JP2763804B2 - Engine knock detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a knock detection device for an engine that performs knock detection at high speed and exclusively.

[Prior Art and Problems to be Solved by the Invention] Recently, a technique of detecting an initial knock due to abnormal combustion of an engine by a knock sensor and controlling ignition timing to avoid knock generation has been widely adopted. The knock control technology makes it possible to advance the ignition timing to the knock limit, thereby greatly improving the output performance of the engine.

The knock sensor detects abnormal combustion pressure vibration due to abnormal combustion of the air-fuel mixture or mechanical vibration transmitted to a cylinder block and outputs the vibration waveform as an electric signal, and processes the vibration waveform of the knock sensor. By determining whether knock has occurred or not and controlling the ignition timing, knock can be avoided.

That is, as disclosed in JP-A-58-30477 and JP-A-61-8472, a knock component is selected by band-limiting a signal from the knock sensor through a filter circuit, and a peak component is selected. The hold circuit holds the peak value of the waveform and performs analog / digital conversion. Then, the average value of the peak values subjected to the analog / digital conversion is calculated by a microcomputer or the like, and is compared with a predetermined knock determination level to determine whether knock has occurred.
Control ignition timing.

However, knock detection processing by one control device,
When executing the ignition timing control or the like, in a region where there is not enough processing time, such as when the engine is running at a high speed, the increase in load cannot be ignored, and there is a possibility that the original engine control may be hindered.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides an engine knock detection device capable of executing knock control at high speed by performing a knock detection process and an engine control in a distributed manner. It is an object.

Means and Action for Solving the Problems In order to achieve the above object, an engine knock detection device according to the present invention includes a control line for transmitting the presence or absence of knock to a main control unit for controlling the engine, and a data exchange. Knock determination means for determining whether or not knock has occurred based on an analog / digital conversion value of the knock sensor output signal and a predetermined knock determination level; and A communication for outputting a determination result to the main control unit via the control line, and transmitting knock data to the main control unit via the serial communication line when the knock determination unit determines that knock has occurred. Means.

That is, when vibration of the engine is detected by the knock sensor, the presence / absence of knock occurrence is determined by knock determination means based on the analog / digital conversion value of the knock sensor and a predetermined knock determination level. The signal is transmitted by means to a main control unit that controls the engine via a control line.

When it is determined by the knock determination means that no knock has occurred, the determination result of no knock occurrence is only transmitted to the main control unit.On the other hand, when it is determined by the knock determination means that knock has occurred, Knock data is transmitted to the main control unit via a serial communication line in addition to the determination result that knock has occurred.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 shows an embodiment of the present invention, FIG. 1 is a functional block diagram of a knock detection unit, FIG. 2 is a circuit configuration diagram, FIG.
FIG. 4 is a flowchart showing a main processing procedure in the knock detection unit, FIG. 4 is a flowchart showing a knock detection procedure, FIG. 5 is a flowchart showing a processing procedure in the main control unit, and FIG. 6 is a timing chart of the knock detection processing. .

(Configuration) Reference numeral 1 in FIG. 2 denotes a main control unit for controlling the engine, which is composed of a microcomputer, to which various sensors such as a crank position sensor 2 are connected via a waveform shaping circuit 2a. Is connected. A knock detection device including a knock detection unit 4 is connected to the main control unit 1, and the knock detection unit 4 is connected to the crank position sensor via the waveform shaping circuit 2a and the amplifier 5, respectively. 2. The knock sensor 6 is connected.

The knock detection unit 4 includes a CPU 7, a ROM 8, a RAM 9, a serial interface (SCI) 10, an analog / digital (A / D) converter 11, timers TM1, TM2, TM3, and an input / output (I / O) interface 12. Are connected to each other via a bus line 13, and are connected via a control line 4a.
An output port (1 bit) of a specific address of the I / O interface 12 is connected to an input port of the main control unit 1, and the SCI 10 and the SCI of the main control unit 1 are connected via a serial communication line 4b. Connected (input port of main control unit 1 and SC
I is not shown).

The crank position sensor 2 is connected to the input port of the I / O interface 12 via the waveform shaping circuit 2a. The knock sensor 6 is connected to the A / D converter via the amplifier 5. Connected to 11.

The crank position sensor 2 includes an electromagnetic pickup or the like that detects a protrusion (or a slit) of the rotor 2b interlocked with the crankshaft of the engine. When the protrusion approaches or separates from the crank position sensor 2 as the rotor 2b rotates. An AC output is generated due to the change in magnetic flux, and is converted into a pulse by the waveform shaping circuit 2a.

For example, in the case of a six-cylinder engine, the top dead center (TDC) of each cylinder that exists every 120 ° CA is 10 ° before the top dead center (BTDC).
The crank angle signal is output from the crank position sensor 2 every 30 ° CA from. That is, BTDC10 °, BTDC40 °,
BTDC 70 ° and BTDC 100 ° crank angle signals are input to the main control unit 1 to calculate ignition timing and the like. When a predetermined ignition timing is reached based on the 30 ° CA signal, the ignition signal is sent to the ignition circuit 3. Is output.

The signal of BTDC10 ° is a fixed ignition angle signal at the time of starting the engine.

Further, a signal indicating, for example, BTDC 10 ° is input from the crank position sensor 2 to the knock detection unit 4 every 120 ° CA, and an interrupt process is started.

The knock sensor 6 is connected with a resistor R from a power supply VCC and has, for example, a vibrator having substantially the same natural frequency as knock vibration, and a piezoelectric element for detecting a vibration acceleration of the vibrator and converting the vibration acceleration into an electric signal. The sensor detects vibration transmitted to a cylinder block or the like by a combustion pressure wave during the explosion stroke of the engine, and outputs the vibration waveform as an electric signal.

After the electric signal is amplified to a predetermined level by the amplifier 5, the A / D converter 11 of the knock detection unit 4
Is A / D converted to digital data. In this A / D conversion, sampling is performed at a high speed in order to faithfully convert the vibration waveform.

The CPU 7 starts an internal interrupt process by the timers TM1, TM2, and TM3 in response to a signal from the crank position sensor 2, and executes a knock detection process program stored in the ROM 8.

In this case, for example, a knock determination map stored in the ROM 8 is searched to set a knock determination level directly or by interpolation calculation, while a signal from the knock sensor 6 is converted to a signal from the A / D converter in a knock detection section. At 11, high-speed A / D conversion is performed to calculate a knock level.

Then, it is determined whether or not knock has occurred by comparing the knock level with the knock determination level, and the determination result is determined as described above.
An output is provided from the output port of the I / O interface 12 to the main control unit 1 via the control line 4a.

As for the knock determination result, 0 is output from the output port of the specific address of the I / O interface 12 when knock occurs, and 1 is output from the output port when no knock occurs.
Is output.

In the main control unit 1, for example, the state of the output port of the I / O interface 12 of the knock detection unit 4 is read in synchronization with the signal from the crank position sensor 2, and when the output port is 0, If there is an occurrence, knock data such as a knock level is read via the serial communication line 4b. Then, based on the knock data, the ignition timing of the corresponding cylinder is immediately delayed to avoid knocking.

(Functional Configuration) The knock detection unit 4 includes an A / D conversion unit 20, a sampling cycle setting unit 21, an engine speed calculation unit 22,
Knock detection section setting means 23, knock level calculation means 24,
Knock determination level setting means 25, knock determination map MPKN,
Knock judging means 26 and communication means 27 execute a function dedicated to knock detection processing at high speed.

In the A / D converter 20, in the knock detection section set by the knock detection section setting section 23, the signal from the knock sensor 6 is sent to the A / D converter 11 at the sampling cycle set by the sampling cycle setting section 21. The data is converted into digital data and output to knock level calculating means 24.

In the sampling cycle setting means 21, in the knock detection section set by the knock detection section setting means 23,
The sampling period of A / D conversion in the A / D conversion means 20 is set, and the A / D conversion means 20, knock level calculation means 2
Output to 4. This sampling period is a time period Ts capable of faithfully reproducing the vibration waveform from the knock sensor 6,
For example, it is set in the timer TM3 at a cycle of Ts = 30 μs.

The engine speed calculating means 22 calculates a time T3 corresponding to a crank angle of 30 ° based on a signal from the crank position sensor 2.
0 is calculated, and the engine speed N is calculated.

The knock detection section setting means 23 sets a knock detection section for the knocking occurrence target period in accordance with the engine speed N calculated by the engine speed calculation means 22,
The signals are output to the A / D conversion means 20, the sampling period setting means 21, and the knock level calculation means 24.

In the knock detection section, for example, a preset map or the like is set directly or by interpolation calculation according to the engine speed N, the start time T1S of the knock detection section is set in the timer TM1, and the timer TM2 ends. Time T1E is set.

In the knock level calculation means 24, in the knock detection section set by the knock detection section setting means 23, the A / A
The amplitude center value P0 of the vibration waveform is subtracted from the digitally achieved Pi for each sampling period Ts converted by the D conversion means 20, and the value is added for each sampling period Ts. Then, after the A / D conversion in the knock detection section is completed, the average value P2 is calculated by dividing by the sampling number S.

That is, Thus, the average value P2 of the knock detection section is calculated, and this is output to the knock determination means 26 as a knock level.

In knock determination level setting means 25, engine speed N
Is used as a parameter to search knock determination map MPKN, and knock determination level PKN is set directly or by interpolation calculation, and output to knock determination means 26.

The knock determination map MPKN is obtained by adding a value obtained by adding a predetermined offset value to the average value P2 calculated in the same manner as the knock level calculation means 24 in a knock non-occurrence target period to a map using the engine speed N as a parameter. The knock determination level P is stored in advance as the determination level PKN, and the knock determination level P
The calculation of KN can be omitted, and the processing speed can be improved.

If the capacity of the CPU 7 of the knock detection unit 4 has a margin, it is needless to say that the knock determination level PKN may be calculated by calculation without using a map search.

In the knock determination means 26, the knock level calculation means 24
The knock level P2 calculated in the above is compared with the knock determination level PKN set by the knock determination level setting means 25.
If <PKN, it is determined that knocking has not occurred, and if P2 ≧ PKN, it is determined that knocking has occurred.

The communication means 27 outputs 0 from the output port of the I / O interface 12 when a knock has occurred, and outputs the I / O when no knock has occurred according to the determination result of the knock determination means 26.
In addition to outputting 1 from the output port of the interface 12, knock data such as knock level P2 is transmitted from the SCI 10 to the main control unit 1 in response to a knock data transmission request from the main control unit 1.

(Operation) Next, the operation of knock detection unit 4 having the above configuration will be described with reference to the flowcharts of FIGS.

First, first, step S101 of the main routine in FIG.
, The interrupt vector, various flags, registers, etc. of the knock detection unit 4 are initialized.

Next, the process proceeds to step S102, where the crank position sensor 2
Then, the interrupt from every 30 ° CA is permitted with respect to the signal from, and the process proceeds to step S103 to determine whether or not the knock occurrence flag FLAG is 1.

The knock occurrence flag FLAG is set to FLAG = 1 when it is determined that knock has occurred and FLAG = 0 when it has been determined that knock has not occurred, as a result of determination by an interrupt process of a timer TM2 described later. , The above step S1
In 03, when FLAG = 0, that is, when no knock has occurred, the process returns to step S103 to monitor the knock occurrence flag FLAG.

On the other hand, if FLAG = 1 in step S103, that is, if knock has occurred, the process proceeds from step S103 to step S1.
Proceeding to 04, it is determined whether or not there is a knock data transmission request from the main control unit 1. If there is no knock data transmission request, the main control unit 1 is ready for communication and performs the above steps until a knock data transmission request is received. S104
When there is a knock data transmission request, the process proceeds to step S105.

Then, in step S105, the knock level P2 detected by the interrupt processing described later and stored in the RAM 9 is set to SC.
110 to the main control unit 1, and
Clears the knock occurrence flag FLAG at 106 (FLAG ← 0)
Then, the process returns to step S103, and the knock occurrence flag FLAG is monitored again.

(Knock Detection Procedure) Next, as shown in FIG. 6, when a crank angle signal of, for example, BTDC10 ° is input from the crank position sensor 2,
The external interrupt processing shown in FIG.
Then, an elapsed time T30 corresponding to a crank angle of 30 ° is calculated. The elapsed time T30 can be measured from the time between the signals from the crank position sensor 2 input every 30 ° CA.

Next, the process proceeds to step S152, the engine speed N is calculated from the value of the elapsed time T30 calculated in step S151, and the process proceeds to step S153.

In step S153, the start time T1 of the knock detection section is determined based on the engine speed N calculated in step S152.
S, that is, the sampling start time T1S of the signal from the knock sensor 6 is set in the timer TM1, and the process proceeds to step S154.

In step S154, the interruption of the timer TM1 is permitted, and the process proceeds to step S155 to calculate the time width TAD1 of the knock detection section based on the engine speed N and return to the main routine.

Next, when an internal interrupt is generated by the timer TM1 at time T1S, the TM1 interrupt step S20 shown in FIG.
At 1, the knock detection section end time T1E (= T1S + TAD
1) is set in the timer TM2, and then in step S202, interruption of the timer TM2 is permitted.

Next, the process proceeds to step S203, where the sampling period TS of the A / D conversion is set in the timer TM3.
A / D conversion by the A / D converter 1 is started immediately by permitting the TM3 interrupt, and the TM1 interrupt is terminated.

That is, when the interruption of the timer TM3 is permitted in the step S204, the TM3 interruption is started as shown in FIG. 4C, and the sampling processing of the A / D conversion value of the vibration waveform from the knock sensor 6 is performed in the step S204. This is executed for each sampling period TS set in S203.

Then, the digital data of the vibration waveform from the knock sensor 6 converted by the A / D converter 11 in step 251 is read, and the process proceeds to step S252.
The difference between the digital data Pi of the vibration waveform read at 51 and the amplitude center value P0 of the vibration waveform, that is, the knock intensity (| Pi−PO |)
Is calculated.

Next, in step S253, the present knock intensity calculated in step S252 is added to the knock intensity integrated value KNP up to the previous sampling to calculate the knock intensity integrated value KNP up to the current sampling (KNP = KNP + | Pi-PO). |), And proceed to step S254.

Proceeding to step S254, the sampling number S up to the previous time
To the sampling number S (S = S +
1) is calculated, and the next sampling timing is set in the A / D converter 11 in step S255, and the routine is terminated.
S251 to S255 are repeated.

Here, the sampling period TS is set to, for example, about 30 μs, and is set so that the vibration waveform from the knock sensor 6 can be faithfully digitized.

When the sampling end time T1E is reached, the fourth
The TM2 interrupt by the timer TM2 shown in FIG.

In this TM2 interrupt, in step S301, the interruption of the sampling process of the A / D conversion value by the timer TM3 is prohibited, and the process proceeds to step S302 to search the knock determination table MPKN using the engine speed N as a parameter.

Next, in step S303, a knock determination level PKN is set directly or by interpolation calculation, and in step S304, the average value P2 of the knock intensity integrated value KNP in the knock detection section is set.
(= KNP / S; knock level) is calculated, and the process proceeds to step S305.

In step S305, the knock determination level PKN set in step S303 is compared with the knock level P2 calculated in step S304, and if P2 <PKN, the flow proceeds to step S306, where it is determined that no knock has occurred, and the flow proceeds to step S307. , I /
1 is output from the output port of O port 12 and step S312
Proceed to.

On the other hand, if P2 ≧ PKN in step S305, the process proceeds to step S308, where it is determined that knock has occurred.
In step 09, 0 is output from the output port of the I / O port 12, and in step S310, the knock level P2 calculated in step S304 is stored in a predetermined address of the RAM 9.

Next, the process proceeds to step S311 where the knock occurrence flag FLAG
Is set (FLAG ← 1). In step S312, the knock intensity integrated value KNP and the sampling number S in the knock detection section are set.
Is cleared, and the process returns to the main routine.

(Processing Procedure of Main Control Unit) Next, the knock data receiving procedure on the main control unit 1 side will be described with reference to the flowchart of FIG.

The flowchart of FIG. 5 is, for example, an interrupt routine started in synchronization with a BTDC 70 ° crank angle signal of the crank position sensor 2. In step S351, the output port of the I / O interface 12 of the knock detection unit 4 is Read the state.

Next, the process proceeds to step S352, where it is determined whether or not knock has occurred based on the value of the output port read in step S351. If the value of the output port is 1, that is, no knock has occurred, the interrupt is terminated. .

On the other hand, if it is determined in step S352 that the value of the output port is 0, that is, knock has occurred, the process proceeds from step S352 to step S353, requests the knock detection unit 4 to transmit knock data, and proceeds to step S354. move on.

In step S354, the data of knock level P2 is received from knock detection unit 4, and the interruption is terminated.

Then, the ignition timing is retarded based on the knock level P2 received from the knock detection unit 4 in the interrupt routine to avoid knocking.

In the above-mentioned interrupt routine, the control line 4a from the knock detection unit 4 may be connected to an interrupt terminal of the main control unit 1 so that the knock detection unit 4 can be used as an external interrupt.

The knock sensor 6 is not limited to a resonance-type sensor, and may detect not only a mechanical vibration of an engine transmitted to a cylinder block or the like, but also a vibration waveform such as a combustion pressure and a vibration sound. Good.

[Effects of the Invention] As described above, according to the present invention, the main control unit for controlling the engine is connected to the main control unit via the control line for transmitting the presence or absence of knock and the serial communication line for data exchange. Knock determination means for determining whether or not knock has occurred based on an analog / digital conversion value of a knock sensor output signal and a predetermined knock determination level; and the main control means determines the determination result of the knock determination means via the control line. Output to the main control unit, and a means for transmitting knock data to the main control unit via the serial communication line when the knock determination means determines that knock has occurred. On the other hand, the knock determination is performed via the above control line without increasing the load due to the knock detection processing. The result can be immediately incorporated into engine control, and high-speed knock control can be realized.

Moreover, since knock data is transmitted to the main control unit only when knock has occurred, the load on the main control unit can be reduced and the processing speed can be improved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is a functional block diagram of a knock detection unit, FIG. 2 is a circuit configuration diagram, FIG. 3 is a flowchart showing a main processing procedure in the knock detection unit, and FIG. FIG. 5 is a flowchart showing a knock detection procedure, FIG. 5 is a flowchart showing a processing procedure in the main control unit, and FIG. 6 is a timing chart of knock detection processing. 1 Main control unit 4a Control line 4b Serial communication line 6 Knock sensor 26 Knock determination means 27 Communication means PKN Knock determination level

Claims (1)

(57) [Claims] An analog / digital conversion value of a knock sensor output signal is connected to a main control unit for controlling an engine via a control line for transmitting the presence / absence of knock occurrence and a serial communication line for data exchange. Knock determination means for determining whether or not knock has occurred based on a predetermined knock determination level, and a knock determination means for outputting the determination result of the knock determination means to the main control unit via the control line, and further comprising the knock determination means And a communication means for transmitting knock data to the main control unit via the serial communication line when it is determined that knock has occurred.