JPS5828643A - Knocking detecting method for internal combustion engine - Google Patents

Abstract

PURPOSE:To simplify the hardware constitution and to increase the accuracy and reliability for the detection of knocking, by integrating the engine vibration detecting signals in the different prescribed ranges of crank angles with different time constants and then comparing the levels of said detecting signals. CONSTITUTION:An interruption is applied to the processing operation carried out by a microprocessor 62 via an interrupting circuit 40 and by the pulse output produced by the crank angle sensors 16 and 18 with each prescribed crank angle. Thus the integral value is fetched by a knocking sensor 12 for the prescribe period before and after the dead point of at least a cylinder which is obtained by an integral network 50 of the engine vibration detecting output. While the integral time constant of the network 50 is controlled by the processor 62 so that the period after the dead point is longer than the period before the dead point. The background signal in a period free from the knocking obtained by the sensor 12 has the good responding performance and high stability without any effect of noise, etc. Then the levels are compared with each other for the integral value between both periods. In such a way, the hardware constitution is simplified to ensure the detection of knocking 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, which detects mechanical vibrations that occur due to abnormal engine combustion, that is, knocking, as electrical amplitude fluctuations using a vibration detection element called a knock sensor, the amplitude of the electrical signal output from the knock sensor is used as a comparison standard. By comparing the values, it is possible to determine whether the detected vibration is actually caused by knocking. In this case, the comparison reference value is not fixed at a constant value, but is changed according to the output signal (hereinafter referred to as pack ground signal) that is considered to be unrelated to the knocking of the knock sensor and na. It becomes possible to compensate for sensor variations, changes over time, and the like.

In internal combustion engines that use a micro combinator to perform software processing to perform control after knocking is detected, such as retarding the ignition timing, it is better to perform knocking detection as described above using software, which reduces the amount of metal. However, if the knocking signal is to be taken in by the microcombiator, it is necessary to configure the input circuit to respond as faithfully as possible to changes in the output of the knock sensor so as to detect even minute knocking. Also/4
．． When a pack ground signal is used, it is necessary to stabilize the pack ground signal by configuring an input circuit that does not have very good response to changes in the output of the knock sensor. In order to satisfy both of these requirements, it is necessary to provide input circuits in separate systems, which inconveniences that the amount of hardware increases accordingly.

The inventors of the present invention have arrived at the present invention as a result of intensive research and efforts to address the above-mentioned problems in the case of attempting to detect knocking using a V microcombi system.

That is, an object of the present invention is to provide a knocking detection method that has a simple hardware configuration and can improve knocking detection accuracy and reliability.

A feature of the present invention that accomplishes the above-mentioned object is that at least one vibration detection element that converts mechanical vibrations into amplitude fluctuations of an electric signal is mounted on the engine body, and the top dead center of at least one cylinder determined in advance is The integral value of the amplitude of the electric signal from the vibration detection element in the previous first predetermined crank angle range is stored, and the integrated value of the amplitude of the electric signal from the vibration detection element in the first predetermined crank angle range is stored, A method for detecting the presence or absence of knocking by comparing the magnitude of an integral value of the amplitude of an electric signal with the stored value, wherein the time constant of the integral with respect to the first crank angle range is set to the second crank angle range. The reason is that it is made larger than the time constant of the integral over the angular range.

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 same figure, 1o is the engine cylinder fcI
, 12 is a cylinder holder attached to the cylinder holder 10 . The knock sensor 12 is a well-known device that is composed of, for example, a piezoelectric element or an electric element, and converts mechanical vibrations into electrical amplitude fluctuations. In FIG. 1, the reference numeral 14 further indicates a distributor, and the crank angle sensor 14 is connected to the distributor 14.
6 and 18 are provided. The crank angle sensor 16 is used for cylinder discrimination, and if this engine has 6 cylinders, then every rotation of the distributor shaft, that is, every 2 rotations of the crankshaft (every 720'CA), one K. Generates a pulse. The occurrence position is set, for example, to the top dead center of the first cylinder. The crank angle sensor 18 generates 24 7-medium russes for each revolution of the distributor shaft, and thus generates 1-1 russ for every crank angle 301.

Noksen? 12, electrical signals from crank angle sensors 16 and 18 are sent to a control circuit 20. Control times
A signal representative of the lug intake air flow rate is also sent to 120 from an air flow sensor 24 provided in the intake passage 22 of the engine. On the other hand, the control circuit j620 outputs an ignition signal to the igniter 26, and the snow current generated by the igniter 26 is transmitted to the distributor 14.
Ignition of each cylinder through! lugs 28.

The engine is usually provided with various other sensors for detecting the operating condition parameters, and the control circuit 20 also includes:
The fuel injection valve 30 and the like are also controlled, but since these are not directly related to the present invention, they will be omitted in the following explanation.

FIG. 2 is a block diagram showing a configuration example of the control circuit 2o in FIG. 1. The voltage signal from the air flow sensor 24 is sent to the analog multiplexer 32 via the buffer 3o.
The signal is sent to the micro combiator, selected according to the instruction from the micro combinator, and applied to the wheat converter 34, where it is converted into two communication signals. be included.

The pulse signal for each crank angle of 72 degrees from the crank angle sensor 16 is applied to the interrupt request signal forming circuit 40 via the torque buffer 38. On the other hand, the pulses at every crank angle 30@ from crank angle cent t18 are applied to the interrupt request signal forming circuit 40 and the speed signal forming circuit 44 via the buffer 42. The interrupt request signal forming circuit 40 includes:
From 14 Lus each for every 720° and 30″ of crank angle,
Forms various interrupt request signals. These interrupt request signals are applied to the microcombination unit via the input/output IC 46. The speed signal forming circuit 44 has a crank angle of 3
A binary signal representing the rotational speed of the engine N@ is formed from the period of the Norms for each 0 @. The formed rotational speed signal M is sent to the microcomputer via the input/output/-).

The output signal of the knock sensor 12 includes a buffer for impedance conversion and a frequency band (7 to 8) on the knocking side.
kHz) is fed into an integrating circuit 50 via a circuit 48 consisting of a band pulse filter with a pass band.

The integrating circuit 50 performs an operation of integrating the output signal from the knock sensor 12 only when the ``''ll level is applied from the micro combiator via the line 52 and the input/output/-) 46. Further, the integrator [50 has an integration time constant that changes in response to a 1-bit time constant control signal of "1" 910Im applied to the micro combinatorial color via the line 53 and the input/output port 46. It is configured.

Assuming that the integrator circuit 5o is a general integrator using an operational amplifier, if it is configured to switch and control its resistance value according to the logic of the time constant control signal given via the line 53, the above-mentioned results can be achieved. It is possible to perform variable control of the time constant. For example, if the input resistance is two resistors connected in series and one of the resistors is configured to be short-circuited when the time constant control signal is @l'', then when the time constant control signal is ``0'', the integral time constant becomes large, and becomes small when @l''. The output of the integrator circuit 50 is converted into a binary signal by a converter 54 and sent to the microcombi controller via a human output port 46. However, the start of ν heavy mass exchange in the wheat exchanger 54 is performed by a heavy mass exchange start signal applied from the microcombinator 1 through the human output 4-461Q156. Further, when the ν weight conversion is completed, the ~1 converter 54 notifies the microcombi tool KA/1) conversion completion 1 via the line 58 and the input/output 4-46.

On the other hand, when an ignition signal is output to the drive circuit 60 via the micro combinator and the turnout IC 46, this is converted into a drive signal to energize the igniter 26, and the duration of the ignition signal and Ignition control is performed according to the duration.

The micro combination device includes the aforementioned input/output ports 36 and 46, a micro combination unit (MPU) 62, a random access memory (RAM) 64, a read only memory (ROM) 66, a clock generation circuit (not shown), and a memory control. It mainly consists of circuits and paths 68 connecting these circuits, and executes various processes according to a control program stored in the ROM 66.

3 to 8 are flowcharts showing only the parts particularly related to the present invention among the control contents. According to the processing routines shown in FIGS. 3 to 6, the signal from the knock sensor 12 does not include any mechanical vibration noise such as king or pulso knocking sounds, but only contains the basic vibration of the engine. Integration of the knock sensor output is performed during a stable period (pack ground signal detection period), and its final value is taken in as a binary signal. However, this /l
The integration time constant during the ground signal detection period is set to a relatively large value. The pack ground signal detection period is preferably 30° CA - BTDC ~ 1 in each compression machine or a predetermined specific cylinder.
0"CA - B'rDC. According to the processing routines shown in FIGS. 6 to 8, during the period in which the signal from the knock sensor 12 should include a knocking signal (knocking detection period), Integration of sensor output is performed.
Its final value is captured as a binary signal. However, the integration time constant during the king detection period is set to a smaller value than the time constant during the pack ground signal detection period. According to the processing routines shown in FIGS. 6 to 8, the third
The binary signals captured in the processing routines shown in Figures to Figure 6,
A comparison is made with the binary signal taken in by this processing routine, and it is determined whether or not a king has occurred. The knocking detection period is preferably 10@CA during the explosion stroke of each cylinder or a predetermined specific cylinder.
・Selected near TDC ~ 50°C ・ATDC.

The contents of the processing routines shown in FIGS. 3 to 8 will be explained in detail below.

From the interrupt request signal forming circuit 40, a position at a predetermined crank angle 0·CA before the compression top dead center of each cylinder or a predetermined specific cylinder, for example, 60°CA-BT
When a predetermined interrupt request signal is applied to the DC, the MPU
62 executes the interrupt processing routine shown in FIG. That is,
In step 70, time t1 at which the 74 ground detection period begins is calculated. This time ti is the time of a timer on the software, and is the crank angle position at which the pack ground detection period starts (for example, 30@CA-BTD
C), current crank angle position (0・CA -BTDC
): It is clear that the KJI can be easily obtained if the current time t. of the timer and the engine rotational speed N. are known.

When the processing in step 70 is completed, the process proceeds to step 71, where the time constant control flag FTct-0'' is reset.

As a result, a time constant control signal of 10'' is sent to the integration circuit 50 via the line 53, and the integration time constant is set to the larger value TCI.

When the processing of STE and GUAR1 is completed, the third interrupt processing is completed and GLODARAM 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 72,
The integrating circuit 5o is caused to start integrating the output of the knock sensor 12. This is transmitted to the integrator circuit 50 via line 52.
This is accomplished by sending an integration instruction signal of "1" level. Note that in this case, the calculation and integration where IPTc=Q are performed using the larger time constant TC. Next, in step 73, the time 1 when the paddle and ground detection period ends is determined. Calculate. Crank angle position at which pack ground detection period ends (e.g. 10'CA - BTDC)
is predetermined, the calculation method for this Stella 173 is the same as that for Step 70. Then,
In step f74, the wheat exchanger 54 is instructed to start heavy exchange, and then the main routine is returned.

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 75, the integrating operation of the integrating circuit 50 is terminated. This is accomplished by inverting the integration indication signal to 102. Next, at the start of the knocking detection period in step 6, I
Calculate Q t s. The crank angle position at which the knocking detection period starts (for example, 10@Cm.mu.TDC) is predetermined, and therefore the calculation method for this step 76 is almost the same as that for step 70. Next, in step 77, the time constant control flag 'TC is set to @1''.
Set to . From this K, a time constant control signal of "11" is sent to the integration circuit 50 via the line 53, and the integration time constant is set to the smaller value T01(TCs)TCs).Then, Glodarum executes the main routine. to return to.

The ν heavy mass exchange by the ν wheat exchanger 54 is completed, and the k heavy mass exchange is completed.
When a completed interrupt request signal is applied via line 58, MPU 62 executes the interrupt processing routine of FIG. First, at Step 8, the output of the integrating circuit 50 is converted into the current value by 1, and the previous width conversion value is converted by 1.
Compare with and move on to the next step.

For Guar 9 and 80, substitute the large weight conversion value for X. Next, in step 81, it is determined whether the integration operation is currently being performed for the /4 ground detection period or for the knocking detection period. In the former case, in Stella f82, the current contents of X are moved to b and stored in RAM 64. In the latter case, in step 83, the contents of X at that time are moved to a and stored in the RAM 64. In the next step 84, it is determined whether or not the integral operation is currently in progress. If the integral operation is in progress, the process proceeds to step 85 and the heavy exchange is started again. In this manner, in this embodiment, the heavy mass exchange is repeated a plurality of times during one integral operation period, and the maximum value thereof is detected.

On the other hand, 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. First, in step 86, the integration instruction signal is inverted @1'K to start the integration operation. In addition, in this case, since 'tc' is 1,
Integration is done using the smaller time constant Tc. Next, in step 87, the time t4tll at which the knocking detection period ends is output. The crank angle position at which the knocking detection period ends (for example, 50° CA・muTDC) is predetermined, so this stay f 8
The calculation method of '7 is almost the same as that of step 70. Next, Ste! At step 88, the heavy mass exchange is started, and after that, the main routine is returned to.

When the soft timer reaches time t4, a time interrupt request is generated, which causes the MPU 52 to execute the interrupt processing routine shown in FIG. First, in step 89, the integration instruction signal is inverted to "O"K, and the integration operation is completed. Next, the process proceeds to step 9o, and the maximum value of the integral value detected during the knocking detection period, in other words, the value corresponding to the maximum amplitude of the knock sensor 12 during this period, is determined during the knocking detection period. The maximum value of the detected integral value, i.e.
Based on the value a corresponding to the maximum amplitude of the knock sensor 12 during this period and the constant, it is determined whether or not a≧−b. If Hatake≧-b, knocking occurs, a<k-b
In this case, it is recognized that no knocking has occurred.If knocking has occurred, the process proceeds to step 91, where the ignition timing advance correction value 0 is decreased by Δ0 and the ignition timing is retarded. That is, the calculation θ'←0−Δ0 is performed.

The optimum ignition timing is calculated by a well-known method from the intake air flow rate 91 detected by the air flow sensor 24 and the rotation speed Ha obtained from the rotation speed signal forming circuit 44. Then, the calculated ignition timing is corrected by the advance angle correction value θ. In Step 91, the advance angle correction value -
The aim is to reduce the ignition timing by Δ0, thereby delaying the ignition timing by Δ0, thereby suppressing knocking.

Figures 9a and 9b are diagrams illustrating the operation of the nine embodiments described above), and in both figures, ■ is the pressure inside the combustion chamber (
(shiatsu), φ) are the output signal waveforms of the knock sensor 12, (0 is the integral instruction signal waveform, and (b) is the output value of the integrating circuit 5o.Furthermore, in both figures, Ts is
9, which indicates the Fugland detection period, and this period T t
is set to a period in which the output signal from the knock sensor 12 is stable, with only the basic vibration of the engine, in which noise e81 such as pulp knocking noise and knocking B are not usually included. t, TI
is a knocking detection period, and this period T is set as a period during which knocking B should occur after the cylinder is ignited.

When the integration time constant of the integration circuit 50 is constant (however,
(When the time constant is fixed to a relatively small value to detect knocking), as shown in Fig. 9a, the output of the xenona 120 is stable without any dizzy noise during the pack ground signal detection period Ti. There is no problem in some cases, but 9b
As shown in the figure, if noise 8s occurs during the period T@ for some reason, the output of the integrating circuit 50 changes in response to this noise 8m, as shown by the broken line in the figure (b). , the output becomes unstable. As a result, the accuracy and reliability of knocking detection are significantly reduced. However, according to the method of the present invention, the pack ground signal detection period T
Since the integral time constant TC during I is sufficiently larger than the integral time constant C3 during the knocking detection period T3,
As shown by the solid line in Figure b, the pack ground signal is stabilized.

does not respond very sharply to changes in the output of the sensor 12.
Therefore, according to the present invention, even minute knocking can be accurately detected with good response, and the back ground signal is stable despite being affected by noise. As a result, special conveniences such as a simplified hardware configuration and significantly improved knocking detection accuracy and reliability can be obtained.

[Brief explanation of the drawing]

Figure WX1 is an overall schematic configuration diagram of one embodiment of the present invention.
The figure is a block diagram of the control circuit in Figure 1, and Figures 3 to 8 are flowcharts of each side processing routine of the control circuit.
FIGS. 9a and 9b are diagrams for explaining the effects of the above embodiment. 10... Cylinder lock, 12... Knock sensor, 14... Distributor, 16.18... Crank angle sensor, 20... Control circuit, 36.41...
Input/output port, 48...Further and filter circuit, integration circuit, 54...k heavy exchanger, 62...MPU
,64...R Ayu166...ROM. Patent Applicant: Toyota Motor Corporation, Patent Application Agent, Patent Attorney, Akira Aomizu, Patent Attorney, Kazuyuki Nishidate, Patent Attorney, Akira Yamaguchi Figure 3 Figure 5 Figure 6 Figure 7 Figure 9a Figure 9b

Claims (1)

[Claims] 1. 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 a first predetermined crank angle range Kj? before the top dead center of at least one cylinder is determined in advance. The integral value of the amplitude of the electric signal from the vibration detection element is stored, and the integral value of the amplitude of the electric signal in a second predetermined crank angle range after ignition of at least one predetermined cylinder and the A method for detecting the presence or absence of knocking by comparing the magnitude with a stored value, the method comprising: a time constant of integration regarding the first crank angle range being made equal to a time constant of integration regarding the second crank angle range; A method for detecting knocking in an internal combustion engine, characterized by increasing the size of the engine.゛