JP2528159B2 - Ignition timing control device for variable compression ratio internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device for a variable compression ratio internal combustion engine in which a compression ratio is variably controlled according to engine operating conditions.

2. Description of the Related Art Various variable compression ratio internal combustion engines have been conventionally proposed in order to achieve both improvement in thermal efficiency at low load and suppression of knocking at high load. For example,
In Japanese Utility Model Laid-Open No. 58-25637, the piston of each cylinder has a dual structure of an inner piston and an outer piston, and the compression ratio is changed by moving the outer piston up and down with respect to the inner piston. A compression ratio variable mechanism, and in Japanese Patent Laid-Open No. 60-230548, a sub cylinder is formed in a cylinder head, and the sub piston is moved up and down in the sub cylinder to change the compression ratio. Each variable mechanism is described.

In this variable compression ratio type internal combustion engine, the compression ratio variable mechanism is switched and controlled according to the engine operating conditions, mainly the load, and is generally in a high compression ratio (hereinafter abbreviated as high ε) state in a low load region. In the high load region, the state is controlled to a low compression ratio (hereinafter abbreviated as low ε) state.

On the other hand, the ignition timing of the internal combustion engine is controlled based on, for example, a data map using the engine speed and the load as parameters, but in the variable compression ratio internal combustion engine, the data in the data map, that is, the optimum ignition timing is As a matter of course, the compression ratio at that time is preliminarily determined in accordance with the required ignition timing. In other words, in the low ε state, it is possible to advance the ignition timing to some extent as compared with the case of the high ε state. Therefore, the engine operating condition is in the low ε region (the region controlled to be low ε, that is, the high load state is generally used. In (), the ignition timing is set to the characteristic on the leading side as a whole, and in the high ε region (a region controlled to a high ε, that is, a generally low load state), the characteristic is set to the delay side as a whole. FIG.
An example of the basic ignition timing characteristic (which is substantially equal to the required ignition timing characteristic) set corresponding to the load at a certain engine speed is shown together with the compression ratio characteristic. That is, the basic ignition timing characteristic is a characteristic in which the required ignition timing characteristic for low ε and the required ignition timing characteristic for high ε are connected at the compression ratio switching point.

Therefore, at the time of acceleration of the internal combustion engine, the ignition timing characteristic is switched from the high ε characteristic to the low ε characteristic as shown in FIG. 12 as the compression ratio is switched, and the ignition timing changes stepwise. Conversely, during deceleration, the characteristic for low ε is switched to the characteristic for high ε, and the ignition timing also changes stepwise.

Problems to be Solved by the Invention The ignition timing of the variable compression ratio internal combustion engine as described above is set on the assumption that the compression ratio is stably maintained at a predetermined value.

However, in order for the compression ratio variable mechanism operated by hydraulic pressure or the like to completely shift from the high ε state to the low ε state or from the low ε state to the high ε state, as shown in FIG.
It takes some time after the operating conditions change.

Therefore, during a transition of the internal combustion engine, the change in the compression ratio cannot follow the change in the ignition timing due to the switching of the characteristics. As a result, for example, during acceleration, the ignition timing is temporarily advanced too much, which may cause strong knocking.
Further, during deceleration, the ignition timing is temporarily delayed too much, which may lead to a reduction in output and a deterioration in drivability.

By the way, the actual compression ratio of the internal combustion engine may be slightly different due to an assembly error of each internal combustion engine, a variation in the thickness of the cylinder head gasket, and the like. Also, in the same internal combustion engine, the compression ratio may differ slightly for each cylinder. In such a case, the extent to which the ignition timing is advanced or delayed too much during acceleration or deceleration is not constant. For example, if the actual compression ratio at high load is higher than the desired low ε state, the degree of excessive advance during acceleration will be large, and conversely if it is lower than the desired low ε state, acceleration will occur. The degree of over-advancement over time decreases.

Therefore, it is not possible to sufficiently eliminate such a temporary shift of the ignition timing by simply adding a certain correction during the transition of acceleration and deceleration.

Means for Solving the Problems The present invention has been made to solve the problems as described above, and can be achieved under both high load and low load conditions where the starting point and the reaching point of the change of the compression ratio at the transition time. The actual compression ratio is estimated from the actual ignition timing under each condition, and the ignition timing at the initial stage of the transient time is corrected in consideration of variations in the actual compression ratio. That is,
As shown in FIG. 1, an ignition timing control device for a variable compression ratio internal combustion engine according to the present invention has a variable compression ratio internal combustion engine in which a compression ratio is variably controlled in accordance with engine operating conditions. Accordingly, the basic ignition timing setting means 8 for setting the basic ignition timing, the knocking detection means 1 for detecting the presence or absence of knocking of the engine, the basic ignition timing which is selected when there is no knocking, and the basic ignition timing is corrected to set the ignition timing. MBT control means 2 for controlling the MBT point, and knocking control means 3 for controlling the ignition timing to the knocking occurrence limit by correcting the basic ignition timing when the knocking is present.
And a compression ratio detecting means 4 for estimating the actual compression ratio under high load conditions and the actual compression ratio under low load conditions from the ignition timing when the engine is in a steady state, and the transient based on the difference between the two compression ratios. A correction amount setting means 5 for setting an initial correction amount at the time, a transient detection means 6 for detecting an engine transient state, and a correction means 7 for correcting the ignition timing based on the initial correction amount at the time of detecting the transient are provided. It is configured.

When the occurrence of knocking is detected by the knocking detection means 1, the knocking control means 3 gradually corrects the ignition timing so that the ignition timing is finally kept at the knocking occurrence limit. Further, in a situation where knocking does not occur, the ignition timing is finally kept at the MBT point (the minimum advance position for obtaining the maximum torque) by the MBT control means 2. That is, if the internal combustion engine is in a steady state, the ignition timing is always maintained at the MBT point or the knocking occurrence limit. The MBT control and the knocking control of this type are known from JP-A-58-82074 and JP-A-62-96779.

Then, the ignition timing at this time changes depending on the actual compression ratio. That is, if the compression ratio is high, it is relatively retarded, and if the compression ratio is low, it is relatively retarded. Therefore, the actual compression ratio can be estimated from the relationship between the reference ignition timing corresponding to the operating condition at that time and the actual ignition timing. Specifically, the actual compression ratio under high load conditions is estimated based on the ignition timing under high load conditions, and the actual compression ratio under low load conditions is estimated based on the ignition timing under low load conditions. It

Then, the difference between the actual compression ratio ε ₁ under the high load condition and the actual compression ratio ε ₂ under the low load condition (Δε = ε ₂ −
ε ₁ ) is obtained, and the smaller the difference Δε is, the larger the initial correction amount during the transition is given to the correction amount setting means 5. The correction means 7 corrects the retard angle side during acceleration and the advance angle side during deceleration based on the initial correction amount. In the transient state, the basic ignition timing changes immediately in consideration of the change in the compression ratio according to the change in the operating conditions, but the actual change in the compression ratio is delayed, but it is necessary to provide the initial correction amount in this way. Properly offsets the effects of the delay.

This will be described with reference to FIGS. 11 and 12.
First, when the actual compression ratio under a high load condition is higher than a predetermined value as indicated by symbol ε _{B in} FIG. 11, the required ignition timing is slightly later than the basic ignition timing as indicated by symbol B. Located on the corner side. Conversely, the actual compression ratio is the sign ε
When it is lower than the predetermined value as shown by _B ', the required ignition timing is on the advance side as shown by B'. Therefore, considering the acceleration at the time of shifting from the low load region to the high load region, in the former case where the required ignition timing after acceleration is B (that is, when the compression ratio difference Δε is small), the delay of the compression ratio change is delayed. In the latter case where the required ignition timing after acceleration is B '(that is, when the compression ratio difference Δε is large), it is necessary to give a large amount of initial correction to the retard side for canceling. The initial correction amount is small.

The above is a request when the compression ratio at a low load before acceleration is at a predetermined value. For example, the actual compression ratio under a low load condition is higher than the predetermined value as indicated by reference sign ε _A in FIG. For example, the actual ignition timing before acceleration is controlled to be slightly retarded from the basic ignition timing by the knocking control and the MBT control, as indicated by symbol A in FIGS. Therefore, even if the actual compression ratio under a high load condition is high and the required ignition timing is in the state of B, the initial correction amount may be given to the same extent as when the compression ratio shows a normal compression ratio change. . Further, when the actual compression ratio under the low load condition is high, the ignition timing before acceleration is at the position A, and the required ignition timing after acceleration is at the position B ', the correction amount is further reduced. Must be done. On the contrary, the compression ratio under the low load condition before acceleration is lower than the predetermined value as indicated by the symbol ε _A ′ in FIG. 11, and the ignition timing is controlled to the position A ′ by the knocking control and the MBT control. In this case, it is necessary to give a large initial correction amount during acceleration.

In short, if the difference Δε between the actual compression ratio under the low load condition before acceleration and the actual compression ratio after the acceleration under high load condition is smaller, the larger the initial correction amount is, It is possible to perform ignition timing correction more suitable for the above requirements.

The same applies to deceleration, and the compression ratio difference Δ
The smaller ε is, the larger the initial correction amount needs to be given.

Second Embodiment FIG. 2 is a configuration explanatory view showing an embodiment of an ignition timing control device for a variable compression ratio internal combustion engine according to the present invention.

In the figure, reference numeral 11 indicates an in-line four-cylinder variable compression ratio type internal combustion engine as an example, and the internal combustion engine 11 is provided with a compression ratio variable mechanism, which will be described later, in the piston portion of each cylinder, for example.

Further, a combustion pressure sensor 13 is provided for each cylinder in the internal combustion engine 11 in order to individually detect occurrence of knocking in the # 1 to # 4 cylinders. The combustion pressure sensor 13 is formed in a washer shape using, for example, a piezoelectric element, and is attached to the ignition plug 12 mounting portion of each cylinder. The output signal of the combustion pressure sensor 13 is input to the control unit 18 as a combustion pressure signal, and is used in the control unit 18 for detecting the combustion pressure peak position during MBT control, and the knocking vibration component from this position. Is used for knocking detection.

Further, in the intake passage 14 of the internal combustion engine 11, an air flow meter 15 for detecting the engine intake air amount is arranged. The intake air amount signal output from the air flow meter 15 is input to the control unit 18.

Reference numeral 16 denotes a crank angle sensor that detects the rotation of the crankshaft of the internal combustion engine 11.
16 is a pulse signal for every 1 ° of crank angle indicating the rotation angle,
A pulse signal for every 180 ° of crank angle for detecting a predetermined position before compression top dead center of each cylinder is output to the control unit 18.

The control unit 18 uses a digital microcomputer system and performs various arithmetic processes.
CPU, ROM that stores control programs and fixed data,
It mainly consists of RAM and I / O ports for temporary storage of various data. The control unit 18 includes an air flow meter 15, a crank angle sensor 16,
Furthermore, ignition timing control by MBT control and knocking control is individually performed for each cylinder based on detection signals from sensors such as the combustion pressure sensor 13. The ignition device 17 including an ignition coil, a power transistor, and the like operates according to the ignition timing determined by the control unit 18, and sequentially ignites each cylinder.

FIG. 3 shows an example of the structure of the compression ratio variable mechanism built in the piston portion of the internal combustion engine 11. In FIG. 3, 21 is a connecting rod, 22 is an inner piston connected to the small end of the connecting rod 21 via a piston pin 23, and 24 is slidably fitted and arranged on the outer side of the inner piston 22. The outer cup-shaped outer pistons are shown. The back surface of the crown of the outer piston 24 and the upper surface of the inner piston 22 are formed into smooth surfaces that can be in close contact with each other, and an upper liquid chamber 25 is formed between them. Further, an annular member 26 serving as a stopper is screwed to the inner periphery of the lower end portion of the outer piston 24, and between the upper surface of the annular member 26 and the lower surface of the outer peripheral portion of the inner piston 22 facing the annular member 26, A lower liquid chamber 27 is formed. Since FIG. 3 shows a high ε state, that is, a state where the outer piston 24 has moved to the upper limit position, the lower liquid chamber 27 is in a crushed state.

The piston pin 23 is held by the inner piston 22 via a pair of snap rings 28, and has a substantially cylindrical shape, and a cylinder portion 29 is formed to penetrate through the inner periphery thereof. The cylinder portion 29 has one end portion formed in a large diameter portion 29a and the other end portion formed in a small diameter portion 29b, and a spool valve 30 is slidably accommodated therein. This spool valve 30 has a first valve body portion 31 fitted to the inner circumference of the large diameter portion 29a at one end, and a second valve fitted to the inner circumference of the small diameter portion 29b of the cylinder portion 29 at the other end. It has a body portion 32. A hydraulic fluid chamber 33 is defined in the cylinder portion 29 by the first valve body portion 31 and the second valve body portion 32. Further, the spool valve 30 is constantly urged toward the second valve body portion 32 side by the coil spring 34 disposed on the first valve body portion 31 side. Incidentally, 35 is a stopper having an opening 35a at the center, and 36 is a spring seat.

The hydraulic fluid chamber 33 communicates with a main passage 37 formed in the connecting rod 21 via a check valve 38, and the check valve 38 allows only the inflow of oil into the hydraulic fluid chamber 33. ing. The main passage 37 communicates with an oil pump of the engine lubrication system so that a part of the engine lubrication oil is pumped without special hydraulic control.

An upper supply passage 39 is formed between the working liquid chamber 33 and the upper liquid chamber 25. This upper supply passage 39 is
It has a check valve 40 that allows only oil to flow into the upper liquid chamber 25 side. Further, the upper supply passage 39 has the cylinder portion 29
Is open at the small diameter portion 29b of the valve and is closed only when the spool valve 30 slides to the left in the drawing. Further, 41 is a signal pressure passage provided between the upper liquid chamber 25 and the working liquid chamber 23, and the signal pressure passage 41 always communicates the two regardless of the position of the spool valve 30 and is caused by the combustion pressure. Upper liquid chamber 25
The pressure fluctuation of is transmitted to the hydraulic fluid chamber 33.

Further, a lower supply passage 42 is provided between the working liquid chamber 33 and the lower liquid chamber 27. This lower supply passage 42 is
A check valve 43 that communicates with the hydraulic fluid chamber 33 regardless of the position of the spool valve 30 and that allows only the flow to the lower fluid chamber 27 side is provided in the passage.

In addition to the upper supply passage 39, an upper discharge passage 44 is formed in the small diameter portion 29b of the cylinder portion 29.
One end of the upper discharge passage 44 communicates with the upper liquid chamber 25, and the other end of the upper discharge passage 44 is closed when the spool valve 30 is in contact with the inner peripheral surface of the small diameter portion 29b, specifically, the spool valve 30. Is formed at a position where it can be opened when it slides to the left in the figure.

The variable compression ratio mechanism having the above configuration automatically switches the compression ratio according to the combustion pressure in the combustion chamber, that is, the engine load, and is in the high compression ratio state when the combustion pressure is low and the load is low. That is, the hydraulic fluid chamber 33 passes through the main passage 37.
The lubricating oil pumped inside flows into the upper liquid chamber 25 through the upper supply passage 39. At this time, since the upper discharge passage 44 is closed by the spool valve 30, the hydraulic pressure generated in the upper liquid chamber 25 pushes the outer piston 24 upward with respect to the inner piston 22, and the high ε state is established. At this time, the lower liquid chamber 27 also communicates with the working liquid chamber 33 through the lower supply passage 42, but the pressure receiving area of the outer piston 24 in the lower liquid chamber 27 is the pressure receiving area of the outer piston 24 in the upper liquid chamber 25. Since it is much smaller than the outer piston 24, it moves upward as described above,
Is crushed.

On the other hand, when the internal combustion engine is in a high load state, the combustion pressure inevitably rises and the outer piston 24
The large combustion pressure acts on the upper surface. As a result, the hydraulic pressure in the upper liquid chamber 25 becomes extremely high, and the pressure is transmitted to the hydraulic fluid chamber 33 through the signal pressure passage 41. In other words, the hydraulic pressure in the hydraulic fluid chamber 33 rises with the combustion pressure, and as a result, the spare valve 30 has the first and second valve body portions.
Due to the difference in pressure receiving area between 31, 32, the coil spring 34 quickly slides to the left in the figure against the urging force. Therefore, the upper discharge passage 44 is opened, and the lubricating oil in the upper liquid chamber 25 is discharged to the outside. Therefore, the outer piston 24 receives the combustion pressure and moves downward to be in the low ε state. At this time, the lubricating oil is supplied to the lower liquid chamber 27 from the hydraulic liquid chamber 33, and the outer piston 12 is urged downward with respect to the inner piston 22.
Therefore, relative movement of the outer piston 24 is prevented by inertial force or the like.

Thus, the compression ratio variable mechanism is switched between the low ε state and the high ε state by the combustion pressure. As a result, when the load (for example, the basic fuel injection amount Tp) and the engine speed are used as parameters, the low ε region and the high ε region are divided with the characteristics shown in FIG.

Next, the ignition timing control executed in the control unit 18 will be described with reference to the flowcharts shown in FIGS.

FIG. 5 is a main flowchart of the ignition timing control executed by the control unit 18. The control program shown in FIG. 5 is executed for each cylinder, that is, the ignition timing is retarded for each cylinder.

The ignition timing control in the constant time is mainly processed in the steps 1 to 11. First, in step 1, the basic ignition timing ADVO corresponding to the engine operating conditions at that time is set. This basic ignition timing ADVO is successively looked up from a basic ignition timing map with the load of the internal combustion engine (for example, basic fuel injection amount Tp) and the number of revolutions as parameters. The characteristic of the basic ignition timing is set on the premise that the compression ratio is controlled to be switched to low ε and high ε under a predetermined operating condition in advance, and as shown in FIG. The required ignition timing characteristic for ε and the required ignition timing characteristic for high ε are connected at the compression ratio switching point. In addition, a basic ignition timing map along the characteristics for low ε and a basic ignition timing map along the characteristics for high ε are set in advance, and either one is selected according to the engine operating conditions to select the basic ignition timing. May be configured to be looked up.

Next, in step 2, it is determined whether or not the cylinder is knocked, based on the knocking vibration component extracted from the combustion pressure signal of the cylinder. If it is determined that there is no knocking, the process proceeds to step 3 to calculate the feedback correction amount FB by MBT control. Since this MBT control itself is known from JP-A-62-96779, etc.,
Although its detailed description is omitted, basically, the peak position of the combustion pressure is detected based on the combustion pressure detected by the combustion pressure sensor 13, and the peak position is determined by a predetermined ATDC.
The ignition timing is feedback-controlled so that the ignition timing is around 15 °. Normally, the feedback correction amount FB is increased / decreased by a constant amount to perform the retard angle and advance angle corrections. If it is determined in step 2 that knocking has occurred, the process proceeds to step 4 to calculate the feedback correction amount FB by knocking control. Although this knocking control itself is also known, a detailed description thereof will be omitted. For example, each time knocking is detected, the feedback correction amount FB is increased by a fixed amount to the retard side to retard the ignition timing.

Then, in step 10, the ignition timing ADV of the cylinder is set to AVO +
It is determined as FB, and the ignition timing ADV is output in step 11.

In step 5 and step 6, whether the basic combustion injection amount is the acceleration state or the deceleration state is determined.
The determination is made based on the value of the change rate ΔTp of Tp. In step 7, an acceleration determination flag FA and a deceleration determination flag FD, which will be described later, are reset.

As a result of repeatedly executing the MBT control and the knocking control as described above, the ignition timing in the steady state is maintained at the MBT point or the knocking occurrence limit for each cylinder. That is,
In the operating region where the MBT point is on the advance side of the knocking occurrence limit, the ignition timing is at the knocking occurrence limit, and conversely MBT
The ignition timing is kept at the MBT point in the operating region where the point is on the retard side of the knocking occurrence limit.

Next, the determination of the initial correction amount made in steps 12 to 21 will be described. First, step 8 and step 9
Then, it is determined based on the basic fuel injection amount Tp whether or not each is in a predetermined high load region and whether or not it is in a predetermined low load region. The reference value Tp ₁ of step 8 is set to the high load side as shown in FIG. 4, whereby the compression ratio ε ₁ is detected in the region where the compression ratio variable mechanism is always in the low ε state. I am trying. Similarly, the reference value Tp of step 9
_As shown in FIG. 4, ₂ is set on the low load side, so that the compression ratio variable mechanism always detects the actual compression ratio ε ₂ within the region in which the compression ratio is high.

When it is determined in step 8 that the engine is in the predetermined high load region, the process proceeds to steps 12 and 13, and the first reference ignition timing ADV ₁ and the second reference ignition timing corresponding to the operating conditions at that time.
Look up ADV ₂ . First reference ignition timing ADV
₁ is the first reference compression ratio, for example, the ignition timing is experimentally determined on the premise of the compression ratio ε ₀₁ when the outer piston 24 is at the lower limit position (low ε state) with respect to the inner piston 22, and the engine load (Basic fuel injection amount Tp) and engine speed are given in the form of a data map corresponding to each operating condition. The first reference ignition timing ADV ₁
Usually corresponds to the required ignition timing characteristic for low ε shown in FIG. 11. The second reference ignition timing ADV ₂ is
The second reference compression ratio, for example, the compression ratio ε when the outer piston 24 is at the upper limit position with respect to the inner piston 22 (high ε state).
_The ignition timing was experimentally obtained on the premise of ₀₂ ,
Again, it is given corresponding to each operating condition in the form of a data map using the load Tp and the number of revolutions as parameters. The second reference ignition timing ADV ₂ normally matches the required ignition timing characteristic for high ε shown in FIG. 11.

Next, in step 14, the actual ignition timing ADV at that time is
(For details, the value obtained last time) and the first and second reference ignition timings ADV ₁ and ADV ₂ from the actual compression ratio ε under high load conditions.
Calculate ₁ This utilizes the fact that the compression ratio and the ignition timing are in a substantially proportional relationship, and specifically, the compression ratio ε ₁ is obtained by the following equation.

That is, the actual compression ratio ε ₁ on the low ε side of the cylinder is obtained from the relationship shown in FIG. 7. In addition,
If the variable compression ratio mechanism operates normally, the compression ratio ε ₁ is naturally obtained as a value close to the reference lower limit compression ratio ε ₀₁ .

The compression ratio ε ₁ detected in this way is stored in the memory and is updated successively.

On the other hand, when it is determined in step 9 that the vehicle is in the predetermined low load area, the process proceeds to steps 17 to 19 and
The actual compression ratio ε ₂ under the low load condition is detected by the same processing as 12 to 14 (see FIG. 7). The detected compression ratio ε ₂ is also stored in the memory. If the variable compression ratio mechanism operates normally, the compression ratio ε ₂ can be obtained as a value close to the reference upper limit compression ratio ε ₀₂ .

Then, in step 15 when the load is high and in step 20 when the load is low, the difference Δε between the actual compression ratio ε ₂ under the low load condition and the actual compression ratio ε ₁ under the high load condition is obtained. In addition, step 16 or step 21
At, the initial correction amount A ₁ during acceleration or the initial correction amount A ₂ during deceleration is determined. The acceleration initial correction amount A ₁ and the deceleration initial correction amount A ₂ are given in the form of a data map using the compression ratio difference Δε and the engine speed as parameters, and are successively looked up. FIG. 8 shows the relationship between the compression ratio difference Δε and the initial correction amounts A ₁ and A ₂ at a certain rotation speed. The smaller the compression ratio difference Δε, the more the initial correction amounts A ₁ and A 2.
₂ is given greatly. Further, in the variable compression ratio mechanism having the above-described configuration that depends on the combustion pressure, the compression ratio change during deceleration is slower than during acceleration, so the initial correction amount during deceleration A ₂ is the initial correction amount during acceleration. It is set larger than A ₁ .

The acceleration initial correction amount A ₁ and the deceleration initial correction amount A ₂ thus obtained are stored in the memory as learning values corresponding to the respective rotation speeds and are updated successively.

Next, the ignition timing correction during transition will be described. First, at the time of acceleration, the routine proceeds from step 5 to step 22, where the acceleration determination flag FA is set to 1, and at step 23 it is determined whether or not the acceleration timer TM1 has reached a predetermined value T ₁ . The acceleration timer TM1 is incremented by the timer routine shown in FIG. 6 only when the acceleration determination flag FA is 1 (steps 33, 3).
5), that is, the elapsed time from the start of acceleration. Then, while the value of TM1 indicating this elapsed time is T ₁ or less, that is, in the initial stage of acceleration, the process proceeds from step 23 to step 24, and the feedback correction amount FB is set to FB = −A ₁ , and the initial correction amount during acceleration A is set. Ignition timing correction by ₁ . This correction is performed only during T _{1 in} the initial stage of acceleration as described above (steps 23 to 25). Therefore, as shown in FIG. 9, the actual ignition timing at the time of acceleration is once largely corrected to the retard angle side at the initial stage of acceleration, and the knocking of the strength caused by the response delay of the compression ratio variable mechanism occurs. Can be reliably prevented. Moreover, the correction amount A ₁ corresponds to the actual change in the compression ratio of each cylinder, so that the optimum correction without excess or deficiency is performed.

Similarly, at the time of deceleration, the routine proceeds from step 6 to step 26, where the deceleration determination flag FD is set to 1, and at step 27 it is determined whether or not the deceleration timer TM2 has reached the predetermined value T ₂ . The above acceleration timer TM2 is the sixth
With the timer routine shown in the figure, deceleration determination flag FD
Is incremented only when is 1 (steps 34, 36), that is, it indicates the elapsed time from the start of deceleration. Then, while the value of TM2 indicating this elapsed time is T ₂ or less, that is, in the initial stage of deceleration, from step 27 to step
Proceed to 28, set the feedback correction amount FB to FB = A ₂ ,
The ignition timing is corrected by the initial correction amount A ₂ during deceleration. This correction is performed only during T _{2 at} the initial stage of deceleration as described above (steps 27, 28, 25). Therefore, the actual ignition timing at the time of deceleration is once largely corrected to the advance side at the initial stage of deceleration, as shown in FIG. 10, and the output decrease and the driving due to the response delay of the compression ratio variable mechanism are reduced. It is possible to reliably prevent the deterioration of sex. Moreover, the correction amount A ₂ also corresponds to the actual change in the compression ratio of each cylinder, and the optimum correction without excess or deficiency is performed.

In short, each internal combustion engine has a different compression ratio,
Even if the compression ratio is different for each cylinder, it is corrected according to the initial correction amount learned based on the actual compression ratio, so it is not affected by variations in the compression ratio, It becomes possible to control the ignition timing in accordance with the requirement in 1.

In the above embodiment, the initial correction is added for both acceleration and deceleration. However, for example, in the case where the initial correction is performed only during acceleration, which is especially problematic in terms of knocking occurrence, The invention is applicable. Further, in the above embodiment, the compression ratio variable mechanism has been described as a type in which the compression ratio switching control is automatically performed by the combustion pressure, but the present invention is disclosed in, for example, Japanese Utility Model Laid-Open No. 58-25637. As described above, the invention can be similarly applied to the case where the compression ratio switching is externally controlled.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the ignition timing control device for a variable compression ratio internal combustion engine according to the present invention, it is possible to cope with a response delay of the compression ratio variable mechanism during acceleration and deceleration of the engine. Therefore, the ignition timing is temporarily retarded and advanced, so that it is possible to prevent the ignition timing from being temporarily advanced or delayed too much, and to prevent knocking, output reduction, or the like during a transition. Since the initial correction amount is determined in consideration of the actual compression ratio of the engine, even if the compression ratio is slightly different due to the assembly error or the thickness of the cylinder head gasket,
Optimal correction can be performed without excess or deficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing the structure of the present invention corresponding to a claim, FIG. 2 is an explanatory view showing the structure of an embodiment of the present invention, FIG. 3 is a sectional view showing an embodiment of a compression ratio variable mechanism, and FIG. Is an operation characteristic diagram of this compression ratio variable mechanism, FIGS. 5 and 6 are flowcharts showing a control program in the above-mentioned embodiment, FIG. 7 is a characteristic diagram showing a relationship between compression ratio and ignition timing, and FIG. FIG. 9 is a characteristic diagram showing the relationship between the compression ratio difference Δε and the initial correction amount, FIG. 9 is a characteristic diagram showing the ignition timing change during acceleration, FIG. 10 is a characteristic diagram showing the ignition timing change during deceleration, and FIG. FIG. 12 is a characteristic diagram showing a basic ignition timing characteristic with respect to a load, and FIG. 12 is a characteristic diagram showing a conventional ignition timing change during acceleration together with a compression ratio change. 1 ... knocking detection means, 2 ... MBT control means, 3 ...
... knocking control means, 4 ... compression ratio detection means, 5 ...
Correction amount setting means, 6 ... Transient detection means, 7 ... Correction means, 8 ... Basic ignition timing setting means.

Claims (1)

(57) [Claims] 1. A variable compression internal combustion engine in which a compression ratio is variably controlled according to engine operating conditions, a basic ignition timing setting means for setting a basic ignition timing according to engine operating conditions, and whether or not the engine is knocked. Knocking detection means for detecting, MBT control means selected when there is no knocking and controlling the ignition timing to the MBT point by correcting the basic ignition timing, and when there is knocking and selected for the basic ignition timing Knocking control means for controlling the ignition timing to the knocking occurrence limit with correction, and compression for estimating the actual compression ratio under high load conditions and the actual compression ratio under low load conditions from the ignition timing during engine steady state A ratio detection means, a correction amount setting means for setting an initial correction amount during a transition based on the difference between the two compression ratios, a transient detection means for detecting an engine transient state, and a transient detection time during the transient detection. Serial initial correction amount ignition timing control device for a variable compression ratio internal combustion engine comprising a correcting means for correcting the ignition timing based on.