JPH01163468A - Control device for ignition timing of variable compression ratio type internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent knocking and the lowering of output by temporarily correcting ignition timing to the delay side and the advance side at the time of switching over from a high compression ratio to a low compression ratio and the other way around respectively. CONSTITUTION:A variable compression ratio type engine is controlled to be a high compression ratio (high epsilon) condition in a low load zone while being controlled to be a low compression ratio (low epsilon) condition in a high load zone, and the ignition timing is set on the delay side in the high epsilon condition while on the advance side in the low epsilon condition. At the time of switching over a compression ratio variable mechanism from a high epsilon to a low epsilon, a fundamental ignition timing is suddenly advanced. A first timer means 2 is operated by a compression ratio judging means 1 and, since the ignition timing is temporarily corrected to the delay side in accordance with the lapse of the time by a first correcting means 4, the deviation from a required ignition timing accompanying the delay in response of the compression ratio variable mechanism can be avoided. On the contrary, at the time of switching over from the low epsilonto the high epsilon, the ignition timing is temporarily corrected to the advance side. Hence, knocking caused by the overly advanced ignition timing or the lowering of output caused by the overly delayed ignition timing can be surely prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ignition timing control device for a variable compression ratio internal combustion engine that switches between a high compression ratio and a low compression ratio depending on engine operating conditions.

BACKGROUND OF THE INVENTION Various variable compression ratio internal combustion engines have been proposed in the past in order to improve thermal efficiency at low loads and suppress knocking at high loads. For example, in Japanese Utility Model Application No. 58-25637, the piston of each cylinder has a double structure of an inch piston and an outer piston,
The variable compression ratio mechanism changes the compression ratio by moving the outer piston up and down relative to the inch piston.
Furthermore, Japanese Patent Application Laid-Open No. 60-230548 describes a variable compression ratio mechanism in which a sub-cylinder is formed in the cylinder head and the compression ratio is changed by vertically moving a sub-piston within the sub-cylinder. ing.

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

On the other hand, the ignition timing of an internal combustion engine is controlled based on a data map with engine speed and load as parameters, but in a variable compression ratio internal combustion engine, the data in the data map, that is, the optimal ignition timing, is naturally controlled. However, it is predetermined in accordance with the required ignition timing based on the compression ratio at that time. In other words, in a low ε state, it is possible to advance the ignition timing to a certain extent than in a high ε state, so it is possible to advance the ignition timing to a certain extent than in a high ε state. ), the ignition timing is set to an advance side characteristic as a whole, and in a high ε region (a region controlled to a high ε, that is, a generally low load state), the ignition timing is set to a retard side characteristic as a whole. Then, near the switching point of the compression ratio, the ignition timing has a discontinuous characteristic.

Problems to be Solved by the Invention Therefore, for example, engine load (e.g. basic fuel injection amount Tp
etc.) gradually increases as shown in Figure 6, then
At a certain point, the compression ratio variable mechanism switches from high ε to low ε, and at the same time, the basic ignition timing rapidly advances from the high ε characteristic to the low ε characteristic, as shown by the solid line (A). It turns out.

However, by the time the compression ratio variable mechanism operated by hydraulic pressure etc. completely shifts from the high ε state to the low ε state,
Generally, there is some delay time. Therefore, during this period, the ignition timing is too advanced relative to the actual compression ratio, which may result in knocking.

Conversely, when switching from a low ε state to a high ε state,
Due to the delay in the response of the variable compression ratio mechanism, the ignition timing is temporarily delayed too much, resulting in a reduction in the horn output.

Means for Solving the Problems This invention was made in view of the conventional problems as described above, and as shown in FIG. In a variable compression ratio internal combustion engine equipped with a variable compression ratio mechanism that switches between a low compression ratio (low ε), it is possible to determine whether the variable compression ratio mechanism is in a high compression ratio state or a low compression ratio state. A compression ratio determination means 1 for determining a compression ratio, and a first compression ratio determination means 1 that is activated when switching from a high compression ratio to a low compression ratio.
a timer means 2; a second timer means 3 activated when switching from a low compression ratio to a high compression ratio; and the first timer means 2.
a first correction means 4 for correcting the ignition timing to the retard side according to the elapsed time of the second timer means 3; and a second correction means 5 for correcting the ignition timing to the advance side according to the elapsed time of the second timer means 3. It is characterized by the fact that it is equipped with

When the variable compression ratio mechanism is switched from high ε to low ε,
The basic ignition timing is rapidly advanced as described above. However, since the ignition timing is temporarily corrected to the retarded side in accordance with the elapsed time of the first timer means 2, a deviation from the required ignition timing due to a response delay of the variable compression ratio mechanism is avoided.

Conversely, when switching from low ε to high ε, the basic ignition timing is rapidly retarded, but the ignition timing is temporarily corrected to the advanced side according to the elapsed time of the second timer means 3. Because
After all, deviation from the required ignition timing due to response delay of the variable compression ratio mechanism can be avoided.

Embodiment FIG. 2 is a configuration explanatory diagram 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 denotes an internal combustion engine that includes a fuel injection valve 12 and a spark plug I3, and this internal combustion engine 11 includes, for example, a variable compression ratio mechanism, which will be described later, in a piston 14 portion.

15 is an air flow meter that detects the intake air amount of the internal combustion engine 11, 16 is a distributor with a built-in crank angle sensor 17, 18 is an ignition coil, and 19 is a transistor eveninger that cuts off the primary current of this ignition coil 18. ing.

Reference numeral 20 denotes a control unit consisting of a microcomputer that controls the ignition timing of the spark plug 13 and the fuel injection amount of the fuel injection valve 12. An air amount signal, a rotation speed signal, etc. are input. The control unit 20 performs arithmetic processing according to a predetermined program and outputs predetermined control signals to the fuel injection valve 12 and the transistor eveninger 19.

FIG. 3 shows an example of the configuration of a variable compression ratio mechanism built into the piston 14 portion. In Figure 3, 21
22 is a connecting rod, 22 is an inch piston connected to the small end of the connecting rod 21 via a piston pin 23, and 24 is a cup-shaped outer piston that is slidably fitted on the outside of this inch piston 22. are shown respectively. The back surface of the crown of the outer piston 24 and the top surface of the inch piston 22 are formed into smooth surfaces that can come into substantially 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 onto the inner periphery of the lower end of the outer piston 24, and between the upper surface of this annular member 26 and the lower surface of the outer periphery of the inch piston 22 facing thereto, A lower liquid chamber 27 is formed. Note that since FIG. 3 shows a high ε state, that is, a state in which 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 inch piston 22 via a pair of snap rings 28, and has a substantially cylindrical shape, and has a cylinder portion 29 formed through its inner periphery.

The cylinder portion 29 has a large diameter portion 29a at one end and a small diameter portion 29b at the other end, and a spool valve 30 is slidably housed inside the cylinder portion 29.

This spool valve 30 has a first valve body part 3I fitted to the inner periphery of the large diameter part 29a at one end, and a second valve part 3I fitted to the inner periphery of the small diameter part 29b of the cylinder part 29 at the other end. It has a body part 32. The hydraulic fluid chamber 3 is inserted into the cylinder portion 29 by the first valve body portion 31 and the second valve body portion 32.
3 are separated. Further, the spool valve 30 is always urged toward the second valve body 32 by a coil spring 34 disposed on the first valve body 3I side.

Note that 35 is a stopper having an opening 35a in the center;
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,
The check valve 38 allows only the inflow of water into the hydraulic fluid chamber 33. The main passage 37 communicates with an oil pump for the engine lubrication system, and a portion of the engine lubrication oil is pumped therein without special hydraulic control.

Further, an upper supply passage 39 is formed between the working fluid chamber 33 and the upper fluid chamber 25. This upper supply passage 3
9 has a check valve 40 that only allows oil to flow into the upper liquid chamber 25 side. Further, the upper supply passage 39 is
The spool valve 3 opens into the small diameter portion 29b of the cylinder portion 29.
It is in a position where it is closed only when it is slid to the left in the figure. Furthermore, 41 is a signal pressure passage provided between the upper liquid chamber 25 and the working liquid chamber 33;
1 always communicates between the two regardless of the position of the spool valve 30, and transmits pressure fluctuations in the upper liquid chamber 25 caused by combustion pressure to the working liquid chamber 33.

Further, a lower supply passage 42 is provided between the working fluid chamber 33 and the lower fluid chamber 27. This lower supply passage 4
2 is in communication with the working fluid chamber 33 regardless of the position of the spool valve 30, and a check valve 43 is provided in the passageway to allow flow only to the lower fluid chamber 27 side.

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. This upper discharge passage 44 has a negative end communicating with the upper liquid chamber 25, and the other end being closed when the spool valve 30 is in contact with the inner circumferential surface of the small diameter portion 29b, and more specifically, when the spool valve 30 is in contact with the stopper 35. An opening is formed at a position that can be opened when 30 is slid to the left in the figure.

The variable compression ratio mechanism configured as described above automatically switches the compression ratio according to the combustion pressure in the combustion chamber, that is, the engine load, and enters a high compression ratio state during low load when the combustion pressure angle is low. That is, the lubricating oil forced into the hydraulic fluid chamber 33 through the main passage 37 flows into the upper fluid 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 oil pressure generated in the upper liquid chamber 25 causes the outer piston to
4 is pushed upward relative to the inch piston 22, resulting in a high ε state. 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 equal to the pressure receiving area of the outer piston 24 in the upper liquid chamber 25. , the outer piston 24 moves upward as described above, and the lower liquid chamber 27 becomes crushed.

On the other hand, when the internal combustion engine is in a high load state, the combustion pressure inevitably increases, and at the beginning of the expansion stroke, the outer piston 24
The large combustion pressure acts on the upper surface. As a result, the oil pressure in the upper liquid chamber 25 becomes extremely high, and this pressure is transmitted into the working liquid chamber 33 through the signal pressure passage 41.

In other words, the oil pressure in the hydraulic fluid chamber 33 rises with the combustion pressure, and as a result, the spool valve 30 is forced to act on the coil spring 34 due to the pressure receiving area difference between the first and second valve body parts 31 and 32. It quickly slides to the left in the figure against the force. Therefore, the upper discharge passage 44 is opened and the upper liquid chamber 2
The lubricating oil inside 5 is discharged to the outside. Therefore, the outer piston 24 moves downward in response to the combustion pressure, and enters a low ε state. At this time, lubricating oil is supplied to the lower liquid chamber 27 from the working liquid chamber 33 to urge the outer pilston 24 downward with respect to the inch piston 22. Therefore, relative movement of the outer piston 24 due to inertial force or the like is prevented.

In this way, the variable compression ratio mechanism is switched between the low ε state and the high ε state depending on the combustion pressure.

As a result, when the load (for example, basic fuel injection ff1Tp) and engine speed are used as parameters, the low ε region and the high ε region are separated by the characteristics shown in FIG.

Next, ignition timing control in the above embodiment will be explained.

The ignition timing during steady operation is basically determined based on the basic ignition timing that is sequentially looked up from a data map provided in the control unit 20. The basic ignition timing data map is set using the engine speed and load (basic fuel injection amount Tp) as parameters, and is set in particular to meet the required ignition timing in consideration of variable compression ratio control. In other words, the basic ignition timing in the low ε region is set relatively on the advanced side assuming a low ε state, and the basic ignition timing in the high ε region is
It is set on the relatively delayed side on the premise that it is in a high ε state.

Therefore, in a steady operating state, the optimum ignition timing can be ensured regardless of low ε or high ε.

On the other hand, when the compression ratio variable mechanism switches, as mentioned above, due to the response delay of the actual compression ratio switching,
A deviation occurs between the required ignition timing and the basic ignition timing in steady state. Therefore, in order to prevent this, the ignition timing is corrected according to the flowchart shown in FIG.

The processing procedure for this ignition timing correction will be explained below.

The correction amount calculation routine shown in FIG. 4 is repeatedly executed in synchronization with the engine rotation, which seems to be time-synchronized.

First, in step 1, the engine speed N and the load, that is, the basic fuel injection ITp are read. Then, in step 2, based on the rotational speed N, find the threshold value TpO that is the boundary between the low ε region and the high ε region at that time. This is because the switching characteristics of the variable compression ratio mechanism shown in FIG. 5 are provided in the control unit 20 as a data map, and the rotation speed N
This is done by sequentially reading out the boundary values corresponding to 4-.

Next, in step 3, the load Tp at that time is set to the threshold value Tp
It is compared with O to determine whether it is a low ε region or a high ε region. In other words, the load Tp is 'r p .

If it is above, the engine operating condition is in the low ε region, and TpO
If it is below, it is in the high ε region.

That is, steps 1 to 3 determine the state (high ε state or low ε state) that the compression ratio variable mechanism should take based on the load and rotation speed.
state) is determined, and constitutes a compression ratio determining means.

This routine also determines whether it was in the low ε region last time or the high ε region.
Whether it is within the area is determined based on the flag HL (step 4.13). If this flag HL is "0",
This means that it was in the low ε region last time, and if it is NJ, it means that it was in the high ε region last time.

As an example, to explain the flow when moving from a high ε region to a low ε region, the process proceeds from step 3 to step 4, and since it was in the high ε region last time, the process proceeds to step 5.6. In step 5, timer TM2 is cleared, and in step 6, timer TM1 is activated. In other words, the timer TMI indicates the elapsed time since the transition to the low ε region. In step 7, the value of the timer TMI is compared with a predetermined value t. If it is less than or equal to t, the process proceeds to step 8, and the ignition timing correction amount ADVH is set to a predetermined value -
Set to R. Then, in step 12, flag HL is set to "
0'' and the -th routine ends.

Next time, since the flag I-I L is "0" in step 4, the process advances from step 4 to step 7. Then, until the value of timer TMI reaches the predetermined value tl, the correction ffl
ADVH is held at -R (step 8).

The above routine is repeated and when the value of the timer TM1 reaches the predetermined value L1 (step 7), the process proceeds from step 7 to step 9, and the correction amount ADV I-1
gradually approaches "0". And correction i A D
When V I-I reaches "0" (step IO), the correction ff1ADVH is fixed at "0" (step 1).
1).

The actual ignition timing of the internal combustion engine 11 is the basic ignition timing obtained from the data map, plus the correction ff obtained as described above.
1 ADVH is added. That is, when transitioning from the high ε region to the low ε region, the ignition timing is temporarily corrected to the retarded side.

FIG. 6 shows how the ignition timing changes when the load of the internal combustion engine 11 is gradually increased. When the load Tp reaches the threshold value TpO, the compression ratio variable mechanism At the same time, the basic ignition timing changes to the advanced side as a whole, as shown by the solid line (A). However, at the same time, since the correction amount ADVI4 is given to the retard side as shown in the figure, the ignition timing actually obtained has a characteristic as shown by the broken line (b). As a result, it is possible to reliably prevent knocking caused by a delay in response of the variable compression ratio mechanism to low ε.

Next, calculation of the correction amount when the operating condition shifts from the low ε region to the high ε region will be explained. That is, in this case, the process proceeds from step 3 to step 13, where the flag HL is determined. In this case, since the previous time was in the low ε region and the flag HL is "0", step 14.
15, the timer TMI is cleared and the timer TM2 is activated. Then, in step 16, the value of the timer TM2 is compared with a predetermined value.

Then, until the value of the timer TM2 reaches t, the correction IADVH is set to a constant value R (step 17).
. Further, when the value of the timer TM2 reaches a predetermined value, the process proceeds from step 16 to step I8, and the correction amount ADV
Gradually reduce H.

Finally, when the correction ffi A DV H becomes "0" (step I9), this correction amount A DV H is changed to "
0'' (step 20). Note that, as mentioned above, when moving to the -dan high ε region, the flag l-ll7 is set.
or Nj (step 21).

Therefore, when transitioning from the low ε region to the high ε region, the ignition timing is temporarily corrected to the advanced side.

FIG. 7 shows changes in the ignition timing, etc. when the load Tp of the internal combustion engine 11 is gradually reduced. In this case as well, when the load Tp reaches the threshold value TpO, the mechanical switching operation of the variable compression ratio mechanism to the high ε side is started, and at the same time the basic ignition timing changes to the characteristics for high ε. Change.

In other words, the characteristics as a whole are on the delayed side (solid line (c)). However, since the correction m A DV H is given to the advance side, the actual ignition timing has a characteristic as shown by the broken line (D). Therefore, the actual ignition timing is not delayed too much in response to the response delay of the variable compression ratio mechanism, and a decrease in output can be avoided.

Note that in the above embodiment, a fixed amount of correction is performed for a while from the start of switching between low ε and high ε, and then the correction amount is gradually reduced to "0", but this invention does not necessarily apply. The present invention is not limited to this, and may be modified to perform correction in an appropriate manner.

Further, in the above embodiment, the compression ratio variable mechanism is of a type in which compression ratio switching control is automatically performed depending on the combustion pressure.
As shown in Japanese Patent No. 25637, etc., the present invention can be similarly applied to those in which compression ratio switching is controlled from the outside. In this case, it is possible to directly detect from the internal signal whether control is being made to a high epsilon state or a low epsilon state, so the region determination using the threshold value TpO described above becomes unnecessary.

Effects of the Invention As is clear from the above explanation, according to the ignition timing control device for a variable compression ratio internal combustion engine according to the present invention, the ignition timing is temporarily retarded when switching from a high compression ratio to a low compression ratio. Also, when switching from a low compression ratio to a high compression ratio, the ignition timing is temporarily adjusted to the advanced side, so the actual compression ratio may not change sufficiently due to the response delay of the variable compression ratio mechanism. Appropriate ignition timing can be provided even when the ignition timing is not present. Therefore, it is possible to reliably prevent knocking due to too much advance of the ignition timing and decrease in output due to too much delay.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a claim correspondence diagram showing the structure of the present invention, Fig. 2 is a structural explanatory drawing showing one embodiment of the ignition timing control device according to the present invention, and Fig. 3 is a variable compression ratio diagram. 4 is a sectional view showing an embodiment of the mechanism, FIG. 4 is a flowchart showing a calculation routine for the ignition timing correction amount in the above embodiment, and FIG.
Characteristic diagram of pO, Figure 6 is a time chart explaining the action when transitioning from high ε region to low ε region, and Figure 7 is a time chart explaining the action during transition from low ε region to high ε region. be. ■...Compression ratio detection means, 2...First timer means, 3
...Second timer means, 4...First correction means, 5...
-Second correction means. Figure 6 Rotation shield for 2 people

Claims (1)

[Claims] (1) In a variable compression ratio internal combustion engine equipped with a variable compression ratio mechanism that switches between a high compression ratio and a low compression ratio according to engine operating conditions, the variable compression ratio mechanism is in a high compression ratio state. compression ratio determination means for determining whether the compression ratio is in a low compression ratio state; first timer means activated when switching from a high compression ratio to a low compression ratio; and first timer means activated when switching from a low compression ratio to a high compression ratio. 2 timer means, and a first timer means for correcting the ignition timing to the retard side according to the elapsed time of the first timer means.
An ignition timing control device for a variable compression ratio internal combustion engine, comprising a correction means and a second correction means for correcting the ignition timing to an advanced side in accordance with the elapsed time of the second timer means.