JP3991940B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device, and more particularly to an engine control device capable of changing the valve overlap of an intake valve and an exhaust valve.
[0002]
[Prior art]
In a vehicle engine control device, in order to reduce the amount of HC emissions when starting the engine, control is performed to improve the fuel vaporization by promoting the development of the suction negative pressure near the fuel injection valve. Increasing the speed of the engine speed can promote the development of intake negative pressure, but in this case, the peak speed excessively increases due to the torque generated by the engine itself after the first explosion, In terms of engine noise, the drivability of the engine may be deteriorated.
[0003]
Patent Document 1 describes a control device that improves the increase in engine speed when the engine is started. In this engine control device, at the initial stage of cranking, the intake valve closing timing is advanced from the bottom dead center, the actual compression ratio is lowered to increase the cranking speed early, and after the cranking speed rises, The initial explosion is ensured by retarding the intake valve closing timing and increasing the actual compression ratio.
[0004]
[Patent Document 1]
JP 2002-276446 A (page 11, FIG. 10)
[0005]
[Problems to be solved by the invention]
In the engine control device described in Patent Document 1, the actual compression ratio is set to be delayed by retarding the intake valve closing timing before the first explosion so that the first explosion can be performed reliably. If there is no means for suppressing the number and the engine speed is increased at a setting with a high actual compression ratio, the peak speed may be excessively increased. Further, as described above, the excessive increase in the peak rotational speed may cause the engine drivability to deteriorate in that excessive blow-up feeling and engine noise are generated.
[0006]
An object of the present invention is to achieve both reduction of HC emissions and engine drivability at the time of starting an engine of a vehicle.
[0007]
[Means for Solving the Problems]
An engine control apparatus according to the present invention is an engine control apparatus capable of changing the valve overlap of an intake valve and an exhaust valve, and includes a condition determination unit and a valve control unit. The condition determining means determines whether or not the engine speed has exceeded a predetermined speed after the start of the engine . The valve control means sets the valve timing of the intake valve or the exhaust valve so that the valve overlap becomes larger than that during normal operation at the start of engine start, and the valve overlap becomes smaller when a predetermined condition is satisfied. Thus, the valve timing of the intake valve or the exhaust valve is set. The predetermined rotational speed in the condition determining means is set based on the estimated peak rotational speed in the engine operating state before satisfying the predetermined condition and the upper limit target rotational speed that is a limit engine rotational speed that does not deteriorate the engine operability. .
[0008]
【The invention's effect】
According to the present invention, the valve overlap is set to be larger than that during normal operation at the start of engine start, pump loss during cranking is reduced, and the number of revolutions during cranking and after the first explosion is quickly increased. As a result, the development of the intake negative pressure is promoted, the fuel vaporization is improved, and the HC emission amount from the engine can be reduced. In addition, when a predetermined condition is satisfied, an engine caused by an excessive increase in the peak rotational speed is set by reducing the valve overlap to increase the pump loss and suppressing the peak rotational speed of the engine from excessively increasing. The deterioration of drivability can be suppressed.
[0009]
As a result, at the time of starting the engine, it is possible to achieve both reduction of the HC emission amount and engine operability.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(1) First Embodiment (1-1) Configuration FIG. 1 is a schematic view of a vehicle engine to which an engine control device according to a first embodiment is applied.
[0011]
The engine body 1 is formed with a combustion chamber 1a and an intake port 2a and an exhaust port 3a communicating with the combustion chamber 1a. A spark plug 10 that is ignited by an ignition coil 9 is mounted in the upper center of the combustion chamber 1a. The ignition coil 9 is driven by a signal from a control unit (ECU) 13 described later. An intake valve 2b and an exhaust valve 2b for controlling the inflow and outflow of intake air and exhaust gas are disposed at the opening portions of the combustion chamber 1a of the intake port 2a and the exhaust port 3a.
[0012]
The intake valve 2b and the exhaust valve 3b are opened and closed by valve drive mechanisms 2c and 3c, respectively. The valve drive mechanism 2c that opens and closes the intake valve 2b is provided with a phase variable mechanism that changes the lift center angle of the intake valve 2b as shown in FIG. As such a phase variable mechanism, for example, the one described in JP-A-2002-295290 is used.
[0013]
A fuel injection valve 8 for injecting and supplying fuel into the intake port 2a based on a drive signal from the control unit 13 is provided near the upstream side of the intake valve 2b of the intake port 2a. A starter motor 19 for starting rotation of the crankshaft is disposed at the lower part of the engine body 1. The starter motor 19 is driven by a drive signal output from the control unit 13 based on a signal from a starter switch 18 provided in a key switch in the vehicle interior. Further, the engine body 1 is provided with a crank angle sensor 11 for detecting the engine speed N and a water temperature sensor 12 for detecting the water temperature Tw in the cooling jacket.
[0014]
An intake passage 2 is connected to an intake port 2 a of the engine body 1. An air cleaner 4 for purifying the intake air, an air flow meter 5 for detecting the intake air amount Q, and a throttle valve 6 for controlling the intake air amount Q are arranged in the intake passage 2. The air cleaner 4 is provided with an intake air temperature sensor 20, and the intake air temperature Tair is output to the control unit 13. The air flow meter 5 detects the intake air amount Q and outputs it to the control unit 13. The throttle valve 6 is provided with a throttle sensor 6a for detecting the throttle opening TVO. Further, a collector 7 having a large volume is connected downstream of the throttle valve 6, and a bypass passage 14 that bypasses the throttle valve 6 and is connected to the collector 7 from the upstream side of the throttle valve 6 is provided. The bypass passage 14 is provided with an idle control valve 14a for controlling the amount of air passing therethrough. The idle control valve 14 a controls the intake air amount Q at the time of engine start by a signal from the control unit 13. In the present embodiment, the intake air amount Q at the time of starting the engine is controlled by the idle control valve 14a. However, when the throttle valve 6 is an electromagnetic type, the intake air amount Q at the time of starting the engine is controlled by the throttle valve 6 and bypassed. The passage 14 and the idle control valve 14a may be omitted.
[0015]
The control unit 13 incorporates a microcomputer having a CPU, a ROM, a RAM, and an input / output port. The intake air amount Q from the air flow meter 5, the throttle opening TVO from the throttle sensor 6 a, and the start from the start switch 18. Various signals such as a signal, a water temperature Tw from the water temperature sensor 12, an intake air temperature Tair from the intake air temperature sensor 20, and an engine speed N from the crank angle sensor 11 are read to control the rotation of the engine.
[0016]
(1-2) Engine Start Control FIGS. 3 to 5 are flowcharts of engine start control. FIG. 6 is an explanatory diagram for calculating the estimated peak rotational speed Np. 7 and 8 are time charts showing changes in the characteristic values when the engine is started. 7 and 8, I is a change in each characteristic value in the case of the present embodiment, and II is a change in the characteristic value for comparison, which is a change when the engine speed is suppressed from the start. .
[0017]
In step S1, it is determined whether or not the engine is in operation. If the engine is not in operation (before time t = t1 in FIG. 7), the process proceeds to step S12 to set the valve timing for starting. That is, the lift center angle is set to θ1 (FIG. 7D). At this time, as shown in FIG. 2, when the lift center angle is θ1, the intake valve opening timing IVO1 is advanced from the top dead center TDC, and the valve overlap φ1 of the intake valve 2b and the exhaust valve 3b is from the normal operation time. (FIG. 7 (e)). For example, the advance amount from the top dead center TDC of IVO1 is set to 5 degrees or more, and the valve overlap φ1 is set to 30 degrees or more.
[0018]
In step S13, it is determined whether or not the deviation between the valve timing set in step S12 and the actual valve timing is equal to or smaller than a predetermined value. If the deviation is equal to or smaller than the predetermined value, the process returns. If it is not below, it will transfer to step S14 and will correct | amend so that a lift center angle may approach (theta) 1.
[0019]
By setting the valve overlap φ1 to be larger than that during normal operation before engine operation as in steps S12 to S14, the engine speed N is quickly compared with the curve of II during cranking and after the first explosion. It rises (FIGS. 7A and 7B). By increasing the rising speed ΔN, the development of the suction negative pressure Pb in the vicinity of the fuel injection valve 8 is promoted (FIG. 7C). Can be reduced. As a result, as shown in FIG. 8, the actual air-fuel ratio A / F in the air-fuel mixture in the vicinity of the fuel injection valve 8 becomes sufficiently close to the set value, and the fuel increase in consideration of the wall flow can be reduced. Thus, the amount of HC emissions can be reduced.
[0020]
If it is determined in step S1 that the engine is operating, the process proceeds to step S2. In step S2, the current valve timing is detected. In step S3, the engine speed N, the rising speed ΔN, the intake air amount Q, the intake negative pressure Pb, the water temperature Tw, and the intake air temperature Tair are detected.
[0021]
In step S4, it is determined whether or not the engine speed N has not reached the peak speed Np. Specifically, the determination is made based on whether or not a predetermined time T0 has elapsed from the time (time t4) when the engine speed N becomes a control start speed Ns described later. The predetermined time T0 is long enough for the engine speed N to pass the peak speed Np. Whether or not the engine speed N has not reached the peak speed Np may be determined based on whether or not the deviation between the engine speed N and the target idle speed Na has become a predetermined value or less. That is, when the deviation exceeds a predetermined value, the engine speed N has not reached the peak speed Np, and when the deviation is less than the predetermined value, the engine speed N becomes the peak speed Np. It may be determined that it has been reached.
[0022]
If the engine speed N has not reached the peak speed Np in step S4, the process proceeds to step S5.
[0023]
In step S5, an estimated peak rotational speed Np is calculated. FIG. 4 is a flowchart showing specific processing for calculating the estimated peak rotational speed Np in step S5.
[0024]
In step S21, the generated torque Ti at the present time (time t0 in FIG. 6) is calculated from the engine speed N, the rotational speed increase ΔN, the water temperature Tw, and the valve timing. In step S22, based on the engine speed N, the water temperature Tw, and the valve timing, a friction torque Tf as an engine load necessary for maintaining the engine rotation is calculated. In step S23, it is determined whether or not generated torque Ti = friction torque Tf. That is, it is determined whether or not the increase speed ΔN = 0 and the engine speed N has reached the peak speed Np. If the generated torque Ti is not equal to the friction torque Tf, the process proceeds to step S24. In step S24, a surplus torque Ti-Tf for increasing the engine speed N is calculated, an increase speed ΔN and an engine speed N after a minute time are calculated, and the calculations of steps S21 and S22 are performed using these ΔN and N. repeat. The calculations in steps S21 and S22 are repeated every minute until Ti = Tf in step S23, and the generated torque Ti and the friction torque Tf are obtained as shown by the curves Ti and Tf (θ = θ1) in FIG. 6B. . When Ti = Tf in step S23, the process proceeds to step S25, and the engine speed N at this time is estimated as the peak speed Np. Here, the estimated peak rotational speed Np is estimated in consideration of the water temperature Tw in addition to the engine rotational speed N and the rising speed ΔN, but the estimated peak rotational speed Np is further estimated in consideration of the oil temperature and the intake air temperature Tair. Anyway.
[0025]
In step S6, the estimated peak rotational speed Np is compared with the upper limit target rotational speed Nm. Here, the upper limit target engine speed Nm is a limit engine speed that does not deteriorate the drivability of the engine, that is, does not cause excessive feeling of blow-up or engine noise. When the estimated peak rotational speed Np is equal to or lower than the upper limit target rotational speed Nm, the process returns to step S1 because there is no need to suppress the engine rotational speed N. On the other hand, when the estimated peak rotational speed Np exceeds the upper limit target rotational speed Nm as shown by the solid line in FIG. 6A, it is necessary to suppress the engine rotational speed N and lower the peak rotational speed Np. The process proceeds to step S7.
[0026]
Hereinafter, in FIG. 6A, processing for suppressing the peak rotational speed Np to the upper limit target rotational speed Nm will be described below.
[0027]
In step S7, a control start rotational speed Ns for starting the engine rotational speed suppression control is calculated. FIG. 5 is a flowchart showing a process for calculating the control start rotational speed Ns.
[0028]
In step S31, based on the difference between the estimated peak rotational speed Np and the upper limit target rotational speed Nm, a required torque reduction allowance ΔT required to suppress the estimated peak rotational speed Np to the upper limit target rotational speed Nm is calculated. In step S32, the friction torque for every minute time when the valve timing is changed is calculated based on the MAP of the sensitivity of the friction torque with respect to the change of the valve overlap as shown in FIG. In step S3 3, in consideration of the required torque drop allowance [Delta] T, the responsiveness of the valve timing change the friction torque Tf (response delay until reaching the actual target value after setting the valve timing to the target value), the control The starting rotational speed Ns is calculated.
[0029]
In step S8, it is determined whether or not the engine speed N has reached the control start speed Ns. If the engine speed N is less than the control start speed Ns, the process returns. If the engine speed N is equal to or greater than the control start speed Ns, the process proceeds to step S9.
[0030]
In step S9, a valve overlap target value φ2 is calculated based on the required torque reduction allowance ΔT. The valve overlap target value φ2 is smaller than the initial value φ1, as shown in FIG. 2, and is a value that can increase the pump loss (friction torque) and suppress the peak rotational speed Np to the upper limit target rotational speed Nm. . Then, the target lift center angle θ2 of the intake valve 2b corresponding to the target overlap φ2 is calculated.
[0031]
In step S10, the lift center angle of the intake valve 2b is set to θ2. In step S11, it is determined whether or not the deviation between the target lift center angle θ2 and the actual lift center angle is a predetermined value or less. If the deviation is less than the predetermined value, the process returns. If the deviation is not less than the predetermined value, the process proceeds to step S16, and the lift center angle is corrected so as to approach θ2.
[0032]
Thus, by setting the lift center angle to θ2 and reducing the valve overlap to φ2, the pump loss increases, the friction torque Tf increases as shown in FIG. 6B, and the peak rotational speed Np is reduced. It is suppressed to the upper limit target rotation speed Nm (FIGS. 6A and 7).
[0033]
In step S4, when the engine speed N reaches the peak speed Np, the process proceeds to step S15, and valve timing control during normal operation is performed. That is, as shown after time t6 in FIG. 7, the lift center angle is advanced from θ2 to θ1, and the valve overlap is expanded from φ2 to φ1.
[0034]
(1-3) Effects In the engine control apparatus according to the present embodiment, the lift center angle of the intake valve 2b is set to advance to θ1 before starting the engine, and the valve overlap φ is set to φ1 larger than that during normal operation. Therefore, the pump loss (friction torque) becomes small at the beginning of the engine start, and the engine speed N quickly increases at the time of cranking and after the first explosion. By increasing the rising speed ΔN, the development of the suction negative pressure Pb in the vicinity of the fuel injection valve 8 is promoted, fuel vaporization is improved, and the proportion of fuel that becomes a wall flow without vaporization can be reduced. As a result, the actual air-fuel ratio A / F in the air-fuel mixture in the vicinity of the fuel injection valve 8 becomes sufficiently close to the set value, and it becomes possible to reduce the fuel increase considering the wall flow and reduce the HC emission amount. it can.
[0035]
On the other hand, when the engine speed N reaches the control start speed Ns, the lift center angle of the intake valve 2b is retarded to θ2, and the valve overlap is reduced from φ1 to φ2, thereby reducing the pump loss (friction torque). Since the increase in speed ΔN is suppressed and the peak rotational speed Np is suppressed to the upper limit target rotational speed Nm or less, an excessive feeling of blowing and engine noise associated with an excessive increase in the peak rotational speed Np are suppressed, and drivability is improved. Deterioration can be prevented.
[0036]
Thus, according to the engine control apparatus according to the present embodiment, it is possible to achieve both reduction in HC emission and drivability when the engine is started.
[0037]
Further, after the engine speed N reaches the peak speed Np, the center angle θ of the intake valve 2b is returned to θ1 and the valve overlap φ is returned to φ1 as shown in FIGS. 7D and 7E. After the engine speed N has reached a peak and the possibility of deterioration in drivability has decreased, the engine can be rotated while suppressing the friction torque.
[0038]
In the above description, when the engine speed reaches the control start speed Ns, the control for reducing the overlap is started, but the overlap is performed on the condition that a predetermined time has elapsed from the engine start start time t1. You may start the control to reduce.
[0039]
(2) Second Embodiment FIG. 10 is a schematic view of a vehicle engine to which an engine control apparatus according to a second embodiment is applied. In the first embodiment, the pump loss (friction torque) is changed by changing the lift center angle of the intake valve 2b by the phase variable mechanism. However, in this embodiment, the intake valve 2d is opened and closed by the electromagnetic drive mechanism 2d. According to the electromagnetic drive mechanism 2d, the intake valve opening / closing timing can be set independently. As such an electromagnetic drive mechanism, for example, one described in JP-A-2002-115515 is used. In the present embodiment, as shown in FIG. 11, until the engine speed N reaches the control start speed Ns, the valve overlap is set to IVO1, so that the valve overlap is larger than that during normal operation by φ1 And Thereafter, when the engine speed N reaches the control start speed Ns, the intake valve opening timing is retarded to IVO2, and the valve overlap is reduced to φ2. Thus, by delaying the intake valve opening timing from IVO1 to IVO2 and reducing the valve overlap from φ1 to φ2, the same effect as the above embodiment can be obtained. The flowchart of the engine start control of this embodiment is substantially the same as the flowchart shown in FIGS. However, in this embodiment, the intake valve opening timing IVO2 is obtained as the target valve timing in step S9, and the intake valve opening timing is set to IVO2 in step S10. In step S12, the intake valve opening timing is set to IVO2 as the starting valve timing. In step S15, the intake valve opening timing is set to IVO2 as the valve timing during normal operation.
[0040]
Further, in the present embodiment, the valve overlap is changed by controlling the intake valve opening timing by the electromagnetic drive mechanism 2d, so there is no need to consider the response delay of the valve timing change, and the valve overlap can be achieved in a very short time. Can be changed to a value. For this reason, the timing at which the valve overlap change control is started can be delayed as compared with the above embodiment, and the control start rotation speed Ns can be set higher. As a result, it is possible to further increase the intake negative pressure Pb by increasing the engine speed N for a longer time and further reduce the HC emission amount.
[0041]
(3) Third Embodiment FIG. 12 is a schematic view of a vehicle engine to which an engine control apparatus according to a third embodiment is applied. In the first embodiment, the lift center angle of the exhaust valve 3b is not changed, and the pump loss (friction torque) is changed by changing the lift center angle of the intake valve 2b by the phase variable mechanism. Both lift center angles of the intake valve 2b and the exhaust valve 3b are changed. In FIG. 12, the valve drive mechanisms 2c and 3d for opening and closing the intake valve 2b and the exhaust valve 3b are both provided with phase variable mechanisms so that the lift center angle can be changed.
[0042]
In this embodiment, as shown in FIG. 13, until the engine speed N reaches the control start speed Ns, the lift center angles of the intake valve 2b and the exhaust valve 3b are set to θ1 and θ4, respectively. The overlap is φ1 which is larger than that during normal operation. Thereafter, when the engine speed N reaches the control start speed Ns, the lift center angle of the intake valve 2b is retarded to θ3, the lift center angle of the exhaust valve 3b is advanced to θ5, and the valve overlap is increased from φ1. By reducing the diameter to φ2, the same effect as the above embodiment can be obtained.
[0043]
The flowchart of the engine start control of this embodiment is substantially the same as the flowchart shown in FIGS. However, in the present embodiment, the lift center angles θ3 and θ5 of the intake valve 2b and the exhaust valve 3b are obtained as target valve timings in step S9, and the lift center angles of the intake valve 2b and the exhaust valve 3b are determined as θ3 and step S10 in step S10. Set to θ5. In step S12, the valve center timing at start is set to the lift center angles θ1 and θ4 of the intake valve 2b and the exhaust valve 3b. In step S15, the valve timings during normal operation are set to the lift center angles θ1 and θ4 of the intake valve 2b and the exhaust valve 3b.
[0044]
In the present embodiment, since the valve overlap is changed by simultaneously changing both the lift center angles of the intake valve 2b and the exhaust valve 3b, the case of the first embodiment in which only the lift center angle of the intake valve 2b is changed. The overlap can be changed in a shorter time. Therefore, the control start rotational speed Ns can be set higher than in the first embodiment, the engine rotational speed N is increased for a longer period of time, and the intake negative pressure Pb is further developed. As a result, the amount of HC emission can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vehicle engine to which an engine control apparatus according to a first embodiment is applied.
FIG. 2 is an explanatory diagram of valve timing according to the first embodiment.
FIG. 3 is a flowchart of engine start control.
FIG. 4 is a flowchart for calculating an estimated peak rotational speed Np.
FIG. 5 is a flowchart for calculating a control start rotation speed Ns.
FIG. 6 is an explanatory diagram of a method for calculating an estimated peak rotational speed Np.
FIG. 7 is a time chart showing changes in characteristic values when the engine is started.
FIG. 8 is a time chart showing changes in characteristic values at the time of engine start.
FIG. 9 is a map showing the sensitivity of friction torque to valve overlap.
FIG. 10 is a schematic diagram of a vehicle engine to which an engine control device according to a second embodiment is applied.
FIG. 11 is an explanatory diagram of valve timing according to the second embodiment.
FIG. 12 is a schematic diagram of a vehicle engine to which an engine control apparatus according to a third embodiment is applied.
FIG. 13 is an explanatory diagram of valve timing according to the third embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine body 2 Intake passage 2a Intake port 2b Intake valve 2c Valve drive mechanism 2d Electromagnetic drive mechanism 3 Exhaust passage 3a Exhaust port 3b Exhaust valve 3c Valve drive mechanism 4 Air cleaner 5 Air flow meter 6 Throttle valve 6a Throttle sensor 7 Collector 8 Fuel injection valve 9 Ignition coil 10 Spark plug 11 Crank angle sensor 12 Water temperature sensor 13 Control unit (ECU)
14 Bypass passage 14a Idle control valve 18 Starter switch 19 Starter motor 20 Intake air temperature sensor

Claims (5)

An engine control device capable of changing a valve overlap of an intake valve and an exhaust valve,
Condition determining means for determining whether or not the engine speed has exceeded a predetermined speed after the start of the engine;
When starting the engine, set the valve timing of the intake valve or exhaust valve so that the valve overlap is larger than that during normal operation, and when the specified conditions are met, the valve overlap is smaller than when starting the engine. And a valve control means for setting the valve timing of the intake valve or the exhaust valve so that
The predetermined rotational speed in the condition determining means is set based on the estimated peak rotational speed in the engine operating state before satisfying the predetermined condition and the upper limit target rotational speed that is a limit engine rotational speed that does not deteriorate the engine operability. , the engine control unit. The engine control apparatus according to claim 1 , wherein the estimated peak rotational speed is estimated based on an engine rotational speed, a rotational speed increase speed, and an engine load. The engine control apparatus according to claim 2 , wherein the estimated peak rotational speed is further estimated based on the water temperature. The engine control apparatus according to claim 2 or 3 , wherein the estimated peak rotational speed is further estimated based on an intake air temperature. The engine control device according to any one of claims 1 to 4 , wherein the valve control means returns the valve timing of the intake valve or the exhaust valve so that the valve overlap becomes large again after setting the valve overlap small.

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