JPS6235608B2 - - Google Patents

Description

[Detailed Description of the Invention] In order to prevent false positives, the present invention sets a relatively low judgment standard, and once knocking is determined, the judgment standard is raised over a predetermined period of time to eliminate consecutive false positives. The present invention relates to a knocking detection device.

As a conventional knocking detection device, for example, there is one shown in FIG. 1, which includes a vibration detection section 2 that outputs a vibration signal corresponding to the vibration of an engine 1, and a vibration detection section 2 that outputs a vibration signal corresponding to the vibration of an engine 1, and a background noise level ( Noise detection unit 5 that outputs a signal (hereinafter referred to as BGL)
, a determination section 6 that inputs a vibration signal and a BGL signal to determine engine knocking, and an advance angle control section 10 that delays the engine's ignition timing by a predetermined angle when knocking is determined. . The vibration detection unit 2 includes a vibration sensor 3 attached to the wall surface of the engine 1, and an amplifier 4 (a band that passes the knocking signal in the frequency band of 6 to 9 KHz) that amplifies the signal of the vibration sensor 3 to an appropriate level. The determination unit 6 compares the vibration signal with a determination reference (slice level) signal corresponding to the level of the BGL signal, and outputs a comparison signal when the vibration signal is large. 1 comparator 7 and an integrator 8 that outputs the integral value of the comparison signal (for example, the integral value is reset at each ignition timing). It is comprised of a second comparator 9 that determines knocking when it exceeds a predetermined value.

With the above configuration, the comparison signal output when the vibration signal corresponding to the output of the vibration sensor 3 exceeds the judgment reference signal corresponding to the level of the BGL signal is integrated, and the integral value reaches a predetermined value. Tokinotskin〓〓〓〓
It is determined that the ignition timing is off, and the ignition timing of the engine 1 is delayed to suppress the occurrence of knocking.

The level of the BGL signal is as shown in Figure 2.
It increases depending on the engine rotation speed (RPM). Furthermore, the knocking signals A ₁ , A ₂ , B ₁ , B ₂ and the noise signals A _x , _B and change. For this reason, knocking is determined based on a comparison between the vibration signal and a determination reference signal predetermined according to the vehicle speed.

However, the cylinders where knocking is more likely to occur may differ depending on the engine, and as shown in Figure 4, even if the BGL signal level is the same,
There are two types of vibration sensors: high detection sensitivity and low detection sensitivity. Therefore, when making judgments using the judgment reference signal based on the BGL signal, if the judgment reference signal is set as S ₁ , knocking cannot be detected in B, and if the judgment reference signal is set as S ₂ , noise will be detected as in A. was detected, making it difficult to set the judgment reference signal, and there was a risk that the control of the engine's ignition timing would lack accuracy.

In view of the above, the present invention eliminates the failure to detect knocking by using a low-level judgment reference signal in order to prevent failure in detection and improve the accuracy of engine control. The time determination reference signal is increased, that is, the determination sensitivity is decreased.

In other words, in knocking control, the torque is controlled to be close to trace knocks and light knocks, which have a small decrease in torque, low knock strength, and low knock frequency, and these trace knocks and light knocks rarely occur consecutively, and only occur after several tens of seconds. They occur at intervals on the order of seconds. When trying to control knocking to such a level, it is not necessary to detect knocking with high sensitivity for each ignition, but rather to compensate for variations in sensitivity caused by the engine and vibration sensor, it is necessary to lower the judgment reference signal somewhat to determine knocking. In order to minimize the influence of excessive advance angle control in the case where a very small number of consecutive determinations are made, a knocking detection device is provided that increases the determination reference signal once a determination is made. This is what we provide.

The knocking detection device of the present invention will be explained in detail below.

FIG. 5A shows a first embodiment of the present invention.
The same parts as in the figure are indicated by the same quotation numerals, so repeated explanations will be omitted. However, in addition to the configuration shown in FIG. ing. The signal control unit 15 is a determination unit (as described later, in the present invention, detection accuracy is improved, so a single comparator may be used)
6 is triggered by the judgment signal output when knocking is detected, for example, a predetermined time that is slightly shorter than the (10 to 10 ³ ) millisecond time that is the interval between occurrences of trace knocks, light knocks, etc. A timer circuit 17 outputs a signal with a predetermined value over time, and the signal value is transmitted to the noise detector 5.
It consists of an addition circuit 16 that outputs the added value added to the BGL signal to the determination section 6.

FIG. 5B shows an embodiment of the time limit circuit 17,
Resistors R ₁ , R ₂ and capacitor C ₁ make up the differential circuit, resistor R ₃ and transistor T ₁ make up the amplifier circuit, transistor T ₂ is turned on by the output of transistor T ₁ , and transistor T ₂ makes up the differential circuit. It has a small resistance R ₄ , a large resistance R ₅ and a capacitor C ₂ that constitute a charging/discharging circuit that charges and discharges on and off.

In the above configuration, the operation of the vibration sensor 3 in the case of high sensitivity (FIG. 6 A) and low sensitivity (FIG. 6 B) will be explained. The vibration signal of the vibration detection section 2 is compared with the level judgment reference signal S set so as to be able to detect the low-sensitivity knocking signal A _b according to the knocking signal A _b (the adder circuit 16 is not working yet). Alternatively, when the integral value obtained by integrating the pulses output when A _b is detected reaches a predetermined value, a determination signal is output. The differentiating circuit of the timer circuit 17 to which the judgment signal is input differentiates the falling edge of the input pulse, and the amplifying circuit of the transistor T 1 amplifies the differential value, and the amplifying circuit of the transistor T ₁ amplifies it to the resistor R ₂ ,
Outputs a pulse with a pulse width determined by capacitor _C1 . This pulse turns on transistor T ₂ and charges capacitor C ₂ through small resistor R ₄ . After the time of the pulse width of said pulse has elapsed, the transistor T ₂ is turned off and the capacitor C ₂ is discharged through the large resistance R ₅ for said predetermined time (the pulse width of said pulse is shortened by the firing interval). Therefore, the charging time of capacitor _C2 should not be longer than the charging time of capacitor C2.
Therefore, the time constants of R ₂ and C ₁ are equal to R ₄ and C ₂
(must be set longer than the time constant).
The terminal voltage value resulting from charging and discharging of the capacitor C ₂ is output to the adding circuit 16 , added to the BGL signal, and input to the determining section 6 . Therefore, when the determination unit 6 detects the knocking signal A _a or A _b and inputs the determination signal to the timer circuit 17, the determination reference signal S has a high level for a predetermined period of time, resulting in low sensitivity. Not to mention the noise signal B _b , the highly sensitive noise signal B _a will no longer be detected (in addition,
In Fig. 6A, even if the high-sensitivity noise signal B _a is detected and the level of the judgment reference signal S increases, the next knocking signal A _a can be detected, so in the state of Fig. 6A, the next knocking signal A a can be detected. (can be detected).
The determination signal is also input to the advance angle control section 10,
Delays engine ignition timing.

Note that if a monostable multivibrator that is turned on for a predetermined time when a judgment signal is input is used as the time limit circuit 17 of the signal control unit 15, the results shown in FIG.
Detection can be performed as shown in FIG. 7, A and B, which correspond to B, respectively.

FIG. 8 shows a second embodiment of the present invention, and the same parts as in the first embodiment are indicated by the same quotation numerals, so a repeated explanation will be omitted. They are different in that they are comprised of a timer circuit 19 that outputs a timer signal for a predetermined period of time when an event occurs, and a transistor 20 that is turned on by the timer signal.

With the above configuration, when the determination section 6 outputs the determination signal, the timer circuit 19 outputs the timer signal for a predetermined period of time and turns on the transistor 20, so that the vibration signal of the vibration detection section 2 is blocked and the Stop the detection operation for a period of time.

Note that the connection point of the collector terminal of the transistor 20 is not set at the illustrated position. Further, the transistor 20 may be a PNP transistor.

In each of the above-mentioned embodiments, the embodiments shown in FIGS. 6A and 6B are effective when a noise that is confused as knocking occurs immediately after knocking, and the embodiments shown in FIGS.
Embodiment B is effective when the timing at which noise occurs varies.

As explained above, according to the knocking detection device according to the present invention, excessive advance angle control is minimized, the judgment reference signal is lowered, and detection omissions due to variations in sensitivity caused by the engine and vibration sensors are eliminated, and engine The accuracy of control can be improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a conventional knocking detection device, and FIG. 2 is an explanatory diagram showing the relationship between engine speed and BGL signal. FIGS. 3A and 3B are explanatory diagrams showing vibration signals at low speed and high speed, respectively. FIGS. 4A and 4B are explanatory diagrams showing vibration signals from low-sensitivity and high-sensitivity vibration sensors, respectively. FIG. 5A is an explanatory diagram showing the first embodiment of the present invention, and FIG. 5B is an explanatory diagram showing the time limit circuit of A. FIGS. 6A and 6B are explanatory diagrams showing vibration signals from low-sensitivity and high-sensitivity vibration sensors, respectively, in the first embodiment. FIGS. 7A and 7B are explanatory diagrams corresponding to FIGS. 6A and 6B in a modification of the first embodiment. FIG. 8 is an explanatory diagram showing a second embodiment of the present invention. Explanation of symbols, 1...Engine, 2...Vibration detection section, 3...Vibration sensor, 4...Amplifier, 5...Noise detection section, 6...Judgment section, 7, 9...Comparator, 8
...Integrator circuit, 15...Signal control unit, 16...Addition circuit, 17...Time limit circuit, 19...Timer circuit, 20...Transistor. 〓〓〓〓

Claims (1)

[Scope of Claims] 1. A vibration detection unit that outputs a vibration signal corresponding to engine vibration; a noise detection unit that detects background noise vibration of the engine included in the vibration signal and outputs a background noise signal; Based on the background noise signal,
and a determination unit that determines knocking and outputs a determination signal when the vibration signal becomes larger than a determination reference signal set to a level close to the background noise signal; A knocking detection device comprising: a signal control section that suppresses detection of vibration over time. 2. The signal control unit includes: a time limit circuit that outputs a signal of a predetermined value for a predetermined time when the determination signal is output; The knocking detection device according to claim 1, further comprising an addition circuit that outputs a new background noise signal to the determination section. 3. The knocking detection device according to claim 1, wherein the signal control section includes a circuit that blocks input of the vibration signal to the determination section when the determination signal is output.