JP2003041995A - Fail safe device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a positive and proper fail safe in an internal combustion engine controlling a suction air quantity by using an variable valve mechanism changing opening and closing characteristics of an intake valve. SOLUTION: Various sensors are diagnosed for anomalies (level 1 diagnosis), and engine power control and constant vehicular speed travel control are diagnosed for operational anomalies (level 2 diagnosis). When an anomaly is determined in the level 1 and 2 diagnoses, a process of limiting engine power by limiting a lift amount and cutting fuel is demanded as a level 1 fail safe process. A CPU of a control unit is diagnosed (level 3 diagnosis), and an ultimate level 2 fail safe process of selecting a fail safe demand from many on the basis of the level 1-3 diagnoses is carried out. In the level 2 fail safe process, a process of stopping the engine is carried out in an anomaly of the CPU, and a limp home operation is carried out in, for example, an undetectable state of the opening and closing characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fail-safe device for an internal combustion engine having a structure for controlling the intake air amount by changing the opening / closing characteristics of an intake valve.

[0002]

2. Description of the Related Art Conventionally, there is known a variable valve mechanism having a structure in which a valve lift amount and a valve operating angle of an intake valve / exhaust valve are continuously changed (JP 2001-012A).
262). The variable valve mechanism includes a control shaft arranged substantially parallel to the cam shaft, a control cam eccentrically fixed to the outer periphery of the control shaft, and a rocker arm pivotally supported by the control cam. A link arm / eccentric cam that swings and drives one end of the rocker arm according to the rotation of the cam shaft, and a swing cam that swings in cooperation with the other end of the rocker arm to open and close the intake / exhaust valve. And a DC servo motor that rotationally drives the control shaft.

Then, the DC servomotor is feedback-controlled so that the actual operating angle of the control shaft detected by the operating angle sensor matches the target operating angle corresponding to the required valve opening characteristic. .

[0004]

When the variable valve mechanism is used to control the intake air amount of the engine by changing the valve lift amount and valve operating angle (opening / closing characteristic) of the intake valve, the intake air amount is reduced. If an abnormality occurs in each sensor used to control the air amount, the intake air amount (output torque) control means will not operate normally,
It is also assumed that the fail-safe function for such an operation abnormality does not function normally due to the abnormality of the processing device CPU, and it is desired to provide a fail-safe that can deal with these in advance.

The present invention has been made in view of the above circumstances. In an internal combustion engine having a structure in which the intake air amount is controlled by changing the opening / closing characteristics of the intake valve, a fail-safe system that can appropriately cope with various abnormal states. The purpose is to provide a device.

[0006]

Therefore, according to the invention described in claim 1, the variable valve mechanism for changing the opening / closing characteristics of the intake valve, and the opening / closing characteristics of the intake valve by the variable valve mechanism are used to intake the engine. In an internal combustion engine provided with a processing device for controlling the amount of air, an operating state diagnostic means for diagnosing the operating state of the engine, a functional diagnostic means for performing a functional diagnostic of the processing device, and an operating state of the operating state diagnostic means When an abnormality is diagnosed, at least one of generating a warning and limiting engine output is performed, and when a functional abnormality of the processing device is diagnosed by the function diagnosing means, a failsafe means for stopping the engine, It is configured to include.

According to this structure, when an abnormal operating condition is diagnosed, at least one of issuing a warning and limiting the engine output is performed to continue the operation of the engine.
When a functional abnormality of the processing device (CPU) that controls the intake air amount of the engine occurs, the engine is stopped. Claim 2
In the invention described above, the operating state diagnosis means is configured to diagnose the detection function of the sensor relating to the control of the intake air amount by the processing device.

According to this structure, a state in which the engine operating state becomes abnormal due to erroneous control due to an abnormality in the sensor is diagnosed. In the invention according to claim 3, as the sensor,
At least one of an accelerator pedal sensor, an adjustment position sensor that detects the adjustment position of the opening / closing characteristics by the variable valve mechanism, and a brake switch is included.

According to this structure, the accelerator pedal sensor for detecting the depression amount (opening degree) of the accelerator pedal, the adjustment position sensor for detecting the adjustment position of the opening / closing characteristic by the variable valve mechanism, and the brake switch which is turned on when the brake is depressed. At least one of them is diagnosed for the detection function. According to a fourth aspect of the present invention, the operating state diagnosis means diagnoses whether or not the fail safe performed by the fail safe means is normally performed when the abnormality of the detection function of the sensor is diagnosed. did.

According to this structure, it is diagnosed whether or not the fail safe, which is supposed to be executed when the abnormality of the detection function of the sensor is diagnosed, is actually executed normally. According to a fifth aspect of the invention, the operating condition diagnosis means diagnoses the output torque adjusting means of the engine.

According to this structure, whether or not there is an abnormality in the output torque adjusting means such as the control of the intake air amount according to the accelerator pedal and the control of the intake air amount according to the set vehicle speed is diagnosed. According to a sixth aspect of the invention, the adjusting means is a constant vehicle speed traveling control means.

According to this structure, the intake air amount is controlled to diagnose whether or not there is any abnormality in the constant vehicle speed traveling control means for keeping the actual vehicle speed at the set vehicle speed. In the invention of claim 7, the variable valve mechanism includes a drive shaft that rotates in synchronization with a crankshaft, a drive cam fixed to the drive shaft, and a swing cam that swings to open and close an intake valve. A transmission mechanism having one end linked to the drive cam side and the other end linked to the swing cam side; a control shaft having a control cam for changing the posture of the transmission mechanism; and an actuator rotating the control shaft. And a mechanism for changing the lift characteristic of the intake valve by rotating the control shaft by the actuator.

According to this structure, the variable valve mechanism is
This is a mechanism in which the lift characteristic of the intake valve changes by rotating the control shaft by an actuator to change the operating angle. The lift characteristic of the intake valve changes according to the operating angle of the control shaft, and the intake air amount of the engine is changed. Changes.

[0014]

According to the first aspect of the present invention, a warning and / or an output is limited to an abnormal operating state to achieve failsafe while continuing engine operation, and the failsafe processing is performed. If the processing device cannot function properly, the engine can be stopped, and a reliable fail-safe operation can be achieved.

According to the second and third aspects of the present invention, when the sensor used for controlling the intake air amount is abnormal, there is an effect that failsafe can be achieved while continuing the engine operation. According to the invention described in claim 4, there is an effect that further fail-safe processing can be performed when fail-safe processing performed at the time of sensor abnormality is not normally performed, and reliable fail-safe can be achieved. .

According to the fifth aspect of the present invention, there is an effect that, when an abnormality occurs in the engine output torque adjusting function, the fail safe can be achieved while continuing the engine operation. According to the sixth aspect of the present invention, there is an effect that fail safe can be achieved while continuing the engine operation when the constant vehicle speed running control means is abnormal.

According to the seventh aspect of the invention, in the system for controlling the intake air amount by using the variable valve mechanism for changing the lift characteristic of the intake valve, the operation of the engine is continued as much as possible and the reliable fail-safe is achieved. The effect is that you can.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a vehicle internal combustion engine according to an embodiment, and an intake pipe 102 of the internal combustion engine 101.
The throttle motor 103a and throttle valve 1
An electronically controlled throttle 104 for opening and closing 03b is interposed, and the electronically controlled throttle 104 and the intake valve 10 are provided.
Air is sucked into the combustion chamber 106 via No. 5.

Combustion exhaust is discharged from the combustion chamber 106 to the exhaust valve 1.
It is discharged via 07, purified by the front catalyst 108 and the rear catalyst 109, and then discharged into the atmosphere. The exhaust valve 107 is opened and closed by a cam 111 supported by an exhaust side cam shaft 110 while maintaining a constant valve lift amount and a constant valve operating angle, while the intake valve 105 is controlled by a variable valve mechanism 112. Also, the valve operating angle (opening / closing characteristic) can be continuously changed.

The control unit 114 containing a microcomputer detects the accelerator pedal sensor APS116 so that the intake air amount corresponding to the accelerator opening can be obtained by the opening of the throttle valve 103b and the opening characteristic of the intake valve 105. The electronically controlled throttle 104 and the variable valve mechanism 112 are controlled according to the opening degree of the accelerator pedal.

In addition to the accelerator pedal sensor APS116, the control unit 114 includes an air flow meter 115 for detecting an intake air amount (mass flow rate), and a crank angle sensor 11 for extracting a rotation signal from a crank shaft.
7, detection signals from the throttle sensor 118 for detecting the opening of the throttle valve 103b, the brake switch 119, etc. are input.

2 to 4 show the variable valve mechanism 112.
2 shows the structure in detail. The variable valve mechanism shown in FIGS. 2 to 4 includes a pair of intake valves 105, 105, a hollow cam shaft 13 (driving shaft) rotatably supported by a cam bearing 14 of a cylinder head 11, and the cam shaft. Two eccentric cams 15 and 15 (driving cams), which are rotary cams pivotally supported by 13, a control shaft 16 rotatably supported by the same cam bearing 14 above the cam shaft 13, and the control shafts. 1
6, a pair of rocker arms 18, 18 swingably supported by a control cam 17 and the intake valves 105, 10
5, a pair of independent rocking cams 20 and 20 arranged via valve lifters 19 and 19 are provided at the upper end portion of 5.

The eccentric cams 15 and 15 and the rocker arm 1
8 and 18 are linked by link arms 25 and 25, and rocker arms 18 and 18 and swing cams 20 and 20 are linked by link members 26 and 26. The rocker arms 18, 18, the link arms 25, 25,
The link members 26, 26 form a transmission mechanism.

The eccentric cam 15 is, as shown in FIG.
A cam body 15a having a substantially ring shape and having a small diameter, and a flange portion 15b integrally provided on an outer end surface of the cam body 15a.
The cam shaft insertion hole 15c is formed so as to penetrate in the inner axial direction, and the shaft center X of the cam body 15a is eccentric from the shaft center Y of the cam shaft 13 by a predetermined amount. Further, the eccentric cam 15 is press-fitted and fixed to the cam shaft 13 on both outer sides which do not interfere with the valve lifter 19 through the cam shaft insertion holes 15c, and the outer peripheral surface 1 of the cam body 15a.
5d have the same cam profile.

As shown in FIG. 4, the rocker arm 18 is bent in a substantially crank shape, and a central base portion 18a is rotatably supported by the control cam 17. In addition, a pin hole 18d into which a pin 21 that is connected to the tip of the link arm 25 is press-fitted is formed through one end 18b protruding from the outer end of the base 18a, while an inner end of the base 18a is formed. Each of the link members 26 is attached to the other end portion 18c protrudingly provided in the portion.
Is formed with a pin hole 18e into which a pin 28 that is to be connected to one end portion 26a of FIG.

The control cam 17 has a cylindrical shape, is fixed to the outer periphery of the control shaft 16, and has a shaft center P1 position eccentric from the shaft center P2 of the control shaft 16 by α, as shown in FIG. As shown in FIGS. 2, 6 and 7, the swing cam 20 has a substantially horizontal U-shape, and the cam shaft 13 is fitted and inserted into a substantially annular base end portion 22 to be rotatably supported. Support hole 2
2a is formed so as to penetrate, and a pin hole 23a is formed so as to penetrate through the end portion 23 of the rocker arm 18 located on the other end portion 18c side.

On the lower surface of the swing cam 20, the base end portion 2 is provided.
A base circular surface 24a on the second side and a cam surface 24b extending in an arc shape from the base circular surface 24a to the end edge of the end portion 23 are formed,
The base circular surface 24a and the cam surface 24b come into contact with predetermined positions on the upper surface of each valve lifter 19 according to the swing position of the swing cam 20. That is, in view of the valve lift characteristics shown in FIG. 8, the predetermined angle range θ1 of the base circle surface 24a becomes the base circle section, and the predetermined angle range θ2 from the base circle section θ1 of the cam surface 24b becomes as shown in FIG. A so-called ramp section is set, and further, a predetermined angle range θ3 from the ramp section θ2 of the cam surface 24b is set to be a lift section.

The link arm 25 is provided with an annular base portion 25a and a projecting end 25b protruding at a predetermined position on the outer peripheral surface of the base portion 25a, and the eccentric cam 15 is provided at the center position of the base portion 25a. A fitting hole 25c for rotatably fitting is formed on the outer peripheral surface of the cam body 15a, while a pin hole 25d through which the pin 21 is rotatably inserted is formed at the protruding end 25b.

Further, the link member 26 is formed in a linear shape having a predetermined length, and the other end portions 26a and 26b of the circular shape are respectively the other end portion 18c of the rocker arm 18 and the end portion 23 of the swing cam 20. Each pin 2 press-fitted into the pin holes 18d, 23a
Pin insertion holes 26 through which the ends of 8, 29 are rotatably inserted
c and 26d are formed through. In addition, each pin 21,2
Snap rings 30, 3 for restricting axial movement of the link arm 25 and the link member 26 are provided at one end of
1, 32 are provided.

In the above structure, the axis P2 of the control shaft 16
6 and 7, the valve lift amount changes depending on the positional relationship between the control cam 17 and the axis P1 of the control cam 17, and by rotating the control shaft 16, the axis of the control cam 17 is changed. The position of the axis P2 of the control shaft 16 with respect to P1 is changed. The control shaft 16 has a configuration as shown in FIG.
1 is driven to rotate within a predetermined rotation angle range. By changing the operating angle of the control shaft 16 by the actuator 121, the valve lift amount and the valve operating angle of the intake valve 105 are continuously changed. It changes (see FIG. 9).

In FIG. 10, the DC servo motor 121
Is arranged such that its rotation axis is parallel to the control shaft 16, and a bevel gear 122 is axially supported at the tip of the rotation shaft. On the other hand, a pair of stays 123 are attached to the tip of the control shaft 16.
a, 123b are fixed and a pair of stays 123a, 12a
Around the axis parallel to the control shaft 16 connecting the tip of 3b,
The nut 124 is swingably supported.

A bevel gear 126, which is meshed with the bevel gear 122, is axially supported at the tip of the screw rod 125, which is meshed with the nut 124, and the screw rod 125 is rotated by the rotation of the DC servomotor 121. The position of the nut 124 that meshes with the threaded rod 125 is
The control shaft 16 is rotated by displacing it in the axial direction.

Here, the position of the nut 124 is set to the bevel gear 1
The direction closer to 26 is the direction in which the valve lift amount decreases, and conversely, the direction in which the position of the nut 124 is moved away from the bevel gear 126 is the direction in which the valve lift amount increases. As shown in FIG. 10, a potentiometer-type working angle sensor 127 (adjustment position sensor) for detecting the working angle of the control shaft 16 is provided at the tip of the control shaft 16 and is detected by the working angle sensor 127. The control unit 114 feedback-controls the DC servo motor 121 so that the actual operating angle that is set matches the target operating angle.

Specifically, in order to control the lift amount corresponding to the target intake air amount according to the opening degree of the accelerator pedal, the target operating angle corresponding to the target intake air amount is set, while A
When the vehicle is traveling at a constant vehicle speed based on an SCD (Auto Speed Control Device) operation signal, the target operating angle is set so that the actual vehicle speed is maintained at the set vehicle speed. The fail-safe in the internal combustion engine 101 having the above configuration will be described below.

FIG. 11 is a diagram showing the flow of diagnosis and fail-safe processing. In FIG. 11, in the level 1 diagnosis, input signals from various sensors and switches are diagnosed. As the various sensors and switches, the accelerator pedal sensor 116, the operating angle sensor 127, the brake switch 119, and the like are targets for diagnosis.

In the diagnosis of the input signals from the various sensors and switches, the accelerator pedal sensor 116 and the operating angle sensor 127 are detected for disconnection and short circuit.
When two sensors are provided, the presence / absence of an abnormality is diagnosed by determining whether the outputs are in agreement or inconsistency. Further, regarding the brake switch 119, the brake switch 11
The presence / absence of an abnormality is diagnosed by determining the matching / mismatching of 9 and the stop lamp switch.

However, the diagnosis of each sensor switch is not limited to the above-mentioned diagnosis method, and various known diagnosis methods can be used. On the other hand, in the level 2 diagnosis, the presence or absence of abnormality in various control operations is diagnosed.
Specifically, when the control operation of the engine output torque (intake air amount) according to the accelerator pedal, the constant vehicle speed traveling control operation, and the level 1 failsafe processing described later are being executed, the failsafe processing operation is abnormal. Diagnose the presence of.

Regarding the control operation of the engine output torque (intake air amount) according to the accelerator pedal and the constant vehicle speed traveling control operation, it is not possible to match the target lift amount (target intake air amount, set vehicle speed) (to the target). It is possible to judge that a state in which it does not change in the approaching direction) is abnormal. When it is diagnosed that the input signal from the sensor switch is abnormal in the level 1 diagnosis and / or when the control operation is abnormal in the level 2 diagnosis, the level 1
Perform the fail-safe processing of.

In the level 1 fail-safe processing,
A process for limiting the output torque of the engine and / or a warning of occurrence of an abnormality are performed. The output torque is limited by a process of limiting the lift amount of the intake valve, a process of temporarily stopping the fuel supply to the engine, an intake throttle by the electronically controlled throttle 104, and the like. Avoid producing higher output torque than required.

For example, when an abnormality occurs in the accelerator pedal sensor 116 and the working angle sensor 127 and the accelerator opening and the working angle of the control shaft 16 cannot be detected, the DC servo motor 121 controls the lift amount to decrease. The shaft 16 is rotationally driven to limit the lift amount to the minimum lift amount. Further, for example, when the sensor is normal but the lift amount of the intake valve is fixed and the output torque (intake air amount) cannot be controlled, fuel cut or intake throttle by the electronic control throttle 104 is performed. , Limit output torque.

While the output torque is being limited, at the same time, the warning lamp 120 or the like is used to warn the driver of the occurrence of an abnormality. However, when an abnormality occurs in the direction in which the output torque is not output, only a warning is issued. You can Further, in the diagnosis of the level 1 fail-safe processing in the level 2 diagnosis, whether or not the output torque of the engine is actually limited is judged from the detected values such as the lift amount, the intake air amount, the engine rotation speed and the like. .

The level 3 diagnosis is for diagnosing the operation of the CPU (central processing unit) built in the control unit 114, and includes ALU (arithmetic unit), ROM / RAM, program / running, etc., which constitute the CPU. Make a diagnosis. In the final level 2 fail-safe processing, based on the diagnosis result of any of the above levels 1 to 3, for example, a partial stop of the control function such as stop of the constant vehicle speed travel control, fuel cut and / or lift amount limitation Output torque limit, Limp home drive
g) From the forced stop of the engine, request the execution of fail-safe processing that is optimal for the abnormal condition at that time, and warn of the occurrence of the abnormal condition.

For example, when an abnormal operation of the CPU (Central Processing Unit) is diagnosed, a process of forcibly stopping the engine is performed, and with respect to the abnormal state of the brake switch 119,
The constant-speed traveling control is stopped, and if the working angle sensor 127 is abnormal, limp home traveling is executed. In the limp / home traveling, the intake valve lift amount is fixed to the maximum and the output torque control is performed by the electronic control throttle 104, or the lift amount of the bank in which the abnormality occurs in the V-type engine is fixed to the minimum. Then, the process of controlling the output torque by the lift amount control in the other normal bank is included.

The variable valve mechanism used for controlling the intake air amount is not limited to the mechanism shown in FIGS. 2 to 4, and other known variable valve mechanism may be used. Also,
Intake valve 105 without electronically controlled throttle 104
The configuration may be such that the intake air amount is controlled only by controlling the opening / closing characteristics of the.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the variable valve mechanism according to the embodiment of the present invention (A-A cross-sectional view of FIG. 3).

FIG. 3 is a side view of the variable valve mechanism.

FIG. 4 is a plan view of the variable valve mechanism.

FIG. 5 is a perspective view showing an eccentric cam used in the variable valve mechanism.

FIG. 6 is a cross-sectional view showing a function of the variable valve mechanism at a low lift (cross-sectional view taken along the line BB in FIG. 3).

FIG. 7 is a cross-sectional view (cross-sectional view taken along the line BB in FIG. 3) showing the action of the variable valve mechanism during high lift.

FIG. 8 is a valve lift characteristic diagram corresponding to a base end surface and a cam surface of a swing cam in the variable valve mechanism.

FIG. 9 is a characteristic diagram of valve timing and valve lift of the variable valve mechanism.

FIG. 10 is a perspective view showing a rotary drive mechanism of a control shaft in the variable valve mechanism.

FIG. 11 is a flowchart showing failsafe control in the internal combustion engine.

[Explanation of symbols]

13 ... Cam shaft 15 ... Eccentric cam 16 ... Control axis 17 ... Control cam 18 ... Rocker Arm 20 ... Swing cam 25 ... Link arm 101 ... Internal combustion engine 104 ... Electronically controlled throttle 105 ... intake valve 112 ... Variable valve mechanism 114 ... Control unit 115 ... Air flow meter 116 ... Accelerator pedal sensor 117 ... Crank angle sensor 118 ... Throttle sensor 119 ... Brake switch 120 ... Warning lamp 121 ... DC servo motor 127 ... Working angle sensor

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Claims (7)

[Claims] 1. An internal combustion engine comprising: a variable valve mechanism for changing the opening / closing characteristic of an intake valve; and a processing device for controlling the intake air amount of the engine by changing the opening / closing characteristic of the intake valve by the variable valve mechanism. In, an operating state diagnostic means for diagnosing the operating state of the engine, a functional diagnostic means for performing a functional diagnostic of the processing device, and a warning and an engine when an abnormal operating state is diagnosed by the operating state diagnostic means. A fail-safe device for an internal combustion engine, comprising: a fail-safe device that performs at least one of output limitation and stops the engine when the functional abnormality of the processing device is diagnosed by the function diagnostic device. 2. The fail-safe device for an internal combustion engine according to claim 1, wherein the operating condition diagnosing means diagnoses a detection function of a sensor relating to the control of the intake air amount by the processing device. 3. The sensor according to claim 2, wherein the sensor includes at least one of an accelerator pedal sensor, an adjustment position sensor for detecting an adjustment position of an opening / closing characteristic by the variable valve mechanism, and a brake switch. Fail-safe device for internal combustion engine. 4. The operating condition diagnosing means diagnoses whether or not the fail safe performed by the fail safe means is normally performed when an abnormality in the detection function of the sensor is diagnosed. A fail-safe device for an internal combustion engine according to claim 2 or 3. 5. The operating condition diagnosis means diagnoses an output torque adjusting means of the engine.
The fail-safe device for an internal combustion engine according to any one of items 1 to 4. 6. The fail safe device for an internal combustion engine according to claim 5, wherein the adjusting means is a constant vehicle speed traveling control means. 7. The variable valve mechanism comprises: a drive shaft that rotates in synchronization with a crankshaft; a drive cam fixed to the drive shaft; a swing cam that swings to open and close an intake valve; A transmission mechanism linked to the drive cam side and linked to the swing cam side at the other end, a control shaft having a control cam for changing the posture of the transmission mechanism, and an actuator rotating the control shaft. The internal combustion engine according to any one of claims 1 to 6, wherein the mechanism is a mechanism that changes the lift characteristic of the intake valve by rotating the control shaft by the actuator. Fail-safe device.