JPS6380075A - Ignition timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent occurrence of knocking to aim at enhancing the economy of fuel consumption and the performance of an engine, by providing a control circuit for changing a maximum value limiting the spark retarding amount in accordance with a variation in the air-fuel ratio which is controlled by an air-fuel ratio control means. CONSTITUTION:An air-flowmeter 10 is disposed downstream of an air cleaner. The air flowmeter 10, an intake-air temperature sensor 12, a throttle sensor 24A, a knocking sensor 36, a cylinder discriminating sensor 46, a rotating angle sensor 48, a cooling water temperature sensor and an exhaust gas temperature sensor 50 are connected to a control circuit 45. An ignitor 44 and a fuel injection valve 26 are controlled in accordance with a control signal delivered from the control circuit 45. When it is discriminated that temperature of exhaust gas is below a predetermined value, a maximum value for limiting the spark retarding amount is increased by a constant value. Further, the compensation spark retarding amount is limited to such a maximum value so that a value which obtained by subtracting the compensating spark retarding amount from a basic spark advancing amount is used as an executive spark advance. With this arrangement, it is possible to prevent occurrence of knocking, thereby it is possible to aim at preventing an engine from being damaged, and at enhancing the economy of fuel consumption and performance of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition timing control device for an internal combustion engine, and particularly to an ignition timing control device for an internal combustion engine equipped with an air-fuel ratio control means for controlling the air-fuel ratio according to the operating state of the engine. The ignition timing side that controls knocking? B
Regarding equipment.

(Prior art) Conventionally, ignition timing control detects whether knocking, which is air column vibration that occurs due to self-ignition of end gas in a cylinder, has occurred and controls ignition timing to control knocking. A device is known. In this ignition timing control device, a predetermined crank angle range (for example, 10' CA ATDC to 50' CA A
It is determined that knocking has occurred by comparing the peak value a of engine vibration at TDC) with the determination level kb obtained by multiplying the level of engine vibration not caused by knocking, that is, the background level b, by a constant k (constant value). I am trying to determine whether or not. Here, the peak value a is determined by installing a knocking sensor consisting of a piezoelectric element, a magnetostrictive element, etc. that converts engine vibration into an electrical signal on the shilling block, and determining the band in which signals in the frequency band specific to knocking (6 to 8 kHz) can pass. It is obtained by inputting an electrical signal to a peak hold circuit via a pass filter and holding the peak value within a predetermined crank angle range. Further, the determination level kb is obtained by multiplying a value (background level) obtained by integrating an electrical signal corresponding to engine vibration not caused by knocking by an integrating circuit by a constant k. Then, when it is determined that knocking has occurred, the ignition timing is retarded by a predetermined amount, and when it is determined that no knocking has occurred, the ignition timing is advanced by a retard amount, and this retard amount is calculated. By correcting the basic ignition advance angle, the maximum advance angle at which knocking does not occur (knocking limit)
The ignition timing is controlled accordingly.

In addition, in order to prevent the ignition timing from being over-retarded due to an abnormality occurring in a knocking sensor, etc., where it is incorrectly determined that knocking has occurred even when no knocking has occurred, the retardation amount is set to a predetermined maximum. The ignition timing is controlled so as not to exceed this value.

Further, such an internal combustion engine is provided with an air-fuel ratio control means for controlling the air-fuel ratio according to the operating state of the engine. For example, this air-fuel ratio control means controls the air-fuel ratio to the output air-fuel ratio (approximately 12.5) in an operating state where the exhaust gas temperature is below a predetermined value so that maximum output can be obtained, and when the exhaust temperature exceeds a predetermined value. In some cases, the air-fuel ratio is controlled to be richer (approximately 10) than the output air-fuel ratio in order to protect the exhaust system (for example, Japanese Patent Application Laid-open No. 56-81235). According to this method, when knocking occurs, the ignition The timing is retarded, and when the exhaust gas temperature rises above a predetermined value due to this retardation, the air-fuel ratio is made rich and the exhaust gas temperature is lowered. Additionally, when knocking is detected during air-fuel ratio lean control (in the example above, when the air-fuel ratio is being controlled to the output air-fuel ratio), the air-fuel ratio is controlled to be rich to control the rise in exhaust temperature. ing.

[Problem that the invention seeks to solve]

However, in the method of controlling the air-fuel ratio rich when the exhaust temperature exceeds a predetermined value, knocking is likely to occur because the air-fuel ratio is controlled lean until the exhaust temperature reaches the predetermined value. As shown in Figure (A), the amount of retardation is limited to the maximum value before the exhaust temperature reaches a predetermined value, and even if the amount of retardation is limited to the maximum value, it may not be possible to suppress the occurrence of knocking. There is a problem that there is a risk of damage to the engine. In addition, in the method of richly controlling the air-fuel ratio when knocking is detected, the knocking limit changes each time the air-fuel ratio is richly controlled, so the knocking level is kept constant and the ignition timing is adjusted to MBT (formerly
imus+ 5pank Advance for Be
5t Torque), and since the air-fuel ratio is controlled every time knocking occurs, air-fuel ratio feedback control based on exhaust temperature cannot be used effectively, making it impossible to expect performance improvement and deteriorating fuel efficiency. There is a problem.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ignition timing control device for an internal combustion engine that prevents damage to the engine due to knocking and improves performance and fuel efficiency. .

[Means for solving problems]

In order to achieve the above object, the present invention determines whether knocking has occurred in an internal combustion engine equipped with an air-fuel ratio control means that controls the air-fuel ratio according to the operating state of the engine, and determines that knocking has occurred. When the ignition timing occurs, the ignition timing is retarded, and when it is determined that knocking has not occurred, the ignition timing is advanced by calculating the retardation amount, and the retardation amount is adjusted so as not to exceed a predetermined maximum value. The ignition timing control device for an internal combustion engine that controls ignition timing by limiting the ignition timing is characterized in that the maximum value is changed in accordance with a change in the air-fuel ratio controlled by the air-fuel ratio control means.

[Effect]

According to the present invention, the ignition timing control device retards the ignition timing when it is determined that knocking has occurred, and advances the ignition timing when it is determined that knocking has not occurred. is calculated, and the ignition timing is controlled by limiting the retard amount so that it does not exceed a predetermined maximum value.

At this time, when the air-fuel ratio is changed by the air-fuel ratio control means, the maximum value for limiting the retard amount is changed. As a result, the above maximum value is changed according to the air-fuel ratio to perform optimal knock control, and even when the air-fuel ratio is changed, the occurrence of knocking is reduced when the retard amount is limited to the maximum value. be done.

Here, the air-fuel ratio (16~
(about 18), knocking tends to occur more easily as the air-fuel ratio becomes leaner, so when changing the air-fuel ratio at a richer side than the air-fuel ratio where the knocking margin becomes the minimum, When the air-fuel ratio is lean, it is preferable to increase the maximum value for limiting the amount of retardation than when the air-fuel ratio is rich.Also, it is preferable to increase the maximum value for limiting the amount of retardation when the air-fuel ratio is lean. When changing the air-fuel ratio, knocking tends to occur more easily as the air-fuel ratio becomes richer. When the air-fuel ratio is rich, it is preferable to make the maximum value for limiting the retard amount larger than when the air-fuel ratio is lean.

〔Effect of the invention〕

As explained above, according to the present invention, the maximum value for limiting the amount of retardation is changed according to the air-fuel ratio, so this maximum value can be increased during control at air-fuel ratios where knocking is likely to occur. This has the effect of preventing engine damage and improving fuel efficiency and performance by preventing the occurrence of knocking.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 schematically shows a supercharged six-cylinder spark ignition internal combustion engine equipped with an ignition timing control device and an air-fuel ratio control device to which the present invention is applicable. Air cleaner (
An air flow meter 10 is disposed downstream of the air flow meter (not shown). This air flow meter 10 detects the amount of intake air from a compensation plate 10A rotatably arranged in a damping chamber, a measuring plate IOB fixed to the compensation plate IOA, and a change in the opening of the measuring plate IOB. It is composed of a potentiometer IOC. An intake air temperature sensor 12 is arranged near the downstream side of the air flow meter 10. The air flow meter 10 is communicated with an intake boat 22 of the engine body 20 via an intake passage 14, a surge tank 16, and an intake manifold 18. A throttle valve 24 is arranged on the upstream side of the surge tank 16,
A potentiometer-type throttle sensor 24A for detecting the opening degree of the throttle valve is attached to the throttle valve 24, and a fuel injection valve 26 is arranged in the intake manifold 18 so as to protrude for each cylinder. The intake boat 22 is communicated with a combustion chamber 28 formed within the engine body 20 via the intake pulp 20A. This combustion chamber 28 includes an exhaust valve 20B, an exhaust boat 3
0, exhaust passage 3 via exhaust manifold 32
It is connected to 4.

A knocking sensor 36 made of a piezoelectric element, a magnetostrictive element, etc. is attached to the cylinder block of the engine body 20. Further, a cooling water temperature sensor 3B is attached to the engine body 20 so as to penetrate through the cylinder block and protrude into the water jacket. A spark plug 40 is attached to each cylinder so as to protrude into the combustion chamber 28 of the engine body 20, and the spark plug 40 is connected to a control circuit 45 including a microcomputer via a distributor 42 and an igniter 44. It is connected to the. Attached to the distributor 42 are a cylinder discrimination sensor 46 and a rotation angle sensor 48, each of which includes a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. The cylinder discrimination sensor 46 has 7
A cylinder discrimination signal is output every 20° CA, and the rotation angle sensor 4
8 outputs a rotation angle signal every 30'' CA.

A thermistor-type exhaust gas temperature sensor 50 for detecting exhaust gas temperature is attached to the exhaust manifold 32. Further, the exhaust passage 34 includes a bypass passage 5.
2 are connected to each other, and a waste gate valve 54 is disposed within this bypass passage 52. This wastegate valve 54 is connected to the actuator 54A via a link mechanism, and is opened and closed via the link mechanism by air pressure supplied to the actuator 54A via the intake passage 14 and the pressure conduit 54B.

The supercharger 56 is arranged such that the compressor 56A is located in the intake passage 14 and the turbine 56B connected to the compressor 56A is located in the exhaust passage 34.

The air flow meter 10, intake temperature sensor 12, throttle sensor 24A1, knocking sensor 36, cylinder discrimination sensor 46, rotation angle sensor 48, cooling water temperature sensor 38, and exhaust temperature sensor 50 are connected to the control circuit 45 so as to input signals. Further, the igniter 44 and the fuel injection valve 26 are connected so as to be controlled by a control signal output from a control circuit 45.

Control circuit 45 configured including a microcomputer
is a random access memory (RA) as shown in Figure 4.
M) 58, read only memory (ROM) 60. A microprocessing unit (MPU) 62, a first output port 4, a second input/output port 6, a first output port 8, a second output port 0, and a data bus or computer that connects them. There are 72 buses such as troll buses. The first input/output capotro 4 is analog-digital (
airflow meter 1 via A/D) converter 74, multiplexer 76 and buffers 78A, 78B, 78G, respectively.
0. It is connected to the intake air temperature sensor 12 and the cooling water temperature sensor 38. Further, the first input/output capotro 4 is connected to supply a control signal to the A/D converter 74 and multiplexer 76. The second input/output capotro 6 is connected to a cylinder discrimination sensor 46 and a rotation angle sensor 48 via a waveform shaping circuit 80, and is also connected to a knocking sensor 36 via an input circuit 82, and is connected to the knocking sensor 36 via an input circuit 82. It is connected to the exhaust gas temperature sensor 50 via an input circuit 84 having an input device, and is also directly connected to the throttle sensor 24A.

As shown in FIG. 5, the input circuit 82 includes a knock gate circuit 82A whose negative end is connected to the knock sensor 36.
and a peak hold circuit 82B, an integrating circuit 82E connected in parallel to this series circuit, a multiplexer 82C connected to the series circuit and the integrating circuit 82E, and a peak hold circuit 82B connected to the multiplexer 82C.
/D converter 82D. And knock gate circuit 82A1 multiplexer 82C and A/D
Converter 82D is connected to be controlled by a control signal from second input/output capotro 6.

The first output port door 8 is connected to the igniter 44 via a drive circuit 86, and the second output port door 0 is connected to the fuel injection valve 26 via a drive circuit 88. Note that 90 is a clock and 92 is a timer. Above ROM6
0 stores in advance a control routine program to be described below.

Next, the operation of the embodiment of the present invention will be explained in detail while explaining the above control routine. This embodiment applies the present invention to an internal combustion engine that controls the air-fuel ratio to the output air-fuel ratio when the exhaust temperature is below a predetermined value, and controls the air-fuel ratio to be richer than the output air-fuel ratio when the exhaust temperature exceeds the predetermined value. is applied.

Further, in order to simplify the explanation, the following description uses numerical values that do not interfere with the present invention, but the present invention is not limited to these numerical values.

FIG. 6 shows the main routine of this embodiment. In step 100, the engine rotational speed N and the intake air I are
In step 102, the basic fuel injection time is calculated from the engine speed N and the intake air 11Q, and in the next step 104, the basic fuel injection time τ is corrected according to the intake air temperature and the engine cooling water temperature. to calculate the fuel injection time τ. This fuel injection time τ corresponds to the output air-fuel ratio. In the next step 106, it is determined whether the current piston position is at top dead center (TDC) based on the cylinder discrimination signal and the rotation angle signal.

In the case of TDC, the multiplexer 82C is controlled in step 114 to input the knocking sensor 36 output to the A/D converter 82D via the integrating circuit 82E and the multiplexer 82C, and the output from the integrating circuit 82E, that is, the A/D at background level b. Start the conversion. As a result, the level of engine vibration that is not caused by knocking, that is, the digital value of the background level b is determined, and the A/D
At the end of the conversion, this digital value is stored in a predetermined area of the RAM. On the other hand, when it is determined in step 106 that it is not TDC, it is determined in step 108 whether or not the current piston position is 15° CA ATDC, and if the determination in step 108 is affirmative, the second input/output cap - Output a control signal from the trolley 6 to the knock gate circuit 82A to open the knock gate circuit 82A, and from the knock sensor 36 to the knock gate circuit 82A.

In the zero-order step 112, the output of the knocking sensor 36 is input to the A/D converter 82D via the peak hold circuit 82B and the multiplexer 82C. Time t (
90” (corresponding to CA ATDC) and set it in the conveyor register.

FIG. 7 shows a time match interrupt routine that is interrupted when the time set in step 112 is reached. When the current time matches the time set in the conveyor register, the second input/output register is activated in step 116. - Output a control signal from the trolley 6 to the A/D converter 82D to start A/D conversion of the peak hold circuit 82B output, and return to the main routine.

FIG. 8 shows an interrupt routine that is interrupted by an A/D conversion end signal from the A/D converter 82D when the A/D conversion of the output of the integrating circuit 82B is completed.
At step 18, the A/D value is stored as a peak value a in a predetermined area of the RAM, and at step 120, a control signal is output from the second input/output capotro 6 to the knock gate circuit 82A to close the knock gate circuit 82A.

The knocking sensor output, the opening/closing state of the knock gate circuit, the peak hold circuit output, and the integral circuit output when controlled as described above are shown in FIG. 9+11 to (4).

FIG. 1 shows a knocking control routine according to an embodiment of the present invention that is executed every 90" CA BTDC (every 120" CA). In the zero-order step 126, which calculates the basic ignition advance angle θ□ from the rotational speed N and the load Q/N, the load Q/N is set to a predetermined value (0, 8 (J
/, @v)) It is determined whether or not the knocking control region is reached by determining whether or not the knocking control region is being suppressed. When the load Q/N is less than a predetermined value, that is, when it is not in the knock control gB region, since the load is light, knocking does not occur and the exhaust temperature does not rise, so in step 128, the basic ignition advance angle θ13! is set as the executed ignition advance angle θ and returns to the main routine. When it is determined in step 126 that the load Q/N exceeds the predetermined value, that is, the knocking control J
When it is determined that the area is in the Btfl region, in step 130, the background level b, which was A/D converted in step 116 and stored in the RAM, and the peak value a, stored in the RAM in step 118, are fetched, and in step 13
2, it is determined whether the exhaust gas temperature exceeds a predetermined value (800° C.). When it is determined in step 132 that the exhaust gas temperature is below a predetermined value, in step 134 the product of the background level b multiplied by a constant k is used as a determination level, and this determination level is compared with the peak value a to determine whether knocking has occurred. Determine whether or not. When the peak value a exceeds the determination level, that is, when it is determined that knocking has occurred, the correction retard amount θ8 regarding knocking is increased by 1.5° CA in step 122. On the other hand, when it is determined in step 134 that the peak value a is below the determination level, that is, when it is determined that knocking has not occurred, it is determined in step 136 whether 100 ignitions have elapsed. When it is determined that 100 ignitions have elapsed, that is, when it is determined that knocking has not occurred during the predetermined number of ignitions, it is determined that the ignition timing is controlled on the retarded side from the knocking limit, and correction is made in step 138. Decrease the retardation amount θ by 1°CA. on the other hand,
If it is determined in step 136 that the predetermined number of ignitions has not elapsed, the process directly advances to step 146.

When it is determined in step 132 that the exhaust temperature exceeds the predetermined temperature, step 1 is performed to protect the exhaust system.
In step 40, the fuel injection time τ is multiplied by 1.3 to control the air-fuel ratio richly, and in the next step 142, the product obtained by multiplying the background level b by a constant k is set as a judgment level, and this judgment level and the peak value a are combined. By comparison, it is determined whether or not knocking has occurred. When the peak value a exceeds the determination level and it is determined that knocking has occurred, the correction retard amount θ1 is set to 1' in step 144.
CA is increased and the corrected retardation amount θ is made smaller than when the exhaust temperature is below a predetermined value, and when the peak value a is determined to be below the determination level, the process proceeds to step 136, and when 100 ignitions have elapsed, step 138 Proceed to and set the correction retard amount θ to 1
Reduce °CA.

In step 146, the maximum value θKIIIX for limiting the amount of retardation stored in the ROM in advance is read, and in the next step 148, it is determined whether the exhaust gas temperature exceeds a predetermined value (800° C.). When it is determined in step 148 that the exhaust gas temperature is below the predetermined value, the maximum value θ□ is increased by a predetermined value (for example, 5" CA) in step 150, and the process proceeds to step 152. If it is determined that the value exceeds the value, the process directly proceeds to step 152. In step 152, the maximum value θ□□ is compared with the retard amount θ8, and if θ0.≦θ, the maximum value θ is set in step 154. By setting □8 to θ, the retardation amount θ is limited to the maximum value θ, and step 15
Proceed to step 6. On the other hand, in step 152, θKmmg >θ,
When it is determined that the ignition advance angle θast is the same, the process directly proceeds to step 156. In step 156, the basic ignition advance angle θast calculated in step 124 is changed in steps 122 and 138, and the maximum value θKIII is changed in step 154.
The value obtained by subtracting the corrected retard amount θ, which is limited to X, is set as the effective ignition advance angle θ, and the process returns to the main routine.

Then, in a fuel injection amount control routine (not shown), the fuel injection valve 26 is opened for a time corresponding to the fuel injection time τ to control the fuel injection amount, the igniter is turned on at a predetermined crank angle, and the actual ignition advance angle θ By turning off the igniter at the point in time, the ignition timing is controlled so that the ignition is ignited at the effective ignition advance angle θ.

As a result of the above, if the exhaust temperature is below the predetermined temperature, step 10
The amount of fuel corresponding to the fuel injection time τ calculated in step 4 is injected, and the air-fuel ratio is controlled to become the output air-fuel ratio.

Since this output air-fuel ratio is normally about 12.5 (lean air-fuel ratio) and knocking is likely to occur, the correction retard amount θ is determined in step 122.

When it is determined that knocking has occurred by increasing the ignition timing, the ignition timing is immediately retarded, and in step 150, the maximum value θ for limiting the amount of retardation is increased by 11□. As a result, the amount of retardation per knock increases and the maximum value θ0. Since the yaw angle is increased, it is possible to significantly retard the ignition timing. The rise in exhaust gas temperature and the change in the retard amount at this time are shown in FIG. 2(C). Furthermore, if the exhaust temperature exceeds the predetermined value, fuel is injected for the fuel injection time τ calculated in step 140 (which is increased compared to when the exhaust temperature is below the predetermined value), and the air-fuel ratio changes to the output air. It is controlled to be richer than the fuel ratio. This rich air-fuel ratio is normally set to about 10, and knocking is less likely to occur than in the case of the output air-fuel ratio, so the corrected retardation amount θ8 is higher than in the above case.
is made smaller to control the ignition timing on the more advanced side. Therefore, in this case, the maximum value θ□ is also smaller than in the above case. Note that in the light load range, knocking does not occur and the exhaust temperature does not rise, so the air-fuel ratio is controlled to the output air-fuel ratio, and the ignition timing is controlled based on the basic ignition advance angle.

As explained above, according to this embodiment, the amount of correction retardation is increased at the output air-fuel ratio where knocking is likely to occur, and the maximum value for limiting the amount of correction retardation is increased, so that knocking is prevented. In the event that knocking occurs, the ignition timing is promptly retarded to prevent the level of knocking from exceeding the permissible level.In addition, when knocking is unlikely to occur, the correction retard amount is reduced and the maximum value is reduced. This provides the effect that the ignition timing is prevented from being abnormally retarded.

By the way, if the air-fuel ratio is changed to be richer than the air-fuel ratio where the knocking margin is minimum, if the air-fuel ratio is richer than the output air-fuel ratio, the combustion pressure will be lower and the amplitude of engine vibration, which determines the background level, will be lowered. When the air-fuel ratio is equal to the output air-fuel ratio, the combustion pressure becomes high and the amplitude of engine vibration becomes large. Therefore, the determination level changes due to a change in the background level due to a change in the air-fuel ratio, and there is a possibility that the ignition timing cannot be controlled to the knocking limit. Therefore, in the above embodiment, it is preferable to reduce the determination level when the air-fuel ratio is controlled to the output air-fuel ratio, and to increase the determination level when the air-fuel ratio is controlled to be richer than the output air-fuel ratio. The determination level can be changed by setting the determination level in step 142 as kb and multiplying the determination level kb by a constant less than 1 (for example, 0.8) in step 134.

Although the above description has been given of an engine in which the air-fuel ratio is changed richer than the air-fuel ratio at which the knock margin becomes the minimum, the present invention is not limited to this; An internal combustion engine that controls the air-fuel ratio according to operating conditions on the lean side, for example, controls the air-fuel ratio in low and medium load ranges to be leaner than the air-fuel ratio that minimizes knocking margin, and increases the amount of fuel injection in high load ranges. It can also be applied to an internal combustion engine in which the air-fuel ratio is changed by changing the air-fuel ratio. In this case, since knocking is more likely to occur when the air-fuel ratio is rich, the maximum value for limiting the correction retard amount when the air-fuel ratio is rich is increased.

Further, although the above description has been made regarding an internal combustion engine that directly detects the amount of intake air using an air flow meter, the present invention is not limited to this, and a pressure sensor that detects the intake pipe pressure on the downstream side of the throttle valve may be provided. The present invention can also be applied to internal combustion engines that indirectly detect the amount of intake air. Furthermore, in the above, an example was explained in which the air-fuel ratio is controlled to the output air-fuel ratio by open-loop control.
The present invention is not limited to this, but can also be applied to an engine that performs feedback control of the air-fuel ratio using the 02 sensor.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the knocking control routine of the embodiment of the present invention, Fig. 2 is a diagram showing changes in the retard amount when the air-fuel ratio changes, and Fig. 3 is the ignition timing according to the above embodiment. A schematic diagram of an engine equipped with a control device, FIG. 4 is a block diagram showing details of the control circuit shown in FIG. 3, FIG. 5 is a block diagram showing details of the input circuit shown in FIG. 4, and FIG. 6 is a block diagram showing details of the input circuit shown in FIG. FIG. 7 is a flow chart showing an example of the main routine of the example; FIG. 7 is a flow chart showing the time match interrupt routine of the above embodiment; FIG. 8 is a flow chart showing the A/D modification end interrupt routine of the above embodiment; FIGS. 9+11 to (4) are diagrams showing each waveform of the knocking sensor output, the opening/closing state of the knock gate circuit, the peak hold circuit output, and the integrating circuit output. 26...Fuel injection valve 36...Knocking sensor 44...Igniter 45...Control circuit 50...Exhaust temperature sensor

Claims (2)

[Claims] (1) Determine whether or not knocking has occurred in an internal combustion engine equipped with an air-fuel ratio control means that controls the air-fuel ratio according to the operating state of the engine, and retard the ignition timing when it is determined that knocking has occurred. In addition, when it is determined that knocking has not occurred, a retard amount for advancing the ignition timing is calculated, and the ignition timing is controlled by limiting the retard amount so that it does not exceed a predetermined maximum value. An ignition timing control device for an internal combustion engine, characterized in that the maximum value is changed in accordance with a change in the air-fuel ratio controlled by the air-fuel ratio control means. (2) The ignition timing control device for an internal combustion engine according to claim 1, wherein the maximum value is larger when the air-fuel ratio is the output air-fuel ratio than when the air-fuel ratio is richer than the output air-fuel ratio.