JPH09256880A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the engine speed for an internal combustion engine in the idle operation with sufficient adjustment range without raising the exhaust temperature different from the measures by controlling the ignition timing when the engine speed to be controlled by an idle speed control(ISC) device is excessive. SOLUTION: A variable valve timing(VVT) 25 changes the valve timing of an air intake valve 8 to change the valve overlap. An idle speed control valve(ISCV) 24 adjusts the quantity QA of air flowing in a bypass passage 23. An engine speed sensor 76 detects the engine speed NE. When the ISC is failed, the engine speed NE is increased. An electronic control unit(ECU) 80 judges whether or not the engine speed NE is excessive over the prescribed value NE1. The air intake valve 8 performs the delay by controlling the VVT 25 based on the judgment to obtain the negative valve overlap. The quantity of air to be sucked into a combustion chamber 4 is reduced thereby.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air adjusting means for adjusting the amount of air flowing through an intake passage during idle operation of an internal combustion engine, and an intake valve and an exhaust valve provided in each of the intake passage and the exhaust passage. The present invention relates to an internal combustion engine having a variable mechanism that can change opening / closing characteristics. More specifically, the present invention relates to a control device for an internal combustion engine that controls the intake adjustment means and the variable mechanism.

[0002]

2. Description of the Related Art In a conventional internal combustion engine for a vehicle (engine), the idle speed of the engine during idle operation is controlled to a predetermined target value regardless of the engine temperature condition, load condition, etc. There is a speed control (ISC) device. As an example, this ISC device
A bypass passage that connects the upstream side and the downstream side of the throttle valve in the intake passage, a valve (ISCV) for adjusting the amount of air flowing through this passage, a sensor for detecting the engine rotation speed, and a sensor for the sensor. And a computer for controlling the ISCV based on the detected value.
The computer controls the ISCV during the idle operation of the engine in which the throttle valve is fully closed, whereby the amount of air flowing through the intake passage is adjusted and the engine speed is adjusted.

However, when some abnormality occurs in the ISC device, there is a possibility that an actual engine rotation speed exceeds a predetermined target value and becomes high, that is, so-called overrun. For example, one of the abnormalities is that the ISCV fails in the fully opened state. If an overrun occurs, the engine torque will increase accordingly. Therefore, when the driver attempts to start the vehicle, a feeling of acceleration more than expected, that is, a feeling of "jumping out" of the vehicle is accompanied.

Japanese Unexamined Patent Publication No. 60-156979 discloses an "ignition timing control device for an internal combustion engine" for solving this type of problem. This device reduces the output of the engine by retarding the ignition timing of the combustible mixture supplied to the engine when the rotational speed of the engine exceeds a predetermined allowable value during idling of the engine. This prevents the occurrence of overrun during idle operation.

[0005]

However, in the device of the above publication, the ignition timing is retarded, so that the temperature of the exhaust gas tends to rise. If this state continues for a long time, the catalyst provided in the exhaust passage may be thermally deteriorated. On the other hand, since the engine torque range that can be adjusted by controlling the ignition timing is relatively small, ISC
In the ISC device in which the flow range of the bypass passage to be adjusted by V is set large, there is a limit to the value of the engine torque that can be reduced by the ignition timing retard control. Therefore, it is impossible to sufficiently suppress the above-described feeling of the vehicle popping out.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to take measures against ignition timing control when the rotational speed of an internal combustion engine controlled by an ISC device becomes excessive during idle operation. Another object of the present invention is to provide a control device for an internal combustion engine capable of reducing the rotational speed of the internal combustion engine with a sufficient adjustment range without increasing the exhaust gas temperature.

[0007]

In order to achieve the above object, in the invention described in claim 1, as shown in FIG.
An intake passage M2 and an exhaust passage M3 communicating with the combustion chamber M1,
An intake valve M4 for selectively opening and closing between the combustion chamber M1 and the intake passage M2, as well as the combustion chamber M1 and the exhaust passage M
An exhaust valve M5 for selectively opening and closing between 3 and
A variable mechanism M6 for varying the opening / closing characteristics of at least one of the intake valve M4 and the exhaust valve M5, and intake adjusting means M7 for adjusting the amount of air flowing through the intake passage M2.
An internal combustion engine M8 having a control means for controlling the intake air adjusting means M7 so that the rotational speed of the internal combustion engine M8 detected by the rotational speed detecting means M9 becomes a predetermined value during idle operation of the internal combustion engine M8. In the control device including the first control unit M10, the rotation speed detected by the rotation speed detection unit M9 is controlled based on the operation of the intake air adjustment unit M7 during the idle operation of the internal combustion engine M8, and exceeds a predetermined value. Judgment means M11 for judging whether or not it is excessive
And a second control means M12 for controlling the variable mechanism M6 so that the rotation speed decreases when the determination means M11 determines that the rotation speed is excessive. .

According to the above construction, when the internal combustion engine M8 is idle, the first control means M10 controls the intake adjusting means M7 based on the detection result of the rotational speed detecting means M9, so that the intake passage M2 is passed through. The amount of air flowing into the combustion chamber M1 is adjusted, and the rotation speed of the internal combustion engine M8 is controlled to be a predetermined value.

If the intake adjusting means M7 or the first control means M10 becomes defective due to some cause and the rotational speed of the internal combustion engine M8 exceeds a predetermined value and becomes excessive, that is the judgment means. It is judged by M11. In response to the determination, the second control means M12 controls the variable mechanism M6 to change the opening / closing characteristics of at least one of the intake valve M4 and the exhaust valve M5, thereby adjusting the amount of air flowing into the combustion chamber M1. The rotation speed of the internal combustion engine M8 decreases.

Therefore, since the rotational speed of the internal combustion engine M8 is reduced by adjusting the amount of air flowing into the combustion chamber M1,
Unlike the case where the ignition timing is retarded, the temperature of the exhaust gas discharged from the combustion chamber M1 to the exhaust passage M3 does not rise. By setting the opening / closing characteristics of the intake / exhaust valve by the variable mechanism M6, the adjustment range of the air amount can be set to a relatively large value.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which a 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 control device of this embodiment. The 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 and is vertically movable in each cylinder 2. In each cylinder 2, the upper side of the piston 3 forms a combustion chamber 4. The ignition plugs 5 provided for each of the combustion chambers 4 ignite a mixture of air and fuel 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 in each combustion chamber 4 selectively opens and closes each port 6a, 7a. Each of these valves 8, 9 has a different camshaft 1
It operates based on the rotation of 0,11. Each camshaft 1
Timing pulleys 12 and 13 provided at the tips of 0 and 11 are connected to the crankshaft 1a via a timing belt 14.

When the engine 1 is in operation, the torque of the crankshaft 1a is generated by the timing belt 14 and the pulleys 1.
The power is transmitted to the respective camshafts 10 and 11 via the second and third camshafts. As each of the camshafts 10 and 11 rotates,
Each valve 8 and 9 operates. Each of the valves 8 and 9 is operable in synchronization with the rotation of the crankshaft 1a, that is, at a predetermined valve timing and a valve lift corresponding to the vertical movement of each piston 3.

The air cleaner 15 provided at the inlet of the intake passage 6 cleans the outside air taken into the passage 19. The injectors 16 provided near the respective intake ports 6a inject fuel toward the intake ports 6a. When the engine 1 is operating, the outside air is the air cleaner 15
It is taken into the intake passage 6 via. At this time, when each injector 16 injects fuel, a mixture of the fuel and the outside air is sucked into the combustion chamber 4 when the intake valve 6 opens the intake port 6a in the intake stroke. The air-fuel mixture sucked into the combustion chamber 4 explodes and burns when the ignition 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 drawn out of the combustion chamber 4 when the exhaust valve 7 opens the exhaust port 7a in the exhaust stroke, and is discharged to the outside through the exhaust passage 7.

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 the valve 17, the amount of outside air taken into the intake passage 6, that is, the intake air amount QA is adjusted. A surge tank 18 provided downstream of the throttle valve 17 smoothes the pulsation of the 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 near the throttle valve 17 detects an opening degree (throttle opening degree) TA of the valve 17 and outputs a signal corresponding to the detected value. This sensor 72 is a throttle valve 1
When 7 is fully closed, it outputs an idle signal IDS indicating that. An intake pressure sensor 73 provided in the surge tank 18 detects a pressure (intake pressure) PM of intake air in the 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 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 74 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 the ignition plugs 5 for operating the respective ignition plugs 5. Therefore, the timing at which each ignition plug 5 is operated 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 in distributor 21
Detects the engine rotation speed NE based on the rotation of the rotor and outputs the detected value as a pulse signal. The rotation speed sensor 76 constitutes the rotation speed detecting means of the present invention. The cylinder discrimination sensor 77 provided in the distributor 21 detects the reference position GP of the crank angle CA at a predetermined ratio according to the rotation of the rotor, and also outputs the predetermined value as a pulse signal. In this embodiment, the crankshaft 1a makes two rotations for a series of four strokes of the engine 1. While the crankshaft 1a makes two rotations,
The rotation speed sensor 76 outputs a signal of 1 pulse at 30 ° CA. The cylinder discrimination sensor 77 outputs a signal of one pulse every 360 ° CA.

Bypass passage 23 provided in the intake passage 6
Connects the upstream side and the downstream side of the throttle valve 17 bypassing the throttle valve 17. A rotary idle speed control valve (I
SCV) 24 adjusts the opening of the passage 23. The bypass passage 23 and the ISCV 24 form the intake air adjusting means of the present invention. The ISCV 24 operates to stabilize the operation of the engine 1 when the engine 1 is idling and the throttle valve 17 is fully closed. The opening of the ISCV 24 is adjusted by operating based on a predetermined command signal.
Based on this opening, the combustion chamber 4 is passed through the bypass passage 23.
The intake air amount QA taken in is adjusted, and the engine speed NE is controlled. Therefore, when the engine 1 is idling, the intake air amount QA of the intake passage 6 is adjusted by the ISCV 24 separately from the throttle valve 17.

The cam sensor 78 provided on the camshaft 10 detects an actual displacement angle (actual displacement angle) VT related to the rotation of the camshaft 10 and outputs a signal corresponding to the detected value. The cam sensor 78 includes a plurality of projections arranged at equal angular intervals on the camshaft 10, and a pickup coil arranged to be able to face each projection.
When the camshaft 10 rotates and each projection crosses the pickup coil, the coil generates an electromotive force.
The cam sensor 78 outputs the electromotive force as a pulse signal indicating the actual displacement angle VT.

A variable mechanism (hereinafter referred to as "VVT") 25 of the present invention provided on the timing pulley 12 changes the valve timing of the intake valve 8 by being hydraulically driven. That is, the valve timing of the intake valve 8 is advanced or delayed.

An oil pan 28 provided in the engine 1,
The oil pump 29 and the oil filter 30 constitute a lubricating device for lubricating each part of the engine 1. This lubrication device supplies hydraulic pressure to the VVT 25 to drive the same. The oil control valve (OCV) 55 is VVT2
5 can be adjusted. By operating the oil pump 29 in conjunction with the operation of the engine 1,
The lubricating oil sucked from the oil pan 28 is discharged by the oil pump 29. The discharged lubricating oil passes through the oil filter 30, is selectively pumped by the OCV 55, and is supplied to the VVT 25.

A vehicle speed sensor 79 provided in the automobile detects the speed (vehicle speed) SPD of the automobile and outputs a signal corresponding to the detected value. The warning lamp 69 provided in the driver's seat of the automobile operates to notify the driver or the like of the presence or absence of an abnormality related to the control of the ISCV 24.

FIG. 3 is a sectional view showing the structure of the VVT 25. The camshaft 10 is rotatably supported by the cylinder head 26. Pulley 12 on camshaft 10
Is mounted, and the pulley 12 is rotatable relative to the camshaft 10. The bottomed cylindrical cover 35 fixed to the pulley 12 has a flange 39 on its outer periphery.
And has a hole 40 in the center of the bottom. Multiple bolts 41
And 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 internal teeth 35a on its inner periphery.

The hollow bolt 46 and the pin 47 fix the inner cap 45 to the tip of the camshaft 10. The cap 45 has external teeth 45a on its outer periphery. Cover 35
And the ring gear 48 interposed between the cap 45 and
Both are relatively rotatable with respect to 35 and 45. The ring gear 48 has internal teeth 48a and external teeth 48b formed of helical splines on its inner circumference and outer circumference, respectively. The internal teeth 48a mesh with the external teeth 45a of the cap 45, and the external teeth 48b mesh with the internal teeth 35a of the cover 35.

Inside the cover 35, the ring gear 4
The first hydraulic chamber 49 and the second hydraulic chamber 50 formed on the left and right sides of FIG. 8 respectively communicate with oil passages 51 and 53 formed inside the camshaft 10.

The belt 14 is the pulley 1 of the camshaft 10.
2 and the pulley 12 of the crankshaft 1a are connected.
As the crankshaft 1a rotates, the belt 1
The pulley 12 rotates via 4 and the like. The rotation of the pulley 12 causes the cap 45 to pass through the ring gear 48.
And the camshaft 10 rotates integrally with the pulley 12.

Here, through the oil passage 51, the first hydraulic chamber 4
9 is supplied with hydraulic pressure, so that oil pressure is applied to the ring gear 48. Based on the hydraulic pressure, the ring gear 48 rotates while moving rightward in the drawing in the axial direction of the camshaft 10. At this time, the rotation phase changes relatively between the camshaft 10 and the pulley 12. In this case, the rotation phase of the camshaft 10 advances more than that of the pulley 12. As a result, the phase of the valve timing of the intake valve 8 leads the rotation phase of the crankshaft 1a.

In this case, as shown in FIG. 4 (b), the valve timing of the intake valve 8 is relatively advanced, and the valve overlap (positive valve overlap) 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 shown in FIG. 3 can be moved to the end position approaching the timing pulley 12. When the ring gear 48 reaches its end position, the valve timing of the intake valve 8 is most advanced and the valve overlap is largest.

On the other hand, when the ring gear 48 is moved to the right in the drawing, hydraulic pressure is applied to the second hydraulic chamber 50 through the oil passage 53, so that hydraulic pressure is applied to the ring gear 48. The ring gear 48 moves leftward in the axial direction of the camshaft 10 based on the hydraulic pressure.
At this time, the rotation phase between the camshaft 10 and the pulley 12 relatively changes in the opposite direction. in this case,
The rotation phase of the camshaft 10 lags behind that of the pulley 12. As a result, the valve timing of the intake valve 8 lags behind the rotational phase of the crankshaft 1a.

In this case, as shown in FIG. 4 (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, when the valve timing of the intake valve 8 is relatively delayed, the state in which the timing at which the intake valve 8 is opened and the timing at which the exhaust valve 9 is opened do not overlap each other, that is, the “negative valve overlap” occurs. can get. As described above, by controlling the hydraulic pressure supplied to the second hydraulic chamber 50, the ring gear 48 shown in FIG. 3 can be moved to the end position approaching the cover 35. When the ring gear 48 reaches the end position, the valve timing of the intake valve 8 is the latest, and the negative valve overlap is the largest.

In this embodiment, the supply of hydraulic pressure to the hydraulic chambers 49, 50 is controlled by the OCV 55. Here, by appropriately controlling the balance of the hydraulic pressure with respect to the first and second hydraulic chambers 49 and 50, the ring gear 48 moves leftward in the drawing or rightward in the drawing. Alternatively, the ring gear 48 is held at an intermediate position on the movement stroke. As a result, the VVT 25 is appropriately controlled and the valve timing of the intake valve 8 is set as shown in FIG.
It is possible to change continuously (steplessly) from the position shown in FIG. 4A to the position shown in FIG.

In this embodiment, the valve timing is controlled by controlling the OCV 55 based on the value of the required drive duty ratio DVT. At this time, in order to match the valve timing with the target value, the drive duty ratio DV is used as a parameter for controlling the OCV 55.
T is used.

Here, the electronic control unit (ECU) 80 is
The judging means and the first and second control means in the present invention are configured. The ECU 80 includes the various sensors 71 to 79 described above.
Input the signal output from. The ECU 80 receives each of the members 16, 22, 24, 55, 69 based on those input signals.
And so on.

As shown in the block diagram of FIG. 5, the ECU 8
0 is a central processing unit (CPU) 81, a read only memory (ROM) 82, a random access memory (RAM) 8
3 and a backup RAM 84. ECU80
Constitutes a logical operation circuit in which these units 81 to 84, an external input circuit 85 including an A / D converter, an external output circuit 85 and the like are connected by a bus 86. In this embodiment, the CPU 81 also has various counter functions including an auto-increment counter. The ROM 82 stores a predetermined control program and the like in advance. RAM 83 is a CPU
81 and the like are temporarily stored. Backup RAM
84 stores data stored in advance. The sensors 71 to 79 described above are connected to the external input circuit 84. The members 16, 22, 24, 55 and 69 described above are connected to the external output circuit 85. The ECU 80 is supplied with electric power from a power supply battery (not shown). CPU8
1 is each sensor or the like which is input via the external input circuit 84
The signals 1 to 79 are read as input values. Based on these input values, the CPU 81 controls the fuel injection amount, the ignition timing, the valve timing, and the idle speed (I
(SC) and each member 16, 22, 24, 55, 69 etc. are controlled in order to perform the control for fail safe.
The ROM 82 stores in advance programs and the like for executing these various controls.

Here, the fuel injection amount control means the engine 1
Is to control the fuel amount by controlling each injector 16 based on the target value calculated according to the operating state of the fuel cell. The ignition timing control is to control the ignition timing of each ignition plug 5 by controlling the igniter 22 based on a target value calculated according to the operating state of the engine 1. ISC means ISC in order to converge the engine speed NE to a predetermined value during idle operation.
It is to control the opening degree of V24. The valve timing control is a control of the OCV 55 based on the value of the drive duty ratio DVT calculated according to the operating state of the engine 1, thereby controlling the VVT 25 to control the valve timing of the intake valve 8, that is, valve overlap. Is to control. Control for fail-safe means IS
Excessive rotation speed N exceeding a predetermined value due to C abnormality
E is to reduce VVT25 by controlling it. IS
The abnormality in C includes, for example, that the ISCV 24 is fixed in an open state and does not operate.

Next, the contents of ISC processing will be described. FIG. 6 is a flowchart showing the "ISC routine". The ECU 80 periodically executes this routine at predetermined time intervals.

In step 100, the ECU 80 reads the values of the idle signal IDS, the engine speed NE and the vehicle speed SPD based on the signals from the sensors 72, 76 and 79, respectively.

At step 110, the ECU 80 determines whether or not the idle signal IDS is input. Throttle valve 1 when idle signal IDS is not input
Since ECU 7 is open and the engine 1 is in the acceleration operation state or the steady operation state, the ECU 80 once ends this routine. When the idle signal IDS is input, the throttle valve 17 is in the fully closed state.
80 shifts the processing to step 120. The ECU 80 that executes the processing of step 110 corresponds to a determination means for determining that the throttle valve 17 is in the fully closed state.

In step 120, the ECU 80 determines whether the vehicle speed SPD is "0". Vehicle speed SPD
If is not "0", the car is running,
The ECU 80 once ends this routine. Vehicle speed SPD
Is “0”, it is determined that the vehicle is stopped, the throttle valve 19 is fully closed, and the engine 1 is in the idle operation state.
Shifts the processing to step 130. In this embodiment, the ECU 80 that executes the process of step 120 corresponds to a determination unit that determines whether or not the vehicle is stopped. Further, the ECU 80 that executes the processing of steps 110 and 120 corresponds to a determination means for determining whether or not the engine 1 is in the idle operation state.

In step 130, the ECU 80 determines whether the engine speed NE exceeds the predetermined value NE1 and is excessive. That is, the ECU 80 executes ISC in order to converge the engine rotation speed NE to a predetermined target value TNE during idle operation. Here, if the engine speed NE exceeds the predetermined value NE1 and is excessive, it is considered that there is some abnormality in the control of the ISCV 24. One of them is that the ISCV 24 is fixed in an open state. Therefore, when the engine speed NE is equal to or lower than the predetermined value NE1, the ECU 80 shifts the processing to step 160. Engine speed N
If E is larger than the predetermined value NE1, the ISCV 24 is fixed in the open state and the ISC is abnormal.
U80 shifts the processing to step 140. In this embodiment, the ECU 80 that executes the processing of steps 110, 120, and 130 determines that the engine rotation speed NE, which is controlled based on the operation of the ISCV 24 during idle operation, has a predetermined value NE.
It corresponds to the judgment means of the present invention for judging whether or not the number exceeds 1 and is excessive.

The process proceeds from step 130 to step 16
At 0, the ECU 80 determines that the abnormality flag XFRS described later
Is determined to be “1”. This flag XFRS
Indicates whether or not an abnormality related to ISC has occurred.
When the flag XFRS is "0", the ISCV 24 operates normally and the ISCV 24 is regarded as normal, and the ECU 8
If 0, the process proceeds to step 170. This flag XF
When RS is "1", ISC is abnormal,
The ECU 80 once ends the subsequent processing.

The process proceeds from step 160 to step 17
At 0, the ECU 80 turns off the warning lamp 69.
In step 180, the ECU 80 calculates a value obtained by subtracting a predetermined target value TNE from the current engine rotation speed NE as a deviation value ΔNE. In this embodiment, the ECU 80 that executes the process of step 180 corresponds to a calculating unit that calculates the deviation value ΔNE of the engine rotation speed NE.

In step 190, the ECU 80 controls the opening degree of the ISCV 24 based on the deviation value ΔNE to converge the engine rotation speed NE to the target value TNE. In this embodiment, the ECU 80 that executes the processing of steps 180 and 190 sets the ISC so that the engine speed NE during idle operation reaches a predetermined target value TNE.
It corresponds to the first control means of the present invention for controlling V24. After the processing of step 134 is finished, the ECU 80
Ends the subsequent processing once.

The process proceeds from step 130 to step 14
At 0, since the ISC is abnormal, the ECU 80
Sets the abnormality flag XFRS to "1". Step 1
At 50, the ECU 80 stores the value of the flag XFRS in the backup RAM 84 as abnormal data.
The abnormal data stored in the backup RAM 84 can be read from the RAM 83 as needed. Further, the ECU 80 turns on the warning lamp 69 to notify the driver of the occurrence of the abnormality, and once ends this routine. In this embodiment, the ECU 80 that executes the processing of steps 140 and 150 corresponds to a recording unit for recording an ISC abnormality, and also corresponds to an ISC abnormality notifying unit.

Next, the processing contents of the valve timing control will be described. FIG. 7 is a flowchart showing the “valve timing control routine”. The ECU 80 periodically executes this routine at predetermined time intervals.

In step 200, the ECU 80 reads the values of the throttle opening TA, the intake pressure PM, the engine rotational speed NE and the actual displacement angle VT based on the signals from the sensors 72, 73, 76, 78 and 79.

At step 210, the ECU 80 reads the value of the abnormality flag XFRS set by the above-mentioned "ISC routine". In step 220, E
The CU 80 determines whether the abnormality flag XFRS is “1”. If the abnormality flag XFRS is “0”, I
Since the SCV 24 is normal, the ECU 80 shifts the processing to step 221. If the abnormality flag XFRS is "1", it means that the ISC is abnormal.
U80 transfers a process to step 230.

The process proceeds from step 220 to step 22.
In 1, the ECU 80 calculates the value of the target displacement angle VTT for controlling the VVT 25 based on the values of the various parameters TA, PM, NE read this time. ECU
80 calculates the target displacement angle VTT and the intake pressure P
This is performed by referring to function data set in advance using M and the engine speed NE as parameters. In this function data, when the engine 1 is idle,
The value of the target displacement angle VTT is set so that the valve overlap between the intake valve 8 and the exhaust valve 9 becomes zero. In addition, the function data is set so as to obtain the optimum value of the target displacement angle VTT according to the values of the respective parameters TA, PM, NE, that is, according to the operating state of the engine 1. In this embodiment, the ECU 80 that executes the process of step 221 corresponds to a calculating unit that calculates the target displacement angle VVT related to the valve timing according to the operating state of the engine 1.

In step 222, the ECU 80 calculates the value of the drive duty ratio DVT for controlling the OCV 55 according to the following formula. DVT = (VTT−VT) * KP Here, “KP” is a constant, and corresponds to a value for converting the difference between the target displacement angle VTT and the actual displacement angle VT into the value of the drive duty ratio DVT. In this embodiment, the ECU 80 that executes the process of step 222 corresponds to a conversion unit that converts a target value related to valve timing control into a command value for controlling the OCV 55.

The process proceeds from step 222 to step 28.
At 0, the ECU 80 duty-controls the OCV 55 based on the value of the drive duty ratio DVT calculated this time, and controls the VVT 25 to adjust the valve timing of the intake valve 8. As a result, when the ISC is normal, a valve overlap corresponding to the operating state of the engine 1 is obtained. In this embodiment, the ECU 80 that executes the process of step 280 determines that the VV based on the required command value.
It corresponds to a control means for controlling T25.

Step 23 shifts from step 220
At 0, the ECU 80 reads the intake pressure P read this time.
Based on the value of M, the intake air amount QA that reflects the magnitude of the load on the engine 1 is calculated. This intake air amount QA is experimentally determined in advance from the relationship with the intake pressure PM. In this embodiment, the ECU that executes the process of step 230
Reference numeral 80 corresponds to calculation means for calculating the magnitude of the load on the engine 1.

In step 240, the ECU 80 determines that the calculated intake air amount QA is a predetermined value α (for example, "20").
Liter / second ”) or less. When the intake air amount QA is larger than the predetermined value α, it is determined that the load on the engine 1 is large to some extent, and the ECU 80 once ends the subsequent processing. Here, when the load of the engine 1 is large, a relatively large output is required of the engine 1 when the vehicle is started, and the engine rotation speed NE decreases. Therefore, a feeling of acceleration more than expected when the vehicle starts, that is, a "jumping out feeling" does not occur. When the intake air amount QA is less than or equal to the predetermined value α, the ECU 80 determines that the load on the engine 1 is relatively small, and the ECU 80 shifts the processing to step 250. In this embodiment, the ECU 80 that executes the process of step 240 is the engine 1
Corresponds to a determination means for determining whether or not the load is smaller than a predetermined value.

In step 250, the ECU 80 determines that the value of the engine speed NE is a predetermined value NE2 (for example, "5").
It is larger than 50 rpm "). Here, the predetermined value NE2 is a value at which engine stall may occur when the engine rotation speed NE becomes lower than that value. The engine speed NE is a predetermined value N
If E2 or less, there is no risk of a "pop-out feeling" when the vehicle starts, so the ECU 80 once ends the subsequent processing. If the engine rotation speed NE is higher than the predetermined value NE2, there is a risk of a "jumping out" when the vehicle starts, so to prevent this, the ECU 8
0 shifts the processing to step 260. In this embodiment, the ECU 80 that executes the process of step 250
It corresponds to a determination means for determining whether or not the engine speed NE is a value that may cause engine stall when the SC is abnormal.

The process proceeds from step 250 to step 26.
At 0, the ECU 80 calculates the target displacement angle VTTF related to the valve timing when the ISC is abnormal, based on the calculated value of the intake air amount QA. The ECU 80
This calculation is performed using the intake air amount QA and the target displacement angle VTTF.
Is performed as a parameter by referring to preset function data. In this embodiment, when ISC is abnormal,
The ECU 80 adjusts V to reduce the engine speed NE.
Control the VT25. During the idling operation, by controlling the VVT 25 so that the above-mentioned negative valve overlap is obtained, the substantial air amount QA taken into the combustion chamber 4 is reduced. As a result, the engine rotation speed NE can be reduced. Therefore, in this embodiment, the value of the target displacement angle VTTF is set in the function data so that a negative valve overlap depending on the magnitude of the intake air amount QA is obtained. This function data is stored in the ROM 82 in advance. In this embodiment,
The ECU 80 that executes the process of step 260 determines that the ISC
It corresponds to a calculating means for calculating a target value used for valve timing control when an abnormality occurs.

In step 270, the ECU 80 calculates the drive duty ratio DVT based on the value of the target displacement angle VTTF calculated this time. The ECU 80 performs this calculation based on the target displacement angle VTTF and the drive duty ratio DVT.
Is performed as a parameter by referring to preset function data. This function data is stored in the ROM 82 in advance. In this embodiment, the ECU 80 that executes the process of step 270 corresponds to a conversion unit that converts a target value related to valve timing control into a command value for controlling the OCV 55.

The process proceeds from step 270 to step 28.
At 0, the ECU 80 duty-controls the OCV 55 based on the value of the drive duty ratio DVT calculated this time, and controls the VVT 25 to adjust the valve timing of the intake valve 8. As a result, when the ISC is abnormal, a negative valve overlap corresponding to the magnitude of the intake air amount QA is obtained, and the air amount Q taken into the combustion chamber 4 is increased.
Since A is reduced, the engine rotation speed NE is reduced. In this embodiment, the ECU 80 that executes the processing of steps 260 to 280 corresponds to the second control means of the present invention for controlling the VVT 25 so that the engine speed NE decreases when the ISC is abnormal. Step 28
After finishing the processing of 0, the ECU 80 once finishes the processing thereafter.

As described above, according to the configuration of this embodiment, since the throttle valve 17 is fully closed during the idle operation of the engine 1, the ECU 80 controls the ISCV 24 in order to control the engine speed NE.
The opening is adjusted to adjust the amount of air flowing through the bypass passage 23. As a result, the amount Q of air taken into the combustion chamber 4
A is adjusted and the engine speed NE is adjusted to a predetermined target value.

Here, due to some cause, ISCV24
Is fixed in the open state and the ISC becomes abnormal, the intake air amount QA taken into the combustion chamber 4 remains increased, and the engine speed NE excessively rises beyond a predetermined value. At this time, the ECU 80 determines the abnormality of the ISCV 24 from the value of the excessive engine rotation speed NE, and in order to reduce the engine rotation speed NE, the valve overlap, which is one of the opening / closing characteristics of the valves 8 and 9, is applied. adjust. That is, the ECU 80 calculates the intake air amount QA when the ISC is abnormal, based on the intake pressure PM, and calculates the value of the target displacement angle VTTF corresponding to the calculated value. Further, the ECU 80 calculates the value of the drive duty ratio DVT according to the value of the target displacement angle VTTF. ECU8
0 is OCV based on the value of this drive duty ratio DVT.
By controlling 55 and controlling VVT 25, the magnitude of the negative valve overlap is adjusted and the engine speed NE is reduced.

Therefore, in this embodiment, since the engine speed NE is lowered by adjusting the amount QA of air taken into the combustion chamber 4, unlike the case where the ignition timing is retarded, the combustion chamber 4 is controlled. The temperature of the exhaust gas discharged does not rise. Therefore, when the ISC is abnormal, the three-way catalyst 20 of the catalytic converter 19 is not subjected to a large heat load, and the heat deterioration thereof can be prevented in advance.

In this embodiment, since the variable range of the valve overlap of both valves 8 and 9 is mechanically set by the VVT 25, the adjustment range of the air amount QA taken into the combustion chamber 4 is set relatively large. It becomes possible to do. Therefore, when the ISC is abnormal, the engine speed NE can be reduced with a sufficient adjustment range. As a result, it is possible to suppress the "pop-out feeling" when the vehicle is started.

In this embodiment, when the ISC is abnormal, the warning lamp 69 provided in the driver's seat is turned on. Therefore,
The occurrence of an abnormality can be notified to the driver or the like, and the driver can promptly deal with the abnormality.

In this embodiment, when the ISC abnormality is detected, the value of the abnormality flag XFRS is stored in the backup RAM 84 as abnormal data. For this reason, when the vehicle is inspected etc.
By reading the abnormal data of AM84, the history regarding the abnormalities of ISC can be confirmed.

The present invention can be embodied in the following other embodiments. In the following another embodiment, the same operation and effect as the above embodiment can be obtained. (1) In the above embodiment, the engine rotation speed NE is made to converge to a predetermined value by controlling the opening degree of the ISCV 24 provided in the bypass passage 23 during the idling operation of the engine 1. On the other hand, the bypass passage 23
Alternatively, the ISCV 24 may be omitted and the engine speed NE may be controlled by driving the throttle valve 17 by a step motor during idle operation.

(2) In the above embodiment, the intake type adjusting means is constituted by the rotary type ISCV 24 and the bypass passage 23. A bimetal type ISCV may be provided in the bypass passage 23 instead of the rotary type ISCV 24. The bimetal type ISCV includes a heat coil, and the heating of the heat coil increases the opening of the ISCV and increases the amount of air taken into the bypass passage 23. (3) In the above embodiment, the valve timing of the intake valve 8 is changed as the valve opening / closing characteristic. On the other hand, only the valve timing of the exhaust valve 9 may be changed, or the valve timing of both the valves 8 and 9 may be changed. Further, the valve lift of the intake valve 8 or the exhaust valve 9 may be changed. With these configurations, the amount of air QA drawn into the combustion chamber 4 for changing the engine speed NE can be adjusted over a wide range.

(4) In the above embodiment, the valve operating mechanism is configured so that the rotational force of the crankshaft 1a is input to the camshaft 10 via the timing pulley 12 and the timing belt 14. . On the other hand, the timing pulley 12 may be replaced with a sprocket and the timing belt 14 may be replaced with a chain to form a valve mechanism.

(5) In the above embodiment, the VVT 25 provided with the ring gear 48 that meshes with the inner cap 45 and the cover 35 and meshes with the both 45, 35 is used. On the other hand, the present invention may be embodied as a rotary variable mechanism. That is, in the rotary variable mechanism, a rotor having a vane is fixed to a camshaft, and a housing rotatable relative to the camshaft and the rotor is provided on the outer periphery of the rotor. Hydraulic chambers are respectively formed on both sides of the vane in the direction of rotation of the rotor, and a lock pin is provided to lock the vane in its starting position or end position.

(6) In the above embodiment, the valve timing of the intake valve is continuously (stepless) by controlling the hydraulic pressure supplied to the first and second hydraulic chambers 49, 50.
It can be changed to On the other hand, the hydraulic pressure supplied to the first and second hydraulic chambers 49 and 50 may be controlled stepwise so that the valve timing of the intake valve can be changed stepwise.

(7) In the above embodiment, the intake valve 8 is retarded to obtain a negative valve overlap, so that the engine speed NE increased due to the abnormal ISC.
It was made to lower. On the other hand, the intake valve 8
By advancing the valve timing of No. 2 to maximize the valve overlap, the engine speed NE increased due to the ISC abnormality may be decreased.
In this case, in the exhaust stroke of the engine 1, the period during which the intake valve 8 is opened becomes longer, a small amount of burned gas is pushed out to the intake passage 7, and returns to the combustion chamber 4 again, so that the internal EGR amount becomes large. As a result, the output of the engine 1 is reduced, and the engine speed NE increased due to the failure of the ISCV 24 can be sufficiently reduced.

Alternatively, the engine speed NE may be reduced by selecting to maximize the valve overlap or to obtain the negative valve overlap depending on the increasing level of the engine speed NE. . That is,
The valve overlap is maximized when the engine speed NE is higher than the predetermined value NE3, and a negative valve overlap is obtained when the engine speed NE is lower than the engine speed NE.

Furthermore, it will be described below together with the effect that the above embodiment includes the following embodiments according to the technical idea described in the scope of claims. (A) In the control device for the internal combustion engine according to claim 1,
A control device for an internal combustion engine, wherein the opening / closing characteristic is a valve overlap adjusted by changing a valve timing of at least one of an intake valve and an exhaust valve.

According to this structure, the valve timing of at least one of the intake valve and the exhaust valve is advanced or retarded to adjust the valve overlap, thereby reducing the amount of air supplied to the intake passage. Or
The internal EGR in the combustion chamber increases. Thereby, the rotation speed of the internal combustion engine can be reduced.

(B) In the control device for an internal combustion engine according to the above item (a), a negative valve overlap is obtained by changing the valve timing.

According to this structure, the amount of air supplied to the intake passage is reduced. Thereby, the rotation speed of the internal combustion engine can be reduced. (C) The control device for an internal combustion engine according to the item (A), wherein the valve overlap is maximized by changing the valve timing.

According to this structure, the internal EGR of the combustion chamber increases. Thereby, the rotation speed of the internal combustion engine can be reduced.

[0076]

According to the first aspect of the invention, the rotational speed detected by the rotational speed detecting means controlled by the operation of the intake air adjusting means during the idling operation of the internal combustion engine exceeds the predetermined value and is excessive. Determination means for determining whether or not the rotation speed is excessive, and second control means for controlling the variable mechanism so as to reduce the rotation speed when the determination means determines that the rotation speed is excessive. Is equipped with.

Therefore, when the intake adjusting means or the first control means malfunctions for some reason and the rotational speed of the internal combustion engine exceeds a predetermined value and becomes excessive, the second control means operates the variable mechanism. By controlling and changing the opening / closing characteristics of at least one of the intake valve and the exhaust valve, the amount of air flowing into the combustion chamber is adjusted and the rotation speed of the internal combustion engine is reduced. Since the rotation speed of the internal combustion engine is reduced by adjusting the amount of air flowing into the combustion chamber, the temperature of the exhaust gas discharged from the combustion chamber to the exhaust passage does not rise unlike the case where the ignition timing is retarded. Absent. By setting the opening / closing characteristics of the intake / exhaust valve with the variable mechanism, it is possible to set the adjustment range of the air amount to be relatively large.

As a result, when the rotation speed of the internal combustion engine controlled by the ISC device becomes excessive, unlike the measure by the ignition timing control, the device is idle-operated with a sufficient adjustment range without increasing the exhaust temperature. This has the effect of reducing the rotational speed of the internal combustion engine during operation.

[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.

FIG. 3 is a cross-sectional view showing a VVT.

FIG. 4 is an explanatory diagram showing changes in valve overlap.

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

FIG. 6 is a flowchart showing an “ISC routine”.

FIG. 7 is a flowchart showing a “valve timing control routine”.

[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 ... Bypass passage, 24 ... Idle speed control valve (ISCV) (23) , 24 constitutes intake air adjusting means of the present invention.), 25 ... Variable mechanism (VVT), 76 ... Rotation speed sensor as rotation speed detecting means, 80 ... ECU
(80 constitutes a judging means and a first and a second controlling means).

Claims (1)

[Claims] 1. An intake passage and an exhaust passage communicating with a combustion chamber, an intake valve for selectively opening and closing between the combustion chamber and the intake passage, and a passage between the combustion chamber and the exhaust passage. An exhaust valve for selectively opening and closing, a variable mechanism for varying the opening and closing characteristics of at least one of the intake valve and the exhaust valve, and an intake adjusting means for adjusting the amount of air flowing through the intake passage. An internal combustion engine having:
A control device comprising first control means for controlling the intake air adjustment means so that the rotation speed of the internal combustion engine detected by the rotation speed detection means becomes a predetermined value. Occasionally, the rotation speed is controlled based on the operation of the intake air adjustment means, and the rotation speed detected by the rotation speed detection means exceeds the predetermined value to determine whether the rotation speed is excessive. A control device for an internal combustion engine, comprising: a second control means for controlling the variable mechanism so that the rotation speed is reduced when the determination means determines that the amount is excessive. .