Title: Apparatus for controlling fuel injection of engine and method thereof
Abstract: In an engine provided with a variable valve event and lift mechanism that varies a valve lift and a valve operating angle of an intake valve, a pressure of fuel supplied to a fuel injection valve is controlled according to an opening period of the intake valve, which is varied according to the valve operating angle and an engine rotation speed.
Patent Number: 7,013,875 Issued on 03/21/2006 to Saruwatari
| Inventors:
|
Saruwatari; Masayuki (Atsugi, JP)
|
| Assignee:
|
Hitachi, Ltd. (Tokyo, JP)
|
| Appl. No.:
|
606122 |
| Filed:
|
June 26, 2003 |
Foreign Application Priority Data
| Jun 28, 2002[JP] | 2002-191034 |
| Current U.S. Class: |
123/478; 123/180 |
| Current Intern'l Class: |
F02M 51/00 (20060101) |
| Field of Search: |
701/104
123/901.5,901,480,478
|
References Cited [Referenced By]
U.S. Patent Documents
| 4455987 | Jun., 1984 | Sudbeck et al.
| |
| 5791321 | Aug., 1998 | Kondoh.
| |
| 6550457 | Apr., 2003 | Kitagawa et al.
| |
| 2003/0062028 | Apr., 2003 | Kitagawa et al.
| |
| 2004/0134467 | Jul., 2004 | Saruwatari.
| |
| Foreign Patent Documents |
| 6-272580 | Sep., 1994 | JP.
| |
| 9-195840 | Jul., 1997 | JP.
| |
| 2001/-012262 | Jan., 2001 | JP.
| |
| 2001/-041013 | Feb., 2001 | JP.
| |
| 2001/-164951 | Jun., 2001 | JP.
| |
Primary Examiner: Kwon; John T.
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
What is claimed is:
1. An apparatus for controlling fuel injection of an engine provided with an
intake valve and a fuel injection valve disposed on the upstream side of said intake
valve, comprising:
an injection quantity regulator varying an injection quantity per unit time of
said fuel injection valve;
an opening time period detector detecting an opening time period of said intake
valve; and
a controller controlling said injection quantity regulator according to the opening
time period detected by said opening time period detector.
2. An apparatus for controlling fuel injection of an engine according to claim 1,
wherein said engine is provided with a variable valve event and lift mechanism
that varies a valve lift and a valve operating angle of said intake valve, and
said opening time period detector detects the valve operating angle of said intake
valve and a rotation speed of said engine as a state amount correlating to the
opening time period of said intake valve.
3. An apparatus for controlling fuel injection of an engine according to claim
2, wherein said controller controls said injection quantity regulator, so that
a fuel injection period of said fuel injection valve becomes shorter than the opening
time period of said intake valve at least in a low valve lift region of said intake valve.
4. An apparatus for controlling fuel injection of an engine according to claim
3, wherein there is provided an injection timing controller controlling injection
timing of said fuel injection valve, so that fuel injection by said fuel injection
valve is performed within the opening time period of said intake valve at least
in the low valve lift region.
5. An apparatus for controlling fuel injection of an engine according to claim
2, wherein said controller controls the injection quantity per unit time to become
larger as the rotation speed of said engine is higher.
6. An apparatus for controlling fuel injection of an engine according to claim
2, wherein said controller controls the injection quantity per unit time to become
larger as the valve operating angle of said intake valve is smaller.
7. An apparatus for controlling fuel injection of an engine according to claim
1, wherein said injection quantity regulator is a fuel pressure regulator varying
a pressure of fuel supplied to said fuel injection valve, and regulates the injection
quantity per unit time by regulating the pressure of fuel.
8. An apparatus for controlling fuel injection of an engine according to claim
1, wherein said injection quantity regulator is a lift regulator regulating a lift
of a valve body of said fuel injection valve, and regulates the injection quantity
per unit time by regulating the lift of said valve body.
9. An apparatus for controlling fuel injection of an engine according to claim 2,
wherein said engine is provided with a variable valve timing mechanism that varies
a central phase of the valve operating angle of said intake valve, and
in a predetermined low load region where closing timing of said intake valve
is set before the bottom dead center by said variable valve event and lift mechanism
and said variable valve timing mechanism,
said controller controls said injection quantity regulator, so that a fuel injection
period of said fuel injection valve becomes shorter than the opening time period
of said intake valve.
10. An apparatus for controlling fuel injection of an engine according to claim 2,
wherein said variable valve event and lift mechanism comprises:
a camshaft rotatingly linked with said engine;
a control shaft disposed substantially in parallel to said camshaft;
a control cam biased to be fixed to a periphery of said control shaft;
a rocker arm swingingly and axially supported by said control cam;
a swing driving member driving one end portion of said rocker arm to swing according
to the rotation of said camshaft;
a swing cam connected to the other portion of said rocker arm to swing, and operating
said intake valve to be opened; and
an actuator driving said control shaft to be rotated.
11. An apparatus for controlling fuel injection of an engine provided with an
intake valve and a fuel injection valve disposed on the upstream side of said intake
valve, comprising:
injection quantity regulating means for varying an injection quantity per unit
time of said fuel injection valve;
opening time period detecting means for detecting an opening time period of said
intake valve; and
control means for controlling said injection quantity regulating means according
to the opening time period detected by said opening time period detecting means.
12. A method of controlling fuel injection of an engine provided with an intake
valve and a fuel injection valve disposed on the upstream side of said intake valve,
comprising the steps of:
detecting an opening time period of said intake valve; and
controlling an injection quantity per unit time of said fuel injection valve.
13. A method of controlling fuel injection of an engine according to claim 12,
wherein said engine is provided with a variable valve event and lift mechanism
that varies a valve lift and a valve operating angle of said intake valve, and
said step of detecting the opening time period detects a valve operating angle
of said intake valve and a rotation speed of said engine as a state amount correlating
to the opening time period of said intake valve.
14. A method of controlling fuel injection of an engine according to claim 13,
wherein said step of controlling the injection quantity per unit time controls
the injection quantity per unit time, so that a fuel injection period of said fuel
injection valve becomes shorter than the opening time period of said intake valve
at least in a low valve lift region of said intake valve.
15. A method of controlling fuel injection of an engine according to claim 14,
further comprising the step of controlling injection timing of said fuel injection
valve, so that fuel injection by said fuel injection valve is performed within
the opening time period of said intake valve at least in the low valve lift region.
16. A method of controlling fuel injection of an engine according to claim 13,
wherein said step of controlling the injection quantity per unit time controls
the injection quantity per unit time to become larger as the rotation speed of
said engine is higher.
17. A method of controlling fuel injection of an engine according to claim 13,
wherein said step of controlling the injection quantity per unit time controls
the injection quantity per unit time to become larger as the valve operating angle
of said intake valve is smaller.
18. A method of controlling fuel injection of an engine according to claim 12,
wherein said step of controlling the injection quantity per unit time controls
a pressure of fuel supplied to said fuel injection valve, to control the injection
quantity per unit time of said fuel injection valve.
19. A method of controlling fuel injection of an engine according to claim 12,
wherein said step of controlling the injection quantity per unit time controls
a lift of a valve body of said fuel injection valve, to control the injection quantity
per unit time of said fuel injection valve.
20. A method of controlling fuel injection of an engine according to claim 13,
wherein said engine is provided with a variable valve timing mechanism that varies
a central phase of the valve operating angle of said intake valve, and
in a predetermined low load region where closing timing of said intake valve
is set before the bottom dead center by said variable valve event and lift mechanism
and said variable valve timing mechanism,
said step of controlling the injection quantity per unit time controls the injection
quantity of said fuel injection valve, so that a fuel injection period of said
fuel injection valve becomes shorter than the opening time period of said intake valve.
Description
FIELD OF THE INVENTION
The present invention relates to an apparatus for controlling fuel injection
in an engine provided with a fuel injection valve on the upstream side of an intake
valve, and a method thereof.
RELATED ART OF THE INVENTION
Heretofore, there has been known a control system in which an operating
characteristic of an intake valve is changed so that a target intake air amount
of an engine can be obtained (refer to Japanese Unexamined Patent Publication No. 6-272580).
Further, there has also been known a variable valve event and lift mechanism
that varies continuously a valve lift of an engine valve together with a valve
operating angle thereof (refer to Japanese Unexamined Patent Publication No. 2001-012262)
Here, when a valve lift of an intake valve is controlled by the variable valve
event and lift mechanism to adjust an intake air amount of an engine, the valve
lift of the intake valve is controlled to be smaller together with a valve operating
angle thereof.
If the valve lift of the intake valve becomes smaller, since an intake air flow
at an intake stroke is strengthened, an atomization effect of fuel can be achieved.
However, if the valve operating angle becomes smaller, since an opening
period of the intake valve becomes shorter, it is impossible to inject all of fuel
within the opening period of the intake valve, and therefore, sometimes, fuel injection
needs to be started before opening timing of the intake valve.
The fuel injected before the opening timing of the intake valve, stays on the
upstream side of the intake valve, and is sucked into a cylinder all at once immediately
after the intake valve opening.
Consequently, there is a problem in that, if the fuel is injected before
the opening timing of the intake valve, a uniform air-fuel mixture in the cylinder
is not formed.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to enable to form in a cylinder,
a uniform air-fuel mixture with excellent combustion stability, in a condition
where a valve lift of an intake valve is low and a valve operating angle thereof
is small.
In order to accomplish the above-mentioned object, according to the present invention,
an injection quantity per unit time of a fuel injection valve is variably controlled
according to an opening period of an intake valve.
The other objects and features of the invention will become understood from the
following description with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a system structure of an engine in an embodiment.
FIG. 2 is a cross section view showing a variable valve event and lift mechanism
(A—A cross section of FIG. 3) in the embodiment.
FIG. 3 is a side elevation view of the variable valve event and lift mechanism.
FIG. 4 is a top plan view of the variable valve event and lift mechanism.
FIG. 5 is a perspective view showing an eccentric cam for use in the variable
valve event and lift mechanism.
FIGS. 6(A) and (B) are cross section views showing a low lift control condition
of the variable valve event and lift mechanism (B—B cross section view of
FIG. 3).
FIGS. 7(A) and (B) are cross section views showing a high lift control condition
of the variable valve event and lift mechanism (B—B cross section view of
FIG. 3).
FIG. 8 is a characteristic diagram showing a correlation between a cam face
and a valve lift in the variable valve event and lift mechanism.
FIG. 9 is a characteristic diagram showing a correlation between the valve lift
and a valve operating angle in the variable valve event and lift mechanism.
FIG. 10 is a perspective view showing a driving mechanism of a control shaft
in the variable valve event and lift mechanism.
FIG. 11 is a longitudinal cross section view of a variable valve timing mechanism.
FIG. 12 is a block diagram showing an intake air amount control in the embodiment.
FIG. 13 is a block diagram showing the intake air amount control in the embodiment.
FIG. 14 is a block diagram showing the intake air amount control in the embodiment.
FIG. 15 is a diagram of a system structure showing a fuel pressure control apparatus
in the embodiment.
FIG. 16 is a graph showing a correlation between a valve lift characteristic,
an intake stroke and an injection period.
FIG. 17 is a flowchart showing a fuel pressure control in the embodiment.
FIG. 18 is a flowchart showing a fuel injection control in the embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an engine for vehicle.
In FIG. 1, an intake passage
102 of an engine
101 is disposed with
an electronically controlled throttle
104.
Electronically controlled throttle
104 is constructed to drive
a throttle valve
103b to open and close by a throttle motor
103a.
Air is sucked into a combustion chamber
106 via electronically controlled
throttle
104 and an intake valve
105.
A combusted exhaust gas is discharged from combustion chamber
106 via
an
exhaust valve
107, purified by a front catalyst
108 and a rear catalyst
109, and then emitted into the atmosphere.
Exhaust valve
107 is driven to open and close by a cam
111
axially supported by an exhaust side camshaft
110, while keeping a fixed
valve lift and a fixed valve operating angle thereof.
Intake valve
105 is provided with a VEL (Variable valve Event and Lift)
mechanism
112 that performs continuously a variable control of a valve lift
together with a valve operating angle, and a VTC (Variable valve Timing Control)
mechanism
113 that performs continuously a variable control of a central
phase of the valve operating angle.
Exhaust valve
107 may be provided with a variable valve mechanism.
An engine control unit (ECU)
114 incorporates therein a microcomputer.
Engine control unit
114 controls electronically controlled throttle
104, VEL mechanism
112 and VTC mechanism
113, so that a target
intake air amount corresponding to an accelerator opening can be obtained.
Engine control unit
114 receives detection signals from various sensors.
Various sensors include an air flow meter
115 detecting an intake
air amount Q of engine
101, an accelerator sensor
116 detecting an
accelerator opening, a crank angle sensor
117 taking out a rotation signal
from a crankshaft
120, a throttle sensor
118 detecting an opening
TVO of throttle valve
103b, and a water temperature sensor
119
detecting a cooling water temperature Tw of engine
101.
In engine control unit
114, an engine rotation speed Ne is calculated
based
on the rotation signal output from crank angle sensor
117.
Further, an electromagnetic fuel injection valve
131 is disposed
on an intake port
130 at the upstream side of intake valve
105 of
each cylinder.
Fuel injection valve
131 injects fuel of a quantity proportional to an
injection pulse width (valve opening period), when driven to open by an injection
pulse signal from engine control unit
114.
FIG. 2 to FIG. 4 show in detail the structure of VEL mechanism
112.
Note, a mechanism that performs continuously the variable control of the valve
lift and the valve operating angle of intake valve
105 is not limited to
the mechanism shown in FIG. 2 to FIG. 4.
VEL mechanism
112 shown in FIG. 2 to FIG. 4 includes a pair of intake
valves
105,
105, a hollow camshaft (drive shaft)
13 rotatably
supported by a cam bearing
14 of a cylinder head
11, two eccentric
cams (drive cams)
15,
15 axially supported by camshaft
13,
a control shaft
16 rotatably supported by cam bearing
14 and arranged
at an upper position of camshaft
13, a pair of rocker arms
18,
18
swingingly supported by control shaft
16 through a control cam
17,
and a pair of independent swing cams
20,
20 disposed to upper end
portions of intake valves
105,
105 through valve lifters
19,
19, respectively.
Eccentric cams
15,
15 are connected with rocker arms
18,
18 by link arms
25,
25, respectively. Rocker arms
18,
18
are connected with swing cams
20,
20 by link members
26,
26.
Rocker arms
18,
18, link arms
25,
25, and link
members
26,
26 constitute a transmission mechanism.
Each eccentric cam
15, as shown in FIG. 5, is formed in a substantially
ring shape and includes a cam body
15a of small diameter and a flange
portion
15b integrally formed on an outer surface of cam body
15a.
An insertion hole
15c is formed through the interior of eccentric
cam
15 in an axial direction, and also a center axis X of cam body
15a
is biased from a center axis Y of camshaft
13 by a predetermined amount.
Eccentric cams
15,
15 are pressed and fixed to camshaft
13
via camshaft insertion holes
15c at outside positions not interfering
with valve lifters
19,
19, respectively.
Each rocker arm
18, as shown in FIG. 4, is bent and formed in a substantially
crank shape, and a central base portion
18a thereof is rotatably
supported by control cam
17.
A pin hole
18d is formed through one end portion
18b
which
is formed to protrude from an outer end portion of base portion
18a.
A pin
21 to be connected with a tip portion of link arm
25 is pressed
into pin hole
18d. Also, a pin hole
18e is formed through
the other end portion
18c which is formed to protrude from an inner
end portion of base portion
18a. A pin
28 to be connected
with one end portion
26a (to be described later) of each link member
26 is pressed into pin hole
18e.
Control cam
17 is formed in a cylindrical shape and fixed to a periphery
of control shaft
16. As shown in FIG. 2, a center axis P
1 position
of control cam
17 is biased from a center axis P
2 position of control
shaft
16 by α.
Swing cam
20 is formed in a substantially lateral U-shape as shown in
FIG. 2, FIG. 6 and FIG. 7, and a supporting hole
22a is formed through
a substantially ring-shaped base end portion
22. Camshaft
13 is inserted
into supporting hole
22a to be rotatably supported. Also, a pin hole
23a is formed through an end portion
23 positioned at the
other end portion
18c side of rocker arm
18.
A base circular surface
24a of base end portion
22 side
and
a cam surface
24b extending in an arc shape from base circular surface
24a to an edge of end portion
23, are formed on a bottom surface
of swing cam
20. Base circular surface
24a and cam surface
24b are in contact with a predetermined position of an upper surface
of each valve lifter
19 corresponding to a swing position of swing cam
20.
Namely, according to a valve lift characteristic shown in FIG. 8, as shown
in FIG. 2, a predetermined angle range θ
1 of base circular surface
24a is a base circle interval and a range of from base circle interval
θ
1 of cam surface
24b to a predetermined angle range
θ
2 is a so-called ramp interval, and a range of from ramp interval
θ
2 of cam surface
24b to a predetermined angle range
θ
3 is a lift interval.
Link arm
25 includes a ring-shaped base portion
25a and
a protrusion end
25b protrudingly formed on a predetermined position
of an outer surface of base portion
25a. A fitting hole
25c
to be rotatably fitted with the outer surface of cam body
15a of
eccentric cam
15 is formed on a central position of base portion
25a.
Also, a pin hole
25d into which pin
21 is rotatably inserted
is formed through protrusion end
25b.
Link member
26 is formed in a linear shape of predetermined length and
pin insertion holes
26c,
26d are formed through both
circular end portions
26a,
26b. End portions of pins
28,
29 pressed into pin hole
18d of the other end portion
18c of rocker arm
18 and pin hole
23a of end
portion
23 of swing cam
20, respectively, are rotatably inserted
into pin insertion holes
26c,
26d.
Snap rings
30,
31,
32 restricting axial transfer of link
arm
25 and link member
26 are disposed on respective end portions
of pins
21,
28,
29.
In such a constitution, depending on a positional relation between the center
axis P
2 of control shaft
16 and the center axis P
1 of control
cam
17, as shown in FIG. 6 and FIG. 7, the valve lift is varied, and by
driving control shaft
16 to rotate, the position of the center axis P
2
of control shaft
16 relative to the center axis P
1 of control cam
17 is changed.
Control shaft
16 is driven to rotate within a predetermined angle
range by a DC servo motor (actuator)
121 as shown in FIG. 10. By varying
an operating angle of control shaft
16 by actuator
121, the valve
lift and valve operating angle of each intake valve
105 are continuously
varied (refer to FIG. 9).
In FIG. 10, DC servo motor
121 is arranged so that the rotation shaft
thereof
is parallel to control shaft
16, and a bevel gear
122 is axially
supported by the tip portion of the rotation shaft.
On the other hand, a pair of stays
123a,
123b are
fixed to the tip end of control shaft
16. A nut
124 is swingingly
supported around an axis parallel to control shaft
16 connecting the tip
portions of the pair of stays
123a,
123b.
A bevel gear
126 meshed with bevel gear
122 is axially supported
at the tip end of a threaded rod
125 engaged with nut
124. Threaded
rod
125 is rotated by the rotation of DC servo motor
121, and the
position of nut
124 engaged with threaded rod
125 is displaced in
an axial direction of threaded rod
125, so that control shaft
16
is rotated.
Here, the valve lift is decreased as the position of nut
124 approaches
bevel gear
126, while the valve lift is increased as the position of nut
124 gets away from bevel gear
126.
Further, a potentiometer type operating angle sensor
127 detecting
the operating angle of control shaft
16 is disposed on the tip end of control
shaft
16, as shown in FIG. 10. Control unit
114 feedback controls
DC servo motor
121 so that an actual operating angle detected by operating
angle sensor
127 coincides with a target operating angle.
Next, the structure of VTC mechanism
113 will be described based on
FIG. 11.
However, VTC mechanism
113 is not limited to the constitution shown
in FIG. 11, and may be constituted to continuously vary a rotation phase of camshaft
relative to a crankshaft.
VTC mechanism
113 in this embodiment is a so-called vane type variable
valve timing mechanism, and comprises: a cam sprocket
51 (timing sprocket)
which is rotatably driven by a crankshaft
120 via a timing chain; a rotation
member
53 secured to an end portion of an intake side camshaft
13
and rotatably housed inside cam sprocket
51; a hydraulic circuit
54
that relatively rotates rotation member
53 with respect to cam sprocket
51; and a lock mechanism
60 that selectively locks a relative rotation
position between cam sprocket
51 and rotation member
53 at predetermined positions.
Cam sprocket
51 comprises: a rotation portion (not shown in the figure)
having on an outer periphery thereof, teeth for engaging with timing chain (or
timing belt); a housing
56 located forward of the rotation portion, for
rotatably housing rotation member
53; and a front cover and a rear cover
(not shown in the figure) for closing the front and rear openings of housing
56.
Housing
56 presents a cylindrical shape formed with both front and
rear ends open and with four partition portions
63 protrudingly provided
at positions on the inner peripheral face at 90° in the circumferential direction,
four partition portions
63 presenting a trapezoidal shape in transverse
section and being respectively provided along the axial direction of housing
56.
Rotation member
53 is secured to the front end portion of camshaft
and comprises an annular base portion
77 having four vanes
78a,
78b,
78c, and
78d provided on an outer
peripheral face of base portion
77 at 90° in the circumferential direction.
First through fourth vanes
78a to
78d present respective
cross-sections of approximate trapezoidal shapes. The vanes are disposed in recess
portions between each partition portion
63 so as to form spaces in the recess
portions to the front and rear in the rotation direction. An advance angle side
hydraulic chambers
82 and a retarded angle side hydraulic chambers
83
are thus formed.
Lock mechanism
60 has a construction such that a lock pin
84 is
inserted into an engagement hole (not shown in the figure) at a rotation position
(in the reference operating condition) on the maximum retarded angle side of rotation
member
53.
Hydraulic circuit
54 has a dual system oil pressure passage, namely
a first oil pressure passage
91 for supplying and discharging oil pressure
with respect to advance angle side hydraulic chambers
82, and a second oil
pressure passage
92 for supplying and discharging oil pressure with respect
to retarded angle side hydraulic chambers
83. To these two oil pressure
passages
91 and
92 are connected a supply passage
93 and drain
passages
94a and
94b, respectively, via an electromagnetic
switching valve
95 for switching the passages.
An engine driven oil pump
97 for pumping oil in an oil pan
96 is
provided in supply passage
93, and the downstream ends of drain passages
94a and
94b are communicated with oil pan
96.
First oil pressure passage
91 is formed substantially radially in a
base
77 of rotation member
53, and connected to four branching paths
91d communicating with each advance angle side hydraulic chamber
82. Second oil pressure passage
92 is connected to four oil galleries
92d opening to each retarded angle side hydraulic chamber
83.
With electromagnetic switching valve
95, an internal spool valve is arranged
so as to control the switching between respective oil pressure passages
91
and
92, and supply passage
93 and drain passages
94a and
94b.
Engine control unit
114 controls the power supply quantity for an electromagnetic
actuator
99 that drives electromagnetic switching valve
95, based
on a duty control signal superimposed with a dither signal.
For example, when a control signal of duty ratio 0% (OFF signal) is output to
electromagnetic actuator
99, the hydraulic fluid pumped from oil pump
47
is supplied to retarded angle side hydraulic chambers
83 via second oil
pressure passage
92, and the hydraulic fluid in advance angle side hydraulic
chambers
82 is discharged into oil pan
96 from first drain passage
94a via first oil pressure passage
91.
Consequently, an inner pressure of retarded angle side hydraulic chambers
83 becomes a high pressure while an inner pressure of advance angle side
hydraulic chambers
82 becomes a low pressure, and rotation member
53
is rotated to the most retarded angle side by means of vanes
78a to
78d. The result of this is that a valve opening period (opening timing
and closing timing) is delayed relative to a rotation phase angle of crankshaft.
On the other hand, when a control signal of duty ratio 100% (ON signal) is output
to electromagnetic actuator
99, the hydraulic fluid is supplied to inside
of advance angle side hydraulic chambers
82 via first oil pressure passage
91, and the hydraulic fluid in retarded angle side hydraulic chambers
83
is discharged to oil pan
96 via second oil pressure passage
92, and
second drain passage
94b, so that retarded angle side hydraulic chambers
83 become a low pressure.
Therefore, rotation member
53 is rotated to the full to the advance
angle side by means of vanes
78a to
78d. Due to this,
the opening period of intake valve
105 is advanced relative to the rotation
phase angle of crankshaft.
Note, the variable valve timing mechanism is not limited to the one of vane
type as described above, and may be the one constituted to vary the rotation phase
of camshaft relative to the crankshaft by a friction braking of electromagnetic
clutch (electromagnetic brake), as shown in Japanese Unexamined Patent Publication
2001-041013 or 2001-164951, or the one constituted to operate a helical gear by
a hydraulic pressure as shown in Japanese Unexamined Patent Publication 9-195840.
Next, there will be described controls of electronically controlled throttle
104, VEL mechanism
112 and VTC mechanism
113, by engine control
unit
114, referring to block diagrams of FIG. 12 to FIG. 14.
In a target volume flow ratio calculating section
301, a target volume
flow ratio TQH
0ST (target intake air amount) of engine
101 is calculated
in the following manner.
Firstly, a requested air amount Q
0 corresponding to accelerator opening
APO and engine rotation speed Ne is calculated, and also a requested air amount
QISC requested in an idle rotation speed control is calculated.
Then, the sum of requested air amount Q
0 and requested air amount QISC
is obtained as a total requested air amount Q.
Q=Q0+
QISC
Next, total requested air amount Q is divided by engine rotation speed Ne and
an effective discharge amount (total cylinder volume) VOL# to calculate target
volume flow ratio TQH
0ST.
TQH0ST=Q/(
Ne·VOL#)
In a target VEL operating angle calculating section
302, a target operating
angle TGVEL of control shaft
16 in VEL mechanism
112 is calculated,
based on target volume flow ratio TQH
0ST and engine rotation speed Ne.
VEL mechanism
112 is controlled based on target operating angle TGVEL.
Here, the larger target volume flow ratio TQH
0ST is and the higher engine
rotation speed Ne is, target operating angle TGVEL at which the valve lift becomes
larger, is set.
On the other hand, in a low lift region where target volume flow ratio TQH
0ST
is small and engine rotation speed Ne is low, target operating angle TGVEL at which
the closing timing of intake valve
105 is before the bottom dead center,
is set.
However, on the low load and low rotation speed side, due to the minimum
limit of the valve lift, a valve lift amount larger than a requested value corresponding
to target volume flow ratio TQH
0ST is set.
Then, an excess portion is corrected by a throttle control of throttle valve
103b as described later.
In this embodiment, as the operating angle of control shaft
16 becomes
larger, the valve lift of intake valve
105 becomes larger.
In a VTC target angle calculating section
303, a target phase angle TGVTC
(target advance angle) in VTC mechanism
113 is calculated based on target
volume flow ratio TQH
0ST and engine rotation speed Ne.
VTC mechanism
113 is controlled based on target phase angle TGVTC (target
advance angle).
Here, the larger target volume flow TQH
0ST is and the higher engine
rotation speed Ne is, target valve timing is retarded.
That is, the larger the valve lift (valve operating angle) is, valve timing
is retarded so that the valve operating angle and the valve lift are varied, while
opening timing of intake valve being substantially constant.
Accordingly, in the low load and low rotation region, intake valve
105
is opened/closed with an opening characteristic as shown in FIG. 16.
Target operating angle TGVEL is input to a total valve opening area calculating
section
304.
In total valve opening area calculating section
304, target operating
angle
TGVEL is converted into a total opening area of intake valve
105.
The total opening area is an integral value of a valve opening area within the
opening period of intake valve
105.
The total opening area of intake valve
105 is output to a multiplier
312.
In multiplier
312, the total opening area is multiplied by a correction
coefficient calculated by a correction coefficient calculating section
313,
to be output as an effective opening area TVELAA
0.
Correction coefficient calculating section
313 sets a larger correction
coefficient (≧1.0) as engine rotation speed Ne is higher.
In VEL mechanism
12 in this embodiment, as engine rotation speed Ne becomes
higher, the valve lift is likely to become larger than a target due to an inertial force.
As a result, there is caused an error between the opening area calculated based
on target operating angle TGVEL and target phase angle TGVTC, and an actual opening area.
Therefore, in correction coefficient calculating section
313, the
correction coefficient is set corresponding to the likelihood that as engine rotation
speed Ne is higher, the valve lift becomes larger than the target.
In a flow loss correction coefficient calculating section
314, a flow
loss
coefficient CD is calculated based on target operating angle TGVEL (target valve lift).
Then, in a multiplier
315, effective opening area TVELAA
0 is
multiplied by flow loss coefficient CD, to be corrected corresponding to a difference
of flow loss due to the valve lift amount.
Effective opening area TVELAA
0 corrected by being multiplied by
flow loss coefficient CD is divided by effective discharge amount (total cylinder
volume) VOL# in a divider
316 and then divided by engine rotation speed
Ne in a divider
317, to be converted into a state amount AANV.
Further, state amount AANV is converted into a volume flow ratio TQH
0VEL
of intake valve
105 in a converting section
318.
Volume flow ratio TQH
0VEL of intake valve
105 is a value on
the assumption that throttle valve
103b is fully opened.
In a divider
319, target volume flow ratio TQH
0ST is divided by
volume flow ratio TQH
0VEL, to calculate a volume flow ratio QH
0 requested
to throttle valve
103b for obtaining target volume flow ratio TQH
0ST.
Volume flow ratio QH
0 requested to throttle valve
103b is
converted into state amount AANV in a converting section
320.
Further, state amount AANV is multiplied by effective discharge amount (total
cylinder volume) VOL# in a multiplier
321 and then multiplied by engine
rotation speed Ne in a multiplier
322, to obtain an opening area AA requested
to throttle valve
103b.
Then, opening area AA is converted into a target opening TGTVO of throttle
valve
103b in a converting section
323, and electronically
controlled throttle
104 is controlled based on target opening TGTVO.
FIG. 15 is a diagram showing a fuel pressure control system in engine
101.
In FIG. 15, a fuel tank
201 is disposed with a motor type fuel pump
202
on the inside thereof.
A fuel supply pipe
203 has one end connected to a discharge port of fuel
pump
202 and the other end connected to a fuel gallery pipe
205 which
is fixed near cylinder heads of engine
101 along a cylinder array.
Thus, fuel sucked by fuel pump
202 from fuel tank
201 is sent
under pressure to fuel gallery pipe
205.
Fuel gallery pipe
205 is connected with fuel injection valves
131a
to
131d (in case of four-cylinder engine) disposed for each cylinder.
Fuel pump
202 has a characteristic in that a discharge amount thereof
is changed in proportion to an applied voltage.
In fuel gallery pipe
205, there is disposed a fuel pressure sensor
211
detecting a pressure P of fuel supplied to fuel injection valves
131a
to
131d.
Engine control unit
114 feedback controls the applied voltage to fuel
pump
202, so that a detection result of fuel pressure sensor
211
coincides with a target fuel pressure.
Here, for fuel injection by fuel injection valves
131a to
131d,
as shown in FIG. 16, fuel injection timing and an injection quantity per unit time
are set, so that the fuel injection is performed within the opening period of intake
valve
105, even in a low valve lift condition where the closing timing of
intake valve
105 is set before the bottom dead center (BDC).
In the low valve lift condition, if the fuel injection can be performed within
the opening period of intake valve
105, the fuel injected from fuel injection
valve
131 is atomized by a strong intake air flow due to the low valve lift,
and also the fuel is sucked gradually into the cylinder within the intake stroke,
so that a uniform air-fuel mixture is formed in the cylinder.
Consequently, the formation of air-fuel mixture in the low load and
low rotation area (low valve lift region) is improved, thereby enabling to reduce
the fuel consumption and the emissions.
In a condition where the opening period of intake valve
105 is short,
in
order to inject a requested fuel quantity within the opening period, it is necessary
to increase the injection quantity per unit time in fuel injection valve
131.
As a method of increasing the injection quantity per unit time in fuel injection
valve
131, there is a method of using a large sized fuel injection valve
as fuel injection valve
131, or a method of setting in advance the fuel
pressure supplied to fuel injection valve
131 to be high in conformity with
the time of low valve lift.
However, it is more preferable that the fuel pressure supplied to fuel injection
valve
131 is variably set according to the opening period of intake valve
105, which is varied according to the valve lift (valve operating angle)
of intake valve
105 and engine rotation speed Ne.
A fuel injection control for setting the fuel pressure according to the opening
period of intake valve
105 will be described hereunder.
A flowchart of FIG. 17 shows a control of fuel pump
202 by engine control
unit
114.
In step S
111, a map in which target fuel pressures are stored in advance
according to the valve lift (valve operating angle) of intake valve
105
controlled by VEL mechanism
112 and engine rotation speed Ne, is referred
to, to retrieve a target fuel pressure corresponding to the valve lift (valve operating
angle) and engine rotation speed Ne at the time.
Note, in retrieving the target fuel pressure from the map, it is preferable
to obtain the target fuel pressure corresponding to a state of map grid spacing
by the interpolating calculation.
Provided that the valve lift (valve operating angle) of intake valve
105
is fixed, as engine rotation speed Ne becomes higher, the opening period of intake
valve
105 becomes shorter.
Further, provided that engine rotation speed Ne is fixed, as the valve lift
(valve operating angle) of intake valve
105 is smaller, the opening period
of intake valve
105 becomes shorter.
The target fuel pressure is set in conformity with a characteristic of the opening
period of intake valve
105, and as the opening period becomes shorter, the
target fuel pressure is set to a higher value.
If the target fuel pressure rises, since the injection quantity per unit valve
opening period in fuel injection valve
131 is increased with this rise,
an injection period (injection pulse width) required for the injection of requested
fuel quantity becomes shorter.
The target fuel pressure is set to the minimum pressure at which the fuel of
requested quantity can be injected within the opening period of intake valve
105
(refer to FIG. 16).
Thus, even in the small valve operating angle state (low valve lift region)
where the closing timing of intake valve
105 is set before the bottom dead
center, and also even in the case where engine rotation speed Ne is high and the
opening period of intake valve
105 is short, it becomes possible to perform
the fuel injection by the fuel injection valve within the opening period of intake
valve
105.
In step S
112, the applied voltage to fuel pump
202 is feedback
controlled,
so that the fuel pressure detected by fuel pressure sensor
211 coincides
with the target fuel pressure.
A flowchart of FIG. 18 shows a control of fuel injection valve
131 by
engine
control unit
114.
In step S
121, a fuel injection pulse width Ti (injection period) at a
basic
fuel pressure is calculated based on intake air amount Q, engine rotation speed
Ne, cooling water temperature Tw, a battery voltage and the like.
To be specific, a basic injection pulse width Tp is calculated based on intake
air amount Q and engine rotation speed Ne, a correction coefficient CO is set based
on the cooling water temperature and the like, and further, an ineffective injection
pulse width Ts is set based on the battery voltage.
Then, injection pulse width Ti is calculated as Ti=Tp×CO+Ts.
In next step S
122, a fuel pressure based correction value CPFUEL for injection
pulse width Ti is set according to the fuel pressure at the time.
Correction value CPFUEL is for adapting fuel injection pulse width Ti
calculated in conformity with a reference fuel pressure (a reference value of injection
quantity per unit valve opening period) to the injection quantity per unit valve
opening period at the time, and is set to a smaller value as the fuel pressure
is higher at which the injection quantity per unit valve opening period is increased.
That is, when the fuel pressure is higher than the reference fuel pressure and
the injection quantity per unit valve opening period is larger, injection pulse
width Ti (injection period) is corrected to be smaller, so that the fuel of requested
quantity is injected with the corrected injection pulse width Ti.
In step S
123, injection pulse width Ti is corrected based on correction
value CPFUEL, to set a final injection pulse width TI.
TI=(
Ti-Ts)×
CPFUEL+Ts
Injection pulse width Ti contains ineffective injection pulse width Ts,
and injection pulse width corresponding to the requested injection quantity (effective
injection pulse width Te) is Te=Ti-Ts. Therefore, effective injection pulse width
Te=Ti-Ts is multiplied by correction value CPFUEL, and then added with ineffective
injection pulse width Ts, to obtain final injection pulse width TI.
In step S
124, the injection pulse signal with injection pulse width TI
is output to fuel injection valve
131 in synchronism with the opening timing
(intake stroke) of intake valve
105 of each cylinder.
To be specific, injection start timing is reverse calculated based on the injection
pulse width, to output the injection pulse signal, so that the injection pulse
signal starts to be output in synchronism with the opening timing of intake valve
105 of each cylinder, or the fuel injection is finished immediately before
the closing timing of intake valve
105.
Here, the constitution is such that the pressure of fuel supplied to fuel injection
valve
131 is changed based on the opening period of intake valve
105
that is varied according to the valve lift (valve operating angle) of intake valve
105 by VEL mechanism
112 and engine rotation speed Ne, so that the
fuel of requested quantity can be injected within the opening period of intake
valve
105.
Accordingly, the fuel injection is performed within the opening period
of intake valve
105 (refer to FIG. 14).
If the constitution is such that the fuel injection is performed within the opening
period of intake valve
105, it is possible to atomize all of fuel due to
the intake air flow within the intake stroke, and in particular, the intake air
flow is strengthened in the low valve lift region where the closing timing of intake
valve
105 is set before the bottom dead center, thereby achieving a large
atomization effect.
Moreover, since the fuel injection is started in synchronism with the opening
timing of intake valve
105 and thereafter the fuel is continuously sucked
into the cylinder within the intake stroke, a uniform air-fuel mixture can be formed
in the cylinder, thereby enabling to improve the air-fuel mixture formation as
well as the atomization effect, and to reduce the fuel consumption and the emissions.
In the above embodiment, VEL mechanism
112 that varies continuously the
valve lift and valve operating angle of intake valve
105, has been used,
however, the constitution may be such that the valve lift and valve operating angle
are switched in stepwise by the switching of cam, and the like.
Further, the constitution may be such that a lift characteristic of a valve
body of fuel injection valve
131 is changed according to the opening period
of intake valve
105 without changing the fuel pressure, so that the injection
quantity per unit time of fuel injection valve
131 is changed corresponding
to the opening period of intake valve
105.
Moreover, the constitution may be such that the fuel injection is performed
within the opening period of intake valve
105 only in the low load region
(low valve lift region), and in a high load region (high valve lift region) where
the closing timing of intake valve
105 is at or after the bottom dead center,
the fuel injection is started before the opening timing of intake valve
105.
The entire contents of Japanese Patent Application No. 2002-191034, filed Jun.
28, 2002, a priority of which is claimed, are incorporated herein by reference.
While only a selected embodiment has been chosen to illustrate the present
invention, it will be apparent to those skilled in the art from this disclosure
that various change and modification can be made herein without departing from
the scope of the invention as defined in the appended claims.
Furthermore, the foregoing descriptions of the embodiment according
to the present invention are provided for illustration only, and not for the purpose
of limiting the invention as defined by the appended claims and their equivalents.
*
