JP2001132507A - Control device for internal combustion engine and vehicle equipped with the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine to improve exhaust performance at starting in an internal combustion engine equipped with an adjustable valve mechanism, and to provide a vehicle equipped with the device. SOLUTION: The overlapping of intake and exhaust valves is set to exceed the prescribed valve at a cold starting by an adjustable valve mechanism, and the internal combustion engine is rotated with the number of idle rotations by a start motor. Fuel is supplied after the negative pressure in a combustion chamber reaches prescribed negative pressure. This action enables to prevent fuel from sticking on the well surface of a fuel chamber and to improve exhaust performance.

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 control device for an internal combustion engine having a variable valve mechanism and a starting motor, and a vehicle equipped with the control device.

[0002]

2. Description of the Related Art There is known an internal combustion engine having a variable valve mechanism for variably controlling the opening / closing timing of intake and exhaust valves in accordance with operating conditions in order to improve fuel efficiency and exhaust performance.

A technique disclosed in Japanese Patent Application Laid-Open No. 9-195840 discloses a fuel injection control device for an internal combustion engine having such a variable valve mechanism when the valve timing of an intake / exhaust valve reaches a valve timing at startup. This permits fuel injection.

More specifically, when the internal combustion engine is stopped due to an engine stall or the like in a state in which the advance value of the intake valve is large and the valve overlap is large with both the intake and exhaust valves open, the valve overflow occurs. The fuel is injected after setting the intake angle of the intake valve having a small lap to a small value. It is described that by this, it is possible to prevent fuel from excessively blowing through to the exhaust side at the time of restart, and to improve the discharge performance.

[0005]

However, according to this technique, the advance angle is delayed and the internal combustion engine is restarted in a state where the advance value is small, so that the negative pressure of the combustion chamber at the time of restart is reduced. As a result, the fuel may adhere to the wall surface of the combustion chamber, so that the exhaust performance may be reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a control device for an internal combustion engine equipped with a variable valve mechanism, which improves emission performance at the time of starting, and a vehicle equipped with the control device. That is the task.

[0007]

In order to achieve the above object, a control device for an internal combustion engine according to the present invention comprises a variable valve mechanism for variably controlling the opening / closing timing of intake and exhaust valves, and is capable of being driven at idle speed or higher. A control device for an internal combustion engine having a simple starting motor, wherein at the time of a cold start, the overlap of the intake and exhaust valves is set to a predetermined value or more by a variable valve operating mechanism,
The internal combustion engine is rotated by the start motor at a rotation speed near the idle rotation speed, and thereafter, control is performed to start fuel supply after determining that the negative pressure in the combustion chamber of the internal combustion engine has reached a predetermined negative pressure.

According to the present invention, the overlap of the intake and exhaust valves is set to a predetermined value or more by the variable valve operating mechanism, and the internal combustion engine is rotated at the idle speed by the starting motor before the fuel is supplied. Can be driven like a vacuum pump to increase the negative pressure in the combustion chamber. By starting fuel supply and starting the internal combustion engine after reaching a predetermined negative pressure, it is possible to secure a sufficient negative pressure for driving the internal combustion engine, and to prevent the fuel from adhering to the inner wall surface of the combustion chamber. In addition, the fuel can be stably burned, and the emission performance is improved. This is particularly effective at the time of a cold start in which the performance of the exhaust catalyst is reduced.

This internal combustion engine is provided with an electronically controlled throttle. At the time of a cold start, the throttle opening is adjusted to be closer to the closed side than before the start of fuel supply, and the throttle opening is returned to the normal state after the start of fuel supply. It is preferred to do so.
By adjusting the throttle opening to the closed side when the pump is driven, the negative pressure of the combustion chamber can be increased to a predetermined value more quickly.

A determination as to whether or not the negative pressure of the combustion chamber has reached a predetermined value is further provided with a negative pressure sensor for detecting a negative pressure of the combustion chamber or the intake pipe, based on the detected value of the negative pressure sensor. Is preferred. Alternatively, the variable valve mechanism has an open / closed state sensor for detecting the open / closed state of the intake / exhaust valve, and a predetermined time has elapsed since the open / closed state of the intake / exhaust valve detected by the open / closed state sensor has reached a predetermined state. In such a case, control may be performed by determining that the predetermined negative pressure has been reached. This is because the negative pressure in the combustion chamber can be made a sufficient negative pressure by continuing the above-described pump drive for a predetermined time after the predetermined intake / exhaust valve overlap is achieved. Alternatively, after setting the overlap of the intake and exhaust valves by the variable valve mechanism to a predetermined value or more, when a predetermined time has elapsed, it may be determined that a predetermined negative pressure has been reached and control may be performed. There is a time lag between the time when the control device instructs the variable valve mechanism to change the opening / closing timing and the time when the opening / closing timing of the intake / exhaust valve is actually changed, but the time lag is usually predictable. , The negative pressure can be predicted.

According to the present invention, it may take one to several seconds for the internal combustion engine to start during a cold start. Therefore, the vehicle equipped with the control device for an internal combustion engine according to the present invention has another drive source capable of driving the vehicle together with the internal combustion engine, and the other drive sources are provided until fuel supply to the internal combustion engine is started. It is preferable that the vehicle is driven by the drive source.

[0012]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In order to facilitate understanding of the description, the same constituent elements are denoted by the same reference numerals as much as possible in each drawing, and redundant description will be omitted.

FIG. 1 is a configuration diagram of a main part of a hybrid vehicle provided with a control device for an internal combustion engine according to the present invention.
The hybrid vehicle is driven by receiving fuel from a fuel tank (not shown).
1, the output shaft of which is connected to a power split mechanism 2 using a planetary gear or the like. The power split device 2 is connected to a generator (generator) 3 and a motor (electric motor) 4, and the driving force of the engine 1 is transmitted to the generator 3, the motor 4, or both by the power split device 2. It has a configuration. Drive wheels 6 of the vehicle are connected to the rotation shaft of the motor 4 via a speed reducer 5. The generator 3 and the motor 4 are electrically connected to a storage battery 8 via an inverter 7. The hybrid vehicle includes an engine control unit (ECU) 9 for controlling the drive system.

Next, a detailed configuration of the engine 1 will be described. An intake pipe 10 connected to the engine 1 has an electronically controlled throttle 11 whose opening is controlled by the ECU 9 from the atmosphere side, a negative pressure sensor 12 for detecting a negative pressure in the intake pipe 10, and an injector 13 for supplying fuel. Is placed,
The intake valve 14 is reached. The intake valve 14 is driven by a cam 15.
9 is connected to a variable valve timing mechanism (VVT) 16 for adjusting the opening / closing timing of the intake valve 14 in accordance with the instruction. The cam 15 is provided with a cam position sensor 17. As the VVT 16, for example, the VVT disclosed in Japanese Patent Application Laid-Open No. 10-227236 can be used. FIG. 2 is a diagram for explaining the operation of the VVT 16. By adjusting the timing at which the intake valve 14 opens (valve lift), the length of the valve overlap where both the intake valve 14 and the exhaust valve 31 are open is adjusted. Hereinafter, the case where the intake valve 14 is opened earlier than before adjustment to extend the valve overlap (corresponding to shifting the valve lift curve of the intake valve 14 to the left in the figure)
Is referred to as being advanced, and conversely, when the valve is opened later than before adjustment to shorten the valve overlap (corresponding to shifting the valve lift curve of the intake valve 14 to the right in the figure), it is referred to as adjusting to the retarded side. .

An ignition plug 21 is arranged in the combustion chamber 20. The reciprocating motion of the piston 23 in the cylinder 22 is transmitted to the above-described power split device 2 via the connecting rod 24 and the crankshaft 26. A water temperature sensor 24 for detecting a cooling water temperature is attached to a crankcase constituting the cylinder 22.

An exhaust valve 31 is provided on the exhaust side of the combustion chamber 20.
The exhaust pipe 30 is connected to the end of the
2 driven configuration.

In such a hybrid vehicle, the distribution of the driving force is changed by the power split device 2 so that
Efficient operation becomes possible. Specifically, engine 1
Is efficient in the high-speed rotation range, and the motor 4 is efficient in the low-speed rotation range.
During normal driving, the generator 3 is driven by a part of the driving force of the engine 1, the driving power is assisted by the motor 4 using the generated power, and the storage battery 8 is used.
Charge. When the load is high, power is supplied from the storage battery 8 to increase the assisting force of the motor 4. At the time of braking, the motor 4 is driven by the drive wheels 6 to generate power, thereby recovering kinetic energy as electric power.

Next, the operation at the time of starting will be described. The control device for an internal combustion engine according to the present invention has solved the above-mentioned problem, and is characterized by the operation at the time of starting. FIG. 3 is a flowchart at the time of starting, and FIG. 4 is a graph showing transitions of the intake valve advance angle, the intake pipe negative pressure, and the engine speed at the time of starting. In the following operation, the ECU 9 controls the operation of each component unless otherwise specified.

First, in step S1, the power split mechanism 2
Is adjusted, the generator 3 and the engine 1 are connected, and
The inverter 7 is controlled by the power stored in the storage battery 8.
To rotate the generator 3 to reduce the speed of the engine 1
Increase engine speed to about 1300rpm and start engine 1.
You. Then, the advance angle of the intake valve 14 is set to 25 °.
Generates a lead angle setting signal. This allows valve overlap
Is set longer. Actual advance value of intake valve 14
Is Δt from the setting signal as shown by the thin broken line in FIG. _a(Figure
4 about 1 second).

In step S2, it is determined whether or not the engine is a cold start. Specifically, when the cooling water temperature detected by the water temperature sensor 24 is −10 ° C. to 70 ° C., or when the catalyst simulated temperature, which is a predicted value obtained by calculating the temperature of the exhaust purification catalyst, is less than 500 ° C., If it is determined that the engine has started, the process proceeds to step S3, in which the cooling water temperature is 70 ° C. or more or the catalyst simulation temperature is 5
If the temperature is equal to or higher than 00 ° C., the subsequent processing is skipped and fuel is injected from the injector 13 and the combustion chamber 2
The combustion within 0 is started, and the operation of the engine 1 is started.

If it is determined that the start is a cold start, in step S3, the throttle opening is closed (for example, the throttle opening is 5 °) from the time of normal startup (for example, the throttle opening is 5 °). 2 °). Thereby, the pressure between the intake pipe 10 and the combustion chamber 20 decreases, and the negative pressure, which is a difference from the atmospheric pressure, increases as shown in FIG. 4 (the absolute value of the negative pressure having a negative value increases). Become).

In step S4, it is detected whether the cranking time is within a predetermined time. Specifically, by monitoring the output of the cam position sensor 16, when the delay (Delta] t _a) is equal to or more than 5 seconds for the setting signal, it is determined that the VVT failure or the like occurs, skip subsequent processing , Start fuel injection. Otherwise, the process proceeds to step S5.

In step S5, a cam position sensor
16 is monitored and the progress calculated from the detected cam position is
The angle value is a predetermined threshold θ_th(In this case, 20 °)
Predetermined time Δt_b(500 ms here)
The process moves to step S6, otherwise, step S6
Return to 4. Lead angle is θ_thTime Δt after exceeding _b
After the passage of time, the intake pipe negative pressure causes the fuel to adhere to the combustion chamber wall.
Enough negative pressure P to completely burn without_th(About -7
0 kPa). Step S after reaching this point
As shown in FIG. 6, fuel is injected from the injector 13
Then, the operation of the engine 1 is started. Departure
According to Ming, NMHC (non-methane hydrocarbon; Non Methan)
 Hydrocarbon) emissions measured in LA-4 mode
From 7.5 mg / km (0.012 g / mile) to 6.
About 20% to 2mg / km (0.010g / mile)
Could be reduced.

The time t ₁ until the engine 1 is driven is:
As shown in FIG. 4, it takes 2 to 3 seconds. Therefore, it is preferable to drive the vehicle by the motor 4 during this time.

After the start, the electronic control throttle 11 is adjusted so as to obtain an optimum air-fuel ratio. At this time, it is preferable to slowly return the engine 1 over a period of one or two seconds, because the fluctuation of the combustion state of the engine 1 can be suppressed and the engine 1 can be started smoothly.

In the above description, the cam position sensor 1
Although it has been determined from the output of 7 whether the engine negative pressure has reached a sufficient _Pth , it is of course possible to determine from whether the value of the negative pressure sensor 12 has reached a threshold value _Pth . Alternatively, to simplify the apparatus, at the time that has passed since emit advance angle setting signal value predetermined time may be determined to have reached the P _th.

In this embodiment, the case where the engine is started by the generator in the parallel series type hybrid vehicle has been described as an example. However, the engine may be started by a motor. In addition, the present invention is applicable not only to a parallel-type or series-type hybrid vehicle, but also to an ordinary vehicle having a starting motor capable of driving an engine at an idle speed or higher.

[0028]

As described above, according to the present invention, at the time of cold start, the overlap of the intake and exhaust valves is set to a predetermined value or more by the variable valve operating mechanism, and the internal combustion engine is rotated at the idle speed by the start motor. At least, by supplying the fuel after the negative pressure in the combustion chamber reaches the predetermined negative pressure, it is possible to prevent the fuel from adhering to the wall surface of the fuel chamber and improve the discharge performance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a hybrid vehicle including a control device for an internal combustion engine according to the present invention.

FIG. 2 is a diagram illustrating a variable valve timing mechanism.

FIG. 3 is a flowchart showing the operation of the control device for an internal combustion engine according to the present invention.

FIG. 4 is a graph showing changes in the engine speed, intake pipe negative pressure, and intake valve advance angle at the time of starting.

[Explanation of symbols]

1 ... engine, 2 ... power split mechanism, 3 ... generator,
4 ... motor, 5 ... reducer, 6 ... drive wheel, 7 ... inverter, 8 ... rechargeable battery, 9 ... ECU, 10 ... intake pipe, 11 ... electronic control throttle, 13 ... injector, 14 ... intake valve, 17 ... VVT, 20: combustion chamber, 24: water temperature sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 29/02 F02D 29/02 D 321 321B 43/00 301 43/00 301J 301Z 301K 45/00 364 45 / 00 364D F-term (reference) 3G084 BA00 BA03 BA05 BA23 BA28 CA01 CA03 EA07 EA11 EC01 FA00 FA11 3G092 AA01 AA05 AA11 AC02 BB06 DA01 DA08 DA12 DC03 EA02 EA08 EA09 EA12 EA15 EA17 FA18 A03 HA01 HA13A01 HA13A13 BA20 BA21 CA01 DA03 DA05 DB23 EA05 EA09 EA15 EC01 3G301 HA01 HA19 JA21 KA01 KA07 LA00 LA01 LA07 LC03 MA18 NE19 NE23 PA07Z PE10Z

Claims (6)

[Claims] 1. A control device for an internal combustion engine having a variable valve mechanism and a starting motor, wherein at the time of a cold start, the variable valve mechanism sets an overlap of intake and exhaust valves to a predetermined value or more. The internal combustion engine is controlled by the start motor to rotate at substantially the idle speed of the internal combustion engine, and thereafter, controls to start fuel supply after it is determined that the negative pressure in the combustion chamber of the internal combustion engine has reached a predetermined negative pressure. Engine control device. 2. The internal combustion engine has an electronically controlled throttle. During a cold start, the throttle opening is adjusted to be closer to the closed side than at least until the start of fuel supply, and after a predetermined time after the start of fuel supply. 2. The control device for an internal combustion engine according to claim 1, wherein control is performed to return the throttle opening to normal. 3. The internal combustion engine has a negative pressure sensor for detecting a negative pressure in a combustion chamber or an intake pipe, and determines whether or not the negative pressure in the combustion chamber has reached the predetermined negative pressure. 3. The control device for an internal combustion engine according to claim 1, wherein the determination is performed based on a value detected by the sensor. 4. The variable valve mechanism has an open / closed state sensor for detecting an open / closed state of an intake / exhaust valve, and determines whether a negative pressure in the combustion chamber has reached the predetermined negative pressure. 3. The internal combustion engine according to claim 1, wherein when the opening / closing state of the intake / exhaust valve detected by the sensor reaches a predetermined state and a predetermined time has elapsed, it is determined that the predetermined negative pressure has been reached and control is performed. Control device. 5. A method according to claim 1, wherein a predetermined time has passed since the overlap of said intake and exhaust valves by said variable valve mechanism was set to be equal to or more than said predetermined value, whether or not the negative pressure in said combustion chamber reached said predetermined negative pressure. 3. The control device for an internal combustion engine according to claim 1, wherein the control is performed by determining that the predetermined negative pressure has been reached in such a case. 6. A vehicle equipped with the control device for an internal combustion engine according to claim 1, further comprising another drive source capable of driving the vehicle together with the internal combustion engine. A vehicle driven by the other drive source until fuel supply of the vehicle is started.