JPH05118232A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To always intend compatibility of improvement on fuel consumption with reduction of NOx without performing external reflux of exhaust gas. CONSTITUTION:An inlet side variable valve timing mechanism (an inlet side VVT) 23 and an exhaust side VVT 26 are respectively provided on respective camshafts 21, 22 in the inlet side and the exhaust side, and open and close timings of an inlet valve 9 and an exhaust valve 10 are made variable. A VVTECU 41 uses drive timing of the inlet side VVT 23 preset so as to be the latest in close timing of the inlet valve 9 in respective load ranges among combinations of both drive timings of the inlet side VVT 23 and the exhaust side VVT 26 for obtaining the most suiable target exhaust gas residual ratio in a combustion chamber 6 in accordance with load change, based on throttle opening and engine revolution speed input from respective sensors 14, 32 through an engine ECU 40. It is possible thereby to keep residual exhaust gas ratio in the most suitable level without depending on load change of an engine 1, in addition, to reduce pumping loss over the whole range of partial load.

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 constructed so that the opening and closing timings of an intake valve and an exhaust valve can be made variable according to the operating state of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a "residual gas control device for an internal combustion engine" disclosed in, for example, Japanese Patent Laid-Open No. 58-214610 is known as a technique of this type. In this technique, each of the intake valve and the exhaust valve is driven to open and close, and the opening and closing timing thereof is variable.
Then, by controlling the opening and closing timings of the intake valve and exhaust valve variably, the amount of residual exhaust gas contained in the combustion chamber is maintained at an optimum level, and at the same time, pumping loss in the intake stroke is reduced, and engine output is reduced. The NOx has been effectively reduced without compromising 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 the 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 part of the burnt gas is retained as a residual exhaust gas as it is in the combustion chamber to recirculate the internal exhaust gas. Then, the residual exhaust gas is mixed with the mixture gas to be sucked in next time to give a heat quantity to the mixture gas, thereby effectively reducing NOx without impairing combustion stability. At the same time, since the intake air amount is controlled by controlling the opening / closing timing of the intake valve, the pumping loss is reduced to improve fuel efficiency. Further, the opening of the intake valve and the exhaust valve is set to increase the valve overlap above the middle load range of the engine. And above the middle load range,
The amount of residual exhaust gas is reduced and the amount of intake air is increased. As a result, the air-fuel mixture is ensured to have a sufficient output in the engine in the middle load range or higher.

[0004]

However, in the above-mentioned conventional technique, the internal exhaust gas recirculation is realized by closing the exhaust valve before the exhaust top dead center only in the low load region.
Ox was reduced. Further, in the medium load range and above, the valve overlap is increased to reduce the residual exhaust gas amount, reduce the pumping loss, and increase the intake air amount. Therefore, in the operating range above the medium load range,
It becomes impossible to secure the residual exhaust gas amount necessary to reduce NOx to a predetermined level, and NO
In order to reduce x, it was necessary to perform exhaust gas recirculation from the outside.

By the way, the combination of the opening and closing timings of the intake valve and the exhaust valve for maintaining the residual exhaust gas ratio in the combustion chamber at an optimum level regardless of the load change of the engine is as follows.
It is known that there are several. Therefore, by combining such opening and closing timings of the intake valve and the exhaust valve, it is possible to secure the target residual exhaust gas amount necessary for reducing NOx in the entire load range and to improve the fuel consumption at a medium load or higher. Was wanted.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to constantly improve fuel efficiency and reduce NOx without recirculating exhaust gas from the outside to the internal combustion engine. Another object of the present invention is to provide a valve timing control device for an internal combustion engine capable of performing the above.

[0007]

In order to achieve the above object, in the present invention, as shown in FIG. 1, the internal combustion engine M1 is driven at a predetermined timing in synchronization with the rotation of the internal combustion engine M1.
An intake valve M5 and an exhaust valve M6 that open and close an intake passage M3 and an exhaust passage M4 that communicate with the combustion chamber M2, respectively,
An intake side variable valve timing mechanism M7 driven to change the opening / closing timing of the intake valve M5, an exhaust side variable valve timing mechanism M8 driven to change the opening / closing timing of the exhaust valve M6, and an internal combustion engine A load state detecting means M9 for detecting the load state of M1 and an intake side variable valve timing mechanism M7 for changing each opening / closing timing of the intake valve M5 and the exhaust valve M6 according to the detection result of the load state detecting means M9. In a valve timing control device for an internal combustion engine, which includes a drive control means M10 for driving and controlling the exhaust side variable valve timing mechanism M8, an optimum target exhaust gas residual ratio in the combustion chamber M2 is set in accordance with a load change of the internal combustion engine M1. Intake side variable valve timing machine used in drive control means M10 to obtain Intake / exhaust timing for setting the drive timing of the intake variable valve timing mechanism M7 so that the closing timing of the intake valve M5 is the slowest in each load region among the combination of the drive timings of M7 and the exhaust variable valve timing mechanism M8. Setting means M11 is provided.

[0008]

According to the above construction, as shown in FIG. 1, the intake valve M5 and the exhaust valve M are operated when the internal combustion engine M1 is in operation.
6 is driven at a predetermined timing in synchronism with the rotation of the internal combustion engine M1, and the intake passage M3 and the exhaust passage M4 are opened and closed to intake and exhaust the combustion chamber M2. or,
The load state detecting means M9 detects the load state of the internal combustion engine M1.

Then, the drive control means M10 changes the opening / closing timing of the intake valve M5 and the exhaust valve M6 in accordance with the load change detected by the load state detection means M9, so that the intake side variable valve timing mechanism M7 and the exhaust side variable valve timing mechanism can be changed. The valve timing mechanism M8 is drive-controlled. At this time, the drive control means M10 uses the intake variable valve timing mechanism M7 and the intake side variable valve timing mechanism M7 used by the drive control means M10 to obtain the optimum target exhaust gas residual ratio in the combustion chamber M2 according to the load change of the internal combustion engine M1. Of the combination of both drive timings of the exhaust side variable valve timing mechanism M8, the intake side variable valve timing mechanism M7 set by the intake / exhaust timing setting means M11 so that the closing timing of the intake valve M5 becomes the latest in each load region. Drive timing is used.

Therefore, the residual exhaust gas ratio is maintained at the target level irrespective of the load change of the internal combustion engine M1 and the closing timing of the intake valve M5 becomes the latest, so that the negative pressure of the intake passage M3 is reduced over the entire partial load. And the pumping loss is reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a valve timing control device for an internal combustion engine according to the present invention will be described below with reference to FIGS.
Will be described in detail based on.

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

The combustion chamber 6 is provided with an intake passage 7 and an exhaust passage 8 which communicate with each other. An intake valve 9 for opening and closing is attached to an intake port 7a that opens into the combustion chamber 6 of the intake passage 7. In addition, an exhaust valve 10 for opening and closing is provided at an exhaust port 8a opening in the combustion chamber 6 of the exhaust passage 8.
Is assembled.

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

In the middle of the intake passage 7, the accelerator pedal 1
A throttle valve 13 that is opened / closed in association with the operation of 2 is provided. Then, by opening and closing the throttle valve 13, the amount of intake air to the intake passage 7 is adjusted.

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

Next, a valve mechanism for the intake valve 9 and the exhaust valve 10 will be described. The intake valve 9 and the exhaust valve 10 are stems 9a and 10 extending upward, respectively.
a, and valve springs 17, 18 and valve lifters 19, 20 and the like are attached to the upper portions of the stems 9a, 10a, respectively. Cams 21a and 22a are provided so as to engage with the valve lifters 19 and 20, respectively. The cams 21a and 22a are formed on the intake-side camshaft 21 and the exhaust-side camshaft 22 supported by the cylinder head 5 in the number corresponding to 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 the direction of closing 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, respectively.

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 by sequentially selecting the electromagnetic coils to be excited, the step motor 25 rotates in a predetermined direction for each step. On the other hand, in order to make the opening / closing timing of the exhaust valve 10 variable, a timing pulley that constitutes 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 that appears and disappears by exciting and demagnetizing an electromagnetic coil in order to turn on and off the exhaust side VVT 26. These timing pulley assemblies 24 and 27 are drivingly connected to the crankshaft via a timing belt (not shown).

Therefore, when the engine 1 is operated, power is transmitted from the crankshaft to the timing pulley assemblies 24 and 27 via the timing belt,
The cam shafts 21 and 22 are rotationally driven to rotate the cams 21a and 22a, respectively. Further, the valve lifters 19 and 20 are pressed against the biasing forces of the valve springs 17 and 18 in accordance with 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 opened. As is well known, the basic opening and closing timings of the intake valve 9 and the exhaust valve 10 are vertical movements associated with four strokes (intake stroke, compression stroke, expansion stroke, exhaust stroke) of the piston 3 during two revolutions of the crankshaft. Is set in advance relative to. Here, when the intake port 7a is opened by the downward movement of the piston 3 during the intake stroke, that is, when the intake valve 9 is opened, the combustion chamber 6
The air-fuel mixture is inhaled. Also, 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 drive-controlled so as to change the basic opening / closing timing of the intake valve 9 in accordance with the operating state of the engine 1 at that time, in particular, the load state, and the camshaft 21, and thus the extension. The rotation phase of each cam 21a is appropriately changed. Then, the intake-side VVT 23 changes the basic opening / closing timing of the intake valve 9, thereby changing the valve overlap between the intake valve 9 and the exhaust valve 10.

Further, the exhaust side VVT 26 has an exhaust valve 10
Is controlled so as to change the basic opening / closing timing of the engine 1 in accordance with the operating state of the engine 1 at that time, particularly the load state, so that the rotational phase of the cam shaft 22, and thus the cams 22a, is appropriately changed. Is becoming Then, the basic opening / closing timing of the exhaust valve 10 is changed by the exhaust side VVT 26, so that 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, the spark plug 2 is attached to the cylinder head 5 at the center of the cylinder.
9 is fixed, and its discharge part 29a is arranged in the combustion chamber 6. This spark plug 29 is the distributor 3
It is driven based on the ignition signal distributed at 0. The distributor 30 synchronizes the high voltage output from the igniter 31 with the crank angle of the engine 1 and the spark plug 2
It is intended to be distributed to nine. Distributor 3
0 is a rotor 3 which is rotated in association with the rotation of the engine 1.
0a is provided, and a rotation speed sensor 32 that detects 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 which detects a crank angle reference position of the engine 1 at a predetermined ratio according to the rotation of the rotor 30a and outputs a reference position signal G thereof.

In addition to this, 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. An oxygen sensor 35 for detecting the oxygen concentration in the exhaust gas is attached in the middle of the exhaust passage 8.

In this embodiment, the throttle sensor 14 and the rotation speed sensor 32 constitute a load state detecting means for detecting the load state of the engine 1. Then, as shown in FIG. 2, the above-mentioned throttle sensor 1
4, the air flow meter 16, the rotation speed sensor 32, the cylinder discrimination sensor 33, the water temperature sensor 34, the oxygen sensor 35, etc. are electrically connected to the input side of an engine electronic control unit (hereinafter simply referred to as “engine ECU”) 40. .. The injector 11 and the igniter 31 described above are electrically connected to the output side of the engine ECU 40. Then, the engine ECU 40 uses the air flow meter 1
The injector 11, the igniter 31 and the like are preferably controlled based on the output signals from the sensor 6 and the sensors 14 and 32 to 35.

In this embodiment, the engine ECU 40
Is a control device that mainly controls the fuel injection amount control and ignition timing control of the engine 1. In addition to this, in this embodiment,
As shown in FIG. 2, the intake VVT 23 and the exhaust VVT 23
A VVTECU 41 for driving and controlling 26 is provided. The VVTECU 41 includes a rotation direction and a rotation amount of the output shaft of the step motor 25, an electromagnetic actuator 28.
It controls the appearance of the output shaft of. Therefore, the engine ECU 4 is provided on the input side of the VVTECU 41.
The detected values of the throttle opening TA, engine speed NE, etc. from 0 are input as data signals. Furthermore, 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 are output.

Next, the aforementioned engine ECU 40 and V
The configuration of VTECU 41 will be described with reference to the block diagrams of FIGS. FIG. 3 is a block diagram illustrating the electrical configuration of the engine ECU 40. Engine ECU
Reference numeral 40 denotes a central processing unit (CPU) 42, a read-only memory (RO) in which a predetermined control program and the like are stored in advance.
M) 43, a random access memory (RAM) 44 for temporarily storing the calculation result of the CPU 42, a backup RAM 45 for storing prestored data, and the like, these units, an external input circuit 46, an external output circuit 47, etc. It is configured as a theoretical operation circuit connected by 48.

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

Then, the CPU 42 inputs the air flow meter 16 and each sensor 1 through the external input circuit 46.
The signals from 4, 32 to 35 are read as input values.
At the time of reading the input value, the external input circuit 46 performs analog-digital conversion processing on the input values from the throttle sensor 14, the air flow meter 16, the water temperature sensor 34, and the oxygen sensor 35. Further, in the external input circuit 46, the input values from the rotation speed sensor 32, the cylinder discrimination sensor 33, etc. are subjected to waveform shaping processing. Then, the CPU 42 causes the air flow meter 16
Also, the injector 11, the igniter 31, etc. are suitably controlled based on the input values read from the respective sensors 14, 32 to 35, etc.

The CPU 42 also outputs the throttle opening TA and the engine speed NE among the signals read from the air flow meter 16 and the sensors 14, 32 to 35 as input values via the external input circuit 46. 47
To the VVTECU 41 as a data signal.

FIG. 4 is a block diagram for explaining the electrical construction of the VVTECU 41. The VVTECU 41 is a micro processing unit (MPU) 50, an intake side V
A ROM 51 in which predetermined control programs and the like for the VT 23 and the exhaust side VVT 26 and the like are stored in advance, a RAM 52 and the like for temporarily storing the calculation results of the MPU 50, and the like, these parts, an input / output port 53, an output port 54, and the like by a bus 55. It is configured as a connected theoretical calculation circuit.
Further, the VVTECU 41 is provided with a clock generator 56 that generates a periodic clock pulse, and the clock pulse is supplied from the generator 56 to the MPU 50. Further, the VVTECU 41 is provided with a latch circuit 57, a gate 58 and a drive circuit 59 connected to the output port 54 thereof.

The input / output port 53 is connected to the engine ECU 40. Further, the step motor 2 is provided at the gate 58.
5 is connected to the drive circuit 59, and the electromagnetic actuator 2
8 is connected.

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

Further, the MPU 50 determines whether to drive the electromagnetic actuator 28 according to the control program stored in the ROM 51 based on the read input value, and the determination result is used as the valve timing control signal in the drive circuit 5.
9 to drive the electromagnetic actuator 28.

Next, the structure of the intake side VVT 23 described above will be described in detail with reference to FIG. The intake-side cam shaft 21 that drives the intake valve 9 is rotatably supported by the cylinder head 5 by the cam journal 21b. The timing pulley assembly 2 that constitutes the VVT 23 is provided at the tip of the camshaft 21.
4 and step 25 are provided. The timing pulley assembly 24 is composed of a pulley body 62 having a plurality of outer teeth 61 on the outer circumference, an inner cap 63 and a cylindrical gear 64 mounted on the pulley body 62.

That is, the pulley body 62 is provided with a boss 62a and a circumferential wall 62b near the center thereof, and a circumferential groove 62c is provided between the boss 62a and the circumferential wall 62b. Helical teeth 62d are formed on the inner circumference of the circumferential wall 62b. The pulley body 62 is mounted on the camshaft 21 so as to be relatively rotatable by the boss 62a.
On the other hand, the inner cap 63 includes a large tubular portion 63a and a small tubular portion 63b extending to the opposite side, and helical teeth 63c are formed on the outer circumference of the large tubular portion 63a. Then, the inner cap 63 is fitted so that its large cylindrical portion 63a covers the boss 62a, and is assembled so as to be rotatable relative to the pulley body 62. The inner cap 63 is integrally rotatably fixed to the tip of the camshaft 21 by a bolt 65 and a knock pin 66. Further, the cylindrical gear 64 has an outer peripheral wall 6
4a and an inner peripheral wall 64b, and a hole 6 is formed in its bottom wall.
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.
Then, 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 respect to c.

In this assembled state, the helical teeth 62d, 63c, 64d, 64e are meshed with each other, and due to the meshing relationship, the cylindrical gear 64 can rotate relative to the camshaft 21 by moving in the axial direction. There is. Further, the timing pulley assembly 24 is drive-connected to the crankshaft via a timing belt (not shown) that is hooked around the outer teeth 61 of the pulley body 62.

Therefore, when the drive force is transmitted 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, and further the bolt 65 and the knock pin 66 are used. The cam shaft 21 connected to the inner cap 63 is integrally driven to rotate.

The step motor 25 described above 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, and a worm gear 67 having a cylindrical shape and having teeth 67a on the outer periphery is attached to the output shaft thereof. The worm gear 67 is a small cylinder portion 6 of the inner cap 63.
It is fitted so as to be rotatable relative to 3b, and is arranged so as to penetrate through the hole 64c of the cylindrical gear 64. On the other hand, around the hole 64c of the cylindrical gear 64, a ring goya 68 having teeth 68a on its inner periphery is mounted by a ball bearing 69 so as to be relatively rotatable. The ring gear 68 is meshed with the outer circumference of the worm gear 67, and due to the meshing relationship, the worm gear 67 can rotate to move in the axial direction. Further, in order to prevent the ring gear 68 from rotating, the long groove 6 extending in the axial direction is formed on the outer periphery of the ring gear 68 on the step motor 25 side.
8b is formed. At the same time, a detent member 70 having a tubular shape and extending toward the timing pulley assembly 24 is attached to the casing of the step motor 25. The long groove 6 described above is provided on the inner circumference of the rotation stopping member 70.
A protrusion 70a that engages with 8b is formed. And
Due to the engagement relationship between the protrusions 70a and the long grooves 68b, the ring gear 68 is prevented from rotating and only the movement in the axial direction is allowed.

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

Therefore, when the timing pulley assembly 24 and the cam shaft 21 are integrally rotated, the step motor 25 is driven to rotate the worm gear 67 in a certain direction by a predetermined amount, whereby the ring gear 68 is rotated.
Is moved in the axial direction while being prevented from rotating on the worm gear 67. Along with this, the cylindrical gear 64 is moved in the same axial direction, relative rotation occurs between the pulley main body 62 and the cam shaft 21, and the cam shaft 21 is twisted. As described above, in the VVT 23 of this embodiment, the stepping motor 25 is drive-controlled to cause the cylindrical gear 6 to rotate.
The axial position of 4 is changed, and as a result, 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, as the opening / closing timing of the intake valve 9, from the opening timing (50 ° before top dead center) / closing timing (20 ° after bottom dead center) to the opening timing (-10 ° before top dead center).・ Close timing (80 after bottom dead center
°) is continuously variable.

In this embodiment, the exhaust side VVT2 is
Regarding the configuration of the timing pulley assembly 27 of 6,
The description is omitted because it is almost the same as that of the timing pulley assembly 24 described above. Also, exhaust side VVT
In the timing pulley assembly 27 of 26, an electromagnetic actuator 28 is provided instead of the step motor 25 described above. Then, the electromagnetic actuator 2
When the exhaust side VVT 26 is turned on and off by the appearance of the output shaft 8 of the valve 8, the opening / closing timing pulley of the exhaust valve 10 is changed in two steps, and the valve overlap is changed.

In this embodiment, the opening / closing timing of the exhaust valve 10 is opening timing (0 ° after top dead center), closing timing (40 ° before bottom dead center), and opening timing (20 ° after top dead center). Closing timing (20 before bottom dead center)
°) and can be switched between.

Next, the operation of the valve timing control device for an internal combustion engine configured as described above will be described with reference to FIGS. FIG. 6 shows the intake side VVT 23 and the exhaust side V
9 is a flowchart illustrating a “VVT control routine” executed by the VVTECU 41 to control the drive of the VT 26, which is executed by a regular interrupt every predetermined time.

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

Subsequently, at step 102, the throttle opening TA and the engine speed NE which have been read in before are read.
Based on the above, the intake load function fI (NE, T is referred to by referring to the map using those values as parameters as shown in FIG.
A) is calculated, and the calculation result is set as the target step number Vst.

Here, the map of FIG. 7 is stored in advance in the ROM 51, and in this map, the combustion chamber changes in accordance with changes in the throttle opening TA and engine speed NE, that is, changes in the load of the engine 1. Intake-side VVT 23 and exhaust-side V for obtaining the optimum target exhaust gas residual ratio within 6
Of the drive timings of the VT 26, the intake load function fI (NE, TA) is set so that the closing timing of the intake valve 9 becomes the latest in each load range.

Then, in step 103, the step motor 25 is moved from the set target step number Vst.
The result obtained by subtracting the current step number Vpo in step 1 is set as the control step number STEP.

Next, at step 104, it is judged if the control step number STEP is "0". Here, when the control step number STEP is “0”,
Step 1 without driving the step motor 25
Move to 14. Then, in step 114, the exhaust load function fE (NE, NE, based on the previously read throttle opening TA and engine speed NE, is referred to with reference to a map using those values as parameters as shown in FIG.
TA) is calculated, and the calculation result is set as the excitation signal VE.

Here, the map of FIG. 8 is stored in advance in the ROM 51. In this map, the combustion chamber 6 is changed according to changes in the throttle opening TA and engine speed NE, that is, changes in the load of the engine 1. Intake-side VVT 23 and exhaust-side VV for obtaining the optimum target exhaust gas residual ratio in
The exhaust load function fE (NE, TA) is set so as to be a combination of both drive timings of T26.

Then, in step 115, the electromagnetic actuator 28 is drive-controlled based on the excitation signal VE, that is, the exhaust-side VVT 26 is drive-controlled, and the subsequent processing is once ended.

On the other hand, when the control step number STEP is not "0" in step 104, step 10
In 5, it is determined whether the control step number STEP is larger than "0", that is, whether the control step number STEP is a positive number. Here, the control step number STEP
Is a positive number, the control flag DIR is reset to "0" in step 106, and then step 1
Move to 09.

In step 105, if the control step number STEP is a negative number, step 107
At, the control flag DIR is set to "1".
In step 108, the control step number STEP
After the absolute value of is set as the new control step number STEP, the process proceeds to step 109.

Then, step 106 or step 10
In step 109 after shifting from 8, it is determined whether 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 reversing only the steps, the process proceeds to step 112. When the control flag DIR is "0", the step motor 25 is normally rotated by one step in step 111, and then the process proceeds to step 112.

In step 112 after shifting from step 110 or step 111, the control step number ST
The result of subtracting "1" from EP is set as a new control step number STEP. In step 113, it is determined whether the new control step number STEP is "0". Then, the new control step number ST
If EP is not "0", the process jumps to step 109 and the processes of steps 109 to 113 are repeated. That is, the intake side VVT 23 is drive-controlled.

On the other hand, if the new control step number STEP is "0", the process proceeds to step 114, and in step 114, based on the previously read throttle opening TA and engine speed NE, As shown in FIG. 8, the exhaust load function fE (NE, TA) is calculated with reference to the map using those values as parameters, and the calculation result is set as the excitation signal VE. Then, step 1
At 15, the electromagnetic actuator 28 is drive-controlled based on the excitation signal VE, that is, the exhaust-side VVT 26 is drive-controlled, and the subsequent processing is once ended.

In this way, the intake side VVT 23 and the exhaust side VVT 26 are drive-controlled by the control of the step motor 25 and the electromagnetic actuator 28, respectively, and the intake valve 9
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
The change in the closing timing of the intake valve 9 and the exhaust valve 10 with respect to the crankshaft torque at the engine speed NE of "0 rpm", that is, the axial torque corresponding to the load will be described with reference to the graph of FIG. As is clear from this graph, in this embodiment, the closing timing of the intake valve 9 is delayed and the closing timing of the exhaust valve 10 is set early in the low load range. Further, in the medium load range, the closing timing of the intake valve 9 is set to be as late as possible, and the closing timing of the exhaust valve 10 is set to be delayed. Further, in the high load range, the closing timing of the intake valve 9 is set to be as late as possible and the closing timing of the exhaust valve 10 is set to be early. The setting of the closing timing is performed in the same manner for the engine speed NE other than "2000 rpm".

Therefore, 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 and the pumping loss is reduced. 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 becomes short, and the residual exhaust gas in the combustion chamber 6 is restricted 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 loss is reduced. Exhaust valve 1
Since the closing timing of 0 is relatively late, the combustion chamber 6
The residual exhaust at is increased. In addition, in the high load area,
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, the residual exhaust gas in the combustion chamber 6 is increased.

The results are shown in FIG. FIG. 10 shows changes in pumping loss and residual exhaust gas ratio with respect to shaft torque,
It is a graph which compares and shows the control result of a present Example, and the result by a normal cam. As is apparent from this graph, it is understood that the control result of the present embodiment is relatively smaller in pumping loss than the result of the normal cam. Further, regarding the residual exhaust gas ratio, it can be seen that the control result of this embodiment is maintained at a substantially constant target level as compared with the result of the normal cam. That is, according to the control result of this embodiment, the residual exhaust gas ratio can be maintained at almost the target level over the entire load range, and the pumping loss can be reduced.

Therefore, according to the valve timing control device of this embodiment, the residual exhaust gas ratio can be maintained at a substantially target level over the entire load range, so that the exhaust gas recirculation from the outside is not performed over the entire load range. Internal exhaust gas recirculation can be realized across the entire range to reduce NOx. or,
Since the pumping loss can be made relatively small, the amount of intake air into the combustion chamber 6 can be increased in the operating range of the medium load range or higher, and the output of the engine 1 and the fuel consumption can be improved. That is, the fuel consumption is always improved and NO
It is possible to achieve both reduction of x.

The present invention is not limited to the above-described embodiment, but may be implemented as follows with a part of the structure appropriately changed without departing from the spirit of the invention. (1) In the above embodiment, the intake-side camshaft 21 and the exhaust-side camshaft 22 are linked via the timing pulley assemblies 24 and 27 and the timing belt, but as shown in FIG. , The intake-side camshaft 21 and the exhaust-side camshaft 22 are interlocked with each other through the engagement of a pair of scissors gears 36, 37, and the timing pulley assembly 24 and the step motor 25 are attached to the tip of the intake-side camshaft 21. Intake side V
The VT 23 may be provided, and the exhaust side VVT 38 may be configured by the scissors gear 37 of the exhaust side camshaft 22 and the electromagnetic actuator 28.

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

(3) In the above embodiment, the gasoline engine 1 is embodied, but it may be embodied as a diesel engine.

[0065]

As described in detail above, according to the present invention,
Of the combination of both drive timing of the intake side variable valve timing mechanism and the exhaust side variable valve timing mechanism for obtaining the optimum target exhaust gas residual ratio in the combustion chamber according to the load change of the internal combustion engine, the intake valve Since the drive timing of the intake variable valve timing mechanism is set so that the closing timing becomes the latest, pumping loss is reduced over the entire partial load and exhaust gas recirculation from the outside to the internal combustion engine is not performed. The excellent effect that both improvement of fuel consumption and reduction of NOx can be achieved at the same time is always exhibited.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram illustrating a basic conceptual configuration of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a gasoline engine in an embodiment embodying the present invention.

FIG. 3 is a block diagram showing an electrical configuration of an engine ECU according to an embodiment.

FIG. 4 is a block diagram showing an electrical configuration of a VVTECU according to an embodiment.

FIG. 5 is a cross-sectional view showing the structure of a VVT in one example.

FIG. 6 is a flowchart illustrating a “VVT control routine” executed by the VVTECU in the embodiment.

FIG. 7 is a map in which a value of an intake load function with an engine speed and a throttle opening as parameters is predetermined in one embodiment.

FIG. 8 is a map in which a value of an exhaust load function having an engine speed and a throttle opening as parameters is predetermined in one embodiment.

FIG. 9 is a graph for explaining changes in the closing timing of the intake valve and the exhaust valve with respect to the shaft torque corresponding to the engine load in one embodiment.

FIG. 10 is a graph illustrating changes in pumping loss and residual exhaust gas ratio with respect to shaft torque corresponding to engine load in one embodiment.

FIG. 11 is a plan view illustrating the configuration of a valve timing control device according to another embodiment of the present invention.

[Description of Reference Signs] 1 ... Engine as 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 load state detection means), 23 ...
Intake side VVT, 26, 38 ... Exhaust side VVT, 41 ... VV constituting drive control means and intake / exhaust timing setting means
TECU.

Claims (1)

[Claims] 1. An intake valve and an exhaust valve, which are driven at a predetermined timing in synchronization with the rotation of an internal combustion engine to open and close an intake passage and an exhaust passage communicating with a combustion chamber, respectively, and an opening / closing timing of the intake valve is made variable. An intake side variable valve timing mechanism driven for that purpose, an exhaust side variable valve timing mechanism driven for varying the opening / closing timing of the exhaust valve, and a load state detection means for detecting a load state of the internal combustion engine. Drive control means for driving and controlling the intake variable valve timing mechanism and the exhaust variable valve timing mechanism so as to change the opening and closing timings of the intake valve and the exhaust valve in accordance with the detection result of the load state detection. A valve timing control device for an internal combustion engine, comprising: Of the combination of both drive timings of the intake side variable valve timing mechanism and the exhaust side variable valve timing mechanism used by the drive control means to obtain the optimum target exhaust gas residual ratio in the combustion chamber according to the change A valve timing control device for an internal combustion engine, comprising: intake / exhaust timing setting means for setting a drive timing of the intake side variable valve timing mechanism such that a closing timing of the intake valve is delayed in each load region. ..