JPH10274065A - Valve characteristic control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an abnormal condition of oil such that oil viscosity is reduced without providing a sensor for detecting an abnormal condition of oil. SOLUTION: A crankshaft 15 of an engine 11 is connected to intake and exhaust cam shafts 25, 26 for opening/closing driving intake and exhaust valves 23, 24 by a timing belt 29. A valve timing variable mechanism (a VVT mechanism) 27 driven by oil pressure of oil is arranged on the intake cam shaft 25, and the opening/closing timing of the intake valve 23 is regulated by driving of the mechanism 27. In an electronic control unit 92, oil pressure of oil supplied to the VVT mechanism 27 is controlled so as to approach a real VVT advance rate to a target VVT advance rate calculated on the basis of an operating condition of the engine 11, and the mechanism 27 is driven. An abnormal condition of oil is detected on the basis of a ratio between a target integrating value obtained by integrating those advance rates respectively and real integrating value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve characteristic control device provided with a hydraulic valve characteristic variable mechanism for varying the opening and closing characteristics of a valve provided in an internal combustion engine, and more particularly, to driving the valve characteristic variable mechanism. The present invention relates to a device for detecting an abnormality of oil for performing the operation.

[0002]

2. Description of the Related Art Generally, an internal combustion engine such as an on-vehicle engine has a piston reciprocally movable in a cylinder block, and the piston is connected to a crankshaft (output shaft) of the internal combustion engine via a connecting rod. . The reciprocating movement of the piston is converted into rotation of the crankshaft by the connecting rod.

[0003] A cylinder head is mounted on the cylinder block, and a combustion chamber is provided between the cylinder head and the head of the piston. Further, the cylinder head is provided with an intake passage and an exhaust passage communicating with the combustion chamber, a fuel injection valve for injecting fuel into the combustion chamber, and an ignition plug for igniting a mixed gas in the combustion chamber. Have been. The cylinder head is provided with intake and exhaust camshafts that rotate with the rotation of the crankshaft, and intake and exhaust valves that are opened and closed by the rotation of the intake and exhaust camshafts. The intake valve is opened and closed to communicate and shut off the combustion chamber and the intake passage, and the exhaust valve is opened and closed to communicate and shut off the combustion chamber and the exhaust passage.

In the intake stroke of the internal combustion engine,
The combustion chamber and the intake passage are communicated by the intake valve, and the combustion chamber and the exhaust passage are shut off by the exhaust valve.
Air is sucked into the combustion chamber through the intake passage by the movement of the piston. At this time, fuel is injected from the fuel injection valve toward the combustion chamber, and a mixed gas comprising the air and the fuel is charged into the combustion chamber. Thereafter, in the compression stroke of the internal combustion engine, the combustion chamber and the intake passage are shut off by the intake valve, and the mixed gas in the combustion chamber is compressed by the movement of the piston. The compressed gas mixture is ignited by the spark plug and explodes, and the explosive force causes the piston to move in the opposite direction to move the internal combustion engine to the explosion stroke. Thereafter, in the exhaust stroke of the internal combustion engine, the combustion chamber and the exhaust passage are communicated by the exhaust valve, and the exhaust gas in the combustion chamber is discharged to the outside via the exhaust passage by the movement of the piston.

In the internal combustion engine having the above structure, the opening and closing characteristics such as the opening and closing timing of the intake valve and the exhaust valve and the lift amount are appropriately changed in order to improve the output and reduce the emission. . An apparatus for changing the valve characteristics as described above is disclosed in, for example, JP-A-7-2337.
A valve timing control device described in Japanese Patent Publication No. 43 is known.

The apparatus includes a driving member that moves so as to change the relative rotation phase of an intake camshaft with respect to a crankshaft, hydraulic chambers provided on both sides in the moving direction of the driving member, And a hydraulic control mechanism for supplying the pressure. Then, the oil is appropriately supplied to and discharged from the hydraulic chamber by the hydraulic control mechanism, and the drive member is moved by the oil pressure of the oil, whereby the relative rotational phase of the intake camshaft with respect to the crankshaft is changed. Thus, by changing the relative rotation phase of the intake camshaft with respect to the crankshaft, the opening / closing timing of the intake valve is changed.

The change of the opening / closing timing of the valve is performed, for example, when the opening / closing timing of the intake valve is delayed when the internal combustion engine is running at a low speed, or when the opening / closing timing of the intake valve is advanced when the internal combustion engine is running at a high speed. This is to stabilize the rotation by shortening the valve overlap when the internal combustion engine is running at a low speed, and to increase the intake efficiency of the engine by speeding up the opening of the intake valve when the internal combustion engine is running at a high speed.

[0008]

By the way, the oil supplied to the hydraulic chamber for moving the driving member has a certain viscosity in the sense that the oil pressure by the oil is efficiently transmitted to the driving member. Is preferred. However, as a matter of fact, the viscosity of the oil may be reduced due to deterioration with use. Also, even if fuel or the like is mixed in the oil, the viscosity is reduced. When the viscosity of the oil decreases, the oil pressure cannot be efficiently transmitted to the drive member, and as a result, the drive responsiveness of the valve timing control device decreases, and the drivability deteriorates. Become.

It is also conceivable to provide an appropriate sensor for detecting an oil abnormality due to a decrease in oil viscosity, and to judge the oil replacement timing based on the detection of the oil abnormality by the sensor. The labor and cost for providing the information cannot be ignored.

The present invention has been made in view of such circumstances, and has as its object to detect an oil abnormality such as a decrease in oil viscosity without providing a sensor or the like for detecting an oil abnormality. An object of the present invention is to provide a valve characteristic control device for an internal combustion engine that can be used.

[0011]

According to the first aspect of the present invention, there is provided a variable valve characteristic mechanism for changing the opening and closing characteristics of a valve in an internal combustion engine, and supply and discharge of oil to and from the variable valve characteristic mechanism. A driving means for hydraulically driving the mechanism, an operating state detecting means for detecting an operating state of the internal combustion engine, and a target value determining for determining a valve opening / closing characteristic target value based on a detection result of the operating state detecting means. Means, an actual characteristic detecting means for detecting an actual opening / closing characteristic of the valve, and a control means for controlling the driving means based on an opening / closing characteristic target value of the valve and the actual opening / closing characteristic,
Oil abnormality detecting means for detecting an abnormality of oil supplied to and discharged from the valve characteristic variable mechanism based on a characteristic transition of an actual opening / closing characteristic of the detected valve.

In this configuration, oil is supplied to and discharged from a valve characteristic variable mechanism based on a target value of the valve opening / closing characteristic and an actual opening / closing characteristic to control the hydraulic pressure of the mechanism. At this time, since the oil abnormality detecting means detects the oil abnormality based on the characteristic transition of the actual opening / closing characteristics of the valve, the oil abnormality can be detected without providing a sensor or the like for detecting the oil abnormality. become.

[0013] In the second aspect of the present invention, the oil abnormality detecting means includes a target integrated value obtained by integrating a valve opening / closing characteristic target value that changes based on an operating state of the internal combustion engine; An oil abnormality is detected based on an actual characteristic integrated value obtained by integrating actual opening / closing characteristics of the valve that changes based on a state.

In general, the valve opening / closing characteristic target value and the actual opening / closing characteristic frequently fluctuate based on the operating state of the internal combustion engine. However, in the same configuration, since the oil abnormality is detected based on the target integrated value and the actual characteristic integrated value obtained by integrating the open / close characteristic target value and the actual open / close characteristic, the open / close characteristic target value and the actual open / close characteristic are detected. Although the opening / closing characteristics fluctuate frequently, oil abnormality can be accurately detected.

According to a third aspect of the present invention, the oil abnormality detecting means measures an actual change speed of the opening / closing characteristic of the valve, and supplies / discharges the valve characteristic variable mechanism based on the measured change speed. Oil abnormality is detected.

According to this configuration, the characteristic change of the opening / closing characteristic can be known from the actual change speed of the opening / closing characteristic of the valve. Therefore, the oil abnormality can be accurately detected based on the change speed of the opening / closing characteristic. Become like

According to a fourth aspect of the present invention, the oil abnormality detecting means supplies the variable valve characteristic mechanism based on a time required for the actual opening / closing characteristic of the valve to reach a target value of the opening / closing characteristic of the valve. Abnormality of the drained oil is detected.

According to this configuration, since the characteristic change of the opening / closing characteristic can be known from the time until the actual opening / closing characteristic of the valve reaches the target value of the opening / closing characteristic, the oil abnormality is accurately detected based on the time. Will be able to do it.

According to a fifth aspect of the present invention, there is further provided a means for detecting or estimating the temperature of the oil supplied / discharged to the variable valve characteristic mechanism, and wherein the oil abnormality detecting means comprises a means for detecting the temperature of the oil detected or estimated. The oil abnormality is detected on condition that the temperature is within a predetermined temperature range.

In general, in the oil temperature region where the drive response of the variable valve characteristic mechanism tends to decrease due to the decrease in oil viscosity, the drive response of the mechanism varies greatly between the case where the oil is normal and the case where the viscosity decreases. Therefore, in the same configuration, by detecting the oil abnormality in the above oil temperature range, it becomes easy to detect the abnormality of the oil due to the decrease in the oil viscosity.

According to a sixth aspect of the present invention, there is further provided a means for obtaining the oil supply amount, wherein the oil abnormality detection means detects the oil abnormality on condition that the obtained oil supply amount is within a predetermined range. Shall be performed.

In general, in the oil supply amount region where the amount of oil supplied to the variable valve characteristic mechanism is small, the drive response of the mechanism greatly differs between the case where the oil is normal and the case where the viscosity is reduced. Therefore, in the same configuration, by detecting the oil abnormality in the oil supply amount region, it becomes easy to detect the abnormality of the oil due to the decrease in the oil viscosity.

According to the present invention, when the oil abnormality detecting means detects an abnormality in oil supplied to and discharged from the variable valve characteristic mechanism, fail-safe means for executing a fail-safe operation state of the internal combustion engine is provided. Further provision.

With this configuration, when an abnormality occurs in the oil supplied to and discharged from the variable valve characteristic mechanism, the fail-safe means performs fail-safe operation of the internal combustion engine. Can be maintained in the same state as when the oil is normal.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a valve timing control device according to the present invention is applied to an in-line four-cylinder vehicle engine will be described below with reference to FIGS.

As shown in FIG. 1, an engine 11 includes a cylinder block 1 provided with a reciprocating piston 12.
3, an oil pan 13 a provided below the cylinder block 13, and a cylinder head 14 provided above the cylinder block 13. A crankshaft 15 as an output shaft is provided at a lower portion of the engine 11.
Is rotatably supported, and the piston 12 is connected to the crankshaft 15 via a connecting rod 16.
The reciprocating movement of the piston 12 is caused by the connecting rod 1
The rotation of the crankshaft 15 is converted into rotation by the crankshaft 15.

At the end of the crankshaft 15, a crank side signal rotor 17 is attached. A plurality of projections 17 a are provided on the outer peripheral portion of the crank-side signal rotor 17 at equal angles around the axis of the crankshaft 15. A crank sensor 18 that detects a protrusion 17a of the rotor 17 and outputs a detection signal is provided on a side of the crank-side signal rotor 17. When the crankshaft 15 rotates and the projections 17a of the crank-side signal rotor 17 sequentially pass by the side of the crank sensor 18, a pulse-shaped signal corresponding to the passage of the projections 17a from the crank sensor 18 is obtained. A detection signal is output.

On the other hand, a combustion chamber 19 is provided above the piston 12.
Is provided. An intake passage 20 and an exhaust passage 21 provided in the cylinder head 14 are connected to the combustion chamber 19. The cylinder head 14 has an intake valve 2 that communicates and shuts off the intake passage 20 and the combustion chamber 19.
3. An exhaust valve 24 for communicating and shutting off the exhaust passage 21 and the combustion chamber 19, and rotatably supported intake and exhaust camshafts 25 and 26 are provided.

A variable valve timing mechanism (VVT) having a pulley 27a at one end of the intake camshaft 25
A mechanism 27 is provided, and a pulley 28 is attached to one end of the exhaust camshaft 26. Those pulleys 2
7a and 28 are connected to a pulley 15a attached to the crankshaft 15 via a timing belt 29. The rotation of the crankshaft 15 is transmitted to the intake and exhaust camshafts 25 and 26 via the timing belt 29, so that the intake and exhaust camshafts 25 and 26 rotate.

The intake camshaft 25 and the exhaust camshaft 26 are provided with an intake cam 31 that contacts the upper end of the intake valve 23 and an exhaust cam 32 that contacts the upper end of the exhaust valve 24, respectively. When the intake camshaft 25 and the exhaust camshaft 26 rotate, the intake cam 31 and the exhaust cam 32 open and close the intake valve 23 and the exhaust valve 24. By opening and closing the intake valve 23, the intake passage 20 and the combustion chamber 19 are communicated and shut off,
By opening and closing the exhaust valve 24, the exhaust passage 21 and the combustion chamber 19 are opened.
Is communicated and cut off.

At the other end of the intake and exhaust camshafts 25 and 26, the intake and exhaust signal rotors 3 are provided, respectively.
3, 34 are attached. Those rotors 33, 3
On the outer peripheral portion of No. 4, one projection 33a, 34a is provided, respectively. Further, on the sides of the intake-side and exhaust-side signal rotors 33, 34, there are provided intake and exhaust cam sensors 35, 36 for detecting the protrusions 33a, 34a of the rotors 33, 34 and outputting detection signals, respectively. . When the intake and exhaust camshafts 25 and 26 rotate, the protrusions 33a and 34a of the intake and exhaust signal rotors 33 and 34 pass by the intake and exhaust cam sensors 35 and 36 at predetermined intervals. In this state, the protrusions 3 from the intake and exhaust cam sensors 35 and 36 are used.
The detection signal is output at predetermined intervals corresponding to the passage of 3a and 33b.

Next, the structure of the fuel system, ignition system, intake / exhaust system and the like in the engine 11 will be described in detail with reference to FIG. As shown in the figure, a water temperature sensor 41 for detecting the temperature of cooling water in the engine 11 is provided in the cylinder block 13 of the engine 11. The cylinder head 14 is provided with an intake port 42 and an exhaust port 43 that communicate with the combustion chamber 19.
4 and the exhaust pipe 45 are connected. The inside of the intake pipe 44 and the inside of the intake port 42 are the intake passage 20, and the inside of the exhaust pipe 45 and the inside of the exhaust port 43 are the exhaust passage 21.

A throttle valve 46 is provided upstream of the intake pipe 44. The opening degree of the throttle valve 46 (throttle opening degree) is adjusted based on the amount of depression of an accelerator pedal 47 (accelerator opening degree) provided in the cabin of the automobile, and the opening degree of the throttle valve 46 is adjusted into the combustion chamber 19. The amount of air taken in is adjusted. And
A throttle sensor 46 is provided near the throttle valve 46.
a is provided. This throttle sensor 46a is
The throttle opening is detected and a detection signal corresponding to the opening is output. The accelerator pedal 47 is provided with an accelerator sensor 47a. This accelerator sensor 47a
Detects the accelerator opening and outputs a detection signal corresponding to the opening.

The intake passage 20 in the intake pipe 44 is connected to a bypass passage 49 which bypasses the throttle valve 46 and connects the upstream side and the downstream side of the throttle valve 46. The bypass passage 49 is provided with a linear solenoid type idle speed control valve (ISCV) 49a for adjusting the flow rate of air flowing through the passage 49. The opening of the ISCV 49a is adjusted based on the duty control of the voltage applied to the electromagnetic solenoid 49b, and the amount of air flowing through the bypass passage 49 is adjusted by adjusting the opening.

Further, the intake pipe 44 is provided with an intake pressure sensor 48 for detecting the pressure in the intake passage 20 located downstream of the throttle valve 46. The intake pressure sensor 48 outputs a detection signal corresponding to the detected pressure. A fuel injection valve 50 for injecting fuel into the combustion chamber 19 is provided at an end of the intake pipe 44 on the combustion chamber 19 side. The fuel injection valve 50 is configured such that the air in the intake passage 20
When the fuel is sucked into the combustion chamber 9, fuel is injected toward the combustion chamber 19 to form a mixed gas composed of fuel and air.

On the other hand, an ignition plug 51 is provided in the cylinder head 14. And the spark plug 51
As a result, the mixed gas filled in the combustion chamber 19 is ignited, whereby the mixed gas explodes and becomes exhaust gas, which is sent to the exhaust passage 21. The ignition plug 51
The engine 11 is connected to an igniter 53 through a distributor 52 provided in the engine 11. The igniter 53 applies a high voltage to the ignition plug 51 via the distributor 52, and the ignition timing of the ignition plug 51 is determined by the output timing of the high voltage output from the igniter 53.

In such an engine 11, in the intake stroke, the combustion chamber 19 and the intake passage 20 are communicated by the intake valve 23, and the combustion chamber 19 and the exhaust passage 21 are shut off by the exhaust valve 24. . At this time, a negative pressure is generated in the combustion chamber 19 due to the lowering of the piston 12, and air is sucked into the combustion chamber 19 through the intake passage 20 by the negative pressure. Also, from the fuel injection valve 50,
An amount of fuel corresponding to the amount of air sucked into the combustion chamber 19 is injected toward the combustion chamber 19, and as a result, the combustion chamber 1
9 is filled with a mixed gas consisting of air and fuel.

Thereafter, during the compression stroke of the engine 11, the combustion chamber 19 and the intake passage 20 are shut off by the intake valve 23 while the combustion chamber 19 and the exhaust passage 21 are kept shut off by the exhaust valve 24. As the piston 12 rises, the mixed gas in the combustion chamber 19 is compressed.

The gas mixture compressed in the combustion chamber 19 is ignited by the spark plug 51 and explodes, and the explosive force lowers the piston 12 to move the engine 11 to an explosion stroke. By this explosion stroke, the engine 11 obtains the driving force.

Thereafter, in the exhaust stroke of the engine 11, the combustion chamber 19 and the exhaust passage 24 are communicated by the exhaust valve 24 while the combustion chamber 19 and the intake passage 20 are kept shut off by the intake valve 23. Then, the mixed gas burned in the combustion chamber 19 is discharged to the outside as the exhaust gas through the exhaust passage 21 by the rise of the piston 12.

When the engine 11 is idling, the depression amount of the accelerator pedal 47 is "0" and the throttle valve 46 is fully closed, so that most of the air taken into the combustion chamber 19 is bypassed. It will pass through the passage 49. Therefore, when the engine 11 is in an idle state, the opening degree of the ISCV 49a is adjusted to adjust the amount of air taken into the combustion chamber 19, so that the engine 1
The idle speed of 1 is adjusted.

Next, the VVT mechanism 27 for adjusting the opening / closing timing of the intake valve 23 will be described in detail with reference to FIG. As shown in FIG.
The intake camshaft 25 to which the nozzle 7 is attached is supported by a bearing 14 a of the cylinder head 14. The VVT mechanism 27 includes a pulley 27a.
a includes a cylindrical portion 61 through which the intake camshaft 25 passes, a disk portion 62 protruding from the outer peripheral surface of the cylindrical portion 61, and a plurality of external teeth 63 provided on the outer peripheral surface of the disk portion 62. I have. The timing belt 29 is mounted on the external teeth 63 of the pulley 27a.

Further, a cover 64 provided on the pulley 27a so as to cover the end of the intake camshaft 25 is fixed by bolts 65 and pins 66. Cover 64
At a position corresponding to the end of the intake camshaft 25 on the inner peripheral surface of the, a plurality of internal teeth 67 are provided along the circumferential direction. On the other hand, an inner cap 70 is fixed to the tip of the intake camshaft 25 by a hollow bolt 68 and a pin 69. External teeth 71 are provided on the outer peripheral surface of the inner cap 70.
Are provided along the circumferential direction, and each of the external teeth 71 faces each of the internal teeth 67 of the cover 64. A ring gear 72 formed in a cylindrical shape is provided between each of the external teeth 71 and each of the internal teeth 67.
Are provided so as to be movable in the axial direction of the intake camshaft 25. Bevel teeth 73 meshing with the internal teeth 67 are provided on the outer peripheral surface of the ring gear 72.
Are provided with spur teeth 74 meshing with the external teeth 71. The spur teeth 74 extend linearly in the axial direction of the intake camshaft 25.

Accordingly, in such a VVT mechanism 27, when the crankshaft 15 is rotated by the driving of the engine 11, and the rotation is transmitted to the pulley 27a via the timing belt 29, the pulley 27a and the intake camshaft 25 are integrated. Rotate. This intake camshaft 2
As described above, the intake valve 23 (FIG. 1) is driven to open and close with the rotation of the fifth rotation.

When the ring gear 72 moves toward the pulley 27a (to the right in the drawing), the relative rotation phase between the pulley 27a and the intake camshaft 25 changes due to the action of the beveled teeth 73 on the ring gear 72, and the intake camshaft is changed. Numeral 25 is controlled, for example, to the side where the crankshaft 15 is retarded. That is, at this time, the intake valve 2
3, the opening / closing timing is delayed. Also, the ring gear 72
Is moved toward the cover 64 (to the left in the drawing), the pulley 27
a and the intake camshaft 25 change in the opposite direction, and the intake camshaft 25 is controlled to, for example, advance to the crankshaft 15. That is, at this time, the opening / closing timing of the intake valve 23 is advanced.

The intake valve 23 is normally connected to the engine 1
The opening / closing timing is delayed during low rotation of the
At the time of high rotation of 1, the opening / closing timing is advanced. This is to stabilize the rotation of the engine when the engine 11 is running at a low speed, and to improve the efficiency of sucking the mixed gas into the combustion chamber 19 when the engine 11 is running at a high speed.

Next, the structure of the VVT mechanism 27 for hydraulically controlling the movement of the ring gear 72 will be described. The ring gear 7 is located inside the cover 64.
2 divides into a retard side hydraulic chamber 75 and an advance side hydraulic chamber 76. Inside the intake camshaft 25, the retard control oil passage 77 and the advance control oil passage 7 connected to the retard hydraulic oil chamber 75 and the advance hydraulic oil chamber 76, respectively.
8 passes. The retard control oil passage 77 communicates with the retard hydraulic chamber 75 through the inside of the hollow bolt 68, and is connected to an oil control valve (OCV) 79 through the inside of the cylinder head 14. The advance angle control oil passage 78 communicates with the advance side hydraulic chamber 76 through the cylindrical portion 61 of the pulley 27a, and the cylinder head 14
And connected to OCV79.

A supply passage 80 and a discharge passage 81 are connected to the OCV 79. The supply passage 80 is connected to the oil pan 13a via an oil pump P driven by the rotation of the crankshaft 15, and the discharge passage 81 is directly connected to the oil pan 13a. Further, the oil pan 13a is provided with an oil temperature sensor 13b which detects the temperature of oil for driving the VVT mechanism 27 and outputs a detection signal corresponding to the detected oil temperature.

On the other hand, the OCV 79 has a casing 83, and the casing 83 has first and second supply / discharge ports 8.
4,85, first and second discharge ports 86,87,
A supply port 88 is provided. The first and second supply / discharge ports 84 and 85 are connected to the retard control oil passage 77.
And the advance angle control oil passage 78 are connected to each other. Further, the supply passage 88 is connected to the supply port 88,
The discharge passage 81 is connected to the first and second discharge ports 86 and 87. In the casing 83,
A spool 89 having four valve portions 89a and urged in opposite directions by a coil spring 90 and an electromagnetic solenoid 91 is provided.

Therefore, when the electromagnetic solenoid 91 is in the demagnetized state, the spool 89 is disposed on one end side (right side in FIG. 3) of the casing 83 by the urging force of the coil spring 90, and the first supply / discharge port 84 and the first Discharge port 86
And the second supply / discharge port 85 communicates with the supply port 88. In this state, the oil in the oil pan 13a is supplied to the advance hydraulic chamber 76 of the VVT mechanism 27 via the supply passage 80, the OCV 79, and the advance control oil passage 78. The oil in the retard hydraulic chamber 75 of the VVT mechanism 27 is returned to the oil pan 13a via the retard control oil passage 77, the OCV 79, and the discharge passage 81. As a result, the ring gear 72 is moved toward the retard hydraulic chamber 75, and the opening / closing timing of the intake valve 23 is advanced as described above.

On the other hand, when the electromagnetic solenoid 91 is excited, the spool 89 is disposed on the other end side (left side in FIG. 3) of the casing 83 against the urging force of the coil spring 90, and the second supply / discharge port 85 is the second discharge port 87
The first supply / discharge port 84 communicates with the supply port 88. In this state, the oil in the oil pan 13a is supplied to the retard hydraulic chamber 75 of the VVT mechanism 27 via the supply passage 80, the OCV 79, and the retard control oil passage 77. The oil in the advance side hydraulic chamber 76 of the VVT mechanism 27 is returned to the oil pan 13a via the advance control oil passage 78, the OCV 79, and the discharge passage 81. As a result, the ring gear 72 is moved toward the advance hydraulic pressure chamber 76, and the opening / closing timing of the intake valve 23 is delayed as described above.

Further, when the power supply to the electromagnetic solenoid 91 is controlled and the spool 89 is positioned in the middle of the casing 83, the first and second supply / discharge ports 84 and 85 are closed,
The movement of oil through the supply / discharge ports 84 and 85 is prohibited. In this state, the retard-side and advance-side hydraulic chambers 7
The oil is not supplied to and discharged from the hydraulic chambers 5, 76, and the oil is filled and held in the hydraulic chambers 75, 76, so that the ring gear 72 is fixed. As a result, the opening and closing timing of the intake valve 23 is maintained at the state when the ring gear 72 is fixed.

Next, an electrical configuration of the valve timing control device according to the present embodiment will be described with reference to FIG. The valve timing control device includes an electronic control unit (hereinafter, referred to as an “ECU”) for controlling an operation state of the engine 11 such as ignition timing control, fuel injection timing control, fuel injection amount control, idle speed control, and valve timing control. ) 92. This ECU 92 has a ROM 9
3. CPU 94, RAM 95 and backup RAM 9
6 and the like.

Here, the ROM 62 is a memory that stores various control programs and maps that are referred to when the various control programs are executed.
The arithmetic processing is executed based on various control programs and maps stored in M93. Also, the RAM 95 stores the CPU 9
4 is a memory for temporarily storing the calculation results in step 4, data input from each sensor, and the like.
Is a nonvolatile memory for storing data to be stored when the engine 11 is stopped. And ROM93, CPU
The RAM 94, the RAM 95, and the backup RAM 96 are connected to each other via a bus 97, and are also connected to an external input circuit 98 and an external output circuit 99.

The external input circuit 98 includes the oil temperature sensor 1
3b, crank sensor 18, intake cam sensor 35, exhaust cam sensor 36, water temperature sensor 41, throttle sensor 4
6a, an accelerator sensor 47a and an intake pressure sensor 48 are connected. The external output circuit 99 has an ISCV
49a, fuel injection valve 50, igniter 53, OCV 79
And a warning light 100 are connected. This warning light 100
Is provided on an instrument panel or the like of an automobile to notify occurrence of an oil abnormality.

The ECU 92 having the above-described configuration is used for the sensors 13b, 18, 35, 36, 41, 46a, 4
The OCV 79 controls the supply and discharge of oil to and from the VVT mechanism 27 based on the operating state of the engine 11 obtained from the detection signals 7a and 48, and drives the VVT mechanism 27. By driving the VVT mechanism 27, the relative rotation phase of the intake camshaft 25 with respect to the crankshaft 15 changes so that the opening / closing timing of the intake valve 23 becomes appropriate for the operating state of the engine 11. That is, the ECU
Reference numeral 92 denotes an engine 1 represented by a throttle opening and the like.
The target relative rotation angle of the intake camshaft 25 with respect to the crankshaft 15 is determined based on the load 1 and the rotation speed of the engine 11. Then, the ECU 92 sets VV so that the relative rotation angle of the intake camshaft 25 with respect to the crankshaft 15 approaches the target relative rotation angle.
The T mechanism 27 is driven.

For example, when the throttle opening, which is fully closed when the engine 11 is idling, increases as shown in FIG. 7B and changes in the manner shown by the solid line in FIG. 7B, the target relative rotation angle is determined. The target VVT advance angle θt (FIG. 7)
(A)) is calculated. This target VVT advance angle θt is
In response to the change in the throttle opening, the state changes in a manner indicated by a two-dot chain line in FIG. Then, the EC is adjusted so that the relative rotation angle of the intake camshaft 25 with respect to the crankshaft 15 approaches the target relative rotation angle.
When the drive of the VVT mechanism 27 is controlled by the U92, the actual VVT advance angle θreal changes in a manner shown by a solid line in FIG.

As is apparent from FIG. 7 (a), the change of the actual VVT advance angle θreal is based on the target VVT advance angle θt.
Is slightly delayed with respect to the transition. This is VVT
After the OCV 79 is controlled to drive the mechanism 27 and the supply of oil to the mechanism 27 is started, it takes time until the oil pressure of the oil acts on the ring gear 72 of the mechanism 27 and the gear 72 starts to move. That's why.

The drive response time of the VVT mechanism 27 changes due to the viscosity of the oil. If the viscosity of the oil is excessively low, the drive response of the VTT mechanism 27 will decrease. This is because if the oil viscosity is excessively low, the oil pressure of the oil cannot be transmitted to the ring gear 72 efficiently, and the change amount of the actual VVT advance amount θreal is smaller than the change amount of the target VVT advance amount θt. It is because it becomes.

Next, an oil abnormality detecting procedure according to this embodiment will be described with reference to FIGS. This figure 5
6 is a flowchart showing a processing routine for detecting oil abnormality such as a decrease in oil viscosity due to deterioration. The same processing routine is executed by the ECU 92 at, for example, a time interruption every one second.

In the same processing routine, the ECU 92 determines in step S101 the determination end flag F1 described later.
Is determined whether or not “0” is set in the RAM 95. Then, when “F1 = 0” is not satisfied, the process proceeds to step S114, and when F1 = "0”, the process proceeds to step S102.

The ECU 92 performs a process in step S102 based on a detection signal from the accelerator sensor 47a.
It is determined whether or not the operating state of the engine 11 is the first idle-off state after the idle-on state. That is, it is determined whether or not the throttle valve 46 has changed from the fully closed state to the opened state for the first time (whether or not the throttle opening is point A in FIG. 7B). If it is determined as YES in step S102, the process proceeds to step S103.
If the determination is NO, the process proceeds to step S104.

The ECU 92 sets the target integrated value Q (see FIG. 7A) obtained by integrating the target VVT advance amount θt to “0” as the process of step S103, and sets the actual VVT advance. The actual integrated value S (see FIG. 7A) obtained by integrating the angular amount θreal is set to “0”. Subsequently, in step S104, the ECU
92 is based on the detection signal from the oil temperature sensor 13b,
The oil temperature of the oil for driving the VT mechanism 27 is 80 ° C.
It is determined whether the temperature is within the range of 100 ° C.

Here, the oil temperature range (80 ° C. to 1
(00 ° C.), generally, the driving speed of the VVT mechanism 27 when the oil shown by the solid line in FIG. 8 is new and the driving speed of the VVT mechanism 27 when the oil viscosity shown by the broken line in FIG. different. Therefore, in the oil temperature range, it is easy to detect an oil abnormality based on a decrease in the drive response of the VVT mechanism 27.

Then, in step S104, NO
If it is determined that this is the case, the process proceeds to step S113, where "1" is set in the RAM 95 as the determination end flag F1, and this processing routine is temporarily terminated. In this case, the oil abnormality determination is restarted from the beginning. If YES is determined in step S104, the process proceeds to step S105.

After proceeding to step S105, the ECU 92
Determines whether or not a predetermined time T1 has elapsed from the time when the engine 11 first enters the idle-off state after the idle-on. This time T1 is set to a value (3 seconds in the present embodiment) necessary to obtain data (target integrated value Q, actual integrated value S) sufficient to detect oil abnormality. Then, if NO is determined in step S105, the process proceeds to step S106 (FIG. 6).

In step S106, the ECU 92 calculates the target V calculated this time from the previous target integrated value Qi-1.
By adding the VT advance amount θti, the current target integrated value Qi is set. Subsequently, the ECU 92 proceeds to step S1.
In step 07, the current actual integrated value Si is set by adding the actual VVT advance amount θreali obtained this time to the previous actual integrated value Si-1. After setting the target integrated value Qi and the actual integrated value Si in this way, the ECU 92 once ends this processing routine.

On the other hand, if it is determined as YES in step S105 (FIG. 5), the process proceeds to step S108. The ECU 92 performs the process of step S108 as follows:
It is determined whether or not the target integrated value Q is larger than a predetermined value a. The predetermined value a is used to check whether the VVT mechanism 27 has been sufficiently driven to accurately detect the oil abnormality, and is set to a value that can accurately detect the oil abnormality. I have.

If "Q>a" is not satisfied, the process proceeds to step S113, where "1" is set in the RAM 95 as the end determination flag F1, and this processing routine is once ended. In this case, the oil abnormality determination is restarted from the beginning. If “Q> a”, the process proceeds to step S109 (FIG. 6).

The ECU 92 determines whether or not the ratio (Q / S) between the actual integrated value S and the target integrated value Q is smaller than a predetermined value b as the process of step S109. The actual integrated value S
And the ratio of the target integrated value Q changes based on the oil viscosity. That is, when the oil viscosity decreases, VVT
Since the drive response of the mechanism 27 is reduced, the actual integrated value S becomes smaller than the target integrated value Q. Therefore, based on the ratio of the actual integrated value S to the target integrated value Q, it is possible to detect an oil abnormality such as a decrease in oil viscosity. Also, a predetermined value b
Is a threshold value for judging oil abnormality. When the predetermined value b increases, the criterion for judging oil abnormality becomes strict, and when the predetermined value b decreases, the criterion for judging oil abnormality becomes loose. Note that the predetermined value b in the present embodiment is set to a value that can accurately detect the oil abnormality without erroneously detecting the oil abnormality.

Then, in step S109,
When it is determined that “(Q / S) <b”, the process proceeds to step S110. After it is determined in step S110 that the oil is normal, the process proceeds to step S113. Also,
If it is determined in step S109 that “(Q / S) <b” is not satisfied, the process proceeds to step S111 and the ECU 9
2 turns on the warning light 100. Further, the following step S
At 112, the ECU 92 sets the oil abnormality flag F2
Is set in the RAM 95. ECU 92
Is set when the oil abnormality flag F2 is set to "1".
For example, fail-safe is executed by limiting the ignition timing advance amount during gentle acceleration.

In general, when the vehicle is accelerated due to an increase in the accelerator opening, the opening of the intake valve 23 is advanced, the ignition timing is advanced, and the efficiency of suction of air into the combustion chamber 19 is improved. An optimal ignition state for the mixed gas is obtained. However, when the drive speed of the VVT mechanism 27 is reduced due to an oil abnormality such as a decrease in oil viscosity, the opening of the intake valve 23 is not advanced as expected, and only the ignition timing is advanced from an appropriate timing. In this state, knocking occurs. For this reason, in the present embodiment, when an oil abnormality such as a decrease in oil viscosity occurs, the ignition timing advance amount is limited as fail-safe to prevent knocking.

After the normality determination in step 110 or after setting the oil abnormality flag F2 to "1" in step S112, the ECU 92 proceeds to step S11.
In the process of step 3, "1" is stored in the RAM as the determination end flag F1.
Set to 95. Then, after setting the determination end flag F1 to “1”, the ECU 92 once ends this processing.

When the determination end flag F1 is set to "1", it is determined in step S101 (FIG. 5) that "F1 = 0" is not satisfied, and the process proceeds to step S114. The ECU 92 determines whether or not a predetermined time T2 has elapsed since the determination end flag F1 was set to "1" as the process of step S114. The time T2 is used to determine the time interval at which the oil abnormality determination is performed. When the time T2 is set to be long, the time interval becomes long. When the time T2 is set to be long, the time T2 becomes long. The interval becomes shorter.

Then, in the above step S114,
If the determination is NO, this processing routine is temporarily terminated. On the other hand, if YES is determined, the process proceeds to step S
In 115, the ECU 92 sets “0” in the RAM 95 as the determination end flag F1, and then temporarily ends the processing routine.

According to the present embodiment for executing the above-described processing, the following effects can be obtained. -It is possible to accurately detect an oil abnormality such as a decrease in oil viscosity due to deterioration or the like without providing a sensor or the like for detecting an oil abnormality.

In general, the target VVT advance angle θt and the actual VVT advance angle θreal frequently fluctuate based on operating conditions such as the load and the number of revolutions of the engine 11. However, in this embodiment, oil abnormality is detected based on the ratio (Q / S) of the target integrated value Q and the actual integrated value S obtained by integrating the target VVT advance amount θt and the actual VVT advance amount θreal. Therefore, the oil abnormality can be accurately detected in spite of the frequent fluctuations of the advance angles θt and θreal.

In the present embodiment, the drive speed of the VVT mechanism 27 when the oil is new and the drive speed of the VVT mechanism 27 when the oil viscosity is low are greatly different in the oil temperature range (80 ° C. to 100 ° C.). C), it was determined whether the oil was abnormal. Therefore, it is possible to easily and accurately determine the oil abnormality based on the decrease in the drive response of the VVT mechanism 27.

When the oil abnormality is detected and the oil abnormality flag F2 is set to "1", the ECU 92 executes the fail-safe by limiting the advance amount of the ignition timing during acceleration of the vehicle. Therefore, when accelerating the vehicle in which the oil abnormality has occurred, it is possible to prevent the ignition timing from being excessively advanced and knocking from occurring when the opening of the intake valve 23 is not properly advanced. Become.

The present embodiment can be modified, for example, as follows. -Instead of the variable valve timing mechanism (VVT mechanism) 27 of the present embodiment, a vane type variable valve timing mechanism may be employed. In this case, the same effect as in the above embodiment can be obtained.

In this embodiment, a variable valve timing mechanism (V
The present invention was applied to the VT mechanism 27, but instead of this,
Alternatively, the present invention may be applied to a valve lift variable mechanism that makes the valve lift of the intake valve 23 variable. The variable valve lift mechanism may be a cam selection type or a cam moving type.

In the variable valve lift mechanism of the cam selection type, a plurality of cams having different cam profiles are provided on the intake camshaft. The mechanism is driven by the oil pressure of the oil supplied to the variable valve lift mechanism,
A cam for driving the intake valve is selected from the plurality of cams by the driving, and the valve lift of the valve is adjusted. In addition, in the cam moving type variable valve lift mechanism,
A three-dimensional cam whose cam profile changes continuously in the axial direction of the intake camshaft is provided, and the cam position of the three-dimensional cam is changed in the axial direction of the intake camshaft by oil pressure to adjust the valve lift of the intake valve.

In these cases, an oil abnormality is detected based on a cam for driving the intake valve or a change in the opening / closing characteristic of the cam when the cam position is switched. In the present embodiment, the VVT mechanism 27 that makes the opening / closing timing of the intake valve 23 variable is illustrated, but the exhaust valve 2
The present invention may be applied to a VVT mechanism that makes the opening / closing timing of the VVT 4 variable. Further, the above-mentioned variable valve lift mechanism may also make the valve lift of the exhaust valve variable.

In this embodiment, the target VVT advance angle θt
Oil abnormality is detected based on a ratio of a target integrated value Q obtained by integrating the actual VVT advance angle θreal to an actual integrated value S obtained by integrating the actual VVT advance amount θreal. It is not limited to this. For example, the drive speed of the VVT mechanism 27 is obtained based on detection signals from the crank sensor 18 and the intake and exhaust cam sensors 35 and 36,
Oil abnormality may be detected from the obtained drive speed of the VVT mechanism 27. In this case, since the characteristic transition of the opening and closing characteristics of the intake valve 23 can be known from the driving speed of the VVT mechanism 27, oil abnormality can be accurately detected based on the driving speed of the VVT mechanism 27.

Instead of detecting oil abnormality based on the ratio between the target integrated value Q and the actual integrated value S, the actual VV
Oil abnormality may be detected based on the time until the T advance angle θt becomes the same value as the target VVT advance angle θreal. In this case, the actual VVT advance amount θt is equal to the target VVT
Since the characteristic transition of the opening / closing characteristics of the intake valve 23 can be known from the time until the advance amount θreal becomes the same value, the oil abnormality can be accurately detected based on the time.

Instead of detecting an oil abnormality based on the ratio between the target integrated value Q and the actual integrated value S, an oil abnormality is detected based on, for example, a difference between the target integrated value Q and the actual integrated value S. Is also good.

The oil for driving the VVT mechanism 27 is supplied to the VVT mechanism 27 by the oil pump P driven by the rotation of the crankshaft 15 of the engine 11, so that the oil discharge of the oil pump P is reduced. When the engine 11 is running at a low speed, the drive responsiveness of the VVT mechanism 27 is likely to be reduced based on oil abnormality such as a decrease in oil viscosity. Based on such characteristics, the oil abnormality may be detected only at the time of low rotation of the engine 11 in which the oil supply amount to the VVT mechanism 27 is small. In this case, when the engine 11 is running at a low speed, the drive response of the VVT mechanism 27 is largely different between the case where the oil is normal and the case where the viscosity is reduced for the above-described reason. It will be easier.

Instead of performing the oil abnormality determination only when the engine 11 is running at a low speed as described above, the amount of oil supplied to the VVT mechanism 27 is calculated,
The oil abnormality determination may be performed when the oil supply amount is small based on the calculation result. In this case, as shown in FIG. 3, the oil pressure of the oil supplied to the VVT mechanism 27 via the OCV 79 is detected downstream of the oil pump P in the supply passage 80, and a detection signal corresponding to the detected oil pressure is detected. Is provided. Then, the supply amount of oil supplied to the VVT mechanism 27 is calculated from the detection signal from the oil pressure sensor 82 and the oil flow cross-sectional area of the supply passage 80. Also in this case, effects similar to the above effects can be obtained.

In this embodiment, the procedure for detecting an oil abnormality at the time of VVT advance has been described.
Oil abnormality detection may be performed at the time of the T delay. In the present embodiment, the advance amount of the ignition timing at the time of accelerating the vehicle is limited as a fail-safe.
The present invention is not limited to this. That is, the target value of the engine speed during idling may be increased as a fail-safe when the oil is abnormal.

In the present embodiment, the case where the predetermined time T1 of step S105 is 3 seconds has been exemplified, but the value of the predetermined time T1 may be changed as appropriate. In the present embodiment, the opening of the ISCV 49a is controlled to adjust the amount of intake air to the combustion chamber 19 during idling. Instead, an electronically controlled throttle valve is employed, and the opening of the valve is controlled. May be used to adjust the amount of intake air during idling.

When such an electronically controlled throttle valve is employed, the throttle valve is not connected to the accelerator pedal but to a step motor and is opened and closed by the motor. An accelerator sensor is provided in the vicinity of the accelerator pedal, and a detection signal according to the accelerator pedal depression amount by the driver, that is, an accelerator opening is provided from the sensor by the ECU.
It is output to an external input circuit 98 of the CPU 92. The opening of the throttle valve (throttle opening) is adjusted by controlling the step motor in accordance with the accelerator opening, the engine speed, and the like.

In this embodiment, when the temperature of the oil for driving the VVT mechanism 27 is between 80 ° C. and 100 ° C., it is determined whether or not the oil is abnormal. The oil temperature range to be used may be appropriately changed. Alternatively, the oil abnormality determination may be performed in the entire oil temperature range by omitting this.

The oil temperature sensor 13b and the like need not always be provided even when the oil temperature range for determining oil abnormality is determined. For example, the oil temperature may be estimated based on the cooling water temperature of the engine 11 detected by the water temperature sensor 41.

[0094]

According to the first aspect of the present invention, the oil abnormality detecting means detects an oil abnormality based on a change in the actual opening / closing characteristics of the valve. Therefore, the oil abnormality can be detected without providing a sensor or the like for detecting the oil abnormality.

According to the second aspect of the present invention, even if the target value and the actual opening / closing characteristic of the valve fluctuate frequently based on the operation state of the internal combustion engine, the target value and the actual characteristic value of the valve are not changed. An oil abnormality can be accurately detected based on the target integrated value and the actual characteristic integrated value obtained by the integration.

According to the third aspect of the present invention, the characteristic change of the opening / closing characteristic of the valve can be known from the actual change speed of the opening / closing characteristic, so that the oil abnormality can be accurately detected based on the change speed of the opening / closing characteristic. can do.

According to the fourth aspect of the invention, the characteristic transition of the opening / closing characteristic can be known from the time until the actual opening / closing characteristic of the valve reaches the target opening / closing characteristic.
An oil abnormality can be accurately detected based on the time.

According to the fifth aspect of the present invention, in the oil temperature range where the drive response of the variable valve characteristic mechanism tends to decrease due to the decrease in oil viscosity, the same mechanism is used when the oil is normal and when the viscosity decreases. Since the drive responsiveness greatly differs, by detecting an oil abnormality in the oil temperature range, it becomes easier to detect an oil abnormality due to a decrease in oil viscosity.

According to the sixth aspect of the present invention, in the oil supply amount region where the amount of oil supplied to the variable valve characteristic mechanism is small, the drive response of the same mechanism depends on whether the oil is normal or the viscosity has decreased. Since the characteristics differ greatly, by detecting an oil abnormality in the oil supply amount region,
Oil abnormality due to a decrease in oil viscosity is easily detected.

According to the seventh aspect of the invention, when an abnormality occurs in the oil supplied to and discharged from the variable valve characteristic mechanism, the fail-safe means performs the fail-safe operation state of the internal combustion engine. In some cases, the operating state of the engine can be maintained in the same state as when the oil is normal.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an entire engine to which a valve characteristic control device according to an embodiment is applied.

FIG. 2 is a sectional view showing an ignition system, a fuel system, and an intake / exhaust system of the engine.

FIG. 3 is a sectional view showing a configuration of a variable valve timing mechanism and an OCV.

FIG. 4 is a block diagram showing an electrical configuration of the valve timing control device.

FIG. 5 is a flowchart showing a procedure for detecting an oil abnormality.

FIG. 6 is a flowchart showing a procedure for detecting an oil abnormality.

FIG. 7 is a time chart showing a transition of a throttle opening and a transition between a target VVT advance amount and an actual VVT advance amount corresponding to the transition of the throttle opening.

FIG. 8 is a graph showing a relationship between an oil temperature and a driving speed of a VVT mechanism.

[Explanation of symbols]

11 ... Engine, 13b ... Oil temperature sensor, 18 ... Crank sensor, 23 ... Intake valve, 24 ... Exhaust valve, 27 ...
Variable valve timing mechanism (VVT mechanism), 35: intake cam sensor, 36: exhaust cam sensor, 41: water temperature sensor, 46a: throttle sensor, 47a: accelerator sensor, 48: intake pressure sensor, 79: OCV, 82: oil pressure sensor, 92 ... Electronic control unit (ECU), P ... Oil pump.

Claims (7)

[Claims] A variable valve characteristic mechanism for changing the opening and closing characteristics of a valve in the internal combustion engine; a drive means for supplying and discharging oil to the variable valve characteristic mechanism to hydraulically drive the mechanism; Operating state detecting means for detecting, target value determining means for determining an opening / closing characteristic target value of the valve based on a detection result of the operating state detecting means, actual characteristic detecting means for detecting an actual opening / closing characteristic of the valve, Control means for controlling the driving means based on the target value of the opening / closing characteristics of the valve and the actual opening / closing characteristics; and A valve abnormality control device for an internal combustion engine, comprising: oil abnormality detection means for detecting abnormality of oil to be performed. 2. The oil abnormality detecting means according to claim 1, wherein the target integrated value obtained by integrating the valve opening / closing characteristic target value that changes based on an operating state of the internal combustion engine, and a target integrated value that changes based on the operating state of the internal combustion engine. 2. The valve characteristic control device for an internal combustion engine according to claim 1, wherein an oil abnormality is detected based on an actual characteristic integrated value obtained by integrating actual valve opening / closing characteristics. 3. The oil abnormality detecting means measures an actual change speed of the opening and closing characteristics of the valve, and detects an abnormality of oil supplied to and discharged from the valve characteristic variable mechanism based on the measured change speed. 2. The valve characteristic control device for an internal combustion engine according to claim 1, wherein: 4. The oil abnormality detecting means detects an abnormality in oil supplied to and discharged from the variable valve characteristic mechanism based on a time until an actual opening / closing characteristic of the valve reaches a target value of the opening / closing characteristic of the valve. The valve characteristic control device for an internal combustion engine according to claim 1, wherein the valve characteristic is detected. 5. The valve characteristic control device for an internal combustion engine according to claim 1, further comprising: means for detecting or estimating a temperature of oil supplied to and discharged from the valve characteristic variable mechanism. A valve characteristic control device for an internal combustion engine, wherein the abnormality detecting means detects the oil abnormality on condition that the detected or estimated oil temperature is within a predetermined temperature range. 6. The valve characteristic control device for an internal combustion engine according to claim 1, further comprising: means for determining the supply amount of the oil, wherein the oil abnormality detection means determines that the determined oil supply amount is An oil characteristic control device for an internal combustion engine, wherein the oil abnormality is detected on condition that the oil abnormality is within a predetermined range. 7. The valve characteristic control device for an internal combustion engine according to claim 1, wherein said oil abnormality detecting means detects an abnormality in oil supplied to and discharged from said variable valve characteristic mechanism. A valve characteristic control device for an internal combustion engine, further comprising fail-safe means for performing a fail-safe operation state of the engine.