L,
40R. Similarly, the symbols L and R, which respectively indicate
left- and right-hand parts, are not attached to the names of the
component parts of the variable valve mechanisms 40L, 40R, the
intake valves 14L, 14R, and other symmetrically arranged parts
except when it is necessary to distinguish between them.
[0062] As shown in FIG. 3, the valve mechanism 18 includes a rocker
arm 35 that presses the intake valve 14 in the opening direction.
The variable valve mechanism 40 is positioned between the first
intake cam 16 and rocker arm 35. The variable valve mechanism 40 is
configured to continuously vary the coordination between the rotary
motion of the first intake cam 16 and the swing motion of the
rocker arm 35.
[0063] The variable valve mechanism 40 includes a control shaft 41
that is positioned in parallel with the intake camshaft 15. A
control arm 42 is fastened to the control shaft 41 with a bolt 43.
A part of the control arm 42 projects in the radial direction of
the control shaft 41. An intermediate arm 44 is mounted on the
projection of the control arm 42 with a pin 45. The pin 45 is
positioned eccentrically relative to the center of the control
shaft 41. Therefore, the intermediate arm 44 swings on the pin
45.
[0064] A swing cam arm 50 is swingably supported by the control
shaft 41. The swing cam arm 50 has a slide surface 50a, which faces
the first intake cam 16. The slide surface 50a is formed so as to
come into contact with a second roller 53. The slide surface 50a is
curved so that its distance to the first intake cam 16 gradually
decreases when the second roller 53 moves from the leading end of
the swing cam arm 50 toward the axial center of the control shaft
41. The swing cam arm 50 also has a swing cam surface 51, which is
positioned opposite the slide surface 50a. The swing cam surface 51
includes a nonoperating surface 51a and an operating surface 51b.
The nonoperating surface 51a is formed so that its distance from
the swing center of the swing cam arm 50 is fixed. The operating
surface 51b is formed so that its distance from the axial center of
the control shaft 41 increases with an increase in the distance to
the nonoperating surface 51a.
[0065] A first roller 52 and the second roller 53 are positioned
between the slide surface 50a and the circumferential surface of
the first intake cam 16. More specifically, the first roller 52 is
positioned so as to come into contact with the circumferential
surface of the first intake cam 16, whereas the second roller 53 is
positioned so as to come into contact with the slide surface 50a of
the swing cam arm 50. The first and second rollers 52, 53 are both
rotatably supported by a coupling shaft 54 that is fastened to the
leading end of the intermediate arm 44. Since the intermediate arm
44 swings on the pin 45, these rollers 52, 53 swing along the slide
surface 50a and the circumferential surface of the first intake cam
16 while maintaining a fixed distance from the pin 45.
[0066] Further, a spring seat 50b is formed on the swing cam arm
50. One end of a lost motion spring 38 is engaged with the spring
seat 50b. The other end of the lost motion spring 38 is fastened to
a stationary part of the internal combustion engine. The lost
motion spring 38 is a compression spring. The force received from
the lost motion spring 38 presses the slide surface 50a of the
swing cam arm 50 against the second roller 53 and the first roller
52 against the first intake cam 16. This positions the first and
second rollers 52, 53 so that they are sandwiched between the slide
surface 50a and the circumferential surface of the first intake cam
16.
[0067] The aforementioned rocker arm 35 is positioned below the
swing cam arm 50. A rocker roller 36 is attached to the rocker arm
35 so that the rocker roller 36 faces the swing cam surface 51. The
rocker roller 36 is rotatably mounted on the middle part of the
rocker arm 35. One end of the rocker arm 35 abuts against a valve
shaft 14a of the valve 14, and the other end of the rocker arm 35
is rotatably supported by a hydraulic lash adjuster 37. When a
lifting operation is conducted, a valve spring (not shown) pushes
the valve shaft 14a in a closing direction, that is, in a direction
of pushing up the rocker arm 35. The rocker roller 36 is pressed
against the swing cam surface 51 of the swing cam arm 50 by the
force of the valve spring and by the hydraulic lash adjuster
37.
[0068] According to the configuration of the variable valve
mechanism 40 described above, the pushing force of the first intake
cam 16 is transmitted to the slide surface 50a via the first and
second rollers 52, 53 as the first intake cam 16 rotates. When this
moves the contact between the swing cam surface 51 and rocker
roller 36 from the nonoperating surface 51a to the operating
surface 51b, the rocker arm 35 is pushed downward to open the valve
14.
[0069] Further, when the rotational position of the control shaft
41 changes, the configuration of the variable valve mechanism 40
changes the position of the second roller 53 on the slide surface
50a, thereby changing the swing range of the swing cam arm 50 for
lifting motion. More specifically, when the control shaft 41
rotates counterclockwise in FIG. 3, the position of the second
roller 53 on the slide surface 50a moves toward the leading end of
the swing cam arm 50. The rotation angle of the swing cam arm 50
that is required between the instant at which the swing cam arm 50
starts a swing motion upon receipt of pushing force from the first
intake cam 16 and the instant at which the rocker arm 35 actually
begins to be pushed then increases as the control shaft 41 rotates
counterclockwise in FIG. 3. In other words, the operating angle and
lift amount of the valve 14 can be decreased by rotating the
control shaft 41 counterclockwise in FIG. 3. On the contrary,
clockwise rotation of the control shaft 41 increases the operating
angle and lift amount of the valve 14.
[0070] As described above, the variable valve mechanism 40
according to the present embodiment varies both the operating angle
and lift amount of the valve 14. In this document, the operating
angle and lift amount are collectively referred to as a "valve
opening amount." It should be noted, however, that the variable
valve mechanism according to the present invention may
alternatively be configured to vary either the operating angle or
the lift amount.
(2) Detailed Configuration of Fixed Valve Mechanism
[0071] The configuration of the fixed valve mechanism 70 will now
be described in detail with reference to FIGS. 2 and 4. FIG. 4 is
an exploded perspective view illustrating the variable valve
mechanism 40 and fixed valve mechanism 70 shown in FIG. 2.
[0072] As shown in FIG. 2, the fixed valve mechanism 70 is
positioned between the second intake cam 17 and the second swing
cam arm 50R. The fixed valve mechanism 70 coordinates the swing
motion of the second swing cam arm 50R with the rotary motion of
the second intake cam 17. The fixed valve mechanism 70 includes a
great lift arm 71, which is driven by the second intake cam 17, and
an arm coupling mechanism 72 (see FIG. 4), which couples the great
lift arm 71 to the second swing cam arm 50R. The arm coupling
mechanism 72 includes a switching pin 74, a hydraulic chamber 75, a
pin hole 76, a return spring 77, and a piston 78, which will be
described later.
[0073] The great lift arm 71, which is mounted on the control shaft
41 and positioned next to the second swing cam arm 50R, can swing
independently of the second swing cam arm 50R. An input roller 73,
which comes into contact with the circumferential surface of the
second intake cam 17, is rotatably supported by the great lift arm
71.
[0074] As shown in FIG. 4, a spring seat 71a is formed on the great
lift arm 71. As is the case with the aforementioned swing cam arm
50, a lost motion spring (not shown) is engaged with the spring
seat 71a. The force of the lost motion spring presses the input
roller 73 against the circumferential surface of the second intake
cam 17.
[0075] The great lift arm 71 includes the switching pin 74, which
can be inserted into and extracted from the second swing cam arm
50R. The great lift arm 71 is provided with the hydraulic chamber
75, which has an opening that is positioned toward the second swing
cam arm 50R. The switching pin 74 is fitted into the hydraulic
chamber 75. The hydraulic chamber 75 is connected to a hydraulic
system that will be described later. When the hydraulic system
raises the hydraulic pressure in the hydraulic chamber 75, the
resulting hydraulic pressure pushes the switching pin 74 out of the
hydraulic chamber 75 and toward the second swing cam arm 50R.
[0076] Meanwhile, the second swing cam arm 50R is provided with the
pin hole 76, which has an opening that is positioned toward the
great lift arm 71. The switching pin 74 and pin hole 76 are
equidistant from the center of the control shaft 41. From bottom to
top, items placed in the pin hole 76 are the return spring 77 and
the piston 78 that serves as a lifter.
[0077] FIG. 5 is a schematic diagram illustrating the configuration
of the hydraulic system for operating the switching pin 74. As
shown in FIG. 5, an oil path 81 is formed in the control shaft 41.
The oil path 81 is connected to the hydraulic chamber 75, a sliding
gap between the control shaft 41 and the great lift arm 71, and a
sliding gap between the control shaft 41 and the second swing cam
arm 50R. The oil path 81 is also connected to a pump 82. A
discharge path 83 is connected to the middle of the oil path 81.
The discharge path 83 is provided with the discharge valve 84.
Further, an orifice 85 is installed downstream of the discharge
valve 84 in the discharge path 83.
[0078] Lubricating oil pressurized by the pump 82 is supplied to
the above sliding gaps through the oil path 81. Part of the
lubricating oil flowing in the oil path 81 is supplied to the
hydraulic chamber 75. Therefore, the hydraulic pressure in the
hydraulic chamber 75 can be raised. Meanwhile, opening the
discharge valve 84 discharges the lubricating oil from the
discharge path 83. This lowers the hydraulic pressure in the
hydraulic chamber 75. The switching pin 74 can be operated by
controlling the hydraulic pressure in the hydraulic chamber 75.
Features of First Embodiment
Single Valve Variable Control Mode
[0079] The great lift arm 71 constantly swings as it is driven by
the second intake cam 17. However, while the base circle of the
second intake cam 17 is in contact with the input roller 73, the
great lift arm 71 is momentarily stationary. The second swing cam
arm 50R also swings as it is driven by the first intake cam 16.
However, while the base circle of the first intake cam 16 is in
contact with the first roller 52, the second swing cam arm 50R is
momentarily stationary. The periods during which the great lift arm
71 and the second swing cam arm 50R are stationary overlap with
each other. In other words, there is a period during which the
great lift arm 71 and the second swing cam arm 50R are
simultaneously stationary.
[0080] The angle of the second swing cam arm 50R in the above
stationary state varies with the rotational position of the control
shaft 41. Therefore, there is a rotational position of the control
shaft 41 at which the switching pin 74 aligns with the pin hole 76
while the great lift arm 71 and the second swing cam arm 50R are
stationary. This rotational position of the control shaft 41 is
hereinafter referred to as the "pin switching position." In the
valve mechanism 18, the pin hole 76 aligns with the switching pin
74 when the rotational position of the control shaft 41 agrees with
the pin switching position. In this state, therefore, the arm
coupling mechanism 72 can perform a switching operation as
described below.
[0081] When the pin hole 76 aligns with the switching pin 74, the
switching pin 74 abuts against the piston 78. If, in this state,
the force exerted by the hydraulic pressure in the hydraulic
chamber 75 to push the switching pin 74 is greater than the force
exerted by the return spring 77 to push the piston 78, the
switching pin 74 enters the pin hole 76 to push the piston 78 all
the way into the pin hole 76. In other words, the switching pin 74
can be inserted into the pin hole 76 by allowing the hydraulic
system to raise the hydraulic pressure in the hydraulic chamber 75.
When the switching pin 74 is inserted into the pin hole 76, the
second swing cam arm 50R is coupled to the great lift arm 71. The
coordination destination for the lifting motion of the second
intake valve 14R then changes from the variable valve mechanism 20R
to the fixed valve mechanism 70.
[0082] In the above instance, the rotary motion of the intake
camshaft 15 is transmitted from the second intake cam 17 to the
second swing cam arm 50R via the great lift arm 71. The valve
opening amount of the second intake valve 14R is mechanically
determined by the shapes of the second intake cam 17, great lift
arm 71, and second swing cam arm 50R and the positional
relationship between them. It is constantly fixed as predetermined
(to provide a great lift and large operating angle) irrespective of
the rotational position of the control shaft 41. Meanwhile, the
first intake cam 16 transmits the rotary motion of the first intake
cam 16 to the first swing cam arm 50L via the first and second
rollers 52, 53L. Consequently, the valve opening amount of the
first intake valve 14L varies with the rotational position of the
control shaft 41.
[0083] In this document, a state in which the valve opening amount
of the first intake valve 14L varies with the rotational position
of the control shaft 41 while the valve opening amount of the
second intake valve 14R remains large as described above is
referred to as the "single valve variable control mode." In the
single valve variable control mode, it is possible to provide the
second intake valve 14R with a great lift and the first intake
valve 14L with a small lift. This causes the second intake valve
14R to flow a large amount of air to the cylinder and the first
intake valve 14L to flow a small amount of air to the cylinder. As
the air flow rates differ as mentioned above, a swirl flow can be
created within the cylinder. Creating the swirl flow provides
combustion improvement in a low engine speed/low load region.
(Dual Valve Variable Control Mode)
[0084] The switching pin 74 can be extracted from the pin hole 76
by lowering the hydraulic pressure in the hydraulic chamber 75 when
the pin hole 76 aligns with the switching pin 74. The great lift
arm 71 is then uncoupled from the second swing cam arm 50R. Thus,
the coordination destination for the lifting motion of the second
intake valve 14R can be changed from the fixed valve mechanism 70
to the variable valve mechanism 20R.
[0085] In the above instance, the rotary motion of the camshaft 15
is transmitted from the first intake cam 16 to the slide surfaces
50a of the first and second swing cam arms 50L, 50R via the first
and second rollers 52, 53. Therefore, the valve opening amounts of
the first and second intake valves 14L, 14R both vary in accordance
with the rotation of the control shaft 41. Consequently, the valve
opening amounts of the first and second intake valves 14L, 14R can
be both varied in accordance with the rotational position of the
control shaft 41. In this document, a state in which the valve
opening amounts of the first and second intake valves 14L, 14R are
both variable as described above is referred to as the "dual valve
variable control mode."
[0086] The ECU 60 switches between the dual valve variable control
mode and single valve variable control mode in accordance with the
operating state (more specifically, the engine speed NE and load)
of the internal combustion engine 1. FIG. 6 shows a switching map
that is stored in the ECU 60 and used for switching between the
dual valve variable control mode and single valve variable control
mode. This switching map shows an operating region of the internal
combustion engine 1 by indicating the engine speed NE along the
horizontal axis and the load along the vertical axis.
[0087] Here, the term "load" denotes an internal combustion engine
torque, load rate, accelerator opening AA, or other index
correlating to the load on the internal combustion engine 1. The
ECU 60 can calculate the value of the load in accordance with
outputs generated from the accelerator opening sensor 24, air flow
meter 26, and the like. Further, the ECU 60 can calculate the
engine speed NE in accordance with an output generated from the
crank angle sensor 6. In this manner, the ECU 60 can determine the
current operating state of the internal combustion engine 1 with
reference to the switching map.
[0088] In FIG. 6, a switching pin operating line P represents a
boundary for switching between the dual and single valve variable
control modes. Two circles positioned side by side represent the
first and second intake valves 14L, 14R, and the words within the
circles indicate whether the valve opening amount is large or
small.
[0089] As shown in FIG. 6, a region that is lower in engine speed
and lower in load than the switching pin operating line P is a
region of the single valve variable control mode. In the present
embodiment, this region is referred to as the "single valve small
lift region." The single valve small lift region provides a coupled
state in which the switching pin 74 of the arm coupling mechanism
72 is inserted into the pin hole 76.
[0090] On the other hand, a region that is higher in engine speed
and higher in load than the switching pin operating line P is a
region of the dual valve variable control mode. In the present
embodiment, this region is referred to as the "dual valve great
lift region." The dual valve great lift region provides an
uncoupled state in which the switching pin 74 of the arm coupling
mechanism 72 is extracted from the pin hole 76.
[0091] The ECU 60 usually switches between the single and dual
valve variable control modes in accordance with the switching map
described above. In general, unstable, incomplete combustion is
likely to result in a low engine speed/low load region. However,
the present embodiment can create a swirl for combustion
improvement by providing the second intake valve 14R with a great
lift and the first intake valve 14L with a small lift in the single
valve small lift region, which corresponds to a low engine
speed/low load region. This makes it possible to reduce fuel
consumption and exhaust emissions. In the dual valve great lift
region, which corresponds to a high engine speed/high load region,
on the other hand, the present embodiment can introduce an adequate
amount of air into the cylinder by providing both intake valves 14
with a great lift.
[0092] When the operating state of the internal combustion engine 1
changes from the single valve small lift region to the dual valve
great lift region, the ECU 60 usually switches to the dual valve
variable control mode by extracting the switching pin 74 from the
pin hole 76 without delay. However, it is conceivable that the ECU
60 may revert to the single valve small lift region within a short
period of time depending on the situation even when the operating
state changes from the single valve small lift region to the dual
valve great lift region.
[0093] The above situation may occur when, for instance, the
vehicle accelerates after it has started moving. Before the vehicle
starts moving, the internal combustion engine 1 is idling as
indicated by point A in FIG. 6. As the vehicle accelerates after
starting in first gear, the operating state changes from point A to
point B in FIG. 6 and then from point B to point C. Subsequently,
an accelerator pedal is released with a clutch disengaged to shift
up to second gear. Since this causes the internal combustion engine
1 to revert to an idling state, the operating state changes from
point C to point A.
[0094] Shifting up to third gear and then fourth gear brings about
the same changes as described above. In other words, when the
vehicle accelerates after it has started moving, the operating
state of the internal combustion engine 1 changes from point A
through point B, point C and then back to point A in FIG. 6 within
a relatively short period of time. If, in such an instance, the arm
coupling mechanism 72 immediately performs a switching operation in
accordance with the switching map shown in FIG. 6, the switching
pin 74 is extracted from the pin hole 76 when the operating state
changes from point B to point C, and then inserted back into the
pin hole 76 when the operating state changes from point C to point
A. It means that the dual valve variable control mode is maintained
for an extremely short period of time when the operating state
changes from point B through point C to point A. Therefore,
switching to the dual valve variable control mode does not
constitute a considerable advantage. Instead, such switching
constitutes a significant disadvantage. More specifically, frequent
insertion/extraction of the switching pin 74 may cause premature
wear and scratching of the switching pin 74 and pin hole 76.
Consequently, the present embodiment does not perform a switching
operation for the switching pin 74 in the above situation in
consideration of durability of the arm coupling mechanism 72.
[0095] The above switching operation, which should be avoided,
takes place due to gear shifting by the transmission. Therefore,
the present embodiment identifies and avoids a gear-shift-induced
switching operation by temporarily disabling the switching
operation of the arm coupling mechanism 72 during a predetermined
period of time after a gear shift by the transmission.
[0096] When the above process is performed, a switching operation
that is not absolutely necessary can be identified and avoided not
only when the vehicle accelerates after the start of moving but
also in the following situation. Points D to K in FIG. 7 indicate
operating state changes that occur when the vehicle begins to climb
a hill during high-speed running. In this situation, the operating
state of the internal combustion engine 1 changes as described
below. When the vehicle begins to run uphill, the vehicle velocity
gradually decreases due to grade resistance, thereby gradually
decreasing the engine speed NE (point D to point E). A driver of
the vehicle then shifts down for the purpose of recovering the
previous speed. When the accelerator pedal is released with the
clutch disengaged for downshifting, the internal combustion engine
1 changes toward an idle state (point E to point F). As the
accelerator pedal is depressed after downshifting, the internal
combustion engine 1 changes toward a high engine speed/high load
state (point F to point G). As acceleration continues, the engine
speed NE increases (point G to point H). When the vehicle velocity
is adequately recovered, the driver shifts up. When the accelerator
pedal is released with the clutch disengaged for upshifting, the
internal combustion engine 1 changes toward an idle state (point H
to point I). After upshifting, the engine speed NE drops below a
level prevailing before upshifting (point I to point J). A steady
operation then takes place in the newly selected gear (point J to
point K).
[0097] If, in the above situation, the arm coupling mechanism 72
immediately performs a switching operation in accordance with the
switching map shown in FIG. 7, the switching pin 74 is extracted
from the pin hole 76 when the operating state changes from point F
to point G, and after a short time, the switching pin 74 is
inserted back into the pin hole 76 when the operating state changes
from point H to point I. In this case, too, the dual valve variable
control mode persists for an extremely short period of time.
Therefore, switching to the dual valve variable control mode does
not constitute a considerable advantage. Instead, such switching
constitutes a significant disadvantage because it may cause
premature wear of the switching pin 74 and pin hole 76. It means
that the switching operation in the above case should also be
avoided. The present embodiment can refrain from performing the
above switching operation, which should be avoided, by detecting
the execution of a gear shift at point F and temporarily disabling
the switching operation of the arm coupling mechanism 72 for a
predetermined period of time after detection.
Details of Process Performed by First Embodiment
[0098] FIG. 8 is a flowchart illustrating a routine that the ECU 60
according to the present embodiment executes to implement the above
functionality. It is assumed that this routine is periodically
executed at predetermined time intervals. First of all, the routine
shown in FIG. 8 performs step 100 to judge whether a gear shift is
performed by the transmission. The shift position sensor 62 detects
whether a gear shift is performed. If the judgment result obtained
in step 100 indicates that no gear shift is performed, the routine
does not perform the following processing steps because it is not
necessary to disable the switching operation of the arm coupling
mechanism 72. In this instance, normal control is continuously
exercised so as to immediately switch between the single and dual
valve variable control modes in accordance with the switching
map.
[0099] If, on the other hand, the judgment result obtained in step
100 indicates that a gear shift is performed, step 102 is followed
to judge whether the operating state of the internal combustion
engine 1 has changed from the single valve small lift region to the
dual valve great lift region within a predetermined period of time
after the gear shift. The predetermined period of time is based,
for instance, on data obtained by examining the time required for a
change from point B through point C to point A in FIG. 6 and a
change from point F through point G, point H to point I in FIG. 7,
and stored in the ECU 60.
[0100] If the judgment result obtained in step 102 does not
indicate a change from the single valve small lift region to the
dual valve great lift region, it means that the arm coupling
mechanism 72 is not instructed to perform a switching operation. In
this instance, it is not necessary to disable the switching
operation; therefore, the routine continuously exercises normal
control without performing the following processing steps.
[0101] If, on the other hand, the judgment result obtained in step
102 indicates a change from the single valve small lift region to
the dual valve great lift region, step 104 is performed to disable
the switching operation of the arm coupling mechanism 72. In other
words, the routine refrains from switching to the dual valve
variable control mode with the switching pin 74 left inserted in
the pin hole 76 although the operating state of the internal
combustion engine 1 has switched to the dual valve great lift
region. When a change from the single valve small region to the
dual valve great lift region is found in step 102, it corresponds
to a change from point B to point C in FIG. 6 or a change from
point F to point G in FIG. 7, and it is anticipated that the
operating state may revert to the single valve small lift region
within a short period of time. Step 104, which is mentioned above,
is performed to avoid a switching operation in such an
instance.
[0102] Next, the routine shown in FIG. 8 performs step 106 to judge
whether a predetermined period of time is reached by the elapsed
time since an operating state change from the single valve small
region to the dual valve great lift region. The present embodiment
performs step 104 to avoid a switch to the dual valve variable
control mode because it anticipates that the operating state will
revert to the single valve small lift region within a short period
of time. However, the operating state may remain in the dual valve
great lift region without immediately reverting to the single valve
small lift region depending on vehicle driving conditions and
operations performed by the driver. In such an instance, a switch
to the dual valve variable control mode should be made to let the
internal combustion engine 1 deliver its expected performance.
Therefore, if the operating state does not revert to the single
valve small lift region when the predetermined period of time is
reached by the elapsed time since a change to the dual valve great
lift region in step 106, the present embodiment terminates the
process of the routine (RETURN) and resumes normal control. When
normal control resumes, a switch to the dual valve variable control
mode is made in accordance with the switching map. It is assumed
that the predetermined period of time usually ranges from several
seconds to ten-odd seconds although its ideal value varies, for
instance, with the type of the internal combustion engine 1 and the
use of the vehicle in which the internal combustion engine 1 is
mounted.
[0103] Next, the routine shown in FIG. 8 performs step 108 to judge
whether the operating state has changed to a region other than the
single valve small lift region and dual valve great lift region.
The region other than the single valve small lift region and dual
valve great lift region is a dual valve variable lift region. In
the dual valve variable lift region, control is exercised in the
dual valve variable control mode so that the lift amounts of both
intake valves 14 vary between a medium lift and a small lift. The
dual valve variable lift region is set for the purpose, for
instance, of enhancing the effect of engine braking when the
internal combustion engine 1 decelerates. The range of the dual
valve variable lift region is stored in the ECU 60 separately from
the switching map.
[0104] If it is found in step 108 that the operating state is
changed to the dual valve variable lift region, the routine
terminates (RETURN) to resume normal control. When normal control
resumes, a switch to the dual valve variable control mode is made
in accordance with predetermined rules. The dual valve variable
lift region can be set as needed, for instance, for low-load
driving, idling, low-temperature startup, and a cold climate as
well as for deceleration.
[0105] Next, the routine shown in FIG. 8 performs step 110 to judge
whether the operating state has changed back from the dual valve
great lift region to the single valve small lift region. In this
instance, a switch to the dual valve variable control mode is
prohibited by the process performed in step 104 above. If the
operating state reverts to the single valve small lift region in
this instance, no instruction is issued for switching to the dual
valve variable control mode; therefore, there is no need to disable
the switching operation. In this situation, therefore, the routine
terminates (RETURN) to resume normal control. If the operating
state remains in the dual valve great lift region in step 110
above, the routine repeats steps 106 and beyond.
[0106] If the switching operation of the arm coupling mechanism 72
is not absolutely necessary, the process described above disables
such a switching operation. This makes it possible to avoid undue
wear of the arm coupling mechanism 72 and enhance its
durability.
[0107] The first embodiment, which has been described above,
assumes that the shift position sensor 62 detects a gear shift by
the transmission. However, an alternative gear shift detection
method may be used. For example, a clutch sensor for detecting
clutch engagement/disengagement may be used to detect a gear shift
upon clutch disengagement (in a situation where a manual
transmission is used). Another alternative would be to detect a
gear shift in accordance with the ratio between the engine speed NE
and vehicle velocity. Since a vehicle velocity sensor is generally
installed in any vehicle, the use of a method based on vehicle
velocity makes it possible to detect a gear shift without adding a
new sensor.
[0108] The first embodiment, which has been described above,
disables the switching operation in a situation where the operating
state has changed from the single valve small lift region to the
dual valve great lift region under predefined conditions. However,
the present invention may alternatively disable the switching
operation in a situation where the operating state has conversely
changed from the dual valve great lift region to the single valve
small lift region.
[0109] The first embodiment, which has been described above, uses a
valve mechanism that continuously varies the valve opening amounts
of the first and second intake valves 14L, 14R (in the dual valve
variable control mode) or the valve opening amount of the first
intake valve 14L (in the single valve variable control mode).
However, the present invention may alternatively use a valve
mechanism that varies the above-mentioned valve opening amounts in
multiple steps.
[0110] The first embodiment, which has been described above,
assumes that the present invention is applied to a variable valve
operating apparatus for an intake valve. However, the present
invention can also be applied to a variable valve operating
apparatus for an exhaust valve.
[0111] The above modifications can also be applied to the other
embodiments, which will be described later.
[0112] In the first embodiment, which has been described above, the
single valve small lift region corresponds to the "single valve
variable control region" according to the first aspect of the
present invention; the dual valve great lift region corresponds to
the "dual valve variable control region" according to the first
aspect of the present invention; the arm coupling mechanism 72
corresponds to the "switching mechanism" according to the first
aspect of the present invention; and the ECU 60 corresponds to the
"storage means" according to the first aspect of the present
invention. The "normal control means" according to the first aspect
of the present invention is implemented when the ECU 60 causes the
arm coupling mechanism 72 to perform a switching operation in
accordance with the switching map; the "condition judgment means"
according to the first aspect of the present invention is
implemented when the ECU 60 performs steps 100 and 102; the
"disable means" according to the first aspect of the present
invention is implemented when the ECU 60 performs step 104; and the
"enable means" according to the fourth aspect of the present
invention is implemented when the ECU 60 performs step 106.
Second Embodiment
Features of Second Embodiment
[0113] A second embodiment of the present invention will now be
described with reference to FIG. 9. However, the differences
between the foregoing embodiment and the second embodiment will be
mainly described while skipping the description of features common
to these two embodiments or describing such features briefly. The
system according to the second embodiment can be implemented by
using the same hardware configuration as the first embodiment and
allowing the ECU 60 to execute a routine shown in FIG. 9, which
will be described later.
[0114] While the vehicle is stopped, the driver may step on the
accelerator pedal to let the internal combustion engine 1 perform a
free acceleration (so-called racing) operation. This free
acceleration operation is rarely conducted for an extended period
of time. Therefore, even if the operating state changes from the
single valve small lift region to the dual valve great lift region
during a free acceleration operation, it is anticipated that the
operating state will revert to the single valve small lift region
within a short period time. In view of such circumstances, the
present embodiment also refrains from switching to the dual valve
variable control mode in the above instance in order to enhance the
durability of the arm coupling mechanism 72.
Details of Process Performed by Second Embodiment
[0115] FIG. 9 is a flowchart illustrating a routine that the ECU 60
according to the present embodiment executes to implement the above
functionality. First of all, the routine shown in FIG. 9 performs
step 120 to judge in accordance with an output generated from the
shift position sensor 62 whether the transmission is shifted to
neutral (when a manual or automatic transmission is used) or
shifted to park (when an automatic transmission is used). If the
transmission is not shifted to neutral or park, the routine does
not perform the following processing steps because a free
acceleration operation does not take place.
[0116] If it is found in step 120 that the transmission is shifted
to neutral or park, the routine performs step 122 to judge whether
the operating state of the internal combustion engine 1 has changed
from the single valve small lift region to the dual valve great
lift region. If the judgment result obtained in step 122 indicates
a change to the dual valve great lift region, it can be concluded
that a free acceleration operation is being conducted. In this
instance, therefore, step 124 is performed to disable the switching
operation of the arm coupling mechanism 72. More specifically,
although the operating state of the internal combustion engine 1 is
changed to the dual valve great lift region, the switching pin 74
is left inserted in the pin hole 76 to refrain from switching to
the dual valve variable control mode.
[0117] Next, the routine shown in FIG. 9 performs step 126 to judge
whether the operating state has changed to a region other than the
dual valve great lift region, that is, to the single valve small
lift region or dual valve variable lift region. If the obtained
judgment result indicates a change to a region other than the dual
valve great lift region, it can be concluded that the free
acceleration operation is terminated. Therefore, the routine
terminates to resume normal control (RETURN). If, on the other
hand, the obtained judgment result does not indicate a change to a
region other than the dual valve great lift region, it can be
concluded that the free acceleration operation is still being
conducted. In this instance, the routine returns to step 124 and
keeps the switching operation disabled.
[0118] When the above process is performed, it is possible to
prevent the arm coupling mechanism 72 from performing an extra
switching operation during a free acceleration operation and
enhance the durability of the arm coupling mechanism 72.
Third Embodiment
Features of Third Embodiment
[0119] A third embodiment of the present invention will now be
described with reference to FIG. 10. However, the differences
between the foregoing embodiments and the third embodiment will be
mainly described while skipping the description of features common
to these three embodiments or describing such features briefly. The
third embodiment has the same hardware configuration as the first
embodiment. The system according to the third embodiment can be
implemented by allowing the ECU 60 to execute a routine shown in
FIG. 10, which will be described later, in addition to the process
according to the first or second embodiment.
[0120] As mentioned earlier, the arm coupling mechanism 72 moves
the switching pin 74 by using the hydraulic pressure of the
lubricating oil for the internal combustion engine 1. While the
internal combustion engine 1 operates, sludge (viscous material)
may be produced in the lubricating oil. If by any chance the
switching pin 74 does not operate for an extended period of time
while the sludge is deposited around the switching pin 74, the
switching pin 74 may bind in the hydraulic chamber 75 or pin hole
76 and become inoperative.
[0121] As described earlier, the first and second embodiments
disable the switching operation of the arm coupling mechanism 72 in
a predefined situation. This reduces the frequency with which the
arm coupling mechanism 72 performs the switching operation. When
the frequency of the switching operation of the arm coupling
mechanism 72 decreases, the switching pin 74 is likely to stay put
for an extended period of time. As a result, it is highly probable
that the switching pin 74 may bind due to the sludge.
[0122] Therefore, if a predetermined value is exceeded by the
number of times the switching operation of the arm coupling
mechanism 72 was disabled or the cumulative time during which the
switching operation of the arm coupling mechanism 72 was disabled,
the present embodiment enables the switching operation to prevent
the switching pin 74 from binding.
Details of Process Performed by Third Embodiment
[0123] FIG. 10 is a flowchart illustrating a routine that the ECU
60 according to the present embodiment executes to implement the
above functionality. The routine shown in FIG. 10 is executed in
conjunction with the routine shown in FIG. 8 or 9.
[0124] The routine shown in FIG. 10 performs step 130 to measure
the number of times the switching operation of the arm coupling
mechanism 72 was disabled by the routine shown in FIG. 8 or 9 and
the cumulative time during which the switching operation of the arm
coupling mechanism 72 was disabled by the routine shown in FIG. 8
or 9, and store the measured number of times and cumulative time in
the ECU 60. The routine then performs step 132 to judge whether
predetermined values are exceeded respectively by the number of
times or cumulative time. The predetermined values are based on the
characteristics of the internal combustion engine 1 and the vehicle
in which the internal combustion engine 1 is mounted, and stored in
the ECU 60. These values are predetermined so as to ensure that the
switching operation is performed before the switching pin 74
binds.
[0125] If the judgment result obtained in step 132 indicates that
one of the predetermined values is exceeded by the measured number
of times or cumulative time, step 134 is performed to stop the
routine's control for disabling the switching operation, which is
shown in FIG. 8 or 9, and resumes normal control. While normal
control is exercised, the arm coupling mechanism 72 performs its
switching operation in accordance with the switching map.
[0126] Next, step 136 is performed to judge whether the switching
operation has been performed by the arm coupling mechanism 72 under
normal control. If the switching operation has been actually
performed by the arm coupling mechanism 72, it means that the
switching operation has been performed to prevent the switching pin
74 from binding. In this instance, step 138 is performed to lift
the ban on switching operation disable control by the routine shown
in FIG. 8 or 9 and enable a switching operation disable control
function. The measured number of times and cumulative time, which
were stored in step 130, are then reset to zero (0). In the above
process, whether the switching operation disable control function
should be enabled is determined by checking whether the switching
operation is actually performed by the arm coupling mechanism 72.
However, an alternative determination method may be used. For
example, whether the switching operation disable control function
should be enabled may alternatively be determined by checking
whether the arm coupling mechanism 72 is instructed to perform a
switching operation.
[0127] When the above process is performed, it is possible to
properly prevent the switching pin 74 from binding due to a
decrease in the frequency with which the arm coupling mechanism 72
performs a switching operation during the process according to the
first or second embodiment.
[0128] In the third embodiment, which has been described above, the
"measurement means" according to the fifth aspect of the present
invention is implemented when the ECU 60 performs step 130; and the
"permission means" according to the fifth aspect of the present
invention is implemented when the ECU 60 performs steps 132 and
134.
Fourth Embodiment
Features of Fourth Embodiment
[0129] A fourth embodiment of the present invention will now be
described with reference to FIG. 11. However, the differences
between the foregoing embodiments and the fourth embodiment will be
mainly described while skipping the description of features common
to these four embodiments or describing such features briefly. The
fourth embodiment has the same hardware configuration as the first
embodiment. Further, the fourth embodiment performs basically the
same process as the first or second embodiment.
[0130] FIG. 11 shows valve lift curves of the first intake valve
14L and the second intake valve 14R. The present embodiment assumes
that the valve lift of the first intake valve 14L is substantially
equal to that of the second intake valve 14R in the dual valve
variable control mode. FIG. 11 shows valve lifts A to E, which are
described below.
[0131] Valve lift A is the maximum valve lift in the dual valve
great lift region (dual valve variable control mode). This valve
lift is preset in accordance with maximum power requirements for
the internal combustion engine 1.
[0132] Valve lift B prevails in a state where the rotational
position of the control shaft 41 coincides with the pin switching
position, that is, the switching pin 74 aligns with the pin hole
76. More specifically, valve lift B prevails while the great lift
arm 71 is not coupled to the second swing cam arm 50R.
[0133] Valve lift C prevails in a state where the great lift arm 71
is coupled to the second swing cam arm 50R so that the valve
opening amount of the second intake valve 14R remains large. More
specifically, valve lift C is the valve lift of the second intake
valve 14R in the single valve variable control mode.
[0134] Valve lift D is the minimum valve lift that can be set by
the variable valve mechanism 40. Valve lift E is the maximum valve
lift that can be set by the variable valve mechanism 40. In the
present embodiment, valve lift A represents the upper limit of its
operating range; therefore, valve lift E is not actually used.
[0135] In the single valve small lift region, a target valve lift
is set within a range from valve lift D to valve lift B. In other
words, the target position of the control shaft 41 in the single
valve small lift region is within a range that begins at the pin
switching position and extends toward a smaller lift, smaller
operating angle region. In the dual valve great lift region, on the
other hand, the target valve lift is set within a range from valve
lift B to valve lift A. In other words, the target position of the
control shaft 41 in the dual valve great lift region is within a
range from the pin switching position corresponding to valve lift B
to a position corresponding to valve lift A, which is in a greater
lift, greater operating angle region.
[0136] As described above, the upper limit of the target valve lift
in the single valve small lift region is represented by valve lift
B. While normal control is exercised, the single valve variable
control mode, that is, a state where the great lift arm 71 is
coupled to the second swing cam arm 50R, is implemented in the
single valve small lift region. Therefore, when the valve mechanism
18 is in the single valve variable control mode, control is
generally exercised while the range below valve lift B is defined
as the target valve lift.
[0137] Meanwhile, the first and second embodiments may disable the
function for switching from the single valve variable control mode
to the dual valve variable control mode and stay in the single
valve variable control mode as described earlier even when the
operating state has changed from the single valve small lift region
to the dual valve great lift region (step 104 in FIG. 8 or step 124
in FIG. 9). Therefore, a target valve lift greater than valve lift
B may be set while the valve mechanism 18 is in the single valve
variable control mode. In this instance, the following situation
occurs.
[0138] In the single valve variable control mode, the second intake
cam 17 usually drives the great lift arm 71, which then drives the
second swing cam arm 50R via the switching pin 74, as described
earlier. However, if the control shaft 41 rotates beyond the pin
switching position corresponding to valve lift B and toward a great
lift and large operating angle region in the single valve variable
control mode, the range over which the first intake cam 16 swings
the second swing cam arm 50R becomes larger than the range over
which the second intake cam 17 swings the second swing cam arm 50R.
This causes the second swing cam arm 50R to reversely drive the
great lift arm 71 via the switching pin 74. In this instance,
therefore, the input roller 73 for the great lift arm 71 leaves the
second intake cam 17.
[0139] If the engine speed NE and load suddenly decrease in a
situation where the input roller 73 for the great lift arm 71 is
separated from the second intake cam 17 as described above, the
control shaft 41 instantaneously rotates toward a small lift and
small operating angle region. The input roller 73 for the great
lift arm 71 may then come into contact again (collide) with the
second intake cam 17, thereby generating noise or damaging the
surfaces of the input roller 73 and the second intake cam 17.
[0140] To avoid the above problem, the present embodiment limits
the target valve lift to valve lift B or smaller when a switch from
the single valve variable control mode to the dual valve variable
control mode is prohibited (step 104 in FIG. 8 or step 124 in FIG.
9), that is, when the operating state enters the dual valve great
lift region in the single valve variable control mode. This
prevents the control shaft 41 from rotating beyond the pin
switching position corresponding to valve lift B and toward a great
lift and large operating angle region while the valve mechanism 18
is in the single valve variable control mode. This makes it
possible to properly prevent the input roller 73 for the great lift
arm 71 from leaving the second intake cam 17. Consequently, the
present embodiment can absolutely avoid noise generation and
prevent the surfaces of the input roller 73 and the second intake
cam 17 from being damaged.
[0141] In the present embodiment, the initial target valve lift in
the dual valve great lift region is within a range from valve lift
B to valve lift A as described earlier. Therefore, if the target
valve lift is limited to valve lift B or smaller in a situation
where a switch from the single valve variable control mode to the
dual valve variable control mode is prohibited, the actual target
valve lift is fixed at valve lift B.
[0142] Since the present embodiment is the same as the first and
second embodiment except as described above, its further
description is omitted here.
[0143] In the fourth embodiment, which has been described above,
the "valve opening amount limitation means" according to the sixth
and seventh aspects of the present invention is implemented when
the ECU 60 limits the target valve lift (target valve opening
amount) to valve lift B or smaller in a situation where a switch
from the single valve variable control mode to the dual valve
variable control mode is prohibited (step 104 in FIG. 8 or step 124
in FIG. 9). Further, the first intake valve 16 corresponds to the
"main cam" according to the seventh aspect of the present
invention; the second intake valve 17 corresponds to the "sub-cam"
according to the seventh aspect of the present invention; and the
input roller 73 for the great lift arm 71 corresponds to the
"mating member" according to the seventh aspect of the present
invention.
* * * * *