JPS6142209B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention compares vibrations propagating through an internal combustion engine with a knocking determination level set from the vibration output, and detects the knocking intensity based on, for example, the number of times the former exceeds the latter. The present invention relates to a knocking control device for an internal combustion engine that retards the ignition timing in response to this intensity. [Conventional technology] Generally, in order to efficiently extract the output of an internal combustion engine, the ignition timing is set at the ignition timing that can generate the maximum torque (MBT: Minimum spark advance).
It is desirable to control the angle so that it advances up to (for Best Torque). However, it is known that engine knocking occurs if the ignition timing is advanced too far, and the ignition timing at the knocking limit that causes this knocking exists on the lag side of MBT depending on the engine condition, and if the ignition timing is advanced to MBT, There are also areas where knocking occurs. Moreover, this knocking limit ignition timing changes depending on the engine condition, the octane number of the fuel used, and the presence or absence of deposits in the combustion chamber, so the actual ignition timing
The engine is forced to advance to a point considerably behind the MBT, which poses the problem of not being able to extract sufficient torque from the engine. Therefore, in order to solve this kind of problem, for example, as shown in Japanese Patent Application Laid-Open No. 52-87537 (Ignition Spark Timing Method and Device for Internal Combustion Engines), knocking vibrations occurring in the engine are detected using a knocking detector. Based on the output of this detector, high and low starting values for knocking judgment, that is, knocking judgment levels are set, and the number of times the detection signal of the knocking detector exceeds these starting values is determined in advance. A method has been proposed in which when the number exceeds a reference number, it is determined that there is knocking and the ignition timing is controlled. [Problems to be Solved by the Invention] In this method, the reference numbers are determined to be, for example, 3 for the low level start value and 1 for the high level start value, and if either start value exceeds the reference number, knocking occurs. In this case, the ignition timing is retarded by a certain value. Therefore, when extremely large knocking occurs, which is likely to occur when the engine is rapidly accelerating, for example, it takes a certain amount of time until the angle is sufficiently retarded, and the knocking does not disappear easily. In order to avoid this problem, if the amount of retardation per time is set to an appropriate amount for large knocking, the retardation amount will be too much in the case of slight knocking, resulting in a decrease in output and worsening of fuel efficiency. I will invite you. Therefore, in view of these problems, the present invention has been made to
The purpose of this invention is to accurately discriminate between high, medium, low, etc. knocking intensities, and to quickly control the ignition timing to always be optimal for any of these. [Means for Solving the Problems] Therefore, the present invention provides a vibration detector that detects vibrations propagating through an internal combustion engine, and sets a determination level for knocking determination based on the vibration output detected by the vibration detector. A judgment level setting means compares the judgment level from the judgment level setting means and the vibration output from the vibration detector, and determines the ratio between the vibration output from the vibration detector and the judgment level from the judgment level setting means. a comparison means that generates an output each time it exceeds a predetermined value; the number of outputs generated by this comparison means is counted for each predetermined crank angle range at each ignition of the internal combustion engine; The present invention is characterized by comprising a number classification means for generating a knocking detection output for the knocking occurrence intensity by discriminating based on a set value, and a control means for retarding the ignition timing by an amount corresponding to the knocking detection output of the number classification means. The present invention provides a knocking control device for an internal combustion engine. [Function] In the present invention, a vibration detector is attached to the engine block of an internal combustion engine to detect vibrations synchronized with each combustion. The damping of vibrations propagating through an engine block consisting of a pair of rigid bodies is small, and the vibrations corresponding to combustion between cylinders are qualitatively the same. Furthermore, when knocking occurs, large vibrations with high frequencies are obtained due to the knocking. The frequency F (Hz) during knocking with respect to the knocking strength is given by F (Hz) = C/2d (1) C: Sound velocity in combustion chamber gas d: Combustion chamber bore diameter, and the vibration frequency is Not related to knotting strength. On the other hand, as the knocking intensity increases, the vibration intensity increases, and the output of the vibration detector also increases proportionally. In the present invention, the comparison means obtains a number of pulse signals corresponding to the knocking intensity, the counted value of this signal is discriminated based on a set value to determine the knocking intensity, and the ignition timing is adjusted according to this discrimination result. The amount of retardation is determined, and the ignition timing can be quickly controlled to the optimum value for each knocking strength. [Example] First, Fig. 1 compares the pressure (P) in the combustion chamber and the corresponding vibration (G) depending on the presence or absence of knocking and its strength at the same engine speed.
If we focus on vibration (G) from the example in Fig. 1, the difference up to compression top dead center (TDC) is small depending on the presence or absence of knocking and its strength. Therefore, for example, the average value of vibration output from ignition (IG) to top dead center (TDC) (vibration average value before top dead center) is approximately constant. From this, for example, when the vibration (G) corresponding to knocking exceeds the value obtained by multiplying the average value of vibrations before top dead center by a constant for each combustion (hereinafter referred to as the average value of vibrations before top dead center), knocking is determined. If the engine condition changes and the overall vibration level changes,
Since the average vibration value before top dead center and the vibration corresponding to knocking also change, knocking can be easily compared and judged. Based on the above, in the example described below, the vibration output corresponding to knocking and the average value output of vibration before top dead center are compared, and the number of times the vibration output from this vibration detector exceeds the average value output of vibration before top dead center. is measured within a predetermined rotation angle, the number of measurements is discriminated by a predetermined number of times, the strength of knocking of the internal combustion engine is determined, and the engine is retarded by an amount corresponding to the result of this determination. According to this method, even if large mechanical noise occurs due to an intake valve, an exhaust valve, etc., it can be determined as knocking without false detection. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be illustrated in the drawings and examples thereof will be described below. First, referring to FIG. 2, a case will be described in which the present invention is applied to an in-line six-cylinder internal combustion engine. 1 is a point attached to the distributor, which is connected to an igniter (not shown). 2
is a rotating disk attached to the crankshaft, and this disk is provided with three protrusions divided into three equal parts, and the protrusions correspond to the top dead center (TDC) of each cylinder of the internal combustion engine. 3 is a commercially available electromagnetic pick-up,
A signal is emitted at the location of the protrusion on the disc 2. 4 is a commercially available vibration detector using a piezo element, which is glued to the engine block. Reference numeral 5 designates a first waveform shaping circuit, which is a known circuit that includes a built-in circuit for preventing chattering of contact point 1, A shown in FIG. 3 is a point waveform, and B shown in FIG. 3 is a first waveform shaping circuit. This is the output waveform of circuit 5. Then, at the rising edge of the waveform A shown in FIG. 3, ignition is performed by an igniter (not shown). A second waveform shaping circuit 6 shapes the waveform of the output signal of the electromagnetic pickup 3. In Figure 3, C is the electromagnetic pick-up 3.
and D is the output signal of the second waveform shaping circuit 6. The internal circuit of this second waveform shaping circuit 6 is shown in FIG. 61 is an input terminal, one end of a low resistor 62 is connected to the input terminal 61, and the other end is commonly connected to a resistor 63, a positive electrode of a diode 64, and a negative electrode of a diode 65. The other end of the resistor 63 is connected to the inverting input terminal of a comparator 69 made of IC product number 3302 manufactured by Motorola, and a constant voltage Vc is applied to the negative electrode of the diode 64. The positive electrode of the diode 65 is grounded. One end of the resistor 66 is connected to the resistor 63
The other end is connected to the negative electrode of the diode 64. One end of the resistor 67 is connected to the negative electrode of the diode 64, and the other end is connected to one end of the resistor 68.
The other end of the resistor 68 is grounded. A connection point between the resistor 67 and the resistor 68 is connected to a non-inverting input terminal of a comparator 69. Since the output of the comparator 69 is an open collector, a resistor 70 is connected between the output and the power supply Vc. And comparator 69
The resistance values are determined so that the impedance seen from the non-inverting input terminal of the resistor is the same as the impedance seen from the inverting input terminal of the resistor.
Further, the non-inverting input terminal of the comparator 69 has a voltage of approximately 1/3Vc. Therefore, when the electromagnetic pickup 3 of the input terminal 61 is connected, approximately 1/3 Vc is also applied to the inverting input terminal of the comparator 69. The diode 65 prevents a negative voltage of −0.5 V or less from being applied to the inverting input terminal, and the diode 64 prevents a positive voltage of +(Vc+0.5 V) or more from being applied to the inverting input terminal. here,
The disk 2 moves and its protrusion becomes the electromagnetic pick-up 3.
The waveform shown in FIG. 3C is generated each time the signal passes through. Then,
The shaped pulse shown in FIG. 3D appears at the output of the comparator 69. This pulse corresponds to the top dead center (TDC) position of each cylinder. 7 is a control pulse generating circuit, and FIG. 5 shows its internal circuit. The input terminal 71 is connected to the first waveform shaping circuit 5, and the input terminal 71 is connected to the input 1B of a monostable multivibrator IC manufactured by Texas Instruments, product number SN74123. Input 1A is grounded. By connecting a capacitor 73 between the terminals 14 and 15 of the IC and a resistor 74 between the terminal 15 and the power supply Vc, after the output of the first waveform shaping circuit 5 rises, the capacitor 73 and the resistor 74 A pulse width of 10 μs is generated at output Q ₁ as shown in FIG. 3E.
Next, connect the NOR gates 76 and 77 to R-S as shown in the figure.
Connected to form a flip-flop, one input terminal of the NOR gate 76 is connected to the Q1 output of the monostable multivibrator ₇₂ , and the other input terminal of the NOR gate 77 is connected to the input terminal 75 of the control pulse generation circuit 7. and further connect the input terminal 7
5 to the output of the second waveform shaping circuit 6, the output of the NOR gate 76 is as shown in _FIG.
The output of NOR gate 77 produces ₁ , respectively.
Next, the monostable multivibrator 78 has an input terminal 75 connected to its input 2B. The operation of the monostable multivibrator 78 is similar to that of the monostable multivibrator 72 described above, and after the output of the second waveform shaping circuit 6 rises, the approximately
A pulse width of 100 μs is generated at the _Q2 output as shown in Figure 3, _S2 . By connecting one input of the two-input NOR gate 81 to the output terminal _Q2 and the other input to the output of the NOR gate 77 constituting the R-S flip-flop, the output of the NOR gate 81 is as shown in FIG. This occurs as shown in ₃ . The output terminals S ₁ , S ₁ , S ₂ , S ₃ of the control pulse generation circuit 7 correspond to the signals S ₁ , ₁ , S ₂ , S ₃ in FIG. 3, respectively. A buffer amplifier 8 converts the output signal of the vibration detector 4 into a low impedance signal. Therefore, the voltage waveform does not change. Reference numeral 9 denotes an absolute value circuit, which is a well-known circuit, so its explanation will be omitted, but the negative side of the vibration waveform is turned back to the positive side. Third
FIG. F shows the output waveform of the buffer amplifier 8, and G shows the output waveform of the absolute value circuit 9. 10 is a first integrator, in which a resistor 102 and a resistor 103 are connected in series with the output of the absolute value circuit 9, and one end of the resistor 103 is connected to the inverting input terminal of the operational amplifier 101. . An analog switch 104 is connected between the connection point between resistor 102 and resistor 103 and ground. The _S1 signal is applied to the control input of the analog switch 104. A capacitor 105 is connected between the inverting input and the output of the operational amplifier 101.
Further, an analog switch 106 and a resistor 107 are connected in series to both ends of the capacitor 105. The output signal S ₃ of the control pulse generation circuit 7 is applied to the control input of the analog switch 106 . In the above configuration, to explain the operation of the first integrator, when the signal _S4 is "1", the analog switch 104 is conductive;
When the output signal S ₃ is "1", _the analog switch 106 is conductive, so the output of the first integrator 10 is OV, and the output signal S ₁ When becomes "0", the analog switch 104 is opened, and at the same time, the analog switch 106 is also opened by the output signal _S3 , so the first integrator 10 starts integrating in the negative direction. This integration time is the time until the analog switch 106 closes, but since the output signal of the absolute value circuit 9 is input during the time when the analog switch 104 is open, the top dead center (TDC) That's it. Therefore, the time during which the signal _S2 shown in FIG. 3 is "1" is the holding time of the first integrator 10. The output voltage V ₁ of the first integrator 10 becomes −∫ ^T1 _p Gdt. The integrated waveform is as shown in FIG. 3H. On the other hand, the second integrator 11 has almost the same circuit configuration as the first integrator 10, but the variable resistor 11 is connected so that a constant voltage VR is applied to its integration input.
1 has been added. A constant power supply voltage Vc is applied to one fixed terminal of the variable resistor 111,
The other fixed terminal is grounded. second integrator 1
The operation of 1 changes the integral input voltage VR to “0” in Figure 3 S _1.
Since integration _is performed for ^T ₁ time in _the state _of
is proportional to. The integral waveform is as shown in FIG. 3I. Next, the divider 12 uses a multiplier 121 made by Intersil Corporation and made by product number 8013, which can be divided. A resistor 122 is connected to the Z input of the multiplier 121.
The output of the first integrator 10 is connected to the X input through a resistor 123, and the output of the second integrator 11 is connected to the X input. diode 1
The positive terminal of the diode 24 is connected to the Z input, the negative terminal of the diode 125 is connected to one terminal of the analog switch 126, and the positive terminal of the diode 125 is connected to the X input, and the negative terminal of the diode 125 is connected to one terminal of the analog switch 126. The other terminal of the analog switch 126 is connected to the negative power supply voltage Vs.
is applied. A signal _S3 from the control pulse generating circuit 7 is applied to the control terminal of the analog switch 126. The output of the multiplier 121 is connected to one fixed terminal of the variable resistor 127,
The other fixed terminals are grounded. The variable resistor 12
The movable terminal 7 is connected to the Y input. To explain the operation of the divider 12 with the above configuration, when the signal _S3 is "1", the analog switch 126 is closed, so the output of the first integrator 10 is connected to the resistor 12.
Since current flows through the second diode 124 and the analog switch 126, a negative voltage is applied to the Z input of the multiplier 121. Similarly, the second integrator 1
1 output causes resistor 123, diode 125,
Since current flows through analog switch 126, a negative voltage is applied to the X input of multiplier 121. Since a negative voltage must always be applied to the Z input and X input of the multiplier 121, the resistor 1
22, 123, diodes 124, 125, and analog switch 126 are required. Then signal S ₁
When is “0”, the analog switch 126 is open, so the Z input of the multiplier 121 has the first
Since the output of the second integrator 11 is directly applied to the X input via the resistors 122 and 123, the output of the second integrator 10 is applied to the X input.
10Z/X is output to the output _V3 of 2. In FIG. 3, when the S ₂ signal is "1" at the end of division, the output V ₃ of the divider 12 is: becomes. Here, V ₃ is a positive voltage as shown in FIG. 3J. The sample and hold circuit 13 uses Intersil's product number 1H5110, and the output of the divider 121 is connected to the analog input.
The control pulse generation circuit 7 is used as a control input.
A signal S ₂ from S2 is applied. Further, a resistor 131 and a capacitor 132 are connected in series to the C terminal. With the above circuit configuration, the output voltage of the divider 12 when the signal S ₂ is in the "1" state is sampled and held. Therefore, the sample hold circuit 13
The output voltage of the divider 1 is as shown in FIG.
The output voltage of V2 becomes _V3 . This _V3 is

[Formula] Therefore, it is the average value multiplied by a constant of the vibration from ignition to TDC (top dead center). One fixed terminal of the variable resistor 14 is connected to the output of the sample hold circuit 13, and the other fixed terminal is grounded. The variable terminal is connected to the inverting input of comparator 15. By doing this, the voltage V ⁴ of the variable terminal becomes

[Formula] becomes. K ₂ is a voltage division ratio divided by the variable resistor 14 . Now by setting K=K ₁ ×K ₂

〔Effect of the invention〕

As described above, in the present invention, the output of the vibration detector is compared with the knocking judgment level set from this detection output, and the number of times the ratio of the two is equal to or higher than a predetermined value is determined for each predetermined crank angle range in each ignition. The counting result is discriminated based on a plurality of preset values, an output corresponding to the knocking intensity is generated, and the ignition timing is retarded by an amount corresponding to the distinguished knocking detection output. Therefore, each knocking strength can be accurately discriminated, and there is an excellent effect that the ignition timing can always be quickly controlled to the optimum ignition timing for any knocking strength.

[Brief explanation of the drawing]

Fig. 1 is an output waveform diagram of each part to explain the basic operation of the device of the present invention, Fig. 2 is an electric circuit diagram showing an embodiment of the device of the present invention, and Fig. 3 is a diagram to explain the operation of the device shown in Fig. 2. Waveform diagrams of each part, Figures 4 to 6 are electrical circuit diagrams of main parts of the device shown in Figure 2, and Figure 7.
FIG. 6 is a waveform diagram of various parts for explaining the operation of the circuit shown in FIG. 6, and FIG. 8 is a retard correction amount characteristic diagram when the device of the present invention is applied to ignition advance correction. 4... Vibration detector, 10, 11, 12, 13...
...a first integrator constituting the determination level setting means,
a second integrator, a divider, a sample and hold circuit,
15... Comparator, 16... Number classification circuit.

Claims (1)

[Claims] 1. A vibration detector that detects vibrations propagating through an internal combustion engine, a determination level setting means for setting a determination level for knocking determination from the vibration output detected by the vibration detector, and a determination level from the determination level setting means. and a vibration output from the vibration detector, and generates an output each time a ratio between the vibration output from the vibration detector and the judgment level from the judgment level setting means is equal to or greater than a predetermined value. , the number of times the output of this comparison means is generated is counted for each predetermined crank angle range at each ignition of the internal combustion engine, and the counting results are discriminated based on a plurality of set values set in advance to determine the knocking detection output for the knocking occurrence intensity. A means for classifying the number of occurrences;
A knocking control device for an internal combustion engine, comprising: control means for retarding ignition timing by an amount corresponding to the knocking detection output of the number classification means.