JP2001263140A - Output control device for engine - Google Patents

Abstract

(57) [Problem] To prevent a measurement error of an intake air amount from occurring by restricting a maximum value of a throttle opening based on a valve timing. An air flow meter provided in an intake passage is provided.
, A throttle 6 for controlling the amount of intake air, and a variable mechanism 10 for changing at least the valve timing of the intake valve 8 according to the operating state. Means is provided for defining the throttle limit opening in accordance with the valve timing, and the throttle opening is controlled so as not to exceed the throttle limit opening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine output control device with variable valve timing.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. Hei 5-79763 discloses an engine having a plurality of intake / exhaust cams having different characteristics, in which the cams are switched in accordance with the operation state to change the valve timing in order to optimize the intake / exhaust efficiency of the engine. It is known from publications and the like.

[0003] In this case, when a failure occurs in the cam switching mechanism, the cam switching is inhibited and the accelerator-throttle characteristic is set for failure, thereby preventing the deterioration of drivability.

In order to change the valve timing of the intake valve or the exhaust valve depending on the operating state, it is known to change the rotational phase of the intake camshaft and delay the closing timing of the intake valve. By delaying the closing timing of the intake valve, a part of the air taken into the cylinder is pushed back to the intake system in the compression stroke, so that the compression pressure is reduced and vibration can be reduced.

[0005] When a hybrid vehicle is provided with an engine and a motor as a driving source and the engine is mainly used for charging a battery, the engine starts and stops more frequently than in a normal engine-driven vehicle. By greatly delaying the valve timing at the time of starting and stopping, engine vibration at the time of starting and stopping is suppressed, unpleasant vibration is suppressed, and the engine is quietened.

[0006] This may be applied to an engine having an idle stop function for automatically temporarily stopping the engine during idling, even if the engine is not a hybrid vehicle.

[0007]

As described above, particularly when the valve timing of the intake valve is greatly delayed, a part of the air sucked into the cylinder is pushed back to the intake system, thereby increasing the influence of the air pulsation. Therefore, an output error of the air flow meter is likely to occur.

The amount of intake air changes pulsatingly in accordance with the intake stroke of each cylinder. However, since the amount of pulsation of the pushed back air overlaps with the amount of pulsation, especially in a region where the throttle opening is relatively large, the amount of pulsation varies. Becomes large, which adversely affects the measurement accuracy of the intake air amount.

As a result, the fuel injection amount and the ignition timing determined based on the output of the air flow meter change from the optimum state in the operating state. For example, knocking occurs when the ignition timing advances too much. There is.

In order to avoid such a problem, an error of the air flow meter may be corrected according to a correction map set in accordance with the throttle opening and the number of revolutions. Since it is necessary to set at each timing, there is a problem that the calculation load of the microprocessor for calculating and controlling the fuel injection amount, the ignition timing, and the like is significantly increased.

The present invention has been proposed to solve such a problem. By limiting the maximum value of the throttle opening based on the valve timing at that time, no measurement error of the intake air amount occurs. The purpose is to be.

[0012]

According to a first aspect of the present invention, an intake air amount measuring means provided in an intake passage, a throttle for controlling an intake air amount, and at least a valve timing of an intake valve are changed in accordance with an operation state. In an engine having a variable mechanism, a means for defining a throttle limit opening in accordance with a valve timing is provided, and the throttle opening is limited so as not to exceed the throttle limit opening.

According to a second aspect of the present invention, in the first aspect, the throttle limit opening is the maximum opening within which a measurement error of the intake air amount measuring means determined according to the valve timing falls within an allowable range. The valve opening is set to the minimum opening within the allowable measurement error range determined according to the engine speed.

According to a third aspect of the present invention, there is provided an intake air amount measuring means provided in an intake passage, a throttle for controlling an intake air amount, and a variable mechanism for changing at least a valve timing of an intake valve in accordance with an operation state. The engine includes means for defining a throttle limit opening in accordance with a valve timing and an engine speed, and limits the throttle opening so as not to exceed the throttle limit opening.

In a fourth aspect based on the third aspect, the throttle limit opening is set to a maximum opening in which a measurement error of intake air amount measuring means determined according to valve timing and engine speed falls within an allowable range. Is set.

According to a fifth aspect of the present invention, in the first to fourth aspects, a means for determining a failure of the variable valve timing mechanism is provided, and the throttle opening is limited so as not to exceed the throttle failure limit opening at the time of failure determination. .

In a sixth aspect based on the fifth aspect, the throttle failure limit opening is set to a fixed small throttle opening.

[0018]

In the first to fourth aspects of the present invention, when the valve timing is variably controlled in accordance with the operating state, the region where the output error of the air flow meter occurs varies accordingly. In particular, when the valve timing of the intake valve is greatly retarded, such as when the throttle opening becomes large enough,
The output error of the air flow meter increases under the influence of air pushed back into the intake system during the compression stroke.

However, since the throttle allowable limit opening is set in accordance with the change in the valve timing so that the throttle opening is not made larger than this, the output error of the air flow meter is not affected by the air pulsation. Can be blocked. Therefore, by controlling the fuel supply amount, the ignition timing, and the like based on the output of the error-free air flow meter, proper control can always be performed, and knocking and the like can be reliably avoided.

Further, in the second and fourth aspects of the present invention, the throttle allowable limit opening can be set based on a map search or the like, and the calculation load of a calculation circuit such as a microprocessor can be reduced.

In the fifth and sixth aspects of the present invention, when a failure occurs in the variable valve timing mechanism, the throttle opening is limited to a smaller throttle limit opening.
It is possible to reliably prevent entry into the error area of the air flow meter 5, and to ensure accurate engine control even in such a case.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an engine body, 2 denotes an intake passage, and 3 denotes an exhaust passage. An air flow meter 5 and a throttle 6 are arranged in the intake passage 2 downstream of an air cleaner 4 in series.

The air flow meter 5 is a means for measuring the amount of intake air, and may be a hot wire type, a Karman vortex type sensor, a flap type, or a sensor for detecting a negative pressure of an intake system. The throttle 6 is an electronically controlled throttle that operates independently of the accelerator pedal, and its opening is controlled by a throttle motor, but may be a type of throttle that is linked to a normal accelerator.

A fuel injector 7 for supplying fuel to the engine is provided downstream of the throttle 6. The engine body 1 is provided with an intake valve 8 and an exhaust valve 9, and among them, a valve timing continuous variable mechanism 10 capable of continuously variably controlling at least the opening and closing timing of the intake valve 8 is provided.

The variable valve timing mechanism 10 can continuously delay the opening timing and closing timing of the intake valve 8, thereby lowering the actual compression pressure and reducing engine vibration when the engine is started or stopped. Or

An ignition plug 11 is provided in the engine body 1 and ignites the compressed air-fuel mixture at a predetermined timing.

In order to optimally control the fuel injection amount supplied from the fuel injector 7, the ignition timing of the ignition plug 11, the opening of the throttle 6, the valve timing of the intake valve 8, etc. , A controller 20 including a memory circuit, an input / output circuit, and the like.

Therefore, various signals representative of the operating state are input to the controller 20, that is, the intake air amount signal from the air flow meter 5, the crank angle sensor 21
, A cooling water temperature signal from a water temperature sensor 22 for detecting an engine cooling water temperature, an accelerator opening sensor 23
Speed sensor 2 that detects the accelerator opening signal from the vehicle and the vehicle speed
4, the actual throttle opening signal from the throttle sensor 25 for detecting the opening of the throttle 6, and the exhaust sensor 26 for the exhaust passage 2.
Air-fuel ratio signal from valve, valve timing continuously variable mechanism (C
VTC) Sensor 2 for detecting actual valve timing of 10
7, the actual valve timing signal is input. Based on these, the controller 20 sends a fuel injection signal to the fuel injector 7 and an ignition signal to the spark plug 11, and outputs a throttle control signal to the throttle 6 in accordance with the accelerator opening (target torque) and the number of revolutions. Further, it outputs a valve timing control signal to the continuously variable valve timing mechanism 10.

In this case, as for the opening of the throttle 6, the actual opening is detected, and feedback control is performed such that the actual opening is equal to the target value.

In the valve timing continuously variable mechanism 10, a solenoid valve is driven by a valve timing control signal, whereby the hydraulic pressure is controlled and the valve timing changes. In this case, the actual valve timing is detected and feedback-controlled by the controller 20 so as to match the target value.

Variable valve timing control mechanism 10
Is configured as shown in FIG. 2, for example.

A piston 44 is fitted between an inner cylinder 42 attached to the shaft end of the intake camshaft 41 and an outer cylinder 43 surrounding the inner cylinder 42. A retard-side oil chamber 45a and an advance-side oil chamber 45b are defined. The piston 44 is fitted to the inner cylinder 42 or the outer cylinder 43 via oblique splines.
Moves in either direction to the left or right in the drawing,
And the outer cylinder 43 rotate relative to each other. A cam sprocket (not shown) for transmitting the engine rotation to the intake camshaft 41 is attached to the outer cylinder 43, so that the intake camshaft 41 changes its phase with respect to the engine crankshaft according to the position of the piston 44.

The position of the piston 44 is controlled by the oil pressure supplied to the front and rear oil chambers 45a or 45b. In the figure, reference numeral 51 denotes a solenoid valve device for controlling the hydraulic pressure supply, which mainly comprises a spool 52 for switching the hydraulic pressure supply direction and a solenoid 53 for controlling the position of the spool 52.

When the spool 52 is driven to the left in the drawing, the engine oil pressure from the main gallery 54 is applied to the retard oil chamber 4 via the port c at the center of the spool and the retard oil passage 55a.
5a. At this time, the advance side oil chamber 45b is simultaneously connected to the drain passage 56 via the advance side oil passage 55b and the port b on the right side of the spool. This allows the piston 4
4 moves to the left, and the intake camshaft 41 rotates in the retard direction. On the contrary, when the spool 52 is driven rightward, the engine oil pressure from the main gallery 54 is introduced into the advance-side oil chamber 45b through the port c at the center of the spool and the advance-side oil passage 55b. The retard-side oil chamber 45a is connected to the drain passage 56 via the retard-side oil passage 55ba and the port a on the left side of the spool, whereby the piston 44 moves rightward and rotates the intake camshaft 41 in the advance direction. Let it.
In the illustrated state where the spool 44 is in the neutral position, each oil passage 54
a, b and oil chambers 45a, b are any ports a, b, c
Piston 4
4 and the intake camshaft 41 are fixed at the position at that time.

The operation timing of the intake valve 8 is controlled based on a signal from the cam position detection sensor 27 functioning as intake valve position detection means, and the controller 20 drives the solenoid 53 so that the predetermined intake valve operation timing is reached. Feedback control. For example, the reference angle signal (REF signal) emitted from the crank angle sensor 21 is used as a trigger to count the rotation angle until the cam target signal from the cam position detection sensor 27 is input. The actual position of the intake camshaft 41 is detected from the deviation from the determined cam reference position (see the sensor signal section in FIG. 2). The controller 20 drives the solenoid valve device 51 by PI control so that the actual cam position thus obtained becomes the target position. At this time, a dither signal is superimposed on the valve drive signal in order to remove the dead zone of the solenoid valve device 51 and increase the response (see the control signal section in FIG. 2).

Next, in the present invention, the controller 20 limits the maximum opening of the throttle 6 in connection with the variable control of the valve timing of the intake valve 8, thereby preventing a measurement error of the air flow meter 5 from occurring. Control is performed so that the air-fuel ratio and the ignition timing do not fluctuate from the optimal values and knocking or the like occurs.

Regarding the throttle opening control operation,
This will be described in detail according to the following flowchart.

FIG. 3 is a flowchart for setting the target throttle opening. First, at step S1, the target torque and the engine speed are read, and then at step S2, via the continuously variable valve timing mechanism 10, as will be described later. Is read in the valve timing of the intake valve 8 which is controlled as follows.

In step S3, the throttle opening T as shown in FIG.
The throttle opening Tθ is calculated by searching the map of θ.
The throttle opening Tθ increases as the target torque increases.

In step S4, a map for limiting the maximum throttle opening as shown in FIG. 9 is searched based on the valve timing and the engine speed at that time to determine the throttle limit opening Lθ.

The throttle limit opening Lθ is obtained from a throttle opening limit curve at the intersection of the valve timing at that time and the rotational speed. For example, when the valve timing is θ1 and the engine speed is n1 in the drawing, the throttle limit opening is approximately 30 °, which is a substantially intermediate value between 40 ° and 20 °. This map characteristic is obtained by sequentially determining the maximum throttle opening at which the output error of the air flow meter 5 does not exceed the allowable limit based on a predetermined unit valve timing and rotation speed by experiments.

Then, in step S5, the throttle opening Tθ obtained as described above and the throttle limit opening Lθ
And selects the smaller one of the values in step S6.
This is output as the target throttle opening.

FIG. 4 is a flowchart for setting the target valve timing. Here, first, in step S11, the target torque and the engine speed are read.
In step S12, a setting map of the valve timing VT as shown in FIG. 10 is searched based on the target torque and the rotation speed, and the searched valve timing VT is output as the target valve timing in step S13.

Next, the overall operation will be described.

The most suitable intake valve 8 according to the operating condition of the engine
Is selected, and this valve timing VT is greatly retarded when the engine is stopped and when the engine is started. As a result, the actual compression pressure is reduced, which is effective in suppressing engine vibration when starting or stopping the engine.

On the other hand, as the closing timing of the intake valve 8 is delayed, the amount of the air once sucked into the cylinder and pushed back to the intake system increases, and the pulsation of the air generated thereby causes the output error of the air flow meter 5 to decrease. It is easy to occur. This air pulsation increases as the opening of the throttle 6 increases, affecting the air flow meter 5 on the upstream side. Therefore, as the throttle opening increases, the reliability of the output of the air flow meter 5 decreases accordingly.

FIG. 11 shows the deviation (measurement error rate) between the measured flow rate of the hot wire air flow meter and the actual flow rate when the throttle opening and the valve timing are changed. At this time, at a certain rotational speed, the actual air amount tends to be larger than the measured value on the low speed side and smaller on the high speed side.

If the fuel injection amount and the ignition timing are controlled based on the output while the output error of the air flow meter 5 is large (error area), the proper proper air-fuel ratio and ignition timing cannot be obtained. If the ignition advance is too large under a relatively large load, knocking may occur.

However, in the present invention, the valve timing VT
And the throttle limit opening Lθ is set based on the engine speed at that time. When the throttle opening Tθ calculated from the target torque and the engine speed reaches the throttle limit opening Lθ, the throttle The opening does not increase. The throttle limit opening Lθ is set within an allowable error range of the output of the air flow meter 5.
For this reason, the throttle opening does not reach the error range of the air flow meter 5, and the fuel injection amount controlled based on the output of the air flow meter 5 at this time,
The ignition timing has an appropriate value that does not include the influence of the error.

Note that the limit opening Lθ of the throttle 6 becomes relatively small, for example, when the valve timing VT of the intake valve 8 is greatly delayed, and thus the engine output is limited. Valve timing V
The time T is greatly delayed in a region where the load is relatively small, such as when the engine is started or stopped, and there is substantially no problem even if the engine output is limited.

The next embodiment will be described with reference to the flowchart of FIG.

In this embodiment, the throttle limit opening Lθ
Is set only in accordance with the valve timing VT.

Steps S21 to S23 are the same as steps S1 to S3 in FIG.
In step S24 for setting the throttle limit opening, the throttle limit opening Lθ is searched from a table set based on the valve timing VT as shown in FIG.
I have decided.

As the throttle limit opening, the smallest throttle opening at which an error exceeding the allowable range of the air flow meter 5 occurs when the rotation speed is changed at the same valve timing is selected, and this is sequentially determined by the valve. The limit opening values obtained when the timing is changed by a predetermined amount are connected, and this is obtained as the throttle limit opening Lθ.

In step S25, the smaller of the calculated throttle opening Tθ and the throttle limit opening Lθ is determined as the target throttle opening, and is output.

Therefore, according to this embodiment, the set throttle limit opening Lθ is the smallest throttle opening at the valve timing.
This is the safest throttle opening. By doing so, the only parameter for setting the throttle limit opening Lθ is the valve timing VT, and the calculation load on the controller can be reduced accordingly.

Still another embodiment will be described with reference to the flowcharts of FIGS.

In this embodiment, when the continuously variable valve timing mechanism 10 fails, the throttle limit opening is set to a small opening so as not to enter the error area of the air flow meter.

In FIG. 6, steps S31 to S34 correspond to steps S21 to S24 in FIG.
Next, in step S35, a failure determination of the continuously variable valve timing mechanism 10 is performed.

Here, the failure determination will be described with reference to FIG.

At step S41, the current valve timing VTn is detected. Further, at step S42, the target valve timing VTt is read.
VTt is determined. If not, the process proceeds to step S44 until the predetermined delay time elapses, and VTn remains VTt even after the predetermined time elapses.
If not, a failure determination is made in step S45 assuming that the valve timing has not been controlled to the target.

On the other hand, in step S43, VTn =
If it is VTt, the process proceeds to step S46, and it is determined that there is no failure in the continuously variable valve timing mechanism 10.

Returning to FIG. 6, when it is determined in step S35 that there is no failure, the process proceeds to step S36.
The smaller of the throttle opening Tθ and the limit opening Lθ is selected, and the process proceeds to step S39.
, This is output as the target throttle opening.

On the other hand, if it is determined in step S35 that a failure has occurred, the throttle limit opening Mθ at the time of failure is calculated in step S37 with reference to a table as shown in FIG.

The throttle limit opening Mθ at the time of failure is a constant value, which is much smaller than the limit opening Lθ for a normal error, and is smaller than the accelerator opening (target opening). As a result, the actual torque is reduced, and the power performance is deteriorated. However, since it does not enter the error region of the air flow meter 5, knocking and the like can be reliably prevented.

Next, at step S38, the throttle opening Tθ, the limiting opening Lθ, and the limiting opening M at the time of failure are determined.
The smallest throttle opening is selected from θ, and this is output as the target throttle opening in step S39.

As described above, when a failure occurs in the continuously variable valve timing mechanism 10, the throttle opening becomes
The throttle opening Mθ at the time of failure is limited to the minimum opening that is surely out of the error area of the air flow meter 5. For this reason, although the power performance slightly decreases, the fuel injection amount and the ignition timing can be appropriately controlled, and knocking and the like can be reliably prevented.

Although the example in which the throttle 6 is provided with an electronically controlled throttle that operates independently of the accelerator has been described, if this is to be a throttle that is linked to the accelerator, a variable restriction for restricting the throttle opening is used. By providing a mechanism (a stopper or the like) and controlling the allowable range determined by the limiting mechanism to be the selected throttle limit opening, the throttle opening can be variably limited.

The above-described engine throttle opening restriction mechanism is most suitable for an engine of a hybrid vehicle or an idle stop vehicle, but is not limited thereto.
Of course, it can be applied to a normal engine.

It is apparent that the present invention is not limited to the above-described embodiment, and that various changes can be made within the scope of the technical idea.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a continuously variable valve timing mechanism.

FIG. 3 is a flowchart of a control operation according to the first embodiment.

FIG. 4 is a flowchart of a control operation.

FIG. 5 is a flowchart of a control operation according to the second embodiment.

FIG. 6 is a flowchart of a control operation according to a third embodiment.

FIG. 7 is a flowchart of a control operation.

FIG. 8 is a setting map of a throttle opening.

FIG. 9 is a setting map of a throttle limit opening.

FIG. 10 is a setting map of valve timing.

FIG. 11 is an explanatory diagram of characteristics of an air flow meter.

FIG. 12 is a setting table of a throttle limit opening.

FIG. 13 is a setting table of a throttle limit opening at the time of failure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 2 Intake passage 3 Exhaust passage 5 Air flow meter 6 Throttle 7 Fuel injector 8 Intake valve 10 Continuous variable valve timing mechanism 20 Controller

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Claims (6)

[Claims] An intake air amount measuring means provided in an intake passage;
An engine having a throttle for controlling an intake air amount and a variable mechanism for changing at least a valve timing of an intake valve in accordance with an operation state, comprising: means for defining a throttle limit opening in accordance with a valve timing; An output control device for an engine, wherein a throttle opening is limited so as not to exceed a limit opening. 2. The throttle limit opening is a maximum opening in which a measurement error of an intake air amount measuring means determined according to a valve timing falls within an allowable range, and according to an engine speed at the same valve timing. The engine output control device according to claim 1, wherein the determined opening is set to a minimum opening within which the measurement error falls within an allowable range. 3. An intake air amount measuring means provided in an intake passage,
In an engine having a throttle for controlling an intake air amount and a variable mechanism for changing at least a valve timing of an intake valve according to an operation state, a means for defining a throttle limit opening degree according to a valve timing and an engine speed is provided. An engine output control device for limiting the throttle opening so as not to exceed the throttle limit opening. 4. The engine according to claim 3, wherein the throttle limit opening is set to a maximum opening in which a measurement error of an intake air amount measuring means determined according to a valve timing and an engine speed falls within an allowable range. Output control device. 5. A system according to claim 1, further comprising means for judging a failure of the variable valve timing mechanism, wherein the throttle opening is limited so as not to exceed the throttle failure limit opening when the failure is judged.
5. The output control device for an engine according to any one of 4. 6. The engine output control device according to claim 5, wherein said throttle failure limit opening is set to a fixed small throttle opening.