JP4440566B2 - Control of an internal combustion engine having a variable valve mechanism - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control technique for an internal combustion engine having a variable valve mechanism.
[0002]
[Prior art]
A variable valve mechanism of an internal combustion engine is used to change the opening / closing characteristics of an intake valve (hereinafter referred to as valve opening / closing characteristics). The variable valve mechanism is usually provided with a sensor (referred to as a “working angle sensor”) for detecting a working angle (crank angle during the valve opening period). If an abnormality occurs in the working angle sensor, the working angle becomes unclear, which causes a disadvantage that a desired operation cannot be performed.
[0003]
As a technique for detecting the occurrence of an abnormality in the working angle sensor, for example, a technique described in Patent Document 1 below is known.
[0004]
[Patent Document 1]
JP 2000-28291 A
[Patent Document 2]
Japanese Patent Laid-Open No. 11-236849
[Patent Document 3]
Japanese Patent Laid-Open No. 10-121998
[Patent Document 4]
Japanese Patent No. 2880638
[Patent Document 5]
JP 2000-97096 A
[0005]
[Problems to be solved by the invention]
However, in the past, the main attention has been directed to detecting the occurrence of an abnormality in the working angle sensor, and there is not much about how the internal combustion engine can be operated after the abnormality is detected. It was not considered.
[0006]
The present invention has been made to solve the above-described problems, and an object thereof is to provide a technique for smoothly operating an internal combustion engine when an abnormality is detected in a working angle sensor.
[0007]
[Means for solving the problems and their functions and effects]
In order to solve the above problems, a control device for an internal combustion engine according to the present invention provides:
A throttle valve,
A variable valve mechanism for adjusting a valve opening characteristic of an intake valve provided in a combustion chamber of the internal combustion engine;
A target value determining unit that determines an operation target value of the throttle valve and the variable valve mechanism in response to a load request to the internal combustion engine;
An intake air amount adjustment mechanism control unit that adjusts the intake air amount to the combustion chamber by controlling the operation of the throttle valve and the variable valve mechanism based on the operation target value;
A working angle sensor provided in the variable valve mechanism for detecting a magnitude of a working angle of the intake valve;
An abnormality diagnosing unit for diagnosing an abnormality of the working angle sensor;
With
The intake air amount adjustment mechanism control unit, when the abnormality diagnosis unit detects an abnormality of the working angle sensor,
(I) The working angle along a predetermined trajectory Over time A drive signal for changing is output to the variable valve mechanism,
(Ii) of the drive signal time Of the actual working angle according to the change time Estimating the change,
(Iii) of the estimated working angle time The opening degree of the throttle valve is adjusted based on the change.
[0008]
According to this configuration, even when an abnormality is detected in the working angle sensor, the working angle is changed along a predetermined locus, and the throttle opening is adjusted based on the change in the working angle. Even after an abnormality is detected in the angle sensor, the internal combustion engine can be operated relatively smoothly.
[0009]
The estimated operating angle may be set to a value that gives an intake air amount that is larger than the actual operating angle.
[0010]
According to this configuration, it is possible to prevent the output of the internal combustion engine from becoming excessive due to an excessive intake amount.
[0011]
When the abnormality diagnosis unit detects that the working angle sensor has returned from the abnormal state to the normal state, the actual working angle indicated by the working angle sensor is the target value determining unit. It is also possible to control the operation of the variable valve mechanism so as to approach the target value of the operating angle determined by.
[0012]
According to this configuration, since the operating angle can be prevented from changing suddenly, it is possible to prevent sudden increase or stop of the output of the internal combustion engine.
[0013]
When the abnormality diagnosis unit detects that the operating angle sensor has returned from an abnormal state to a normal state, the intake air amount adjustment mechanism control unit adjusts the operating angle from the actual operating angle to the target operating angle value. An increase rate limit and a decrease rate limit may be set for the change.
[0014]
According to this configuration, it is possible to reliably prevent the operating angle from changing suddenly.
[0015]
It should be noted that the present invention can be realized in various modes, for example, realizing a control device or control method for an internal combustion engine, an engine or vehicle equipped with the control device, and a function of the control device or control method. The present invention can be realized in the form of a computer program for recording, a recording medium storing the computer program, and the like.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in the following order based on examples.
A. Device configuration:
B. First embodiment:
C. Second embodiment:
D. Third embodiment:
E. Variations:
[0017]
A. Device configuration:
FIG. 1 shows the configuration of a control apparatus as an embodiment of the present invention. This control device is configured as a device that controls a gasoline engine 100 mounted on a vehicle. Engine 100 includes an intake pipe 110 for supplying air (fresh air) to the combustion chamber, and an exhaust pipe 120 for exhausting the exhaust from the combustion chamber to the outside. The combustion chamber is provided with a fuel injection valve 101 for injecting fuel into the combustion chamber, an ignition plug 102 for igniting an air-fuel mixture in the combustion chamber, an intake valve 112, and an exhaust valve 122.
[0018]
The intake pipe 110 is provided with an air flow meter 130 (flow rate sensor) for measuring the intake flow rate, an electromagnetic throttle valve 132 for adjusting the intake flow rate, and a surge tank 134 in order from the upstream side. The surge tank 134 is provided with a temperature sensor 136 (intake air temperature sensor) and a pressure sensor 138 (intake air pressure sensor). The intake path on the downstream side of the surge tank 134 is divided into a number of branch pipes connected to a plurality of combustion chambers, but is simplified in FIG. 1 and only one branch pipe is drawn. The exhaust pipe 120 is provided with an air-fuel ratio sensor 126 and a catalyst 128 for removing harmful components in the exhaust. The air flow meter 130 and the pressure sensor 138 can be provided at other positions. In this embodiment, the fuel is directly injected into the combustion chamber, but the fuel may be injected into the intake pipe 110.
[0019]
The intake operation and the exhaust operation of the engine 100 are switched depending on whether the intake valve 112 and the exhaust valve 122 are open or closed. The intake valve 112 and the exhaust valve 122 are provided with variable valve mechanisms 200 and 300 for adjusting the opening and closing timing, respectively. These variable valve mechanisms 200 and 300 can change the size of the valve opening period (so-called operating angle) and the position of the valve opening period (also referred to as “phase of the valve opening period”). A specific example of the variable valve mechanism will be described later.
[0020]
The operation of the engine 100 is controlled by the control unit 10. The control unit 10 is configured as a microcomputer including a CPU, RAM, and ROM therein. The control unit 10 is supplied with signals from various sensors. In addition to the sensors 136, 138, and 126 described above, these sensors include a knock sensor 104, a water temperature sensor 106 that detects engine water temperature, a rotation speed sensor 108 that detects engine rotation speed, an accelerator sensor 109, It is included.
[0021]
The control unit 10 realizes the functions of an operation target value determination unit 12, an intake air amount calculation unit 14, an abnormality diagnosis unit 16, and an intake air amount adjustment mechanism control unit 18. The operation target value determination unit 12 mainly determines the target value of the intake air amount adjustment mechanism (the electromagnetic throttle valve 132 and the intake valve 112) according to the output from the accelerator sensor 109 (accelerator depression amount). The intake air amount calculation unit 14 outputs the output of a sensor for calculating the intake air amount (such as the air flow meter 130 and the pressure sensor 138) and the operation target value (command value) of the intake air amount adjustment mechanism determined by the operation target value determination unit 12. The intake air amount is calculated according to. The abnormality diagnosis unit 16 determines whether an abnormality has occurred in the working angle sensor according to an output signal from a working angle sensor (described later) provided in the variable valve mechanisms 200 and 300. The intake air amount adjustment mechanism control unit 18 outputs a command value to each intake air amount adjustment mechanism at an appropriate timing according to the operation target value of the intake air amount adjustment mechanism determined by the operation target value determination unit 12. Further, when an abnormality occurs in the operating angle sensor, a command value is output to each intake air amount adjustment mechanism in a sensor abnormal operation mode described later. The functions of these units 12, 14, 16 and 18 are realized by a computer program stored in a memory (not shown) of the control unit 10.
[0022]
FIG. 2 is an explanatory diagram showing an example of the structure of the variable valve mechanism 200. The variable valve mechanism 200 includes a cam mechanism 210 for setting the operating angle of the intake valve 112, an actuator 220 for moving the cam mechanism 210 in the axial direction, and an attachment 215 for connecting the cam mechanism 210 and the actuator 220. It has.
[0023]
The actuator 220 includes a movable shaft 223, an electric motor 221 for moving the movable shaft 223 left and right, a sensor 222 for measuring the rotation angle of the electric motor 221, and an electric motor drive unit 224 for driving the electric motor 221. I have. The electric motor drive unit 224 drives the electric motor 221 in accordance with the operating angle control signal Sag supplied from the intake air amount adjustment mechanism control unit 18 (FIG. 1) to determine the left and right positions of the cam mechanism 210, and thereby the intake valve The working angle of 112 is adjusted.
[0024]
The cam mechanism 210 includes a cam 211 and a cam shaft 212. The shape of the cam 211 is set so that the operating angle can be changed according to the position in the left-right direction in the drawing. When the movable shaft 223 of the actuator 220 moves to the left and right, the cam shaft 212 moves to the left and right within a predetermined movable range via the attachment 215. When the camshaft 212 is at the left end of the movable range, the operating angle of the intake valve 112 is maximized. On the other hand, when the camshaft 212 is at the right end of the movable range, the operating angle of the intake valve 112 is minimum. A cam 211 indicated by a two-dot chain line in FIG. 2 shows a state when the cam 211 is at the minimum operating angle position.
[0025]
The sensor 222 is a value indicating the rotation angle of the electric motor 221, and this rotation angle is associated with the position of the movable shaft 223 in the left-right direction. Further, the position of the movable shaft 223 is associated with the operating angle of the intake valve 112. That is, the output of the sensor 222 can be used as a value indicating the working angle, and the sensor 222 functions as a working angle sensor. Other types of working angle sensors can be used.
[0026]
The cam mechanism 210 is driven to rotate by a timing pulley (not shown) provided at the other end of the cam shaft 212. The attachment 215 is configured so that the rotation of the cam mechanism 210 is not transmitted to the movable shaft 223 of the actuator 220. The timing belt wound around the timing pulley is connected to a crankshaft (not shown). When the cam 211 rotates, a force is applied to the valve lifter 152 via the cam follower 156 that swings according to the direction of the contact surface of the cam 211. The upper end of the shaft of the intake valve 112 is fixed to the valve lifter 152.
[0027]
A valve spring 151 is accommodated in the valve lifter 152, and the valve lifter 152 is biased by the spring 151 in the valve opening direction of the intake valve 112 (upward in the drawing). On the other hand, the cam 211 pushes the valve lifter 152 in a direction to close the intake valve 112 according to the rotation of the cam shaft 212. The amount of movement of the intake valve 112 at this time is the valve lift amount.
[0028]
FIG. 3 is an explanatory diagram showing the relationship between the crank angle and the valve lift amount. As can be seen from FIG. 3, the valve lift amount of the intake valve 112 has a variable profile. The profile of the intake valve 112 changes continuously according to the position of the cam shaft 212 (FIG. 2) in the axial direction. The minimum lift amount corresponds to the minimum operating angle, and the maximum lift amount corresponds to the maximum operating angle. The minimum working angle is, for example, about 100 ° CA (indicating that CA is a crank angle), and the minimum working angle is, for example, about 260 ° CA. Thus, the maximum working angle is often set to 180 ° CA or more.
[0029]
FIG. 4A shows the relationship between the duty of the working angle control signal Sag of the intake valve 112 and the working angle. Here, “duty” means the ratio of the on-level period in the rectangular wave signal. When the duty DT is zero, the operating angle is the minimum value θmin, and when the duty DT is the maximum value DTmax within a predetermined allowable range, the operating angle is the maximum value θmax. FIG. 4B shows the relationship between the operating angle and the intake air amount. Here, it is assumed that the opening degree of the electromagnetic throttle valve 132 is constant. As the operating angle increases from the minimum value θmin, the intake air amount also increases. However, after the intake amount reaches the maximum value at a specific operating angle θpeak, the intake amount decreases as the operating angle increases. This is because, as described above, the maximum value θmax of the operating angle is set to a value of 180 ° CA or more.
[0030]
FIG. 5 shows the output characteristics of the working angle sensor 222. The working angle sensor 222 constitutes a double system including two sensor elements. Two output voltages VS1 and VS2 are output from the two sensor elements. These output voltages VS1 and VS2 have an offset ΔVS, and can be changed within the range from the minimum values VS1min and VS2min to the maximum values VS1max and VS2max, respectively. Note that the second output voltage VS2 has a flat portion cut by the upper limit value VS2max. Therefore, when the working angle sensor 222 is normal, the working angle is determined according to the first output voltage VS1.
[0031]
The abnormality diagnosis unit 16 (FIG. 1) diagnoses an abnormality of the working angle sensor 222 using, for example, the following determination conditions.
(1) Disconnection / Short-circuit judgment conditions:
When at least one of the two output voltages VS1 and VS2 is outside the normal range (VS1min to VS1max, VS2min to VS2max), a disconnection or short-circuit state (hereinafter referred to as "disconnection / short-circuit state") judge.
[0032]
(2) Judgment condition for sensor range out-of-range condition:
When the difference ΔVS between the two output voltages VS1 and VS2 is outside the predetermined allowable range (below the predetermined value or above the predetermined value), it is determined that the sensor range is out of range.
[0033]
When the disconnection / short circuit state or the sensor range outage state continues for the first predetermined time (for example, 12 ms), the abnormality diagnosis unit 16 determines that the abnormality is a temporary abnormality and sets a temporary abnormality flag. Further, when the temporary abnormality continues for a second predetermined time (for example, 400 ms), it is determined that this abnormality is present, and this abnormality flag is set. Even when the temporary abnormality flag is set, if the two output voltages VS1 and VS2 are both within the normal range for a predetermined time (for example, 50 ms), the temporary abnormality flag is canceled. Thus, it is determined that the operating angle sensor 222 has returned to normal.
[0034]
The intake air amount adjustment mechanism control unit 18 (FIG. 1) adjusts both the opening degree of the electromagnetic throttle valve 132 and the operating angle of the intake valve 112 to achieve an intake air amount suitable for the required load of the engine 100. Hereinafter, the adjustment of the intake air amount by the control of the electromagnetic throttle valve 132 and the intake valve 112 is referred to as “working angle / throttle cooperative control”.
[0035]
FIG. 6 is a graph showing the operating angle / throttle cooperative control characteristics. The solid line in the figure is an equal intake air amount line, and the intake air amount increases as it goes upward. As can be understood from this, there are many combinations of the throttle opening and the operating angle in order to achieve a certain intake amount. In the normal operation mode, the throttle opening and the operating angle are selected along the fuel efficiency optimum line indicated by the alternate long and short dash line. However, when an abnormality occurs in the operating angle sensor 222, the fuel efficiency optimal line cannot always be realized. Therefore, in the operation mode at the time of occurrence of an abnormality (sensor abnormal operation mode), the intake air amount should be as close as possible to the target value, and the knock area (the area where knocking is likely to occur) should be avoided as close to the fuel efficiency optimum line In addition, the operating angle and the throttle opening are selected. Note that the target value of the operating angle and the target value of the throttle opening are determined by the operation target value determination unit 12 (or the intake air amount adjustment mechanism control unit 18) according to the required load of the engine 100.
[0036]
B. First embodiment:
FIG. 7 is a flowchart showing the procedure of the abnormality diagnosis process for the working angle sensor in the first embodiment. In steps S <b> 1 to S <b> 3, the abnormality diagnosis unit 16 determines whether a main abnormality or a temporary abnormality has occurred in the operating angle sensor according to the determination conditions described above. If neither this abnormality nor provisional abnormality has occurred and the operating angle sensor is normal, the intake air amount adjustment mechanism control unit 18 executes normal cooperative control in step S7. That is, the throttle opening and the operating angle of the intake valve 112 are selected along the fuel efficiency optimum line shown in FIG.
[0037]
FIG. 8 shows an operation when the working angle sensor 222 shifts from the temporary abnormality to the present abnormality. FIG. 8A shows the time change of the duty of the working angle control signal Sag (FIG. 2), FIG. 8B shows the time change of the working angle, and FIGS. 8C and 8D show temporary abnormalities. The time changes of the flag and the abnormal flag are shown. If it is determined in step S2 in FIG. 7 that there is a temporary abnormality, the intake air amount adjustment mechanism control unit 18 sets the duty of the operating angle control signal Sag to zero in step S5 (time t1 in FIG. 8). When the duty of the working angle control signal Sag becomes zero, the cam 211 is pushed by the valve spring 151 shown in FIG. 2, and the cam 211 gradually moves in the right direction together with the shafts 212 and 223 to become the minimum working angle θmin (FIG. 8 (b)). Therefore, the intake air amount adjustment mechanism control unit 18 adjusts the intake air amount by adjusting the opening of the throttle valve 132 based on such a change in the operating angle.
[0038]
However, since the actual operating angle (referred to as “actual operating angle”) is unknown while the temporary abnormality (and the main abnormality) is occurring, the intake air amount adjustment mechanism control unit 18 has one point in FIG. The estimated value of the working angle is used as indicated by the chain line. This estimated operating angle is determined so as to take a value greater than the actual operating angle. The reason for this is that if the estimated operating angle is greater than or equal to the actual operating angle, the throttle opening set based on the estimated operating angle will be small, and the intake amount realized thereby will be kept smaller than the target intake amount. This is because the engine output can be prevented from becoming excessive. From this point of view, it is preferable to set the estimated working angle so that the estimated working angle gives an intake amount larger than the actual working angle. In other words, in the intake valve characteristic shown in FIG. 4B, it is more preferable that the estimated operating angle has a value closer to the maximum intake amount operating angle θpeak than the actual operating angle.
[0039]
In an actual driving state, it is difficult to confirm whether or not the estimated operating angle is greater than or equal to the actual operating angle. Therefore, for example, in a factory, in various operating conditions, a test for reducing the duty of the working angle control signal Sag to zero is performed to measure a change in the actual working angle, and a change in the estimated working angle based on the duty change. Is created (referred to as an “estimated operating angle map”). In actual operation, if the estimated operating angle is determined from the duty change according to the estimated operating angle map, the estimated operating angle is set so that the estimated operating angle is larger than the actual operating angle. Is possible.
[0040]
When the temporary abnormality continues for a predetermined time and shifts to this abnormality at time t2 in FIG. 8, the intake air amount adjustment mechanism control unit 18 gradually increases the duty of the operating angle control signal to a predetermined value (step S5 in FIG. 7). In the example of FIG. 8A, the duty increases linearly up to the duty DTpeak (FIG. 4A) corresponding to the maximum intake air amount operating angle θpeak after the duty increases in a stepped manner by a certain amount at time t2. is doing. Note that the locus of change in duty may be a curve instead of a straight line. Further, the duty value reached after the gradual increase can be set to any value (for example, the maximum operating angle) other than the duty DTpeak corresponding to the maximum intake air amount operating angle θpeak.
[0041]
As can be understood from FIG. 8, in the abnormal state as well, in the same way as in the temporary abnormal state, the estimated operating angle is determined to take a value greater than the actual operating angle. Alternatively, the estimated working angle is set so that the estimated working angle gives an intake amount larger than the actual working angle.
[0042]
In the example of FIG. 8, when the duty of the working angle control signal Sag increases to a predetermined value Dpeak in this abnormal state, a certain time sufficient for the actual working angle to reach the value θpeak corresponding to the signal value is The duty of the angle control signal Sag is held at the value Dpeak. Thereafter, the intake air amount adjustment mechanism control unit 18 sets the duty value to the holding duty DThold and maintains the actual operating angle. Here, “holding duty DThold” means a duty required to keep the working angle constant, and is usually a value smaller than a duty value required to change the working angle. Is normal.
[0043]
As described above, in the sensor abnormal operation mode of the first embodiment, since the estimated operating angle is set so that the estimated operating angle is larger than the actual operating angle, it is possible to prevent the intake air amount from becoming excessively large. . As a result, there is an advantage that the output of the engine 100 can be prevented from becoming excessive.
[0044]
By the way, in the procedure of FIG. 7, there is a case where the temporary abnormal state is restored to the normal state (steps S3 and S6). Before describing the operation of the embodiment at this time, first, the operation of the comparative example will be described with reference to FIG. In this comparative example, when a temporary abnormality occurs in the operating angle sensor at time t11 and the duty of the operating angle control signal becomes zero and the actual operating angle decreases, the driver then responds as engine output decreases. It is assumed that the accelerator is depressed (FIG. 9 (a)). At this time, the throttle opening increases as the accelerator opening (accelerator depression amount) increases. However, since the actual operating angle is the minimum operating angle θmin, even if the throttle opening is fully opened, The amount does not increase so much. Thereafter, when the operating angle sensor returns to normal at time t12, the duty of the operating angle control signal rapidly increases to a value suitable for the accelerator opening, and the actual operating angle also increases correspondingly. When the actual operating angle suddenly increases, the intake air amount increases accordingly, so that the output of the engine 100 increases rapidly and the vehicle accelerates rapidly. As described above, when the operating angle control signal is suddenly increased when the operating angle sensor returns to normal from the temporary abnormality, sudden acceleration that is not intended by the driver may occur.
[0045]
FIG. 10 is an explanatory diagram showing an operation when the working angle sensor returns to normal from the temporary abnormality in the first embodiment. The solid line in FIG. 10A indicates the accelerator depression amount, and the alternate long and short dash line indicates the limit value of the accelerator opening (also referred to as “accelerator opening limit”). Here, the “accelerator depression amount” means the amount by which the driver actually depressed the accelerator, and the “accelerator opening value” is determined by the driving target value determination unit 12 (FIG. 1) from the accelerator depression amount. This means the required load value. Normally, the accelerator depression amount and the accelerator opening are equal or proportional, but in the example of FIG. Specifically, when the accelerator depression amount exceeds the accelerator opening limit, the accelerator opening value is set to the limit value. In the first embodiment, when the operating angle sensor returns to normal at time t12, the accelerator opening limit is set to a predetermined relatively low value in step S6 of FIG. a) dashed line). The solid line in FIG. 10 (b) shows the change in the accelerator opening value determined according to the accelerator opening restriction. As shown in FIG. 10 (c), the duty of the operating angle control signal increases according to the accelerator opening value, but the accelerator opening value is suppressed to a value smaller than that of the comparative example shown in FIG. Therefore, the operating angle does not increase rapidly after normal return. As a result, it is possible to prevent the intake air amount from rapidly increasing and suddenly accelerating.
[0046]
In the example of FIG. 10, the accelerator opening value is limited, but instead, the operating angle (that is, the duty of the operating angle control signal) may be limited. Also with this configuration, it is possible to prevent sudden acceleration (sudden increase in engine output) when the operating angle sensor returns to normal.
[0047]
C. Second embodiment:
FIG. 11 is an explanatory diagram showing an operation when the working angle sensor shifts from the temporary abnormality to the main abnormality in the second embodiment, and corresponds to FIG. 8 of the first embodiment. The second embodiment is different from the first embodiment only in the setting of the estimated working angle when an abnormality occurs in the working angle sensor, and other configurations and operations are the same as those in the first embodiment.
[0048]
In the second embodiment, as shown in FIG. 11B, the estimated operating angle is set to the maximum intake air amount operating angle θpeak. FIG. 12 is an explanatory diagram showing an intake air amount control method in the second embodiment. The estimated operating angle is set to the maximum intake air amount operating angle θpeak, and the intake air amount is set to the target intake air amount Vt (a value determined by the operation target value determining unit 12 in FIG. 2 from the accelerator opening by reducing the throttle opening. ). However, the actual working angle is always a value equal to or smaller than the estimated working angle θpeak as shown by the solid line in FIG. Therefore, the intake air amount is always kept at a value equal to or less than the target value determined from the accelerator opening. As a result, it is possible to more reliably prevent the output of the engine 100 from becoming excessive and sudden acceleration.
[0049]
D. Third embodiment:
FIG. 13 is an explanatory diagram showing an operation when the working angle sensor returns to normal from the temporary abnormality in the third embodiment. The third embodiment is different from the first embodiment or the second embodiment in that a limit is imposed on the change in the working angle when the working angle sensor returns to normal. Other configurations and operations are the same as those in the first embodiment. This is the same as the first embodiment or the second embodiment.
[0050]
As shown in FIG. 13 (a), in the third embodiment, when the working angle sensor returns to normal, the working angle increase rate limit SL1 and the decrease rate limit SL2 are set. In other words, the change in the target operating angle value is limited to a change rate that is greater than or equal to the decrease rate limit SL2 and less than or equal to the increase rate limit SL1. As shown in FIG. 13B, when the actual operating angle is lower than the target operating angle when a temporary abnormality occurs, the intake air amount adjusting mechanism control unit 18 when the operating angle sensor returns to normal. Is set so that the working angle target value once coincides with the actual working angle, and then asymptotically approaches the initial working angle target value determined by the operation target value determining unit 12 (solid line in FIG. 13A). In addition, the corrected working angle target value is gradually increased according to the increase rate limit SLup. Further, the intake air amount adjusting mechanism control unit 18 corrects the target value of the throttle opening as shown in FIG. 13C in accordance with the change in the operating angle. Thus, if the rate of increase of the working angle is limited, it is possible to prevent the actual working angle from rapidly increasing even when the difference between the actual working angle and the working angle target value when the working angle sensor returns to normal is large. . As a result, it is possible to prevent sudden acceleration due to a sudden increase in engine output.
[0051]
FIG. 14 shows an example in the third embodiment where the actual operating angle is higher than the target operating angle when a temporary abnormality occurs. In FIG. 14, it is assumed that the actual working angle does not decrease to the minimum working angle for some reason when a temporary abnormality occurs. In this case, when the operating angle sensor returns to normal, the intake air amount adjustment mechanism control unit 18 sets the operating angle target value to once match the actual operating angle, and then the operation target value determining unit 12. The corrected working angle target value is gradually decreased according to the descent rate limit SLdown so as to gradually approach the initial working angle target value determined by. The intake air amount adjusting mechanism control unit 18 further corrects the target value of the throttle opening as shown in FIG. 14C according to the change in the operating angle. Thus, if the rate of decrease of the operating angle is limited, it is possible to prevent the actual operating angle from rapidly decreasing when the operating angle sensor returns to normal, and thus it is possible to prevent engine stall.
[0052]
E. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
[0053]
E1. Modification: 1
In the above-described embodiment, the working angle sensor does not return to the normal state when it enters the abnormal state, but may return to the normal state when a specific condition is satisfied even after shifting to the abnormal state. In this case, it is preferable to perform a control operation similar to the control operation performed when the temporary abnormal state described above returns to the normal state.
[0054]
In addition, the abnormality diagnosis unit 16 may simply determine whether or not an abnormal state occurs without providing a distinction between the temporary abnormal state and the abnormal state in the working angle sensor. In this specification, the term “abnormal” includes both provisional abnormalities and actual abnormalities.
[0055]
E2. Modification: 2
In the above embodiment, when it is determined that the working angle sensor is in a temporary abnormal state, the duty of the working angle control signal is set to zero so that the working angle becomes the minimum value. The intake air amount adjusting mechanism control unit 18 may be configured to output a drive signal for changing the operating angle along a predetermined locus to the variable valve mechanism 200. At this time, the intake air amount adjustment mechanism control unit 18 estimates the actual change in the operating angle according to the change in the drive signal, and adjusts the opening of the throttle valve based on the estimated change in the operating angle. It is preferable to be configured.
[0056]
E3. Modification: 3
Although the gasoline engine has been described in the above embodiment, the present invention can be applied to various internal combustion engines other than the gasoline engine.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a configuration of a control device in an embodiment.
FIG. 2 is an explanatory view showing an example of the structure of a variable valve mechanism 200. FIG.
FIG. 3 is an explanatory diagram showing an example of a relationship between a crank angle and a valve lift amount.
FIG. 4 is a graph showing a working angle characteristic of an intake valve.
FIG. 5 is a graph showing output characteristics of a working angle sensor.
FIG. 6 is a graph showing operating angle / throttle cooperative control characteristics;
FIG. 7 is a flowchart showing a procedure of abnormality diagnosis processing for the working angle sensor in the first embodiment.
FIG. 8 is an explanatory diagram showing an operation when the working angle sensor shifts from a temporary abnormality to a main abnormality in the first embodiment.
FIG. 9 is an explanatory diagram showing an operation of a comparative example in the case of returning to normal from a temporary abnormality.
FIG. 10 is an explanatory diagram showing the operation of the first embodiment in the case of normal recovery from a temporary abnormality.
FIG. 11 is an explanatory diagram showing an operation when the working angle sensor shifts from a temporary abnormality to a main abnormality in the second embodiment.
FIG. 12 is an explanatory diagram showing an intake air amount control method in the second embodiment.
FIG. 13 is an explanatory diagram showing an operation when the working angle sensor returns to normal from a temporary abnormality in the third embodiment.
FIG. 14 is an explanatory diagram showing an operation when the working angle sensor returns to normal from a temporary abnormality in the third embodiment.
[Explanation of symbols]
10 ... Control unit
12 ... Driving target value determination unit
14: Intake amount calculation unit
16: Abnormality diagnosis section
18 ... Intake amount adjusting mechanism control unit
100 ... gasoline engine
101 ... Fuel injection valve
102 ... Spark plug
104 ... Knock sensor
106 ... Water temperature sensor
108: Rotational speed sensor
109 Accelerator sensor
110 ... Intake pipe
112 ... Intake valve
120 ... exhaust pipe
122 ... Exhaust valve
126 ... Air-fuel ratio sensor
128 ... Catalyst
130 ... Air flow meter
132 ... Electromagnetic throttle valve
134 ... Surge tank
136 ... temperature sensor
138 ... Pressure sensor
151 ... Valve spring
152 ... Valve lifter
156 ... Cam follower
200: Variable valve mechanism
210 ... Cam mechanism
211 ... Cam
212 ... Camshaft
215 ... Attachment
220 ... Actuator
221: Electric motor
222 ... Working angle sensor
223 ... Moveable shaft
224 ... Electric motor drive unit
200: Variable valve mechanism

Claims (4)

A control device for an internal combustion engine,
A throttle valve,
A variable valve mechanism for adjusting a valve opening characteristic of an intake valve provided in a combustion chamber of the internal combustion engine;
A target value determining unit that determines an operation target value of the throttle valve and the variable valve mechanism in response to a load request to the internal combustion engine;
An intake air amount adjustment mechanism control unit that adjusts the intake air amount to the combustion chamber by controlling the operation of the throttle valve and the variable valve mechanism based on the operation target value;
A working angle sensor provided in the variable valve mechanism for detecting a magnitude of a working angle of the intake valve;
An abnormality diagnosing unit for diagnosing an abnormality of the working angle sensor;
With
The intake air amount adjustment mechanism control unit, when the abnormality diagnosis unit detects an abnormality of the working angle sensor,
(I) outputting a drive signal for changing the working angle along a predetermined locus over time to the variable valve mechanism;
(Ii) estimating a time change of an actual operating angle according to a time change of the drive signal;
(Iii) A control device that adjusts the opening of the throttle valve based on the estimated time variation of the operating angle. The control device according to claim 1,
The estimated operating angle is set to a value that gives a larger intake amount than the actual operating angle. The control device according to claim 1 or 2,
When the abnormality diagnosis unit detects that the working angle sensor has returned from the abnormal state to the normal state, the actual working angle indicated by the working angle sensor is the target value determining unit. A control device that controls the operation of the variable valve mechanism so as to approach the target value of the operating angle determined by. The control device according to claim 3,
When the abnormality diagnosis unit detects that the operating angle sensor has returned from an abnormal state to a normal state, the intake air amount adjustment mechanism control unit adjusts the operating angle from the actual operating angle to the target operating angle value. A control device that sets an increase rate limit and a decrease rate limit for changes.

Images