JPS5828641A - Knocking detecting method for internal combustion engine - Google Patents

Abstract

PURPOSE:To realize the detection of knocking with high accuracy and high reliability, by calculating the reference value of comparison in accordance with the minimum value of the detected vibrating amplitude of an engine during the prescribed cycle of ignition and as a result increasing responding performance in a transient operation mode. CONSTITUTION:The minimum value detecting circuit 51 holds the minimum value of the vibrating amplitude during the prescribed cycle of ignition which is given by a knocking sensor 12 that is reset at each working cycle of an engine as the background signal and via a microprocessor 62, an I/O46, etc. This background signal is turned into a highly responsive signal which is not affected by the noise and has the high follow-up performance in a transient operation mode. Thus the value of comparison is calculated in accordance with the holding value of the circuit 51 and via an MPV62 and then compared with the value of the engine vibrating amplitude of the maximum value detecting circuit 50 within a prescribed range of crank angle. In such a way, the detection of knocking is possible with high accuracy and high reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting whether or not knocking occurs in an internal combustion engine.

In the knocking detection method, the mechanical vibrations that occur due to abnormal engine combustion, that is, knocking, are detected as electrical amplitude fluctuations using a vibration detection element called a knock sensor. By comparing the vibration with a reference value, it is determined whether the detected vibration is actually caused by knocking or not. In this case, without fixing the comparison reference value to a constant value, by changing the comparison reference value according to an output signal that is considered to be unrelated to knocking of the knock sensor (hereinafter referred to as pack ground signal), it is possible to eliminate the variation in the knock sensor. It becomes possible to compensate for changes over time. Conventionally, the pack ground signal was obtained by applying the output signal of the knock sensor to an integrating circuit with a large time constant and constantly integrating this signal. The output signal of the knock sensor is constantly compared with the pack ground signal in a comparator. The output of this comparator becomes a signal indicating the presence or absence of knocking.

However, when the back ground signal is obtained by the method described above, although the background signal value is certainly stabilized, it does not respond well to changes in the engine operating condition, so knocking may be detected incorrectly. This may lead to judgment.

As another technique for obtaining a pack ground signal, the applicant detects the output of a knock sensor in a crank angle range that is considered not to include noise such as pulp knocking noise, and uses this detected value as a pack ground signal. We have already proposed a method to do so. However, this type of method has a problem in that it imposes a large burden on the microcomputer in order to define the specific crank angle range.

Therefore, the present invention is intended to solve the above-mentioned technical problems, and an object of the present invention is to stabilize the engine when it is in a steady operating state and to improve responsiveness when the engine is in a transient operating state. It is an object of the present invention to provide a novel method in which a pack ground signal that changes according to the tracking is obtained, thereby enabling highly accurate and reliable knocking detection, and which requires less burden on a microcomputer. .

A feature of the present invention that achieves the above-mentioned object is that at least one vibration detection element that converts mechanical vibration into an amplitude fluctuation of an electric signal is mounted on the engine body, and knocking is detected in response to the electric signal from the vibration detection element. In the method of detecting the presence or absence of occurrence, the minimum amplitude value of the Tsumugi electrical signal during a predetermined number of ignition cycles is detected, a comparison reference value is calculated according to the detected minimum amplitude value, and the calculated comparison reference value is The purpose is to detect whether or not knocking has occurred by comparing the amplitude value of the electric signal in a predetermined crank angle range after ignition of at least one cylinder determined in advance.

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

FIG. 1 schematically shows the overall configuration of an embodiment of the present invention. In the figure, 10 is a cylinder block of the engine, 12 is a cylinder block, and a knock sensor is attached to the cylinder block 10. The knock sensor 12 is a well-known device that is composed of, for example, a piezoelectric element or an electromagnetic element, and converts mechanical vibrations into electrical amplitude fluctuations. In FIG. 1, 14 further indicates a distributor; 9;
This distributor 14 has a crank angle sensor 16.
and 18 are provided. The crank angle sensor 16 is
It is for cylinder discrimination, and if this engine is a 6-cylinder engine,
Every time the distributor shaft makes one revolution, that is, every two revolutions of the crankshaft (every 720° CA), one yakurus is generated. The position where this occurs is set, for example, at the top dead center of the first cylinder.

The crank angle sensor 18 generates 24 pulses for each rotation of the distributor shaft, ie, a pulse for every 30 degrees of crank angle.

Electric signals from knock sensor 12 and crank angle sensors 16 and 18 are sent to control circuit 20. The control circuit 20 is further fed with a signal representing a large intake air flow rate from an air sensor 24 provided in the intake passage 22 of the engine. On the other hand, the control circuit 20 outputs an ignition signal to the igniter 26,
Snow 9-ri electric flL formed by the igniter 26
The spark is then distributed to the spark plugs 28 of each cylinder via the distributor 14.

The engine is normally provided with various other sensors that detect the operating state 74' parameters, and the control circuit 20 also controls the fuel injection valve 30, etc., but these are not directly related to the present invention. Therefore, all of these will be omitted in the following explanation.

FIG. 2 is a schematic diagram showing an example of the configuration of the control circuit 20 shown in FIG. The voltage signal from the air 70-sensor 24 is passed through a buffer 30 to an analog multiplexer 32.
The signal is sent to the microcomputer, which is selected according to instructions from the user, and applied to the converter 34, where it is converted into two communication signals, and then input into the microcomputer via the input/output port 36. It will be done.

A pulse of every 720 degrees of crank angle from the crank angle sensor 16 is applied to the interrupt request signal forming circuit 40 via the buffer 38. On the other hand, Noculus signals for every 30 degrees of crank angle from the crank angle sensor 18 are applied to an interrupt request signal forming circuit 40 and a speed signal forming circuit 44 via a buffer 42 . The interrupt request signal forming circuit 40 forms various interrupt request signals from each A/rus at every 720° and every 30° crank angle. These interrupt request signals are applied to the microcomputer via the input/output port 46. The speed signal forming circuit 44 has a crank angle of 30°.
2 represents the engine rotational speed N from the period of each noise.
Form an evolutionary issue. The formed rotational speed signal is sent to the microcomputer via the input/output (/-)4e.

The output signal of the knock sensor 12 is transmitted through a buffer for impedance conversion and a frequency band (7 to 8) unique to knocking.
kHz) is sent to a rectifier circuit 48 via a circuit 47 consisting of a bandpass filter having a pass band. The signal from the knock sensor 12 is subjected to half-wave rectification or full-wave rectification by the rectifier circuit 48. The rectified signal is sent to an integrating circuit 49 and smoothed. Therefore, the output of the integrating circuit 49 represents the envelope of the output signal of the knock sensor 12. In other words, the signal has a voltage value corresponding to the amplitude of the output signal of the knock sensor 12. The output signal of the integrating circuit 49 is sent to a maximum value detection circuit 50 and a minimum value detection circuit 51, and the maximum value and minimum value of its amplitude are detected, respectively. However, the minimum value detection circuit 5o
The detected maximum value is cleared by the first reset signal sent from the microcomputer via the line 50m and the input/output port 46. For example, the first reset signal of 120°
If the maximum value detection circuit 5o is output once per CA (in the case of six cylinders), the maximum value detection circuit 5o will detect a new maximum value for each ignition cycle. Further, the minimum value detection circuit 51
i! 51m and the second reset signal sent from the microcomputer via the input/output port 46,
The detected minimum value is cleared. The second reset signal is e.g.
If the minimum value is output once every ), the minimum value detection circuit 51 will detect a new minimum value every operation cycle. The outputs of the maximum value detection circuit 50 and the minimum value detection circuit 51 are sent to an analog multiplexer 52, and these outputs are sent to an analog multiplexer 52 in response to a selection instruction signal sent from a microcomputer via a line 53 and an input/output/-) 46. Either one is selected and applied to the ~Φ converter 54. A/D converter 5
4 converts the input maximum value signal or minimum value signal into a binary code. The start of Φ conversion of the A/D converter 54 is performed by a Φ conversion start signal applied from the microcomputer via the input/output (/-) 46 and line 56't-. 't7't, ~When the Φ conversion is completed, ~heavy exchanger 5
4 notifies the microcombi via the 1158 and the input/output port 46 that the Φ conversion has been completed. On the other hand, an ignition signal is output from the microcomputer to the drive circuit 60 via the input/output port 46. Then, this is converted into a drive signal to energize the igniter 26, and ignition control is performed according to the duration and duration of the ignition signal.

Microcombi, the above-mentioned input/output ports 36 and 4
6, a microcombi processor (MPU) 62, a random access memory (RAM) 64, a read-only memory (ROM) 66, a clock generation circuit (not shown),
It is composed of a memory control circuit, a path 68 connecting these circuits, etc., and executes various processing pipes according to control programs stored in the R6M66.

3 to 6 are flowcharts showing only the parts particularly related to the present invention among the control contents. According to these processing routines, the signal from the maximum value detection circuit 50 is detected during a period in which only a knocking signal is mainly included in the signal from the knock sensor 12 when knocking occurs (), king detection period). During other periods, the signal from the minimum value detection circuit 51 is taken in. A comparison reference value is calculated according to the signal from the minimum value detection circuit 51, and the presence or absence of knocking is determined by comparing the signal value from the maximum value detection circuit 50 with this comparison reference value. The above-mentioned king detection period is preferably from 10° CA・BTDC to 50° CA・BTDC during the compression and explosion strokes of each cylinder or a predetermined specific cylinder.
Selected near CA-ATDC.

The contents of the processing routines shown in FIGS. 3 to 6 will be explained in detail below.

The interrupt request signal forming circuit 40 outputs a predetermined crank angle θ from the compression top dead center of each cylinder or a predetermined specific cylinder. CA mid-front position, e.g. 30° CA-BTDC
When a predetermined interrupt request signal is applied, the MPU 62 executes the interrupt processing routine shown in FIG. That is, Ste.
At differential 0, time t1 when the knocking detection period starts
Calculate. This time t1 is the time of a timer on the footwear, including the crank angle position at which the knocking detection period starts (for example, 10'CA-BTDC), the current crank angle position (θ.CA-BTDC), and the timer's current time. It is clear that it can be easily calculated if the time to% and the engine rotational speed N are known. When the process of step 70 is completed, this interrupt routine ends and the program returns to the main routine.

When the time of the soft timer reaches tl, a time interrupt request is generated, which causes the MPU 62 to execute the interrupt processing routine shown in FIG. First, in step 71, selection flag F1. to @1”.

This causes the analog multiplexer 5 to
A predetermined selection instruction signal is sent to 2, the multiplexer selects the channel on the maximum value detection circuit 50 side, and the maximum value signal is sent to the small changer 54. Calculate the time t3 at which the time t3 ends. Crank angle position at which the knocking detection period ends (
For example, 50° CA-ATDC) is determined in advance, so the calculation method in step 72 is
The same is true for . When the processing in step 72 is completed, the program returns to the main routine.

Microcombi, -Yuha~ I against Koken Exchange 54! 5
When the converter 54 completes the conversion of the signal given from the analog multiplexer 52, an interrupt request signal of 1158 is issued. is applied to the microcomputer via. The MPU 62 executes the interrupt processing routine shown in FIG. 5 in response to this interrupt request. First, in step f73, it is determined whether or not the selection flag /F, is 10''.If F, .=00, that is, as will be described later, the 1 analog multiplexer 52 is connected to the minimum value detection circuit 51 side. If a channel has been selected, the process proceeds to step 74, and the ~Φ conversion value Dad is stored as b in a predetermined position in the RAM 64.

If F@@ is 0, that is, if the analog multiplexer 52 selects the channel on the maximum value detection circuit 50 side, the process proceeds to step 75, and ~Φ conversion memory Dad
It is stored in a predetermined location in the RAM 640 as ta. The above values correspond to the Nonotsu ground signal,
Further, the value a is the value of the knock sensor 12 during the knock detection period.
This value corresponds to the maximum value of the output amplitude of .

The soft timer time is 1. Then, a time interrupt request is generated, which causes the MPU 62 to execute the interrupt processing routine shown in FIG. At step 76, the selection flag F is set. Reset @0# trap. As a result, 7%
A predetermined selection instruction signal is sent to the analog multiplexer 52 via 1153, and the multiplexer selects the channel on the minimum value detection port $51 side. Therefore, in this case, the maximum lJ1 signal is sent to the ~Φ converter 54.Next, in step 77, a reset signal is sent to the maximum value detection circuit 50 via the line 50ai, and the maximum value held until then is reset. Clear 0 Next, the program proceeds to step and differential 8, and multiplies the value corresponding to the maximum value of the output amplitude of the knock sensor 12 during the knocking detection period and the value corresponding to the tag ground signal by a constant. to the value −
A determination is made as to whether it is large or small with a comparison reference value consisting of b.

If the bell ≧ -b, knocking will occur (A'), *<k-b
In this case, it is determined that knocking has not occurred. If knocking has occurred, the process proceeds to step 79, where the advance angle correction value θ used in the ignition timing calculation processing routine is decreased by Δ0 to perform retard angle control, that is, the calculation θ′←0−Δ0 is performed.
The above-mentioned ignition timing calculation processing routine assumes that there is no knocking using a well-known method based on the intake air flow rate Q1 detected by the air flow sensor 24&C and the /4 rammeter of the rotational speed N0 etc. obtained by the rotational speed signal forming circuit 44. The optimum ignition timing for each case is calculated, and this Minode value is corrected by an advance angle correction value θ. In the steering and differential 9, such advance angle correction value 0 is decreased by Δθ, and as a result,
The ignition timing in the next ignition cycle is delayed by Δθ. As a result, knocking is suppressed.

The minimum value detection circuit 51 is connected via a line 511 once per engine operation cycle, that is, at a crank angle of 720°.
Once every cycle, a reset signal is sent at a predetermined crank angle position, which clears the previously held minimum value.

FIG. 7 is a diagram for explaining the operation of the above-mentioned embodiment, in which the output signal waveform of the knock sensor 12 is shown, and the waveform obtained by rectifying and smoothing the output signal waveform is obtained from the integrating circuit 49. The signal waveform, (C) represents the logic of the selection flag Fse corresponding to the selection instruction signal sent to the analog multiplexer 52, and (2) represents the signal waveform sent to the A/D converter 54, respectively. In the same figure, T
I indicates the knocking detection period, and τ indicates the pack ground detection period, respectively. The knocking detection period T1 is
As shown in (2), the period is set such that the output of the knock sensor 12 does not include the noise 8□ of pulp striking, but includes knocking 81. And no.

During the king detection period T1, the value 1 corresponding to the maximum value of the output amplitude of the knock sensor 12 is taken into the combination, and during the packing period and the de detection period T3, the value 1 corresponding to the maximum value of the output amplitude of the knock sensor 12 is taken in.
The value corresponding to the minimum value of the output amplitude is taken into the combination, -.

FIG. 8 is a diagram for explaining the effects of the present invention.
The vertical axis represents the rectified and smoothed amplitude waveform of the output of the knock sensor 12, and the horizontal axis represents the crank angle. In the figure, a broken line shows an amplitude waveform in a certain operating cycle of the engine, and a solid line shows an amplitude waveform in another operating cycle of the engine.

As is clear from the figure, the minimum value of the amplitude of the knock sensor output is a nearly constant value in each operating cycle when the engine is in a steady state. Therefore, this minimum amplitude value can be used as the pack ground signal. For example, it is possible to obtain a very stable pack ground signal.In addition, by taking the minimum amplitude value, noise such as pulse hitting noise is completely ignored, so it is possible to obtain a pack ground signal within a specific crank angle range. There is no need to pay extra for detection, which reduces the burden on the operator. Furthermore, it is completely free from the effects of fluctuations and noise that are inevitably included even when a pack ground signal is detected within a specific crank angle range. Moreover, this minimum amplitude value has the characteristic that it changes according to the transient change even when the operating state of the engine becomes a transient state, so the pack ground value changes with good response even in such cases. It becomes possible to obtain a signal.

As explained in detail above, according to the method of the present invention, when the engine is in the steady operating state WAK, it is stabilized, and when the engine is in the transient operating state M
If there is K, a pack ground signal that changes with good responsiveness can be obtained. Therefore, highly accurate and reliable knocking detection can be performed. Further, the convenience of reducing the burden on the microcomputer can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the control circuit shown in FIG. 1, and FIGS. 3 to 6 are flowcharts of each side processing routine of the control circuit. FIG. 7 is a diagram for explaining the operation of the above embodiment, and FIG. 8 is a diagram for explaining the effects of the present invention. 10... Cylinder pro, ri, 12... Knock sensor, 14... De(stribi, -ta, 16.18... Crank angle sensor, 20... Control circuit, 32.52...
・Multiple brefsa, 36.46-...input/output/-), 4
7...P, 7A and filter circuit, 48-...Rectifier circuit, 49-...Integrator circuit, 50...Maximum value detection circuit,
51... Minimum value detection circuit, 54... K1 converter, 6
2...MPU. 64...RA, 66...ROM. Patent applicant Toyota Motor Corporation Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Akira Yamaguchi. 3□ ″ 6 Figure 5

Claims (1)

[Claims] 1. A method in which at least one vibration detection element that converts mechanical vibrations into amplitude fluctuations of an electrical signal is mounted on the engine body, and the presence or absence of a king occurrence is detected in accordance with the electrical signal from the vibration detection element, The minimum amplitude value of the electric signal during a predetermined number of ignition cycles is detected, a comparison reference value is calculated according to the detected minimum amplitude value, and the comparison reference value and the predetermined comparison reference value of at least one cylinder are compared. A method for detecting knocking in an internal combustion engine, characterized in that the presence or absence of knocking is detected by comparing the magnitude of the electric signal with the amplitude value in a predetermined crank angle range after ignition.