JPH0647987B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition timing control device that enhances drivability by performing MBT control while suppressing knocking of an internal combustion engine such as an automobile.

(Prior Art) The ignition timing of an internal combustion engine must be determined according to the state of the engine so that the engine operates optimally. It is generally known that it is best to ignite in the vicinity of the minimum advance angle at the time of maximum torque, that is, so-called MBT (Minimum advance for Best Torque), considering the efficiency and fuel efficiency of the engine. So-called MBT control is performed.

However, in a certain engine state, knocking occurs when the ignition timing is advanced, and stable engine operation cannot be performed. For example, MBT at low speed and low load
The knocking limit has come earlier. Further, the knocking limit is easily affected by atmospheric conditions such as temperature and humidity.

Therefore, a system has been developed in which the so-called knocking control in which the ignition timing is controlled according to the presence or absence of knocking is used together with the MBT control. For example, such a system is described in JP-A-58-82074. There is a device.

In this device, the pressure in the combustion chamber (hereinafter referred to as cylinder pressure)
Is detected, and the ignition timing is MBT controlled so that the crank angle θpmax at which the pressure becomes maximum (hereinafter referred to as the combustion peak position) comes to a predetermined position at which the torque generated by the engine becomes maximum. At the same time, knocking is detected through a signal processing circuit using a signal for detecting the in-cylinder pressure, and when the knocking level exceeds a predetermined value, the ignition timing is retarded to avoid knocking with priority over MBT control. This is intended to increase the torque generated by the engine as much as possible while suppressing knocking and improve the driving performance.

(Problems to be Solved by the Invention) However, in such a conventional ignition timing control device for an internal combustion engine, the ignition timing is controlled based on the output of the knock detection means regardless of abnormality of the knock detection means. Therefore, for example, when the knock detection means fails, the ignition timing is controlled on the basis of the knock level that is erroneously detected. Therefore, the ignition timing may be retarded more than necessary despite the low knocking level, or the ignition timing may be advanced despite the high knocking level. As a result, the combustion efficiency of the engine is deteriorated and the engine itself is broken, resulting in a decrease in operating performance.

On the other hand, in order to prevent the above-mentioned harmful effects, for example, it is conceivable to newly add an abnormality determination function of the knock detection means, and to provide an equivalent knock detection means so that knock detection can be performed at the time of abnormality. It may be complicated and costly.

(Object of the Invention) Therefore, the present invention prevents the deterioration of the ignition timing control based on the erroneous determination of knocking by making it possible to perform the above abnormality determination and knock detection with a simple improvement of the existing function to operate the engine. The purpose is to improve performance.

(Structure of the Invention) As shown in the basic conceptual diagram of the ignition timing control device for an internal combustion engine according to the present invention, a pressure detecting means a for detecting combustion pressure of the engine and an operation for detecting an operating state of the engine are provided. The state detecting means b, the first knock level detecting means c for detecting the knocking level of the engine based on the output of the pressure detecting means a and the output of the first knock level detecting means c are compared with a predetermined reference value, and the means are compared. The abnormality determining means d for determining the abnormality of c, the peak position detecting means e for detecting the combustion peak position where the combustion pressure becomes maximum based on the output of the pressure detecting means a, and the combustion peak position for maximizing the torque generated by the engine. The first calculation means f for calculating the combustion correction amount for correcting the ignition timing so that the ignition timing is adjusted to the predetermined position, and the combustion peak position when the first knock level detection means c are determined to be abnormal. Second to detect knocking level by comparing with a fixed reference value
When the knock level detecting means g and the first knock level detecting means c are normal, the knock correction amount for correcting the ignition timing is calculated based on the output of the means c so that the knocking level becomes a predetermined value. If it is determined that there is a second knock level detection means g, the second calculation means h for calculating the knock correction amount based on the output of the second knock level detection means g, and the basic ignition timing is set based on the operating state, and the combustion correction is performed. Ignition timing setting means i for making correction according to the amount and knock correction amount
And ignition means j that ignites the air-fuel mixture based on the output of the ignition timing setting means i, and prevents deterioration of ignition timing control due to erroneous determination of knocking.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 9 are views showing an embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an in-cylinder pressure sensor (pressure detecting means), and the in-cylinder pressure sensor 1 converts the combustion pressure in the cylinder into an electric charge by a piezoelectric element and outputs an electric charge output S ₁ . Specifically, the in-cylinder pressure sensor 1 is screwed to the cylinder head 2 and formed as a washer for the ignition plug 3, as shown in detail in FIGS. 3 (A) and 3 (B).
The ignition plug 3 is pressed and fixed in the outer recess of the cylinder head 2 by the tightening portion 3a of the ignition plug 3.

The sensor output S ₁ is input to the charge amplifier 4,
The charge amplifier 4 has operational amplifiers OP1 and OP2, resistors R1 to R8, and a capacitor 1 as shown in detail in FIG.
And a so-called charge-voltage conversion amplifier composed of the diodes D1 to D3, and the sensor output S ₁ is converted into the voltage signal S ₂
Signal processing circuit (first knock level detecting means)
5 and control unit 6.

The integration interval signal Sk is further input from the control unit 6 to the signal processing circuit 5, and the signal processing circuit 5 uses a band pass filter (B) as shown in detail in FIG.
PF) 7, rectifier 8 and integrator 9.
The band pass filter 7 passes only the signal in the frequency band (for example, 5 KHz to 20 KHz) corresponding to knocking vibration in the signal S ₂ , and outputs it as the signal S ₃ to the rectifier 8, and the rectifier 8 full-wave rectifies the signal S _3. (Half-wave rectification may be used) and the rectified signal S ₄ is output to the integrator 9. The integration interval signal Sk is input to the integrator 9 for a predetermined period, and the integrator 9 integrates the rectified signal S ₄ in response to the input of the integration signal Sk to obtain the combustion vibration energy during knocking and when not knocking. The integrated values K and B corresponding to the related physical quantities are obtained and output to the control unit 6.

Referring again to FIG. 2, the control unit 6 is further supplied with a signal from the operating condition detecting means 11, and the operating condition detecting means 11 is composed of a crank angle sensor 12 and an air flow meter 13. The crank angle sensor 12 detects the compression top dead center (TD) of each cylinder at every explosion interval (crank angle 120 ° for 6 cylinder engine, 180 ° for 4 cylinder engine).
A reference position signal Ca which becomes a pulse of [H] level at a predetermined position before C), for example, BTDC 70 ° is output, and [H] is output for each unit angle (for example, 2 °) of the crank angle.
A unit signal C ₁ that becomes a level pulse is output. In addition,
The engine speed can be known by counting the pulses of the signal Ca. Further, the air flow meter 13 detects the intake air amount Qa of the engine and outputs an analog signal Sa.

The control unit 6 has functions as abnormality determining means, peak position detecting means, second knock level detecting means, first calculating means, second calculating means, and ignition timing setting means, and CPU 21, ROM 22, RAM 23, A / D. It is composed of a converter 24 and an I / O port 25. CPU21 is RO
According to the program written in M22, it takes in the required external data from I / O port 25, and R
While exchanging data with the AM23, the processing values necessary for knock determination and ignition timing control are calculated and processed.
The data processed as necessary is output to the I / O port 25. The I / O port 25 receives signals from the operating state detecting means 11, the charge amplifier 4, and the signal processing circuit 5, and the I / O port 25 outputs an integration interval signal S _K and an ignition signal Sp. .

The output range of the integration interval signal S _{K is} a range in which knocking is expected to occur (for example, ATDC 0 ° to 40 °) and a region in which knocking is not expected to occur at all (eg, BTDC 50 ° to 10 °). Set to two. The timing for determining these sections is determined using the pulse signals Ca and C ₁ of the crank angle described above. A / D converter
The A / D converter 24 A / D converts an external signal input to the I / O port 25 in accordance with an instruction from the CPU 21. Also, RMO22 is CP
A calculation program in U21 is stored, and the RAM 23 stores data used for calculation in the form of a map or the like. The ignition signal Sp is input to the ignition means 26, and the ignition means 26 is composed of an ignition coil, a distributor, an ignition plug, etc., and generates a high voltage based on the ignition signal Sp to ignite the air-fuel mixture.

The use will now be described, but first the basic principles of the invention will be described.

In general, the knocking phenomenon refers to abnormal combustion due to early ignition of unburned air-fuel mixture in the cylinder, which is caused by the pressure in the cylinder having multiple natural vibrations determined by the cylinder size (especially bore diameter) and combustion gas temperature. Appears as damped vibration. This pressure vibration is transmitted to the air through the cylinder wall, the cylinder block, etc., and an unpleasant high-frequency sound that reaches the human sense of hearing is what is called a knocking sound.

FIG. 6 shows the relationship between the crank angle (hereinafter referred to as the combustion peak position) θpmax when the in-cylinder pressure becomes maximum and the knocking level by the sensitivity evaluation. This is one
This is an example of an engine of a model, but other models also show a similar tendency. As is clear from FIG. 6, there is a large difference between θpmax when knocking occurs and when it does not knock. Therefore, by detecting this θpmax, it is possible to detect a knocking level that is faithful to human sensitivity evaluation.

Further, as shown in FIG. 7 which shows the relationship between θpmax and ignition timing, it is possible to change the position of θpmax by modifying the ignition timing. Therefore, it is possible to suppress knocking by detecting θpmax and correcting the ignition timing based on the difference from θpmax that provides a desired knocking level. This represents the basic principle of the present invention that can suppress the knocking by utilizing the detection control information θpmax in MBT control of controlling the theta _pmax to the target value.

Next, the ignition timing control based on the above basic principle will be described according to the program shown in FIG.

When this program detects the [H] pulse of the reference position signal Ca of the crank angle sensor 12 as shown in FIG. 9 (a), it starts counting the [H] pulse of the unit signal C ₁ ,
The crank angle θ is counted a predetermined number of times and a predetermined value (for example,
Start at the point where it reached BTDC 40 °). On the other hand, the output signal S ₂ of the charge amplifier 4 changes in proportion to the in-cylinder pressure as shown in FIG. 9 (b), and contains a unique vibration component when knocking occurs. This voltage signal S ₂ is a signal S ₃ in which only the vibration component in the knocking frequency band is extracted by the bandpass filter 7 as shown in FIG. Then
Signal S ₃ is a signal S ₄ is rectified by a rectifier 8 as shown in FIG. (D).

Now, assuming that the program shown in Fig. 8 starts, P
_{At 1} , the integrator 9 is set (the integration interval signal Sk is output) and the integration of the rectified output S ₄ is started. Then, at P ₂ , the crank angle θ is compared with θ ₂ (for example, θ ₂ = BTDC 5 °),
When θ <θ ₂ , stand by in this step P ₂ and θ ≧ θ ₂
Then, in P ₃ , the integrated value at this time is A / D converted. Then, at P ₄ , this A / D converted value B is stored in a predetermined area of the RAM 23, and at P ₅ , the integrator 9 is reset (the output of the integration interval signal Sk is stopped) and the process proceeds to P ₆ . The integrated value in the integration section is a physical quantity B corresponding to combustion vibration energy when the engine is not knocked, as shown in FIG. 9 (e).

At P ₆ , the crank angle θ is set to θ ₃ (for example, θ ₃ = TDC).
Compare with. When θ <θ ₃ holds, when θ ≧ θ ₃ , A / D conversion of the voltage signal S ₂ corresponding to the in-cylinder pressure is started at P ₇ . Next, at P ₈ , the crank angle θ is compared with θ ₅ (for example, θ ₅ = ATDC10 °), and when θ = θ ₅ , the integrator 9 is set at P ₉ and the integration of the rectified output S ₄ is restarted. Proceed to P ₁₀ , and if θ ≠ θ ₅ , proceed directly to P ₁₀ . At P ₁₀ , the signal S corresponding to the crank angle θ at that time
Wait ₂ of the A / D conversion processing is completed, the A / D conversion value of the signal S ₂ at that time as well as far RAM23 at P ₁₁ When finished, the crank angle θ similarly the time in P ₁₂ It is stored in the RAM 23. Next, at P ₁₃ , the crank angle θ
Is compared with θ ₄ (for example, θ ₄ = ATDC 40 °), and θ <
When the theta ₄ back to _{P 7} repeats the flow until _P 7 to P _13. Then, when θ ≧ θ ₄ , the process proceeds to P ₁₄ . Therefore, between TDC and ATDC 40 °, the crank angle θ and the A / D conversion value of the signal S ₂ are stored in the RAM 23 in a one-to-one correspondence as shown in FIG. 9 (f). The stored contents include θpmax and the maximum value Pmax of the in-cylinder pressure at that time, as shown in FIG.

Next, at P ₁₄ , the crank angle θ is set (for example, θ ₆ = ATD
Compared with C45 °), when θ <θ ₆ stands by and when θ ≧ θ ₆ , the integrated value at this time is A / D converted at P ₁₅ . P ₁₇
Then, this A / D conversion value K is stored in the RAM 23 as a physical quantity K corresponding to combustion vibration energy at the time of knocking.

Next, at P _17, it is determined whether the knock signal is abnormal. The knock signal corresponds to the A / D conversion values K and B of the previously calculated integral value or those obtained by performing some calculation.
The abnormality is judged by comparing such an actual knock signal with a table lookup of the allowable limit value of the knock signal which is recognized as normal under the operating conditions at that time, from the engine speed, the intake air amount, etc. . Such an abnormality determination can be performed at low cost by previously creating the allowable limit value of the knock signal in a data table format over a wide range of operating conditions and by creating a program by so-called software. Determine the abnormality determination result of the P ₁₈ in the knock signal, when the abnormal process proceeds to P _19, the process proceeds to P ₂₀ and if not abnormal. Hereinafter, cases will be described according to the presence or absence of an abnormality in the knock signal.

[I] When it is determined that the knock signal is abnormal: At P ₁₉ , the crank angle θpmax at which the in-cylinder pressure becomes maximum is detected from the A / D conversion value of the voltage signal S ₂ stored in the RAM 23. As described above, since the θpmax and the knock level have a good correlation, the knock level is determined based on this value. Therefore, first, at P ₂₁ , the target value θ _{k of} θ pmax that becomes a predetermined knock level under the operating condition at that time
Table lookup is performed, and θ pmax is compared with this θ _k at P ₂₂ . ? pmax ≧ theta _k control for knock level knock suppression in P ₂₃ was determined to be equal to or greater than the predetermined value when the (hereinafter referred to as a knock control) is performed.

Here, the following is performed as an example of knock control.

When the knock is detected, the ignition timing correction amount m is calculated according to the knock level, and the sum M ′ + m of the previous ignition timing correction amount M ′ and the present correction amount m is calculated as the current ignition timing correction amount M.
(Corresponding to knock correction amount) M = M '+ m. The basic ignition timing (advanced in the figure) N is calculated from the data table shown in FIG. 10 based on the operating conditions such as the engine speed and the intake air amount. When the timing (N + M) is determined and the timing is reached, the ignition signal Sp is output to output the ignition means.
26 ignites the mixture. Therefore, the ignition timing is retarded so as to suppress the knock according to the knock level.

On the other hand, when? Pmax <theta _k-cylinder pressure from the A / D conversion value of the cylinder pressure knock level is stored in the RAM23 in P ₂₄ was determined to be less than the predetermined value when in the step P ₂₂ is maximized The crank angle θpmax is calculated and the MBT control is performed.

Here, the following is performed as an example of the MBT control.

While calculating the average value of the latest predetermined number of times θpmax,
It is compared with a target value, and the ignition timing correction amount m is calculated according to the result. The subsequent process is similar to the knock control described above, and the sum of these m and the previous correction amount M is obtained as the ignition timing correction amount M {M = (M '+ m)} (corresponding to the combustion correction amount). The final ignition timing (N + M) is obtained from this M and the basic ignition timing N to control the ignition timing. As a result, the ignition timing is controlled so as to maximize the generated torque.

In this way, when the knock signal is abnormal, that is, even if the original knock detecting means fails, the knock is detected based on θpmax at that time, and the MBT control can be performed within an appropriate knocking level range. . That is, it is possible to prevent the device from becoming complicated and prevent the ignition timing control from deteriorating at a low cost based on an erroneous determination of knocking. As a result, it is possible to avoid the inconvenience such as the deterioration of the combustion efficiency of the engine and the failure of the engine itself, which is pointed out in the conventional example, and it is possible to improve the fuel consumption and the driving performance.

[II] When it is determined that the knock signal is normal First, at P ₂₀ , a knock level index (knock parameter)
As a function f (K, B of integral values K and B corresponding to physical quantities related to combustion vibration energy during knocking and non-knocking
B) is calculated. As the function f (K, B), for example, K
And the ratio (K / B) of B is calculated, and this is used as a knock parameter. Next, at P ₂₅ , the target value S of f (K, B) that gives a predetermined knock level under the operating conditions at that time
L is looked up from the data table stored in the ROM ₂₂ , and the knock parameter (K / B) is compared with this target value SL at P ₂₆ . When K / B ≧ SL, it is determined that the knock level is equal to or higher than a predetermined value, and the knock control similar to that described above is performed at P ₂₃ . When K / B <SL, it is determined that the knock level is less than the predetermined value, and the same processing as in step P ₁₉ is performed in P ₂₇ to detect θpmax,
MBT control is performed at P ₂₄ .

As described above, when the knock signal is normal, the MBT control is performed while suppressing the knock, and the original control performance by both of them is effectively exhibited.

In this embodiment, K is used as the knock detection parameter.
Although / B is used, it is not limited to this. For example,
It is known that knocking can be detected by only K or by applying a predetermined calculation to K.

(Effects) According to the present invention, it is possible to avoid the complexity of the device and appropriately determine the abnormality of the knock signal at a low cost to prevent the deterioration of the ignition timing control based on the erroneous judgment of the knocking, and the deterioration of the combustion efficiency. It is possible to improve fuel efficiency and driving performance by avoiding the problem of causing engine or engine failure.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 9 are diagrams showing an embodiment of the present invention, and FIG. 2 is a block configuration diagram thereof.
3 (A) is a sectional view showing the mounting state of the cylinder pressure sensor, FIG. 3 (B) is a plan view of only the cylinder pressure sensor, and FIG. 4 is a detailed circuit diagram of the charge amplifier. FIG. 6 is a detailed block diagram of the signal processing circuit, FIG. 6 is a diagram showing the relation between θpmax and knock level, FIG. 7 is a diagram showing the relation between θpmax and ignition timing, and FIG. 9A to 9F are flowcharts showing a program for ignition timing control, and FIGS. 9A to 9F are diagrams showing signal waveforms of respective parts. 1 ... In-cylinder pressure sensor (pressure detection means), 5 ... Signal processing circuit (first knock level detection means), 6 ... Control unit (abnormality determination means, peak position detection means, second knock level detection means, second 1 calculating means, 2nd calculating means, ignition timing setting means), 11 ... Operating state detecting means, 26 ... Ignition means.

Claims (1)

[Claims] 1. A) pressure detecting means for detecting combustion pressure of the engine, b) operating state detecting means for detecting operating state of the engine, and c) knocking level of the engine based on output of the pressure detecting means. A first knock level detecting means for: d) an abnormality determining means for comparing the output of the first knock level detecting means with a predetermined reference value to determine an abnormality of the means; and e) a combustion based on the output of the pressure detecting means. Peak position detecting means for detecting a combustion peak position where the pressure becomes maximum; and f) first calculating a combustion correction amount for correcting the ignition timing so that the combustion peak position becomes a predetermined position where the torque generated by the engine is maximized. And a second knock level detecting means for detecting a knocking level by comparing the combustion peak position with a predetermined reference value when the first knock level detecting means is determined to be abnormal. H) When the first knock level detecting means is normal, a knock correction amount for correcting the ignition timing is calculated based on the output of the means so that the knocking level becomes a predetermined value, and when it is determined that the knocking level is abnormal. Second computing means for computing the knock correction amount based on the output of the second knock level detecting means; i) setting a basic ignition timing based on the operating state, and using this as the combustion correction amount and the knock correction amount. An ignition timing control device for an internal combustion engine, comprising: an ignition timing setting means for making a corresponding correction; and j) an ignition means for igniting an air-fuel mixture based on the output of the ignition timing setting means.