JP4100192B2 - Variable valve operating device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable valve system that variably controls the valve lift characteristics of an intake valve of an internal combustion engine, and more particularly to a variable valve system that changes the valve lift characteristics of a plurality of cylinders simultaneously with a single actuator.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 2004-228561 has been proposed by the present applicant, and uses a variable valve device that continuously and variably controls the valve lift characteristics of an intake valve to control the intake amount of an internal combustion engine and its output. Such a configuration is disclosed. In the variable valve operating apparatus, a variable valve mechanism is provided for the intake valve of each cylinder, and one control shaft provided with an eccentric cam portion is linked to the variable valve mechanism of a plurality of cylinders to operate the actuator. Thus, when the angular position of the control shaft is changed, the valve lift characteristics of the intake valves of a plurality of cylinders are changed at the same time.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-256905 [0004]
[Problems to be solved by the invention]
In the above configuration, for example, the target valve lift characteristic changes when the operating condition changes, so that the control shaft is rotated by driving the actuator so as to achieve the target valve lift characteristic. If the actuator is driven while the intake valve of one of the cylinders is lifted, the valve lift characteristic will change during the lift, so the valve lift characteristic will be deformed and flow into the cylinder. The amount of air to be used may deviate from the expected value. In particular, if the valve lift characteristic is deformed after an appropriate amount is injected as a fuel injection amount at a certain timing and the actual intake air amount becomes excessive or insufficient, the air-fuel ratio changes, which is not preferable.
[0005]
The present invention is provided with a variable valve mechanism capable of continuously changing the valve lift characteristics in the intake valve of each cylinder, and one actuator is linked to the variable valve mechanism of a plurality of cylinders and interlocks with the operation of the actuator. Therefore, the present invention is intended for a variable valve operating apparatus for an internal combustion engine in which the valve lift characteristics of the intake valves of a plurality of cylinders change simultaneously and continuously .
[0006]
In particular, in the present invention, for example, the actuator drive speed during lift of the intake valve is reduced compared to the actuator drive speed during the period when the intake valve is not lifted, for example, by limiting the actuator drive speed based on the crank angle. It is characterized by. Specifically, the valve lift characteristic is changed on the assumption that the period including at least the lift period of the intake valve of each cylinder is the limit period, and the period outside this limit period does not include the lift period of the intake valve of any cylinder. The drive speed of the actuator at the time of making the limit is limited so as to be relatively smaller in the limit period than the actuator drive speed in a period outside the limit period. That is, when the actuator is driven from a certain control state to a different control state due to a change in operating conditions, the actuator stops or moves at a low speed while the intake valve is lifted. As a result, the valve lift characteristics are not greatly different between the initial stage and the final stage of the lift, and deformation of the valve lift characteristics is suppressed.
[0007]
【The invention's effect】
According to the present invention, the deformation of the valve lift characteristic due to the driving of the actuator during the actual valve lift is suppressed, and the amount of air sucked into the cylinder can be accurately controlled according to the intended value.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to, for example, a variable valve operating apparatus for an in-line four-cylinder internal combustion engine will be described.
[0009]
FIG. 1 is a configuration explanatory view showing the configuration of a variable valve operating device provided on the intake valve side of an internal combustion engine. This variable valve operating device is a variable lift / operating angle that changes the lift / operating angle of the intake valve. The mechanism 1 and a phase variable mechanism 21 for advancing or retarding the phase of the center angle of the lift (phase with respect to a crankshaft (not shown)) are combined.
[0010]
First, the lift / operating angle variable mechanism 1 will be described. The lift / operating angle variable mechanism 1 has been previously proposed by the applicant of the present invention. However, since it has already been publicly known, for example, from the aforementioned Japanese Patent Application Laid-Open No. 2002-256905, only the outline thereof will be described. To do.
[0011]
The variable lift / operating angle mechanism 1 includes an intake valve 11 slidably provided on a cylinder head (not shown) and a drive shaft 2 rotatably supported by a cam bracket (not shown) on the cylinder head. And an eccentric cam 3 fixed to the drive shaft 2 by press-fitting or the like, and a control shaft 12 that is rotatably supported by the same cam bracket at a position above the drive shaft 2 and arranged in parallel with the drive shaft 2. And a rocker arm 6 that is swingably supported by the eccentric cam portion 18 of the control shaft 12, and a swing cam 9 that contacts the tappet 10 disposed at the upper end of each intake valve 11. The eccentric cam 3 and the rocker arm 6 are linked by a link arm 4, and the rocker arm 6 and the swing cam 9 are linked by a link member 8.
[0012]
As will be described later, the drive shaft 2 is driven by a crankshaft of an engine via a timing chain or a timing belt.
[0013]
The eccentric cam 3 has a circular outer peripheral surface, and the center of the outer peripheral surface is offset from the shaft center of the drive shaft 2 by a predetermined amount, and the annular portion of the link arm 4 is rotatable on the outer peripheral surface. It is mated.
[0014]
The rocker arm 6 has a substantially central portion supported by the eccentric cam portion 18 so as to be swingable, and an arm portion of the link arm 4 is linked to one end portion thereof via a connecting pin 5. The upper end portion of the link member 8 is linked to the end portion via the connecting pin 7. The eccentric cam portion 18 is eccentric from the axis of the control shaft 12, and accordingly, the rocking center of the rocker arm 6 changes according to the angular position of the control shaft 12.
[0015]
The rocking cam 9 is fitted to the outer periphery of the drive shaft 2 and is rotatably supported, and the lower end portion of the link member 8 is linked to the end portion extending sideways via a connecting pin 17. ing. On the lower surface of the swing cam 9, a base circle surface concentric with the drive shaft 2 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface are in contact with the upper surface of the tappet 10 according to the swing position of the swing cam 9.
[0016]
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 9 swings and the cam surface comes into contact with the tappet 10, it gradually lifts. A slight ramp section is provided between the base circle section and the lift section.
[0017]
As shown in FIG. 1, the control shaft 12 is configured to rotate within a predetermined angle range by a lift / operation angle control actuator 13 provided at one end. The lift / operating angle control actuator 13 includes, for example, a servo motor that drives the control shaft 12 via the worm gear 15, and is controlled by a control signal from the engine control unit 19. The rotation angle of the control shaft 12 is detected by the control shaft sensor 14.
[0018]
The operation of the variable lift / operating angle mechanism 1 will be described. When the drive shaft 2 rotates, the link arm 4 moves up and down by the cam action of the eccentric cam 3, and the rocker arm 6 swings accordingly. The swing of the rocker arm 6 is transmitted to the swing cam 9 via the link member 8, and the swing cam 9 swings. The tappet 10 is pressed by the cam action of the swing cam 9, and the intake valve 11 is lifted.
[0019]
Here, when the angle of the control shaft 12 changes via the lift / operation angle control actuator 13, the initial position of the rocker arm 6 changes, and consequently, the initial swing position of the swing cam 9 changes.
[0020]
For example, if the eccentric cam portion 18 is positioned upward in the figure, the rocker arm 6 is positioned upward as a whole, and the end of the swing cam 9 on the side of the connecting pin 17 is relatively lifted upward. Become. That is, the initial position of the swing cam 9 is inclined in a direction in which the cam surface is separated from the tappet 10. Therefore, when the swing cam 9 swings as the drive shaft 2 rotates, the base circle surface is kept in contact with the tappet 10 for a long time, and the period during which the cam surface is in contact with the tappet 10 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.
[0021]
Conversely, assuming that the eccentric cam portion 18 is positioned downward in the figure, the rocker arm 6 is positioned downward as a whole, and the end of the swing cam 9 on the side of the connecting pin 17 is relatively pushed downward. It becomes a state. That is, the initial position of the swing cam 9 is inclined in a direction in which the cam surface approaches the tappet 10. Therefore, when the swing cam 9 swings as the drive shaft 2 rotates, the portion that contacts the tappet 10 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.
[0022]
Since the initial position of the eccentric cam portion 18 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 11 change substantially symmetrically as the lift and operating angle change.
[0023]
Next, as shown in FIG. 1, the phase variable mechanism 21 relatively connects the sprocket 22 provided at the front end of the drive shaft 2, and the sprocket 22 and the drive shaft 2 within a predetermined angle range. And a phase control actuator 23 to be rotated. The sprocket 22 is interlocked with the crankshaft via a timing chain or a timing belt (not shown). The phase control actuator 23 is composed of, for example, a hydraulic or electromagnetic rotary actuator, and is controlled by a control signal from the engine control unit 19. The action of the phase control actuator 23 causes the sprocket 22 and the drive shaft 2 to rotate relative to each other, thereby delaying the lift center angle in the valve lift. 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 21 is detected by the drive shaft sensor 16 that responds to the rotational position of the drive shaft 2.
[0024]
The control of the lift / operating angle variable mechanism 1 and the phase variable mechanism 21 is not limited to the closed loop control based on the detection of the sensors 14 and 16, and may be simply open loop controlled according to the operating conditions. .
[0025]
The drive shaft 2 and the control shaft 12 described above are common in common over four cylinders arranged in series. On the other hand, the eccentric cam 3, the eccentric cam portion 18, the rocker arm 6, and the swing cam 9 are used. The variable valve mechanism including the link arm 4, the link member 8, and the like is provided for each cylinder. FIG. 1 representatively shows the variable valve mechanism for only one cylinder.
[0026]
The internal combustion engine of the present invention provided with such a variable valve device on the intake valve side does not depend on the throttle valve, and the intake amount and thus the engine output are controlled by the variable control of the intake valve 11. In a practical engine, it is preferable that a slight negative pressure exists in the intake system for recirculation of blow-by gas, etc. Therefore, instead of a throttle valve, a negative pressure control valve described later is provided upstream of the intake passage. It is desirable to provide an appropriate throttle mechanism for generating negative pressure such as 32.
[0027]
Next, FIG. 2 shows the valve lift characteristics of the intake valve under typical operating conditions. As shown in the drawing, in an extremely low load region such as an idle, the intake air mainly focuses on the lift amount. Since the amount is controlled, the lift amount becomes a minimum lift. In particular, the lift amount is so small that the phase of the lift center angle does not affect the intake air amount. The phase of the lift center angle by the phase variable mechanism 21 is the most retarded position, so that the closing timing is the position immediately before the bottom dead center.
[0028]
By setting the minimum lift in this way, the intake flow becomes choked in the gap between the intake valves 11, and the necessary minute flow rate can be stably obtained in the extremely low load region. Since the closing time is near the bottom dead center, the effective compression ratio is sufficiently high, and it is possible to ensure relatively good combustion in combination with the improvement of gas flow by the minimal lift.
[0029]
On the other hand, in the low load region where the load is higher than the extremely low load region such as idle (including the idle state where the auxiliary load is applied), the lift / operating angle is large and the lift center angle is the advanced position. It becomes. At this time, the intake air amount control is performed in consideration of the valve timing, and the intake air amount is controlled to a relatively small amount by advancing the intake valve closing timing. As a result, the lift / operating angle becomes somewhat large, and the pumping loss due to the intake valve 11 is reduced.
[0030]
In the middle load range where the load further increases and the combustion becomes stable, as shown in FIG. 2, the phase of the lift center angle is advanced while further increasing the lift / operation angle. The phase of the lift center angle is the most advanced state at a certain point in the middle load region. Thereby, internal EGR is utilized and the pumping loss can be further reduced.
[0031]
In addition, at the maximum load, the phase variable mechanism 21 is controlled so that the lift / operation angle is further expanded and the optimum valve timing is obtained. As shown in the figure, the optimum valve lift characteristic varies depending on the engine speed.
[0032]
As described above, in an extremely low load range such as an idle, a minute flow rate is controlled mainly by a lift amount as a valve lift control range, but a boundary with a low load range that is a valve timing control range, that is, control switching. The point is preferably corrected according to the actual stable combustion state. Alternatively, for simplification of control, it is also possible to detect the engine temperature and correct it accordingly. By correcting in this way, the valve timing control region can be expanded within a range that does not cause deterioration of combustion, which is advantageous in reducing pumping loss.
[0033]
FIG. 3 shows the system configuration of the entire internal combustion engine. As shown in the drawing, a negative pressure control valve 32 composed of a butterfly valve similar to a throttle valve is provided at the inlet of the intake collector 31. As described above, the negative pressure control valve 32 is a throttling mechanism for generating an appropriate negative pressure necessary for recirculation of blow-by gas as a practical engine, and is not for controlling the engine output. The opening of the negative pressure control valve 32 is controlled by an actuator 33 made of, for example, a DC motor. The intake air collector 31 is provided with a pressure sensor 34 and an intake air temperature sensor 35 for detecting the intake air state. Reference numeral 36 denotes a crank angle sensor that detects the rotational position (crank angle) of the crankshaft, and reference numeral 37 denotes an air-fuel ratio sensor (wide area air-fuel ratio sensor or oxygen sensor) that responds to the exhaust air-fuel ratio. Detection signals from these sensors are input to the engine control unit 19. In addition, for example, a signal indicating the amount of depression of an accelerator pedal (not shown) operated by the driver is input as a signal indicating the required load.
[0034]
In the configuration as described above, when the control shaft 12 is driven in the rotational direction by the lift / operating angle control actuator 13, the valve lift characteristics of the intake valves 11 of the cylinders change all at once. That is, the lift / operating angle changes. Here, as shown in FIG. 4, when the actuator 13 operates and the angle of the control shaft 12 changes while the intake valve 11 of a certain cylinder is being lifted, the valve lift characteristic is deformed. The example of FIG. 4 shows a state in which the control shaft 12 rotates in the direction of expansion of the lift / operating angle during the lift, and the valve should be a broken line at the initial position of the control shaft 12. The lift characteristics are deformed as indicated by the solid line. The effect of this deformation of the valve lift characteristics is that during the low rotation time when the actual lift period is relatively long, and the low lift rate where the rate of change in the air amount is large even with the same lift / operating angle change.・ Especially large at operating angle. Therefore, in this embodiment, the drive speed of the lift / operation angle control actuator 13 during the lift period is limited in the low-speed and low-load region shown in FIG. 5 which is controlled at low rotation and low lift / operation angle.
[0035]
FIG. 6 is a characteristic diagram showing an embodiment in which the drive speed of the lift / operating angle control actuator 13 is limited based on the crank angle. The period (crank angle range) indicated by hatching is as follows. It is a limited period including during intake valve lift. The illustrated example is in the order of ignition of # 1- # 3- # 4- # 2 and is controlled to a low lift / operating angle. Therefore, as shown in FIG. Are not overlapping each other. Further, the period from t1 to t2 immediately before the intake valve lift indicates the fuel injection period of each cylinder, and the limit period is set as a period from the fuel injection start t1 to the intake valve closing timing. Note that the fuel injection timing may be retarded from the normal time so as to approach the intake valve closing timing under the predetermined operating condition for limiting the driving speed shown in FIG.
[0036]
In the embodiment shown in FIG. 6, the lift / operating angle control actuator 13 is not driven and the angle of the control shaft 12 is held at a fixed position during the above-mentioned limit period. That is, when the target lift / operating angle is expanded due to a change in operating conditions, for example, the angle of the control shaft 12 changes at a constant speed only outside the limit period, as shown in the figure, and changes within the limit period. do not do. Therefore, the valve lift characteristic of the intake valve 11 of each cylinder does not change and gradually increases in accordance with the firing order. In this embodiment, the drive start of the lift / operating angle control actuator 13 is outside the limit period. Accordingly, there is no change in the intake air amount after fuel injection.
[0037]
FIG. 7 shows the characteristics of the second embodiment. The limit period is from the start of fuel injection to the intake valve closing timing. In this embodiment, the drive speed of the lift / operating angle control actuator 13 within the limit period is limited to a constant speed smaller than the drive speed outside the limit period. That is, when the target lift / operating angle is increased due to, for example, a change in operating conditions, the actuator 13 operates continuously, but its speed changes. Therefore, the deformation of the valve lift characteristic of the intake valve 11 is small, and the error in the intake air amount that occurs after the start of fuel injection is relatively small. In addition, it is possible to obtain the change in the driving speed as described above by changing the driving torque of the lift / operating angle control actuator 13.
[0038]
Next, FIG. 8 is a characteristic diagram showing the third embodiment. In this embodiment, the drive speed of the lift / operating angle control actuator 13 during the limit period is a constant speed, and each intake air The smaller the lift of the valve 11, the lower the driving speed is limited. In this embodiment, since the fuel injection start t1 is before the intake top dead center and is relatively far from the lift period, the fuel injection amount can be corrected by predicting the deformation of the valve lift characteristic. desirable.
[0039]
FIG. 9 is a flowchart showing the control flow of the lift / operation angle control actuator 13 which is configured to limit the drive speed as described above. First, the accelerator opening indicating the engine operating condition and the engine speed are read (step 1), the required torque (required air amount) is calculated from these (step 2), and the target valve lift characteristic is obtained (step 3). Then, the required drive amount of the lift / operating angle control actuator 13 is calculated (step 4). Next, in step 5, it is determined whether or not the operating condition is within the predetermined restricted area of FIG. If it is not within the restricted area, normal driving of the actuator 13 is permitted (step 6). If it is within the restricted region, it is determined in step 7 whether the drive amount of the actuator 13 is equal to or greater than a predetermined threshold value. If the drive amount of the actuator 13 is small, it is assumed that the drive speed is not restricted even within the restricted region, and normal drive of the actuator 13 is permitted (step 8). If the drive amount of the actuator 13 is equal to or greater than a predetermined threshold value, the process proceeds to step 9 to set a drive speed limit, and then the actuator 13 is driven (step 10). Specific modes for limiting the driving speed are as described in the above embodiments.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing the configuration of a variable valve operating apparatus for an internal combustion engine according to the present invention.
FIG. 2 is a characteristic diagram showing valve lift characteristics under typical operating conditions.
FIG. 3 is a system configuration diagram of the entire internal combustion engine.
FIG. 4 is a characteristic diagram showing deformation of a valve lift characteristic associated with a change in the angle of a control shaft during lift.
FIG. 5 is a characteristic diagram showing an operation region in which drive speed is limited.
FIG. 6 is a time chart showing a first embodiment of drive speed limitation.
FIG. 7 is a time chart showing a second embodiment of the drive speed limitation.
FIG. 8 is a time chart showing a third embodiment for limiting the driving speed.
FIG. 9 is a flowchart showing a control flow of a lift / operating angle control actuator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lift / operation angle variable mechanism 2 ... Drive shaft 3 ... Eccentric cam 6 ... Rocker arm 8 ... Link member 9 ... Swing cam 11 ... Intake valve 12 ... Control shaft 19 ... Engine control unit

Claims (13)

The intake valve of each cylinder is provided with a variable valve mechanism capable of continuously changing the valve lift characteristics , and one actuator is linked to the variable valve mechanism of a plurality of cylinders. In a variable valve operating system for an internal combustion engine in which the valve lift characteristics of the intake valves change simultaneously and continuously ,
The actuator for changing the valve lift characteristics on the assumption that the period including at least the lift period of the intake valve of each cylinder is a limit period, and the period outside the limit period does not include the lift period of the intake valve of any cylinder The variable valve operating apparatus for an internal combustion engine is characterized in that the driving speed of the internal combustion engine is limited to be relatively smaller than the actuator driving speed in a period outside the limit period in the limit period . 2. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the limited period is determined based on a crank angle. The variable valve operating apparatus for an internal combustion engine according to claim 1 or 2, wherein the actuator drive speed is limited during the restriction period when the internal combustion engine is in a predetermined low speed range. 4. The variable valve for an internal combustion engine according to claim 1, wherein when the valve lift characteristic of the intake valve is controlled to be low lift, the actuator drive speed is limited during the limit period. apparatus. 3. The variable valve operating apparatus for an internal combustion engine according to claim 2, wherein a period from the start of fuel injection to the intake valve closing timing is set as the limit period . It said during limited periods, variable valve device for an internal combustion engine according to claim 2 or 5, characterized in that holding at a predetermined position of the actuator as a non-driving. It said during limited periods, variable valve device for an internal combustion engine according to claim 2 or 5, characterized in that to drive the actuator with a lower speed than the driving speed of the outside the restriction period. 6. The variable valve operating apparatus for an internal combustion engine according to claim 5 , wherein the actuator drive start time is outside the limit period .   A control shaft linked to a variable valve mechanism of a plurality of cylinders is provided, and the valve lift characteristic is changed by changing the angle of the control shaft with an actuator. The variable valve operating apparatus for an internal combustion engine according to any one of 8. 6. The variable valve operating apparatus for an internal combustion engine according to claim 5 , wherein when the actuator driving speed is limited, the fuel injection timing of each cylinder is corrected so as to approach the intake valve closing timing. The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 10, wherein the actuator drive speed in the restriction period is restricted to be lower as the lift of the intake valve is smaller. 12. The internal combustion engine according to claim 1, wherein the actuator driving speed in the limit period is made smaller than the actuator driving speed in a period outside the limit period by changing the drive torque of the actuator. Variable valve device.   The variable valve operating apparatus for an internal combustion engine according to any one of claims 1 to 12, wherein an output of the internal combustion engine is controlled by a valve lift characteristic of the intake valve.

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