JP4063194B2 - Idle speed control device for internal combustion engine - Google Patents

Description

  The present invention relates to an idle speed control of an internal combustion engine provided with a lift / operating angle variable mechanism capable of variably controlling a lift operating angle that is at least one of a valve lift amount and an operating angle of an intake valve, and a so-called electronically controlled throttle valve. More particularly, the present invention relates to a technique for feedback control of the idling speed toward a target value by controlling the opening of a throttle valve.

  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 for early intake air closing control, that is, mirror cycle operation, by controlling the intake air amount without depending on the throttle valve by changing the valve lift amount of the intake valve. By using this technique, 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.

As a similar technique, in Patent Document 1, in an intake control device for an internal combustion engine that controls early closing of intake by an intake control valve provided in an intake passage, a throttle opening is set to be larger during intake early closing control. A technique for performing control based on a non-linear map is disclosed.
JP-A-8-189394

  As described above, when the intake air amount is controlled by variable control of the valve lift characteristic of the intake valve as a so-called throttleless, the intake air amount to be controlled becomes very small in the extremely low load region including the idle. Stable intake air amount control based only on characteristics becomes difficult. 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.

  For this reason, a so-called electronically controlled throttle valve is provided and combined with variable control of the valve lift characteristics of the intake valve and opening degree control of the throttle valve, it is possible to realize a substantially throttleless operating state in most operating regions. Although the applicant has studied, in such a case, even in the same idling operation state, the throttle opening varies depending on the situation, and the mode of flow (velocity / flow rate) passing through the throttle valve may vary. . Therefore, depending on the opening degree of the throttle valve, the characteristics and sensitivity of the flow rate change with respect to the opening degree change of the throttle valve will be different. For this reason, the feedback control for controlling the idling speed toward the target value by the opening control of the throttle valve is not properly performed, that is, the behavior varies depending on the opening of the throttle valve, so that the control stability and reliability It becomes inferior.

  The present invention has been made in view of such a problem, and even when the opening of the throttle valve at an idle is different, the feedback control of the idle rotation speed by the throttle opening control can be stably performed. The main object is to provide a novel idle speed control device for an internal combustion engine.

At least one of the valve lift and the duration of the intake valve and the continuously variable controllable lift operating angle variable mechanism,
A collector to which intake passages of a plurality of cylinders are connected;
A throttle valve located upstream of the collector and controlled in opening by a control signal;
Feedback control means for controlling the idling speed toward the target value by controlling the opening of the throttle valve;
Feedback correction means for correcting the gain of the feedback control according to the valve lift amount or the operating angle ;
Have
The feedback correction means includes
When the valve lift amount or the operating angle is larger than the first threshold value, the gain is fixed to the minimum value,
When the valve lift amount or the operating angle is smaller than the second threshold value, the gain is fixed to the maximum value,
When the valve lift amount or operating angle is smaller than the first threshold value and larger than the second threshold value, the gain is decreased as the valve lift amount or operating angle increases.

  According to the present invention, since the idle speed is feedback-controlled toward the target value by controlling the opening degree of the throttle valve, and the gain of this feedback control is corrected according to the lift operating angle, the throttle valve opening is controlled. Regardless of the degree, the response / sensitivity of the intake air amount change with respect to the throttle opening change in the feedback control can be made uniform and leveled, and the accuracy and stability of the idle speed control are remarkably improved.

  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. The variable valve mechanism 2 includes a lift / operating angle variable mechanism 51 that changes a lift operating angle, which is a valve lift amount and an operating angle (opening / closing period) of an intake valve, and a phase of a center angle of the lift (a crank (not shown)). And a phase variable mechanism 71 for advancing or retarding the phase relative to the shaft.

  First, the lift / operating angle variable mechanism 51 will be described. The lift / operating angle variable mechanism 51 has been previously proposed by the applicant of the present application. However, since it is 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 with the change in the lift operating angle.

  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. The lift / operating angle variable mechanism 51 and the phase variable mechanism 71 are closed-loop controlled based on detection by the sensors 64 and 66.

  In the present embodiment, the valve lift characteristics of the variable valve mechanism 2, in particular, the variable control of the valve lift amount and operating angle (lift operating angle) of the intake valve by the lift / operating angle variable mechanism 51, and the opening control of the throttle valve 18. Is combined to control the amount of intake air flowing into the combustion chamber (intake amount control means). Further, in the idling range, feedback control is performed so as to maintain the idling speed (engine speed) detected by the crank angle sensor 21 in the vicinity of the target value by controlling the opening degree of the throttle valve 18. (Feedback control means). As is well known, this feedback control is so-called proportional integral (PI) control using a proportional component (P component) and an integral component (I component). The target value is changed / calculated according to a required load based on input signals from auxiliary machines and various sensors. These controls are stored and executed by the engine control unit 19.

  In this embodiment, the lift operating angle and the throttle opening are increased or decreased depending on the situation even in the same idle range. Note that the lift operating angle and the throttle opening are adjusted in relation to each other, and for the same required load and intake air amount, the throttle opening decreases as the lift operating angle increases, and the throttle opens when the lift operating angle decreases. There is a relationship of increasing degrees.

3 and 4 show two typical idle operation modes. As shown in FIG. 3, in terms of improving fuel efficiency, it is preferable to set the first idle operation mode in which the lift operating angle is reduced and the throttle opening is increased. Specifically, the valve lift amount is maintained in a minimal lift state of, for example, 1 mm or less, and is increased to a certain extent (for example, several degrees or more).

  However, if the lift of the intake valve 3 is controlled to a minimum, the intake amount of each cylinder and thus the air-fuel ratio is likely to change greatly due to slight variations. Accordingly, when the lift operating angle is minimized, such as when the engine is cold, when the oil / water temperature is low, or when the lift / operating angle variable mechanism 51 is fixed on the large lift side, the intake amount can be stably obtained. In a situation where this is not possible, as shown in FIG. 4, the lift operating angle is made relatively large, and the second idle operation mode in which the throttle opening is small, that is, near the fully closed state, is set. For example, the valve lift amount is maintained at a large operating angle state of 10 mm or more and the operating angle is 240 CA (crank angle) or more, and the throttle valve is in the vicinity of full closing. Note that the above-described fixation of the lift / operating angle variable mechanism 51 can be estimated and detected based on, for example, a detection signal of the control axis sensor 64.

As described above, by controlling the lift operating angle and the throttle opening in combination even in the same idling range according to the situation, it is possible to improve the fuel efficiency while stably performing the intake air amount control according to the required load. it can. However, since the lift operating angle and the throttle opening are different even in the same idling range, the response and sensitivity of the intake flow rate change to the opening change of the throttle valve 18 are different. For example, in a situation where the throttle opening is extremely small as in the second idle operation mode, the flow velocity near the throttle valve 18 becomes very fast near or above the sonic speed. In the first idle operation mode in which the responsiveness / sensitivity of the change is high and the throttle opening is relatively large, the flow velocity in the vicinity of the throttle valve 18 is slower than the speed of sound, and the flow rate changes with respect to the change in the throttle valve opening. Responsiveness and sensitivity are low.

  In this embodiment, therefore, the gain of the feedback control of the idle speed using the throttle opening control is corrected according to the lift operating angle (feedback correction means). This gain is a control factor related to feedback control, and corresponds to the response and sensitivity of the flow rate change with respect to the throttle opening change. That is, the sensitivity of the flow rate change with respect to the throttle opening change increases as the gain increases, and the sensitivity of the flow rate change with respect to the throttle opening change decreases as the gain decreases. Therefore, when the lift operating angle is large, the gain is reduced, and when the lift operating angle is small, the gain is increased.

  Such a control flow will be described with reference to FIG. In S (step) 1, it is determined whether or not the engine is in an idle operation state. For example, it is determined whether a known idle SW is ON. When it is in the idling operation state, the process proceeds to S2, and the idling speed control process is executed. That is, as described above, the intake air amount is adjusted by combining the lift operating angle and the throttle opening, and a preset and stored table as shown in FIG. 6 is referred to according to the lift operating angle at that time. Thus, the integral part (I part) corresponding to the gain of the feedback control of the idle speed is corrected. Feedback control is performed using the corrected integral.

  As shown in FIG. 6, when the operating angle is larger than the first threshold value α1, that is, when the flow velocity in the vicinity of the throttle valve is equal to or higher than the sound speed, the integral amount of the feedback control is fixed to the minimum value. In a situation where the operating angle is smaller than the second threshold value α2 (α2 <α1), the integral amount of the feedback control is fixed to the maximum value. In a situation where the operating angle is smaller than the first threshold value α1 and larger than the second threshold value α2, the integral is reduced in proportion to the operating angle so that the integral becomes smaller as the operating angle becomes larger.

  According to the present embodiment as described above, in the situation where the idling speed is feedback-controlled toward the target value by controlling the throttle opening, the integral amount that is the gain of the feedback control is calculated according to the lift operating angle. Since the correction is made, the response and sensitivity of the intake air amount change to the throttle opening change in this feedback control can be made uniform and leveled regardless of the opening of the throttle valve. Therefore, even when the opening degree of the throttle valve varies depending on the situation even in the same idling range, the idling speed feedback control can be stably performed. Therefore, for example, even when the target value of the idle speed increases or decreases according to the required load, the idle speed is favorably feedback-controlled toward the target value, and stable idle speed control can be performed.

  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 integral is corrected as the gain of the feedback control, but the proportional component may be corrected alone or in combination. Further, in the idle operation region, the above-described first and second idle operation modes may be switched and used, or both the lift operating angle and the throttle opening are continuously changed in accordance with the oil water temperature or the like. You may make it adjust.

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. Explanatory drawing which shows 1st idle operation mode. Explanatory drawing which shows 2nd idle operation mode. The flowchart which shows the flow of control concerning a present Example. Operating angle-Table of I minutes for feedback control.

Explanation of symbols

16 ... Collector 18 ... Throttle valve 19 ... Engine control unit 51 ... Lift / operating angle variable mechanism

Claims (7)

At least one of the valve lift and the duration of the intake valve and the continuously variable controllable lift operating angle variable mechanism,
A collector to which intake passages of a plurality of cylinders are connected;
A throttle valve located upstream of the collector and controlled in opening by a control signal;
Feedback control means for controlling the idling speed toward the target value by controlling the opening of the throttle valve;
Feedback correction means for correcting the gain of the feedback control according to the valve lift amount or the operating angle ;
Have
The feedback correction means includes
When the valve lift amount or the operating angle is larger than the first threshold value, the gain is fixed to the minimum value,
When the valve lift amount or the operating angle is smaller than the second threshold value, the gain is fixed to the maximum value,
When the valve lift amount or operating angle is smaller than the first threshold value and larger than the second threshold value, the gain is decreased as the valve lift amount or operating angle increases.
An idle speed control device for an internal combustion engine. 2. The throttle valve according to claim 1, wherein when the valve lift amount or the operating angle is greater than a first threshold value, the opening of the throttle valve is minimized, and the flow velocity in the vicinity of the throttle valve is close to or higher than the speed of sound. Idling engine speed control device for internal combustion engine. The valve lift amount when less than the second threshold value, idle speed control apparatus for an internal combustion engine according to claim 1 or 2 the amount of valve lift is 1mm or less.   The idle speed control device for an internal combustion engine according to any one of claims 1 to 3, wherein the gain is a proportional component or an integral component of feedback control.   The idle speed control device for an internal combustion engine according to any one of claims 1 to 4, wherein the target value of the idle speed is calculated according to a required load. 6. An idling engine speed control device for an internal combustion engine according to claim 1, further comprising intake control means for controlling the intake air amount by combining the variable control of the valve lift or operating angle and the throttle valve opening control. .   The internal combustion engine according to any one of claims 1 to 6, wherein the throttle valve is substantially fully closed when the engine is in an idling state and when the engine is cold or when there is a malfunction including the fixed lift / operating angle variable mechanism. Intake control device.

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