JPH076487B2 - Control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a knock control device for an internal combustion engine, which suppresses knocking of the internal combustion engine.

[Conventional technology]

Although there are fuel control, ignition timing control, supercharging pressure control, and the like as control methods for detecting and suppressing knocks generated by the engine, the ignition timing control that is most practically used will be described below.

The conventional ignition timing control system for an internal combustion engine shown in FIG. 4 will be described below.

In FIG. 4, 1 is an acceleration sensor which is attached to the engine and detects vibration acceleration of the engine. 2 is a frequency filter which passes a signal component having a high sensitivity to knocking among output signals of the acceleration sensor 1. 3 is a frequency. It is an analog gate that blocks noise that becomes an interfering wave for knock detection in the output signal of the filter 2.

Further, the gate timing controller 4 instructs the opening / closing of the analog gate 3 in accordance with the time of occurrence of the disturbing noise.

The output of the analog gate 3 is sent to the noise level detector 5 and the comparator 6. The noise level detector 5 detects the level of mechanical vibration noise of the engine other than knocking.

Further, the comparator 6 compares the output voltage of the analog gate 3 with the output voltage of the noise level detector 5 to generate a knock detection pulse and output it to the integrator 7.

The integrator 7 integrates the output pulse of the comparator 6 and generates an integrated voltage roughly equal to the knocking intensity.

The phase shifter 8 displaces the position of the reference ignition signal according to the output voltage of the integrator 7.

On the other hand, 9 is a rotation signal generator that generates an ignition signal according to a preset ignition advance characteristic. The output of this rotation signal generator 9 is shaped by a waveform shaping circuit 10 and, at the same time, the ignition coil 12 is energized. The closing angle control is performed.

In addition, a switching circuit is provided by the output signal of the phase shifter 8.
Reference numeral 11 is adapted to intermittently supply power to the ignition coil 12.

FIG. 5 shows frequency characteristics of the output signal of the acceleration sensor 1. In FIG. 5, A is the case where there is no knocking,
B is the case where knocking occurs.

The output signal of the acceleration sensor 1 includes a knock signal (a signal generated by knocking), mechanical noise of the engine other than the knock signal, and various noise components on the signal transmission path, such as ignition noise. . Comparing the characteristics A and B in FIG. 5, it can be seen that the knock signal has a unique frequency characteristic.

Although this distribution varies depending on the engine or the mounting position of the acceleration sensor 1, there is a clear difference in the distribution depending on the presence or absence of knocking in each case. Therefore, the noise of other frequency components can be suppressed by passing the frequency component of this knock signal, and the knock signal can be efficiently detected.

6 and 7 show the operation waveforms of the respective parts in FIG. 4, and the same reference numerals show the waveforms of the same parts. FIG. 6 shows a mode in which no knocking occurs in the engine, and FIG. 7 shows the engine. Shows the mode in which the knocking is occurring.

Next, the operation of the ignition timing control system for the internal combustion engine of FIG. 4 will be described. The ignition signal generated by the rotation signal generator 9 corresponding to the ignition timing characteristic set in advance by the rotation of the engine is waveform-shaped by the waveform shaping circuit 10 into an opening / closing pulse having a desired closing angle, and the phase shifter 8 The engine is ignited and operated by the ignition voltage of the ignition coil 12 generated when the switching circuit 11 is driven via the switch to interrupt the power supply to the ignition coil 12 and the energization current is interrupted. The engine vibration that occurs during operation of this engine is detected by the acceleration sensor 1.

Now, when the engine is not knocked, the engine vibration due to the knocking does not occur, but other mechanical vibration causes the output signal of the acceleration sensor 1 to generate mechanical noise as shown in FIG. 6 (a). Ignition noise that rides on the signal transmission path at the ignition timing F occurs.

As this signal passes through the frequency filter 2, the mechanical noise component is considerably suppressed as shown in FIG. 6 (b), but the ignition noise component is strong, so that it has a large level even after passing through the frequency filter 2. May be output with.

As it is, the ignition noise is mistakenly recognized as a knock signal. Therefore, the analog gate 3 is triggered by the output of the phase shifter 8 and is output by the gate timing controller 4 (FIG. 6 (c)). Then, the gate is closed for a certain period from the ignition timing to shut off the ignition noise. Therefore, only the low level mechanical noise remains at the output of the analog gate 3 as shown in FIG. 6 (d).

On the other hand, the noise level detector 5 responds to a change in the peak value of the output signal of the analog gate 3 and, in this case, has a characteristic of being able to respond to a relatively gentle change due to the peak value of the normal mechanical noise. A DC voltage slightly higher than the peak value of noise is generated ((b) in FIG. 6 (d)).

Therefore, as shown in FIG. 6D, since the output of the noise level detector 5 is larger than the average peak value of the output signal of the analog gate 3, the comparator 6 for comparing these
As shown in FIG. 6 (c), nothing is output, and eventually all noise signals are removed.

Therefore, the output voltage of the integrator 7 remains zero as shown in FIG. 7 (f), and the phase shift angle by the phase shifter 8 (input / output (FIG. 7)
The phase difference between (g) and (h)) is also zero.

Therefore, the opening / closing phase of the switching circuit 11 driven by this output, that is, the intermittent phase of energization of the ignition coil 12 becomes the same phase as the reference ignition signal of the output of the waveform shaping circuit 10, and the ignition timing is the reference ignition timing. Become.

When knocking occurs, the output of the acceleration sensor 1 includes a knock signal in the vicinity of a certain time delay from the ignition timing as shown in FIG. 7 (a), and after passing through the frequency filter 2 and the analog gate 3. 7 (d), the knock signal is largely superposed on the mechanical noise as shown in (a) of FIG.

Of the signals that have passed through the analog gate 3, the rising edge of the knock signal is steep, so that the level of the output voltage of the noise level detector 5 is delayed in response to the knock signal. As a result, the inputs of the comparator 6 become a and b of FIG. 7 (d), respectively, so that a pulse is generated at the output of the comparator 6 as shown in FIG. 7 (e).

The integrator 7 integrates the pulse and generates an integrated voltage as shown in FIG. 7 (f). Since the phase shifter 8 shifts the output signal of the waveform shaping circuit 10 (FIG. 7 (g) (reference ignition signal)) to the delay side in time according to the output voltage of the integrator 7, the phase shifter 8 shifts the phase. The output of the device 8 is delayed in phase from the phase of the reference ignition signal of the waveform shaping circuit 10, and drives the switching circuit 11 at the phase shown in FIG. 7 (h). As a result, the ignition timing is delayed and knocking is suppressed. Eventually, the states shown in FIGS. 6 and 7 are repeated to perform optimum ignition timing control.

[Problems to be solved by the invention]

In the above-mentioned conventional device, each of the acceleration sensor 1 and the comparator 6 is one, and the knock detection system is one.

However, with the recent increase in engine output, if the number of cylinders in the engine is 6 or more, or if the cylinder block shape of the engine is a so-called V-shape, a single detection system can reduce the occurrence of knocks in all cylinders. As described above, it may not be possible to reliably detect, and a plurality of knock detection systems may be provided.

In this case, even if a plurality of knock detection systems are simply provided, the frequency distribution of the knock signal and the noise varies depending on the mounting position of the knock sensor, so that the knock detectability is not sufficient.

The present invention has been made to solve such a problem, and makes the frequency characteristic in the knock detection characteristic of each knock detection system the best in each detection system, so that the knocks generated in all cylinders are uniformly and at a sufficient level. An object is to obtain a knock control device for an internal combustion engine that can be detected.

[Means for solving problems]

The knock control device for an internal combustion engine according to the present invention is provided with a plurality of knock detection systems each having an acceleration sensor having different characteristics and a pair of frequency filters.

[Work]

In the present invention, the characteristics of each component in each knock detection system are designed to be optimal for that detection system, and knock detection is performed reliably.

〔Example〕

An embodiment of a knock control device for an internal combustion engine of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. The portions denoted by reference numerals 4 and 7 to 12 in FIG. 1 are the same as those in FIG. 4, and the portions described below are portions which characterize the present invention, unlike FIG.

That is, in the embodiment of FIG. 1, first and second knock detection systems 100 and 200 are provided. In the first and second knock detection systems 100 and 200, 51 and 61 are acceleration sensors (corresponding to the acceleration sensor 1 in FIG. 4) that detect vibration acceleration of the engine.

The outputs of the acceleration sensors 51, 61 are sent to the frequency filters 52, 62, respectively. Frequency filter 52,62
Only the knock signal component is selected and output from the outputs of the acceleration sensors 51 and 61 (corresponding to the frequency filter 2 in FIG. 4).
These outputs are analog gates 53 and 63, respectively.
I am trying to output to.

The analog gates 53 and 63 block the noise that becomes an interfering wave for the knock detection in the output signals of the frequency filters 52 and 62, respectively (corresponding to the analog gate 3 in FIG. 4).

The outputs of the analog gates 53 and 63 are sent to the noise level detectors 55 and 65 and the comparators 56 and 66, respectively.

The noise level detectors 55 and 65 detect the mechanical vibration noise level of the engine other than knocking and use it as the reference voltage (corresponding to the noise level detector 5 in FIG. 4), and the comparators 56 and 66 are The output voltage of the analog gate 53, 63 is compared with the output voltage of the noise level detector 55, 65 to generate a knock detection pulse (corresponding to the comparator 6 in FIG. 4).
It is a thing.

The outputs of both comparators 56 and 66 are sent to the OR circuit 70. The OR circuit 70 outputs the logical sum signal of the knock detection pulses from the outputs of both comparators 56 and 66.

As described above, the first knock detection system 100 includes the acceleration sensors 51 to
The second knock detection system 200 includes a comparator 56, and the second knock detection system 200 includes an acceleration sensor 61 to a comparator 66.

In each of the first and second knock detection systems 100 and 200, the basic operation of the block circuit of each configuration is the same as that of the conventional device described above, and the connection between the block circuits is also as shown in FIG. Therefore, the description of the basic operation of knock detection will be omitted.

This embodiment has two knock detection systems, that is, the first and second knock detection systems 100 and 200, and the first knock detection system.
The knock detection pulses output from the comparator 56 of 100 and the comparator 66 of the second knock detection system 200 are converted into respective OR signals by the OR circuit 70 and input to the integrator 7.

Since the integrator 7 generates the control voltage corresponding to the input pulse as in the conventional device (FIG. 4), even if the knock is detected in any of the first and second knock detection systems 100 and 200, the integrator 7 outputs the control voltage. A control voltage is generated, the ignition timing is retarded, and knocking of the engine is suppressed.

By the way, the detection signals of the acceleration sensors 51 and 61 are basically different from each other because they change depending on the mounting position of the engine as described above.

This is because the knock signal of the engine is often a component of several KHz to 10 KHz, and this frequency belongs to the high frequency in the vibration characteristics of the cylinder block of the engine and represents a very delicate characteristic.

That is, each detection signal of the acceleration sensors 51, 61 has the frequency characteristic of the noise signal and the knock signal of the engine as shown in FIG. 5, and the knock component appears at the same level with respect to the noise component between the detection signals. Then, if the first and second knock detection systems 100 and 200 having exactly the same characteristics are configured for only two systems (providing two block circuits for each), desired knock detection can be performed. become.

However, since the actual detection signals are subtly different from each other in terms of frequency or level, when the characteristics of the constituent block circuits of the above two types of knock detection systems are the same and the detection characteristics are exactly the same, the knock detectability is Is rarely the best.

For example, if the frequency component of the detection signal from the acceleration sensor 51 has the characteristics shown in FIG. 5 depending on whether the engine is knocked or not, the frequency component of the detection signal from the acceleration sensor 61 attached at one different position is shown in FIG. 2 or FIG. become that way.

In these figures, the characteristic A represents the frequency characteristic when the engine is not knocked, and the characteristic B is the frequency characteristic when the engine is knocked.

FIG. 2 shows a case where the characteristic B when a knock occurs in the engine differs from the frequency characteristic of FIG. 5 and the level of the knock signal is small.

FIG. 3 shows the case where the frequency distribution of the knock signal is the same as that of FIG. 5, but the level of the noise signal when the engine is not knocked is higher than the characteristic A of FIG.

When the detection signals of the acceleration sensors 51 and 61 are different as described above, the frequency filters 52 and 62 must be set so as to have different frequency selectivity in order to obtain an output signal that can surely perform knock detection from each input signal. I have to. Its main characteristics are center frequency, center frequency voltage gain, bandwidth, etc.

The center frequency is set to a frequency at which the noise signal component is small and the knock signal component is large, and the frequency selectivity is determined together with the setting of the bandwidth. Center frequency voltage gain is the voltage amplification factor that sets the output signal to the desired voltage.

2 and 3 show the characteristics A when knock does not occur.
There is a difference in the distribution of the knock signal or the noise between the characteristic B and the characteristic B when the knock occurs (the knock signal frequency is constant), but the distribution of the knock signal and the noise is not limited to these. There may be no difference and the knock signal frequencies may simply differ.

In this embodiment, the acceleration sensors 51 and 61 have flat frequency characteristics, and the frequency filters 52 and 62 are provided with frequency selectivity. However, when the acceleration sensors having resonance characteristics are used, this frequency selectivity is also provided. Therefore, to make the frequency selectivity different between the knock detection systems 100 and 200,
Accelerometers with different resonance characteristics are required.

As described above, since the input signals of the frequency filters 52 and 62 and the frequency selectivity of each of them are different from each other, the noise signal of each output signal and the voltage of the knock signal (each peak value and its fluctuation) are different from each other, and the noise Level detector
The respective characteristics of 55 and 65 cannot be surely detected by the comparators 56 and 66 unless the characteristics are optimized for each input signal.

That is, the voltage relationship between the two types of inputs of each of the comparators 56 and 66 is a and b of FIG. 6 (d) described in the conventional apparatus of FIG. 4 (when the engine is not knocked), and The characteristics of each of the noise level detectors 55 and 65 must be optimized for each input signal so that there is always a relation between a and b in FIG. 7 (d) (when a knock occurs in the engine). .

The characteristics of the noise level detectors 55 and 65 include offset voltage and voltage gain. The offset voltage represents the output voltage when there is no input, and the voltage gain represents the amplification factor of the input signal.

As described above, when the acceleration sensors 51 and 61 are attached at different positions, the characteristics of the respective detection signals are different, so that the characteristics of the frequency filters 52 and 62 or the noise level detectors 55 and 65 are set to the respective knock detection systems. Unless the characteristics are different from each other, it is not possible to obtain the optimum characteristics that can surely detect the knock in each knock detection system.

When the acceleration sensors 51 and 61 have resonance characteristics, it is necessary to make the resonance characteristics different from each other.

〔The invention's effect〕

As described above, according to the present invention, the knock information of the engine is detected by the knock sensor, the knock signal component is selectively output from the knock information by the frequency filter, and the reference voltage for knock detection is generated from this output, and the reference voltage and the frequency filter are generated. In the device for detecting knocks generated in the engine from the comparison with the output of the above, when a plurality of knock detection systems are provided, the specifications of the acceleration sensor and the frequency filter provided in a pair are different between the knock detection systems. Since it has been made to have the characteristics, it is possible to obtain the optimum characteristics in each knock detection system, and the characteristics of each knock detection system can detect the knocks of all cylinders of the engine uniformly and surely. Is what you get.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of an embodiment of a knock control device for an internal combustion engine of the present invention, and FIGS. 2 and 3 are outputs of an acceleration sensor for explaining the operation of the knock control device for an internal combustion engine. FIG. 4 is a block diagram of a conventional knock control device for an internal combustion engine, and FIG. 5 is a diagram showing an output of an acceleration sensor for explaining the operation of the knock control device for an internal combustion engine of FIG. FIG. 6 is an operation waveform diagram of each part in a mode in which the engine is not knocking, for explaining the operation of the knock control device for the internal combustion engine of FIG. 4, and FIG. 7 is a knock diagram of the internal combustion engine of FIG. FIG. 9 is an operation waveform diagram of each part in a mode in which the engine is causing knocking, for explaining the operation of the control device. 4 ... Gate timing controller, 7 ... Integrator, 8 ...
Phase shifter, 9 ... Rotation signal generator, 10 ... Waveform shaping circuit,
11 ... Switching circuit, 12 ... Ignition coil, 51,61 ...
… Accelerometer, 52,62 …… Frequency filter, 53,63 ……
Analog gate, 60 ... OR circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An acceleration sensor for obtaining knock information by detecting vibration acceleration of an engine, a frequency filter for selecting and outputting a knock signal component from the knock information, and a reference voltage generation for generating a reference voltage from the output of the frequency filter. Means for detecting the knock of the engine from the comparison of the output of the frequency filter and the reference voltage, and controlling the ignition timing of the engine to control the knock to suppress the knock, the acceleration sensor, the frequency filter and the reference voltage A plurality of knock detection systems are provided with the respective generating means, frequency filters are connected to the acceleration sensor in a pair, and the frequency filters of each knock detection system have different characteristics for each knock detection system. A knock control device for an internal combustion engine, comprising: