JP2008267362A - Knocking control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize operating conditions of an engine while inhibiting knocking even if an environmental conditions influencing the control of the engine changes. <P>SOLUTION: This knocking control device for the engine 10 provided with a variable valve timing mechanism 11 for an intake valve, is provided with a valve timing determination part 54 determining valve timing of the intake valve and a knocking detection part 52 detecting knocking. When knocking is detected, the valve timing determination part 54 shifts valve timing of the intake valve in a direction reducing intake air quantity to a combustion chamber of the engine 10 by predetermined quantity to reduce filling efficiency in to the combustion chamber. Consequently, knocking can be inhibited even if trace knock ignition timing is shifted to an advancing side and knocking occurs due to change of the environment condition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a knocking control device that suppresses engine knocking.

Since the optimum engine operating conditions vary depending on the properties of the fuel, atmospheric conditions, and the like, there is a need for an engine control apparatus that can cope with any conditions.
One of the engine control items is ignition timing. When the ignition timing is advanced, the thermal efficiency improves according to the amount of advancement until the ignition timing (MBT: Minimum Advance For the Best Torque) at which the engine generates the maximum torque. improves. However, there are concerns about the occurrence of knocking.

In Patent Document 1, when knocking is detected by a knock sensor, the ignition timing is greatly retarded, and after the retarded timing, the ignition timing is gradually advanced until knocking is detected again. It is disclosed that the operating condition of the engine is optimized by repeatedly retarding and advancing the ignition timing, such that the ignition timing is greatly retarded when detected.
JP 2005-127154 A

However, in the case of the device disclosed in Patent Document 1, since the ignition timing is repeatedly changed, the fuel consumption and output of the engine are reduced due to excessive retardation of the ignition timing until the optimal ignition timing is reached. Arise. Therefore, there is a problem that drivability deteriorates.
Further, in the case of such a control method, there is a concern about engine damage due to knocking.

  Therefore, an object of the present invention is to provide an engine knock control device capable of optimizing operating conditions while suppressing the occurrence of knocking without causing such a problem.

  The present invention is an engine knocking control device having an intake valve timing variable mechanism, comprising: a valve timing determining unit that determines a valve timing of an intake valve; and a knocking detection unit that detects the occurrence of knocking; Is detected, the valve timing determination unit shifts the valve timing of the intake valve by a predetermined amount in a direction in which the amount of intake air into the combustion chamber of the engine decreases.

According to the present invention, when the occurrence of knocking is detected by the knocking detection unit, the valve timing of the intake valve is shifted by a predetermined amount in a direction in which the amount of intake air into the combustion chamber of the engine decreases. The amount of air supplied to the is reduced.
When the amount of air in the combustion chamber decreases, the fuel and air charging efficiency in the combustion chamber decreases, and therefore, the limit ignition timing at which knocking occurs (trace knock ignition timing) is shifted to the advance side by the decreased amount. As a result, the ignition timing at the time of occurrence of knocking is positioned more retarded than the trace knock ignition timing after the shift, so the degree of knocking is reduced according to the shift amount of the trace knock ignition timing. Or knocking is eliminated.
Further, since the air-fuel ratio is fixed, when the amount of air supplied into the combustion chamber of the engine decreases, the fuel supplied into the combustion chamber also decreases. Therefore, the fuel consumption is reduced, and the fuel efficiency of the engine is improved.

Hereinafter, the knocking control apparatus according to the present embodiment will be described.
FIG. 1 is an explanatory diagram illustrating the configuration of the knocking control device according to the present embodiment.
The knocking control device includes an engine 10 that includes a variable valve timing mechanism 11 for an intake valve, and an ECU 50 that has a function of controlling the valve timing of the engine 10. An air flow sensor 30 and an electronic control throttle 40 are provided in the intake passage 20 of the engine 10 in order from the upstream side.

  The air flow sensor 30 is a sensor that measures the amount of air that passes through the intake passage 20, generates an electrical signal (intake air amount signal) corresponding to the measured amount of air, and outputs the electrical signal to the ECU 50.

The electronically controlled throttle 40 adjusts the amount of air taken into the engine 10 through the intake passage 20 by opening and closing a throttle valve (not shown).
The air amount is adjusted by opening and closing the throttle valve by a throttle motor (not shown) based on a throttle drive signal input from the ECU 50.
The electronic control throttle 40 has an opening sensor (not shown) that detects the opening of the throttle valve, and the opening sensor is an electric signal (throttle position signal) corresponding to the detected opening of the throttle valve. Is generated and output to the ECU 50.

The variable valve timing mechanism 11 opens and closes an intake valve and an exhaust valve (not shown) of the engine 10 according to a drive signal input from the ECU 50, and changes the opening and closing timing of at least one of the intake valve and the exhaust valve as necessary. Let
Further, the position of the intake valve is detected by a sensor (not shown), an electric signal (VTC position signal) is generated according to the detected position of the intake valve, and is output to the ECU 50.

The ECU 50 controls the engine so as to provide an optimum driving state based on environmental conditions specified by detection signals from various sensors, and includes a storage unit 51, a knocking detection unit 52, and environmental condition estimation. Unit 53, valve timing determination unit 54, and signal generation unit 55.
In addition to the intake air amount signal output from the airflow sensor 30, the throttle position signal output from the electronic control throttle 40, and the VTC position signal input from the valve timing variable mechanism 11, the ECU 50 receives from the knocking sensor 60. And the signal from the engine speed sensor 70 are input.

The storage unit 51 stores and holds programs for performing various controls performed by the ECU 50, calculation data (basic control map 51a, environmental condition index table 51b), data calculated when the control is executed, and the like.
The basic control map 51a is a map that defines the opening / closing timing of the intake valve and exhaust valve of the engine, the ignition timing of the spark plug, the fuel injection amount, the air-fuel ratio, and the like. This basic control map is prepared for each different environmental condition (for example, octane number, temperature / humidity, etc.), and each basic control map defines an operating condition that can provide an optimal operating state in each environmental condition. .

The environmental condition index table 51b is a table that defines the relationship between the engine speed N, the amount of change Tp of the intake air volume index Q with respect to the engine speed N (ΔTp), and the environmental condition index.
Note that the detailed description of the environmental condition index table 51b will be given in the description of the processing performed by the ECU 50 when knocking described later is detected.

The knocking detection unit 52 determines whether or not knocking has occurred based on the detection value of the knocking sensor 60.
The environmental condition estimation unit 53 estimates environmental conditions that affect engine control such as atmospheric conditions, octane number, temperature / humidity, and the like based on detection signals from various sensors.

The valve timing determination unit 54 selects a predetermined basic control map from among a plurality of basic control maps 51a stored in the storage unit 51 at the time of engine startup or the like.
In addition, when knocking is detected by the knocking detection unit 52, a basic control map that can provide an optimum driving state is selected based on the environmental conditions estimated by the environmental condition estimation unit 53.

When the basic control map is selected, the signal generation unit 55 is configured to drive the intake and exhaust valves of the engine 10 according to the conditions defined in the selected basic control map, and the throttle valve of the electronic control throttle 40. A throttle drive signal for instructing the opening and closing of the engine and its degree, and an ignition signal for instructing ignition of the mixed gas in the combustion chamber.
And it outputs to the valve timing variable mechanism 11, the electronic control throttle 40, and the ignition plug of the engine 10 at a predetermined timing defined in the basic control map.

A process performed in the ECU 50 when knocking is detected will be described.
FIG. 2 is a flowchart illustrating a process performed in the ECU when knocking is detected.
In step 100, the valve timing determination unit 54 determines whether or not the variable valve timing mechanism 11 is movable within the operating range in the direction of decreasing the intake air amount, that is, changes the valve timing in the direction of decreasing the intake air amount. Confirm whether or not is possible.

If it can be changed in step 100, in step 101, the knocking detection unit 52 determines whether knocking has occurred based on the detection value of the knocking sensor 60.
When it is determined in step 101 that knocking has occurred, in step 102, the valve timing determination unit 54 determines the throttle opening (TVO) and the engine 10 in order to temporarily maintain a predetermined operating state. The ignition timing (ADV) of the spark plug is fixed. As a result, the throttle opening and the ignition timing of the ignition plug of the engine 10 are fixed, so that the engine 10 is held in a predetermined operating state.

  In Step 103, the valve timing determination unit 54 multiplies the engine speed N acquired from the detection value of the engine speed sensor 70 and the detection value (airflow sensor voltage) of the airflow sensor 30 by a predetermined constant and obtains the intake air. From the quantity index Q, the ratio of the intake quantity index Q to the engine speed N (Tp0: Tp0 = Q / N) is calculated and stored in the storage unit 51.

  In step 104, the valve timing determination unit 54 causes the signal generation unit 55 to generate a drive signal instructing to shift the valve timing by a predetermined amount, for example, 5 degrees, in the direction in which the intake air amount of the engine 10 decreases, thereby varying the valve timing. The mechanism 11 is made to output. As a result, the amount of air (intake amount) supplied into the combustion chamber of the engine 10 decreases by a predetermined amount.

Here, the relationship between the decrease in the intake air amount and the limit ignition timing at which knocking occurs (trace knock ignition timing) will be described.
FIG. 4 is a correlation diagram showing the correlation between the intake air amount (filling efficiency) and the trace knock ignition timing when the engine speed is 4000 rpm.
When the intake air amount to the engine 10 decreases, the charging efficiency in the combustion chamber decreases, and as is apparent from FIG. 4, the trace knock ignition timing is advanced according to the decreasing rate of the charging efficiency.
For example, when the charging efficiency is reduced by about 5 points, the trace knock ignition timing is changed from about 33 deg to 39 deg. That is, it shifts to about 6 deg advance side.
Therefore, if the intake air amount is decreased when the occurrence of knocking is detected, the trace knock ignition timing is shifted to the advance side, so that the ignition timing at that time is retarded from the trace knock ignition timing after the shift. Will be located. As a result, the degree of knocking is reduced or knocking is eliminated according to the shift amount of the trace knock ignition timing.

  Referring to FIG. 2, in step 105, in order to confirm whether knocking has been eliminated due to a decrease in the intake air amount, knocking detection unit 52 determines whether or not the valve timing has been shifted based on the detection value of knocking sensor 60. Determine whether knocking has been resolved.

  If it is determined in step 105 that the knocking has been resolved, referring to FIG. 3, in step 106, the valve timing determination unit 54 determines the engine speed N from the current engine speed N and the intake air amount index Q. The ratio of the intake air amount index Q (Tp1: Tp1 = Q / N) is calculated and stored in the storage unit 51.

In step 107, the environmental condition estimation unit 53 calculates a change amount (ΔTp) of the ratio Tp of the intake air amount index Q to the engine speed N based on the following equation (1).
ΔTp = Tp1-Tp0 (1)
Here, ΔTp is the ratio of Tp (ratio of intake air amount index Q to engine speed N) until knocking can be eliminated after occurrence of knocking is detected and intake air amount adjustment (decrease) is started. It means the amount of change.

In step 108, the environmental condition estimation unit 53 obtains the environmental condition index table 51b stored in the storage unit 51 based on the engine speed N at the time of calculating Tp0 and the Tp variation (ΔTp) obtained in step 107. Refer to and obtain the environmental condition index.
Here, the environmental condition index means an index indicating changes in environmental conditions such as octane number and water vapor partial pressure.

The environmental condition index table 51b will be described.
As shown in FIG. 5, in the environmental condition index table 51b, the engine speed N when knocking is detected, and the intake air volume index Q with respect to the engine speed N from when knocking is detected until knocking is eliminated. The environmental condition index is set from the change amount (ΔTp) of the ratio Tp.
For example, when the engine speed at the time of occurrence of knocking is N3 and the amount of change in Tp required until knocking is eliminated is ΔTpII, the environmental condition index is set to “3”.

Referring to FIG. 3, in step 109, the valve timing determination unit 54 is based on the environmental condition specified by the obtained environmental condition index from the plurality of basic control maps 51 a stored in advance in the storage unit 51. To select a basic control map that can provide the optimal operating conditions.
This is because the engine control based on the currently selected basic control map is an operating condition in which knocking occurs, so that the optimal condition can be obtained under the current environmental conditions specified by the obtained environmental condition index. This is to prevent knocking by newly selecting a basic control map that defines the driving conditions that can provide the driving state and controlling the engine based on the newly selected basic control map.

In step 110, the valve timing determination unit 54 releases the fixed throttle opening (TVO) and ignition timing (ADV).
Thereby, engine control based on the newly selected basic control map is performed.
If the occurrence of knocking is detected after the basic control map is newly selected in step 111, the routine proceeds to engine control for retarding the ignition timing.

Referring to FIG. 2, if it is determined in step 105 that knocking has not been eliminated, it is determined whether or not the valve timing variable mechanism 11 can be controlled so as to further reduce the intake air amount. Therefore, in step 112, the valve timing determination unit 54 confirms whether or not the valve timing change mechanism 11 is movable in the direction in which the intake amount decreases in the operation region.
If it can be changed in step 112, the process proceeds to step 104, and a drive signal is generated to instruct to change the valve timing by 5 deg in the direction in which the intake air amount Q of the engine 10 decreases, and the valve timing is variable. It is output to the mechanism 11.

If it is not possible to change in step 112, the intake air amount cannot be further reduced, and thus the calculation of the environmental condition index and the reselection of the basic control map cannot be performed.
Therefore, in step 113, the valve timing determination unit 54 resets the value of Tp0 stored in the storage unit 51, and in step 114, the valve timing shifted in step 104 is set to the initial state specified in the control map. Return to the valve timing. In step 115, the throttle opening (TVO) and ignition timing (ADV) are released from being fixed.
Thereby, when the occurrence of knocking is detected thereafter, engine control for retarding the ignition timing is performed.
Here, the variable valve timing mechanism 11 in this embodiment corresponds to the variable timing mechanism of the invention, and the basic control map corresponds to the control map of the invention.

As described above, this embodiment is an engine knocking control apparatus including the variable valve timing mechanism 11 for an intake valve, and includes a valve timing determination unit 54 that determines the valve timing of the intake valve, and a knocking that detects the occurrence of knocking. And a valve timing determination unit that shifts the valve timing of the intake valve by a predetermined amount in a direction in which the amount of intake air into the combustion chamber of the engine 10 decreases when the occurrence of knocking is detected. It was.
As a result, when the occurrence of knocking is detected, the amount of air supplied into the combustion chamber of the engine 10 decreases, and the charging efficiency of fuel and air in the combustion chamber decreases. Trace knock ignition timing is shifted to the advance side. As a result, the ignition timing at the time of occurrence of knocking is positioned more retarded than the trace knock ignition timing after the shift, so the degree of knocking is reduced according to the shift amount of the trace knock ignition timing. Or knocking is eliminated.

FIG. 6 is an explanatory diagram showing changes in fuel consumption rate and output when the valve timing is shifted and the charging efficiency is decreased while the ignition timing is fixed, and FIG. 7 is a diagram in the state where the charging efficiency is fixed. It is explanatory drawing which shows the change of a fuel consumption rate and an output with respect to the advance angle change of ignition timing.
As shown in FIG. 6, when the amount of intake air into the combustion chamber of the engine 10 is reduced by changing the conversion amount of the valve timing variable mechanism 11 from the initial value (40 deg CA) to 20 deg CA to shift the valve timing, Efficiency is reduced by about 5 points. Here, since the air-fuel ratio is fixed, the supply amount of fuel decreases from about 300 g / kWh to about 296 g / kWh following the decrease in the air amount accompanying the decrease in the charging efficiency.

Referring to FIG. 7, for example, when the ignition timing is advanced by about 6 deg, the fuel consumption rate decreases from about 300 g / kWh to about 286 g / kWh, and the corrected shaft output increases from about 76 kW to about kW due to the increase in thermal efficiency. It rises to 80 kW.
Therefore, when the occurrence of knocking is detected, if the valve timing of the intake valve is shifted by a predetermined amount in the direction in which the amount of intake air into the combustion chamber of the engine 10 decreases, the fuel consumption rate decreases and fuel consumption improves. In addition, an effect of increasing the output by improving the thermal efficiency due to the advance of the ignition timing can be obtained.
Here, when the conventional control is performed in which the ignition timing is 6 deg retarded when knocking occurs, the output decreases and the combustion consumption rate deteriorates. However, as in the present application, the intake amount is decreased and the trace knock ignition timing is decreased. If the ignition timing is advanced to the maximum, there is no problem as in the case of conventional control.

In addition, an environmental condition estimation unit 53 that estimates environmental conditions (for example, octane number, temperature / humidity, etc.) that affect the control of the engine 10 is further provided, and the valve timing determination unit 54 determines the valve timing until knocking is eliminated. The shift is repeated, and the environmental condition estimation unit 53 estimates the environmental condition based on the amount of change in the intake air amount after the occurrence of knocking is detected and until the knocking is eliminated, and the valve timing determination unit 54 estimates The valve timing is feedback controlled based on the environmental conditions.
As a result, the valve timing is feedback-controlled according to the environmental conditions estimated from the amount of change in the intake air amount until knocking is eliminated, and the engine operating conditions are adjusted, thereby bringing the engine into a more suitable operating state. Can do.

In particular, an environmental condition index is used as an environmental condition, and an environmental condition index table 51b that prescribes the relationship between a change amount (ΔTp) of the ratio Tp of the intake air volume index Q to the engine speed N and the environmental condition index is prepared in advance. Based on the change amount (ΔTp) of the ratio Tp of the intake air amount index Q to the rotational speed N, an index (environmental condition index) indicating a change in the environmental condition is obtained by referring to the environmental condition index table 51b, and the obtained environmental condition index The environmental conditions were estimated from the above.
Accordingly, since the environmental condition can be easily estimated simply by obtaining the change amount (ΔTp), the engine feedback control based on the estimated environmental condition can be quickly performed.

Further, the valve timing determination unit 54 determines the valve timing based on a basic control map prepared in advance, and is prepared in advance for each environmental condition when the environmental condition estimation unit 53 estimates the environmental condition. In addition, the valve timing is determined based on one basic control map selected from a plurality of basic control maps based on the estimated environmental conditions.
As a result, when knocking occurs in engine control based on a basic control map prepared in advance due to a change in environmental conditions, the current environmental conditions are estimated, and a new one is created based on the estimated environmental conditions. A control map is selected.
Therefore, a basic control map that can provide an optimum driving state under the estimated environmental conditions can be newly selected from the plurality of basic control maps 51a stored in the storage unit 51, and knocking can be performed. An operating state that does not occur can be provided.
In addition, when knocking is detected, the environmental conditions are estimated, and a new control map is selected based on the estimated environmental conditions, so that it is possible to provide an optimal operating state while suppressing the occurrence of knocking. Become.

Further, the valve timing determination unit 54 is configured to retard the ignition timing when the valve timing cannot be shifted in a direction in which the amount of intake air into the combustion chamber of the engine 10 decreases.
Thereby, when the intake amount is decreased and the trace knock ignition timing cannot be advanced, the ignition timing is retarded, so that knocking can be eliminated.

In the above embodiment, after selecting a new control map based on the estimated environmental conditions, the engine control for retarding the ignition timing when knocking occurs is described as an example. After selecting the control map, the estimation of environmental conditions and the selection of the basic control map may be repeated each time occurrence of knocking is detected.
This makes it possible to provide an optimal operating state while suppressing the occurrence of knocking even under a situation where environmental conditions frequently change.

It is explanatory drawing explaining the structure of the knocking control apparatus concerning an Example. It is a flowchart explaining a process when knocking is detected. It is a flowchart explaining a process when knocking is detected. FIG. 5 is a correlation diagram showing a correlation between charging efficiency and trace knock ignition timing. It is explanatory drawing explaining an environmental condition index table. It is a correlation diagram which shows the correlation with filling efficiency, valve timing variation | change_quantity, and fuel consumption rate. FIG. 5 is a correlation diagram showing a correlation among charging efficiency, ignition timing advance angle, and fuel consumption rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 11 Valve timing variable mechanism 20 Intake passage 30 Air flow sensor 40 Electronically controlled throttle 50 ECU
DESCRIPTION OF SYMBOLS 51 Memory | storage part 51a Basic control map 51b Environmental condition index table 52 Knocking detection part 53 Environmental condition estimation part 54 Valve timing determination part 55 Signal generation part 60 Knock sensor 70 Engine speed sensor

Claims (4)

An engine knocking control device having a variable timing mechanism of an intake valve,
A valve timing determining unit for determining the valve timing of the intake valve;
A knock detection unit for detecting the occurrence of knocking,
The valve timing determination unit shifts the valve timing of the intake valve by a predetermined amount in a direction in which the amount of intake air into the combustion chamber of the engine is reduced when occurrence of knocking is detected. Knocking control device. An environmental condition estimating unit that estimates an environmental condition that affects engine control;
The valve timing determination unit repeatedly shifts the valve timing until the knocking is eliminated,
The environmental condition estimating unit estimates the environmental condition based on the amount of change in the intake air amount after the occurrence of knocking is detected and until knocking is eliminated,
The engine knock control device according to claim 1, wherein the valve timing determination unit feedback-controls the valve timing based on the estimated environmental condition. The valve timing determination unit determines valve timing based on a control map prepared in advance, and when the environmental condition is estimated by the environmental condition estimation unit, a plurality of controls prepared in advance for each environmental condition 3. The engine knock control apparatus according to claim 2, wherein the valve timing is determined based on one control map selected from the map based on the estimated environmental condition. The valve timing determining unit retards the ignition timing when the valve timing is within a range in which the amount of intake air into the combustion chamber of the engine cannot be shifted. The engine knocking control device according to any one of claims 1 to 3.

Images