JPH08270467A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent control delay related to valve timing at the decelerating time and to prevent the occurrence of a misfire and an engine stalling. CONSTITUTION: Variable mechanism (VVT) 25 continuously changes the valve timing of an intake valve 8 in order to change valve overlap. An electric control unit(ECU) 80 computes the control target value related to valve timing control according to the operating state of an engine 1 by referring to function data formed by predetermining the target value to the rotating speed and load of the engine 1. In order to obtain valve overlap suitable for the operating state, the ECU 80 controls the VVT 25 on the basis of the computed control target value. At the time of judging the engine 1 to be shifted into a sudden speed reducing state, on the other hand, the ECU 80 uses the control target value, changed to the suitable value, for the control of the VVT 25 instead of the control target value computed on the basis of the function data to forcibly minimize valve overlap.

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 controlling valve overlap by controlling the valve timing of at least one of an intake valve and an exhaust valve provided in an internal combustion engine.
More specifically, the present invention relates to a valve timing control device that continuously controls valve timing according to the operating state of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in a basic internal combustion engine, an intake valve and an exhaust valve provided in the engine open an intake passage and an exhaust passage communicating with a combustion chamber, respectively. These valve timings are uniquely synchronized with the rotation phase of the crankshaft, and eventually with the timing when the piston moves up and down. Therefore, the intake / exhaust amount in the combustion chamber depends on the opening degree of the throttle valve separately provided in the intake passage and the rotation speed of the engine.

On the other hand, in recent years, there is a device in which the valve timing can be changed so that the intake / exhaust amount in the combustion chamber can be adjusted with more freedom. This type of device comprises a variable mechanism for changing the valve timing and a computer for controlling the movement of the variable mechanism. The computer controls the valve timing of at least one of the intake valve and the exhaust valve by controlling the variable mechanism according to the operating state of the engine,
Therefore, the size of the valve overlap between the intake valve and the exhaust valve is controlled. By this control, the computer adjusts the mixture of fuel and air to be filled in the combustion chamber, optimizes the air-fuel ratio, and thus controls the output of the engine.

For example, the computer controls the variable mechanism so that the valve overlap becomes relatively large when the rotation speed of the engine is high to some extent. According to this control, the inertial effect of the intake air can be utilized, the efficiency of filling the combustion chamber with the intake air is increased, and the output of the engine is improved. On the other hand, the computer controls the variable mechanism so that the valve overlap becomes relatively small when the engine speed is low to some extent. According to this control, the exhaust gas once discharged from the combustion chamber is prevented from flowing back into the combustion chamber, the proportion of the residual exhaust gas in the combustion chamber, that is, the internal EGR is reduced, and the combustion failure of the air-fuel mixture is prevented. It

Japanese Patent Laid-Open No. 4-279705 discloses an example of the device. This device makes it possible to change the valve timing particularly continuously and arbitrarily according to the operating state of the engine. In this device, the computer calculates a control target value related to valve timing based on the engine speed, load, and other values. The computer detects the actual valve timing condition.
Then, the computer continuously controls the movement of the variable mechanism based on the detected value and the control target value so that the actual valve timing becomes the optimum valve timing according to the operating state of the engine. According to this control, for example,
The valve timing is controlled not only in response to the engine operating at high speed or in the engine operating at low speed, but the valve timing can be controlled in response to an intermediate state between these two states. it can.

As an example of this control, the computer uses function data which is predetermined in relation to various parameters relating to the operating state and a control target value or a value (target displacement angle) related thereto. For example, the computer calculates the value of the target displacement angle VTT based on the function data shown in the graph of FIG. This graph shows the optimum target displacement angle VT with respect to the engine speed NE and the load LD.
The relationship of T, which is an experimentally determined relationship, is shown. Then, the computer calculates the value of the target displacement angle VTT based on the values of the engine rotation speed NE and the load LD detected at that time, and controls the variable mechanism based on the calculation result.

[0007]

However, in the device of the above publication, when the above function data is applied,
The computer always tries to determine the target displacement angle VTT based on the function data when the engine is operating. Therefore, even if the operating state of the engine suddenly changes, the computer follows the change of the operating parameters (here, the engine rotation speed NE and the load LD) obtained during the change, and the target displacement angle VTT. Will be calculated. Therefore, in particular, as shown by the arrow in FIG. 7, when the engine decelerates from a high rotation speed or a high load state, there is a risk of a response delay in the control of the valve timing by the computer. That is,
At the time of deceleration, although the optimum value of the valve overlap demanded immediately by the engine is a relatively small value, the computer is based on the value of the target displacement angle VTT calculated at any time during the process until the deceleration is completed. Try to control the variable mechanism. As a result, despite the deceleration, the valve overlap may temporarily become excessive, combustion of the air-fuel mixture in the combustion chamber may become unstable, and misfire or engine stall may occur. This is particularly remarkable when the degree of deceleration is rapid.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to quickly reduce the valve overlap at the time of deceleration of the internal combustion engine to prevent the response delay of the control relating to the valve timing. It is therefore an object of the present invention to provide a valve timing control device for an internal combustion engine, which makes it possible to prevent the occurrence of misfire and engine stall.

[0009]

In order to achieve the above object, according to the invention described in claim 1, as shown in FIG. 1, each of an intake passage M3 and an exhaust passage M4 communicating with a combustion chamber M2 of an internal combustion engine M1. To open the output shaft M of the internal combustion engine M1
A valve timing control device for controlling valve overlap by controlling the valve timing of at least one of an intake valve M5 and an exhaust valve M6 that operate in synchronization with the rotation of 1a according to the operating state of the internal combustion engine M1. A variable mechanism M7 for continuously changing the valve timing of at least one of the valves M5 and M6 in order to change the valve overlap.
And operating state detecting means M8 for detecting the operating state of the internal combustion engine M1 including at least the rotation speed of the output shaft M1a as one of the operating parameters, and function data for predetermining an optimum target value for the operating parameters. By referring to the control target value calculation means M9 for calculating the control target value for controlling the valve timing based on the detection result of the operation state detection means M8, and the valve overlap suitable for the operation state of the internal combustion engine M1. In the valve timing control device of the internal combustion engine, which is provided with the control means M10 for controlling the variable mechanism M7 based on the calculation result of the control target value calculation means M9 in order to obtain When it is determined that the deceleration state is entered based on the detection result of the operating state detection means M8, the valve overlap is determined. Control means M to the control to minimize
The target value changing means M11 for changing the control target value used in 10 is provided.

[0010]

According to the configuration of the above invention, as shown in FIG. 1, the intake valve M5 and the exhaust valve M6 operate in synchronization with the rotation of the output shaft M1a when the internal combustion engine M1 is operating. By this operation, each of the intake passage M3 and the exhaust passage M4 is opened, and intake and exhaust to the combustion chamber M2 are performed. At this time, the control target value calculating means M9 calculates the optimum control target value for controlling the valve timing based on the detection result of the operating state detecting means M8 by referring to the function data. Then, the control means M10 controls the variable mechanism M7 based on the calculated control target value. By this control, the valve timing of at least one of the valves M5 and M6 is changed, and the internal combustion engine M1 at that time is changed.
A valve overlap that matches the operating conditions of

Here, when the target value changing means M11 determines that the internal combustion engine M1 has shifted to a deceleration state of a predetermined degree,
The control setpoint value used in the control means M10 is changed in order to forcefully minimize the valve overlap.

Therefore, when the internal combustion engine M1 shifts to a deceleration state to some extent, instead of the control target value that should be calculated at any time based on the function data in the process until the deceleration is completed, based on the changed control target value. Variable mechanism M7
Is immediately controlled and the valve overlap is immediately changed to the minimum. Therefore, the valve overlap does not become excessive during the deceleration process, and the exhaust gas remaining in the combustion chamber does not increase.

[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 system for an automobile will be described in detail below with reference to FIGS.

FIG. 2 is a schematic configuration diagram showing a gasoline engine system according to the valve timing control system of this embodiment. An engine 1 as an internal combustion engine includes a plurality of cylinders 2. A piston 3 provided in each cylinder 2 is connected to a crankshaft 1a as an output shaft and can move up and down in each cylinder 2. In each cylinder 2, the upper side of the piston 3 constitutes a combustion chamber 4. Spark plugs 5 provided corresponding to the respective combustion chambers 4 ignite the air-fuel mixture introduced into the combustion chambers 4. Each of the intake port 6a and the exhaust port 7a provided corresponding to each combustion chamber 4 constitutes a part of the intake passage 6 and the exhaust passage 7. Each of the intake valve 8 and the exhaust valve 9 provided corresponding to each combustion chamber 4 has respective ports 6a and 7a.
Open each. Each of these valves 8 and 9 operates based on the rotation of different camshafts 10 and 11. The timing pulleys 12 and 13 provided at the tips of the camshafts 10 and 11 are the timing belt 1
It is connected to the crankshaft 1 a via 4.

When the engine 1 is in operation, the rotational force of the crankshaft 1a is transmitted through the timing belt 14 and the timing pulleys 12 and 13 to the camshafts 10 and 11, respectively.
It is transmitted to. When the camshafts 10 and 11 rotate, the valves 8 and 9 operate. The valves 8 and 9 can be operated at predetermined timings in synchronization with the rotation of the crankshaft 1a, that is, in synchronization with the intake stroke, the compression stroke, the explosion / expansion stroke, and the exhaust stroke according to the vertical movement of each piston 3. Has become.

An air cleaner 15 provided at the inlet of the intake passage 6 cleans the outside air taken into the passage 6. The injectors 16 respectively provided near the intake ports 6a inject fuel toward the intake ports 6a. When the engine 1 is operating, outside air is taken into the intake passage 6 via the air cleaner 15. At this time, each injector 16 injects fuel, so that the mixture of the fuel and the outside air is sucked into the combustion chamber 4 when the intake valve 8 opens the intake port 6a in the intake stroke. The air-fuel mixture sucked into the combustion chamber 4 explodes and burns when the spark plug 5 operates. As a result, the piston 3 operates, the crankshaft 1a rotates, and an output is obtained for the engine 1. The exhaust gas after combustion is led out from the combustion chamber 4 and discharged to the outside through the exhaust passage 7 when the exhaust valve 9 opens the exhaust port 7a in the exhaust stroke.

The throttle valve 17 provided in the intake passage 6 operates in conjunction with the operation of an accelerator pedal (not shown). By adjusting the opening of this valve 17,
The intake amount of outside air into the intake passage 6, that is, the intake air amount Q is adjusted. A surge tank 18 provided on the downstream side of the throttle valve 17 smoothes the pulsation of intake air. An intake air temperature sensor 71 provided near the air cleaner 15 detects the intake air temperature THA and outputs a signal corresponding to the detected value. A throttle sensor 72 provided in the vicinity of the throttle valve 17 detects the opening (throttle opening) TA of the valve 17 and outputs a signal corresponding to the detected value. The intake pressure sensor 73 provided in the surge tank 18 detects the pressure (intake pressure) PM of intake air in the surge tank 18 and outputs a signal corresponding to the detected value.

On the other hand, the catalytic converter 19 provided in the middle of the exhaust passage 7 purifies the exhaust gas by the built-in three-way catalyst 20. Oxygen sensor 74 provided in the exhaust passage 7
Detects the oxygen concentration Ox in the exhaust gas and outputs a signal corresponding to the detected value. A water temperature sensor 75 provided in the engine 1 detects a temperature of cooling water (cooling water temperature) THW for cooling the engine 1 and outputs a signal according to the detected value.

The distributor 21 is the igniter 2
The high voltage output from 2 is distributed to each spark plug 5 as an ignition signal for operating each spark plug 5. Therefore, the timing at which each ignition plug 5 is activated is determined by the timing at which the igniter 22 outputs a high voltage.

A rotor (not shown) built in the distributor 21 is rotated by a camshaft 11 which rotates in synchronization with the crankshaft 1a. Rotation speed sensor 76 provided on the distributor 21
Detects the rotational speed NE of the engine 1 (engine rotational speed) based on the rotation of the rotor, and outputs the detected value as a pulse signal. The cylinder discrimination sensor 77 provided in the distributor 21 detects the crank angle reference position GP at a predetermined ratio according to the rotation of the rotor, and outputs the detected value as a pulse signal. In this embodiment, the crankshaft 1a makes two revolutions for a series of four strokes of the engine 1. While the crankshaft 1a makes two revolutions, the rotation speed sensor 76 outputs a signal of one pulse for each crank angle of 30 °. Cylinder discrimination sensor 77 is 3
It outputs a signal of one pulse for each crank angle of 60 °.

In this embodiment, a hydraulically driven variable mechanism (hereinafter simply referred to as “VVT”) 25 provided on the timing pulley 12 changes the valve timing of the intake valve 8. The configurations of the VVT 25 and the hydraulic device for driving the VVT 25 will be described in detail with reference to FIGS. 3, 4 and 6A and 6B.

3 and 4 show the structure of the VVT 25 and its associated linear solenoid valve (LSV) 55.
The cylinder head 26 and the bearing cap 27 of the engine 1 rotatably support the camshaft 10 on its journal 10a. VVT25 is camshaft 1
It is integrated with a timing pulley 12 provided at the tip of 0. Two oil grooves 31 and 3 provided in the journal 10a
2 extends along the outer circumference of the journal 10a. The oil passages 33 and 34 provided in the bearing cap 27 supply lubricating oil to the journal 10a and the oil grooves 31 and 32. In this embodiment, as shown in FIG. 2, the oil pan 28, the oil pump 29, the oil filter 30 and the like provided in the engine 1 constitute a lubricating device for lubricating each part of the engine 1.

By operating the oil pump 29 in conjunction with the operation of the engine 1, the lubricating oil sucked up from the oil pan 28 is discharged from the oil pump 29. The discharged lubricating oil passes through the oil filter 30 and passes the LSV5
5, the oil is selectively pumped to the oil passages 33 and 34 and supplied to the oil grooves 31 and 32 and the journal 10a.

The substantially pulley-shaped timing pulley 12 and the cover 35 attached to the pulley 12 are the housing 3
Make up 6. The bottomed cylindrical cover 35 is the pulley 1
2 covers one side surface and the tip of the camshaft 10. The pulley 12 has a plurality of external teeth 37 on its outer circumference, and the boss 3 is provided at the center.
8 The pulley 12 mounted on the camshaft 10 at the boss 38 is rotatable relative to the shaft 10. The timing belt 14 described above has external teeth 37.
Leads to.

The cover 35 has a flange 39 on its outer periphery and a hole 40 in the center of its bottom. Multiple bolts 41
The pin 42 fixes the flange 39 to one side surface of the pulley 12. The lid 43 attached to the hole 40 is removable. The cover 35 has a plurality of inner teeth 35a on its inner circumference.

A space 44 surrounded by the pulley 12 and the cover 35 accommodates a cylindrical inner cap 45 and the like. Hollow bolts 46 and pins 47 fix the cap 45 to the tip of the camshaft 10. Peripheral wall 4 of the cap 45
5a encloses the boss 38, and both 45 and 38 are rotatable relative to each other. The peripheral wall 45a has a plurality of external teeth 45 on its outer periphery.
b.

A ring gear 48 interposed between the housing 35 and the cap 45 connects the housing 35 and the camshaft 10. The ring gear 48 housed in the space 44 has an annular shape and is movable along the axial direction of the camshaft 10. The ring gear 48 has a plurality of teeth 48a and 48b on its inner and outer circumferences, both of which form helical teeth. The ring gear 48 rotates relative to the shaft 10 by moving along the cam shaft 10. The inner teeth 48a of the ring gear 48 are the outer teeth 45b of the cap 45, and the outer teeth 48b of the ring gear 48 are the cover 3
5 meshes with the inner teeth 35a.

When the pulley 12 rotates, the housing 35 and the cap 4 connected by the ring gear 48 are connected.
6 and the cam shaft 10 and the housing 35 integrally rotate.

As shown in FIGS. 3 and 4, the space 44 has a first and second hydraulic chambers 49 defined by a ring gear 48.
50. The first hydraulic chamber 50 is located between the left end of the ring gear 48 and the bottom wall of the cover 37. Second hydraulic chamber 5
0 is located between the right end of the ring gear 48 and the pulley 12.

Here, in order to supply the hydraulic pressure by the lubricating oil to the first hydraulic chamber 49, the camshaft 10 has an oil passage 51 extending in the axial direction therein. This oil passage 51
Of the hollow bolt 46 communicates with the first hydraulic chamber 49 through the hole 46a of the hollow bolt 46. The base end of the oil passage 51 communicates with the oil groove 31 via an oil hole 52 extending in the radial direction of the camshaft 10.

On the other hand, in order to supply the hydraulic pressure by the lubricating oil to the second hydraulic chamber 50, the camshaft 10 has another oil passage 53 extending parallel to the oil passage 51 therein. Boss 38
The oil hole 54 formed at the position communicates between the second hydraulic chamber 50 and the oil passage 53.

In the above structure, the oil passage 33 and the oil hole 5
2, the oil passage 51, the hole 46a, and the like form a first hydraulic pressure supply passage for supplying the hydraulic pressure of the lubricating oil to the first hydraulic chamber 50. The oil passage 34, the oil passage 53, the oil hole 54, etc. are the second
For supplying hydraulic pressure by lubricating oil to the hydraulic chamber 51 of
Constitutes a hydraulic pressure supply passage. Here, the opening degree of the LSV 55 provided in the middle of both hydraulic pressure supply passages is duty-controlled to control the hydraulic pressure supplied to the hydraulic pressure chambers 49 and 50. FIG. 2 shows the connection relationship between the LSV 55, the oil pan 28, the oil pump 29, and the oil filter 30.

As shown in FIGS. 3 and 4, the casing 56 that constitutes the LSV 55 includes the first to fifth ports 57 and 5.
It has 8,59,60,61. The first port 57 communicates with the oil passage 33, and the second port 58 communicates with the oil passage 34. The third and fourth ports 59 and 60 are connected to the oil pan 28.
The fifth port 61 communicates with the discharge side of the oil pump 29 via the oil filter 30. The skewer-shaped spool 62 provided inside the casing 56 has four cylindrical valve bodies 62a. The spool 62 is capable of reciprocating along its axial direction. An electromagnetic solenoid 63 provided on the casing 56 moves the spool 62 between a first operating position shown in FIG. 3 and a second operating position shown in FIG. Spring 6 provided in casing 56
4 biases the spool 62 toward the first operating position.

Then, as shown in FIG. 4, the spring 6
By arranging the spool 62 in the second operating position against the biasing force of No. 4, the discharge side of the oil pump 29 communicates with the oil passage 33, and the oil passage 34 communicates with the oil pan 28. As a result, hydraulic pressure is supplied to the first hydraulic chamber 49,
The ring gear 48 rotates while moving in the axial direction against the oil remaining in the second hydraulic chamber 50. As a result, the relative rotational phase between the camshaft 10 and the housing 36 changes. Here, the rotational phase of the camshaft 10 leads that of the pulley housing 36. As a result, the valve timing of the intake valve 8 leads the rotation phase of the crankshaft 1a.

In this case, as shown in FIG. 6B, the valve timing of the intake valve 8 is relatively advanced, and the valve overlap between the intake valve 8 and the exhaust valve 9 in the intake stroke is relatively large. In this way, by controlling the hydraulic pressure supplied to the first hydraulic chamber 49, the ring gear 48 can be moved to the end position approaching the timing pulley 12 as shown in FIG. When the ring gear 48 is located at its end position, the valve timing of the intake valve 8 is most advanced and the valve overlap is largest.

On the other hand, as shown in FIG. 3, the discharge side of the oil pump 29 communicates with the oil passage 34 by arranging the spool 62 at the first operating position, and the oil passage 33 and the oil pan 28 are connected to each other. Communicate with each other. As a result, the second hydraulic chamber 50
To the first hydraulic chamber 49.
It rotates while moving in the axial direction against the oil remaining in the. As a result, the relative rotational phase between the camshaft 10 and the housing 36 changes in the opposite direction. here,
The rotation phase of the camshaft 10 lags behind that of the housing 36. As a result, the valve timing of the intake valve 8 lags behind the rotation phase of the crankshaft 1a.

In this case, as shown in FIG. 6 (a), the valve timing of the intake valve 8 is relatively delayed, and the valve overlap in the intake stroke is relatively small. In this embodiment, valve overlap is eliminated. In this way, by controlling the hydraulic pressure supplied to the second hydraulic chamber 50, the ring gear 48 can be moved to the end position approaching the cover 35, as shown in FIG.
When the ring gear 48 is located at the terminal position, the valve timing of the intake valve 8 is delayed most and the valve overlap is minimized.

By appropriately controlling the VVT 25 as described above, the valve timing of the intake valve 8, and thus the valve overlap, is controlled between the range shown in FIG. 6 (a) and the range shown in FIG. 6 (b). Can be changed continuously (steplessly).

Here, as shown in FIG. 2, the cam sensor 78 provided on the camshaft 10 detects the actual displacement angle (actual displacement angle) VT related to the rotation of the camshaft 10 and responds to the detected value. Output a signal. The cam sensor 78 includes a plurality of protrusions arranged on the cam shaft 10 at equal angular intervals, and a pickup coil arranged so as to face each protrusion. And the camshaft 10
Is rotated and each protrusion crosses the pickup coil, so that the pickup coil generates an electromotive force. The cam sensor 78 outputs the electromotive force as a pulse signal indicating the actual displacement angle VT.

The starter 23 provided in the engine 1 is used to apply a rotational force to the crankshaft 1a when the engine 1 is started, that is, to perform cranking.
Starter switch 79 provided in this starter 23
Detects the on / off state of the starter 23. As is well known, the starter 23 operates by operating an ignition switch (not shown). When the ignition switch is turned on to start the engine 1, the starter 23 is turned on. At this time, the starter switch 79 has a starter signal ST indicating its ON state.
Output A.

In this embodiment, the various sensors 71, etc. described above are used.
˜79 constitute the operating state detecting means of the present invention. Here, the electronic control unit (ECU) 80 constitutes the control target value calculating means, the control means and the target value changing means in the present invention. As shown in FIG. 2, the ECU 80 inputs signals output from the various sensors 71 to 79 described above. ECU
80 indicates each member 16, 22, 55 based on these signals.
Control each.

As shown in the block diagram of FIG. 5, the ECU
80 is a central processing unit (CPU) 81, a read-only memory (ROM) 82, a random access memory (RAM)
83 and a backup RAM 84. ECU8
Reference numeral 0 forms a logical operation open circuit in which these units 81 to 84, an external input circuit 85 including an A / D converter, an external output circuit 86 and the like are connected by a bus 87. ROM 82
Stores a predetermined control program or the like in advance. RAM83
Temporarily stores the calculation result and the like of the CPU 81. The backup RAM 84 stores previously stored data. The sensors 71 to 79 described above are connected to the external input circuit 85. The above-mentioned members 16, 22, 55 are the external output circuit 8
Connect to 6.

The CPU 81 reads the signals of the respective sensors 71-79 input via the external input circuit 85 as input values. The CPU 81 controls the respective members 16, 22, 55 and the like to execute fuel injection amount control, ignition timing control, valve timing control and the like based on these input values.

Here, the fuel injection amount control means the engine 1
The amount of fuel supplied to the combustion chamber 4 is controlled by controlling each injector 16 based on the target value calculated according to the operating state of. What is ignition timing control?
The ignition timing of each spark plug 5 is controlled by controlling the igniter 22 based on the target value calculated according to the operating state of the engine 1. The valve timing control is performed by controlling the LSV 55 on the basis of the value of the drive duty ratio DVT as the control target value calculated according to the operating state of the engine 1.
5 to control the valve timing of the intake valve 8 and thus the valve overlap.

Next, the valve timing control described above will be described with reference to FIGS. FIG. 8 is a flowchart showing the "valve timing control routine". E
The CU 80 periodically executes this routine at predetermined time intervals.

When the processing shifts to this routine, in step 100, the ECU 80 causes the sensors 73, 76,
Intake pressure PM, engine speed NE, actual displacement angle VT and starter signal STA based on signals from 78 and 79.
Read each value of.

Then, in step 105, the ECU
Reference numeral 80 determines whether or not the start of the engine 1 is completed.
The ECU 80 makes this determination based on the values of the engine rotational speed NE and the starter signal STA read this time. The value of the engine speed NE is larger than a predetermined value,
When the starter signal STA indicates “OFF”, the EC
U80 determines that the start of the engine 1 is completed. If the engine 1 has not been started, EC
U80 shifts the processing to step 120. Engine 1
If the startup of the above is completed, the ECU 80 shifts the processing to step 110. In this embodiment, step 105
The ECU 80 that executes the process of (1) corresponds to a determination unit for determining the completion of starting the engine 1.

In step 110, the ECU 80 calculates the change in the engine speed NE per unit time, that is, the value of the change in rotation speed ΔNE. The ECU 80 calculates the difference between the value of the engine rotational speed NE read last time and the value of the engine rotational speed NE read this time as the rotational speed change ΔNE.
It is calculated as the value of. Therefore, this rotation speed change ΔNE
Is a positive value when the engine 1 is decelerating, and is a negative value when the engine 1 is accelerating. In this embodiment, the ECU 80 that executes the process of step 110 determines that the rotation speed change ΔN of the engine 1 is ΔN.
It corresponds to a calculation means for calculating E.

In step 115, the ECU 80 determines whether or not the value of the rotation speed change ΔNE is greater than or equal to a predetermined reference value (positive value) α. That is, the ECU 80 determines whether the engine 1 has transitioned to a rapid deceleration state of a predetermined degree. Here, when the value of the rotation speed change ΔNE is equal to or greater than the reference value α, the engine 1 has transitioned to a rapid deceleration state of a predetermined degree, and therefore the ECU 80 executes the processing in step 1
Move to 20. If the value of the rotational speed change ΔNE is smaller than the reference value α, the engine 1 is not in a deceleration state of a predetermined degree, and therefore the ECU 80 executes the process in step 130.
Move to. The ECU 80 that executes the processing of step 115 in this embodiment corresponds to a determination means for determining that the engine 1 has shifted to the deceleration state.

In step 120 after shifting from steps 105 and 115, the ECU 80 sets the value of the drive duty ratio DVT for controlling the duty of the LSV 55 to "0".
% ". That is, the ECU 80 sets the value of the drive duty ratio DVT to "0%" in step 120 when the engine 1 has not been started yet or when the engine 1 has transitioned to a rapid deceleration state of a predetermined degree. is there. The ECU 80 that executes the processing of steps 115 and 120 in this embodiment corresponds to the target value changing means of the present invention.

On the other hand, in step 130 after shifting from step 115, the ECU 80 calculates the VV based on the values of the intake pressure PM and the engine speed NE which are read this time.
The value of the target displacement angle VTT for controlling T25 is calculated. The ECU 80 calculates the value of this target displacement angle VTT as shown in FIG.
It is calculated by referring to the function data shown in the graph. In this function data, the target displacement angle VTT is experimentally optimally determined in advance from the relationship between the engine rotation speed NE and the load LD of the engine 1 obtained from the intake pressure PM and the engine rotation speed NE. The ECU 80 that executes the process of step 130 in this embodiment corresponds to a calculation unit that calculates the value of the target displacement angle VTT that is suitable for the current operating state of the engine 1.

Then, in step 135, the ECU
Reference numeral 80 determines whether or not the value of the target displacement angle VTT calculated this time is approximately “0 °”, that is, whether or not the valve timing should be controlled to the most delayed state (the most retarded state). An EC that executes the processing of step 135 in this embodiment.
U80 corresponds to a judgment means for judging whether or not the valve timing should be controlled to the most retarded state. Here, when the value of the target displacement angle VTT is approximately “0 °”, the ECU 80 shifts the processing to step 140 in order to keep the valve timing in the most retarded state. In step 140, the ECU 80 executes the "holding control of the most retarded angle" by setting the drive duty ratio DVT to the predetermined value γ. Here, the predetermined value γ is a value obtained by learning. The holding control is control for holding the displacement angle of the camshaft 10 to be controlled by the VVT 25 at the value of the target displacement angle VTT.

The contents of the holding control will be briefly described. ECU
80 is the drive duty ratio DV calculated at that time
By controlling the LSV 55 based on the value of T, the value of the actual displacement angle VT is made to match the value of the target displacement angle VTT. The ECU 80 determines that the value of the actual displacement angle VT is the target displacement angle V
A holding duty for holding the rotation phase of the camshaft 10 from the value of the drive duty ratio DVT that should displace the rotation phase of the camshaft 10 from the value of the drive duty ratio DVT that should be output to the LSV 55 when it matches the value of TT. Switch to the value of the ratio DVTH. The value of this holding duty ratio DVTH is L in order not to change the supply state of the hydraulic pressure to both the pressure chambers 49 and 50 of the VVT 25 from the current state.
It corresponds to the command value to be output to the SV55. From the value of this holding duty ratio DVTH, LSV55 and VVT2
In order to eliminate the effects of tolerances and changes over time related to 5,
The ECU 80 determines the holding duty ratio DVTH based on a holding duty learning value GDVTH described later.
Then, the ECU 80 duty-controls the LSV 55 based on the value of the holding duty ratio DVTH, so that V
The displacement angle of the camshaft 10 by the VT 25 does not advance or lag, and is maintained at the value of the target displacement angle VTT immediately before the holding control is started.

Here, "holding control of the most retarded angle" means VVT
25 is a control for holding the ring gear 48 at the end position on the most retarded angle side. It is also conceivable that the ring gear 48 is pressed against the cover 35 with a strong force and stopped at the end position on the most retarded angle side. However, in this case, a strong force is required when the ring gear 48 starts moving to the opposite advance side, and the responsiveness is not good. Therefore, in this "maximum retardation holding control", although the ring gear 48 is pressed against the cover 35 with a certain amount of force, the ECU 80 adjusts so that good response can be obtained when the gear 48 starts moving toward the advance side. LS
By controlling V55, the supply of hydraulic pressure to both pressure chambers 49, 50 is adjusted. Step 14 in this example
The ECU 80 that executes the process of 0 corresponds to a control unit that executes the holding control for the most retarded angle.

On the other hand, when the value of the target displacement angle VTT is not approximately "0 °" in step 135, the ECU 8
0 executes the processing of steps 150 to 180 in order to perform feedback control of the displacement angle of the camshaft 10 or hold control in a constant state other than the most retarded angle.

That is, in step 150, the ECU 8
0 determines whether the deviation value (absolute value) between the value of the target displacement angle VTT calculated this time and the value of the actual displacement angle VT read this time is less than or equal to a predetermined reference value β. Here, “3 °” can be applied as the reference value β. The ECU 80 that executes the processing of step 150 in this embodiment
Is equivalent to a determination means for determining the magnitude of the deviation of the actual displacement angle VT from the target displacement angle VTT. When this deviation value is larger than the reference value β, the ECU 80 shifts the processing to step 160.

In step 160, the ECU 80 learns and updates the holding duty learning value GDVTH. That is,
The ECU 80 calculates the value of the target displacement angle VTT and the actual displacement angle VT.
Is compared and the holding duty learning value GDVTH is learned by increasing or decreasing the holding duty learning value GDVTH from the result of the comparison. Step 16 in this example
The ECU 80 that executes the process of 0 corresponds to learning means for learning the holding duty learning value GDVTH for holding control.

Then, at step 170, the ECU
Reference numeral 80 calculates the value of the drive duty ratio DVT according to the following calculation formula. DVT = (VTT-VT) * KP + GDVTH Here, "KP" is a constant and corresponds to a gain of proportional control.

On the other hand, when the deviation value is equal to or smaller than the reference value β in step 150, the ECU 80 drives the holding duty learning value GDVTH learned up to now in order to execute the holding control in step 180. It is set as the value of the duty ratio DVT. The ECU 80 that executes the processing of steps 130 to 180 in this embodiment
Corresponds to the control target value calculation means of the present invention.

Then, steps 120, 140 and 17
In step 190 after moving from 0,180, EC
U80 duty-controls the LSV 55 based on the value of the holding duty ratio DVT calculated this time,
The displacement angle of the camshaft 10 is controlled. Where EC
U80 converts the value of the drive duty ratio DVT into a current value for duty-controlling the LSV55,
The duty of the LSV 55 is controlled. As a result, VVT2
5 controls the displacement angle of the camshaft 10, controls the timing of the intake valve 8 and controls the valve overlap. The ECU 80 that executes the processing of step 190 in this embodiment corresponds to the control means of the present invention. Then, after executing the processing of step 190, the ECU 80
Waits for the next control cycle and restarts the processing from step 100.

Next, the operation and effect of the valve timing control device constructed as described above will be described. During operation of the engine 1, the intake valve 8 and the exhaust valve 9 operate in synchronization with the rotation of the crankshaft 1a. By this operation, each of the intake port 6a and the exhaust port 7a is opened to intake and exhaust the combustion chamber 4. At this time, the ECU 80 calculates the optimum value of the target displacement angle VTT related to the valve timing control by referring to the function data shown in FIG. 7. Then, the ECU 80 calculates the value of the drive duty ratio DVT as the control target value based on the calculated value of the target displacement angle VTT. ECU
80 is LS based on the value of this drive duty ratio DVT.
By controlling V55, VTT25 is controlled.
As a result, the valve timing of the intake valve 8 is changed, and a valve overlap that matches the operating state of the engine 1 at that time is obtained.

When the engine speed NE is high and the load LD is high to some extent, the VVT 25 is controlled so that the valve overlap becomes large. By this control, it is possible to improve the efficiency of filling the combustion chamber 4 with intake air by utilizing the inertial effect of intake air in the intake passage 6, and to improve the output of the engine 1. On the other hand, when the engine speed NE is low and the load LD is small, the VVT 25 is controlled so that the valve overlap becomes small. By this control, the ratio of the internal EGR in the combustion chamber 4 can be reduced, and the combustion failure of the air-fuel mixture can be prevented. With respect to other relationships between the engine rotation speed NE and the load LD, the optimum valve overlap can be obtained, and the output of the engine 1 can be improved and the combustion failure of the air-fuel mixture can be prevented.

Here, when the ECU 80 determines that the engine 1 has suddenly decelerated, the value of the drive duty ratio DVT used to control the LSV 55 is forcibly minimized in the valve overlap. To force "0
% ". Therefore, when the engine 1 shifts to a rapid deceleration state, "0%" is used instead of the value of the drive duty ratio DVT that should be calculated at any time based on the function data shown in FIG. 7 in the process until the deceleration is completed. The VVT 25 is immediately controlled based on the drive duty ratio DVT changed to, and the valve overlap is quickly changed to the minimum. Therefore, the valve overlap does not become excessive in the process until the deceleration of the engine 1 is completed, and the internal EGR in the combustion chamber 4 does not increase. As described above, by promptly reducing the valve overlap at the time of deceleration of the engine 1, it is possible to prevent the response delay related to the control of the valve timing. As a result, it is possible to prevent the occurrence of misfire and engine stall due to the increase in internal EGR.

Further, in this embodiment, the ECU 80 forcibly sets the drive duty ratio DVT to "0%" even when the engine 1 is started, so that the internal EGR becomes excessive at the time of starting and a start failure occurs. There is no such thing.

Further, in this embodiment, the ECU 80 executes the holding control as necessary to stabilize the displacement angle of the camshaft 10 by the VVT 25 to the value of the target displacement angle VTT immediately before the holding control is started. Can be kept. Moreover, the ECU 80 sets the holding duty ratio DVTH used in the holding control to the holding duty learning value GDV.
Determine based on TH. Therefore, the holding duty ratio D
From the value of VTH, it is possible to eliminate the influence of the tolerance and the change with time of the LSV 55 and the VVT 25, and it is possible to always perform the optimum holding control.

In addition, in this embodiment, also in the feedback control other than the holding control, the ECU 80 uses the holding duty learning value GDVTH as one parameter for calculating the drive duty ratio DVT. Therefore,
Even during feedback control, the drive duty ratio DVT
It is possible to eliminate the influence of the tolerance and the change with time of the LSV 55 and the VVT 25 from the value of, and it is possible to always carry out the optimal feedback control.

The present invention can be embodied in the following other embodiments. In another embodiment described below, the same operation and effect as the above embodiment can be obtained. (1) In the above embodiment, the valve overlap is changed by changing only the valve timing of the intake valve 8 by the VVT 25 provided on the intake side camshaft 10. On the other hand, a VVT is provided on the camshaft 11 on the exhaust side, and the exhaust valve 9 is provided by the VVT.
The valve overlap may be changed by changing only the valve timing of. Alternatively, the valve overlap is changed by providing VVTs on both the intake side and exhaust side camshafts 10 and 11 and changing the valve timings of the intake valve 8 and the exhaust valve 9 by the respective VVTs. Good.

(2) In the above embodiment, the VVT 25 driven by hydraulic pressure is used, but it is also possible to use VVT driven by an electric actuator such as a step motor.

(3) In the above-described embodiment, the fact that the operating state of the engine 1 has shifted to the deceleration state of a predetermined degree is judged based on the rotational speed change ΔNE. In contrast,
The transition to the deceleration state of the engine 1 may be determined based on the amount of change in the intake pressure PM per unit time or the amount of change in the throttle opening TA per unit time. Furthermore, while the engine 1 is operating, the throttle valve 1
When it is detected that 7 is fully closed, it may be determined that the engine 1 has shifted to a deceleration state of a predetermined degree.

(4) In this embodiment, when it is determined that the operating state of the engine 1 has shifted to a deceleration state of a predetermined degree, the value of the drive duty ratio DVT is set to "0" in order to forcibly eliminate the valve overlap. I changed it to "%". On the other hand, when it is determined that the operating state of the engine 1 has shifted to a deceleration state of a predetermined degree, the drive duty ratio DV is set in order to forcibly minimize the valve overlap.
The value of T may be changed to an appropriate value other than "0%".

[0071]

According to the invention described in claim 1, it is premised on the valve timing control device for controlling the valve overlap by controlling the valve timing according to the operating state of the internal combustion engine. Then, the control target value is calculated based on the operating state of the internal combustion engine by referring to the optimally determined function data in advance. The variable mechanism is controlled based on the calculated control target value in order to obtain the valve overlap that matches the operating state of the internal combustion engine. Further, when it is determined that the operating state of the internal combustion engine has shifted to a deceleration state of a predetermined degree, the control target value is changed to forcibly minimize the valve overlap.

Therefore, when the internal combustion engine shifts to the deceleration state, the valve overrun is set based on the changed control target value instead of the control target value that should be calculated at any time based on the function data until the deceleration is completed. The lap is quickly changed to the minimum. As a result, it is possible to prevent a response delay related to the control of the valve timing, and thus it is possible to prevent the occurrence of misfire and engine stall.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram showing a gasoline engine system according to an embodiment.

FIG. 3 is a cross-sectional view showing the structure of VVT and LSV.

FIG. 4 is a cross-sectional view showing structures of VVT and LSV.

FIG. 5 is a block diagram showing a configuration of an ECU.

6A and 6B are explanatory views showing changes in valve overlap.

FIG. 7 is a graph showing function data relating to a target displacement angle.

FIG. 8 is a flowchart showing a “valve timing control routine”.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 1a ... Crankshaft as an output shaft, 4 ... Combustion chamber, 6 ... Intake passage, 7 ... Exhaust passage, 8 ... Intake valve, 9 ... Exhaust valve, 25 ... Variable mechanism (VVT), Reference numeral 73 ... Intake pressure sensor, 76 ... Rotation speed sensor, 79 ... Starter switch (73, 76, 79 and the like constitute an operating state detecting means), 80 ... ECU (80
Constitutes a control target value calculating means, a control means and a target value changing means).

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location F02D 45/00 322 F02D 45/00 322B (72) Inventor Chika Kato 1st Toyota Town, Aichi Prefecture Toyota Town Toyota Auto Car Co., Ltd. (72) Inventor Atsushi Goto 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Inventor Tadahisa Naganawa 1, Toyota Town, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A valve timing of at least one of an intake valve and an exhaust valve, which operates in synchronization with rotation of an output shaft of the internal combustion engine to open an intake passage and an exhaust passage communicating with a combustion chamber of the internal combustion engine. A valve timing control device for controlling valve overlap by controlling according to an operating state of an internal combustion engine, wherein at least one valve timing of both valves is changed in order to change the valve overlap. A variable mechanism for making it continuously changeable, an operating state detecting means for detecting an operating state of the internal combustion engine including at least the rotation speed of the output shaft as one of operating parameters, and an optimum for the operating parameters Control of the valve timing by referring to function data in which various target values are predetermined. Control target value calculation means for calculating a control target value according to the detection result of the operating state detection means, and the control target value calculation for obtaining the valve overlap adapted to the operating state of the internal combustion engine. A valve timing control device for an internal combustion engine, comprising: a control means for controlling the variable mechanism based on a calculation result of the means, wherein the operating state indicates that the operating state of the internal combustion engine has shifted to a deceleration state of a predetermined degree. A target value changing means for changing the control target value used in the control means to forcibly minimize the valve overlap when judged based on the detection result of the detection means. A valve timing control device for an internal combustion engine, comprising: