JPH04303141A - Controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To control a fuel injection timing properly, and stabilize a combustion condition in an engine capable of controlling an intake air quantity by changing a valve opening period of an intake valve. CONSTITUTION:An injection completion timing (theta IE) for a fuel injection valve is determined to be either before starting an intake stroke or in the middle of the intake stroke corresponding to a relation between a valve closing completion timing (theta ICOBJ) for an intake valve and a determined valve closing timing (theta ref) set corresponding to an engine operation condition, and an injection starting timing (theta IS) is determined based on a result.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a control device for an internal combustion engine, and in particular, controls the intake air amount of the engine by changing the opening period of the intake valve, and also adjusts the fuel injection timing to the operating state of the engine. The present invention relates to a control device that controls according to the user's needs.

0002

2. Description of the Related Art Engines and their control devices that can control the amount of intake air by changing the opening period of the intake valves have been proposed in the past (for example, Japanese Patent Laid-Open No. 63-1
No. 76610).

[0003] Furthermore, in an engine in which fuel is injected independently into each cylinder by a fuel injection valve disposed corresponding to each cylinder of the engine, the fuel injection start timing is determined by
A fuel injection control method is conventionally known in which the fuel injection end timing is calculated backward from the fuel injection time so that the fuel injection end timing is at a predetermined crank angle within the range of 30° to 120° after top dead center. No. 1973-29733).

0004

[Problem to be Solved by the Invention] In an engine in which the amount of intake air can be controlled by changing the opening period of the intake valve, the opening period of the intake valve changes over a wide range depending on the engine operating condition. Therefore, if the conventional fuel injection control method described above, which assumes that the intake valve opening period is constant, is applied as is, the following problems will occur.

That is, when the engine is in a low load and low rotation state, the intake valve opening period is short and the intake air flow velocity is low. Therefore, if fuel is injected during the intake valve opening period, some fuel will enter the cylinder. It remains in the intake pipe without being inhaled, causing fluctuations in the air-fuel ratio of the air-fuel mixture. As a result, the combustion state fluctuates, resulting in unstable engine rotation and fluctuations in exhaust gas characteristics.

On the other hand, if fuel injection is completed before the opening period of the intake valve in order to avoid the above-mentioned problems, there will be a delay in the intake of fuel when the engine is under high load, which will affect the combustion state and charging efficiency. It is not possible to obtain sufficient engine performance.

The present invention has been made in view of the above points, and is an object of the present invention to appropriately control the fuel injection timing in an engine in which the amount of intake air can be controlled by changing the opening period of the intake valve, thereby improving the combustion state. It is an object of the present invention to provide a control device that can achieve stabilization.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a valve control means for controlling the intake air amount of the engine by changing the opening period of the intake valve of the internal combustion engine, and In a control device for an internal combustion engine comprising a fuel injection means for injecting fuel into a pipe, the injection end timing of the fuel injection means is set to either before the start of an intake stroke or during the intake stroke, depending on the timing of completion of closing of the intake valve. and an injection start timing determining means that determines the injection start time of the fuel injection means depending on whether the injection end time is before the start of the intake stroke or during the intake stroke. It was designed to be provided.

[0009] Further, the injection end timing determining means determines the injection end timing to be before the start of the intake stroke when the closing completion timing of the intake valve is earlier than a predetermined determination time set depending on the operating state of the engine. On the other hand, when the valve closing completion time is later than the predetermined determination time, it is desirable that the injection end time be set during the intake stroke.

[0010] Furthermore, the intake valve closing completion timing may be determined based on a value calculated according to engine operating parameters including at least an engine rotational speed and a parameter representing a driver's request to the engine, or an intake valve detected by a lift sensor. It is desirable that the value be calculated based on the lift amount of the valve.

[0011]

[Operation] The injection end timing of the fuel injection means is determined to be either before the intake stroke starts or during the intake stroke, depending on the intake valve completion timing, and the injection start timing is determined according to the determination result. Ru.

[0012] When the intake valve closing completion timing is earlier than a predetermined determination timing set according to the operating state of the engine, the injection end timing is determined to be before the start of the intake stroke; If it is later than the determination timing of , it is determined that the intake stroke is in progress.

[0013] The timing of completion of closing the intake valve is determined according to engine operating parameters including at least the engine speed and a parameter representing the driver's request to the engine, or based on the lift amount of the intake valve detected by a lift sensor. Calculated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the overall configuration of an internal combustion engine and its control device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an internal combustion engine (main body), which has a hydraulically driven valve unit 20 for hydraulically driving intake valves and exhaust valves. A fuel injection valve 14 is disposed in the middle of an intake pipe 1a of the engine 1, and the injection valve 14 is electrically connected to an electronic control unit (hereinafter referred to as "ECU") 2. The ECU 2 is also connected to a solenoid (202 in FIG. 5, which will be described later) and a spark plug (not shown) in the hydraulic valve unit 20, and receives control signals (θO
FF, θON and θIG) are supplied.

The ECU 2 includes a cylinder discrimination sensor (hereinafter referred to as ``CYL signal pulse'') that outputs a signal pulse (hereinafter referred to as ``CYL signal pulse'') at a predetermined crank angle position of a specific cylinder of the engine 1.
3. A TDC that generates a TDC signal pulse at a crank angle position a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder (every 180 degrees of crank angle in a 4-cylinder engine). sensor 4, and a crank angle sensor (hereinafter referred to as "CRK signal pulse") that generates one pulse (hereinafter referred to as "CRK signal pulse") at a constant crank angle (for example, 30 degrees) period shorter than the period of the TDC signal pulse.
5 is electrically connected to CYL
A signal pulse, a TDC signal pulse and a CRK signal pulse are sent to the ECU2. The output signal pulses of these three sensors 3, 4, and 5 are the intake valve closing timing, fuel injection timing,
It is used for various timing controls such as ignition timing and for detecting engine rotation speed.

Furthermore, the ECU 2 has engine cooling water temperature (T
W), an intake temperature sensor (TA sensor) 7, an oxygen concentration sensor (O2 sensor) 8 that detects the oxygen concentration in exhaust gas, and an intake valve lift amount (Lft) of the engine 1. ), a hydraulic sensor (Poil sensor) 10 that detects the hydraulic oil pressure (Poil) and oil temperature (Toil) of the hydraulic oil of the hydraulically driven valve unit 20 of the engine 1, and an oil temperature sensor (Toil).
l sensor) 11, an accelerator opening sensor (θACC sensor) 12 that detects the amount of depression of the accelerator pedal as a parameter representing the driver's request to the engine, and an atmospheric pressure sensor (PA sensor) that detects atmospheric pressure (PA). 1
3 are electrically connected, and these sensors 6 to 13
A detection signal of is supplied to the ECU 2.

The ECU 2 is composed of a central processing unit, a memory, a control signal output circuit, etc. (not shown), and controls the operation and ignition timing of the hydraulically driven valve unit 20 based on the detection signals from the various sensors mentioned above. , fuel injection valve 14
Controls the valve opening timing and valve closing timing (valve opening time).

FIG. 2 is a cross-sectional view of the hydraulically driven valve unit 20, which is attached to the cylinder head 21 of each cylinder of the engine 1. cylinder head 21
is opened at the top of the combustion chamber (not shown) of the engine 1,
An intake valve port 23 is provided, the other end of which communicates with an intake port 24 . The intake valve 22 is arranged so as to be guided so as to be freely movable in the vertical direction in the figure within the cylinder head 21 in order to open and close the intake valve port 23. A valve spring 26 is compressed between the flange 25 of the intake valve 22 and the cylinder head 21, and the valve spring 26 biases the intake valve 22 upward in the figure (in the valve closing direction). Ru.

On the other hand, a cam shaft 28 having a cam 27 is rotatably disposed on the left side of the cylinder head 21 in the drawing. This camshaft 28 is connected to a crankshaft (not shown) via a timing belt (not shown). A hydraulically driven valve unit 20 is interposed between the cam 27, which is integrally formed with the camshaft 28, and the intake valve 22.

The hydraulically driven valve unit 20 includes a hydraulically driven mechanism 30 that presses the intake valve 22 downward against the valve spring 26 to open and close it according to the profile of the cam 27, and a pressing force of the hydraulically driven mechanism 30. The hydraulic release mechanism 31 disables the valve opening during the valve opening operation, thereby closing the intake valve 22 regardless of the cam profile.

The hydraulic drive mechanism 30 includes a cylinder head 21
A first cylinder body 33 is fixed to a block 32 that is integrally formed with the cylinder hole 33 of the first cylinder body 33 with its lower end (front end) abutting the upper end (rear end) of the intake valve 25.
A valve-side piston (valve-driving piston) 34 that is slidably fitted into the first cylinder body 33 and the valve-side piston 3
4, a second cylinder body 36 fixed to the block 32, a lifter 35 in sliding contact with the cam 27, and a second cylinder body with its lower end in contact with the lifter 35.
a cam-side piston 37 slidably fitted to the lower part of the cylinder body 36; a hydraulic pressure generation chamber 39 defined by the second cylinder body 36 and the cam-side piston 37; The main component is an oil passage 40 connecting the chamber 38, and when the hydraulic pressure in the hydraulic pressure chamber 38 is above a predetermined value, the intake valve 22 is opened and closed according to the profile of the cam 27.

The block 32 includes a flange 25 of the intake valve 22.
A lift sensor 9 is disposed at a position opposite to. The lift sensor 9 is connected to the ECU 2 and is connected to the intake valve 22.
detects the lift amount and supplies the detection signal to the ECU 2.

FIG. 3 is an enlarged view showing the vicinity of the hydraulic pressure chamber 38 defined by the first cylinder body 33 and the valve-side piston 34, and the illustrated state is when the intake valve 22 is in the fully closed position. (The position where the valve seat 21a is seated in FIG. 2) is shown, that is, the valve side piston 34 has moved to the uppermost position.

The first cylinder body 33 has an oil passage 40a forming a part of the oil passage 40, a fixed orifice 33c communicating the oil passage 40a with the top of the hydraulic pressure chamber 38, and a valve-side piston 34. An annular recess 33 forming an annular oil passage 33d therebetween.
e is provided.

The valve side piston 34 has a valve hole 341a,
The valve body 341 has a spherical valve body 341b that can close the valve hole 341a from the hydraulic pressure chamber side, and a plurality of communication holes 341d.
A check valve 3 consisting of a retainer 341c that holds b.
41 is provided, and this check valve 341 only allows flow of hydraulic oil from the oil passage 40a to the hydraulic pressure chamber 38. Further, the valve-side piston 34 is provided with first and second variable orifices 34a and 34b, as shown in FIG. These orifices 34a, 34b, together with the fixed orifice 33c, are located at a hydraulic buffer start position P (at the upper end of the annular recess 33e) set in the middle of the cylinder hole 33a when the valve-side piston 34 operates in the valve-closing position (raises). ) constitutes a hydraulic oil return amount control mechanism that exhibits a function of limiting the amount of hydraulic oil returned to the oil passage 40a in response to the upper end (rear end) of the valve-side piston 34 passing through.

According to the above-mentioned hydraulic oil return amount limiting mechanism, the first and second variable Since the orifices 34a and 34b are fully open with respect to the annular oil passage 33d, the lift amount of the intake valve 22 decreases relatively rapidly (the valve closes at a relatively high speed). Thereafter, as the valve-side piston 34 rises, the opening area of the first variable orifice 34a and then the second variable orifice 34b with respect to the annular oil passage 33d decreases, and as a result, the leakage amount of hydraulic oil also decreases, so that the intake valve The valve closing operation speed of 22 gradually decreases. Furthermore, after the lower end of the second variable orifice 34b passes through the hydraulic buffer start position P, the hydraulic oil is returned to the oil passage 40a only by the fixed orifice 33c, and the intake valve 22 slowly moves toward the valve seat 21.
Sit on a. Note that the check valve 341 is in a closed state after the upper end of the valve-side piston 34 passes through the hydraulic buffer start position P.

On the other hand, the hydraulic release mechanism 31
and an oil passage 41 connecting the oil supply gallery 42 and the oil passage 4
1, a feed valve 43 and a check valve 44 arranged in the oil passage 41, and an accumulation circuit 41a defined by these valves 43, 44 and the spill valve 45. The main component is an accumulator 46 for maintaining oil pressure at a predetermined value. The oil supply gallery 42 is provided to supply hydraulic pressure to a hydraulically driven valve unit provided for each cylinder, and is connected to an oil pump 47.
It is connected to the. The oil pump 47 supplies hydraulic oil in an auxiliary oil pan 48 provided in the cylinder head 21 to the oil supply gallery 42 as a hydraulic pressure within a predetermined range. Note that the hydraulic oil supplied to the oil supply gallery 42 may be supplied by an oil pump from an oil pan provided at the bottom of the crankcase (not shown).

The spill valve 45, as shown in FIG.
It consists of a control valve section 100 and an electromagnetic drive section 200 that drives the control valve section 100, and the control valve section 100 includes:
The valve housing 101 has an oil passage 41 and an accumulation circuit 41a.
A main valve body 102 that can switch between communication and cutoff is slidably fitted, and a pilot valve 103 that controls opening and closing movement of the main valve body is provided. It is connected to the control valve section 100 to be driven to open and close. That is, the casing 2 of the electromagnetic drive section 200
A valve housing 101 of a control valve section 100 is connected to 01.

The main valve body 102 is formed into a cylindrical shape with a bottom. The main valve body 102 is slidably fitted into the valve housing 101 while applying the hydraulic pressure of the passage 41 in the valve opening direction to the front surface of the main valve body 102. A chamber 104 is formed. Moreover, a spring 105 is housed in the pilot chamber 104, which biases the main valve body 102 in a direction to cut off the passage 41 and the accumulator circuit 41a. Therefore, the oil pressure in the passage 41 acts on the main valve body 102 in the valve opening direction, and the oil pressure in the pilot chamber 104 and the spring force of the spring 105 act on the main valve body 102 in the valve closing direction. Furthermore, the main valve body 102 has a passage 41 in the pilot chamber 1.
An orifice 106 is provided that communicates with 04.

The pilot valve 103 is interposed between the pilot chamber 104 and the auxiliary oil pan 48, and is biased by a spring 107 in a direction to cut off the pilot chamber 104 and the oil pan 48. . Further, the electromagnetic drive unit 200 includes a solenoid 202 and a solenoid 20
The movable core 203 is biased by a spring 204 having a smaller spring load than the spring 107 in the direction of coaxially abutting the upper end of the pilot valve 103. When the solenoid 202 is energized, the movable core 203 presses the pilot valve 103 in the downward direction against the spring force of the spring 107 to bring the pilot valve 103 to the closed position, and the solenoid 202 is demagnetized. The pilot valve 103 moves upward while pushing the movable core 203 by the spring force of the spring 107, and opens.

In such a spill valve 45, when the solenoid 202 of the electromagnetic drive unit 200 is demagnetized, the pilot valve 103 opens and the hydraulic oil in the pilot chamber 104 is led out to the auxiliary oil pan 48. Therefore, main valve body 1
The oil pressure acting on both sides of the valve 02 is unbalanced, and the opening force due to the oil pressure of the passage 41 acting on the front surface overcomes the oil pressure of the pilot chamber 104 and the valve closing force of the spring 105, causing the spill valve 45 to open. The valve operates.

When the pilot valve 103 is closed by the excitation of the solenoid 202, the hydraulic pressure in the passage 41 acts on the pilot chamber 104 through the orifice 106, and the main valve body 10
2 operates in the valve closing direction, and the spill valve 45 enters the closed state.

The solenoid 202 is connected to the ECU 2, and demagnetization/excitation is controlled by a control signal from the ECU 2.

Returning to FIG. 2, the accumulator 46 maintains the oil pressure in the accumulator circuit 41a at a predetermined pressure.
A cap 463 provided in the middle of the accumulator circuit 41a and having a cylinder hole 461 bored in the block 32 and an air hole 462, a piston 464 slidably fitted in the cylinder hole 461, and the cap 463 and the piston 46
4 and a spring 465 compressed between the spring 465 and the spring 465.

Hydraulic drive mechanism 30 configured as described above
The operation of the hydraulic pressure release mechanism 31 will be explained below.

The spill valve 4 is activated by a control signal from the ECU 2.
When the solenoid 202 of No. 5 is energized, the spill valve 45 is closed, and the oil pressure in the oil pressure generation chamber 39, oil passage 40, and working oil pressure chamber 38 of the hydraulic drive mechanism 30 is maintained at high pressure (a predetermined value or higher). The intake valve 22 is driven to open and close according to the profile of the cam 27. Therefore, the valve operating characteristics (relationship between crank angle and valve lift amount) in this case are as shown by the solid line in FIG.

On the other hand, when the solenoid 202 of the spill valve 45 is demagnetized by a control signal from the ECU 2 when the intake valve 22 is opened, the spill valve 45 becomes open, and the oil pressure generation chamber 39 of the hydraulic drive mechanism 30 and the oil The oil pressure in the passage 40 and the hydraulic pressure chamber 38 decreases, and the intake valve 22 begins to close regardless of the profile of the cam 27. At this time, the hydraulic oil return amount limiting mechanism slows down the closing speed of the intake valve 22 from the middle of the valve closing operation, and the intake valve 22 closes at the valve seat 21a.
Sit down gently. The valve operating characteristics in this case are shown by the broken line in FIG. That is, in the same figure, the crank angle θ
When the solenoid 202 is demagnetized by turning OFF, the intake valve 22 starts closing operation with a slight delay from θOFF (θ=θST), and reaches the valve closing completion state at θ=θIC.

As described above, by opening and closing the spill valve 45 according to the control signal from the ECU 2 and disabling the action of the hydraulic drive mechanism 30 when the spill valve 45 is opened, the timing at which the intake valve 22 starts closing can be arbitrarily set. Can be set to . As a result, it becomes possible to control the amount of intake air in each cylinder using the control signal from the ECU 2.

In this embodiment, the exhaust valve side is also provided with a hydraulically driven valve unit similar to the intake valve side (not shown), but the exhaust valve side is a normal valve that closes at a fixed timing according to the cam profile. It is also possible to use a variable valve timing mechanism that can set multiple valve opening/closing timings.

FIGS. 7 and 8 are flowcharts of programs for determining the fuel injection timing by the fuel injection valve 14, and FIGS. 9 to 13 are diagrams for explaining the injection timing determination method using these programs.

FIGS. 9 to 13 all focus on a specific cylinder of the engine (in the illustrated example, cylinder #1), and show the intake valve lift curve (each figure (a)) and the intake stroke (each figure (b)). ), injection stage (each figure (c)), injection execution range (each figure (d)
) and injection control signal (each figure (e)). In the lift curve of the intake valve (each figure (a)), the broken line shows the lift curve according to the cam profile when the hydraulic pressure release mechanism 31 is not operated at all, and the solid line shows the lift curve when the hydraulic pressure release mechanism 31 is activated depending on the engine operating state. It shows the lift curve when activated.

The injection stage (each figure (c)) is one revolution of the crankshaft (between θ1 and θ2) divided into 12 stages (stage 0 to stage 11), and the CR
It is determined based on the output of the K sensor 5.

The method for determining the fuel injection timing will be explained below with reference to FIGS. 7 to 13.

In step S1 of FIG. 7, the injection end stage (injection end time) INJSTGF is calculated by the program shown in FIG.

In step S11 of FIG. 8, first, the target valve closing timing θICOBJ of the intake valve (FIGS. 9(a) to 13(a)
) is the target value for the intake valve closing completion time, and is calculated as follows. In addition, FIGS. 9(a) to 13(
In a), θICOBJ indicates the time immediately before the lift amount of the intake valve becomes 0, and this is because almost no intake is performed immediately before the intake valve completely closes.

As shown in FIG. 6, the actual valve closing timing (hereinafter referred to as "actual valve closing timing") θIC of the intake valve is basically the timing at which the solenoid 202 of the hydraulic pressure release mechanism 31 is demagnetized (hereinafter referred to as "actual valve closing timing"). The actual valve closing timing θIC varies depending on the engine speed NE, the temperature of the hydraulic oil in the hydraulically driven valve unit, etc. even if the valve closing instruction timing θOFF is the same. . Therefore, in this embodiment, the reference value of the target valve closing timing θICOBJ is calculated based on the valve closing instruction timing θOFF, and by correcting this according to the engine rotation speed NE and the hydraulic oil temperature Toil, the target valve closing timing is calculated. θICOBJ is calculated.

Note that the valve closing instruction timing θOFF is based on the reference value set based on the engine speed NE and the accelerator opening θACC, and the intake temperature TA, atmospheric pressure PA, hydraulic oil temperature Toil, hydraulic pressure Poil, etc., and the lift. It is calculated by correcting according to the sensor detection value Lft.

Further, the target valve closing timing θICOBJ may be corrected based on the detected value Lft of the lift sensor.

Returning to FIG. 8, in step S12, the determination closing timing θref (FIGS. 9(a) to 12(a)
(see) is calculated using the following formula (1). Note that the smaller the value of the determined closing timing θref, the more frequently fuel injection is performed during the intake stroke.

θref=θ0+Δθ1+Δθ2+Δθ3
...(1) θ0 is a reference value set, for example, at 60° after the top dead center (TDC1 in FIG. 9). Δθ1
is set, for example, as shown in FIG. 14(a) according to the engine water temperature TW. When the engine water temperature TW is low, the amount of fuel injected into the intake pipe that adheres to the intake port wall increases, so it is desirable to perform fuel injection during the intake stroke when there is air flow within the intake port. Therefore, Δθ1 is set to decrease (increase in the negative direction) as the engine water temperature TW decreases.

Δθ2 is set, for example, as shown in FIG. 14(b) according to the accelerator opening θACC. The smaller the accelerator opening θACC, the slower the intake flow velocity.
It is desirable to perform fuel injection before the start of the intake stroke. Therefore, Δθ2 is set to increase as the accelerator opening degree θACC decreases.

Δθ3 is a correction term that is set according to other engine operating conditions (for example, engine speed NE; intake air temperature TA, oil temperature Toil).

Note that the reference value θ0 is not set as a constant value, but is set depending on the engine operating condition (for example, when the engine is running at high speed, the intake flow velocity is high, so the frequency of injection during the intake stroke is increased). You may also do so.

Furthermore, the method for calculating the θref value is not limited to the above method; for example, a reference value is read out from a map set according to the engine coolant temperature TW and the accelerator opening θACC, and the calculation method is calculated according to other engine operating conditions. The correction may be made by

Returning to FIG. 8, in step S13, the target valve closing timing θICOBJ is determined to be the determined closing timing θre.
Determine whether it is smaller than f and the answer is affirmative (YES)
That is, when θICOBJ<θref holds true, the injection end stage INJSTGF is set to stage 5 (step S14), and this program is ended. As a result, the engine is in a low load state (
9 corresponds to the idle state), then θI
Since COBJ<θref holds, the injection end timing θI
E is set to stage 5 within the injection possible range (FIG. 2(d)).

When the answer to step S13 is negative (NO), that is, when θICOBJ≧θref holds, a parameter STGIC indicating where in the injection stage the target valve closing timing θICOBJ is located is determined (step S15).
), injection end stage INJSTGF (STGIC-
I) (step S16), this program is ended. Here, I is usually set to a value of 1, but it can be set to a value depending on the engine speed NE, engine water temperature TW, etc. (for example,
It may be set to values 2, 3, etc.).

In steps S15 and S16, when the engine is in a medium load or high load state as shown in FIG. 11 or 12, θICOBJ≧θref holds true, so the injection end timing θIE is equal to the target valve closing timing θICO.
Injection stage with BJ (in the case of Fig. 11, stage 8,
It is set to the stage (stage 7 in FIG. 11 and stage 9 in FIG. 12) one stage before (I=1) (stage 10 in FIG. 12).

Returning to FIG. 7, in step S2, TOU
Determine whether T/CRME is divisible by an integer. Here, TOUT is the valve opening time of the fuel injection valve 14 that is set according to the engine operating state, and CRME is CRK
This is the generation interval of the output pulse of the sensor 5, that is, the crank angle for one injection stage converted into time (hereinafter referred to as "unit crank angle time").

If the answer to step S2 is affirmative (YES), the injection start stage INJSTG0 is calculated using the following equation (2) (step S3).

INJSTG0=INJSTGF-((TOUT/
CRME quotient) - 1)...(2) On the other hand, when the answer to step S2 is negative (NO), the injection start stage INJST
G0 is calculated using the following equation (3) (step S4).

INJSTG0=INJSTGF-(TOUT/C
RME quotient)...(3) Here, (TOUT/CRME quotient) in the above formulas (2) and (3) is TOUT/CRM
It means the integer part of the operation result of E.

According to the above steps S2 to S4, as shown in FIG. 13, for example, the injection end stage INJSTGF
is stage 9 and the engine speed NE is 5000
rpm (at this time CRME=1msec), TO
When UT=3.5msec, TOUT/CRME is
3.5/1, which is not divisible by an integer and the quotient is 3, so the injection start stage INJST0 is set to INJST0 by equation (3).
JST0=9-3=6. Therefore, the injection start timing θIS is as shown in FIG. 13(e).
This is set at the start of stage 6, as shown by the broken line in .

[0064] Also, under the same conditions as above, TOUT=6m
sec, TOUT/CRME is 6/1=6
, that is, it is divisible by an integer and the quotient is 6, so the injection start stage INJST0 is determined by equation (2) as INJST0=9.
-(6-1)=4. Therefore, the injection start timing θIS is as shown in FIG. 13(e).
This is set at the start of stage 4, as shown by the solid line.

Injection start timing θIS in FIGS. 9 to 12
is also set in the same manner as above.

According to the programs shown in FIGS. 7 and 8, in low load and low rotation conditions including idling, fuel injection is completed before the start of the intake stroke, so the injected fuel is almost completely sucked into the cylinder. The combustion state can be stabilized. In addition, under high load conditions, fuel injection is performed during the intake stroke, so fuel is drawn in at a high intake flow rate.
The combustion state can be stabilized by improving the fuel intake delay, and the charging efficiency can be improved by cooling the fuel.

[0067]

As described in detail above, according to the present invention, the injection end timing of the fuel injection means is determined either before the start of the intake stroke or during the intake stroke, depending on the timing when the intake valve completes closing. Since the injection start timing is determined according to the determination result, the fuel injection timing is appropriately controlled in response to changes in the operating state of the intake valve due to changes in engine load, stabilizing the combustion state and improving filling. Efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall configuration of an internal combustion engine and its control device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a hydraulically driven valve unit.

FIG. 3 is an enlarged view of a part of FIG. 2;

FIG. 4 is a perspective view of a valve-side piston.

FIG. 5 is a cross-sectional view of the spill valve.

FIG. 6 is a diagram showing the operating characteristics (lift curve) of the intake valve.

FIG. 7 is a flowchart of a program for determining a fuel injection start stage and end stage.

FIG. 8 is a flowchart of a program for determining a fuel injection end stage.

FIG. 9 is a diagram for explaining fuel injection timing during idling.

FIG. 10 is a diagram for explaining fuel injection timing at low load.

FIG. 11 is a diagram for explaining fuel injection timing during medium load.

FIG. 12 is a diagram for explaining fuel injection timing during high load.

FIG. 13 is a diagram illustrating means for determining an injection start stage.

[Fig. 14] Correction term (Δ
θ1, Δθ2); FIG.

[Explanation of symbols]

1 Internal combustion engine 2 Electronic control unit (ECU) 20 Hydraulic drive valve unit 27 Cam 30 Hydraulic drive mechanism 31 Hydraulic release mechanism

Claims (4)

[Claims] Claims: 1. An internal combustion engine comprising: a valve control means for controlling the intake air amount of the engine by changing the opening period of the intake valve of the internal combustion engine; and a fuel injection means for injecting fuel into the intake pipe of the engine. In the engine control device, the injection end timing determining means determines the injection end timing of the fuel injection means to be either before the start of the intake stroke or during the intake stroke according to the closing completion timing of the intake valve; 1. A control device for an internal combustion engine, comprising: injection start timing determining means for determining the injection start timing of the fuel injection means depending on whether the timing is before the start of the intake stroke or during the intake stroke. 2. The injection end timing determining means sets the injection end timing to before the start of the intake stroke when the closing completion timing of the intake valve is earlier than a predetermined determination time set according to the operating state of the engine. 2. The control device for an internal combustion engine according to claim 1, wherein, on the other hand, when the valve closing completion timing is later than the predetermined determination timing, the injection termination timing is set to be during an intake stroke. 3. The intake valve closing completion timing is a value calculated in accordance with engine operating parameters including at least an engine rotational speed and a parameter representing a driver's request to the engine. 3. A control device for an internal combustion engine according to 1 or 2. 4. The intake valve includes a lift sensor that detects a lift amount of the intake valve, and the closing completion timing of the intake valve is a value calculated based on the lift amount detected by the lift sensor. The control device for an internal combustion engine according to claim 1 or 2.