JP2003148181A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the exhaust emission controlling performance and the operability even when a trouble related to the control system of an adjustable valve mechanism occurs. SOLUTION: When a trouble related to the control system of the adjustable valve timing mechanism (VTC) is detected (S2, S3), the operation region of the engine is detected and the trouble-time control is executed according to the operation region (S4-S8). As a result, the quantity of the valve overlapping is reduced and the external EGR quantity is increased. At the time, the torque compensation is executed in a first operation region for compensating the torque reduction following the trouble-time control (S7). On the other hand, in second and third operation regions where troubles cannot be controlled by the torque compensation, the gear ratio of a non-stage transmission CVT is changed to execute the output compensation control for increasing the engine rotation speed Ne (S8).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine, and more particularly to a failure control when a control system of a variable valve mechanism that variably controls valve timing of an intake valve or an exhaust valve has a failure.

[0002]

2. Description of the Related Art As a control performed when a variable valve mechanism that variably controls the opening / closing timing of an intake valve or an exhaust valve of an engine fails, there is known one in which the valve overlap amount is forcibly made small (Japanese Patent Laid-Open No. Hei 10 (1999) -264242). 7-139378). Further, when the valve lift characteristic is switched, the cylinder residual exhaust amount (internal EGR amount) and the external EG by the EGR means are used.
There is known a technique for preventing deterioration of exhaust emission by controlling the variable valve mechanism and the EGR means so that the total of the R amount (total EGR amount) becomes substantially constant (Japanese Patent Laid-Open No. 8-
158954).

[0003]

However, in the former case, N obtained by the internal EGR due to the valve overlap.
The Ox reduction effect cannot be obtained when the variable valve mechanism fails, which causes a problem that exhaust emission is deteriorated. Further, the latter can prevent deterioration of exhaust emission by making the total EGR amount substantially constant, but it is not intended for the case of failure of the variable valve mechanism in the first place, and retards when the variable valve mechanism fails. It does not take into consideration the torque decrease caused by the return to the side.

The present invention has been made in view of such conventional problems, and ensures exhaust purification performance and drivability even if a failure occurs in the control system of the variable valve mechanism. An object of the present invention is to provide a control device for an internal combustion engine that is made possible.

[0005]

Therefore, in the invention according to claim 1, a variable valve mechanism capable of variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve of an engine, and a part of engine exhaust are provided. When it is diagnosed that there is a failure in the control system of the variable valve mechanism, EGR means for controlling the flow rate and returning to the intake side, failure diagnosis means for diagnosing a failure related to the control system of the variable valve mechanism. In addition, the variable valve mechanism is controlled in a direction to reduce the valve overlap amount in which both the intake valve and the exhaust valve are open, and the EG is increased so as to increase the flow rate of the exhaust gas to be recirculated.
A failure control means for controlling the R means, and a torque compensation means for compensating the torque decrease of the engine due to the control at the time of the failure,
It is characterized by including.

According to the second aspect of the present invention, there is provided a variable valve mechanism capable of variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve of the engine, and a part of the exhaust gas of the engine to the intake side while controlling the flow rate. EGR means for recirculation, continuously variable transmission capable of steplessly controlling the gear ratio, failure diagnosis means for diagnosing a failure related to the control system of the variable valve mechanism, and failure of the control system of the variable valve mechanism. When it is diagnosed that the intake valve and the exhaust valve are both open, the variable valve mechanism is controlled so as to reduce the valve overlap amount, and the flow rate of exhaust gas to be recirculated is increased. Failure control means for controlling the EGR means,
Output compensating means for compensating for a reduction in engine output due to the failure control by changing the gear ratio of the continuously variable transmission to increase the engine rotation speed.

The invention according to claim 3 is characterized in that the output compensation by the output compensating means is performed only in a low rotation and high load region. According to a fourth aspect of the invention, a variable valve mechanism capable of variably controlling the opening / closing timing of at least one of an intake valve and an exhaust valve of the engine, and an EGR that recirculates a part of the exhaust gas of the engine to the intake side while controlling the flow rate. Means, a failure diagnosing means for diagnosing a failure related to the control system of the variable valve mechanism, and both of the intake valve and the exhaust valve open when a failure is diagnosed in the control system of the variable valve mechanism. A failure time control means for controlling the variable valve mechanism in a direction to reduce the valve overlap amount being valved, and for controlling the EGR means so as to increase the flow rate of exhaust gas to be recirculated, and the failure time control means A region determining means for determining an operating region in which the torque reduction of the engine can be compensated and an operating region in which the compensation is not possible, and an operating region in which the torque reduction of the engine associated with the failure control can be compensated, The torque compensating means for compensating the engine torque drop due to the failure control and the gear ratio of the continuously variable transmission are changed in the operating range where the engine torque drop due to the failure control cannot be compensated. And an output compensating means for compensating for a decrease in engine output due to the failure control by increasing the engine speed.

[0008]

According to the first aspect of the present invention, a failure relating to the control system of the variable valve operating mechanism is diagnosed, and at the time of failure, the valve overlap amount in which both the intake valve and the exhaust valve are open. The drive of the variable valve mechanism is controlled so as to reduce the amount of EGR, and the drive of the EGR means is controlled so as to increase the flow rate of the exhaust gas (external EGR) to be recirculated. It is possible to prevent deterioration of exhaust emission by supplementing the decrease amount of the internal EGR with the external EGR by the EGR means while surely avoiding the situation that causes the above.

Further, since the torque compensating means controls the engine such as the increase of the intake air amount and the advance of the ignition timing, the torque decrease caused by the failure control can be compensated.
The drivability can be secured. According to the invention of claim 2, similarly to the invention of claim 1, instability of combustion and deterioration of exhaust emission can be prevented. Further, since the engine speed is increased by changing the gear ratio of the continuously variable transmission by the output compensating means, it is possible to compensate for the decrease in engine output caused by the torque decrease due to the failure control.

That is, when the valve overlap amount is reduced and the external EGR amount is increased in a predetermined operating range, the intake air amount is increased and the ignition timing is advanced (torque compensation control). The required engine torque cannot be compensated. Therefore, in such an operating region, the engine output is compensated by increasing the engine rotation speed. Since the gear ratio and the engine rotation speed are set so that the output is constant, the vehicle speed is kept constant.

According to the third aspect of the present invention, the output compensation control for increasing the engine rotation speed is performed only in the low rotation / high load region, whereby unnecessary change of the gear ratio can be avoided and fuel consumption can be reduced. Can be maintained well. According to the invention of claim 4, since the operating region is determined and the torque compensation control or the output compensation control is executed according to the operating region, the decrease in the engine torque due to the preceding failure time control is appropriately controlled. Can automatically compensate (torque compensation or output compensation).

[0012]

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 schematic diagram showing a configuration of a vehicle internal combustion engine (engine). In FIG. 1, an automatic transmission 2 is provided on the output side of the engine 1. The automatic transmission 2 is connected to a torque converter 2A interposed on the output side of the engine 1 via the torque converter 2A. Transmission 2B, and hydraulic actuator 2C (not shown) for connecting / disconnecting various transmission elements in the transmission 2B
And Here, in the present embodiment, as the automatic transmission 2, a continuously variable transmission (for example, a toroidal type continuously variable transmission) capable of continuously controlling the gear ratio is used.

A throttle valve 4 is provided in the intake passage 3 of the engine 1 and controls the intake air amount Qa in accordance with the opening thereof. In the exhaust passage 5 of the engine 1, an exhaust gas purification device 6 that purifies exhaust gas is interposed. Further, the exhaust passage 5 is provided with an EGR passage 7 branching upstream from the exhaust purification device 6 and connected to the intake system. An EGR valve 8 is provided in the EGR passage 7,
The amount of exhaust gas that recirculates to the intake side according to the opening degree (external EG
R amount) is controlled. Then, by controlling the opening degree of the EGR valve 8 in the operating region (EGR region) where the engine speed and the engine load are equal to or less than a predetermined value,
Since the exhaust gas of the engine 1 is recirculated to the intake system to lower the temperature in the combustion chamber, the production of NOx is suppressed, and exhaust emission (NOx) is reduced (EGR control).

FIG. 2 is a schematic diagram showing the structure of each cylinder of the engine 1. In FIG. 2, each cylinder of the engine 1 has a fuel injection valve (injector) 10 for injecting fuel into the combustion chamber 9, and a spark plug 1 for performing spark ignition in the combustion chamber 9.
1 is provided, fuel is injected from the injector 10 to the air taken in through the intake port 12 and the intake valve 13 of each cylinder to form a mixture, and the mixture is formed in the combustion chamber 9 It is compressed inside and ignited by spark ignition by the spark plug 11. The combustion exhaust is discharged to the exhaust port 15 via the exhaust valve 14.

The intake valve 13 and the exhaust valve 14
Are opened and closed by cams provided on the intake side cam shaft 16 and the exhaust side cam shaft 17, respectively. Here, the intake side camshaft 16 has a known variable valve timing mechanism (VTC) 18 for varying the opening / closing timing of the valve by changing the rotational phase of the camshaft with respect to the crankshaft (not shown).
Is provided.

Therefore, the intake valve 13 and the exhaust valve 14 are advanced by advancing the opening / closing timing of the intake valve 13.
Valve overlap amount (O /
L) can be enlarged, and the valve overlap amount (O / L) can be reduced by delaying. It should be noted that, due to the increase of the internal EGR due to the securing of the valve overlap amount (O / L), the exhaust emission (N
Ox) can be reduced.

The control unit (C / U) 20 includes an accelerator opening degree sensor 21 for detecting an accelerator opening degree,
A throttle opening sensor 22 for detecting the throttle opening TVO and an air flow meter 2 for detecting the intake air amount Qa.
3, a crank angle sensor 24 for detecting the crank angle position,
Cam sensor 2 for detecting the rotational position of the intake side cam shaft 12
5. Output signals from various sensors such as the vehicle speed sensor 26 that detects the vehicle speed VSP are input. The engine speed Ne is calculated based on the output signal from the crank angle sensor 24.

The control unit C / U20
During normal operation, the operating state is grasped based on these input signals, and predetermined arithmetic processing is performed to perform the fuel injection amount Tp of the engine 1, the fuel injection timing IT, and the ignition timing A.
Along with setting the DV, the automatic transmission (continuously variable transmission)
2. Control the throttle valve 4, EGR valve 8 and variable valve timing mechanism (VTC) 18.

Specifically, an optimum gear ratio is set based on the detected throttle opening TVO and the vehicle speed VSP,
By controlling the hydraulic actuator so as to attain the gear ratio, the automatic transmission (continuously variable transmission) 2 is controlled so as to obtain the optimum gear ratio. Based on the output signals from the crank angle sensor 24 and the cam sensor 25, the rotational phase of the intake side camshaft 16 with respect to the crankshaft is detected to detect the intake valve 1.
The variable valve timing mechanism that detects the opening / closing timing of No. 3 and sets the target advance value or the retard value according to the operating state so that the rotational position of the intake side camshaft 16 becomes the target advance value or the retard value. By controlling the (VTC) 18, the opening / closing timing of the intake valve 13 is controlled.

Further, in the EGR region, the opening degrees of the throttle valve 4 and the EGR valve 8 are controlled so that the target EGR rate is set according to the operating condition.
The above is the control during normal operation, but when a failure related to the control system of the variable valve timing mechanism (VTC) 18 is diagnosed, the following failure time control is executed.

(1) Valve overlap amount (O / L)
Variable valve timing mechanism (VTC) to reduce
Control the drive of. That is, in this embodiment,
The opening / closing timing of the intake valve 13 is retarded. This avoids a situation where the internal EGR becomes excessive in the low load region and ensures combustion stability. (2) The drive of the EGR valve 8 is controlled so as to increase the EGR amount. As a result, the amount of internal EGR reduced as the valve overlap amount is reduced is reduced to E by EGR control.
It can be compensated by the amount of GR and suppresses deterioration of exhaust emission.

In order to prevent the valve overlap amount (O / L) from being reduced (retarding the closing timing of the intake valve) and the decrease in torque due to the increase in the (external) EGR amount due to the failure control, At the same time, the throttle opening TVO and the ignition timing ADV are adjusted (torque compensation control). Further, in a predetermined operating region where the torque compensation control cannot cope with the torque reduction caused by the failure control, the gear ratio of the continuously variable transmission 2 is changed to increase the engine rotation speed Ne to output the engine output. Is compensated (output compensation control).

The above control will be described with reference to the flowchart shown in FIG. In step 1 (denoted as S1 in the figure; the same applies hereinafter), the engine speed Ne and the throttle opening TVO are read. In step 2, a failure related to the control system of the variable valve timing mechanism (VTC) 18 is diagnosed. Such failure diagnosis is performed as follows, for example.

Crank angle sensor 24 and cam sensor 25
The current rotation phase of the intake-side camshaft is detected based on the output signal from, and the detected current rotation phase is compared with the target rotation phase set according to the operating state. If the difference is equal to or larger than the set threshold value, a failure related to the control system (cam sensor or the like) of the variable valve timing mechanism (VTC) is diagnosed. Note that this is an example of failure diagnosis, and failure diagnosis by other methods may be used.

In step 3, the result of failure diagnosis is judged. As a result of the failure diagnosis, if there is a failure, the process proceeds to step 4, and if there is no failure, this control ends (that is,
Perform control during normal operation). In step 4, the read engine speed Ne and throttle opening TVO
The engine load is estimated based on.

In step 5, the current engine operating range is detected based on the read engine speed Ne and the engine load estimated in step 4. In step 6,
Region determination is performed to determine which of the set regions the current engine operating region is in. This region determination is for executing a failure control suitable for the operating region, and in the present embodiment, three operating regions are set.

Here, the three operating regions will be described. FIG. 4 is a diagram showing the relationship between engine rotation speed and torque. In FIG. 4, A (solid line) indicates the full opening torque when the variable valve timing mechanism (VTC) is operated without operating the EGR control, and B (dotted line) is the variable valve timing mechanism (VTC) and EGR. C (dashed line) is the full-open torque when control is not operated, and E is the EGR value without operating the variable valve timing mechanism (VTC).
The full-open torque when the control is operated is shown.

As shown in the figure, the first operating region is a region where the required torque can be secured even when the EGR control is operated without operating the variable valve timing mechanism (as the VTC most retarded position). And an area where the required torque can be secured when neither the variable valve timing mechanism (VTC) nor the EGR control is operated,
The region where the required torque can be secured when the variable valve timing (VTC) is operated without operating the control is the third operating region.

Returning to step 6, as a result of the area determination, if the current operation area is the first operation area, step 7
If it is the second or third operation region, the process proceeds to step 8.
In step 7, the failure control for the first operating range is executed. The specific control content is shown in FIG. The drive of the variable valve timing mechanism (VTC) 18 is controlled so as to retard the opening / closing timing of the intake valve 13 (that is, the direction in which the valve overlap amount (O / L) is reduced), and set to the most retarded position. (FIG. 5 (a)).

Then, the valve overlap amount (O
/ L) to reduce the decrease in internal EGR by reducing external E
The EGR valve 8 is controlled so as to increase the GR amount (FIG. 5 (b)). By such control at the time of failure, it is possible to surely prevent the situation such that the combustion becomes unstable, and also prevent the deterioration of the exhaust emission (NOx).

Here, the torque decreases as the valve overlap amount is reduced by the failure control and the (external) EGR amount is increased accordingly. The first operating area is
As mentioned above, the variable valve timing mechanism (VTC)
Without operating (minimum valve overlap) E
Even when the GR control is operated, the operating range is where the required torque can be secured. Therefore, the amount of torque decrease due to the failure control is compensated by adjusting the throttle opening TVO and the ignition timing ADV (torque compensation control). ).

Specifically, the throttle opening TVO is increased to increase the intake air amount (FIG. 5 (c)) and the ignition timing ADV is advanced (FIG. 5 (d). A failure time control for a few operation ranges is executed.Specific control contents are shown in Fig. 6. As in the first operation range, the failure time control, that is, the valve overlap amount (O /
Variable valve timing mechanism (VT)
C) EG is controlled so that the external EGR amount is increased.
The R valve 8 is controlled (FIGS. 6A and 6B).

As a result, it is possible to surely prevent the situation that the combustion becomes unstable, and also to exhaust the exhaust gas (NOx).
Will surely prevent the deterioration of. Here, the second operation region is the variable valve timing mechanism (VTC) and EGR.
The operating region where the required torque can be secured when the control is not operated, and the third operating region is the operating region where the required torque can be secured by operating the variable valve timing mechanism (VTC) without operating the EGR control. Therefore, the variable valve timing mechanism (VT
Since C) and the EGR control are operated, it is not possible to compensate for the torque decrease caused thereby.

Therefore, in the second and third operation regions, the output compensation control for compensating the engine output is executed by changing the gear ratio of the continuously variable gear ratio 2 to increase the engine rotation speed Ne (FIG. 6 ( e)). Specifically, the engine rotation speed Ne is increased as follows. The third operation region is a region where the required torque can be secured when the variable valve timing mechanism (VTC) is operated without operating the EGR control, and therefore the valve overlap amount is reduced by the failure control (that is, Due to the stop of VTC) and the increase of the external EGR amount (execution of EGR control), the torque that can be secured is reduced to the first operation region (for example, Tx in FIG. 4).

Therefore, in order to compensate for the output decrease due to the torque decrease Tx, it is necessary to increase the engine rotation speed until it is located on the equal horsepower line in the first operating region. For example, when increasing the engine rotation speed while keeping the torque constant, the rotation speed corresponding to the arrow X in FIG. 4 is increased while changing the gear ratio of the continuously variable transmission. On the other hand, the second operation region is a region where the required torque can be secured when the variable valve timing mechanism (VTC) and the EGR control are not operated, and therefore, when executing the failure control, the external EG
It is also possible to avoid the torque decrease by stopping the increase of the R amount.

However, in this embodiment, the amount of external EGR is increased in order to secure the exhaust gas purification performance, so that the torque that can be secured is reduced to the first operating range (in FIG. 4). Ty). Therefore, in order to compensate for the output decrease due to this torque decrease Ty, it is necessary to increase the engine rotation speed until it is located on the equal horsepower line in the first operating region, as in the case of the third operating region. For example, when the engine rotation speed is increased with the torque kept constant, the arrow Y in FIG. 4 is changed while changing the gear ratio of the continuously variable transmission.
Increase the rotation speed for minutes.

As the engine speed Ne is increased, the throttle opening TVO and the ignition timing A are increased.
Adjust DV (FIGS. 6C and 6D). As described above, in the present embodiment, the torque compensation control is performed in the first operating region and the output compensation control is performed in the second and third operating regions, which cannot be handled by the torque compensation control, with respect to the torque decrease due to the failure control. I am trying to do it.

By performing different compensation (torque compensation or output compensation) control depending on the operating region in this manner, optimal control can be executed, change in the gear ratio can be minimized, and fuel consumption is good. Can be maintained at As described above, even when a failure related to the control system of the variable valve timing mechanism (VTC) occurs, the situation of combustion instability is avoided, and the NOx reduction effect obtained by the internal EGR is reduced by the external EGR. It is possible to prevent the deterioration of the exhaust emission by increasing the amount of and to ensure the drivability.

In the present embodiment, the variable valve timing mechanism (VTC) for varying the valve timing (phase) while keeping the valve lift fixed has been described, but the invention is not limited to this, and the valve timing can be varied. Other types may be used as long as they are used. Further, the invention is not limited to controlling only the valve timing of the intake valve, and may control the valve timing of the exhaust valve. In this case, the valve timing of the exhaust valve is controlled to advance, so that the valve overlap amount (O / L) can be controlled to decrease.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram showing the structure of each cylinder of the internal combustion engine.

FIG. 3 is a flow chart showing the same control at the time of failure.

FIG. 4 is a diagram showing a relationship between engine rotation speed and torque.

FIG. 5 is a diagram showing the contents of control at the time of a failure in the first operation region.

FIG. 6 is a diagram showing the contents of control at the time of failure in the second and third operation regions.

[Explanation of symbols]

1 engine 2 continuously variable transmission 3 intake passage 4 Throttle valve 5 exhaust passage 7 EGR passage 8 EGR valve 10 Combustion injection valve 11 Spark plug 13 Intake valve 14 Exhaust valve 18 Variable valve timing mechanism (VTC) 20 control unit (C / U) 21 Accelerator position sensor 22 Throttle opening sensor 23 Air Flow Meter 24 crank angle sensor 25 Cam sensor

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Claims (4)

[Claims] 1. A variable valve mechanism capable of variably controlling opening / closing timing of at least one of an intake valve and an exhaust valve of an engine, and EGR means for recirculating a part of exhaust gas of the engine to an intake side while controlling a flow rate. Failure diagnosis means for diagnosing a failure related to the control system of the variable valve mechanism, and when both of the intake valve and the exhaust valve are opened when it is diagnosed that there is a failure in the control system of the variable valve mechanism. The variable valve mechanism is controlled to reduce the valve overlap amount, and the failure control means for controlling the EGR means so as to increase the flow rate of the recirculated exhaust gas, and the engine for the failure control. A control device for an internal combustion engine, comprising: a torque compensating means for compensating for a decrease in torque. 2. A variable valve mechanism capable of variably controlling opening / closing timing of at least one of an intake valve and an exhaust valve of an engine, and EGR means for recirculating a part of exhaust gas of the engine to an intake side while controlling a flow rate. A continuously variable transmission capable of controlling the speed ratio steplessly, a failure diagnosing means for diagnosing a failure relating to the control system of the variable valve mechanism, and a case where it is diagnosed that there is a failure in the control system of the variable valve mechanism. In addition, the variable valve mechanism is controlled to reduce the valve overlap amount in which both the intake valve and the exhaust valve are open, and the EGR means is controlled to increase the flow rate of the exhaust gas to be recirculated. A failure control means, and an output compensation means for compensating for a reduction in engine output due to the failure control by increasing the engine speed by changing the gear ratio of the continuously variable transmission. Control device for an internal combustion engine according to symptoms. 3. The control device for an internal combustion engine according to claim 2, wherein the output compensation by the output compensating means is performed only in a low rotation / high load region. 4. A variable valve mechanism capable of variably controlling opening / closing timing of at least one of an intake valve and an exhaust valve of an engine, and EGR means for recirculating a part of exhaust gas of the engine to an intake side while controlling a flow rate. Failure diagnosis means for diagnosing a failure related to the control system of the variable valve mechanism, and when both of the intake valve and the exhaust valve are opened when it is diagnosed that there is a failure in the control system of the variable valve mechanism. The variable valve mechanism is controlled to reduce the valve overlap amount, and the failure control means for controlling the EGR means so as to increase the flow rate of the exhaust gas to be recirculated and the engine torque associated with the failure control. A region discriminating means for discriminating an operating region capable of compensating for the reduction and an operating region not capable of compensating for the reduction, and the fault in the operating region capable of compensating for the torque reduction of the engine due to the control at the time of the fault. Torque compensating means for compensating for the torque reduction of the engine due to the time control, and changing the gear ratio of the continuously variable transmission in the operating region where the compensation for the torque reduction of the engine due to the failure control is impossible. 3. A control device for an internal combustion engine according to claim 1 or 2, further comprising: output compensating means for compensating for a decrease in engine output due to the failure control by increasing a rotation speed.