JP2004353611A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately switch ignition timing, fuel injection timing and fuel injection quantity accompanying the switching of valve lift characteristics of a variable valve mechanism. <P>SOLUTION: An internal combustion engine including the variable valve mechanism 2 having a plurality of different valve lift characteristics and selecting valve lift characteristics according to an operation condition is provided with a lift switching command means 6 issuing switch command of the valve lift characteristics according to the operation condition, a seating vibration detection means 5 detecting seating vibration of valves 9, 10, an actual valve switch determination means 6 comparing frequency component of the seating vibration and strength, a means measuring switch delay time based on signal from the lift switching command means 6 and determination result of the actual valve switch determination means 6, and a combustion control variable switch means 6 determining switch of combustion control variable based on the switch delay time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to control of an internal combustion engine having a variable valve mechanism that variably controls the operation (lift) characteristics of intake and exhaust valves according to an operating state, and particularly to ignition timing and fuel injection timing accompanying switching of the variable valve mechanism. And so on.
[0002]
[Prior art]
The internal combustion engine requires contradictory characteristics of high torque during low-speed operation and high output during high-speed operation. As a technology that satisfies both of these requirements, a low-speed camshaft with a lift characteristic that emphasizes torque performance and a high-speed camshaft with a lift characteristic that emphasizes output performance are provided. There is known a so-called variable valve mechanism that switches the lift characteristic of an intake valve or an exhaust valve to a valve suitable for an operation state by properly using a shaft.
[0003]
In Patent Document 1, a vibration sensor is provided in an internal combustion engine, a frequency analysis of valve seating vibration is performed based on a detection signal detected by the vibration sensor, and a current low-speed camshaft or high-speed camshaft is determined based on the intensity of the frequency component. A technique for diagnosing which is operating is disclosed.
[0004]
[Patent Document 1]
JP-A-7-238822 [0005]
[Problems to be solved by the present invention]
However, Patent Document 1 discloses only the diagnosis of which of the low-speed camshaft and the high-speed camshaft is operating, and does not disclose any camshaft switching operation. However, in the actual operation state, the intake air amount changes due to the switching of the valve lift characteristics, and accordingly, it is necessary to switch the ignition timing, the fuel injection timing, the fuel injection amount, and the like. If these switching timings deviate, the air-fuel ratio becomes excessively rich or thin and knocking or shock occurs, leading to a reduction in drivability. Therefore, it is important to diagnose the timing at which the valve lift characteristics are switched.
[0006]
In view of the above, an object of the present invention is to provide a control device capable of accurately detecting a timing of switching a camshaft and performing switching of an ignition timing, a fuel injection timing, and a fuel injection amount with high accuracy. I do.
[0007]
[Means for Solving the Problems]
The control device for an internal combustion engine according to the present invention has a variable valve mechanism that has a plurality of different valve lift characteristics and switches the valve lift characteristics according to operating conditions. Lift switching command means for issuing a switching command for valve lift characteristics, seat vibration detecting means for detecting seat vibration of the valve, actual valve switching determining means for comparing frequency components and intensity from the seat vibration detecting means, and the lift Means for setting a switching delay time based on a signal from the switching command means and a determination result from the actual valve switching determining means; and a combustion control amount switching means for determining switching of a combustion control amount based on the switching delay time. And
[0008]
[Action / Effect]
According to the present invention, the actual switching timing of the valve lift characteristic is detected using the seating vibration of the valve detected by the seating vibration detecting means, and based on this, the ignition timing, the fuel injection timing, the fuel injection amount, etc. Since the switching of the combustion control amount other than the air amount is performed, it is possible to accurately match the valve lift characteristics and the switching timing of the combustion control amount, and it is possible to prevent knocking and shock caused by the above-described switching timing shift. It becomes possible.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a schematic diagram of the system of the present invention.
[0011]
Reference numeral 1 denotes an internal combustion engine (engine), which includes a variable valve mechanism 2 that can variably control lift characteristics of an intake valve 9 and an exhaust valve 10 according to an operation state.
[0012]
The engine 1 includes a crank angle sensor 4 for detecting a rotation angle of the crankshaft 3, a knock sensor 5 for detecting vibration of the engine 1, a cam sensor 24 for detecting a rotation angle of the intake camshaft 7 or the exhaust camshaft 8, and the like. These detection signals are read into a control unit (ECU) 6.
[0013]
In addition to the above sensors, the ECU 6 reads detection signals from, for example, a water temperature sensor for detecting a cooling water temperature, a rotation speed sensor for detecting an engine speed, and a vehicle speed sensor for detecting a running speed of the vehicle.
[0014]
The ECU 6 controls the amount of air supplied to the engine 1 by changing the lift characteristics of the variable valve mechanism 2 on the basis of the detection values of the above-mentioned sensors, and is capable of instantaneously switching ignition timing, fuel injection timing, and fuel injection amount. The control of the combustion control amount contributing to combustion other than the air is performed.
[0015]
FIG. 2 is a schematic diagram of a system of the variable valve mechanism 2. FIG. 2 is merely an example of the variable valve mechanism 2, and the variable valve mechanism 2 to which the present embodiment can be applied is not limited to the following.
[0016]
In the present system, since the intake side and the exhaust side have the same mechanism, the description will be made using the intake side mechanism.
[0017]
The intake camshaft 7 is provided with a cam having a high lift / high working angle high speed cam 18 in the center and a low lift / low working angle low speed cam 17 on both sides thereof.
[0018]
The rocker shaft 12 is provided with a rocker arm 14 having a low-speed follower 15 in contact with the low-speed cam 17 and a sub rocker arm 23 having a high-speed follower 16 in contact with the high-speed cam 18. The vicinity of the end of the rocker arm 14 opposite to the rocker shaft 12 is in contact with the upper end of the valve stem 9a of the intake valve 9.
[0019]
A rocker arm 14 is rotatably mounted on the rocker shaft 12 around the rocker shaft 12, and a sub rocker arm 23 is rotatably mounted on a shaft 31 parallel to the rocker shaft 12.
[0020]
Accordingly, when the intake camshaft 7 rotates, the low-speed follower 15 and the high-speed follower 16 move up and down according to the profiles of the low-speed cam 17 and the high-speed cam 18, respectively, so that the rocker arm 14 and the sub rocker arm 23 rotate around their respective axes. I do. Then, only the movement of one of the rocker arm 14 and the sub rocker arm 23 is transmitted to the intake valve 9 by the switching mechanism described later.
[0021]
Here, the switching mechanism between the low-speed cam 17 and the high-speed cam 18 will be described.
[0022]
An oil passage 13 is provided inside the rocker shaft 12, and this oil passage 13 is connected to an oil pump 24, and a solenoid 11 that is ON / OFF controlled by the ECU 6 is provided in the middle of the oil passage 13.
[0023]
3 and 4 are detailed views around the cam switching mechanism when the low-speed cam is selected and when the high-speed cam is selected, respectively.
[0024]
The lower surface of the sub rocker arm 23 is provided with a lost motion mechanism 19 composed of an elastic member such as a spring. The lost motion mechanism 19 absorbs the movement of the sub rocker arm 23 by the expansion and contraction of the spring. Therefore, when the lost motion mechanism 19 is functioning, the movement of the sub rocker arm 23 driven by the high-speed cam 18 is absorbed and is not transmitted to the rocker arm 14.
[0025]
A concave portion communicating with the oil passage 13 is provided on a side surface of the rocker shaft 12 on the intake valve 9 side, and the hydraulic plunger 22 is housed therein. The hydraulic plunger 22 projects from the recess when the hydraulic pressure of the oil passage 13 is applied.
[0026]
The tip 22 a of the hydraulic plunger 22 is in contact with the vicinity of one end of the lever 20. The lever 20 is rotatable around a shaft 30 provided on the rocker shaft 12 and parallel to the rocker shaft 12. When one end is pushed by the hydraulic plunger 22, the lever 20 rotates around the shaft 30. At this time, the other end located at a position substantially opposite to the one end with the shaft 30 interposed therebetween is engaged with a notch 32 provided on the lower surface of the sub rocker arm 23. As a result, the lost motion mechanism 19 does not function, and the rocker arm 14 and the sub rocker arm 23 are connected. When no hydraulic pressure is applied to the hydraulic plunger 22, the hydraulic plunger 22 is pressed by the return spring 21 in a direction of pressing the hydraulic plunger 22 against the concave portion. At this time, the other end does not engage with the notch 32 of the seat rocker arm 23, and the rocker arm 14 and the sub rocker arm 23 are not connected.
[0027]
In the variable valve mechanism 2 configured as described above, when the low-speed cam 17 is selected, the solenoid 11 is turned off, and the oil passage 13 to the rocker shaft 13 is closed. Therefore, as shown in FIG. 3, the hydraulic pressure is not applied to the hydraulic plunger 22, the lever 20 is pushed by the return spring 21, and the rocker arm 14 and the sub rocker arm 23 are in a non-coupled state. Therefore, the lift difference between the low speed cam 17 and the high speed cam 18 is absorbed by the lost motion mechanism 19, and the low speed cam 17 acts on the rocker arm 14.
[0028]
When the high-speed cam is selected, the solenoid 11 is turned ON, the oil passage 13 to the rocker shaft 12 is opened, and the lever 20 is pushed by the hydraulic plunger 22 as shown in FIG. Be combined.
[0029]
As a result, the lift difference between the low-speed cam 17 and the high-speed cam 18 is not absorbed by the lost motion mechanism 19, so that the high-speed cam 18 acts on the rocker arm 14.
[0030]
In the variable valve mechanism 2 described above, the switching condition of the low-speed cam 17 and the high-speed cam 18 is, for example, that the solenoid 11 is turned on when the cooling water temperature is 60 degrees or more on the intake side, the vehicle speed is 30 km / h, and the engine speed is about 5600 rpm or more. On the exhaust side, it is determined that the solenoid 11 is turned on when the cooling water temperature reaches 60 degrees, the vehicle speed reaches 30 km / h, and the engine speed reaches about 6700 rpm.
[0031]
Next, the operation of the variable valve mechanism 2 at the time of switching will be described with reference to the time chart of FIG.
[0032]
When a signal for switching the valve lift characteristic (switching from the low-speed cam 17 to the high-speed cam 18 or vice versa) is output at T1, a delay (response delay time) occurs due to the operation time of the solenoid 11 and the hydraulic plunger 22. It is at T2 that the cam is actually switched. The ignition timing, fuel injection timing, and the like are changed in accordance with the switching of the cam. However, since the switching operation is completed only by switching the electric signal, the response speed is high with respect to the switching of the valve lift characteristics. Therefore, the switching signal is transmitted at T2 when the response delay time elapses after the switching signal of the valve lift characteristic is transmitted.
[0033]
However, the response delay time varies depending on factors such as a decrease in oil pressure due to deterioration of oil and aging of the oil pump 24, and the switching may be terminated at T3 or T4. As a result, if there is a difference between the switching of the ignition timing, the fuel injection amount, and the like and the switching of the valve lift characteristics, knocking, shock, and the like will occur.
[0034]
Therefore, the ECU 6 corrects the ignition timing, the fuel injection amount, and the like based on the actual delay time in order to eliminate the shift between the switching of the ignition timing, the fuel injection amount, and the like and the switching of the valve lift characteristics. FIG. 6 shows a flowchart of the control performed by the ECU 6.
[0035]
In step S100, it is determined whether or not a switching signal of the valve lift characteristic has been input. This can be determined, for example, based on whether the above-described switching condition of the valve lift characteristic is satisfied and the ECU 6 inputs a switching signal to the solenoid 11.
If the switching signal has not been input, the routine ends. If the switching signal has been input, the process proceeds to step S101, in which the timer for measuring the response delay time provided in the ECU 6 is started to start counting, and the process proceeds to step S102.
[0036]
In step S102, the ECU 6 reads signals from the crank angle sensor 4, the coolant temperature sensor, the vehicle speed sensor, the engine speed sensor, and the like, and the signal from the knock sensor 5, which is the valve seat vibration detecting means of the present embodiment.
[0037]
In step S103, a crank angle and a top dead center (TDC) are calculated from the crank angle sensor signal read in step S102.
[0038]
In step S104, a frequency analysis of the vibration of the engine 1 is performed based on the signal from the knock sensor 5 read in step S103.
[0039]
Specifically, the frequency component of the detection signal of the knock sensor 5 and its intensity are calculated by a frequency detection unit having an analog filter, a digital filter, an FFT, a Wavelet, and the like provided in the ECU 6.
[0040]
In step S105, the closing / seat timing of the intake valve 9 and the exhaust valve 10 is calculated based on the crank angle and TDC calculated in step S103, and the frequency component and its strength calculated in step S104. This makes it possible to know which of the low-speed cam 17 and the high-speed cam 18 is currently being driven.
[0041]
In step S106, it is determined whether or not the valve lift characteristics have actually been switched. This can be determined from the switching signal of the valve lift characteristic input in step S100 and the closing / seating timing calculated in step S105. For example, if a switching signal from the low-speed cam 17 to the high-speed cam 18 is input in step S100 and if it is determined in step S105 that the high-speed cam 18 is currently being driven, it can be determined that the valve lift characteristics have been switched. . If it has been switched, the process proceeds to step S107, in which the counting of the timer for measuring the delay time is stopped, and then the process proceeds to step S108. The delay time measured by the timer is stored as a learning value in the ECU 6 in step S112 described later. If the valve lift characteristics have not been switched, the process returns to step S102.
[0042]
In step S108, the time from when the oil passage 13 switching signal is input to the solenoid 11 to when the actual valve lift characteristics are switched, that is, the actual response delay time is calculated, and the difference between this and the initial response value (actual response delay) is calculated. Then, the process proceeds to step S109. Note that the response delay time initial value is a value in which the response delay time detected by the same method during the previous operation is stored in the ECU 6. Therefore, assuming that the initial value of the response delay time is T2 in FIG. 5, the actual operation variation is represented by T4-T2 and T3-T2.
[0043]
In step S109, it is determined whether or not the magnitude of the actual operation variation obtained in step S108 is within a predetermined range. If it is within the predetermined range, the routine is terminated as it is. Proceed to S110. It should be noted that the predetermined range is set by previously examining a range that is small enough to allow knocking or shock due to deviation of the valve lift characteristic switching timing from the fuel injection timing and the like. This makes it possible to reduce the calculation load.
[0044]
In step S110, the switching timing such as the ignition timing and the fuel injection amount is corrected based on the difference (correction allowance) between the initial value of the response delay calculated in step S108 and the actual response delay time.
[0045]
This makes it possible to switch the ignition timing, the fuel injection amount, and the like at an appropriate timing according to the switching timing of the valve lift characteristics.
[0046]
In step S111, the difference (correction allowance) between the initial value of the response delay calculated in step S108 and the actual response delay time is stored in the ECU 6. The difference (correction allowance) between the initial value of the response delay at the previous switching and the actual response delay time is already stored in the ECU 6, but is overwritten with the current value.
[0047]
In step S112, the actual response delay time detected this time is stored in the ECU 6 as a new response delay initial value, and the routine ends. Note that, similarly to step S111, the already stored value is overwritten with the current value.
[0048]
In steps S111 and S112, the difference (correction allowance) between the initial value of the response delay and the actual response delay time and the initial value of the response delay are overwritten by the actual measurement value this time, so that the response due to the deterioration of the engine oil, the oil pressure drop of the oil pump, etc. Even if a change occurs in the delay time, it is possible to switch the ignition timing and the like corresponding to the change.
[0049]
As described above, in the present embodiment, the actual switching timing of the valve lift characteristic is accurately detected, and the combustion control amount other than air that contributes to combustion, such as the ignition timing and the fuel injection amount, is corrected accordingly. It is possible to switch the ignition timing, fuel injection amount, etc. at an appropriate timing according to the switching of the valve lift characteristics, and knocking or shock caused by a shift in the switching timing between the valve lift characteristics and the combustion control amount other than air is shifted. Occurrence can be prevented.
[0050]
Further, the difference (correction allowance) between the initial value of the response delay and the actual response delay time is stored as a learning value and reflected at the next switching, so that the valve lift characteristic is switched due to, for example, deterioration of the engine oil or oil pressure of the oil pump. Even if the response delay time that occurs sometimes changes, it is possible to switch the ignition timing, fuel injection amount, and the like corresponding to the change.
[0051]
Since the knock sensor 5 also provided in the conventional engine 1 is used for detecting the seating vibration, it is not necessary to add a new sensor for this embodiment.
[0052]
The difference (correction allowance) between the initial value of the response delay and the actual response delay time stored in the ECU 6 is not limited to one, but may be different for each operating condition of the engine, for example, for conditions such as rotation speed, load, oil temperature, and the like. A plurality may be stored. As a result, it is possible to set a more appropriate initial value of the response delay time according to the operating state of the engine, and it is also possible to more appropriately switch the ignition timing, the fuel injection amount, and the like.
[0053]
It is needless to say that the present invention is not limited to the above embodiment, and various changes can be made within the scope of the technical idea described in the claims.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a system configuration according to a first embodiment.
FIG. 2 is a schematic view of a variable valve mechanism.
FIG. 3 is a detailed view of a variable valve mechanism when a low-speed cam is acting.
FIG. 4 is a detailed view of a variable valve mechanism when a high-speed cam is acting.
FIG. 5 is a time chart showing a valve timing switching operation.
FIG. 6 is a control flowchart of the first embodiment.
[Explanation of symbols]
Reference Signs List 1 engine 2 variable valve mechanism 3 crankshaft 4 crank angle sensor 5 knock sensor 6 control unit (ECU)
7 Intake camshaft 8 Exhaust camshaft 9 Intake valve 10 Exhaust valve 11 Solenoid 12 Rocker shaft 13 Oil passage 14 Rocker arm 15 Low speed follower 16 High speed follower 17 Low speed cam 18 High speed cam 19 Lost motion mechanism 20 Lever 21 Return spring 22 Plunger 23 Sub rocker arm 24 oil pump

Claims (3)

An internal combustion engine having a plurality of different valve lift characteristics and having a variable valve mechanism that switches the valve lift characteristics according to operating conditions,
Lift switching command means for issuing a switching command of the valve lift characteristic to the variable valve mechanism according to an operation state;
Seating vibration detecting means for detecting seating vibration of the valve,
Actual valve switching determining means for comparing the frequency component and the intensity from the seating vibration detecting means,
Means for setting a switching delay time based on a signal from the lift switching command means and a determination result from the actual valve switching determining means,
A control device for an internal combustion engine, comprising: combustion control amount switching means for determining switching of a combustion control amount based on the switching delay time. 2. The control device for an internal combustion engine according to claim 1, wherein the switching delay time is stored as a learning value, and the learning value is updated every time a valve lift characteristic switching operation is performed. 3. The control device for an internal combustion engine according to claim 2, wherein a plurality of the learning values are provided in accordance with an operation state of the internal combustion engine.

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