JP3508218B2 - Engine control device with variable valve mechanism - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve mechanism, and more particularly, to changing at least one of an opening / closing timing of an intake valve in an open state and a lift amount at the time of valve opening. The present invention relates to an engine control device provided with a variable valve mechanism. 2. Description of the Related Art In an engine for an automobile or the like, in order to improve fuel consumption performance and output performance, an opening state such as an opening / closing timing with respect to a crank angle of an intake / exhaust valve and a lift amount at the time of opening the valve. Is variably controlled to an optimum state in accordance with the operation state. For example, Japanese Patent Application Laid-Open No. 2-271014 discloses a variable valve mechanism having the following configuration. That is, as shown in FIG. 5, this variable valve mechanism forms cams B... B whose profile changes along the axial direction on a camshaft A, and a hydraulic actuator is provided at one end of the camshaft A. C, the camshaft A is slid in the axial direction by supplying and discharging hydraulic pressure to and from the actuator C. According to this, the cam B is slid in the axial direction
.. B, the profile of the portion in contact with the upper surface of the tappet D... D changes, and the opening / closing timing of the valves E. Become. The above-mentioned publication discloses that such a variable valve operating mechanism is used to set a valve operating angle in a steady state in advance in accordance with an operating region of an engine, for example, a low rotation region, a middle rotation region, and a high rotation region. In addition, it is described that the valve operating angle is set to a separately set transient valve operating angle during a transition in which the operating region changes, and according to this, the switching of the valve operating angle during the transition is performed smoothly. Therefore, it is said that the drivability is not deteriorated due to the temporary decrease in the torque. [0005] Incidentally, when the valve opening state such as the opening / closing timing of the valve and the lift amount at the time of opening the valve as described above, particularly the valve opening state of the intake valve, is changed,
When the throttle valve opening is small and the load on the downstream side of the load is so low that the flow rate of intake air exceeds the sonic speed and a so-called surging state occurs, the change speed of the valve opening state and the response delay of the change of the intake pressure accompanying the change. Therefore, there is a problem that the air filling amount or the engine torque fluctuates temporarily. That is, as shown in FIG. 6, the closing timing of the intake valve is, for example, -50 ° with respect to the intake bottom dead center.
Is switched from early closing to late closing of + 40 °, the actual volume of the combustion chamber increases from V1 to V2 (V1
<V2), the negative pressure of the intake air supplied to the combustion chamber is P1
From P1 to P2 (P1> P2), and theoretically V1 × P
1 = V2 × P2 holds, but in fact,
While the actual volume of the combustion chamber changes at the same time as the change of the valve closing timing, the intake negative pressure changes slowly when the opening of the throttle valve is small, and when the actual volume increases to V2. At the time indicated by the symbol a in FIG. 6, a state larger than the theoretical value indicated by the dashed line occurs at the time indicated by the symbol a in FIG. [0007] Then, due to the negative pressure greater than the theoretical value, intake air is sucked into the combustion chamber more than necessary, and the air charge increases. This increase in the air charge is caused by the opening of the throttle valve. During a small low load or intake surging, the air flow sensor upstream of the throttle valve does not detect or delays detection, so the fuel supply amount controlled based on the output of this sensor does not correspond to an increase in the air charge amount. As a result, the air-fuel ratio temporarily becomes lean. On the other hand, when the closing timing of the intake valve is switched from a late closing of + 40 ° to an early closing of -50 °, on the other hand, as shown by reference numeral A in FIG. Due to the response delay of the pressure change, the actual volume of the combustion chamber becomes V
When the pressure decreases to 1, the negative pressure has not increased to P1, and a state occurs in which the negative pressure is smaller than the theoretical value indicated by the dashed line. Therefore, at this time, the intake air amount or the air filling amount is insufficient, but also in this case, the insufficient air filling amount is not detected by the air flow sensor or the detection is delayed. The corresponding correction of the fuel supply amount is not performed, and as a result, the air-fuel ratio becomes temporarily rich. Then, a torque shock occurs due to a temporary change in the air filling amount or the air-fuel ratio when the opening state of the intake valve is changed. Further, such a torque shock occurs when the fuel injection amount is corrected with respect to the fluctuation of the air charge amount.
It is also conceivable that the correction itself occurs. [0010] Therefore, an object of the present invention is to reduce the torque shock at the time of changing the open state of the intake valve in an engine provided with such a variable valve operating mechanism. [0011] In order to solve the above problems, an engine control apparatus provided with a variable valve mechanism according to the present invention is characterized by using the following means. That is, the invention according to claim 1 of the present application is provided with a variable valve mechanism for changing at least one of an opening / closing timing as an open state of an intake valve and a lift amount at the time of valve opening, and operating the engine. Operating state detecting means for detecting the state; and valve opening state changing means for operating the variable valve mechanism in accordance with the operating state of the engine detected by the detecting means to change the opening state of the intake valve. A change delay means for changing the opening speed of the intake valve by the valve opening state changing means to a speed lower than the operating speed of the variable valve mechanism itself; and a change by the change delay means. A delay amount setting means for increasing the speed delay amount as the load of the engine decreases, and an opening state of the intake valve associated with a change in the operating state of the engine to an idle state. When changing, characterized in that a delay inhibiting means for inhibiting the delay control change operation by the changing delay means. According to the present invention, the following effects can be obtained by using the above means. That is, there is provided a variable valve operating mechanism for changing at least one of the opening / closing timing as the opening state of the intake valve or the lift amount at the time of opening, and the opening state of the intake valve according to the operating state of the engine. When the open state of the intake valve is changed, the change speed is made slower than the operating speed of the variable valve mechanism itself by the change delay means. The change speed of the substantial volume of the combustion chamber and the change speed of the intake pressure due to the change in the pressure change correspond to each other. Therefore,
Temporary increase or decrease of the air charge due to the delay of the change of the intake pressure with respect to the change of the actual volume of the combustion chamber is suppressed, and the torque shock due to the change of the air charge is reduced. In this case, the change speed of the opening state of the intake valve is reduced as the engine load decreases,
This change speed corresponds to a response delay of the intake pressure change that becomes more remarkable at a low load, so that the change speed of the real volume of the combustion chamber and the change speed of the intake pressure always correspond with high accuracy, and the air The temporary increase or decrease of the filling amount and the associated torque shock are more effectively reduced. In particular, when the opening state of the intake valve is changed due to the change of the operating state of the engine to the idle state, the delay control of this changing operation is prohibited, and the target valve opening state is set. Since the shift is performed promptly, further instability caused by delaying the change of the opening state of the intake valve in the idle region where the operating state tends to be unstable can be avoided. Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an intake passage 5 and an exhaust passage 6 communicate with a combustion chamber 2 of an engine 1 through an intake valve 3 and an exhaust valve 4, respectively. From the upstream side, an air cleaner 7 for filtering the intake air, an air flow sensor 8 for detecting the intake air amount, a throttle valve 9 for controlling the intake air amount or the engine output, and supplying fuel to the combustion chamber 2 A fuel injection valve 10 is provided. Further, a bypass passage 11 for bypassing the throttle valve 9 is provided in the intake passage 5, and an idle speed control valve (hereinafter, referred to as an ISC valve) 12 for adjusting a bypass air amount is provided in the bypass passage 11. The exhaust passage 6 is provided with a catalytic converter 13 for purifying exhaust gas. In the engine 1, for example, variable valve mechanisms (hereinafter, referred to as VVT mechanisms) 14a and 14b as shown in FIG. 5 are provided on the intake valve 3 side and the exhaust valve 4 side, respectively. And these valves 3,
The valve opening state such as the opening / closing timing with respect to the crank angle and the lift amount at the time of opening the valve is variably controlled according to the operating state, and the VVT mechanisms 14a, 14b
A camshaft position sensor 15 is provided which detects the position of the camshaft which is slid in the axial direction to determine the open state of the intake valve 3 and the exhaust valve 4. Further, the engine 1 is provided with an electronic control type control unit (hereinafter referred to as ECU) 16. The ECU 16 receives an intake air amount signal from the air flow sensor 8, a throttle opening signal from a throttle opening sensor 17 for detecting the opening of the throttle valve 9, and a crank angle sensor 18 for detecting the engine speed. An engine speed signal, a boost pressure signal from a boost pressure sensor 19 for detecting a boost pressure downstream of the throttle valve 9 in the intake passage 5, and a camshaft position signal from the camshaft position sensor 15 are input. VV based on the signal
In addition to controlling the suction by the T mechanisms 14a and 14b and changing the opening state of the exhaust valves 3 and 4, the fuel injection control for the fuel injection valve 10, the bypass air control for the ISC valve 12, the ignition timing control for the spark plug 19, and the like are performed. Is supposed to do it. Next, as part of the control of the valve opening state performed by the ECU 16, the control for changing the valve closing timing of the intake valve 3 will be described with reference to a flowchart. As shown in FIG. 2, the ECU 16 first
In steps S1 and S2, the throttle opening TVO and the engine speed Ne are determined based on the signals from the sensors 17 and 18.
Then, in step S3, it is determined whether or not the closing timing of the intake valve 3 is changed. This determination is made based on a preset map, and the valve closing timing on the map corresponding to the throttle opening TVO measured this time and the engine speed Ne matches the current valve closing timing. In step S4, it is determined that the valve closing timing needs to be changed, and the valve closing timing on the map is set as the target timing P in step S4. When changing the valve closing timing,
Next, the ECU 16 sets the control gain G for operating the VVT mechanism 14a in step S5 according to a subroutine described later, then operates the VVT mechanism 14a in step S6, and sets the current timing P0 in step S7. The control is terminated when it is determined in step S8 that the current valve closing timing P0 has become equal to the target timing P in step S8. As a result, the closing timing of the intake valve 3 is changed to a timing corresponding to the throttle opening TVO and the engine speed Ne. At this time, the gain G is appropriately set. Thus, the switching operation of the valve closing timing is made slower than the operation speed of the VVT mechanism itself. Therefore, the delay control causes the change speed of the substantial volume of the combustion chamber 2 due to the change of the valve closing timing to correspond to the change speed of the intake negative pressure. The temporary increase or decrease in the air charge due to the delay in the pressure change is suppressed, and the torque shock due to the change in the air charge is reduced. In this case, if the gain G is made smaller as the throttle opening TVO becomes smaller and the change speed of the closing timing of the intake valve 3 is made slower, the change speed becomes smaller at low throttle opening. This corresponds to a response delay of a change in intake negative pressure that becomes more significant. Therefore,
The rate of change of the actual volume of the combustion chamber 2 and the rate of change of the negative pressure of the intake air always correspond with high accuracy, and the temporary increase or decrease of the air charge amount or the associated torque shock is more effectively reduced. become. Note that step S in the flowchart of FIG.
The setting of the control gain G according to 5 is performed according to the flowchart shown in FIG. That is, in steps S11 and S12, the throttle opening TVO and the engine speed Ne are read, and in step S13, a target timing P corresponding to these measured values is set based on the aforementioned map.
In step S14, the current valve closing timing P0 is read. When the current timing P0 is smaller than the target timing P, that is, when the valve closing timing of the intake valve 3 is controlled to be delayed, the engine speed Ne and the throttle opening TVO are set to predetermined values L.
1, L2, and if the current operating state belongs to the idle region I shown in FIG. 4, the ECU 16 executes steps S15 to S16 to execute the VVT mechanism 1
The control gain G of 4a is set to G1, otherwise, step S17 is executed to set the control gain G to G2. Here, G1> G2, so that
In the control in the direction of delaying the valve closing timing as described above, when the operating region belongs to the idle region I, V
The operating speed of the VT mechanism 14a is increased, in other words, the above-described delay control for reducing the operating speed of the VT mechanism 14a is prohibited. This is because in the idle region I where the combustion state tends to be unstable, VV
This is because, when the operation of the T mechanism 14a is delayed, if the operation is delayed, the combustion state becomes more unstable. Therefore, by prohibiting the delay control, the deterioration of the combustion state in the idle region I is deteriorated. To avoid. As described above, according to the present invention, there is provided a variable valve mechanism for changing at least one of the opening / closing timing as the valve opening state of the intake valve or the lift amount at the time of valve opening. The following effects can be obtained in an engine configured to change the opening state of the intake valve according to the operating state of the engine. That is, according to the present invention, when the opening state of the intake valve is changed, the change speed is made slower than the operation speed of the variable valve mechanism itself by the change delay means.
The change speed of the substantial volume of the combustion chamber and the change speed of the intake pressure by the change of the valve opening state correspond to each other. Therefore, the temporary increase or decrease of the air charge due to the delay of the change of the intake pressure with respect to the change of the actual volume of the combustion chamber is suppressed, and the torque shock due to the change of the air charge is reduced. Become. In this case, the changing speed of the open state of the intake valve is reduced as the engine load becomes lower.
This change speed corresponds to a response delay of the intake pressure change that becomes more remarkable at a low load, so that the change speed of the real volume of the combustion chamber and the change speed of the intake pressure always correspond with high accuracy, and the air The temporary increase or decrease of the filling amount and the associated torque shock are more effectively reduced. In particular, when the opening state of the intake valve is changed due to the change of the operating state of the engine to the idle state, the delay control of this changing operation is prohibited, and the target valve opening state is set. Since the shift is performed promptly, further instability caused by delaying the change of the opening state of the intake valve in the idle region where the operating state tends to be unstable can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a control system diagram of an engine according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating a control operation according to the embodiment. FIG. 3 is a flowchart illustrating a subroutine of the control of FIG. 2; FIG. 4 is a map used in the control of FIG. 2; FIG. 5 is a schematic view showing a general configuration of a variable valve mechanism. FIG. 6 is an explanatory diagram of a problem when changing the opening / closing timing of the intake valve from early closing to late closing; FIG. 7 is an explanatory diagram of a problem when the opening / closing timing of the intake valve is changed from late closing to early closing. [Description of Signs] 3 Intake valves 14a, 14b Variable valve mechanism 16 Valve opening state changing means, change delay means,
Delay amount setting means, delay prohibition means (engine control unit)

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 320 F02D 41/04 320 45/00 312 45/00 312J (56) References JP-A-6-10747 (JP, A) JP-A-5-231211 (JP, A) JP-A-3-260357 (JP, A) JP-A-4-124436 (JP, A) JP-A-6-241102 (JP, A) JP-A-6 −146936 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 13/02 F02D 41/00-45/00

Claims (1)

(57) [Claim 1] A variable valve mechanism for changing at least one of an opening / closing timing as an opening state of an intake valve and a lift amount at the time of opening is provided, and an operating state of an engine. Operating state detecting means for detecting the operating state of the engine, and valve opening state changing means for operating the variable valve mechanism to change the opening state of the intake valve in accordance with the operating state of the engine detected by the detecting means. An engine control device provided with a variable valve operating mechanism, wherein when the opening state of the intake valve is changed by the valve opening state changing means, the changing speed is made lower than the operating speed of the variable valve operating mechanism itself. Change delay means; delay amount setting means for increasing the delay amount of the change speed by the change delay means as the load of the engine decreases; and suction delay caused by the engine operating state changing to the idle state. When changing the open state of the valve, the control apparatus for an engine equipped with a variable valve mechanism, characterized in that the delay inhibiting means for inhibiting the delay control change operation by the changing delay means.