JP3931490B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for an internal combustion engine that automatically performs idle stop, and more particularly, to a control device for an internal combustion engine that improves startability at restart and reduces shock at restart.
[0002]
[Prior art]
In recent years, in order to reduce exhaust gas, reduce carbon dioxide emissions, and reduce fuel consumption, an idle stop exercise has been performed to encourage the engine to stop while the vehicle is stopped. In addition, in order to reduce the burden of the driver's idle stop operation when the vehicle is frequently stopped due to traffic jams or traffic lights, there may be an automobile equipped with an idle stop function that automatically stops and restarts the engine by detecting the idle state. Yes.
[0003]
In an automobile having such an idle stop function, a case where an elapsed time from an engine stop to a restart is short frequently occurs. In order to improve the restartability of such an internal combustion engine, a first prior art described in JP-A-7-224712 is known. In the first conventional technique, in an internal combustion engine using an air flow meter equipped with a heating resistor as an intake air amount sensor, the heating resistor is energized before starting the engine, and the energization is continued until a predetermined time elapses after the engine is stopped. To do.
[0004]
As a technique for improving the restartability of an internal combustion engine provided with a variable valve timing mechanism, a second conventional technique described in Japanese Patent Application Laid-Open No. 8-261027 is known. In this second prior art, an auxiliary power switch that is closed when the main power switch is opened is provided, and after the main power is turned off, the idle speed control valve (ISCV) is forcibly fully opened in preparation for restart. In addition, the valve timing is set to a valve overlap period suitable for engine start.
[0005]
[Problems to be solved by the invention]
However, in the above prior art, regardless of the state in the intake manifold, the throttle opening at the time of starting is always set according to the engine temperature such as the cooling water temperature. There was a problem of shocking passengers.
[0006]
In view of the above problems, an object of the present invention is to provide a control device for an internal combustion engine that prevents sudden torque generation at the time of restart and does not shock the vehicle body and the occupant.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 automatically stops the engine when a predetermined idle condition is satisfied, and automatically restarts the engine when a predetermined restart condition is satisfied. A control device for an internal combustion engine having an idle stop function, an intake air amount control means for controlling the amount of air taken in by the engine, an in-manifold state estimation means for estimating a state in the intake manifold during idle stop, A required air amount calculating means for calculating a required air amount when the engine is restarted, and an opening degree calculating means for calculating an opening degree of the intake air amount control means according to the state in the manifold and the required air amount. The manifold state estimation means stores storage means for storing the intake manifold pressure immediately before idling stop, and stores the intake manifold pressure as an initial value. As-up duration of integration time, by integrating the intake manifold air quantity, and summarized in that with a calculating means for calculating the intake manifold internal pressure.
[0010]
According to a second aspect of the present invention, in order to achieve the above object, in the control device for an internal combustion engine according to the first aspect , the required air amount calculation means is a table stored in advance based on the outside air temperature and the engine temperature. The gist is to obtain the required air volume by indexing
[0011]
According to a third aspect of the present invention, in order to achieve the above object, in the control device for an internal combustion engine according to the first or second aspect, the intake air amount control means is an electronically controlled throttle, and the state in the manifold is estimated. The means is to calculate the total gas amount in the intake manifold by integrating the air flowing in from the electronic control throttle.
[0012]
In order to achieve the above object, according to a fourth aspect of the present invention, in the control apparatus for an internal combustion engine according to the first or second aspect, the intake air amount control means changes the intake valve opening / closing timing to perform intake. The gist of the invention is valve timing control means for controlling the amount of air.
[0013]
【The invention's effect】
According to the first aspect of the present invention, in the control device for an internal combustion engine having an idle stop function, the state in the intake manifold during idle stop estimated by the in-manifold state estimation means and the required air amount calculation means are calculated. Since the opening degree calculation means calculates the opening degree of the intake air amount control means based on the required air amount at the time of restarting the engine, the opening degree of the intake air amount control means should be optimally controlled at the time of restart Thus, it is possible to prevent a sudden torque from being generated at the time of restart and to eliminate shocks to the vehicle body and the occupant.
[0014]
Further, the manifold state estimating means includes storage means for storing the intake manifold pressure of the idling stop immediately before the the stored intake manifold pressure and an initial value, the duration of the idle stop as integration time, the intake manifold The calculation means for calculating the change in intake manifold internal pressure by integrating the amount of internal air is configured to provide a highly accurate change in intake manifold pressure as time elapses after idling stop. There is an effect that it can be calculated.
[0016]
In the invention according to claim 2 , in addition to the effect of the invention according to claim 1 , the required air amount calculation means indexes a table stored in advance based on the outside air temperature and the engine temperature. Therefore, the required air amount can be obtained in a short time without performing complicated calculations.
[0017]
In the invention according to claim 3 , in addition to the effect of the invention according to claim 1 or 2, the intake air amount control means is an electronic control throttle, and the required air amount calculation means Since the total amount of gas in the intake manifold is calculated by integrating the air flowing in from the electronically controlled throttle, the change in the intake manifold pressure can be calculated with high accuracy over time after idle stop. Can do.
[0018]
According to a fourth aspect of the present invention, in addition to the effects of the first or second aspect, the intake air amount control means controls the intake air amount by changing the opening / closing timing of the intake valve. Therefore, the present invention can be applied to an internal combustion engine that includes an electromagnetically driven intake valve or the like and opens and closes the intake valve at an arbitrary timing to control the intake air amount.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a first embodiment of a control device for an internal combustion engine according to the present invention.
[0020]
In FIG. 1, the control device 1 includes an air flow meter 2 that detects the intake air amount of the engine, a timing unit 3 that generates a timing signal at regular time intervals, and from the timing unit 3 not only during engine operation but also after engine shutdown. The intake manifold air amount calculation unit 4 that calculates the amount of air in the intake manifold according to the time signal of the above, the restart required air amount calculation unit 5 that calculates the required air amount during restart, and the throttle opening are calculated A throttle opening calculation unit 7 and an electronic control throttle 8 that is disposed downstream of the air flow meter 2 and controls the amount of intake air are provided.
[0021]
The air flow meter 2 preferably employs a method capable of measuring up to a low flow rate among various types of air flow meters, for example, a hot wire method. The measurement signal of this air flow meter is Qa.
[0022]
The time measuring unit 3 oscillates the natural frequency using a crystal resonator or the like, divides the natural frequency, and generates a time signal t having a fixed period every 1 msec, for example.
[0023]
The intake manifold air amount calculation unit 4 calculates the amount of air in the manifold that is in the intake manifold after the engine is operating and after the engine is stopped. In accordance with the time signal t of the fixed period from the time measuring unit 3, the inside of the manifold is calculated. The air flow in and out of the manifold is sequentially updated using the calculated value.
[0024]
The restart required air amount calculation unit 5 calculates an air amount necessary for restarting the engine based on the outside air temperature Ta and the coolant temperature Te as the engine temperature. This calculation may be performed according to an approximate calculation formula. However, in the present embodiment, a required air amount map 6 is provided inside the restart required air amount calculation unit 5 and two-dimensional variables of Ta and Te are used. The map is indexed to obtain the required air amount Qd.
[0025]
The throttle opening calculation unit 7 stores, for example, in advance based on the intake manifold air amount Cm calculated by the intake manifold air amount calculation unit 4 and the required air amount Qd calculated by the restart required air amount calculation unit 5. The opening degree of the electronic control throttle 8 at the time of restart is calculated with reference to the map.
[0026]
Next, the operation flow of this embodiment will be described with reference to the flowchart of FIG. The flowchart shown in FIG. 2 shows the operation for each time signal t generated by the timer 3, and the constituent elements of the control device 1 excluding the air flow meter 2 and the electronic control throttle 8 are constituted by a microcomputer or the like. You can think of it as a subroutine.
[0027]
First, it is determined whether or not an idle stop is being performed (step 10, hereinafter, step is abbreviated as S).
[0028]
Here, a supplementary explanation will be given regarding idle stop. For example, when the engine has been warmed up and the storage battery does not need to be charged, the driver releases the accelerator pedal and releases the brake pedal. This is a time when all the conditions such as the state of being stepped on, the vehicle speed becoming zero, and the gear position being N or D are satisfied. When this idle stop condition is satisfied, the control device for the internal combustion engine performs fuel injection and ignition stop to automatically stop the engine.
[0029]
Then, when the driver depresses from the brake pedal to the accelerator pedal, if the side brake is released and the gear position is N or D, the control device drives the starter motor, assuming that the restart condition is satisfied, The engine shall be automatically restarted by fuel injection and ignition.
[0030]
If it is determined in S10 that the engine is not idling, the air flow rate Qa is measured by an air flow meter (S12), and the outflow air amount Cc from the intake manifold to the cylinder is calculated (S14). Next, by adding [Qa · Δt−Cc] to the previous intake manifold air amount Cm (n−1) calculated in synchronization with the previous time signal t, the current intake manifold air amount Cm (n) is obtained. Obtain (S16) and return to the main routine. Here, Δt is the time from time n−1 to time n, that is, the interval of the time signal t generated by the time measuring unit 3.
[0031]
If it is determined in S10 that the engine is idling, it is determined whether or not a predetermined restart condition for restarting the engine is satisfied (S18). If the engine is not restarted, the air flowing into the intake manifold is determined. The amount Qa is measured (S20), and then the current intake manifold air amount is calculated by adding Qa · Δt to the previous intake manifold air amount Cm (n−1) calculated in synchronization with the previous time signal t. Cm (n) is obtained (S22), the elapsed time after the idle stop is updated (S24), and the process returns to the main routine.
[0032]
If the restart condition is satisfied in the determination of S18, the outside air temperature Ta is measured (S26), the cooling water temperature Te is measured (S28), and the required air amount Qd is calculated using Ta and Te (S30). ).
[0033]
Next, using the calculated required air amount Qd and the intake manifold air amount Cm calculated up to the previous time, the throttle opening at the time of restart is calculated (S32). Is set (S34), and the engine is started (S36).
[0034]
In this way, the state in the intake manifold can be calculated even after the engine is stopped, and the opening of the electronically controlled throttle can be controlled according to the state in the intake manifold when the engine is restarted. In addition to ensuring good restartability, excessive torque is not suddenly generated and the vehicle and passengers are not impacted.
[0035]
FIG. 3 is an explanatory diagram of an internal model of the intake system used for calculation by the intake manifold air amount calculation unit 4.
In FIG. 3, an electronic control throttle 8 is provided downstream of an air flow meter (AFM) 2 that measures the intake air amount. An intake manifold section 20 is provided downstream of the electronic control throttle 8, and a cylinder section 22 is provided via an intake valve 21.
[0036]
Let the air flow rate of the AFM part be Qa [kg / h]. The pressure in the manifold section is Pm [Pa], the volume is Vm [m ³ ], the air mass is Cm [g], and the temperature is Tm [° K]. The cylinder part pressure is Pc [Pa], the volume is Vc [m ³ ], the air mass is Cc [g], the temperature is Tc [° K], and the fresh air ratio in the cylinder is η.
[0037]
The amount of air Cm (n) in the intake manifold is expressed by the following equation (1).
[Expression 1]
Cm (n) = Cm (n−1) + Qa (n) · Δt−Cc (n) (1)
Here, Qa (n) · Δt is an inflow air amount to the manifold, and Cc (n) is an outflow air amount from the manifold.
[0038]
Further, assuming that the gas constant is R, the engine speed is Ne, the manifold part temperature = cylinder part temperature (Pm = Pc), and the manifold part pressure = cylinder part pressure (Tm = Tc), Cc is the following formula ( 2).
[Expression 2]
Cc = η · Pm · Vc / (R · Tm) / Ne (2)
FIG. 4 is a signal diagram showing the calculation content of the air quantity in the intake manifold shown by the equation (1).
The input signals are the air flow rate Qa of the AFM section, the approximate air flow rate value QH0, the engine speed Ne, and the cylinder volume Vc. The output signal is a manifold part air amount Cm.
[0039]
The approximate air flow rate value QH0 is an approximate value of the intake air flow rate obtained from the engine speed Ne and the throttle opening (not shown), and a Ktrm map, which is a correction coefficient map, is indexed by QH0 and Ne to obtain Ktrm. An accurate air flow rate is obtained by multiplying the air flow rate measured by the AFM unit by Ktrm. It is known that the characteristics of the hot-wire air flowmeter used here fluctuate due to intake pulsation, and in order to obtain a flat open-loop air-fuel ratio control characteristic as much as possible, the measured value is corrected by Ktrm. It is carried out.
[0040]
Next, after changing the unit of Qa, the interval integration of 1 msec is performed to obtain the inflow air amount Ca to the manifold.
On the other hand, the outflow air amount Cc from the manifold is obtained by multiplying the cylinder volume Vc by the cylinder pressure Pc = Pm. Then, when Cc is subtracted from the sum of Cm (n−1) and Ca = Qa (n) · Δt, an updated manifold air amount Cm (n) is obtained.
[0041]
FIG. 5 shows the throttle opening during restart with respect to the time from engine stop to restart in the present embodiment.
For example, as shown in FIG. 5A, if the intake manifold internal pressure is −200 mmHg or more when the engine is stopped, the throttle opening is 70% (0) of fully open (1.0) when restarting immediately after the stop. 7), the throttle opening at the time of restart becomes smaller as the time until the restart elapses, and at the time of restart after about 1 second, the throttle opening becomes a constant of approximately 0.5.
[0042]
Further, as shown in FIG. 5B, if the intake manifold internal pressure is −200 mmHg or less when the engine is stopped, the throttle opening is almost fully opened (1.0) at the restart immediately after the stop, and the engine is restarted. As time elapses, the throttle opening at the time of restart becomes smaller, and at the time of restart after about 3 seconds, the throttle opening becomes a constant of approximately 0.5.
[0043]
In this embodiment, the air amount in the intake manifold is calculated as the intake manifold state estimating means. However, the present invention is not limited to this, and an intake pressure sensor is provided in the intake manifold instead of the air flow meter. The air amount may be calculated from the internal pressure, and the throttle opening may be calculated based on the calculated value and the required air amount at restart.
[0044]
In this case, the intake pressure sensor value at the time of engine stop is temporarily stored as an initial value, and the air flow rate according to the difference between the atmospheric pressure that can be regarded as almost constant and the intake manifold internal pressure leaks from the throttle valve. The air amount may be integrated and calculated.
[0045]
FIG. 6 is a block diagram showing the configuration of the second embodiment of the control apparatus for an internal combustion engine according to the present invention.
In FIG. 6, the control device 101 includes an air flow meter 2 that detects the intake air amount of the engine, a timing unit 3 that generates a timing signal at regular time intervals, and a timing unit 3 that is not only during engine operation but also after engine shutdown. An intake manifold air amount calculation unit 4 for calculating the amount of air in the intake manifold according to the time signal of the above, a restart required air amount calculation unit 5 for calculating the required air amount at restart, and an electromagnetically driven intake / exhaust valve An intake / exhaust valve opening / closing timing calculation unit 10 for calculating the opening / closing timing and an electromagnetically driven intake / exhaust valve 11 are provided.
[0046]
The control device 101 of the present embodiment is applied to an internal combustion engine having an electromagnetically driven intake / exhaust valve, and is a throttle opening calculation that is a component of the first embodiment shown in FIG. Instead of the unit 7 and the electronic control throttle 8, an intake / exhaust valve opening / closing timing calculation unit 10 and an electromagnetically driven intake / exhaust valve 11 are provided. Other configurations are the same as those in the first embodiment, and the same reference numerals are given.
[0047]
In an internal combustion engine equipped with an electromagnetically driven intake / exhaust valve, the intake air amount can be controlled by controlling the opening / closing timing of the intake / exhaust valve. It is in a state.
[0048]
The operation in this embodiment is the same as that in the first embodiment, except that the intake / exhaust valve opening / closing timing is calculated instead of the throttle opening calculation.
That is, in the first embodiment, when the calculated value of the throttle valve opening is fully opened, in this embodiment, the opening / closing timing of the intake valve is opened at the timing at which the maximum intake amount is obtained, for example, near the top dead center, The timing for closing near the dead point.
[0049]
Further, when the throttle valve is throttled in the first embodiment, the intake valve is controlled to be closed early or late closed beyond the bottom dead center according to the throttle amount. By controlling the opening / closing timing of the intake valve in this way, the optimum amount of air can always be sucked into the cylinder regardless of the time from engine stop to restart, ensuring good restartability, Sudden torque generation at the time of restart is prevented, and the vehicle and the passenger are not shocked.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a control device for an internal combustion engine according to the present invention.
FIG. 2 is a flowchart for explaining the operation of the first embodiment.
FIG. 3 is an explanatory diagram of an internal model of an intake system calculated by an intake manifold air amount calculation unit;
FIG. 4 is a signal diagram showing calculation contents of an intake manifold air amount calculation unit;
FIG. 5 is a graph showing an example of a throttle opening with respect to an elapsed time after engine stop.
FIG. 6 is a block diagram showing a configuration of a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Control apparatus 2 Air flow meter 3 Timekeeping part 4 Intake manifold air amount calculating part 5 Restart required air amount calculating part 6 Required air amount map 7 Throttle opening degree calculating part 8 Electronically controlled throttle

Claims (4)

A control device for an internal combustion engine having an idle stop function that automatically stops the engine when a predetermined idle condition is satisfied, and automatically restarts the engine when a predetermined restart condition is satisfied,
Intake air amount control means for controlling the amount of air taken in by the engine;
In-manifold state estimating means for estimating the state in the intake manifold during idle stop,
A required air amount calculating means for calculating a required air amount when the engine is restarted;
An opening degree calculating means for calculating an opening degree of the intake air amount control means according to the state in the manifold and the required air amount;
With
The in-manifold state estimation means includes:
Storage means for storing the intake manifold pressure immediately before idling stop;
Calculating means for calculating the intake manifold internal pressure by integrating the intake manifold air amount with the stored intake manifold internal pressure as an initial value and the idle stop duration as an integration time; and
A control apparatus for an internal combustion engine, comprising: The required air amount calculating means includes
  2. The control apparatus for an internal combustion engine according to claim 1, wherein a required air amount is obtained by indexing a table stored in advance based on the outside air temperature and the engine temperature. The intake air amount control means is an electronically controlled throttle,
  3. The internal combustion engine according to claim 1, wherein the in-manifold state estimating means calculates the total gas amount in the intake manifold by integrating the air flowing in from the electronic control throttle. Control device. 3. The control apparatus for an internal combustion engine according to claim 1, wherein the intake air amount control means is valve timing control means for controlling the intake air amount by changing an opening / closing timing of the intake valve.

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