JPH06257477A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To suppress knocking without using any knock sensor and the like and to suppress worsening of fuel consumption. CONSTITUTION:An opening/closing timing of an intake valve is altered by driving a VVT 23 by an oil pressure. An ECU 70 computes a driving area of an engine 1 on the basis of signals of an air flow meter 62, a rotational speed sensor 66, and the like. When the computed result is in a low relation and load area or a low rotation and high load area, the opening/closing timing of the intake valve 8 drives the VVT 23 for spark-advance. On the other hand, when the computed result is in a low rotation and medium load area or in an area of more than medium rotation, the VVT 23 is driven so as to delay the opening/closing timing of the intake valve 8. Therefore, the opening/closing timing of the intake valve 8 is delayed in a low rotation and medium load driving area, in which knocking is likely to happen, so that an intake air, which tends to escape after being introduced into a combustion chamber 4 once, is increased, and consequently, the intake air amount is reduced and an effective compression ratio is reduced.

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 for varying the opening / closing timing of an intake valve during operation of an internal combustion engine. More specifically, the present invention relates to a valve timing control device for an internal combustion engine that suppresses knocking by changing valve timing.

[0002]

2. Description of the Related Art Conventionally, in knocking control of an internal combustion engine such as a gasoline engine, occurrence of knocking is determined based on a signal from a knock sensor provided in the engine body. When it is determined that knocking has occurred, the ignition timing is retarded to suppress knocking. However, retarding the ignition timing may result in deterioration of fuel efficiency, and therefore knocking control instead of this has been desired.

Therefore, Japanese Patent Laid-Open No. 59-93939 discloses a technique for suppressing knocking by controlling the opening / closing timing of the intake valve, that is, the valve timing instead of controlling the ignition timing. This prior art was proposed focusing on the fact that the effective compression ratio of the internal combustion engine changes by changing the valve timing. When it is determined that knocking occurs based on the detection signal from the knock sensor, the valve timing variable mechanism is controlled so that the valve timing is retarded. On the other hand, when it is not knocking, the variable valve timing mechanism is controlled so that the valve timing is advanced.

[0004]

However, in the above-mentioned conventional technique, since it is premised that the occurrence of knocking is determined, a knock sensor is required, and the number of sensors required for controlling the internal combustion engine is reduced. The result was to increase. Moreover, it is necessary to perform a process for determining the occurrence of knocking, and a control program for that is required.

In addition, in the prior art, since the valve timing is retarded when it is actually determined that knocking has occurred, there is a case where the fuel consumption is sacrificed while the knocking is suppressed. That is, the graph of FIG. 9 shows the relationship between the output torque and the fuel consumption that correlate with the load of the internal combustion engine. Further, a characteristic curve for advancing the opening timing of the intake valve and a characteristic curve for retarding the opening timing of the intake valve are shown by broken lines and two-dot chain lines, respectively. As is clear from this graph, it can be seen that the advancing characteristic curve and the retarding characteristic curve are reversed at the intersections of the two characteristic curves with respect to the fuel efficiency with respect to an arbitrary output torque. That is, on the side of small output torque than on the intersection, the advance characteristic curve has better fuel consumption, and on the side of large output torque than the intersection, the characteristic curve of retardation shows better fuel consumption. Here, in the conventional valve timing control, the knocking occurrence point at which knocking occurrence is determined may be on the smaller output torque side than the intersection.
In that case, the change in fuel consumption immediately shifts from the knocking occurrence point to the retarded characteristic curve, as shown by the solid line in the figure. Then, when an increase in output torque is requested from the knocking occurrence point to the full load point, the fuel economy changes as it is in accordance with the delay angle characteristic curve, and the output torque is further increased at the full load point. Therefore, it is returned to the characteristic curve of the advance angle. Therefore, as indicated by hatching in the figure, fuel consumption deteriorates in the region from the knocking occurrence point to the intersection.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to suppress knocking without determining the occurrence of knocking using a knock sensor or the like, and also to reduce fuel consumption. An object of the present invention is to provide a valve timing control device for an internal combustion engine that can be suppressed.

[0007]

In order to achieve the above object, in the present invention, as shown in FIG. 1, an intake passage M3 which is driven in synchronization with the rotation of an internal combustion engine M1 and communicates with a combustion chamber M2 and An intake valve M5 and an exhaust valve M6 for respectively opening and closing the exhaust passage M4, and an intake valve M5
The variable valve timing mechanism M7 driven to make the opening / closing timing of the engine variable, the operating state detecting means M8 for detecting the operating state of the internal combustion engine M1, and the intake state based on the detection result of the operating state detecting means M8. A valve timing control device for an internal combustion engine, comprising: a drive control means M9 for driving and controlling a variable valve timing mechanism M7 to change the opening / closing timing of a valve M5, based on a detection result of an operating state detection means M8. An operating area calculation means M10 for calculating the operating area of M1;
When the calculation result of the operating region calculation means M10 is a low rotation and low load region or a low rotation and high load region, the opening / closing timing of the intake valve M5 to be changed by the control of the drive control device M9 is advanced. When the calculation result of the advance angle setting means M11 set to the angle side and the operation area calculation means M10 is a low rotation and medium load area or a medium rotation or higher area,
The purpose is to include a retard angle setting means M12 for setting the opening / closing timing of the intake valve M5 to be retarded by the control of the drive control means M9.

[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 in synchronization with the rotation of the internal combustion engine M1, and the combustion chamber M
The intake passage M3 and the exhaust passage M4 which communicate with 2 are opened and closed to intake and exhaust the combustion chamber M2. Further, the drive control means M9 drives and controls the variable valve timing mechanism M7 to change the opening / closing timing of the intake valve M5. In addition, this changes the valve overlap between the intake valve M5 and the exhaust valve M6.

Then, in the transfer region calculating means M10, based on the detection result of the operating state detecting means M8, the internal combustion engine M1
Is calculated. When the calculation result of the operation region is a low rotation and low load region or a low rotation and high load region, the opening / closing timing of the intake valve M5 to be changed by the control of the drive control unit M9 is The lead angle is set by the lead angle setting means M11. On the other hand, when the calculation result of the operating region is the region of low rotation and medium load, or the region of medium rotation or higher, the opening / closing timing of the intake valve M5 to be changed by the control of the drive control means M9 is set to the retard angle setting. It is set to the retard side by the means M12.

Therefore, when the internal combustion engine M1 is in a low rotation and medium load operation region where knocking is likely to occur, the opening and closing timing of the intake valve M5 is retarded, so that before and after the intake stroke is shifted to the compression stroke. The closing of the intake valve M5 becomes slower. Therefore, the intake air that is once introduced into the combustion chamber M2 and then tries to escape increases, and the effective intake air amount decreases and the effective compression ratio decreases.

Further, when the internal combustion engine M1 is in the operating region of low rotation and low load, or low rotation and high load, the opening / closing timing of the intake valve M5 is advanced, so that the intake stroke to the compression stroke are advanced. The intake valve closes before and after moving to. Therefore, the intake air that is once introduced into the combustion chamber M2 and then tries to escape decreases, and the effective intake air amount increases and the effective compression ratio increases.

Further, when the internal combustion engine M1 is in the operation region of medium rotation or higher, the opening / closing timing of the intake valve M5 is retarded, so that the intake valve M5 is closed at the time of shifting from the intake stroke to the compression stroke. Become slow. However, in this operating region, the momentum of the intake air is large and the inertia effect of the intake air is obtained, so that the efficiency of filling the combustion chamber M2 with the intake air is improved. Therefore, even if the closing of the intake valve M5 is delayed a little, the substantial amount of intake air introduced into the combustion chamber M2 increases and the effective compression ratio increases.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the valve timing control device for an internal combustion engine according to the present invention is embodied in a gasoline engine will be described in detail below with reference to FIGS.

FIG. 2 is a schematic configuration diagram showing a valve timing control device for an internal combustion engine in this embodiment. In an engine 1 as an internal combustion engine including a plurality of cylinders, a piston 3 is provided in a cylinder 2 for each cylinder so as to be vertically movable, and an upper side of each piston 3 is a combustion chamber 4. A spark plug 5 is provided in each combustion chamber 4. Further, an intake passage 6 and an exhaust passage 7 are provided in communication with each combustion chamber 4 through an intake port 6a and an exhaust port 7a. The intake port 6a and the exhaust port 7a are provided with an intake valve 8 and an exhaust valve 9 for opening and closing, respectively. These intake valves 8
The exhaust valve 9 is driven by the rotation of the intake camshaft 10 and the exhaust camshaft 11. An intake side timing pulley 12 and an exhaust side timing pulley 13 are provided at one end of each of the camshafts 10 and 11. Furthermore, each timing pulley 12, 13
Are drivingly connected to a crankshaft (not shown) via a timing belt 14.

Therefore, during operation of the engine 1, rotational power is transmitted from the crankshaft to the camshafts 10 and 11 via the timing belt 14 and the timing pulleys 12 and 13, and the intake air is generated by the rotation of the camshafts 10 and 11. The valve 8 and the exhaust valve 9 are opened and closed. Further, the opening / closing timings of the intake valve 8 and the exhaust valve 9 are predetermined in synchronization with the rotation of the crankshaft, that is, in synchronization with a series of four strokes of an intake stroke, a compression stroke, an explosion / expansion stroke and an exhaust stroke. It is opened and closed at the timing.

An air cleaner 15 is provided on the inlet side of the intake passage 6.
Is provided. An injector 16 for fuel injection is provided near the intake port 6a for each cylinder. Then, outside air is taken into the intake passage 6 through the air cleaner 15. Further, at the same time when the outside air is taken in, fuel is injected from each injector 16 into the intake port 6a. Then, in the engine 1, the mixture of the outside air and the fuel is introduced into the combustion chamber 4 in synchronization with the opening of the intake valve 8 in the intake stroke. Further, in the engine 1, the air-fuel mixture introduced into the combustion chamber 4 is exploded and burned by the ignition of the spark plug 5 to obtain a driving force. Further, the exhaust gas after combustion is led out from the exhaust port 7a in synchronization with the opening of the exhaust valve 9 in the exhaust stroke, and further, the exhaust passage 7
Is discharged to the outside through.

A throttle valve 17 which is opened / closed in conjunction with the operation of an accelerator pedal (not shown) is provided in the intake passage 6. By opening / closing the throttle valve 17, the intake air amount Q which is the intake amount of the outside air into the intake passage 6 is adjusted. A surge tank 18 for smoothing the pulsation of intake air is provided downstream of the throttle valve 17 in the intake passage 6. An intake air temperature sensor 61 for detecting the intake air temperature THA is provided in the intake passage 6 in the vicinity of the air cleaner 15.
Is provided. Similarly, an air flow meter 6 for detecting the intake air amount Q is provided near the air cleaner 15.
Two are provided. A throttle sensor 63 for detecting the throttle opening TA is provided near the throttle valve 17.

On the other hand, in the middle of the exhaust passage 7, a catalytic converter 20 having a three-way catalyst 19 for purifying the exhaust gas is provided. In the middle of the exhaust passage 7,
An oxygen sensor 64 is provided for detecting the oxygen concentration in the exhaust gas.

Further, the engine 1 is provided with a water temperature sensor 65 for detecting the temperature (cooling water temperature) THW of the cooling water. The ignition signal distributed by the distributor 21 is applied to each ignition plug 5 for each cylinder. The distributor 21 distributes the high voltage output from the igniter 22 to each spark plug 5 in synchronization with the rotation of the crankshaft, that is, the crank angle. The ignition timing of each spark plug 5 is determined by the high voltage output timing from the igniter 22.

The distributor 21 has a built-in rotor (not shown) which is connected to the exhaust side camshaft 11 and rotates in conjunction with the crankshaft. The distributor 21 is provided with a rotation speed sensor 66 for detecting the rotation speed (engine rotation speed) NE of the engine 1 from the rotation of the rotor. or,
The distributor 21 is also provided with a cylinder discrimination sensor 67 for detecting the crank angle reference position GP of the engine 1 at a predetermined rate in accordance with the rotation of the rotor. In this embodiment, the intake stroke of the engine 1,
Assuming that the crankshaft makes two revolutions for a series of four strokes including the compression stroke, the explosion / expansion stroke, and the exhaust stroke, the rotation speed sensor 66 detects the crank angle at a rate of 30 ° CA per pulse. Further, the cylinder discrimination sensor 67 detects the crank angle at a rate of 360 ° CA per pulse.

In this embodiment, the air flow meter 62, the throttle sensor 63, the rotation speed sensor 66 and the like constitute the operating condition detecting means for detecting the operating condition of the engine 1.

In addition, in this embodiment, the intake side timing pulley 12 is provided with a variable valve timing mechanism (hereinafter simply referred to as "VVT") 23 driven by hydraulic pressure to make the opening / closing timing of the intake valve 8 variable. It is provided.

The configuration of the VVT 23 and the like will be described in detail with reference to FIG. The camshaft 10 has a cam journal 10 a whose cylinder head 1 is the engine 1.
It is rotatably supported between a and the bearing cap 1b. A VVT 23, which is provided integrally with the timing pulley 12, is provided at one end of the camshaft 10.

The timing pulley 12 has a plurality of outer teeth 31 on its outer circumference and a housing recess 32 on one side. In addition, the camshaft 1 covers the accommodation recess 32.
A cap 33 is fastened and fixed to the tip of 0 by a bolt 34. Further, between the opening end of the timing pulley 12 and the outer periphery of the cap 33, a well-known cushioning member including an outer plate 35 press-fitted and fixed to the pulley 12, an inner plate 36 formed on the cap 33, and the like. A viscous joint (viscus coupling) 37 is provided.

A ring gear 38 is interposed between the timing pulley 12 and the camshaft 10, and the ring gear 38,
10 are connected. That is, the ring gear 38 is housed in the housing recess 32 of the timing pulley 12 which is sealed by the cap 33. The ring gear 38 has helical teeth on both teeth 38a and 38b provided on the inner and outer circumferences thereof, and is rotatable relative to the camshaft 10 by moving in the axial direction. The teeth 38a, 38b on the inner and outer circumferences of the ring gear 38 are the timing pulley 1
The two inner teeth 12 a and the inner teeth 33 a of the cap 33 are in mesh with each other. Further, the timing pulley 12 is drivingly connected to a crankshaft (not shown) via a timing belt 14 that is wound around its outer teeth 31.

Therefore, when the drive force is transmitted from the crankshaft to the timing pulley 12 via the timing belt 14, the timing pulley 12 and the cap 33, which are further connected by the ring gear 38, are integrally rotated, and the camshaft 10 is rotated. It is driven to rotate. At this time, the ring gear 38 is moved in the axial direction (the left-right direction in FIG. 3), so that the camshaft 10 is twisted with respect to the timing pulley 12. As a result, the camshaft 1
0 and the relative position of the timing pulley 12 in the rotation direction are changed, and the opening / closing timing of the intake valve 8 is changed. The rattling caused by the backlash of the ring gear 38 when the cam shaft 10 is twisted is buffered by the action of the viscous coupling 37, and the generation of abnormal noise is suppressed.

In order to drive the ring gear 38 hydraulically, in the accommodation recess 32 of the timing pulley 12,
One end side of the ring gear 38 in the axial direction is a pressurizing chamber 39 into which hydraulic pressure of hydraulic oil is introduced. Similarly, in the accommodation recess 32, the other end of the ring gear 38 is a spring chamber 41 for accommodating a balancing spring 40 that opposes the hydraulic pressure. Further, a head oil passage 42 and a shaft oil passage 43, which communicate with each other, are formed in the cylinder head 1a of the engine 1 and the camshaft 10, respectively, in order to supply hydraulic pressure to the pressurizing chamber 39.

On the other hand, in order to drain the hydraulic oil from the pressurizing chamber 39, a part of the timing pulley 12 and the camshaft 10 is returned for discharging the hydraulic oil leaking from the pressurizing chamber 39 to the spring chamber 41. An oil passage 44 is formed.
In addition, the timing pulley 1 communicates with the return oil passage 44.
At one end side of 2, the camshaft 10 and the cylinder head 1
An oil recovery chamber 46 surrounded by a, the bearing cap 1b and the rubber seal 45 is provided. Furthermore,
At the lower position of the camshaft 10, the cylinder head 1a
An oil return hole 48 for returning the working oil recovered in the oil recovery chamber 46 to the oil pan 47 of the engine 1 is formed in a part of the above.

The upper side of the cylinder head 1a is covered with a head cover 49. Also, the cylinder head 1
A head oil passage 50 for supplying lubricating oil to the cam journal 10a is formed in a.

In this embodiment, the engine 1 is used as hydraulic oil.
Lubricating oil is used. That is, as shown in FIGS. 2 and 3, by driving the oil pump 51 linked to the operation of the engine 1, the lubricating oil accumulated in the oil pan 47 is sucked up. Then, the lubricating oil flows from the oil filter 52 to the first oil switching valve (OSV).
The hydraulic oil is supplied to the head oil passage 42 of the cylinder head 1 a via 53. The lubricating oil sucked up by the oil pump 51 is guided from the oil filter 52 to another head oil passage 50 and supplied to the cam journal 10a. On the other hand, the lubricating oil returned from the head oil passage 42 is
The oil is drained to the oil pan 47 through the drain second OSV 55.

The supply and release of hydraulic oil to the pressurizing chamber 39 is controlled by switching the first and second OSVs 53 and 54 on and off. That is, when the first OSV 53 is turned on and the second OSV 54 is turned off, hydraulic oil is supplied to the head oil passage 42, and the hydraulic oil is supplied to the head oil passage 4
2 is introduced into the pressurizing chamber 39 through the shaft oil passage 43. The hydraulic pressure causes the ring gear 38 to resist the urging force of the spring 40 in one axial direction (rightward in FIG. 3).
Is pushed to. As a result, the camshaft 10 is twisted and the rotational phase with respect to the timing pulley 12 is changed. That is, as shown in FIG. 5B, the opening / closing timing of the intake valve 8, that is, the opening / closing timing is advanced (advanced), and the intake valve 8 in the intake stroke is advanced.
The valve overlap between the exhaust valve 9 and the exhaust valve 9 is increased.

On the other hand, the first OSV 53 is turned off, and the second
When the OSV 54 is turned on, the supply of hydraulic oil to the head oil passage 42 is cut off. As a result, the hydraulic pressure is released in the pressurizing chamber 39, and the ring gear 38 is pressed back by the urging force of the spring 40 in the other axial direction (leftward in FIG. 3). As a result, an opposite twist is applied to the camshaft 10 and the rotational phase with respect to the timing pulley 12 is changed. That is, as shown in FIG. 5A, the opening / closing timing of the intake valve 8 is delayed (retarded), and the valve overlap in the intake stroke is reduced. At this time, the hydraulic oil leaking from the pressurizing chamber 39 to the spring chamber 41 is guided to the oil recovery chamber 46 through the return oil passage 44 and drained to the oil pan 47 through the oil return hole 48.

Each injector 16, the igniter 22, and the first and second OSVs 53, 54 are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 70, and the EC
The operation of U70 controls their drive timing. The ECU 70 constitutes drive control means, operating area calculation means, advance angle setting means, and retard angle setting means. Then, the intake air temperature sensor 6 described above is included in the ECU 70.
1, an air flow meter 62, a throttle sensor 63, an oxygen sensor 64, a water temperature sensor 65, a rotation speed sensor 66, and a cylinder discrimination sensor 67 are connected to each other. ECU
Reference numeral 70 denotes each injector 16, 63-67 and each injector 16, based on the output signals from the air flow meter 62.
The igniter 22 and the first and second OSVs 53 and 54 are preferably controlled.

Next, the electrical configuration of the ECU 70 will be described with reference to the block diagram of FIG. The ECU 70 includes a central processing unit (CPU) 71, a read-only memory (ROM) 72 that stores a predetermined control program and the like in advance, and a CP.
A random access memory (RAM) 73 for temporarily storing the calculation result of U71, a backup RAM 74 for storing previously stored data, and the like are provided. And EC
The U 70 is configured as a theoretical operation circuit in which the respective components 71 to 74, the external input circuit 75, the external output circuit 76, etc. are connected by a bus 77.

The external input circuit 75 includes the intake air temperature sensor 61, the air flow meter 62, and the throttle sensor 6 described above.
3, oxygen sensor 64, water temperature sensor 65, rotation speed sensor 6
6 and the cylinder discrimination sensor 67 are connected to each other.

On the other hand, the external output circuit 76 includes the injectors 16, the igniter 22, the first OSV 53, and the second output circuit 76.
OSV 54 of each is connected. And CP
U71 reads the output signals from the sensors 61, 63 to 67, the air flow meter 62, etc., which are input via the external input circuit 75, as input values. Further, the CPU 71 preferably controls the injectors 16, the igniter 22, the first and second OSVs 53, 54, etc. based on the read input values.

Next, the processing operation of the valve timing control executed by the above-mentioned ECU 70 will be described with reference to FIGS.
Follow the instructions below. The flowchart of FIG.
5 shows a "valve timing control routine" that is performed to switch the opening / closing timing of the intake valve 7 among the processes executed by the engine 1 every predetermined time ("10 ms" in this embodiment) during the operation of the engine 1. It is executed by the scheduled interrupt of.

When the processing shifts to this routine, first, at step 101, the intake air amount Q, the throttle opening TA and the engine speed NE are based on the output signals from the air flow meter 62, the throttle sensor 63 and the speed sensor 66. Respectively.

Next, at step 102, it is judged if the engine 1 is in the idle operation state. This determination is made based on the throttle opening TA read this time, the engine speed NE, and the like. Here, in the idle operation state, in step 103,
In order to drive the VVT 23 and delay the opening / closing timing of the intake valve 8, the first OSV 53 is turned off and the second OSV 54 is turned on. Then, after the processing of step 103 is completed, the subsequent processing is once completed.

On the other hand, when it is determined in step 102 that the engine is not in the idle operation state, in step 104, the load equivalent value QN indicating the load state of the engine 1 is obtained from the intake air amount Q and the engine speed NE read this time. . That is, the result of dividing the intake air amount Q by the engine speed NE is set as the load equivalent value QN.

Further, in step 105, the engine 1 is determined based on the load equivalent value QN and the engine speed NE.
Calculate the operating area of. That is, it is calculated whether the engine 1 is in the low-speed, medium-speed, or high-speed operation region and whether the engine 1 is in the low-load, medium-load, or high-load operation region.

Then, in step 106, it is judged whether or not the operating region calculated this time is the "advancing region" in which the opening / closing timing of the intake valve 8 should be advanced.
This determination is made by referring to the VVT control map as shown in FIG. In this map, the medium-high speed operation region is set to a "retard region" in which the opening / closing timing of the intake valve 8 should be retarded in order to improve the output torque of the engine 1 regardless of the load region. . In addition, the low rotation and high load operation region is set to the “advance region” in which the opening / closing timing of the intake valve 8 should be advanced in order to improve the output torque of the engine 1. or,
In the low rotation speed and low load operation range excluding the idle operation range, the "advance range" in which the opening / closing timing of the intake valve 8 should be advanced in order to improve fuel efficiency and reduce hydrocarbon (HC) emission It is set. Further, the low rotation speed and medium load operation region is set to a "retardation region" in which the opening / closing timing of the intake valve 8 should be retarded in order to alleviate the occurrence of knocking and improve fuel efficiency.

Here, in the normal valve timing control, in the low revolution and medium load operation region, it is general to advance the opening / closing timing of the intake valve in order to improve the output torque. However, it has been confirmed that in the low rotation speed and medium load operation range, knocking is likely to occur and fuel efficiency is deteriorated by advancing the opening / closing timing of the intake valve 8. In that sense, the opening / closing timing of the intake valve 8 is set to be retarded in the low rotation speed and medium load operation region. Further, in this VVT control map, the settings of the "advance angle region" and the "retard angle region" in the low rotation speed operation region are set so as to match the graph as shown in FIG. That is, the graph of FIG. 8 corresponds to the graph of FIG. 9 described above, and the characteristic curve when the opening of the intake valve 8 is advanced and the characteristic curve when the intake valve 8 is retarded are respectively indicated by broken lines and 2 It is indicated by a dashed line. In this graph, the output torque is relative to the load equivalent value QN of the engine 1.
Then, at the intersection where the two characteristic curves intersect, the characteristic curve of the advance angle on the side of small output torque has better fuel economy than that on the side of the intersection, and the characteristic curve of the angle of retard on the side of large output torque than the intersection Fuel consumption is improving. In this embodiment, by controlling the opening / closing timing of the intake valve 8 by using a VVT control map as shown in FIG. 7, as shown by a solid line in the graph of FIG. Fuel consumption changes according to the characteristic curve of. Further, on the side of large output torque from the intersection, the fuel consumption changes according to the characteristic curve of the retard angle until before the full load.

If the operating region of the engine 1 is in the "advance region" in step 106, the VVT 23 is driven in step 107 to advance the opening / closing timing of the intake valve 8. OSV
53 is turned on and the second OSV 54 is turned off. Then, after the processing of step 107 is completed,
The subsequent processing is once ended.

On the other hand, in step 106, when the operating region of the engine 1 is not in the "advancing region", that is, in the "retarding region", the routine proceeds to step 103, where the same processing as described above is executed. After that, the subsequent processing is once terminated.

As described above, the valve timing control for changing the opening / closing timing of the intake valve 8 is executed. As described above, according to this embodiment,
In controlling the opening / closing timing of the intake valve 8, whether the operating region of the engine 1 is the "advancing region" or the "retarding region" is determined with reference to the VVT control map shown in FIG. Then, the first and second OSVs 53 and 54 are turned on / off in accordance with the result of the determination, so that V
The VT 23 is driven, and the opening / closing timing of the intake valve 8 is changed to the advance side or the retard side. In addition, the valve overlap between the intake valve 8 and the exhaust valve 9 is changed accordingly.

Therefore, when the engine 1 is in the operating range above the middle speed, the intake valve 8 is irrespective of the load range.
The opening and closing timing of is delayed. Therefore, the opening of the intake valve 8 is delayed immediately before shifting from the exhaust stroke to the intake stroke, and the valve overlap is reduced. In addition, the closing of the intake valve 8 is delayed before and after shifting from the intake stroke to the compression stroke. However, in this operating region, the momentum of the intake air is large and the inertial effect of the intake air is obtained, so the combustion chamber 4
The efficiency of filling the intake air with respect to is improved. Therefore, even if the closing of the intake valve 8 is delayed a little, the substantial amount of intake air taken into the combustion chamber 4 increases and the effective compression ratio increases. As a result, the output torque of the engine 1 can be improved.

On the other hand, when the engine 1 is in a low rotation and low load operation region, the opening / closing timing of the intake valve 8 is advanced except in the idle operation state. Therefore, the opening of the intake valve 8 immediately before the shift from the exhaust stroke to the intake stroke is accelerated, and the valve overlap becomes large. Further, the intake valve 8 is closed earlier before and after the shift from the intake stroke to the compression stroke. Therefore, in this operating region, although the intake air amount and momentum are small, the exhaust back blow (internal EGR) becomes large, the pumping loss is reduced accordingly, and the substantial intake air amount increases. The effective compression ratio becomes large. As a result, the output torque of the engine 1 can be improved and the fuel consumption can be improved. In addition, the combustion chamber 4 is increased by increasing the internal EGR.
Since the temperature of the intake air in the engine 1 rises, it is possible to suppress the generation of HC during the combustion of the air-fuel mixture.
It is possible to reduce the amount of HC discharged from the vehicle.

Further, in the idle operation state, the intake valve 8
Since the opening / closing timing of is retarded, the opening of the intake valve 8 immediately before the shift from the exhaust stroke to the intake stroke is delayed, and the valve overlap is reduced. Therefore, in this operating region, the intake air is properly introduced into the combustion chamber 4 in accordance with the amount and the momentum of the intake air, and the idle operation can be stabilized.

Further, when the engine 1 is in the low rotation and high load operation region, the opening / closing timing of the intake valve 8 is advanced. Therefore, the intake valve 8 opens faster before and after the shift from the exhaust stroke to the intake stroke, and the valve overlap increases. Further, the intake valve 8 is closed earlier before and after the shift from the intake stroke to the compression stroke. Therefore, in this operating region, the intake air that is once introduced into the combustion chamber 4 and then tries to escape decreases, and the effective intake ratio increases and the effective compression ratio increases even though the intake air has a small momentum. Become. As a result, the output torque of the engine 1 can be improved and the fuel consumption can be improved.

Further, when the engine 1 is in a low rotation and medium load operation region where knocking easily occurs, the opening / closing timing of the intake valve 8 is retarded. Therefore, the opening of the intake valve 8 before and after the shift from the exhaust stroke to the intake stroke is delayed, and the valve overlap is reduced. In addition, the closing of the intake valve 8 is delayed before and after shifting from the intake stroke to the compression stroke. Therefore, in this operating region, the intake air that is once introduced into the combustion chamber 4 and then tries to escape increases, and the effective intake air amount decreases and the effective compression ratio decreases. as a result,
It is possible to suppress the occurrence of knocking and improve fuel efficiency. In other words, in this embodiment, in the low rotation speed and medium load operation region where knocking is likely to occur, the opening and closing timing of the intake valve 8 is retarded, so that the occurrence of knocking can be suppressed, and fuel efficiency is also improved. Can be achieved. Therefore, knocking can be suppressed without using a knock sensor or a control program for executing the determination of knocking occurrence. Moreover, in this embodiment, as shown in the graph of FIG. 8, the fuel consumption changes in accordance with the advance characteristic curve on the side of the output torque smaller than the intersection of the advance characteristic curve and the retard characteristic curve. Will be done. Therefore, in this embodiment, unlike the case where the fuel consumption is deteriorated between the knocking occurrence point and the branch point as shown in the graph of FIG. 9, the fuel consumption is not sacrificed in order to suppress knocking. It is possible to improve fuel efficiency by just that much.

The present invention is not limited to the above-described embodiments, but can be implemented as follows with a part of the structure appropriately modified without departing from the spirit of the invention. (1) In the above embodiment, the hydraulic VVT 23 whose drive is switched by the two OSVs 53 and 54 is used. However, the present invention is not limited to this, and the VVT whose drive is switched using one OSV is used. May be.

(2) In the above-described embodiment, the VVT 23 whose drive is switched by hydraulic pressure is adopted, but the VVT whose drive is switched by a step motor may be adopted. (3) In the above embodiment, the VVT set in the "advance region" except for the idle operation region in the low rotation and low load operation regions and the "retard angle region" in the other operation regions.
A control map was used. On the other hand, in the VVT control map, it is possible to change the shape of the “advance region” appropriately, assuming that the basic features are the same.

[0054]

As described in detail above, according to the present invention, when the operating region of the internal combustion engine is the low rotation and low load region or the low rotation and high load region, the intake valve is opened and closed. The timing is advanced, and the opening / closing timing of the intake valve is retarded when the operating region is the region of low rotation and medium load, or the region of medium rotation or higher.

Therefore, in the operating range of low rotation and medium load where knocking is likely to occur, the opening / closing timing of the intake valve is retarded, so that the amount of intake air once introduced into the combustion chamber and then trying to escape increases, The effective intake ratio is reduced and the effective compression ratio is reduced. As a result, knocking can be suppressed without using a knock sensor or the like to determine the occurrence of knocking, and at the same time, deterioration of fuel efficiency can be suppressed, which is an excellent effect.

[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 showing a valve timing control device for an internal combustion engine in an embodiment embodying the present invention.

FIG. 3 is a cross-sectional view showing a configuration of a VVT or the like in one embodiment.

FIG. 4 is a block diagram showing a configuration of an ECU and the like in one embodiment.

FIG. 5 illustrates the relationship between the opening and closing timings of the intake valve and the exhaust valve in one embodiment, (a) is an explanatory view when the opening and closing timing of the intake valve is retarded, and (b) is an opening and closing timing of the intake valve. It is explanatory drawing at the time of advancing.

FIG. 6 is a flowchart illustrating a “valve timing control routine” executed by the ECU in the embodiment.

FIG. 7 is a VVT control map used to change the opening / closing timing of an intake valve in one embodiment.

FIG. 8 is a graph showing a characteristic curve when the opening timing of the intake valve is advanced and a characteristic curve when the opening timing of the intake valve is retarded in the relationship between the output torque of the engine and the fuel consumption in one embodiment. .

FIG. 9 is a graph showing a characteristic curve when the opening timing of the intake valve is advanced and a characteristic curve when the opening timing is retarded in the relationship between the output torque of the internal combustion engine and the fuel consumption in the prior art. .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 4 ... Combustion chamber, 6 ... Intake passage, 7 ... Exhaust passage, 8 ... Intake valve, 9 ... Exhaust valve, 23 ... Variable valve timing mechanism (VVT), 62
… Air flow meter, 63… Throttle sensor, 66…
Rotational speed sensors (62, 63, 66 compose operating state detecting means), 70 ... ECU (composing drive control means, operating area computing means, advance angle setting means and retard angle setting means).

Claims (1)

[Claims] 1. An intake valve and an exhaust valve, which are driven in synchronization with 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 to be variable. A driven variable valve timing mechanism, an operating state detecting means for detecting an operating state of the internal combustion engine, and the variable valve for changing the opening / closing timing of the intake valve based on the detection result of the operating state detecting means. A valve timing control device for an internal combustion engine, comprising: a drive control means for driving and controlling a timing mechanism; and an operating area calculating means for calculating an operating area of the internal combustion engine based on a detection result of the operating state detecting means. And a case where the calculation result of the operating region calculation means is a low rotation and low load region, or a low rotation and high load region An advance angle setting means for setting the opening / closing timing of the intake valve to be changed on the advance side by the control of the drive control means, and an operation result of the operation area operation means in a low rotation speed and medium load area Or a retard setting means for setting the opening / closing timing of the intake valve, which is to be changed by the control of the drive control means, to the retard side in the region of medium rotation or higher. A valve timing control device for an internal combustion engine.