JPH11190236A - Device for suppressing knocking of four cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate an engine at a better thermal efficiency by ensuring that knocking is suppressed. SOLUTION: A device for suppressing the knocking of a 4-cycle engine, having a valve opening/closing timing changing means for making the timing of opening and closing of a suction valve 8 and/or an exhaust valve 9 variable relative to the phase of a crankshaft, and provided with a knock sensor for detecting knocking, subjects the timing of opening and closing of the valve to feedback control to retard or advance it depending on whether or not knocking takes place. The device may also subject ignition timing to feedback control to retard or advance it depending on whether or not knocking takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knocking suppressing device for a four-stroke engine, which suppresses the occurrence of knocking in the four-stroke engine.

[0002]

2. Description of the Related Art The above knocking suppression (suppression) device includes:
Conventionally, there is one disclosed in Japanese Patent Application Laid-Open No. 6-129271.

According to this, a variable intake valve opening / closing timing mechanism for varying the opening / closing timing of an intake valve, a control unit for a variable intake valve opening / closing timing mechanism to which a map is connected, and an engine speed for detecting an engine speed are provided. In an engine provided with a number sensor and an air flow sensor for detecting an intake air amount, knocking is suppressed by retarding the valve closing timing by a variable intake valve opening / closing timing mechanism.

When the intake valve closing timing is retarded, the amount of retard is determined based on a map assigned to the engine speed and the average effective pressure.
That is, in the retard control, the control unit reads out the retard amount according to the engine speed and the throttle opening or the output of the air flow meter from the map, and the variable mechanism is controlled.

Further, by controlling the intake valve closing timing based on the retard amount map, an optimal opening / closing valve timing can be selected. As a result, there is no need to delay the ignition timing in order to suppress knocking.

[0006]

However, if the on-off valve timing is controlled according to a previously prepared map as described above, there is a limit in improving the engine output and fuel efficiency. Considering mass production, individual differences between engines and variations in compression ratio among cylinders in one engine always exist, and considering practicality, carbon deposits in the combustion chamber For example, the compression ratio may change over time, and the compression ratio at which knocking may occur depends on the properties of the fuel used and the intake air temperature and density. This is because it is necessary to set the retard amount in a region where the retard does not occur.

Therefore, in the range of the above-mentioned conventional technology,
Since the opening and closing timing of the intake valve needs to be set with a margin in a retard amount region where knocking does not occur, there is a limit in improving the engine output and fuel efficiency.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to make it possible to suppress the occurrence of knocking more reliably and to operate the engine with better thermal efficiency. Make it an issue.

[0009]

Means for Solving the Problems A knocking suppression device for a four-stroke engine according to the present invention for solving the above problems is as follows.

The invention of claim 1 is provided with a valve opening / closing timing varying means 20 for varying the opening / closing timing of the intake valve 8 and / or the exhaust valve 9 with respect to the phase of the crankshaft. In a knocking suppression device for a four-stroke engine provided with a knock sensor 27 for detection,

According to the present invention, feedback control is performed such that the opening / closing valve timing is retarded or advanced in accordance with the knocking occurrence situation.

According to a second aspect of the present invention, in addition to the first aspect, feedback control is performed such that the ignition timing is retarded or advanced according to the occurrence of knocking.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, reference numeral 1 denotes a main part of a four-cycle engine which is an internal combustion engine mounted on a vehicle such as an automobile or a motorcycle.

In the engine 1, a piston 4 is slidably fitted into a cylinder hole 3 of a cylinder 2, and the piston 4 is connected to a crankshaft. A space surrounded by the piston 4 and the cylinder head 5 of the cylinder 2 in the cylinder hole 3 is defined as a combustion chamber 7, and an intake passage communicating from the outside of the cylinder 2 to the combustion chamber 7 is opened and closed. An intake valve 8 is provided, and an exhaust valve 9 that opens and closes an exhaust passage that connects the combustion chamber 7 to the outside of the cylinder 2 is provided. A throttle valve is provided upstream of the intake passage.

The cylinder head 5 is provided with a valve mechanism 12. The valve mechanism 12 includes an intake camshaft 13 cam-engaged with the intake valve 8 and an exhaust camshaft 14 cam-engaged with the exhaust valve 9, each of which is individually wound around a chain around the crankshaft. Linked by means 15
The intake valve 8 and the exhaust valve 9 are operated to open and close in conjunction with the crankshaft.

Ignition plug 1 with discharge section facing combustion chamber 7
Further, a fuel injection valve 18 for supplying fuel to either the intake passage or the combustion chamber 7 is provided.

1 and 2, during the operation of the engine 1, the intake camshaft 13 opens the intake valve 8 at a predetermined opening / closing valve timing (crank angle) during the intake stroke, so that the intake valve 8 is opened for a certain time. The open state is maintained only during the valve opening period A (crank angle). At this time, the intake air is supplied to the combustion chamber 7 together with the fuel injected by the fuel injection valve 18 through the intake passage and the throttle valve. You.

Next, in the compression stroke, the intake air is compressed in the combustion chamber 7.

In the next explosion stroke, the intake air is
7 ignites and burns.

In the next exhaust stroke, the exhaust valve 9 is opened by the exhaust cam shaft 14 at a predetermined opening / closing valve timing.
The valve-open state is maintained only during a certain valve-opening period B. At this time, the gas generated by the combustion in the combustion chamber 7 is discharged to the outside of the cylinder 2 through the exhaust passage as exhaust gas.

A valve opening / closing timing varying means 20 for varying the opening / closing timing of the intake valve 8 and / or the exhaust valve 9 with respect to a certain phase (crank angle) of the crankshaft is provided. More specifically, the intake valve variable means 21 for varying the opening / closing timing of the intake valve 8 while keeping the opening period A of the intake valve 8 constant is provided by the intake camshaft 13 and the chain winding means 15. It is interposed between and. The exhaust valve 9
The exhaust valve variable means 22 for varying the opening / closing valve timing of the exhaust valve 9 is provided between the exhaust camshaft 14 and the chain winding means 15 while keeping the valve opening period B constant.

In FIG. 2, a control device 24 for electronically controlling the intake valve variable means 21 and the exhaust valve variable means 22 is provided. The control device 24 includes an engine speed sensor 25 for detecting the rotation speed of the engine 1, a throttle opening sensor 26 for detecting the load of the engine 1 by detecting the opening of the throttle valve, and a knocking occurrence state (frequency). , Intensity, etc.) are electrically connected to each other.

The control device 24 includes an engine speed calculating means, a throttle opening calculating means, an ignition timing correction amount calculating means, a fuel correction amount calculating means, a phase detecting means, and a correction for correcting the opening / closing valve timing to retard and advance. It has an amount calculating means and a knock strength determining means. An engine speed sensor 25 is connected to the engine speed calculating means, a throttle opening sensor 26 is connected to the throttle opening calculating means, and an ignition plug 17 is connected to the ignition timing correction amount calculating means via the ignition timing correcting means. The fuel injection valve 18 is connected to the fuel correction amount calculating means via the fuel correcting means, and the knock sensor 27 is connected to the knock strength determining means.

In all of the drawings, during normal operation of the engine 1 during which no knocking occurs in the engine 1, the variable intake valve means 21 and the variable exhaust valve means 22 are controlled by a map provided in the control device 24. Then, the intake valve 8 and the exhaust valve 9 have their valve opening periods A and B, respectively.
The opening / closing valve timing is controlled to be retarded and advanced while keeping the constant, thereby improving the engine performance.

On the other hand, according to the knocking occurrence situation detected by the knock sensor 27, the valve opening / closing timing varying means 20 causes the opening / closing valve timing of the intake valve 8 or the exhaust valve 9 to be retarded or advanced. Feedback control is performed by the control device 24.

By the way, in the above-mentioned prior art, there is provided intake valve variable means for varying the opening / closing valve timing of the intake valve while keeping the opening period of the intake valve constant. When knocking occurs, the opening / closing valve timing of the intake valve is retarded by the intake valve variable means.

As described above, when knocking occurs during low-speed, high-load operation of the engine, the opening / closing valve timing of the intake valve is retarded by the intake valve variable means.
The opening and closing timing of the intake valve is delayed during the intake stroke. For this reason, firstly, the overlap period between the opening / closing valve timing of the intake valve and the opening / closing valve timing of the exhaust valve in the exhaust stroke preceding the intake stroke is shortened. Mixing into the intake air in the intake stroke is suppressed, and therefore, the intake air is prevented from being heated by the high heat of the exhaust gas.

Secondly, as described above, the delay in the opening / closing timing of the intake valve shortens the substantial compression period in the compression stroke subsequent to the intake stroke, thereby lowering the compression ratio of the intake air. Let me do.

That is, as described above, the intake air is prevented from being heated by the high heat of the exhaust gas, and the compression ratio is reduced, so that the occurrence of subsequent knocking is suppressed. .

However, in the above-described conventional technique, the occurrence of knocking at low speed and high load is suppressed, but the knocking occurring at high speed and high load is not considered. The technique described above is not sufficient to more reliably suppress knocking over the entire speed range of the engine, and leaves room for improvement. Then, in order to solve the above-mentioned inconvenience, especially, it is constituted as follows.

That is, when knocking occurs at the time of low speed and high load during the operation of the engine 1, the intake valve variable means 2 which is feedback-controlled by the control device 24.
1, the opening / closing valve timing of the intake valve 8 is controlled to be retarded E while the valve opening period A thereof is kept constant, as shown by a dashed line in FIG.

On the other hand, when knocking occurs during high speed and high load of the engine 1, the intake valve 8 is indicated by a two-dot chain line in FIG. Thus, the opening / closing valve timing is subjected to the advance control H while the valve opening period A is kept constant.

Each feedback control by the control device 24 will be described in detail. The following (P-
Although not shown, 1) to (P-8) show each step of the program.

The start of the knocking suppression routine (P-1) interrupts the control of the control device 24 during the normal operation of the engine 1 described above.

As shown in FIG. 1, when the detection signal detected by the knock sensor 27 exceeds a predetermined knock determination level C, the knock intensity determination means determines that the knock intensity is large, and the knock intensity determination is performed. signal n _n is output (P-2).

Next, the engine speed is detected by the engine speed sensor 25, the engine speed is calculated by the engine speed calculating means (P-3), and the engine speed is smaller than a predetermined value. It is determined whether or not (P-4).

In (P-4), it is determined that the engine speed is lower than a predetermined value, and although not shown,
If it is determined that the load is high based on the detection signal of the throttle opening sensor 26, that is, if it is determined that the engine 1 is in a low speed and high load state, (P-5) is executed.

In the above (P-5), the above (P-4)
Is determined by the intake valve variable means 21 by the intake valve 8
The opening / closing valve timing is detected by a phase detection means from a reference value, that is, how much the phase is advanced or retarded from the basic phase D shown in FIG. 3, that is, the phase of the intake valve variable means 21 is detected. Is done. Next, the engine 1
In order to obtain a retard amount to be set with reference to the basic phase D at the time of low speed and high load, the correction amount of the phase of the intake valve variable means 21 is calculated by the correction amount calculating means.

The phase of the intake valve variable means 21 is corrected by the calculated value of the correction amount in (P-5) (P-6).

This will be described in more detail with reference to FIGS. ₁ and _{3. When} knock intensity determination signals N ₁ to N ₃ are successively output by the knock intensity determination means, the intake valve variable means 21 responds to the above according to the output. The retard control E ₁ to E _{3 is} successively performed so that the opening / closing valve timing of the intake valve 8 is further retarded. In the retard control E, the knock intensity determination signal N is set to a predetermined period F
If not generated by the correction amount calculating means, it is the retard control E ₄ so as to retard is decreased a predetermined amount.

As described above, when knocking occurs during low-speed and high-load operation of the engine 1, the opening / closing valve timing of the intake valve 8 is retarded E by the intake valve variable means 21. 8 will be delayed. For this reason, first, the overlap period G between the opening / closing valve timing of the intake valve 8 and the opening / closing valve timing of the exhaust valve 9 in the exhaust stroke preceding the intake stroke is shortened. Of the exhaust gas is suppressed from being mixed into the intake air in the intake stroke, and therefore, the intake air is prevented from being heated by the high heat of the exhaust gas ("first operation").

Secondly, as described above, the delay in the opening / closing timing of the intake valve 8 shortens the substantial compression period in the compression stroke subsequent to the intake stroke, and thus the compression ratio of the intake air is reduced. Reduced ("second effect").

That is, as described above, the intake air is prevented from being heated by the high heat of the exhaust gas, and the compression ratio is reduced, whereby the occurrence of subsequent knocking is suppressed. .

On the other hand, if it is determined in (P-4) that the engine speed exceeds the predetermined value, and it is determined that the load is high based on the detection signal of the throttle opening sensor 26 (not shown). That is, if it is determined that the engine 1 is in the high-speed, high-load state, (P-8) is executed.

In the above (P-8), the above (P-4)
Is determined, the phase of the intake valve variable means 21 is detected in the same manner as in (P-5). next,
In order to obtain an advance amount to be set with reference to the basic phase D when the engine 1 is running at a high speed and a high load, the correction amount of the phase of the intake valve varying means 21 is calculated by the correction amount calculating means.

The phase of the intake valve varying means 21 is corrected by the calculated value of the correction amount in (P-8) (P-6).

This will be described in detail with reference to FIGS. ₁ and _{3. When} knock intensity determination signals N ₁ to N ₃ are successively output by the knock intensity determination unit, the intake valve variable unit 21 responds to the above according to the output. The advance control H ₁ to H ₃ is performed one after another so that the opening / closing valve timing of the intake valve 8 is further advanced. In this advancing control H, knock intensity determination signal N if not a predetermined period F generated by the correction amount calculating means, the advance is advance control H ₄ so as to be reduced a predetermined amount.

As described above, when knocking occurs during high-speed, high-load operation of the engine 1, the opening / closing valve timing of the intake valve 8 is advanced by the intake valve variable means 21 so that the intake valve is controlled during the intake stroke. As the opening / closing valve timing of No. 8 is advanced, the inertia effect is reduced, and as a result, the intake air amount is reduced ("third operation").

That is, as described above, the occurrence of knocking is suppressed by increasing the exhaust gas mixing rate and decreasing the intake air amount.

When the engine 1 is operated at a low speed and a high load, and when the engine 1 is operated at a high speed and a high load, the opening / closing timing of the intake valve 8 is selected from either the retard control E or the advance control H. The reason is as follows. That is, the inertia effect of the intake air greatly differs between when the engine 1 is running at a low speed and when the engine 1 is running at a high speed. Therefore, as described above, when either the retard control E or the advance control H is selected at each speed, This is because the “first and second actions” and the “third action” are remarkably obtained at each speed.

By the "first to third actions", the occurrence of knocking is more reliably suppressed over the entire speed range of the engine 1.

In FIG. 1, when the opening / closing valve timing of the intake valve 8 is retarded E or advanced H by the control device 24, the exhaust valve variable The opening / closing valve timing of the exhaust valve 9 is advanced by the means 22 as shown by a broken line in FIG.

For this reason, when the engine 1 is at a low speed and a high load, the overlap period G is further shortened by the earlier opening / closing timing of the exhaust valve 9, and the above-mentioned "first operation" is achieved.
Is generated, that is, the heating of the intake air by the exhaust gas is more reliably suppressed, and the occurrence of knocking is further suppressed.

As described above, when the engine 1 is running at a high speed and a high load, the opening / closing timing of the exhaust valve 9 is advanced, so that the overhung, which has been lengthened by the advance control H of the opening / closing timing of the intake valve 8, is performed. The lap period G is shortened.

Here, if the overlap period G is too long, the suction effect becomes excessive and the volume efficiency η _v may become too high, which may cause knocking.

Therefore, as described above, by making the opening / closing timing of the exhaust valve 9 advance control I, the overlap period G is prevented from becoming too long.
For this reason, the volumetric efficiency η _v is prevented from becoming too high, and the intake air amount is suppressed, so that the occurrence of knocking is more reliably suppressed.

In the above case, G ≒ I or G <
If I, the overlap period G tends to be shorter, the volume efficiency η _v becomes lower, and the occurrence of knocking is further suppressed.

As described above, since the feedback control is performed so that the opening / closing valve timing is retarded or advanced in accordance with the knocking occurrence situation, for example, the knock intensity in the knocking occurrence situation is stored in the control device 24. If the stored upper limit level is exceeded, a knock intensity determination signal N is output, and a retard control signal is sent to the valve opening / closing timing variable means 20 to delay the opening / closing valve timing.

When the opening / closing valve timing is actually retarded and the knock intensity falls below a certain lower limit level stored in the control device 24, the knock intensity determination signal N stops, and the valve opening / closing timing is advanced to advance the opening / closing valve timing. The advance control signal is sent to the variable means 20.

The advance and retard controls are repeatedly and repeatedly performed, that is, feedback control is performed. At this time, if the upper and lower limit levels are set to close values, knocking of the on-off valve timing is reduced. Control is continued so as to converge to a state where a maximum air suction amount and a compression ratio that do not occur are obtained. That is, it is possible to continue operating the engine 1 with the best thermal efficiency.

According to this method, even when there is an individual difference such as a compression ratio in a mass-produced engine, the best opening / closing valve timing can always be obtained for the individual engine.

Further, in the above configuration, feedback control is performed so that the ignition timing is retarded or advanced according to the occurrence of knocking.

Here, for example, when knocking with an intensity exceeding a certain upper level is detected and the opening / closing valve timing is controlled to be retarded, the opening / closing valve timing depends on the valve opening operation angle of each of the valves 8 and 9. It is conceivable that the valve starts lifting before the retarding operation is completed.

Then, in that cycle, it is conceivable that knocking occurs again with the same ignition timing.

Therefore, in the above case, knocking can be suppressed by retarding the ignition timing.

Further, in a multi-cylinder engine, the knocking occurrence status of each cylinder is not always the same due to the variation of the components. For this reason, the opening and closing valve timing is generally controlled by feedback in the advance and retard ranges below a certain level of knocking in all cylinders, and further, the ignition timing is feedback controlled in accordance with the knocking situation of the corresponding cylinder to optimize the engine. It is possible to operate in a state of high thermal efficiency.

Although the above description is based on the illustrated example, if it is simply determined that the load is high when knocking occurs, the throttle opening sensor 26 and the throttle opening calculating means may be omitted. Further, although the opening / closing valve timing of the exhaust valve 9 is controlled to be advanced based on the occurrence of knocking, this need not be the case.

[0069]

The effects of the present invention are as follows.

The invention according to claim 1 is provided with a valve opening / closing timing varying means for varying the opening / closing timing of the intake valve and / or the exhaust valve with respect to the phase of the crankshaft, and detects knocking. In a knocking suppression device for a four-stroke engine provided with a sensor,

Feedback control is performed so that the opening / closing valve timing is retarded or advanced in accordance with the occurrence of knocking.

For this reason, for example, when the knock intensity in the knocking occurrence situation exceeds a certain upper limit level stored in the control device, a knock intensity determination signal is output, and the valve opening / closing timing is changed to retard the opening / closing valve timing. A retard control signal is sent to the means.

When the opening / closing valve timing is actually retarded and the knock intensity falls below a certain lower limit level stored in the control device,
The knock intensity determination signal stops, and the advance control signal is sent to the valve opening / closing timing variable means to advance the opening / closing valve timing.

The advance / retard control is repeatedly and repeatedly performed, that is, feedback control is performed. At this time, if the upper and lower limit levels are set to close values, the opening / closing valve timing can knock. Control is continued so as to converge to a state where a maximum air suction amount and a compression ratio that do not occur are obtained. That is, it is possible to keep the engine running with the best thermal efficiency.

According to this method, even when there is an individual difference such as a compression ratio in a mass-produced engine, the best opening / closing valve timing can always be obtained for the individual engine.

According to a second aspect of the present invention, feedback control is performed such that the ignition timing is retarded or advanced in accordance with the state of occurrence of knocking.

Here, for example, when knocking with an intensity exceeding a certain upper limit level is detected and the opening / closing valve timing is controlled to be retarded, depending on the valve opening operating angle of each valve, the retarding of the opening / closing valve timing is performed. It is possible that the valve starts to lift before the operation is completed.

Then, in that cycle, knocking may occur again with the same ignition timing.

Therefore, in the above case, the occurrence of knocking can be suppressed by retarding the ignition timing.

Further, in a multi-cylinder engine, the knocking occurrence status of each cylinder is not always the same due to the variation of the components. For this reason, the opening and closing valve timing is generally controlled by feedback in the advance and retard ranges below a certain level of knocking in all cylinders, and further, the ignition timing is feedback controlled in accordance with the knocking situation of the corresponding cylinder to optimize the engine. It is possible to operate in a state of high thermal efficiency.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relation over time of a stroke of four cycles, the operation of intake and exhaust valves, a knock sensor detection signal, and a knock intensity determination signal.

FIG. 2 is a plan partial sectional view of the engine.

FIG. 3 is a diagram showing the opening / closing valve timing of an intake valve over time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 8 Intake valve 9 Exhaust valve 20 Valve opening / closing timing variable means 21 Intake valve variable means 22 Exhaust valve variable means 24 Controller 25 Engine speed sensor 26 Throttle opening sensor 27 Knock sensor A Opening period B Opening period E Delay Angle control G Overlap period H Lead angle control I Lead angle control

Claims (2)

[Claims] 1. A system comprising: a valve opening / closing timing varying means for varying the opening / closing timing of an intake valve and / or an exhaust valve with respect to a phase of a crankshaft; and a knock sensor for detecting a knocking occurrence situation. A knocking suppression device for a four-stroke engine, wherein feedback control is performed such that the opening / closing valve timing is retarded or advanced in accordance with the occurrence of knocking. 2. The knocking suppression device for a four-stroke engine according to claim 1, wherein feedback control is performed such that the ignition timing is retarded or advanced in accordance with the occurrence state of knocking.