Information
-
Patent Grant
-
6615778
-
Patent Number
6,615,778
-
Date Filed
Wednesday, November 21, 200122 years ago
-
Date Issued
Tuesday, September 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Chang; Ching
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 9015
- 123 9016
- 123 9017
- 123 9018
- 123 9031
- 464 1
- 464 2
- 464 160
- 251 12
- 251 251
-
International Classifications
-
Abstract
In a variable valve timing apparatus for variably controlling the valve timing by changing a rotation phase of a camshaft with respect to a crankshaft, an abnormality diagnosis of the apparatus is performed on a condition that a change amount per unit time in a control target value of the rotation phase has been kept equal to or less than a predetermined limit value for a predetermined period or more.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for diagnosing an abnormality in a variable valve timing apparatus for an internal combustion engine.
RELATED ART OF THE INVENTION
There has been known a conventional variable valve timing apparatus for an engine, for changing a rotation phase of a camshaft relative to a crankshaft by controlling a rotation delay of the camshaft relative to the crankshaft based on a friction braking by an electromagnetic brake (Japanese Unexamined Patent Publication 10-153104).
In this variable valve timing apparatus, for example, a basic control amount of the electromagnetic brake is calculated based on a target rotation phase (target rotation delay) and an engine rotation speed, while calculating a feedback control amount from a deviation between the target rotation phase and an actual rotation phase. Then, a final control amount (for example, duty control amount) is determined from the basic control amount and the feedback control amount, to control a current flowing in an electromagnetic coil constituting the electromagnetic brake.
As a variable valve timing apparatus for an internal combustion engine, in general, a hydraulic type apparatus other than the above type is known.
An abnormality diagnosis of such a variable valve timing apparatus (VTC) has been on condition that a target value (hereinafter, target angle) of the rotation phase of the camshaft relative to the crankshaft continues to be held constant for a predetermined period or more (Japanese Unexamined Patent Publication 2000-54870).
In the above variable valve timing apparatus (VTC), since an engine operating region for each target angle is set a relatively large, an opportunity to establish the abnormality diagnosis condition can be secured enough. However, in particular, in the above mentioned electromagnetic brake type apparatus, since the target angle is set fine for each narrow engine operating region, it is hard to sufficiently secure the opportunity to establish the abnormality diagnosis condition, leading a possibility that the diagnosis is not completed.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of the foregoing problem, and has an object of securing an opportunity to establish an abnormality diagnosis condition and completing a diagnosis even in a case a target angle is set fine.
To achieve the above object, with the present invention, in a variable valve timing apparatus constituted to change the valve timing by changing a rotation phase of a camshaft relative to a crankshaft, an abnormality diagnosis in this apparatus is performed on condition that a change amount per unit time of a control target value of the rotation phase continues to be held at a predetermined limit value or less for a predetermined period.
Accordingly, even in case the control target value (target angle) of the rotation phase is set fine to be changed by a slight change of an engine operating condition, a diagnosis execution is permitted on condition that the change amount per unit time continues to be held at the limit value or less for the predetermined period.
Therefore, diagnosis opportunity is sufficiently secured and the diagnosis can be completed.
The other objects and features of this invention will become understood from the following description with accompanying drawings.
BRIEF EXPLANATION OF THE DRAWINGS
FIG. 1
is a sectional view of a variable valve timing apparatus according to an embodiment.
FIG. 2
is an exploded perspective view of the variable valve timing apparatus according to the embodiment.
FIG. 3
is a block diagram of the variable valve timing apparatus according to the embodiment.
FIGS. 4A and 4B
illustrate a flow chart showing a routine according to the invention for judging whether or not an abnormality diagnosis execution permission condition is established.
FIG. 5
is a flow chart of an abnormality diagnosis routine according to the embodiment.
EMBODIMENT
An embodiment according to the invention will be explained as follows.
FIG. 1
is a sectional view of a variable valve timing apparatus using an electromagnetic brake in the embodiment and
FIG. 2
is an exploded perspective view thereof.
In variable valve timing apparatus
1
shown in FIG.
1
and
FIG. 2
, a pulley
2
(or sprocket) is rotatably supported around an axis of an end portion
111
of a camshaft
110
rotatably supported to a cylinder head
120
. Pulley
2
is supported to camshaft
110
in a relative rotatable manner, and is rotated in synchronization with the rotation of a crankshaft of an engine.
On an extending line of end portion
111
of camshaft
110
is fixed a transmission member
3
with a gear being formed around an axis thereof, by a bolt
31
and the rotation of pulley
2
is transmitted to transmission member
3
through a transmission mechanism to be described later.
A cylindrical drum
41
with a flange is disposed on the same axis as camshaft
110
, and between drum
41
and pulley
2
is disposed a coil spring
42
for urging a rotation phase of drum
41
to advance. That is, a case member
44
is fixed to pulley
2
and an outer peripheral end of coil spring
42
is fixed to an inner peripheral surface portion of case member
44
and an inner peripheral end of coil spring
42
is fixed to an outer peripheral surface of drum
41
.
A gear
32
formed around the axis of transmission member
3
is in mesh with a gear
433
formed on an inner periphery of a cylindrical piston member
43
by a helical mechanism with a helical gear.
Engagement portions
431
,
431
are projectingly formed on opposite two portions of an outer peripheral surface of piston member
43
, to be engaged between pawl members
21
,
21
extending in an axial direction of camshaft
110
from a rotation center portion of pulley
2
. Piston member
43
and pulley
2
are rotated on the same phase by this engagement.
Engagement portions
431
,
431
of piston member
43
are formed with male screws
432
as a center thereof being an axis of piston member
43
, respectively, to be engaged with female screws
411
formed on an inner peripheral surface of drum
41
by a screw function.
A drum bearing member
45
is disposed between an outer periphery of transmission member
3
and an inner periphery of drum
41
, to bear the relative rotation of them. A pawl receiving member
7
a
is disposed between drum bearing member
45
and the inner peripheral surface of drum
41
.
Pawl receiving member
7
a
is supported by the inner peripheral surface of drum
41
and contacts step portions
22
,
22
formed on outer peripheral surfaces of tip end portions of pawl members
21
,
21
to retain pawl members
21
,
21
in a radial direction of camshaft
110
.
A sucked member
46
is formed with an internal spur gear
461
at a rotation center thereof and the gear
461
is engaged with a spur gear
33
formed on a tip end portion of transmission member
3
. Thereby, sucked member
46
is constituted to be slidable to transmission member
3
in an axial direction of transmission member
3
and also rotatable on the same phase as transmission member
3
.
A gear
413
is formed on a side surface of a flange portion
412
of drum
41
to face a gear
463
formed on one surface
462
of sucked member
46
. As a result, both of these gears are in mesh to engage drum
41
and sucked member
46
in the rotation direction.
A first electromagnetic solenoid
5
b
and a second electromagnetic solenoid
5
a
are positioned through a bearing member
6
so as to surround an axis line of camshaft
110
, and also to surround transmission member
3
fixed to the end portion
111
of camshaft
110
, and an outer peripheral surface of bolt
31
fixing transmission member
3
.
A spacer member
47
is inserted fixedly between a head portion
311
of bolt
31
and the tip end portion of transmission member
3
and, on an outer peripheral surface side of spacer member
47
, second electromagnetic solenoid
5
a
is disposed through bearing member
6
. Further, first electromagnetic solenoid
5
b
constituting an electromagnetic brake is disposed between second electromagnetic solenoid
5
a
and an outer peripheral surface of sucked member
46
. Second electromagnetic solenoid
5
a
is fixed to a case
8
by a bolt
51
a.
An operation of the embodiment will be explained as follows.
In order to change a rotation phase of camshaft
110
into an advance side, piston member
43
is moved to the axial direction of camshaft
110
by a magnetic field generated by first electromagnetic solenoid
5
b.
Namely, First of all, when sucked member
46
is sucked by the magnetic field generated by second electromagnetic solenoid
5
a
, gear
463
of sucked member
46
and gear
413
of drum
41
are separated from each other, so that drum
41
can be relatively rotated to pulley
2
.
Then, drum
41
is sucked by the magnetic field generated by first electromagnetic solenoid
5
b
to be pushed against an end face of first electromagnetic solenoid
5
b
, thereby performing a friction braking. Accordingly, drum
41
is subjected to a relative rotation due to a rotation delay to pulley
2
against an urging force of coil spring
42
, and piston member
43
in mesh by screw
411
and screw
432
is moved to the axial direction of camshaft
110
. Since piston member
43
and transmission member
3
are engaged by the helical mechanism, the rotation phase of transmission member
3
, as well as camshaft
110
is changed to the advance side to pulley
2
by the movement of piston member
43
. As a result, as a current value to first electromagnetic solenoid
5
b
is increased and a braking force (slide friction) against the urging force of coil spring
42
is increased, the rotation phase of camshaft
110
is changed further to the advance side of camshaft
110
.
As described above, since the rotation phase of camshaft
110
is changed to pulley
2
(crankshaft) depending on a rotation delay amount of drum
41
determined corresponding to the braking force by the electromagnetic brake and the braking force of the electromagnetic brake is controlled by duty-controlling a current value supplied to first electromagnetic solenoid
5
b
, a change amount (advance amount) of the rotation phase can be continuously controlled by changing a duty ratio. The current value supplied to first electromagnetic solenoid
5
b
is increased in response to an increase in duty value (%) equivalent to a control amount of the electromagnetic brake.
FIG. 3
is a block diagram showing a control system of the variable valve timing apparatus having the above constitution. A control unit
511
incorporating therein a microcomputer for controlling the power supply to first electromagnetic solenoid
5
b
and second electromagnetic solenoid
5
a
, is input with detections signals from an air flow meter
512
for detecting an engine intake air amount, a crank angle sensor
513
for detecting a crank rotation, a water temperature sensor
514
for detecting an engine cooling water temperature, an atmosphere temperature sensor
515
for detecting an atmosphere temperature, a cam sensor
516
for detecting a cam rotation and the like.
Control unit
511
duty-controls the power supply to first electromagnetic solenoid
5
b
to change the rotation phase of camshaft
110
. When the rotation phase reaches a target rotation phase, gear
463
of sucked member
46
and gear
413
of drum
41
are engaged with each other by cutting off the power supply to second electromagnetic solenoid
5
a
, and drum
41
is fixed in a phase state at that time to pulley
2
, to cut off the power supply to first electromagnetic solenoid
5
b.
An abnormality diagnosis of the variable valve timing apparatus controlled in the above manner will be executed as follows.
FIGS. 4A and 4B
illustrate a flow chart of a routine according to the invention for judging whether or not an abnormality diagnosis execution permission condition is established.
In
FIG. 4A
at Step
1
, various operating conditions detected from the respective sensors are read out.
At Step
2
, it is judged whether or not an engine rotation speed Ne is within a predetermined range (NeL≲Ne≲NeH). When it is within the predetermined range, the control goes to Step
3
.
At Step
3
, it is judged whether or not an engine cooling water temperature (water temperature) Tw is within a predetermined range (TwL≲Tw≲TwH). When it is within the predetermined range, the control goes to Step
4
.
At Step
4
, it is judged whether or not a battery voltage VB is within a predetermined range (VBL≲VB≲VBH). When it is within the predetermined range, the control goes to Step
5
.
At Step
5
, it is judged whether or not a diagnosis result of signal of the cam sensor
516
, such as disconnection or short-circuit, is OK. When it is OK, the control goes to Step
6
.
At Step
6
, it is judged whether or not a control target value, that is, a target angle VTCTRG is at a reference position regulated by a stopper, specifically at 0 (maximum retard position). When it is not at the reference position, the control goes to Step
8
.
At Step
7
, a change ratio TRGCHG of the target angle VTCTRG is calculated as follows.
TRGCHG=|IVTCTRG−VTCTRGz|
VTCTRGz: target angle VTCTRG prior to 10 ms
At Step
8
, a limit value VTRLIM being a threshold value of a diagnosis permission condition of the target angle change ratio TRGCHG is set based on the water temperature Tw and the engine rotation speed Ne.
At Step
9
, it is judged whether or not an absolute value of the change ratio TRGCHG of the target angle VTCTRG calculated at Step
7
is equal to or less than the limit value VTRLIM. When it is equal to or less than the limit value VTRLIM, the control goes to Step
10
wherein a timer is counted up.
At Step
11
, it is judged whether or not a timer count value reaches a predetermined value CLERTIM.
The execution of the abnormality diagnosis is not permitted at Step
13
until the timer count value reaches the predetermined value CLERTIM. When the timer count value reaches the predetermined value CLERTIM, that is, when the absolute value of the change ratio TRGCHG of the target angle VTCTRG has been kept equal to or less than the limit value VTRLIM for a predetermined period or more, the control goes to Step
12
, wherein the execution of the abnormality diagnosis is permitted.
In this way, even if the target angle is set fine and is changed due to a slight change in the engine operating condition, the diagnosis is permitted to secure the diagnosis opportunity as long as the change ratio of the target angle is maintained equal to or less than the predetermined value for the predetermined period or more.
When the diagnosis permission condition is established, the abnormality diagnosis is executed.
FIG. 5
is a flow chart of an abnormality diagnosis routine.
In
FIG. 5
, at Step
21
, the target angle VTCTRG set based on a basic fuel injection quantity Tp being a representative value of the engine rotation speed Ne and an engine load is read out.
At Step
22
, an actual angle VTCNOW (actual rotation phase of the camshaft) is read out based on a signal of cam sensor
516
.
At Step
23
, a deviation ERROR (error amount) between the target angle VTCTGR and the actual angle VTCNOW is calculated as the following equation.
VTCTGR−VTCNOW
At Step
24
, it is judged whether or not the deviation ERROR is within a predetermined range (OFAGB≲ERROR≲OFAGF).
When the deviation ERROR is within the predetermined range, the diagnosis result is judged as OK at Step
25
while when it is not within the predetermined range, the timer is counted up at Step
26
. Then at Step
27
, it is judged whether or not a count value reaches a predetermined value CNGDLY.
When the count value reaches the predetermined value CNGDLY, that is, when the deviation ERROR has been kept out of the predetermined range for a predetermined time or more, the control goes to Step
28
wherein the diagnosis result is judged as NG (presence of abnormality).
As a variable valve timing apparatus of electromagnetic brake type, there is an apparatus for performing a duty control by supplying a power to an electromagnetic brake all the time without provided with a locking mechanism by a second electromagnetic solenoid. The present invention can also be applied to the apparatus of such a constitution. The present invention can be applied to a hydraulic variable valve timing apparatus.
The entire contents of basic Japanese Patent Application No. 2000-360057 filed Nov. 27, 2000, a priority of which is claimed, are herein incorporated by reference.
Claims
- 1. An apparatus for diagnosing a variable valve timing apparatus comprising:a variable valve timing apparatus which comprises, a camshaft for driving an intake valve and an exhaust valve of an internal combustion engine to be open/close, a valve timing adjustment mechanism for variably controlling a rotation phase of said camshaft with respect to a crankshaft, to adjust the valve timing of said intake valve and exhaust valve; a change amount calculation unit for calculating a change amount per unit time in a control target value of said rotation phase; a comparison unit for comparing said calculated change amount with a predetermined limit value; a diagnosis permission unit for permitting an abnormality diagnosis of said variable valve timing apparatus on a condition that said change amount has been kept equal to or less than said predetermined limit value for a predetermined period by said comparison of said comparison unit; and a diagnosis unit for diagnosing an abnormality of said variable valve timing apparatus when said diagnosis permission unit permits said abnormality diagnosis.
- 2. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein at least one of said predetermined limit value used in said comparison unit and said predetermined period used in said diagnosis permission unit is variably set corresponding to an engine temperature.
- 3. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein at least one of said predetermined limit value used in said comparison unit and said predetermined period used in said diagnosis permission unit is variably set corresponding to an engine rotation speed.
- 4. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein said diagnosis permission unit permits an abnormality diagnosis on a condition that an engine operating condition and an environment state satisfy predetermined conditions, in addition to the condition that the change amount has been kept equal to or less than said predetermined limit value for a predetermined period.
- 5. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein said diagnosis permission unit also permits an abnormality diagnosis on a condition that the control target value of said rotation phase does not coincide with a reference value regulated by a stopper, in addition to the condition that the change amount has been kept equal to or less than said predetermined limit value for a predetermined period.
- 6. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein said diagnosis unit judges an abnormality when a deviation between the control target value of said rotation phase and an actual value of said rotation phase has been kept out of a predetermined range for a predetermined period or more.
- 7. An apparatus diagnosing a variable valve timing apparatus according to claim 1, wherein said valve timing adjustment mechanism changes said rotation phase with respect to the crankshaft with a friction braking by an electromagnetic brake.
- 8. A method for diagnosing a variable valve timing apparatus which comprises a variable valve timing adjustment mechanism for variably controlling a rotation phase of a camshaft with respect to a crankshaft, to adjust the valve timing of an intake valve and an exhaust valve of an internal combustion engine, comprising:calculating a change amount per unit time in a control target value of said rotation phase; comparing said calculated change amount with a predetermined limit value; permitting an abnormality diagnosis of said variable valve timing apparatus on a condition that said change amount has been kept equal to or less than said predetermined limit value for a predetermined period by said comparison; and diagnosing an abnormality of said variable valve timing apparatus when said abnormality diagnosis is permitted.
- 9. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein at least one of said predetermined limit value and said predetermined period is variably set corresponding to an engine temperature.
- 10. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein at least one of said predetermined limit value and said predetermined period is variably set corresponding to an engine rotation speed.
- 11. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein an abnormality diagnosis is permitted on a condition that an engine operating condition and an environment state satisfy predetermined conditions, in addition to the condition that the change amount has been kept equal to or less than said predetermined limit value for a predetermined period.
- 12. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein an abnormality diagnosis is permitted on a condition that the control target value of said rotation phase does not coincide with a reference value regulated by a stopper, in addition to the condition that the change amount has been kept equal to or less than said predetermined limit value for a predetermined period.
- 13. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein the presence of abnormality is judged when a deviation between the control target value of said rotation phase and an actual value of said rotation phase has been kept out of a predetermined range for a predetermined period or more.
- 14. A method for diagnosing a variable valve timing apparatus according to claim 8, wherein the valve timing is controlled by changing said rotation phase with respect to the crankshaft with a friction braking by an electromagnetic brake.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-360057 |
Nov 2000 |
JP |
|
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DE |
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JP |
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