JP4020065B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device that controls the amount of intake air and the ignition timing taken into a cylinder of an internal combustion engine, and more particularly, variable control of valve timing (valve lift characteristics) of an intake valve and opening control of a so-called electronically controlled throttle valve. And a control device for an internal combustion engine that controls the intake air amount in combination.

In a gasoline engine, the intake air amount is generally controlled by controlling the opening of a throttle valve provided in the intake passage. As is well known, this type of system has a particularly small throttle valve opening. There is a problem that the pumping loss is large at low load. On the other hand, attempts have been made to control the intake air amount without depending on the throttle valve by changing the opening / closing timing (especially the closing time) of the intake valve and the lift amount. Thus, it has been proposed to realize a so-called throttle-less configuration in which an intake system is not equipped with a throttle valve as in a diesel engine. For example, in Patent Document 1, the intake air amount is controlled using the valve timing of the intake valve, and in order to activate the catalyst early in the cold state, the opening timing of the intake valve is retarded to retard the ignition timing. A technique for expanding the above is disclosed.
JP2002-235567

  By the way, in a low-speed and low-load region including idle, the responsive ignition timing is set in advance to the retarded angle side relative to the optimal ignition timing MBT (Minimum Spark Advance for Bset Torque), and the required load is increased by auxiliary equipment. In the case of a sudden increase, the ignition timing is advanced immediately so that the fuel injection amount can be increased in accordance with the required load without causing misfire or the like. That is, the ignition timing is retarded in advance from the MBT as a kind of safety margin.

  When the intake air amount is controlled by the throttle valve, since the intake volume of the collector, intake manifold, etc. downstream of the throttle valve is large, the response of the intake air amount change to the change in the throttle valve opening is low, and the above-mentioned ignition timing from the MBT is low. It is necessary to ensure a relatively large retardation amount. Thus, when the retard amount of the ignition timing is increased, the driving point is naturally moved away from the best fuel consumption line, and the fuel consumption performance is lowered.

  On the other hand, when the intake air amount is controlled by the valve timing of the intake valve, the intake air flowing into the combustion chamber can be directly adjusted regardless of the intake air volume downstream of the throttle valve. The responsiveness is remarkably good, and therefore the retard amount of the ignition timing as a safety margin can be suppressed low.

  However, in the low-speed and low-load range including idle, the amount of intake air to be controlled is very small, so the response of the actuator of the variable valve mechanism cannot be ensured due to conditions such as oil temperature and motor temperature, In the case of malfunction such as sticking of the valve mechanism, it may be difficult to stably perform intake air amount control depending on the valve timing of the intake valve. Also, if no negative pressure is generated in the intake system because it is completely throttleless, for example, an existing system that recirculates blow-by gas or purge gas from an evaporator to the intake system cannot be used, or as a drive source for various actuators, etc. However, a new problem arises that the negative pressure that is also used cannot be easily obtained.

  The present invention has been made in view of such problems, and is capable of improving fuel efficiency while ensuring responsiveness and combustion stability with respect to a sudden increase in required load in an operation region including an idle. The main object is to provide a control device for an internal combustion engine.

  A variable valve mechanism capable of variably controlling the valve timing of the intake valve, a collector to which intake passages of a plurality of cylinders are connected, a throttle valve that is located upstream of the collector and whose opening is controlled by a control signal, and ignition Ignition timing control means for controlling the timing. In a predetermined operation region including idle, a first intake control mode in which the intake amount is controlled mainly by the valve timing of the intake valve, and a second intake control mode in which the intake amount is controlled mainly by the opening of the throttle valve, Switch to use. The ignition timing retard amount with respect to the optimal ignition timing is set smaller in the first intake control mode than in the second intake control mode.

According to the present invention, in a predetermined operating region including idling, primarily by using the first intake control mode for controlling the amount of intake air by the valve timing of the intake valve, the retard amount of the ignition timing against the optimum ignition timing In a situation where it is possible to obtain a fuel consumption performance improvement effect by suppressing it to a low level and it is difficult to use the first intake control mode, such as during cold idling, the intake air amount is mainly controlled by the opening of the throttle valve. By using the second intake control mode, the desired responsiveness and combustion stability can be stably secured. That is, the fuel efficiency improvement effect can be obtained while ensuring the desired response and combustion stability in the operation region including the idle.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment in which the present invention is applied to a V-type 6-cylinder gasoline engine 1, and variable valve mechanisms 2 (to be described later) are provided on the intake valve 3 side of the left and right banks, respectively. The valve operating mechanism on the exhaust valve 4 side is a direct acting type that drives the exhaust valve 4 by the exhaust camshaft 5, and its valve lift characteristic is always constant.

  The exhaust manifolds 6 in the left and right banks are connected to a catalytic converter 7, and an air-fuel ratio sensor 8 that detects an exhaust air-fuel ratio is provided at an upstream position of the catalytic converter 7. The exhaust passages 9 of the left and right banks merge on the downstream side of the catalytic converter 7, and further include a second catalytic converter 10 and a silencer 11 on the downstream side.

  A branch passage 15 is connected to the intake port of each cylinder, and the upstream ends of the six branch passages 15 are connected to the collectors 16 respectively. An intake inlet passage 17 is connected to one end of the collector 16, and an electronically controlled throttle valve 18 is provided in the intake inlet passage 17. The electronically controlled throttle valve 18 includes an actuator composed of an electric motor, and its opening degree is controlled by a control signal supplied from an engine control unit 19. Note that a sensor (not shown) that detects the actual opening of the throttle valve 18 is integrally provided, and the throttle valve opening is closed-loop controlled to the target opening based on the detection signal. An air flow meter 25 for detecting the intake air flow rate is disposed upstream of the throttle valve 18, and an air cleaner 20 is provided further upstream.

  In order to detect the engine speed and the crank angle position, a crank angle sensor 21 is provided for the crankshaft, and an accelerator for detecting an accelerator pedal opening (depression amount) operated by the driver. An opening sensor 22 is provided. These detection signals are input to the engine control unit 19 together with the detection signals of the air flow meter 25 and the air-fuel ratio sensor 8 described above. In the engine control unit 19, based on these detection signals, the injection amount and injection timing of the fuel injection valve 23, the ignition timing by the ignition plug 24 (ignition timing control means), the valve lift characteristics by the variable valve mechanism 2, the throttle valve The opening degree of 18 is controlled.

  Next, the configuration of the variable valve mechanism 2 on the intake valve 3 side will be described with reference to FIG. This variable valve mechanism 2 advances or retards the lift / operation angle variable mechanism 51 for changing the lift / operation angle of the intake valve and the phase of the center angle of the lift (phase with respect to a crankshaft (not shown)). The phase variable mechanism 71 is combined.

  First, the lift / operating angle variable mechanism 51 will be described. The lift / operating angle variable mechanism 1 has been previously proposed by the applicant of the present application. However, since it has been publicly known, for example, in Japanese Patent Application Laid-Open No. 2002-89303, only the outline thereof will be described.

  The lift / operating angle variable mechanism 51 includes the intake valve 3 slidably provided on the cylinder head, a drive shaft 52 rotatably supported by a cam bracket (not shown) on the cylinder head, An eccentric cam 53 fixed to the drive shaft 52 by press-fitting or the like, a control shaft 62 rotatably supported by the same cam bracket above the drive shaft 52 and disposed in parallel with the drive shaft 52, and The rocker arm 56 is swingably supported by the eccentric cam portion 68 of the control shaft 62, and the swing cam 59 is in contact with the tappet 60 disposed at the upper end portion of each intake valve 3. The eccentric cam 53 and the rocker arm 56 are linked by a link arm 54, and the rocker arm 56 and the swing cam 59 are linked by a link member 58.

  As will be described later, the drive shaft 52 is driven by a crankshaft of an engine via a timing chain or a timing belt.

  The eccentric cam 53 has a circular outer peripheral surface, the center of the outer peripheral surface is offset from the shaft center of the drive shaft 52 by a predetermined amount, and the annular portion of the link arm 54 is rotatable on the outer peripheral surface. It is mated.

  The rocker arm 56 is supported at its substantially central portion so as to be swingable by the eccentric cam portion 68, and the arm portion of the link arm 54 is linked to one end thereof via a connecting pin 55. The upper end portion of the link member 58 is linked to the end portion via a connecting pin 57. The eccentric cam portion 68 is eccentric from the axis of the control shaft 62, and accordingly, the rocking center of the rocker arm 56 changes according to the angular position of the control shaft 62.

  The swing cam 59 is rotatably supported by being fitted to the outer periphery of the drive shaft 52, and the lower end portion of the link member 58 is linked to the end portion extending laterally via a connecting pin 67. ing. On the lower surface of the swing cam 59, a base circle surface concentric with the drive shaft 52 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface come into contact with the upper surface of the tappet 60 according to the swing position of the swing cam 59.

  That is, the base circle surface is a section where the lift amount becomes 0 as a base circle section, and when the swing cam 59 swings and the cam surface contacts the tappet 60, the base circle section lifts gradually. A slight ramp section is provided between the base circle section and the lift section.

  As shown in the figure, the control shaft 62 is configured to rotate within a predetermined angle range by a lift / operation angle control actuator 63 provided at one end. The lift / operating angle control actuator 63 includes, for example, a servo motor that drives the control shaft 62 via the worm gear 65, and is controlled by a control signal from the engine control unit 19. The rotation angle of the control shaft 62 is detected by the control shaft sensor 64.

  The operation of the lift / operating angle variable mechanism 51 will be described. When the drive shaft 52 rotates, the link arm 54 moves up and down by the cam action of the eccentric cam 53, and the rocker arm 56 swings accordingly. The swing of the rocker arm 56 is transmitted to the swing cam 59 via the link member 58, and the swing cam 59 swings. The tappet 60 is pressed by the cam action of the swing cam 59, and the intake valve 3 is lifted.

  Here, when the angle of the control shaft 62 changes via the lift / operating angle control actuator 63, the initial position of the rocker arm 56 changes, and consequently, the initial swing position of the swing cam 59 changes.

  For example, if the eccentric cam portion 68 is positioned upward in the figure, the rocker arm 56 is positioned upward as a whole, and the end of the swing cam 59 on the side of the connecting pin 67 is relatively lifted upward. Become. That is, the initial position of the swing cam 59 is inclined in a direction in which the cam surface is separated from the tappet 60. Therefore, when the swing cam 59 swings with the rotation of the drive shaft 52, the base circle surface is kept in contact with the tappet 60 for a long time, and the period during which the cam surface is in contact with the tappet 60 is short. Therefore, the lift amount is reduced as a whole, and the angle range from the opening timing to the closing timing, that is, the operating angle is also reduced.

  On the contrary, if the eccentric cam portion 68 is positioned downward in the figure, the rocker arm 56 is positioned downward as a whole, and the end portion on the connecting pin 67 side of the swing cam 59 is pushed downward relatively. It becomes a state. That is, the initial position of the swing cam 59 is inclined in a direction in which the cam surface approaches the tappet 60. Therefore, when the swing cam 59 swings with the rotation of the drive shaft 52, the portion that contacts the tappet 60 immediately shifts from the base circle surface to the cam surface. Therefore, the lift amount is increased as a whole, and the operating angle is increased.

  Since the initial position of the eccentric cam portion 68 can be continuously changed, the valve lift characteristic is continuously changed accordingly. That is, the lift and the operating angle can be continuously expanded and contracted simultaneously. Depending on the layout of each part, for example, the opening timing and closing timing of the intake valve 3 change substantially symmetrically as the lift and operating angle change.

  Next, as shown in FIG. 2, the phase varying mechanism 71 has a sprocket 72 provided at the front end of the drive shaft 52, and the sprocket 72 and the drive shaft 52 are relatively moved within a predetermined angle range. And a phase control actuator 73 to be rotated. The sprocket 72 is linked to the crankshaft via a timing chain or a timing belt (not shown). The phase control actuator 73 is composed of, for example, a hydraulic or electromagnetic rotary actuator, and is controlled by a control signal from the engine control unit 19. Due to the action of the phase control actuator 73, the sprocket 72 and the drive shaft 52 rotate relatively, and the lift center angle in the valve lift is retarded. That is, the lift characteristic curve itself does not change, and the whole advances or retards. This change can also be obtained continuously. The control state of the phase variable mechanism 71 is detected by a drive shaft sensor 66 that responds to the rotational position of the drive shaft 52.

  In the present embodiment, the lift / operating angle variable mechanism 51 and the phase variable mechanism 71 are closed-loop controlled based on the detection of the sensors 64 and 66.

  In the configuration in which the variable valve mechanism 2 as described above is provided on the intake valve 3 side, the intake air amount can be basically controlled by variable control of the intake valve 3 without depending on the throttle valve 18. is there. However, in a region where the intake air amount is extremely small, such as the idle region, it is necessary to control the lift of the intake valve 3 to be very small, and due to the slight variation, the intake air amount and thus the air-fuel ratio of each cylinder greatly changes. Cheap. Therefore, in the present embodiment, in the operation region on the low speed and low load side including the idle, the valve timing (and valve lift amount) of the intake valve mainly by the variable valve mechanism 2 according to various conditions such as oil temperature and motor temperature. The first intake control mode M1 for controlling the intake amount by variable control of the intake valve and the second intake control mode M2 for controlling the intake amount by mainly controlling the opening degree of the throttle valve 18 are used by switching (intake control means) ). These controls are stored and executed by the control unit 19 described above.

  The flow of such control will be specifically described with reference to FIG. First, in S1 (step), it is determined whether or not the vehicle is in a predetermined operating range including idle. This predetermined operating range is, for example, an operating range where idle speed control (ISC) is performed, or a low speed and low load range including idling.

  If the determination in S1 is affirmative, the process proceeds to S2, and it is determined whether an operating condition that can stably perform the first intake control mode M1 is satisfied, that is, whether the intake amount can be controlled by the valve timing. This determination includes determination of the oil / water temperature of the engine, determination of the temperature of the motor as the lift / operation angle control actuator 63, determination of malfunction of the variable valve mechanism 2, and the like. For example, when the oil / water temperature is excessively low, such as during cold engine idling, or when the motor temperature is excessively high or low, the responsiveness required by the actuator of the variable valve mechanism 2 cannot be satisfied. Judgment is denied. The determination of S2 is also denied when the variable valve mechanism 2 is malfunctioning due to sticking or the like.

  If the determination at S2 is affirmative, the routine proceeds to S3, where the first intake control mode M1 in which the intake amount control is performed mainly by the valve timing of the intake valve is selected, and the ignition timing T1 is set. If S2 is negative, the routine proceeds to S4, where the second intake control mode M2 in which the intake air amount control is mainly performed by the opening of the throttle valve is selected, and the ignition timing T2 is set. These ignition timings T1 and T2 are preset and stored in the form of table data or map data in the ROM of the engine control unit 19, for example.

  In the first intake control mode M1, the throttle valve 18 is fixed and held in a fully open state or slightly closed, and the variable valve mechanism 2 controls the valve timing of the intake valve to adjust the intake amount. In a practical engine, it is preferable that a slight negative pressure exists in the intake system for recirculation of blow-by gas. Therefore, the throttle valve 18 is desirably closed slightly to generate a negative pressure in the collector 16. For example, the opening degree of the throttle valve 18 is kept substantially constant so that the pressure in the collector 16 becomes a predetermined negative pressure, that is, a minimum negative pressure necessary for a negative pressure source (for example, −50 mmHg), and is required. The intake air amount is controlled by performing closed loop control of the operating angle of the intake valve in the vicinity of, for example, 80 to 120 CA (crank angle) according to the load.

  In the second intake control mode M2, the intake air amount is controlled by performing closed loop control of the throttle valve 18 near the fully closed state while the operating angle of the intake valve is maintained at, for example, about 240 CA by the lift / operating angle variable mechanism 51. To control. In this case, the negative pressure in the collector 16 is very large, for example, -500 to -550 mmHg.

  FIG. 4 shows the ignition timing-fuel consumption characteristics in the first and second intake control modes M1, M2 in the idling operation range. As shown in the figure, in the idling operation region, the ignition timing T1 in the first intake control mode M1 is set to the advance side with respect to the ignition timing T2 in the second intake control mode M2, and The retardation amount ΔT1 of the first ignition timing T1 with respect to the optimal ignition timing MBT is set smaller than the retardation amount ΔT2 of the ignition timing T2 with respect to the optimal ignition timing MBT. Further, in any of the control modes M1 and M2, the responsiveness that can cope with the sudden increase in the required load due to the auxiliary machinery or the like is sufficiently ensured without causing deterioration in combustion stability and idling stability.

  As described above, in the predetermined operation region including the idling, the first intake control mode M1 in which the intake amount is mainly controlled by the valve timing is used, so that the retard amount from the MBT of the ignition timing is suppressed to be low. In a situation where a reduction, that is, an improvement in fuel consumption can be obtained, and it is difficult to use the first intake control mode M1 as in cold idling, the intake amount is controlled mainly by the opening of the throttle valve. By using the second intake control mode M2, it is possible to stably ensure the desired response and combustion stability. That is, the fuel efficiency improvement effect can be obtained while ensuring the desired response and combustion stability in the operation region including the idle.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes without departing from the spirit of the present invention. . For example, in the above embodiment, the present invention is applied to a V-type 6-cylinder internal combustion engine, but the present invention may be applied to other types of internal combustion engines such as an in-line 4-cylinder. In addition, the phase variable mechanism 71 on the intake valve side may be omitted, or the phase variable mechanism 71 may be provided on both the intake and exhaust sides.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows one Example of this invention. The perspective view which shows the structure of a variable valve mechanism. The flowchart which shows the flow of control of a present Example. The ignition timing-fuel-consumption characteristic figure in the 1st, 2nd intake control mode in an idle driving | operation area | region.

Explanation of symbols

2 ... Variable valve mechanism 18 ... Throttle valve 19 ... Engine control unit 51 ... Lift / operating angle variable mechanism 71 ... Phase variable mechanism

Claims (5)

A variable valve mechanism that can variably control the valve timing of the intake valve;
A collector to which intake passages of a plurality of cylinders are connected;
A throttle valve located upstream of the collector, the opening of which is controlled by a control signal;
Ignition timing control means for controlling the ignition timing;
Idle at a predetermined engine operating region were pre retarded from the optimum ignition timing, the ignition timing in order to cope with surge-containing Umate required load is a mainly first intake for controlling the intake air quantity by the valve timing of the intake valve An intake control means that switches between a control mode and a second intake control mode for controlling the intake amount mainly by the opening of the throttle valve;
An internal combustion engine in which the retard amount of the ignition timing with respect to the optimal ignition timing in the first intake control mode is set smaller than the retard amount of the ignition timing with respect to the optimal ignition timing in the second intake control mode. Control device.   2. The control device for an internal combustion engine according to claim 1, wherein the ignition timing in the first intake control mode is set to an advance side with respect to the ignition timing in the second intake control mode.   The control device for an internal combustion engine according to claim 1 or 2, wherein the intake air amount is controlled by the second intake air control mode at least during cold idling.   The variable valve mechanism includes a lift / working angle variable mechanism capable of simultaneously and continuously expanding and reducing the lift / working angle of the intake valve, and a phase variable mechanism for delaying the phase of the lift center angle of the intake valve; The control device for an internal combustion engine according to claim 1, comprising: In the first intake control mode, the operating angle of the intake valve is controlled according to the required load while holding the throttle valve near the fully open position.
5. The control device for an internal combustion engine according to claim 4, wherein in the second intake control mode, the opening of the throttle valve is controlled in the vicinity of the fully closed state according to the required load while maintaining the operating angle of the intake valve at a predetermined angle. .

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