JPS6316137A - Control of engine equipped with variable compression ratio mechanism - Google Patents

Abstract

PURPOSE:To prevent the breakage of an engine by increasing the fuel feed quantity when knocking is generated even if the ignition timing is corrected and the compression ratio is reduced, and then fixing the fuel feed quantity and the ignition timing at the value in idling when knocking is generated. CONSTITUTION:In an engine equipped with a variable compression ratio mechanism equipped with an eccentric bearing 6 between a piston pin insertion hole 5 on a connecting rod 3 and the outer periphery of a piston pin 4, the ignition timing is delayed by a controller 23, and the compression ratio is reduced, when a knock sensor 30 detects knocking. When said knocking continues, the injection quantity of fuel supplied from injectors 34-47 is increased for a certain time, and when knocking continues as yet, the fuel injection quantity and ignition timing are fixed at the values in the same conditions to those in idling. Therefore, even if the variable compression ratio mechanism is in broken state, the load for the engine can be reduced, and breakage can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling an engine equipped with a variable compression ratio mechanism.

[Conventional technology]

In internal combustion engines, increasing the compression ratio improves combustion efficiency, improves fuel efficiency, and improves shaft torque, so it is desirable to increase the compression ratio. However, if the compression ratio is increased too much, there will be adiabatic compression in the combustion chamber, which will easily cause ignition (and knocking) when the temperature rises.
Increase in compression ratio is limited. Knocking tends to occur at high loads when a large amount of air is sucked into the combustion chamber, and is less likely to occur at light loads when the amount of air sucked in is small and the actual degree of compression in the combustion chamber is small. Therefore, the compression ratio should be adjusted according to the load. It is desirable that the compression ratio be made variable so that the compression ratio, which is set to be appropriate for medium to high loads, is increased during light loads. In this sense, many variable compression ratio mechanisms for internal combustion engines have been proposed.

As one of the mechanisms for varying the compression ratio in internal combustion engines,
A variable compression ratio mechanism using an eccentric bearing is known (for example, Japanese Patent Application Laid-Open No. 58-91340, No. 91340) In an engine with a reduction ratio mechanism, when knocking occurs, the compression ratio can generally be lowered. One countermeasure is to lower the compression ratio. If knocking still occurs, the ignition timing is corrected to the retarded side.

[Problem to be solved by the invention] However, if trouble occurs in the compression ratio control mechanism for some reason and the compression ratio becomes uncontrollable, the compression ratio may become uncontrollable (or become uncontrollable), especially at high compression ratios. In this case, retarding the ignition timing alone cannot prevent knocking, and there is a risk of major damage to the engine.Therefore, it would be best to stop the engine as soon as possible, but depending on the circumstances, it may not be possible to stop the engine. Failure to do so may cause further damage.

Therefore, if knocking cannot be prevented due to a problem with the compression ratio control mechanism, engine damage can be prevented by automatically reducing the load on the engine. For example, If knocking cannot be suppressed in a vehicle equipped with a variable compression ratio mechanism, it is possible to automatically reduce the load on the engine to the extent that the vehicle can be driven at a slow speed, thereby preventing the engine from being damaged by knocking. can be protected from.

The present invention focuses on the above points, and in an engine with a variable compression ratio mechanism, when knocking cannot be prevented due to trouble in the compression control mechanism, the load on the engine is automatically reduced. , an object of the present invention is to provide a control method that protects an engine from damage caused by knocking.

[Means for solving problems]

A method for controlling an engine with a variable compression ratio mechanism according to the present invention, which meets this objective, is effective in reducing the supply to the engine when the occurrence of knocking cannot be suppressed even after taking knocking suppression measures including at least ignition timing correction and compression ratio reduction. If the amount of fuel is increased for a certain period of time and knocking still occurs, a control method is used in which the amount of supplied fuel and the ignition timing are fixed to substantially the same conditions as during idling.

Note that when the amount of fuel supplied and the ignition timing are fixed, it is desirable to provide a warning so that troubles can be recognized.

[Effect]

In such a control method for an engine with a variable compression ratio mechanism, if knocking cannot be suppressed even by lowering the compression ratio and correcting the ignition timing to the retarded side, the amount of fuel supplied to the engine is reduced for a certain period of time. The amount will be increased. In other words, more fuel is supplied than during normal operation. Therefore, the temperature of the combustion chamber decreases, and the occurrence of knocking is suppressed. Here, if the knocking is suppressed, it is determined that the knocking is transient and not a failure of the device. - If knocking continues to occur even after the amount of fuel supplied to the engine has been increased for a certain period of time, it is naturally determined that an abnormal situation has occurred. In other words, it is determined that a trouble has occurred in the compression ratio control mechanism. Based on this judgment, the amount of fuel supplied to the engine and the ignition timing are automatically fixed to conditions that are almost the same as when idling, and are controlled so that the load on the engine is minimized.

Therefore, it is possible to protect the engine from knocking, and damage to the engine can be prevented.

〔Example〕

Below, preferred embodiments of the method for controlling an engine with a variable compression ratio mechanism according to the present invention will be described. , will be explained with reference to the drawings.

FIG. 1 shows a control system diagram of an engine with a variable compression ratio mechanism to which the present invention is applied. In FIG. They are connected via a piston pin 4. The piston pin 4 is fixedly or rotatably supported in the piston pin hole of the piston 2.

Between the piston pin insertion hole 5 at the small end of the connecting rod 3 and the outer periphery of the piston pin 4, there is an eccentric bearing 6 whose wall thickness changes in the circumferential direction and whose inner and outer circumferential circles are eccentric from each other. is rotatably installed.

A lock pin storage hole 7 extending in the radial direction of the eccentric bearing 6 is formed at a position of the connecting rod 3 corresponding to the eccentric bearing 6, and a lock pin 8 is slidably inserted into the hole 7 and inserted from the hole 7. The eccentric bearing 6 is housed so as to be able to move in and out of the eccentric bearing 8. On the other hand, a lock pin retaining hole 9 having a diameter that allows the lock pin 8 to move in and out is formed in the thick part of the eccentric bearing 6 in the radial direction. ing. When the lock pin 8 engages with the lock pin engagement hole 9, the piston 2 is kept at a high position and a high compression ratio is achieved, and when the engagement by the lock pin 8 is released, the eccentric bearing 6 freely rotates and compresses. At top dead center, the piston is in a low position, creating a low compression ratio state. That is, in this variable compression ratio side-mounted engine, the compression ratio can be switched to two levels, high and low.

Next, the drive structure of the lock pin 8 will be described. A lock pin locking hydraulic passage lO and a lock pin unlocking hydraulic passage 11 are connected to the lock pin storage hole 7 with the lock pin 8 interposed therebetween.
is opened at a position that urges the lock pin 8 in the direction of the eccentric bearing 6.

Further, a lock pin guide groove 12 is formed on the outer periphery of the eccentric bearing 6 at a position corresponding to the lock pin 8 and extends over the entire circumference in the circumferential direction, and the lock pin retaining hole 9 is provided in this groove 12. It is being

The hydraulic passage 1 provided in the connecting rod 3
0.11 is oil provided independently on the circumference of the bearing at the large end of the connecting rod. They are connected to n14 and n15, respectively. The oil grooves 14 and 15 are connected to oil grooves 18 provided independently from each other on the circumference of the journal bearing of the crankshaft via an oil passage 17 in the crankshaft 16.
．． 19 so that they can communicate intermittently when the crankshaft 16 rotates.

The oil groove 18 can communicate with the lock pin locking hydraulic passage 10 via the oil groove 14, and the oil groove 19 can communicate with the lock pin unlocking hydraulic passage 11 via the oil groove 15.

A main oil passage 20 for high compression ratio and a main oil passage 21 for low compression ratio are provided in the cylinder block, and the main oil passage 20 for high compression ratio is communicated with oil 'a18, The main oil passage 21 is an oil groove 19
is communicated with. The lubricating oil in the oil pan 32 is pumped up by the oil pump 26 and sent to either the high compression ratio main oil passage 20 or the low compression ratio main oil passage 21 via the switching valve 22.

The switching valve 22 is controlled by the ECU (electronic control unit) 2 according to the load.
When the load is medium or high, pressure oil is sent to the main oil passage 21 for low compression ratio, and when the load is light, pressure oil is sent to the main oil passage 20 for high compression ratio. controlled so that

The intake air amount Q detected by the air flow meter 24 and the engine rotation speeds N and E detected by the engine rotation speed sensor 25 are input to the ECU 23, respectively. That is, the ECU 23 controls the intake air IQ and the engine speed NB.
The switching valve 22 is operated in response to an input signal to switch the compression ratio.

The ignition control device consists of an igniter (ignition control circuit) 27 and an ignition coil (path shown), and the igniter 27 is connected to an output port of the ECU 23 to receive and receive an ignition signal. The ignition coil is
It is connected to the central electric bridge of the distributor 28, and high voltage is distributed to the spark plugs 29 of each cylinder according to the rotation of the distribution shaft.

A knock sensor 30 is attached to the cylinder block 1 to detect knocking occurring in the combustion chamber, and the knock sensor 30 is connected to an input port of the ECU 23. The knock sensor 30 uses a resonant knock sensor that has characteristics tuned so that the detection ability is maximized by resonance between the vibration frequency generated by knocking and the natural frequency of the detection element. It will be done. That is, when knocking occurs, a signal at a very high level is input to the knock sensor 3, and when knocking does not occur, a low level signal is manually input to the ECU 23.

Injectors 34, 35, 36, and 37 that inject fuel into each cylinder are connected to the output port of the ECU 23, respectively.

2 to 8 show flow diagrams and map diagrams of each control l in the present invention. The compression ratio and ignition timing map and each control procedure are provided by the CPU 3 of the ECU 23.
1 is preprogrammed.

FIG. 3 shows a flowchart for calculating correction values for the ignition timing and compression ratio switching map.

As shown in FIG. 3, first, an interrupt is made to the CPU 31 in the ECU 23 at a necessary time, and in step 41, it is determined based on a signal from the knock sensor 30 whether or not knocking is occurring. As a result, if knocking has not occurred, the process proceeds to step 42, where it is determined whether or not knocking occurred last time, and if knocking has occurred, the process returns to step 43. If knocking has not occurred, the process proceeds to step 45, where the correction values of the ignition timing map and compression ratio switching map become S-3+1. If it is determined in step 41 that there is knocking, the process proceeds to step 46, where the correction value is set to S-3-1, and then the process returns to step 43. This correction value is added; for example, if knocking is confirmed continuously, the S-
If it is O, it becomes S-12.

FIG. 4 shows a flow diagram of compression ratio switching control.

As shown in the figure, first, the CP in the ECU 23 is
An interruption is made to U, and in step 51 the engine speed NE and intake air amount Q are input as engine operating conditions, and in step 52 the compression ratio is determined. FIG. 5 shows a compression ratio map, and as shown in the figure, the horizontal axis shows the engine speed NE, and the vertical axis shows the ratio Q/NE between the intake air amount Q and the engine speed NB. The graph has a boundary value that separates a high compression ratio region and a low compression ratio region.

In the figure, the standard compression ratio switching map is based on the boundary value 370, and when the boundary value is 5--3 to S-+3,
A corrected compression ratio switching map obtained by correcting the standard compression ratio switching map is shown.

That is, in step 32, the correction value S calculated based on the signal from the knock sensor 30 is input, and the standard compression ratio switching map S-0 is changed to, for example, the corrected compression ratio switching map 5.
− Corrected to −1. And engine speed sensor 2
5 and the air flow meter 24, it is determined whether a high compression ratio or a low compression ratio should be used depending on whether the intersection of the corresponding maps is in a high compression ratio region or a low compression ratio region. It is designed to output the output of what should be done.

Once the compression ratio is determined in step 52, the process proceeds to step 53 where it is determined whether the determined compression ratio is a high compression ratio or a low compression ratio. If the higher compression ratio is selected in step 53, step 5
The process proceeds to step 4, where the compression ratio is flagged, and if the result is a high compression ratio, the process proceeds to step 55, where the process returns. If the high compression ratio is not reached, the process proceeds to step 56, where the high compression ratio is achieved. Then, in step 57, the compression ratio flag is set to FC-1, and then the process returns to step 57.

Note that if the lower compression ratio is selected in step 53, the process proceeds to step 58 and the actual compression ratio flag is determined.

As a result, if the compression ratio is not high, the process returns to step 55, and if the compression ratio is high, the process proceeds to step 59, where a high compression ratio is achieved. Then, in step 60, the compression ratio flag is set to F.
As C-0, the process returns to step 55.

As shown in FIG. 0, which shows a flow diagram of ignition timing control, an interrupt is first made to the CPU 31, and in step 71, the ratio Q between the engine speed NE and the intake air amount Q is shown.
/NE and engine speed NB are input. When each condition is input, the process proceeds to step 72, where the correction value S is input,
Proceed to step 73. In step 73, it is determined whether the compression ratio is high.

That is, it is determined whether the compression ratio flag is FC-1. As a result, if the compression ratio is high, the process proceeds to step 74, where the ignition timing for high compression ratio is corrected by the correction value S. Therefore, the ignition timing is adjusted based on the corrected value in step 74, and then the process proceeds to step 77 and returns.

In this way, by correcting the intake air amount Q/engine speed NE and engine speed NB,
The ignition timing for high compression ratio is adjusted, for example, from A on the ignition timing map to A+SB.

If the result determined in step 73 is a low compression ratio,
Proceeding to step 79, the low compression ratio ignition timing is corrected using the correction value S. Therefore, the ignition timing is adjusted based on the corrected value in step 79, and then the process proceeds to step 77 and returns.

In this case as well, by correcting the intake air amount Q/engine speed NB and engine speed NB as in the case of high compression ratio, the ignition timing for low compression ratio can be adjusted from, for example, C to C+SD. Ru.

FIG. 2 shows a flow diagram for protecting a variable compression ratio engine from damage caused by knocking.

In FIG. 2, in addition to the above-mentioned controls, the amount of fuel supplied to the engine is also controlled.

As shown in the figure, first, the CPU of the ECU 23 is
31 is interrupted, and in step 81 the knock sensor 3 is
Based on the signal from 0, it is determined whether knocking is occurring. As a result, if it is determined that there is knocking, the process proceeds to step 82, where the correction value S is set to the correction limit value S + *in
It is determined whether the target has been reached. Here, the correction value S
has not reached the correction limit value S sin, step 9
0 and corrects the correction value S to S-3-1, then proceeds to step 89 and returns.

If the correction value S has reached the correction limit value S l1in in step 82, the process proceeds to step 83, where it is determined whether the compression ratio is a low compression ratio. That is, the compression ratio flag FC
It is determined whether or not is 0. In this case, if it is determined that the compression ratio is not a low compression ratio, the process proceeds to step 91, where the compression ratio is switched to the low compression ratio, and then proceeds to step 89, where it is returned.

If the result in step 83 is a low compression ratio, step 8
The process proceeds to step 4, where it is determined whether the amount of fuel supplied to the engine is the normal amount of fuel supplied. That is, it is determined whether the timer increase mode flag FT is 0 or not. In this case, if the supplied fuel amount is not the normal supplied fuel amount, the process proceeds to step 92, where the low compression ratio ignition timing and the supplied fuel amount are fixed at substantially the same supplied fuel amount as during idling. That is, the injection amount injected from the injector 34, 35, 36, 37 becomes small, and the ignition timing MR of the ignition timing map for low compression ratio shown in FIG. 8 is corrected to, for example, the ignition timing W. When the correction of the supplied fuel amount and ignition timing in step 92 is completed, the process proceeds to step 93, where an indicator or the like is used to notify that the engine is in an abnormal state.

If it is determined in step 84 that the amount of supplied fuel is in a normal state, the process proceeds to step 85, where it is determined whether the increase in the amount of supplied fuel has been completed. That is, it is determined whether the normal injection amount return flag after timer increase is 0 or not. As a result, if the supplied fuel has returned to its normal state, the process proceeds to step 92, where the supplied fuel amount and low compression ratio ignition timing are fixed to the same conditions as during idling, as described above.

If the normal injection amount return flag FF has not been reset after the timer increase in step 85, the process proceeds to step 86, where an increase command τ for the supplied fuel amount is issued. Then, the process proceeds to step 87, where the fuel increase time is counted by the timer, and the supplied fuel amount is increased for a certain period of time.

After that, proceed to step 88 and set the timer increase mode flag FT.
is set to 1, and then proceeds to step 89 and returns.

Returning to the previous step, if it is determined in step 81 that there is no knocking, the process proceeds to step 94 where it is determined whether the timer increase mode flag FT is 1 or not. In other words, it is determined whether the amount of supplied fuel is being increased. As a result, if the amount is not being increased, the process proceeds to step 99, where it is determined whether the amount of supplied fuel has been restored to the normal amount. Here, if the amount of supplied fuel has not been restored to the normal amount, the process proceeds to step 101 and the correction value is corrected to S=S+1. Thereafter, the process proceeds to step 89 and is returned.

In this way, within the range where knocking can be corrected, correction using the correction value S is always performed in a learning manner.

If it is determined in step 99 that the normal injection amount return flag FF after timer increase is 1, the process proceeds to step 100, where the normal injection amount return flag FF after timer increase is set to 0, and then,
The process proceeds to step 89 and returns.

If the timer increase mode flag FT is determined to be 1 in step 94, that is, if the amount of supplied fuel is being increased, the process proceeds to step 95, where it is determined whether or not the time has expired. As a result, if there is no time up, step 89
and then come back. If the time has expired in step 95, the process proceeds to step 96 and the fuel increase is turned off. The process then proceeds from step 96 to step 97, where the normal injection amount return flag after timer increase is set to 1. After that, proceed to step 98, set the timer increase mode flag FT to 0, and step 8
He will advance to 9 and return.

As mentioned above, if knocking cannot be suppressed even after knocking suppression measures such as lowering the compression ratio and correcting the ignition timing, first increase the amount of fuel supplied to the engine for a certain period of time to reduce the amount of combustion chamber. lower the temperature,
Knocking is suppressed. However, if knocking still occurs, it is determined that there is a problem with the engine's compression ratio control mechanism rather than transient knocking, and the amount of fuel supplied to the engine and the ignition timing for low compression ratio are set to idling. The conditions are fixed to almost the same as those of the time. This minimizes the load on the engine and protects it from damage caused by knocking.

In the present invention, transient knocking is prevented by increasing the amount of fuel supplied, but other methods include, for example, injecting water into the intake manifold,
Possible methods include injection of alcohol into the intake manifold, temporary rapid cooling of intake air, and temporary rapid cooling of engine coolant.

〔Effect of the invention〕

As explained above, when using the control method for a variable compressor horizontally mounted engine of the present invention, if the occurrence of knocking cannot be suppressed even after taking knocking suppression measures including at least ignition timing correction and compression ratio reduction, If the amount of fuel supplied to the engine is increased for a certain period of time and knocking still occurs, the amount of supplied fuel and ignition timing are controlled to be fixed at almost the same conditions as when idling, suppressing transient knocking. This can be countered by lowering the temperature of the combustion chamber. When knocking occurs due to trouble with the compression ratio control mechanism, the engine automatically switches to idling operating conditions, reducing the load on the engine and protecting the engine from damage caused by knocking. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a control system diagram of an engine with a variable compression ratio mechanism to which the present invention is applied, and Fig. 2 is a flow line for protecting the engine with a variable compression ratio mechanism of Fig. 1 from damage caused by knocking. Figure 3 is a flow diagram for calculating correction values for the compression ratio map and ignition timing map, Figure 4 is a flow diagram for compression ratio switching control, and Figure 5 is a standard compression ratio switching map diagram and correction. Compression ratio switching map,
. FIG. 6 is a flow diagram of ignition timing control. 3......Connecting rod 6.
・・・・・・・・・・・・Eccentric bearing 8・・・・・・
・・・・・・Rock Bin 10・・・・・・・・・・・・
Hydraulic passage for lock pin lock 11...
・Hydraulic passage 22 for lock bin unlocking
......Switching valve 23...ECU (electronic control unit) 24...Air flow meter 25
・・・・・・・・・・・・Engine speed sensor 27・
・・・・・・・・・・・・Igniter (ignition control circuit) 2
8...Distributor 29.
・・・・・・・・・・・・Spark plug 30・・・・・・
・・・・・・Knock sensor 31・・・・・・・・・・
・・cpu 34.35.36.37・・・・Injector NE
・・・・・・・・・Engine speed Q・・・・・・・・・
...Intake Air Volume Patent Applicant: Toyota Motor Corporation Representative: Patent Attorney: Tsuneo Degata (and 1 other person) Figure 2 Figure 3

Claims (1)

[Claims] (1) In a method of controlling an engine with a variable compression ratio mechanism,
If the occurrence of knocking cannot be suppressed even after taking knocking suppression measures including at least ignition timing correction and compression ratio reduction, increase the amount of fuel supplied to the engine for a certain period of time, and if knocking still occurs, increase the amount of fuel supplied to the engine. A control method for an engine with a variable compression ratio mechanism, characterized in that the fuel amount and ignition timing are controlled to be fixed to substantially the same conditions as when idling.