JP2884854B2 - Valve timing control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device configured to make each opening and closing timing of an intake valve and an exhaust valve variable according to the operating state of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as this kind of technique, for example, a "residual gas control device for an internal combustion engine" disclosed in Japanese Patent Application Laid-Open No. 58-214610 is known. In this technique, each of an intake valve and an exhaust valve is driven to open and close, and the opening and closing timing thereof is made variable.
By controlling the opening and closing timings of the intake valve and the exhaust valve variably, the amount of residual exhaust gas confined in the combustion chamber is maintained optimally, and at the same time, the pumping loss during the intake stroke is reduced and the engine output is reduced. NOx is effectively reduced without deteriorating fuel efficiency.

That is, in this technique, the exhaust valve is set to be closed before the exhaust top dead center and the intake valve is opened after the top dead center in a low load region of the engine. As a result, in the low load range, the valve overlap between the opening of the intake valve and the opening of the exhaust valve is eliminated, and a portion of the burned gas is contained as residual exhaust in the combustion chamber as it is to recirculate the internal exhaust gas. Then, by mixing the residual exhaust gas with the air-fuel mixture to be sucked next, heat is given to the air-fuel mixture, and NOx is effectively reduced without impairing combustion stability. At the same time, since the intake air amount is controlled by controlling the opening and closing timing of the intake valve, the pumping loss is reduced to improve the fuel efficiency. Further, above the middle load range of the engine, the opening of the intake valve and the exhaust valve is set so that the valve overlap becomes large. And above the medium load range,
The residual exhaust amount is reduced and the intake air amount is increased. In this way, a sufficient air-fuel mixture for the engine to exhibit a high output in the middle load region or higher is ensured.

[0004]

However, in the above prior art, internal exhaust gas recirculation is realized by closing the exhaust valve before the exhaust top dead center only in the low load range.
Ox was reduced. Above the medium load range, the valve overlap is increased to reduce the amount of residual exhaust, and the pumping loss is reduced to increase the amount of intake air. Therefore, in the operation range above the medium load range,
It is no longer possible to secure the amount of residual exhaust required to reduce NOx to a predetermined level.
In order to reduce x, it was necessary to recirculate exhaust gas from the outside.

Incidentally, the combination of the opening and closing timings of the intake valve and the exhaust valve for maintaining the ratio of the residual exhaust gas in the combustion chamber at an optimum level irrespective of the change in the load of the engine is as follows.
Several are known to exist. Therefore, by combining such opening and closing timings of the intake valve and the exhaust valve, it is possible to improve the fuel efficiency at a medium load or higher while securing a target residual exhaust amount required for reducing NOx over the entire load range. Was desired.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to always achieve both improvement in fuel efficiency and reduction in NOx without recirculating exhaust gas from the outside to the internal combustion engine. It is an object of the present invention to provide a valve timing control device for an internal combustion engine that can perform the above.

[0007]

In order to achieve the above object, the present invention provides a valve timing control device for an internal combustion engine.
The intake and exhaust valves of the internal combustion engine
Valve timing change to change the lube timing separately
Means and the ratio of residual exhaust gas in the combustion chamber of the internal combustion engine.
Valves of both valves that are almost constant regardless of the change in related load
Of the timing combinations, during the compression stroke of the internal combustion engine
At which the intake valve close timing is
Function of engine load with the combination of lube timing
Storage means for storing the engine load in advance, and the engine load of the internal combustion engine.
Detecting means to detect, detected engine load and storage means
Valve timing change based on stored function
The valve timing of both valves, which is changed by
And setting means for setting each operation.
You.

[0008]

According to the above arrangement, when the engine load changes.
However, the residual ratio in the combustion chamber is almost the entire engine load
, And keeps the NOx amount in the exhaust gas low.
A sufficient amount of residual exhaust to reduce
You. Further, the exhaust residual ratio is kept almost constant in this manner.
Also, close the intake valve during the compression stroke.
The combination of each valve timing that causes the slowest
Suction that is returned to the intake system during the compression stroke because it is selected
The amount of air becomes relatively large. As a result, a predetermined amount of suction
To get the specified engine output by introducing the incoming air into the combustion chamber
Of the intake system such as increasing the opening of the throttle valve
An operation to decrease the aperture amount is inevitably performed.
You. Therefore, the suction in the intake system over almost the entire area of the engine load
The negative air pressure drops (increases in absolute pressure) and the pumping
Is effectively reduced.

[0009]

[0010]

[0011]

EXAMPLES Hereinafter, will be described in detail based on an embodiment embodying the valve timing control apparatus for an internal combustion engine in the present invention in FIGS. 1-9.

FIG. 1 is a schematic diagram illustrating a gasoline engine 1 (only one cylinder is shown) as an internal combustion engine mounted on a vehicle according to this embodiment. A piston 3 is provided in a cylinder bore 2a formed in a cylinder block 2 of the engine 1 so as to be vertically movable. The piston 3 is connected to a crankshaft (not shown) via a rod 4. A space surrounded by the piston 3, the cylinder bore 2a, and the cylinder head 5 covering the upper side of the bore 2a is a combustion chamber 6.

An intake passage 7 and an exhaust passage 8 are provided in the combustion chamber 6 so as to communicate with each other. An intake valve 9 for opening and closing is mounted on an intake port 7a opening to the combustion chamber 6 of the intake passage 7. An exhaust valve 8 for opening and closing is provided in an exhaust port 8a opening to the combustion chamber 6 of the exhaust passage 8.
Is assembled.

Outside air is introduced into the intake passage 7 via an air cleaner (not shown). An injector 1 for fuel injection is provided near the intake port 7a in the intake passage 7.
1 is provided so that fuel is taken into the intake passage 7. As is well known, fuel at a predetermined pressure is supplied to the injector 11 from a fuel tank (not shown) by the operation of a fuel pump.
Then, a mixture of fuel and outside air injected from the injector 11 and taken into the intake passage 7 is introduced into the combustion chamber 6 through the intake port 7a when the intake valve 9 is opened. Further, the mixture introduced into the combustion chamber 6 explodes.
By the combustion, the driving force of the engine 1 is obtained via the piston 3, the crankshaft, and the like. Further, the burned gas burned in the combustion chamber 6 is discharged from the exhaust port 8a to the outside through the exhaust passage 8 when the exhaust valve 10 is opened.

In the middle of the intake passage 7, the accelerator pedal 1
2 is provided with a throttle valve 13 which is opened and closed in conjunction with the operation of Step 2. When the throttle valve 13 is opened and closed, the amount of air taken into the intake passage 7 is adjusted.

In the vicinity of the throttle valve 13, a throttle sensor 14 for detecting the throttle opening TA is provided. A surge tank 15 for smoothing the pulsation of the intake air is provided downstream of the throttle valve 13.
Is provided. Further, on the upstream side of the throttle valve 13, there is provided a known air flow meter 16 for detecting an intake air amount Q taken into the intake passage 7 from the outside.

Next, a valve operating mechanism for the intake valve 9 and the exhaust valve 10 will be described. An intake valve 9 and an exhaust valve 10 are stems 9a, 10 extending upward, respectively.
The valve springs 17 and 18 and the valve lifters 19 and 20 are mounted on the upper portions of the stems 9a and 10a, respectively. Cams 21a and 22a are provided on the respective valve lifters 19 and 20 so as to engage with each other. The cams 21a and 22a are formed on the camshaft 21 on the intake side and the camshaft 22 on the exhaust side supported by the cylinder head 5 by the number of all cylinders. The intake valve 9 and the exhaust valve 10 are urged upward by the urging forces of the valve springs 17 and 18 and in a direction to close the intake port 7a and the exhaust port 8a. In this biased state, each stem 9
The upper ends of a and 10a are always in contact with the cams 21a and 22a via the valve lifters 19 and 20.

In this embodiment, an intake-side variable valve timing mechanism (hereinafter simply referred to as "intake-side VVT") 23 is provided at the tip of the intake-side camshaft 21 in order to make the opening / closing timing of the intake valve 9 variable. A timing pulley assembly 24 and a step motor 25 are provided. The step motor 25 includes a plurality of electromagnetic coils, and sequentially selects an electromagnetic coil to be excited among them, so as to rotate in a predetermined direction at each step. On the other hand, in order to make the opening / closing timing of the exhaust valve 10 variable, a timing pulley constituting an exhaust-side variable valve timing mechanism (hereinafter simply referred to as “exhaust-side VVT”) 26 is provided at the tip of the exhaust-side camshaft 22. An assembly 27 and an electromagnetic actuator 28 are provided. The electromagnetic actuator 28 has an output shaft which is protruded and retracted by exciting and demagnetizing an electromagnetic coil to turn on / off the exhaust side VVT 26. These timing pulley assemblies 24 and 27 are drivingly connected to a crankshaft via a timing belt (not shown).

Therefore, when the engine 1 is operated, power is transmitted from the crankshaft to each of the timing pulley assemblies 24 and 27 via the timing belt.
Each of the camshafts 21 and 22 is driven to rotate, and each of the cams 21a and 22a is rotated. The valve lifters 19 and 20 are pressed against the urging forces of the valve springs 17 and 18 according to the profiles of the rotated cams 21a and 22a, so that the intake valve 9 and the exhaust valve 10 move downward. The intake port 7a and the exhaust port 8a are respectively opened. The basic opening / closing timing of the intake valve 9 and the exhaust valve 10 is, as is well known, a vertical movement accompanying four strokes (the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke) of the piston 3 during two rotations of the crankshaft. Is set in advance in relation to. Here, when the intake port 7a is opened by the downward movement accompanying the intake stroke of the piston 3, that is, when the intake valve 9 is opened, the combustion chamber 6
The mixture is inhaled. When the exhaust port 8a is opened by the upward movement of the piston 3 during the exhaust stroke, that is, when the exhaust valve 10 is opened, the burned gas is discharged from the combustion chamber 6 to the exhaust passage 8.

The intake side VVT 23 is driven and controlled to change the basic opening / closing timing of the intake valve 9 in accordance with the operating state of the engine 1 in particular, particularly the load state. The rotation phase of each cam 21a is appropriately changed. By changing the basic opening / closing timing of the intake valve 9 by the intake side VVT 23, the valve overlap between the intake valve 9 and the exhaust valve 10 is changed.

The exhaust side VVT 26 is connected to the exhaust valve 10.
Is controlled to change the basic opening / closing timing according to the operating state of the engine 1 at each time, particularly the load state, so that the rotational phase of the camshaft 22, and thus the rotation of each cam 22a, is changed appropriately. Has become. By changing the basic opening / closing timing of the exhaust valve 10 by the exhaust side VVT 26, the valve overlap between the intake valve 9 and the exhaust valve 10 is changed.

In order to ignite the air-fuel mixture introduced into the combustion chamber 6, an ignition plug 2 is mounted on a cylinder head 5 at the center of the cylinder.
9 is fixed, and the discharge part 29 a is disposed in the combustion chamber 6. This spark plug 29 is connected to the distributor 3
It is driven based on the ignition signal distributed at zero. The distributor 30 synchronizes the high voltage output from the igniter 31 with the crank angle of the engine 1 and
9 for distribution. Distributor 3
0 is a rotor 3 that rotates in conjunction with the rotation of the engine 1
0a is provided, and a rotation speed sensor 32 for detecting the engine rotation speed NE from the rotation of the rotor 30a is provided. Further, the distributor 30 is provided with a cylinder discrimination sensor 33 that detects a reference position of the crank angle of the engine 1 at a predetermined ratio in accordance with the rotation of the rotor 30a and outputs a reference position signal G.

In addition, a water temperature sensor 34 for detecting the temperature (cooling water temperature) THW of the cooling water of the engine 1 is attached to the cylinder block 2. In the middle of the exhaust passage 8, an oxygen sensor 35 for detecting the oxygen concentration in the exhaust gas is mounted.

[0024] In this embodiment, by the throttle sensor 14 and the rotational speed sensor 32 is detecting means that detect the load state of the engine 1 is constructed. As shown in FIG. 1 , the throttle sensor 14, the air flow meter 16, the rotational speed sensor 32, the cylinder discriminating sensor 3,
3. The water temperature sensor 34, the oxygen sensor 35, and the like are electrically connected to the input side of an engine electronic control unit (hereinafter simply referred to as "engine ECU") 40. Also, this engine E
The injector 11 and the igniter 31 described above are electrically connected to the output side of the CU 40. And
The engine ECU 40 suitably controls the injector 11 and the igniter 31 based on the output signals from the air flow meter 16 and the sensors 14, 32 to 35.

In this embodiment, the engine ECU 40
Is a control device that mainly controls the fuel injection amount control and the ignition timing control of the engine 1. In addition to this, in this embodiment,
As shown in FIG. 1 , the intake-side VVT 23 and the exhaust-side VVT
A VVT ECU 41 for controlling the driving of the motor 26 is provided. The VVT ECU 41 determines the direction and amount of rotation of the output shaft of the step motor 25,
It controls the emergence of the output shaft. Therefore, the input side of the VVT ECU 41 is connected to the engine ECU 4.
From 0, the detected values of the throttle opening TA and the engine speed NE are input as data signals. In addition, VVTE
The CU 41 determines the opening / closing timing of the intake valve 9 and the exhaust valve 10 according to the load state of the engine 1 at each time based on the input data signal and the like.
5 and a valve timing control signal for suitably controlling the electromagnetic actuator 28.

Next, the aforementioned engine ECU 40 and V
The configuration of VTECU41, be described with reference to the block diagram of FIG. 2, 3. FIG. 2 is a block diagram illustrating an electrical configuration of the engine ECU 40. Engine ECU
Reference numeral 40 denotes a central processing unit (CPU) 42, a read-only memory (RO) which stores a predetermined control program and the like in advance.
M) 43, a random access memory (RAM) 44 for temporarily storing the operation results and the like of the CPU 42, a backup RAM 45 for storing previously stored data, and the like, and a bus connecting these components with the external input circuit 46 and the external output circuit 47. 48, it is constituted as a theoretical operation circuit.

The external input circuit 46 includes the above-described throttle sensor 14, air flow meter 16, rotation speed sensor 3
2. The cylinder discrimination sensor 33, the water temperature sensor 34, and the oxygen sensor 35 are respectively connected. On the other hand, the external output circuit 47 includes the injector 11, the igniter 31, and the VV
The TECUs 41 are respectively connected.

Then, the CPU 42 controls the air flow meter 16 and each sensor 1 input through the external input circuit 46.
Signals from 4, 32 to 35, etc. are read as input values.
When reading the input values, the input values from the throttle sensor 14, the air flow meter 16, the water temperature sensor 34, and the oxygen sensor 35 are subjected to analog / digital conversion processing in the external input circuit 46. In the external input circuit 46, input values from the rotation speed sensor 32, the cylinder discrimination sensor 33, and the like are subjected to waveform shaping processing. Then, the CPU 42 controls the air flow meter 16
The injector 11 and the igniter 31 are preferably controlled based on input values read from the sensors 14, 32 to 35, and the like.

The CPU 42 outputs the throttle opening degree TA and the engine speed NE among the signals read as input values from the air flow meter 16 and the sensors 14, 32 to 35 via the external input circuit 46 to an external output circuit. 47
And outputs it as a data signal to the VVT ECU 41 via the.

FIG. 3 is a block diagram illustrating an electrical configuration of the VVT ECU 41. The VVT ECU 41 includes a microprocessing unit (MPU) 50 and an intake-side V
A ROM 51 previously storing a predetermined control program and the like for the VT 23 and the exhaust side VVT 26 and the like, a RAM 52 for temporarily storing the calculation result of the MPU 50 and the like, and these parts, an input / output port 53 and an output port 54 are connected by a bus 55. It is configured as a connected theoretical operation circuit.
The VVT ECU 41 includes a clock generator 56 that generates a periodic clock pulse, and the generator 56 supplies a clock pulse to the MPU 50. Further, the VVT ECU 41 includes a latch circuit 57, a gate 58, and a drive circuit 59 connected to the output port 54.

The input / output port 53 is connected to the engine ECU 40. The gate 58 has a step motor 2
5 is connected to the drive circuit 59 and the electromagnetic actuator 2
8 are connected.

The MPU 50 reads, as input values, signals such as the throttle opening TA and the engine speed NE input through the input / output port 53, and based on the read input values, controls the stepping motor 25 and the electromagnetic actuator 28. Control appropriately. That is, the MPU 50 calculates and determines the direction to rotate the step motor 25 and the number of steps according to the control program stored in the ROM 51 based on the read input value, and latches the calculation result as a valve timing control signal via the output port 54. Output to the circuit 57. Latch circuit 57 receives the valve timing control signal and applies a gate 58 to execute it.
Are output in accordance with a predetermined sequence. Then, the gate 58 selects an electromagnetic coil to be excited and drives the step motor 25 according to the opening / closing command.

The MPU 50 determines whether or not to drive the electromagnetic actuator 28 according to a control program stored in the ROM 51 based on the read input value, and uses the determined result as a valve timing control signal in the drive circuit 5.
9 to drive the electromagnetic actuator 28.

[0034] Next, will be described in detail in accordance with FIG. 4 the configuration of the intake side VVT23 described above. The intake side camshaft 21 for driving the intake valve 9 is rotatably supported by the cylinder head 5 by its cam journal 21b. At the tip of the camshaft 21, a timing pulley assembly 2 constituting the VVT 23 is provided.
4 and step 25 are provided. The timing pulley assembly 24 includes a pulley main body 62 having a plurality of external teeth 61 on the outer periphery, an inner cap 63 and a cylindrical gear 64 attached to the pulley main body 62.

That is, the pulley body 62 has a boss 62a and a circumferential wall 62b near the center thereof, and a space between the boss 62a and the circumferential wall 62b is a circumferential groove 62c. Helical teeth 62d are formed on the inner periphery of the circumferential wall 62b. The pulley main body 62 is mounted on the camshaft 21 with its boss 62a so as to be relatively rotatable.
On the other hand, the inner cap 63 includes a large cylindrical portion 63a and a small cylindrical portion 63b extending to the opposite side, and helical teeth 63c are formed on the outer periphery of the large cylindrical portion 63a. The inner cap 63 is fitted so that the large cylindrical portion 63a covers the boss 62a, and is attached to the pulley main body 62 so as to be relatively rotatable. Further, the inner cap 63 is fixed to the tip of the camshaft 21 so as to be integrally rotatable by a bolt 65 and a knock pin 66. Further, the cylindrical gear 64 is attached to the outer peripheral wall 6.
4a and an inner peripheral wall 64b.
4c is formed. Helical teeth 64d and 64e are formed on the inner and outer circumferences of the inner peripheral wall 64b, respectively.
A circumferential groove 64f is formed between a and the inner peripheral wall 64b.
The inner peripheral wall 64b of the cylindrical gear 64 and the circumferential groove 6
4f is a circumferential wall 62b and a circumferential groove 62 of the pulley body 62.
It is assembled in an uneven relationship with c.

In this assembled state, the helical teeth 62d, 63c, 64d, and 64e are meshed with each other. Due to the meshing relationship, the cylindrical gear 64 is relatively rotatable with the camshaft 21 by moving in the axial direction. I have. The timing pulley assembly 24 is drivingly connected to the crankshaft via a timing belt (not shown) mounted on the external teeth 61 of the pulley body 62.

Accordingly, by transmitting the driving force from the crankshaft to the timing pulley assembly 24, the pulley main body 62 and the inner cap 63 connected by the cylindrical gear 64 are integrally rotated. The camshaft 21 connected to the inner cap 63 is driven to rotate integrally.

The above-described step motor 25 is attached to the engine 1 by a bracket (not shown). The step motor 25 is for moving the cylindrical gear 64 in the axial direction. A worm gear 67 having a cylindrical shape and having teeth 67a on the outer periphery is attached to an output shaft thereof. The worm gear 67 is a small cylinder 6 of the inner cap 63.
3b so as to be rotatable relative to each other, and is disposed so as to pass through a hole 64c of the cylindrical gear 64. On the other hand, around the hole 64c of the cylindrical gear 64, a ring gear 68 having teeth 68a on its inner periphery is assembled by a ball bearing 69 so as to be relatively rotatable. The ring gear 68 is meshed on the outer periphery of the worm gear 67, and is movable in the axial direction by the rotation of the worm gear 67 due to the meshing relationship. In order to prevent the rotation of the ring gear 68, a long groove 6 extending in the axial direction is provided on the outer periphery of the ring gear 68 on the step motor 25 side.
8b are formed. At the same time, a detent member 70, which has a tubular shape and extends toward the timing pulley assembly 24, is attached to the casing of the step motor 25. On the inner periphery of the detent member 70, the aforementioned long groove 6 is provided.
A projection 70a engaging with the projection 8b is formed. And
Due to the relationship between the engagement of the projection 70a and the long groove 68b, the ring gear 68 is prevented from rotating, and is allowed to move only in the axial direction.

The oil passage 7 is provided inside the camshaft 21.
1 and 72 are formed, and lubricating oil is supplied to the inside of the timing pulley assembly 24 through the oil passages 71 and 72.

Accordingly, when the timing pulley assembly 24 and the camshaft 21 are integrally rotating, the step motor 25 is driven to rotate the worm gear 67 by a predetermined amount in a certain direction, whereby the ring gear 68 is rotated.
Is moved in the axial direction while being prevented from rotating on the worm gear 67. Accordingly, the cylindrical gear 64 is moved in the same axial direction, a relative rotation occurs between the pulley main body 62 and the camshaft 21, and the camshaft 21 is twisted. As described above, in the VVT 23 of this embodiment, the drive of the step motor 25 is controlled so that the cylindrical gear 6 is driven.
The position of the camshaft 21 in the axial direction is changed, so that the camshaft 21 is twisted. When the camshaft 21 is twisted, the opening / closing timing of the intake valve 9 is continuously changed, and the valve overlap is changed.

In this embodiment, the opening and closing timing of the intake valve 9 is changed from the opening timing (50 ° before top dead center) and the closing timing (20 ° after bottom dead center) to the opening timing (-10 ° before top dead center).・ Close timing (80 after bottom dead center)
°) continuously variable.

In this embodiment, the exhaust side VVT2
For the configuration of the timing pulley assembly 27 of No. 6,
The description is omitted because it is almost the same as that of the timing pulley assembly 24 described above. Also, the exhaust side VVT
In the timing pulley assembly 27, an electromagnetic actuator 28 is provided instead of the step motor 25 described above. And the electromagnetic actuator 2
When the exhaust side VVT 26 is turned on and off by the emergence of the output shaft 8, the opening / closing timing pulley of the exhaust valve 10 is changed in two stages, and the valve overlap is changed.

In this embodiment, the opening / closing timing of the exhaust valve 10 includes a closing timing (0 ° after top dead center) and an opening / closing timing.
And can timing (bottom dead center 40 °), (20 ° after top dead center) closing timing opening timing (bottom dead center 20
°).

Next, will be described in accordance with FIGS. 5-9 the operation of the valve timing control apparatus for an internal combustion engine configured as described above. FIG. 5 shows the intake side VVT 23 and the exhaust side VV.
It is a flowchart explaining the "VVT control routine" performed by the VVT ECU 41 in order to drive-control T26, and is performed by the periodic interruption for every predetermined time.

When the process proceeds to this routine, first, at step 101, the throttle opening TA and the engine speed NE detected by the throttle sensor 14 and the speed sensor 32 are read from the engine ECU 40, respectively.

Subsequently, at step 102, the previously read throttle opening TA and engine speed NE are read.
The basis of, referring to the intake load function fI a map as a parameter the values as shown in FIG. 6 (NE, T
A) is calculated, and the calculation result is set as the target step number Vst.

Here, the map shown in FIG. 6 is stored in the ROM 51 in advance. In this map, the combustion chamber is changed in accordance with changes in the throttle opening TA and the engine speed NE, that is, changes in the load of the engine 1. 6, an intake side VVT 23 and an exhaust side V
Among the drive timings of the VT 26, the intake load function fI (NE, TA) is set such that the closing timing of the intake valve 9 is the latest in each load region.

In step 103, the stepping motor 25 is deduced from the set target step number Vst.
Is set as the control step number STEP.

Next, at step 104, it is determined whether or not the control step number STEP is "0". Here, when the control step number STEP is “0”,
Step 1 is performed without driving the step motor 25.
Move to 14. Then, in step 114, based on the throttle opening TA and the engine rotational speed NE read earlier, referring to exhaust load function fE (NE maps to parameter the values as shown in FIG. 7,
TA) is calculated, and the calculation result is set as the excitation signal VE.

Here, the map shown in FIG. 7 is stored in the ROM 51 in advance. In this map, the change in the throttle opening TA and the engine speed NE, that is, the change in the load of the engine 1 causes the combustion chamber 6 to change. Intake-side VVT 23 and exhaust-side VV for obtaining the optimal target exhaust residual ratio
The exhaust load function fE (NE, TA) is set so as to be a combination of both drive timings of T26.

Subsequently, at step 115, the drive of the electromagnetic actuator 28 is controlled based on the excitation signal VE, that is, the drive of the exhaust side VVT 26 is controlled, and the subsequent processing is temporarily terminated.

On the other hand, if the control step number STEP is not "0" in step 104, step 10
In 5, it is determined whether or not the control step number STEP is larger than “0”, that is, whether or not the control step number STEP is a positive number. Here, the number of control steps STEP
Is a positive number, after resetting the control flag DIR to “0” in step 106,
Move to 09.

If the number of control steps STEP is a negative number in step 105, step 107
, The control flag DIR is set to "1".
In step 108, the number of control steps STEP
Is set as the new control step number STEP, and then the process proceeds to step 109.

Then, step 106 or step 10
In step 109 after shifting from step 8, it is determined whether or not the control flag DIR is "1". Here, if the control flag DIR is “1”, step 110
, The step motor 25 of the intake side VVT 23 is set to 1
After the step is reversed, the process proceeds to step 112. If the control flag DIR is “0”, the process proceeds to step 111 after the step motor 25 is rotated forward by one step in step 111.

After shifting from step 110 or step 111, in step 112, the number of control steps ST
A result obtained by subtracting “1” from EP is set as a new control step number STEP. In step 113, it is determined whether or not the new control step number STEP is “0”. Then, the new control step number ST
If the EP is not “0”, the process jumps to step 109 and repeats the processing of steps 109 to 113. That is, the drive control of the intake side VVT 23 is performed.

On the other hand, if the new control step number STEP is "0", the routine proceeds to step 114, where the control routine proceeds to step 114 based on the previously read throttle opening TA and engine speed NE. As shown in FIG. 7 , the exhaust load function fE (NE, TA) is calculated with reference to a map using those values as parameters, and the calculation result is set as the excitation signal VE. Then, Step 1
At 15, the drive of the electromagnetic actuator 28 is controlled based on the excitation signal VE, that is, the drive of the exhaust-side VVT 26 is controlled, and the subsequent processing is temporarily terminated.

As described above, the drive of the intake side VVT 23 and the exhaust side VVT 26 are controlled by the control of the step motor 25 and the electromagnetic actuator 28, respectively.
And the opening / closing timing of the exhaust valve 10 is controlled.

Here, as a result of controlling the opening / closing timing of the intake valve 9 and the exhaust valve 10 as described above, “200
Crankshaft torque in the engine speed NE 0rpm ", namely the intake valve 9 to the load equivalent shaft torque, for explaining the change of the closing timing of the exhaust valve 10 according to the graph of FIG. As is apparent from this graph, in this embodiment, the closing timing of the intake valve 9 is set to be late and the closing timing of the exhaust valve 10 is set to be early in a low load region. Further, the closing timing of the intake valve 9 is set to be as late as possible in the middle load range, and the closing timing of the exhaust valve 10 is set to be delayed. Further, the closing timing of the intake valve 9 is set as late as possible in the high load region, and the closing timing of the exhaust valve 10 is set earlier. Such setting of the closing timing is performed in substantially the same manner at the engine speed NE other than “2000 rpm”.

Accordingly, in this embodiment, since the closing timing of the intake valve 9 is relatively late in the low load range, the negative pressure in the intake passage 7 is reduced to reduce the pumping loss. Further, since the closing timing of the exhaust valve 10 is relatively early, the opening time of the exhaust valve 10 in the intake stroke is shortened, and the residual exhaust in the combustion chamber 6 is limited so as not to increase more than necessary. Furthermore, in the medium load range,
Since the closing timing of the intake valve 9 is relatively late,
Similarly, pumping losses are reduced. Also, exhaust valve 1
0 is relatively late, the combustion chamber 6
The residual exhaust at is increased. In addition, in the high load range,
Since the closing timing of the intake valve 9 is relatively late,
Pumping loss is reduced. Further, since the closing timing of the exhaust valve 10 is relatively early, residual exhaust in the combustion chamber 6 is increased.

FIG. 9 shows the result. FIG. 9 is a graph showing changes in the pumping loss and the residual exhaust ratio with respect to the shaft torque in comparison between the control result of the present embodiment and the result obtained by a normal cam. As is clear from this graph, regarding the pumping loss, it is understood that the control result of the present embodiment is relatively smaller than the result obtained by the normal cam. Further, it can be seen that the control result of the present embodiment is maintained at a substantially constant target level with respect to the residual exhaust ratio as compared with the result obtained by the normal cam. That is, according to the control result of this embodiment, the residual exhaust gas ratio can be maintained at substantially the target level over the entire load range, and the pumping loss can be reduced.

Therefore, according to the valve timing control device of the present embodiment, the residual exhaust gas ratio can be maintained at substantially the target level over the entire load region, so that the exhaust gas is not recirculated from the outside and the exhaust gas is recirculated over the entire load region. It is possible to realize internal exhaust gas recirculation over the entire area and reduce NOx. or,
Since the pumping loss can be made relatively small, the amount of air taken into the combustion chamber 6 can also be increased in the operation region above the medium load region, and the output of the engine 1 and the fuel efficiency can be improved. That is, it is possible to always improve the fuel efficiency and reduce the NO
x can be reduced at the same time.

It should be noted that the present invention is not limited to the above-described embodiment, and may be implemented as follows, with a part of the configuration being appropriately changed without departing from the spirit of the invention. (1) In the embodiment, although the intake side camshaft 21 and the exhaust side cam shaft 22 so as to interlock via the two timing Puglia Tsu Consequences 24, 27 and a timing belt, as shown in FIG. 1 0 The camshaft 21 on the intake side and the camshaft 22 on the exhaust side are interlocked via a pair of scissors gears 36 and 37, and a timing pulley assembly 24 and a step motor 25 are attached to the tip of the camshaft 21 on the intake side. Intake side V
The VT 23 may be provided, and the scissors gear 37 of the camshaft 22 on the exhaust side and the electromagnetic actuator 28 may constitute an exhaust VVT 38.

(2) In the above embodiment, the step motor 2
Although the intake-side VVT 23 using the drive source 5 and the exhaust-side VVT 26 using the electromagnetic actuator 28 as a drive source are employed, a hydraulically driven VVT may be employed.

(3) In the above embodiment, the present invention is embodied in the gasoline engine 1. However, the present invention can be embodied in a diesel engine.

[0065]

As described in detail above, according to the present invention,
Exhaust residue in the combustion chamber even when the engine load changes
The ratio is maintained almost constant over almost the entire engine load.
That is sufficient to reduce the amount of NOx in the exhaust
Exhaust will be secured. In addition, during the compression stroke
Relatively larger amount of intake air returned to the system
As a result, the throttle amount of intake air in the intake system is reduced
Intake over almost the entire engine load.
The intake negative pressure in the system is reduced, and pumping loss is effectively reduced.
Will be reduced. As a result, external
Over the entire engine load without exhaust recirculation
The specified NOx reduction effect at all times,
Fuel efficiency can be improved by reducing ping loss.
You.

[Brief description of the drawings]

FIG. 1 is a scorpion according to an embodiment of the present invention;
FIG. 2 is a schematic configuration diagram illustrating an engine.

FIG. 2 is an electrical configuration of an engine ECU according to one embodiment .
FIG.

FIG. 3 shows an electrical configuration of a VVT ECU according to one embodiment .
FIG.

FIG. 4 is a cross-sectional view showing a configuration of a VVT according to one embodiment.
is there.

FIG. 5 is executed by a VVT ECU in one embodiment .
Is a flowchart illustrating a “VVT control routine”.
is there.

FIG. 6 shows an engine speed and a throttle in one embodiment .
Predetermine the value of the intake load function using the opening as a parameter.
It is a map that can be obtained.

FIG. 7 shows an engine speed and a throttle in one embodiment .
Predetermine the value of the exhaust load function using the opening as a parameter.
It is a map that can be obtained.

FIG. 8 is a diagram illustrating an example of an axial load corresponding to an engine load;
Intake valve and exhaust valve closing timing for luk
6 is a graph for explaining the change of the graph.

FIG. 9 is a diagram illustrating an example of an axial load corresponding to an engine load.
Explains changes in pumping loss and residual exhaust gas rate
It is a graph to clarify.

FIG. 10 is a perspective view of another embodiment embodying the present invention;
FIG. 2 is a plan view illustrating a configuration of a lubrication timing control device.
You.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 6 ... Combustion chamber, 7 ... Intake passage, 8 ... Exhaust passage, 9 ... Intake valve, 10 ... Exhaust valve, 14 ... Throttle sensor, 32 ... Rotation speed sensor (1
4, 32 ... constitute a detection means), 23 ... intake side V
VT, 26, 38 ... exhaust side VVT, 41 ... V VTEC
U.

Continuation of the front page (56) References JP-A-56-34914 (JP, A) JP-A-3-202640 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 13 / 02 F01L 1/12 F01L 1/34 F02M 25/07 510

Claims (1)

(57) [Claims] 1. An intake valve and an exhaust valve of an internal combustion engine .
Valve timing change to change valve timing individually
Means for controlling the residual ratio of exhaust gas in the combustion chamber of the internal combustion engine.
Valves of both valves that are almost constant regardless of changes in load
Of the timing combinations, the compression line of the internal combustion engine
The closing timing of the intake valve during
The combination of valve timings
Storage means for storing in advance as a function, detection means for detecting the engine load of the internal combustion engine, and the detected engine load and the storage means stored in the storage means.
The valve timing changing means based on the
The valve timing of both valves
A valve timing control device for an internal combustion engine, comprising: setting means for performing calculation and setting .