JP2890908B2 - Secondary air control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary air control device for supplying secondary air to an exhaust system in order to reburn unburned gas (HC, CO) discharged from an internal combustion engine. .

[0002]

2. Description of the Related Art Conventionally, as one method of purifying exhaust gas from an internal combustion engine, secondary air is supplied to an exhaust system. In this method, the exhaust gas discharged from the combustion chamber undergoes an oxidation reaction with air supplied by an air pump, thereby producing hydrocarbons (HC) in the exhaust gas.
And the emission of carbon monoxide (CO) is reduced.

A secondary air control device of this type is disclosed, for example, in Japanese Patent Application Laid-Open No. 63-41641. In this technique, secondary air supply means for supplying or stopping secondary air to an exhaust system is provided, and supply or stop of secondary air by the secondary air supply means is controlled in accordance with the water temperature of the internal combustion engine by a water temperature sensor. I have. That is, the supply start water temperature of the secondary air and the supply end water temperature higher than the supply start water temperature are set in advance. When the water temperature by the water temperature sensor is lower than the supply start water temperature, the supply of the secondary air by the secondary air supply means is stopped. When the water temperature is equal to or higher than the supply start water temperature and lower than the supply end water temperature, the secondary air is supplied, and the supply end water temperature is higher than the supply end water temperature. Then, the supply of the secondary air is terminated.

[0004]

The internal combustion engine,
In particular, various fuels having different fuel properties (mainly distillation characteristics) are appropriately used as fuels used for automobile engines. However, the conventional secondary air control device described above controls the supply and stop of the secondary air irrespective of the difference in the fuel properties described above, and thus has a problem that the air-fuel ratio is disturbed especially when heavy fuel is used. Was.

[0005] That is, based on whether or not 50% or more of the fuel evaporates at, for example, 100 ° C, a light fuel having a low boiling point that is more than 50% evaporable, There are heavy fuels with high boiling points, which only evaporate. Therefore, when heavy fuel is used as the fuel, the fuel is less likely to evaporate than when light fuel is used. More.

Here, the amount of fuel actually entering the combustion chamber is:
In addition to the amount of fuel that did not adhere to the intake passage wall surface of the fuel injected from the fuel injection valve, the amount of the fuel that adhered to the intake passage that flowed in a liquid state and the amount of fuel that adhered to the intake passage after evaporation Some are inhaled. For this reason, when the amount of fuel adhering to the intake passage such as heavy fuel is large, the above-mentioned amounts are not constantly constant, and the amount of fuel entering the combustion chamber varies from cycle to cycle. Fluctuations for each increase. Then, due to the fluctuation of the air-fuel ratio, the amount of fuel supplied into the cylinder of the engine may become leaner than the lean limit. As a result, a misfire occurs, a large amount of unburned HC and CO is discharged, and the exhaust properties deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a secondary air control device for an internal combustion engine capable of controlling the supply of secondary air according to differences in fuel properties. Is to do.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention, as shown in FIG. 1, supplies and stops secondary air to an exhaust system of an internal combustion engine M1, and supplies the secondary air. An adjustable secondary air supply means M2, an operating state detecting means M3 for detecting an operating state of the internal combustion engine M1, a fuel property detecting means M4 for detecting a property of fuel of the internal combustion engine M1, Internal combustion engine M by state detection means M3
1 is a preset secondary air supply operation state and the fuel property detected by the fuel property detection means M4 is a normal property within a predetermined range, the secondary air supply means M
The second supply control means M5 controls the second air supply system 2 to supply a preset amount of secondary air to the exhaust system, and the operation state of the internal combustion engine M1 by the operation state detection means M3 is the secondary air supply operation state. If the fuel property detected by the fuel property detection means M4 is out of the predetermined range, the secondary air supply means M2 is controlled to make the supply amount of the secondary air different from the supply amount in the case of the normal property. And supply control means M6.

[0009]

When the internal combustion engine M1 is operating, its operating state is detected by the operating state detecting means M3, and the fuel property is detected by the fuel property detecting means M4. When the operating state of the internal combustion engine M1 by the operating state detecting means M3 is a preset secondary air supply operating state and the fuel property by the fuel property detecting means M4 is a normal property within a predetermined range, the first supply control is performed. The means M5 controls the secondary air supply means M2 to supply a preset amount of secondary air to the exhaust system.

If the operating state of the internal combustion engine M1 by the operating state detecting means M3 is the secondary air supply operating state and the fuel property by the fuel property detecting means M4 is out of the predetermined range, the second The supply control means M6 controls the secondary air supply means M2 to make the supply amount of the secondary air different from the supply amount in the case of the normal property.

Therefore, the supply amount of the secondary air is controlled in accordance with the difference in the fuel properties, and it becomes possible to purify unburned HC and CO with an optimum amount of the secondary air.

[0012]

FIG. 2 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 2 is a diagram showing a schematic configuration of an automobile multi-cylinder engine 1 as an internal combustion engine provided with a secondary air control device. The engine 1 has a piston 3 in a cylinder 2. A combustion chamber 4 formed above the piston 3 has an intake passage 5 forming a part of an intake system and an exhaust gas forming a part of an exhaust system. The passage 6 is in communication. A communication portion between the combustion chamber 4 and the intake passage 5 and a communication portion between the combustion chamber 4 and the exhaust passage 6 are opened and closed by an intake valve 7 and an exhaust valve 8.

The engine 1 introduces a mixture of intake air from an intake passage 5 and fuel injected from a fuel injection valve 9 into a combustion chamber 4 through an intake valve 7. An ignition plug 11 is mounted on the engine 1, and an ignition voltage distributed by a distributor 12 is applied to the ignition plug 11. The distributor 12 distributes the high voltage output from the igniter 13 to each of the ignition plugs 11 in synchronization with the crank angle of the engine 1. The ignition timing of each of the ignition plugs 11 is based on the high voltage output from the igniter 13. Determined by timing.
After the engine 1 explodes the air-fuel mixture in the combustion chamber 4 by the ignition plug 11 to obtain a driving force, the exhaust gas is discharged to the exhaust passage 6 through the exhaust valve 8.

The distributor 12 has:
A rotation speed sensor 14 that detects the rotation of the rotor and outputs an engine rotation signal is provided. Further, a water temperature sensor 1 as an operating state detecting means for detecting the temperature of the cooling water of the engine 1 is provided in the cylinder block 1a of the engine 1.
5 are attached.

A surge tank 16 for suppressing pulsation of intake air is provided in a part of the intake passage 5, and a pressure sensor 17 of a diaphragm type is attached to the surge tank 16. On the upstream side of the surge tank 16, a throttle valve 18 that opens and closes in conjunction with operation of an accelerator pedal (not shown) is provided, and the opening and closing of the throttle valve 18 adjusts the amount of intake air to the intake passage 5. Is done. An idle switch 19 that is turned on when the throttle valve 18 is fully closed is mounted near the throttle valve 18.

A throttle valve 1 is provided in the intake passage 5.
8, and a bypass passage 21 that communicates between the upstream side and the downstream side of the throttle valve 18 is provided.
An idle speed control valve (ISCV) 22 is mounted in the middle of the bypass passage 21. The ISCV 22 is a so-called step motor type in which the rotor of the step motor rotates in response to the pulse signal, thereby changing the lift amount of the valve body and changing the opening area of the valve. The ISCV 22 controls the opening degree of the ISCV 22. The idle speed is controlled to the target speed by adjusting the amount of air flowing through the bypass passage 21. Further, an air cleaner 23 is disposed upstream of the throttle valve 18, and an intake air temperature sensor 24 for detecting an intake air temperature is mounted near the air cleaner 23.

On the other hand, an oxygen sensor 25 for detecting the oxygen concentration in the exhaust gas and an exhaust gas (H
A three-way catalytic converter 26 for purifying (C, CO, NOx) is attached. Further, one end of a secondary air supply passage 27 is connected between the oxygen sensor 25 and the three-way catalytic converter 26 in the exhaust passage 6. This 2
An air pump 28 as secondary air supply means is connected to the other end of the secondary air supply passage 27 so that the secondary air discharged from the air pump 28 is guided to the exhaust passage 6 via the secondary air supply passage 27. It has become. In the middle of the secondary air supply passage 27, an air switching valve (ASV) 29
The ASV 29 guides the secondary air from the air pump 28 to the exhaust passage 6 when turned on, and discharges the secondary air to the atmosphere when turned off.

In addition, the fuel tank 31 mounted on the vehicle
A fuel temperature sensor 32 for detecting the temperature of the fuel in the fuel tank 31 is attached to a lower part of the fuel tank 31. The fuel temperature sensor 32 constitutes a part of the fuel property detecting means. A canister 34 is connected to an upper portion of the fuel tank 31 via a vapor passage 33, and the evaporated fuel generated in the fuel tank 31 is guided to the canister 34 through the vapor passage 33. The canister 34 is an evaporative fuel adsorption container containing activated carbon, and the evaporative fuel is once adsorbed to the activated carbon.

In the middle of the vapor passage 33, a vapor flow meter 35 is provided. The vapor flow meter 35 includes a rotating unit 36 that rotates by the passage of the evaporated fuel.
6, a signal rotor (not shown) is attached. A vapor flow sensor 37 is attached to the housing of the vapor flow meter 35, and outputs a high voltage when the signal rotor of the rotating unit 36 crosses the vapor flow sensor 37, and outputs a low voltage when the signal rotor is separated. Output. The vapor flow sensor 37 is provided with the fuel temperature sensor 3.
2 together with the fuel property detecting means.

The canister 34 is connected to the intake passage 5 downstream of the surge tank 16 via a purge passage 38 so that the fuel vapor in the canister 34 is sucked into the engine 1. A purge control valve 39 is provided in the middle of the purge passage 38. The purge control valve 39 is for opening and closing the purge passage 38 to adjust the purge amount of the evaporated fuel guided from the canister 34 to the intake passage 5. It is adjusted by duty control. An orifice (not shown) is provided in the purge passage 38, and the intake passage 5
Is prevented from directly acting on the fuel tank 31.

The rotation speed sensor 14, the water temperature sensor 15,
The pressure sensor 17, the idle switch 19, the intake air temperature sensor 24, the oxygen sensor 25, the fuel temperature sensor 32, and the vapor flow sensor 37 are electrically connected to the input side of an electronic control unit (hereinafter simply referred to as “ECU”) 41. I have. Also,
Each fuel injection valve 9, igniter 13, ISCV22, AS
V29 and the purge control valve 39 are connected to the ECU 4
1 is electrically connected to the output side. And ECU
Reference numeral 41 denotes each fuel injector 9, igniter 13, ISCV 22, ASV 29 based on detection signals from the various sensors.
And the purge control valve 39 is controlled.

Next, the configuration of the ECU 41 will be described with reference to FIG.
This will be described with reference to the block diagram of FIG. The ECU 41 includes a central processing unit (CPU) 42 constituting first supply control means and second supply control means, and a read-only memory (ROM).
43, a random access memory (RAM) 44, a backup RAM 45, a clock generator 46, input ports 48, 49, and output ports 51, 52, 53, 5
4 and 55, which are connected to each other by a bus 56. The CPU 42 executes various arithmetic processes in accordance with a preset control program.
A control program and initial data necessary for executing the arithmetic processing in the PU 42 are stored in advance. RAM4
Reference numeral 4 temporarily stores the operation result of the CPU 42. The backup RAM 45 is backed up by a battery so as to retain various data even after the power is turned off.
The clock generator 46 outputs the master clock to the CPU.
42.

The fuel temperature signal from the fuel temperature sensor 32 is input to an input port 48 via a buffer 57, a multiplexer 58, and an A / D converter 59. The pressure signal from the pressure sensor 17 is supplied to a filter 61, a buffer 62,
The signal is input to the input port 48 via the multiplexer 58 and the A / D converter 59. The water temperature signal from the water temperature sensor 15 is supplied to the buffer 63, the multiplexer 58, the A / D converter 5
9 to the input port 48. An intake air temperature signal from the intake air temperature sensor 24 is input to an input port 48 via a buffer 64, a multiplexer 58, and an A / D converter 59. A multiplexer 58 selectively outputs the fuel temperature signal, the pressure signal, the water temperature signal, and the intake temperature signal, and outputs an A / D signal.
Converter 59 converts those signals into digital signals. The filter 61 is for removing a pulsating component of the intake pipe pressure contained in the pressure signal of the pressure sensor 17.

The oxygen concentration signal from the oxygen sensor 25 is input to the input port 49 via the buffer 65 and the comparator 66. The engine rotation signal from the rotation speed sensor 14 and the vapor flow signal from the vapor flow sensor 37 are input to the input port 49 via the shaping circuit 67.
The on / off signal from the idle switch 19 is input to the input port 49 via the buffer 68.

The CPU 42 detects the fuel temperature Ti, the pressure value, the water temperature, the intake air temperature, the rich / lean signal, the engine speed, the vapor flow rate Qi, and the on / off state of the idle switch 19 based on these signals.

On the other hand, the CPU 42 controls the igniter 13 through the output port 51 and the drive circuit 69, and controls the opening and closing of the fuel injection valve 9 through the output port 52 and the drive circuit 70. Further, the CPU 42 controls the opening degree of the ISCV 22 via the output port 53 and the drive circuit 71, and controls the opening and closing of the purge control valve 39 via the output port 54 and the drive circuit 72, and controls the output port 55 and the drive circuit 73. The opening / closing control of the ASV 29 is performed through the control unit.

In this embodiment, the CPU 42 controls the ON / OFF timing of the ASV 29 in accordance with the water temperature at that time by the water temperature sensor 15, thereby controlling the air pump 2.
The supply of secondary air to the exhaust passage 6 is started and terminated from the outlet 8. Specifically, the supply start water temperature (for example, 0 ° C.) is set as the supply start operation state when the supply of the secondary air is started
A is stored in the ROM 43.

In the ROM 43, a first supply end water temperature (for example, 50 ° C.) B for terminating the supply of the secondary air when the fuel property is the normal property is stored. The first supply end water temperature B corresponds to a preset normal supply end operation state. The ROM 43 stores a second supply end water temperature C for terminating the supply of the secondary air when the fuel property is heavy. This second
The supply end water temperature C is set to be a predetermined temperature higher than the first supply end water temperature B (for example, 60 ° C.) so that the supply time of the secondary air is longer than when the fuel property is the normal property. ).

Further, the ROM 43 stores a third supply end water temperature D for terminating the supply of the secondary air when the fuel property is light. The third supply end water temperature D is set lower by a predetermined temperature than the first supply end water temperature B so that the supply time of the secondary air is shorter than when the fuel property is the normal property. (For example, 40 ° C.). Accordingly, the supply start water temperature A, the first supply end water temperature B, the second supply end water temperature C, and the third supply end water temperature D
Have a relationship of A <D <B <C. The second supply end water temperature C and the third supply end water temperature D correspond to a supply end operation state different from the normal supply end operation state (in this case, the first supply end water temperature B).

When the water temperature detected by the water temperature sensor 15 is lower than the supply start water temperature A, the CPU 42
9 is turned off to stop the supply of the secondary air. Also, CP
U42 is the first to third supply end water temperatures B, depending on the fuel properties.
One of C and D is selected, and when it is equal to or higher than the supply start water temperature A and lower than the selected supply end water temperatures B, C and D, the ASV 29 is turned on to supply the secondary air. Further, when the water temperature becomes equal to or higher than the selected supply end water temperatures B, C, and D, the CPU 42 turns off the ASV 29 and ends the supply of the secondary air.

Next, the operation and effect of the embodiment constructed as described above will be described. The flowchart of FIG. 4 shows a routine for controlling the end of the supply of the secondary air among the processes executed by the CPU 42,
It is started by a periodic interruption every predetermined time.

When the CPU 42 shifts to this processing routine in a state in which the secondary air is being supplied, the CPU 42 detects the property of the fuel in step 101. That is, the CPU 42 reads the fuel temperature Ti in the fuel tank 31 by the fuel temperature sensor 32 and the vapor flow rate Qi by the vapor flow rate sensor 37.

Next, the CPU 42 executes steps 102 and 10
In 3, it is determined whether the fuel is light, heavy, or normal. In order to make this determination, a determination value Ta of the fuel temperature and a determination value Qa of the vapor flow rate are stored in the ROM 43 in advance. And CPU
42 is a step 102 in which the fuel temperature Ti by the fuel temperature sensor 32 is compared with the determination value Ta, and the vapor flow rate sensor 37
Then, the vapor flow rate Qi at that time is compared with the determination value Qa. The fuel temperature Ti is lower than the determination value Ta (Ti <Ta
) And the vapor flow rate Qi is equal to or greater than the determination value Qa (Qi
.Gtoreq.Qa), the CPU 42 determines that a large amount of fuel has evaporated despite the low fuel temperature Ti, that is, that the fuel used at that time contains many low-boiling components, and It is determined that the fuel.

If the CPU 42 determines in step 102 that the fuel is not light fuel, the process proceeds to step 103, in which the fuel temperature Ti by the fuel temperature sensor 32 and the determination value T
a, and the vapor flow rate Qi at that time by the vapor flow rate sensor 37 is compared with the determination value Qa. Fuel temperature Ti
Is greater than or equal to the determination value Ta (Ti ≧ Ta) and the vapor flow rate Qi is smaller than the determination value Qa (Qi <Qa), CP
U42 determines that only a small amount of fuel evaporates in spite of the high fuel temperature Ti, that is, determines that the low boiling component is low in the fuel used at that time, and determines that the fuel is a heavy fuel. I do.

If the CPU 42 determines in step 103 that the fuel is not heavy fuel, it determines that the fuel being used is neither light fuel nor heavy fuel, and proceeds to step 104. CP in step 104
U42 sets the first supply end water temperature B as the secondary air supply end water temperature, and then determines in step 105 whether the secondary air supply end condition is satisfied. This determination is made based on whether the water temperature detected by the water temperature sensor 15 is equal to or higher than the first supply end water temperature B, whether the water temperature is lower than the supply start water temperature A, and whether the throttle valve 18 is fully opened. And so on. If the supply end condition in step 105 is not satisfied (the water temperature is equal to or higher than the supply start water temperature A, is lower than the first supply end water temperature B, and the throttle valve 18 is not fully opened), the CPU 42 sets A to
The ON state of the SV 29 is maintained, and this routine ends.
Therefore, the secondary air from the air pump 28 is continuously supplied to the exhaust passage 6.

When the supply termination condition in step 105 is satisfied, that is, whether the water temperature is lower than the supply start water temperature A, or whether the water temperature is equal to or higher than the first supply termination water temperature B,
Alternatively, when the throttle valve 18 is fully opened, the CPU 42
Turns off the ASV 29 in step 106 and terminates this routine. Then, the secondary air from the air pump 28 is discharged to the atmosphere without being supplied to the exhaust passage 6.

If the fuel is light fuel in step 102, the CPU 42 determines in step 107 the third supply end water temperature D (in this case, 4
0 ° C). Subsequently, the CPU 42 proceeds to step 10
Then, it is determined whether or not the condition for terminating the supply of the secondary air is satisfied in the same manner as in step 105. If this condition is not satisfied, the CPU 42 keeps the ON state of the ASV 29 and ends this routine. Therefore, the secondary air from the air pump 28 is continuously supplied to the exhaust passage 6. On the other hand, when the supply end condition is satisfied in step 108, the CPU 42 turns off the ASV 29 in step 109 in the same manner as in step 106, and ends this routine. Then, the secondary air from the air pump 28 is discharged to the atmosphere without being supplied to the exhaust passage 6.

As described above, when the third supply ending water temperature D is set as the secondary air supply ending water temperature when the light fuel is used, the third supply ending water temperature D becomes higher than the first supply ending water temperature B. Therefore, the supply time of the secondary air is shorter than when the normal fuel is used. Here, since the light fuel has a good evaporability and a small amount of adhesion to the wall of the intake passage 5, the air-fuel ratio in each cycle is small, and the unburned HC and CO emissions are smaller than those of the heavy fuel. Considerably less. Therefore, even if the supply time of the secondary air is shortened as described above, HC, CO
Can be purified to a sufficiently low level.

When secondary air is supplied to the exhaust passage 6, the air-fuel ratio in the three-way catalytic converter 26 becomes lean due to the stoichiometric air-fuel ratio, and while unburned HC and CO can be purified by an oxidation reaction, NOx is reduced by a reduction reaction. It becomes difficult to be purified. However, in the present embodiment, since the supply time of the secondary air is shortened as described above, it is possible to increase the NOx purification amount.

If the fuel is heavy fuel in step 103, the CPU 42 determines in step 110 that the secondary air supply end water temperature is the second supply end water temperature C.
(In this case, 60 ° C.). Subsequently, the CPU 42 proceeds to step 111, and determines whether or not the condition for terminating the supply of the secondary air is satisfied in the same manner as in step 105. If this condition is not satisfied, the CPU 42
9 is maintained, and this routine ends. Therefore, the secondary air from the air pump 28 is continuously supplied to the exhaust passage 6. On the other hand, when the supply end condition in step 111 is satisfied, the CPU 42 turns off the ASV 29 in step 112 in the same manner as in step 106,
This routine ends. Then, the secondary air from the air pump 28 is discharged to the atmosphere without being supplied to the exhaust passage 6.

As described above, when the second supply end water temperature C is set as the secondary air supply end water temperature when the heavy fuel is used, the second supply end water temperature C becomes the first supply end water temperature B. Therefore, the supply time of the secondary air is longer than when the normal fuel is used. For this reason, when heavy fuel is used, a large amount of fuel adheres to the wall surface of the intake passage 5, and the air-fuel ratio is disturbed between the cycles to discharge a large amount of unburned HC and unburned CO. Because of the long supply time, the unburned HC and unburned CO are oxidized with the secondary air and are reliably purified.

As described above, in this embodiment, the fuel temperature sensor 3
2 and the fuel flow rate Qi is detected by the vapor flow rate sensor 37 (step 10).
1) Based on the fuel temperature Ti and the vapor flow rate Qi, it is determined whether the fuel is a normal fuel, a light fuel, or a heavy fuel (steps 102 and 103).
As the supply end water temperature when terminating the supply of the next air, the first supply end water temperature B is set when the normal fuel is used (step 104), and the third supply end water temperature D is set when the light fuel is used (step 107). When the heavy fuel is used, the second supply end water temperature C is set (step 110). For this reason, unlike the prior art in which the supply and stop of the secondary air is controlled irrespective of the difference in the fuel properties, in the present embodiment, the supply amount of the secondary air is increased when heavy fuel is used. Unburned HC and unburned CO can be reliably purified, and when light fuel is used, the supply amount of secondary air can be reduced to improve NOx purification performance.

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and may be arbitrarily changed without departing from the spirit of the present invention, for example, as follows. (1) In the above-described embodiment, the fuel temperature sensor 32 and the vapor flow rate sensor 37 are used to detect the fuel properties. Instead, however, the fuel temperature sensor 32 and the vapor flow rate sensor 37 are used to determine the fuel temperature Ti and the pressure rise time in the fuel tank 31. Known methods such as a method of detecting the fuel property based on the ease of evaporation of the fuel (lead vapor pressure: RVP), a method of detecting the pressure in the fuel tank 31, and a method of learning the air-fuel ratio may be used. (2) Although the air pump 28 is used as the secondary air supply means in the above embodiment, an air suction system may be used instead of the air pump 28. In this air suction system, only the negative pressure portion of the pulsation of the combustion gas generated in the exhaust passage 6 such as an exhaust manifold is taken out by a reed valve, and secondary air is introduced into the exhaust passage 6 using this negative pressure. In this case, the same effect as in the above embodiment can be obtained by controlling the on / off timing of the ASV 29. (3) The supply start water temperature A, the first supply end water temperature B, the second supply end water temperature C, and the third supply end water temperature D are not limited to the values in the above embodiment, and may be changed as appropriate. Good. (4) In the above embodiment, the supply time of the secondary air is longer when using heavy fuel than when using normal fuel, and the supply time for secondary air is shorter when using light fuel than when using normal fuel. However, only one of the supply times may be changed. (5) In general, when the engine 1 shifts from a steady state or an acceleration state to a deceleration state, the fuel adhering to the wall surface of the intake passage 5 evaporates rapidly, and a rich mixture temporarily enters the combustion chamber 4. And may discharge a large amount of unburned gas. Therefore, when the supply time of the secondary air is increased as in the above-described embodiment, the so-called afterburn, in which the unburned gas explosively burns in the exhaust system, is likely to occur. In response to this, a dashpot is used to temporarily delay closing of the throttle valve to the idle position during deceleration to prevent misfire, or use an ISC (idle speed control device) to supply air to the intake system during deceleration. Or to be introduced. Where the dashpot and ISC
In any case, there is a possibility that the deceleration characteristics may be deteriorated. Therefore, it is necessary to set the opening degree of the dashpot and the amount of inflow air by ISC so that the reduction in the deceleration characteristics is small and the occurrence of afterburn is reduced.

[0044]

As described above in detail, according to the present invention, when the operation state of the internal combustion engine is the preset secondary air supply operation state and the fuel property is the normal property within a predetermined range, the preset value is set. Supply the secondary air to the exhaust system,
When the operation state of the internal combustion engine is the secondary air supply operation state and the fuel property is out of the predetermined range, the supply amount of the secondary air is made different from the supply amount in the case of the normal property. There is an excellent effect that the secondary air supply control to the exhaust system by the secondary air supply means can be performed according to the difference in fuel properties.

[Brief description of the drawings]

FIG. 1 is a conceptual configuration diagram of the present invention.

FIG. 2 is a schematic configuration diagram showing a secondary air control device for an internal combustion engine according to one embodiment of the present invention;

FIG. 3 is a block diagram illustrating a configuration of an ECU according to an embodiment.

FIG. 4 is a flowchart for explaining the operation of one embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine as an internal combustion engine, 6 ... Exhaust passage which comprises a part of exhaust system, 15 ... Water temperature sensor as operating state detecting means, 28 ... Air pump as secondary air supply means,
32: a fuel temperature sensor forming a part of the fuel property detecting means, 37: a vapor flow rate sensor forming a part of the fuel property detecting means, 42: forming a first supply control means and a second supply control means. CPU

Claims (1)

(57) [Claims] 1. Secondary air supply means for supplying and stopping secondary air to an exhaust system of an internal combustion engine and capable of adjusting a supply amount of the secondary air, and an operation state for detecting an operation state of the internal combustion engine. Detecting means; fuel property detecting means for detecting fuel properties of the internal combustion engine; operating state of the internal combustion engine by the operating state detecting means being a preset secondary air supply operating state; and the fuel property detecting means First fuel supply control means for controlling the secondary air supply means to supply a predetermined amount of secondary air to an exhaust system when the fuel property of the fuel cell is in a normal property within a predetermined range; If the operating state of the internal combustion engine is the secondary air supply operating state and the fuel property by the fuel property detecting means deviates from the predetermined range,
A secondary air control device for an internal combustion engine, comprising: a second supply control means for controlling a secondary air supply means to make a supply amount of secondary air different from a supply amount in a case of a normal property.