JPS6240538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking control device for a turbocharged engine.

In order to improve the output and fuel efficiency of a gasoline engine or diesel engine, a turbocharger may be installed.

This turbocharger uses the energy of the engine's exhaust gas to turn the turbine, and also relatively increases the amount of intake air supplied to the engine cylinders by the compressor driven by the turbine, increasing the supercharging rate. The output of the engine is increased accordingly.

However, when this turbocharger is installed, the pressure of the intake air increases according to the supercharging rate.
Knocking is likely to occur due to the accompanying rise in air temperature. If this knocking is particularly severe and occurs frequently, it may cause partial overheating or abnormal vibration of the engine, impairing the durability of the engine, and resulting in a reduction in engine output.

For this reason, conventionally, when installing a turbocharger, measures have been taken, such as increasing the volume of the combustion chamber of the engine and lowering the compression ratio of the engine, thereby suppressing the occurrence of knocking.

However, even if supercharging is carried out, the output and fuel efficiency will not be significantly improved.

Therefore, it is known that the occurrence of knocking can be controlled by delaying the ignition timing as shown in Figure 1. Knocking is suppressed by controlling the ignition timing to be delayed.

In addition, as shown in Figure 2, the occurrence of knocking is greatly affected by the air-fuel ratio of the engine, and it becomes less likely to occur as the stoichiometric air-fuel ratio A/F = 14.5 is made richer or leaner.
(indicates the ignition timing that can generate the maximum torque), and as seen in JP-A No. 55-43206, for example, in response to the occurrence of knocking, the air-fuel ratio is shifted to the rich side to prevent knocking. It has also been proposed to avoid or suppress

Furthermore, as seen in JP-A-54-112, patterns such as ignition timing and air-fuel ratio that have been stored in advance according to operating conditions can be modified or rewritten according to the state of occurrence of knocking. It has also been proposed to enable the engine to always be simulated under optimal operating conditions.

However, in turbocharged engines, as shown in Figure 3, the knocking limit is MBT, especially in high-speed, high-load ranges where the supercharging rate is high.
Since the ignition timing is shifted to a considerably delayed side from the ignition timing that can generate the maximum torque, if the ignition timing is corrected to near the knocking limit, the engine output will decrease as shown in Figure 4, and acceleration performance and hill climbing performance will be affected. There is a problem with damage.

On the other hand, in order to suppress the occurrence of knocking by controlling the air-fuel ratio, it is necessary to
Although it is effective to lower the exhaust temperature by shifting the air-fuel ratio to the rich side, there is a problem in that fuel efficiency deteriorates if air-fuel ratio control is always performed based on knocking detection.

The present invention solves all of the problems caused by these conventional knocking control devices, and effectively suppresses the occurrence of knocking in the entire operating range of a turbocharged engine without reducing output or deteriorating fuel efficiency. The purpose of this invention is to constantly control engine knocking to a slight knocking state that does not cause damage or the like, and to fully enhance the performance of the turbocharger to improve fuel efficiency and output characteristics.

In order to achieve the above object, the knocking control device for an engine equipped with a turbocharger according to the present invention includes a knocking detection means for detecting engine knocking, and corrective control of the ignition timing to the retarded side in accordance with a detection signal of the knocking detection means. ignition timing control means for correcting the air-fuel ratio to the rich side in response to the detection signal of the knocking detection means; means for detecting the operating state of the engine; A switching means is provided for switching and outputting the detection signal of the knocking detection means to the air-fuel ratio control means in a load range and to the ignition timing control means in other operating ranges.

The knocking control device according to the present invention configured as described above corrects and controls the ignition timing to the retarded side when knocking is detected in an engine operating range other than the high-speed, high-load range, thereby preventing deterioration in fuel efficiency and reduction in output. It effectively suppresses the occurrence of knocking, and when knocking is detected at high speeds and high loads, the air-fuel ratio is corrected to the rich side, lowering the exhaust temperature without reducing output, and effectively suppressing knocking. suppress.

Therefore, the above objective can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to FIG. 5 and subsequent figures of the accompanying drawings.

First, an overview of the system configuration of a turbocharger-equipped engine equipped with a knocking control device according to the present invention will be explained with reference to FIG.

The turbocharger 2 that supercharges intake air to the engine 1 includes a turbine 4 installed in an exhaust passage 3 (3a, 3b) through which exhaust gas from the engine 1 is discharged, and a turbine 4 installed in an intake passage 5. 4 and a compressor 6 which rotates coaxially.

Then, the exhaust gas discharged from the engine 1 is transferred to the exhaust passage 3 until the boost pressure reaches a predetermined value.
a, exhaust intake port 4a, turbine 4, exhaust outlet 4
b. After passing through the three-way catalyst 7 that removes harmful components from the exhaust gas through the exhaust passage 3b, it is discharged outside, thereby driving the turbine 4 to rotate according to the energy of the exhaust gas.

As a result, when the compressor 6 rotates,
Intake air flowing in through the air cleaner 8 and air flow sensor 9 is compressed and supercharged to the engine 1 through the air intake port 6a, compressor 6, air outlet 6b, throttle valve 10, and intake manifold 11. When the supercharging pressure exceeds a predetermined value, the bypass valve 12 opens according to the supercharging pressure, and part of the exhaust gas is discharged into the exhaust passage 3b through the bypass passage 3c, causing excessive supercharging pressure. It's learned not to get too big.

In this way, turbocharger 2 uses the energy of exhaust gas to forcibly increase the amount of intake air.
This increases the engine's output.

In addition, the exhaust gas is EGR orifice 13, EGR
The NOx gas is returned to the intake system via the passage 14 and the EGR valve 15 to reduce the NOx concentration in the exhaust gas. Note that the EGR valve 15 is controlled to open and close depending on the operating state of the engine.

The control unit 16 includes a throttle valve switch 17 that is turned on when the throttle valve 10 reaches a predetermined opening or more, a water temperature sensor 18 that is attached to the thermostat housing and detects the engine cooling water temperature, and a water temperature sensor 18 that is installed in the exhaust passage 3b. The fuel injection amount and ignition are determined based on the detection signals from the _O2 sensor 19, which is attached to the engine and detects the oxygen concentration in the exhaust gas, and the vibration sensor 20, which is attached to the cylinder block of the engine and detects engine vibrations. The basic value of the timing and its correction value are determined.

Then, the control unit 16 controls the fuel injection valve 21 and the igniter 22 according to the determined value.
An ignition plug 25 is controlled via an ignition coil 23 and a power distributor 24 to perform fuel injection and ignition.

Next, the details of the control unit 16 will be explained in the sixth section.
This will be explained with reference to the figures and subsequent figures.

In FIG. 6, the vibration of the engine 1 is detected by a resonance type vibration sensor 20 attached to the main body of the engine 1 (see FIG. 5), and the detected signal S is sent to the amplifier 26 of the control unit 16. Quantitative amplification is performed to obtain a signal S' as shown in FIG. 7C. It is assumed that the resonance frequency of the vibration sensor 1 is approximately equal to the knocking frequency range of the engine.

Next, the signal S' is half-wave rectified, averaged, and amplified by an averaging circuit 27 consisting of a rectifier, an integrator (large discharge time constant), an amplifier, etc. A comparison signal Sr is formed.

Then, this comparison signal Sr and the output signal S' of the amplifier 26 are inputted to the comparator 28 and compared, and when S'≧Sr, it is considered that knocking has occurred, and the magnitude of the knocking is determined as shown in FIG. A pulse signal Sp that becomes high level "H" a corresponding number of times is output.

By the way, even when knocking is not occurring, electrical spike-like noise and sharp mechanical vibrations are intermittently mixed into the signal S', so a signal that is not caused by knocking may appear in the output of the comparator 28. There is.

Therefore, in order to remove the erroneous signal, the pulse signal Sp from the comparator 28 is integrated by the integrator 29 and converted into a voltage signal Vp as shown in FIG. Therefore, the reference voltage Vref ₁
In comparison, only the signal due to knocking is extracted.

That is, the comparator 30 determines that knocking has occurred when Vp≧Vref ₁ , and outputs a knocking determination signal S _N that remains at a high level "H" for a predetermined period as shown in FIG. Therefore, the presence or absence of knocking can be determined from this knocking determination signal S _N .

In this embodiment, in order to determine the presence or absence of knocking for each ignition, a differential signal obtained by differentiating the point signal S _F (see FIG. 7A) from the power distributor 24 by a differentiator 31 is used. Sf (see Figure 7 B)
The output Vp of the integrator 29 is reset at each rising edge of the integrator 29.

The knocking determination signal S _N obtained as described above is further input to an integrator 32 to obtain a voltage signal V _N (see FIG. 7) corresponding to the frequency of knocking occurrence. This integrator 32 increases the amount of integration in accordance with the high level period (constant) every time the knocking determination signal S _N becomes high level "H",
The integrated amount is discharged at a relatively large constant time constant to be reduced to zero. Therefore, the voltage signal V _N increases as the knocking frequency increases, and becomes zero when knocking no longer occurs.

These vibration sensor 20, amplifier 26, averaging circuit 27, comparator 28, integrator 29, comparator 3
0. The integrator 32 and the like constitute knocking detection means for detecting engine knocking.

Based on the voltage signal V _N obtained by this knocking detection means, the ignition timing is retarded in the engine partial load range and low to medium speed rotation range, and the fuel injection amount is increased in the high speed and high load range. However, if the voltage signal _VN remains unchanged, it cannot be used as an ignition timing or air-fuel ratio control signal.

Next, we will discuss how to create each control signal.

Point signal S _F output from the power distributor 24
(see Fig. 7A) is converted into a voltage signal V _S proportional to the engine speed by an F/V converter 33, and further, the voltage signal V _S is converted into a current signal I by a voltage/current converter 34. Convert to _S.

Using this current signal I _S and the differential signal Sf shown in FIG. 7B obtained by differentiating the point signal S _F from the differentiator 31, the integrator 35 generates a triangular wave signal S _K as shown in FIG. 7G. form.

Then, this triangular wave signal S _K and the _voltage signal V _N from the integrator ₃₂ are input to the comparator 36 and compared, and the signal S _R (seventh (see Figure H). Note that the pulse width of this signal S _R is proportional to the knocking occurrence frequency.

This signal S _R is used to perform ignition timing control and air-fuel ratio control, and switching between these two controls is performed by a switching circuit 37.

That is, the switching circuit 37 is the F/V converter 33,
In response to the detection signal from the engine operating state detection means constituted by the comparator 38 and the AND circuit 39, the signal S
_R is switched and outputted to the AND circuit 40 of the ignition timing control system, and to the air-fuel ratio control circuit 41 of the air-fuel ratio control system in the high load high rotation range.

To explain specifically, the above-mentioned F/V converter 3
Comparator 3 outputs a voltage signal V _S corresponding to the engine speed output from Comparator 3 and a reference voltage Vref ₂ corresponding to the high rotation range (for example, 3000 rpm or more) (see Fig. 8 A).
8, _the signal S _H ( _8th
(see figure b).

Next, this signal S _H and the throttle valve 10
becomes high level “H” when the opening is above the specified opening,
The signal S _S from the throttle valve switch 17 (see FIG. 8 C), which is at low level "L" at other times, is input to the AND circuit 39, and the logical product of the two is taken, and the signals S _H and S When _S is both high level "H", that is, the signal S M becomes high level "H" in the high load and high rotation range, and becomes low level "L" in other partial load ranges and low and medium speed rotation _ranges .
(See Figure 8 D) is obtained.

The switching circuit 37 outputs the signal S _R to the AND circuit 40 when the signal S _M is at a low level "L", and outputs the signal S _R to the air-fuel ratio control circuit 41 when the signal S _M is at a high level "H". The circuit is configured in

Therefore, first, ignition timing control in the partial load range and low to medium speed rotation range will be explained.

The signal S _R from the switching circuit 37 is inverted by an inverting circuit built into one input stage of the AND circuit 40 as shown in _FIG . The logical AND is taken, and the 7th
A timing signal S _T as shown in Figure N is obtained.

In this timing signal _ST , the rising point of each pulse indicates the corrected ignition timing, and if knocking does not occur as shown in the figure, the power distributor 24 as the ignition timing determining means determines the engine rotation speed. This coincides with the basic ignition timing (the time of the rise of the pulse of point signal _SF ) determined by the suction negative pressure. Further, when knocking occurs, the ignition timing is delayed as shown by θ ₁ to _{θ 5} from the basic ignition timing depending on the frequency of knocking.

The AND circuit 40 constitutes ignition timing control means for correcting and controlling the ignition timing determined by the ignition timing determining means in accordance with the detection signal of the knocking detection means.

The igniter 22 performs switching at each rising edge of the pulse of the timing signal S _T (see FIG. 7), controls the energization of the ignition coil 23, and controls the ignition coil 23 through the power distributor 24 and the spark plug 25. The ignition is performed in such a way that knocking occurs.

In this way, the knocking control device according to the present invention delays the ignition timing in accordance with the frequency of knocking when the engine is operating in the partial load range and low-to-medium speed range to improve fuel efficiency and output characteristics. Feedback control of the ignition timing is performed so that the slight knocking condition improves, and if knocking does not occur, ignition is performed in accordance with the basic ignition timing determined by the ignition timing determining means. It's becoming like that.

Next, in response to the high-level “H” signal S _M output from the AND circuit 39 in the high-load, high-speed range, the switching circuit 37 transfers the signal S _R to the air-fuel ratio control circuit 41.
The air-fuel ratio control when the output is output to will be explained.

In this embodiment, the air-fuel ratio is varied to the rich side (larger amount of fuel) depending on the frequency of knocking, and for this purpose the fuel of the electronically controlled fuel injection system (EGI) is varied depending on the frequency of knocking. He is trying to control the injection time by the injection valve 21 to be long.

The air-fuel ratio control circuit 41 receives various sensor signals to be described later, a point signal S _F from the power distributor 24, and a detection signal from the O ₂ sensor 19 that the switch 43 outputs in response to a signal S _S from the throttle valve switch 17.
The injection time of the fuel injection valve 21 is determined according to V ₀ or the reference voltage V _R from the reference voltage circuit 42, and the injection time is determined by the signal S _R from the switching circuit 37 that corresponds to the frequency of occurrence of knocking. The fuel injection valve 21 is driven by the signal S _X obtained as a result of the correction, and the air-fuel ratio is changed to the rich side.

This air-fuel ratio control circuit 41 will be explained with reference to FIG. 9. First, the frequency conversion circuit 44 divides the point signal S _F (see FIG. 10 A) from the power distributor 24 by 1/2. The period is 1/N (N is the engine rotation speed at that time, that is, the number of revolutions per second.
rps) into a signal S _E (see Figure 10 b).

Each rising edge of this signal S _E becomes a starting point for fuel injection.

The reference pulse generation circuit 45 is composed of, for example, an integrator and a multivibrator, and the integrator starts integrating a predetermined input current at the falling edge of the signal S _E , and starts integrating the current air flow at the rising edge of the signal S _E. Inverse integration, or discharge, is started with a time constant determined according to the magnitude of the output signal S _AF of the sensor 9 (the smaller the signal S _AF , that is, the larger the intake air flow rate, the larger the time constant). Therefore, the output signal S _G of this integrator becomes as shown in FIG. 10C.

On the other hand, a multivibrator (bistable multivibrator) that constitutes the reference pulse forming circuit 45
is triggered at the rising edge of the signal S _E and is triggered again when the integrator signal S _G becomes zero as a result of discharge, and the output of this multivibrator, that is, the reference pulse forming circuit 45
The output pulse signal S _J of is as shown in FIG. 10D.

In addition, in this case, the rise of the signal S _E is
It coincides with the fuel injection start point, and its pulse width increases in proportion to the intake air flow rate per revolution at all engine speeds.

This is because there is an inversely proportional relationship between the intake air flow rate per rotation and the output signal S _AF of the air flow sensor 9, as shown in FIG. 11, and the signal S _AF
This is because the smaller the integrator is, that is, the larger the intake air flow rate per rotation, the larger the discharge time constant of the integrator becomes. Figure 12 shows the engine rotation speed N (N ₂ >
₁ ) and the relationship between the output signal S _G of the integrator and the output pulse signal S _J of the reference pulse forming circuit 45 when the intake air amount changes, and the broken line is the same as the solid line. This is the case when the amount of intake air is larger than in the case of

Then, the pulse signal S _J indicating the reference injection amount determined in this manner is input to the first correction pulse forming circuit 46 .

The first correction pulse forming circuit 46 includes a starting correction amount to facilitate engine starting, a warm-up correction amount until the cooling water temperature reaches a predetermined temperature after engine starting,
Calculate the total correction amount, such as the high load correction amount during high load, the voltage correction amount when the battery voltage drops, and the feedback correction amount due to air-fuel ratio feedback control, and output a pulse signal S _C with a pulse width corresponding to the total correction amount. do.

That is, the first correction pulse forming circuit 46 is constituted by, for example, a multivibrator, and is first triggered by the falling edge of the pulse signal _SJ .

Then, when the starter switch 47 is turned on, a signal S _A is output from the starting increase correction circuit 48 , a signal S W is output from the warm-up increase correction circuit 49 in response to the detection signal of the water temperature sensor 18 , and a signal S _W is output from the warm-up increase correction circuit 49 in response to the detection signal of the water temperature sensor 18 . Feedback signal Sλ, etc. output from air-fuel ratio feedback control (λ-control) circuit 51 based on on/off signal S _S , battery voltage signal V _B from battery 50, and detection signal V ₀ from O ₂ sensor 19 After the elapse of the time calculated by
Outputs _C.

This pulse signal S _C is further input to a second correction pulse forming circuit 53 for knocking correction.

In addition, when the load is high, the throttle valve switch 1
The switch 43 detects the detection signal of the _O2 sensor 19 by the high level "H" signal S _S output from the switch 43.
V ₀ is cut off and the reference voltage V _R from the reference voltage circuit 42 is output to the air-fuel ratio feedback control circuit 51, at which point the feedback control system using the O ₂ sensor 19 is stopped.

The second correction pulse forming circuit 53 is also constituted by a multivibrator or the like, and is a pulse signal S output from the first correction pulse forming circuit 46.
Triggered on the falling edge of _C. And switching circuit 3
The pulse width is changed according to the frequency of knocking as shown in FIG. 10 by the signal S _R (see FIG. Pulse signal S _N
get.

Note that the switching circuit 37 is closed except during high speed and high load.
The output signal S _R of the comparator 36 is determined by the signal S _M of the AND circuit 39 in the AND circuit of the ignition timing control system shown in FIG.
At that point, a ground level signal is input to the second correction pulse forming circuit 53, and the pulse width of the pulse signal S _N becomes zero, and the air-fuel ratio correction due to knocking is no longer possible. I won't do it.

Then, the logical sum circuit 52 takes the logical sum of these pulse signals S _J , S _C , and _SN and obtains the tenth signal.
A pulse signal S _I as shown in the figure is obtained.

Therefore, the rising edge of this signal S _I coincides with the starting point of fuel injection, and its pulse width determines the final fuel injection amount.

After this pulse signal S _I is amplified by the amplifier 54, the amplified pulse signal S _X drives the fuel injection valve 21 to open only for a period corresponding to the pulse width.

Therefore, when knocking occurs, the amount of fuel injected becomes larger than when knocking does not occur, depending on the frequency of knocking, and the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio.

In this way, the knocking control device of the above embodiment shifts the air-fuel ratio to the rich side depending on the frequency of knocking when knocking occurs when the engine is operating in a high-load, high-speed range, thereby preventing the knocking from occurring. Feedback control of the air-fuel ratio is also being carried out to suppress the air-fuel ratio.

In the above embodiment, the driving time of the fuel injection valve 21 is controlled to be longer depending on the frequency of occurrence of knocking, and the air-fuel ratio is shifted to the rich side. When the present invention is applied to a vehicle that performs air-fuel ratio control, the pulse width of the on/off signal of the solenoid valve that controls the air-fuel ratio by varying the pressure of the air bleed part is changed in the same manner as in the above embodiment. The control may be performed in accordance with the output pulse signal of the air-fuel ratio control circuit.

As explained above, the knocking control device for a turbocharged engine according to the present invention corrects the ignition timing to the retarded side when knocking is detected in engine operating ranges other than high-speed, high-load ranges, and controls the ignition timing to retard the knocking in other operating ranges. When this is detected, the air-fuel ratio is corrected to the rich side, so the occurrence of knocking can be effectively suppressed without causing a decrease in output or deterioration of fuel efficiency in the entire operating range of the engine, and always prevents damage to the engine. It is possible to control the knocking state to a slight knocking state without causing a risk of occurrence, and to fully demonstrate the performance of the turbocharger, thereby improving fuel efficiency and output characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between ignition timing and knocking strength. FIG. 2 is a diagram showing the air-fuel ratio versus ignition timing characteristics of the knocking limit and MBT (ignition timing that can generate maximum torque). FIG. 3 is a diagram showing the knocking limit and MBT's engine rotational speed/ignition timing characteristics together with the supercharging rate.
FIG. 4 is a diagram showing the relationship between ignition timing and shaft torque. FIG. 5 is a system configuration diagram of a turbocharger-equipped engine equipped with a knocking control device according to the present invention. FIG. 6 is a block diagram of a control unit showing an embodiment of the invention. FIGS. 7A to 7E are signal waveform diagrams of various parts for explaining the operation of FIG. 7. FIGS. 8A to 8D are diagrams for explaining the operation of the switching circuit in FIG. 7. FIG. 9 is a block diagram of the air-fuel ratio control circuit in FIG. 7. Figure 10 I to I are as follows:
10 is a signal waveform diagram of each part for explaining the operation of FIG. 9. FIG. FIG. 11 is a diagram showing the output characteristics of the air flow sensor. FIG. 12 is an explanatory diagram for explaining the operation of the reference pulse forming circuit in FIG. 9. 1...engine, 2...turbocharger, 9
... Air flow sensor, 10 ... Throttle valve, 16 ... Control unit, 17 ... Throttle valve switch, 18 ... Water temperature sensor,
19...O ₂ sensor, 20... Vibration sensor, 21
...Fuel injection valve, 22...Igniter, 23...
Ignition coil, 24...Distributor, 25...
...Spark plug, 37...Switching circuit, 41...Air-fuel ratio control circuit.

Claims (1)

[Claims] 1. In an engine equipped with a turbocharger that supercharges intake air, knocking detection means detects knocking of the engine, and ignition timing control means corrects and controls ignition timing to the retarded side in response to a detection signal of the knocking detection means. , an air-fuel ratio control means for correcting and controlling the air-fuel ratio to the rich side in response to a detection signal from the knocking detection means; a means for detecting the operating state of the engine; A knocking control device characterized in that the control means is provided with switching means for switching and outputting the detection signal of the knocking detection means to the ignition timing control means in other operating ranges.