JPH0337029B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a knocking control device for suppressing knocking in an internal combustion engine.

[Conventional technology]

When the compression ratio of an engine is increased in order to improve its fuel efficiency, knocking often occurs when the throttle valve is wide open, especially in the low to medium speed range. Therefore, in high compression ratio engines, turbocharged engines, etc., it is necessary to suppress the occurrence of knocking in the above-mentioned operating range. One method is to use the area where knocking is thought to occur (hereinafter referred to as the knocking occurrence area).
There is a method in which a knock suppressant such as water, alcohol, or a mixture of water and alcohol is supplied to the engine, and the amount of the knock suppressant is controlled by feedback so that the knocking frequency remains constant. (Reference: Utility Model Application No. 1983-74414, Utility Model Application No. 54-146062).

[Problem to be solved by the invention]

However, according to the knocking feedback control method described above, as long as the knocking frequency is high, the supply amount of the knocking suppressant increases indefinitely, and as a result, for example, the knocking suppressant is mainly water. If so, there is a risk that the ignitability will deteriorate and a misfire will occur.Furthermore, if the knock suppressant is mainly alcohol, there is a problem that plague will occur and the engine will be damaged.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a knocking control device for an internal combustion engine that prevents misfires or damage to the engine.

[Means to solve the problem]

A means for solving the above problem is shown in FIG. That is, the engine is equipped with a knock sensor that detects the knocking frequency ( _NKN ) of the engine. The knock suppressant supply means gradually increases the amount of knock suppressant T _ALC supplied to the engine when the knock occurrence frequency N _KN detected by the knock sensor is greater than a predetermined value B, and on the other hand, when the knock occurrence frequency N _KN is greater than a predetermined value B. When the value is less than B, the amount of knock suppressant T _ALC supplied to the engine is gradually reduced. Also, the amount of knock inhibitor supplied
When T _ALC gradually increases, the upper limit supply value determining means determines whether the amount of knock suppressant T _ALC is greater than the upper limit supply value T _ALCMAX . As a result, when the amount of knock suppressant is greater than the upper limit supply value, the ignition timing retard means retards the ignition timing Θ of the engine.

[Effect]

According to the above-mentioned means, when the supply amount of knock suppressant exceeds the upper limit supply value, knocking is prevented by retarding the ignition timing so that the supply amount of knock suppressant does not exceed the upper limit supply value. Occurrence is suppressed.

〔Example〕

The present invention will be explained in detail below using the drawings.

FIG. 1 schematically shows, as an embodiment of the present invention, an example of an internal combustion engine in which the supply amount of a knock suppressant is controlled in accordance with a signal from a vibration detection element called a knock sensor. In the figure, reference numeral 10 denotes a throttle valve provided in the middle of an intake passage 12 of the engine. An electromagnetic injection valve 16 for a knock suppressant is attached to a surge tank 14 downstream of the throttle valve 10. This injection valve 16
a knock suppressant filled in the tank 18;
For example, water, alcohol, or a mixture of water and alcohol is pressurized by pump 20 and applied via conduit 22 . Note that 24 is a pressure regulating valve for keeping the applied pressure of the knock suppressant constant. The injection valve 16 is connected to the control circuit 24 by wire 2.
When a predetermined injection signal is applied via 6, a pressurized nok suppressant is injected into the surge tank 14 continuously or intermittently in an amount corresponding to the signal.

The cylinder block 28 of the engine is equipped with a knock sensor 3, which is composed of, for example, a piezoelectric element or an electromagnetic element, and which converts mechanical vibrations into electrical amplitude fluctuations.
0 is attached. The detection signal from the knock sensor 30 is sent to the control circuit 24 via line 32.

In the intake passage 12 downstream of the throttle valve 10,
A pressure detection section of a pressure sensor 34 that detects the pressure inside the intake pipe and generates a voltage corresponding to the detected value is in communication. The output voltage of this pressure sensor 34 is sent to the control circuit 24 via a line 35.

The distributor 36 of the engine is provided with a crank angle sensor 38 that generates an angular position signal every time the distributor shaft 36a rotates by a predetermined angle, for example, 30 degrees in terms of crank angle. The angle signal from the crank angle sensor 38 is sent to the control circuit 24 via line 40.

An ignition signal is sent from the control circuit 24 to the igniter 44 via a line 42, so that the igniter 44 controls energization and de-energization of the primary current of the ignition coil 46. The high voltage secondary current obtained from the ignition coil 46 is sent to the ignition plug 48 via the distributor 36.

FIG. 2 is a block diagram showing an example of the control circuit 24 of FIG. 1.

The output voltages from the knock sensor 30 and the pressure sensor 34 are sent to an A/D converter 50 having an analog multiplexer function, and are converted into binary signals sequentially or in a specified order at a predetermined conversion cycle.

Angle signals for every 30 degrees of crank angle from the crank angle sensor 38 are sent to a speed signal forming circuit 52 and further sent to a central processing unit (CPU) 54 for a crank angle synchronization interrupt signal. This speed signal forming circuit 52 includes a gate that is controlled to open and close by the above-mentioned signal every 30 degrees of crank angle, and a counter that counts the number of clock pulses from the clock generation circuit 56 that pass through this gate. , forming a binary speed signal having a value depending on the rotational speed of the engine.

When a binary injection signal representing the amount to be injected to a predetermined position of the output port 60 is given from the CPU 54 via the bus 58, the drive circuit 62 generates a rectangular wave injection signal with a variable duty ratio or a variable current value. A continuous injection signal having . As a result, the injection valve 16 discharges the knock suppressant into the surge tank 14 at a flow rate corresponding to the duty ratio or current value of the injection signal.

The ignition control circuit 64 receives, via the bus 58, output data regarding the start timing of energization of the ignition coil 64 and output data regarding the energization end time, that is, the ignition timing, which are calculated by the CPU 54 using a well-known method. 2 registers, two presettable down counters for generating trigger pulses at the points indicated by each output data, and energizing the ignition coil by being set and reset by the above-mentioned trigger pulses from the down counters. It is equipped with a flip-flop that generates an ignition signal indicating when to fire. Ignition control circuits of this type are well known and the generated ignition signal is
The fuel is sent to an ignition device 66 that includes a spark plug 48, a distributor 36, an ignition coil 46, etc. shown in FIG. Note that the same function as the above-described ignition control circuit may be executed by software on the CPU 54 side.

A/D converter 50, speed signal forming circuit 52, output port 60, and ignition control circuit 64 are components of a microcomputer, such as CPU 54, read-only memory (ROM) 68, random access memory (RAM) 70, and It is connected to a clock generation circuit 56 via a bus 58, and data is transferred via this bus 58.

Although not shown in FIG. 2, the microcomputer is provided with an input/output control circuit, a memory control circuit, etc. in a well-known manner.

The ROM 68 stores in advance a main processing routine program to be described later, a well-known interrupt processing program for calculating ignition timing, and various data, maps, tables, etc. necessary for these calculations.

Although omitted in FIG. 2, the output signal of the knock sensor 30 has a buffer circuit for impedance conversion and a knocking-specific frequency (7 to
8kHz) is sent to the A/D converter 50 via a bandpass filter circuit, etc., which is a pass band.
If the response characteristics of the A/D converter 50 cannot follow changes in the output signal of the knock sensor 30, a peak hold circuit is provided to detect the peak value of the output signal of the knock sensor 30 during a predetermined crank angle period. A/D output of hold circuit
It may be configured to convert. Furthermore, a comparison reference value for knock determination, which will be described later, or a reference value to be compared with the output signal value of the knock sensor 30 may be configured to be varied in accordance with the output signal value of the knock sensor 30 during a period in which no knock occurs.

Next, the processing contents of the above-mentioned microcomputer will be explained.

The CPU 54 is in the middle of its main processing routine,
Alternatively, in a system equipped with the peak hold circuit described above, the process shown in FIG. 3 is executed in a predetermined interrupt processing routine. First, in step 80, input data V _KN corresponding to the output signal of the knock sensor 30 stored in a predetermined area of the RAM 70 after A/D conversion is fetched. In the next step 81, input data V _KN and comparison reference value B
When V _KN ≧B, it is determined that knocking has occurred, and when V _KN <B, it is determined that knocking has not occurred. As mentioned above, this comparison standard value B
may be a constant value or may be a variable value.

If it is determined that knocking has occurred, the process proceeds to step 82, where it is determined whether or not the injection signal value T _ALC corresponding to the supply amount of the knock suppressant exceeds its upper limit value A _ALCMAX . If T _ALC is less than its upper limit value T _ALCMAX , the process proceeds to step 83 where T _ALC is increased by a constant value _α1 , and in the next step 84 this T _ALC
is sent to the output port 60. This increases the amount of knock suppressant supplied. In this way, if knocking occurs, proceed to step 8.
The program is executed through routes 1, 82, 83, and 84, and the amount of knock inhibitor supplied is gradually increased. However, T _ALC is its upper limit.
If knocking still occurs after T _ALCMAX is exceeded, the program continues from step 82 to step 8.
5, the advance angle correction value Δθ is decreased by a certain amount β ₁ in order to control the ignition timing in the retarded direction.
If knocking still occurs, the process of passing through step 85 is repeated, and the ignition timing is gradually controlled in the retarded direction.

On the other hand, if it is determined in step 81 that no knocking has occurred, control that is completely opposite to that described above is performed. That is, in step 86, it is determined whether T _ALC is less than or equal to its lower limit value T _ALCMIN .
If T _ALC is greater than T _ALCMIN , step 87
This T _ALC is decreased by a constant value α ₂ .
Therefore, if no knocking continues, the amount of knock suppressant supplied will be gradually reduced, and if the amount is reduced to the lower limit, generally zero, then the ignition timing will change. The angle is gradually controlled in the advance direction. This is achieved by increasing the advance angle correction value Δθ by a constant value β ₂ in step 88 and repeating the process through step 88.

FIG. 4 shows a processing routine for calculating ignition timing using the advance angle correction value Δθ.

The CPU 54 executes the processing routine shown in FIG. 4 every time the crankshaft rotates to a predetermined rotational reference position. First, in step 90, the RAM 70
The data related to the intake pipe internal pressure P and the data related to the rotational speed N stored in a predetermined area are taken in. In the next step 91, the basic ignition advance angle θ _ppt is calculated from these captured data.
Various methods are known for calculating this θ _ppt , and for example, it may be calculated from a map of θ _ppt with respect to θ and P that is stored in advance in the ROM 68. Next, in step 92, θ←
A calculation of θ _ppt +Δθ is performed, and the ignition timing is advanced by Δθ. However, if Δθ is negative, the angle will be delayed. Next, in step 93, the crank angle between θ obtained as described above and the reference angular position is calculated, and the time required for the crankshaft to rotate by the calculated angle is calculated. is converted into the count value of a presettable down counter in the ignition control circuit 64. In the next step 94, the output data thus obtained is set in a register within the ignition control circuit 64. As a result, the ignition timing is
Control is performed at a time corresponding to θ _ppt +Δθ.

〔Effect of the invention〕

As explained above, according to the present invention, an upper limit is set for the supply amount of the knock suppressant, so when the knock suppressant is mainly water, deterioration of ignitability can be prevented, and misfires can therefore be prevented. In addition, if the knock suppressant is mainly alcohol, it is possible to prevent a break from occurring, thus preventing damage to the engine, and when the knock suppressant supply reaches the upper limit, the ignition is stopped. Since the timing is delayed, it is possible to sufficiently prevent the occurrence of knotting.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the control circuit of FIG. 1, and FIGS.
The figure is a flowchart of a part of the processing program of the microcomputer in the control circuit, and FIG. 5 is a block diagram showing the basic configuration of the present invention. 10...throttle valve, 12...intake passage, 1
6... Injection valve, 18... Tank, 20... Pump, 22... Pressure regulating valve, 24... Control circuit, 2
8... Cylinder block, 30... Knock sensor, 34... Pressure sensor, 38... Crank angle sensor, 46... Ignition coil, 48... Spark plug, 50... A/D... Converter, 52... Speed Signal forming circuit, 54... CPU, 60... Output port,
64...Ignition control circuit, 66...Ignition device, 68
...ROM, 70...RAM.

Claims (1)

[Claims] 1. A knock sensor 30 that is attached to an internal combustion engine and detects the knocking frequency (N _KN ) of the engine.
and when the detected knocking frequency is greater than a predetermined value (B), the amount of knock suppressant (T _ALC ) supplied to the engine is gradually increased; B) means for supplying a knock suppressant to gradually reduce the amount of knock suppressant (T _ALC ) fed to said engine when the amount of knock suppressant (T ALC ) is smaller; upper limit supply value determining means for determining whether or not the amount of knock suppressant (T _ALC ) is greater than the upper limit supply value (T _ALCMAX ); ignition timing retarding means for retarding the ignition timing.