JP2011069332A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine suppressing torque fluctuation in dither control executing switching between rich combustion and lean combustion even with an engine body including one injector per one cylinder. <P>SOLUTION: In the internal combustion engine 1, a catalyst device 3 is warmed up by sending exhaust gas G2 containing oxygen and unburned gas formed by dither control setting fuel injection quantity to each cylinder 2c so as to execute switching between rich combustion and lean combustion to the catalyst device 3. ECU 5 controlling the internal combustion engine 1 sets fuel injection quantity to each cylinder 2c so as to maintain output torque of a cylinder 2c in which rich combustion occurs and output torque of a cylinder 2c in which lean combustion occurs equivalent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine of a vehicle.

  A vehicle equipped with an internal combustion engine has a catalyst device that purifies exhaust gas by detoxifying harmful components contained in exhaust gas exhausted from the engine body by oxidation and reduction. Since the catalyst device cannot effectively purify the exhaust gas if the temperature of the internal catalyst is low, when the temperature of the catalyst is low, such as when starting an internal combustion engine, the catalyst is at a predetermined temperature (activation temperature). It is necessary to warm up the catalytic device until it rises to).

  As a method for warming up the catalyst device, for example, in Patent Document 1, the engine is dither controlled so as to switch between rich combustion and lean combustion, and carbon monoxide contained in unburned gas generated by rich combustion is lean burned. Discloses a technique for quickly warming up a catalyst device with heat of reaction (oxidation heat) when oxidized with oxygen generated in the above.

  However, in the case of dither control in which rich combustion and lean combustion are switched, the output torque of the cylinder that performs rich combustion differs from the output torque of the cylinder that performs lean combustion, resulting in torque fluctuations in the engine. By adjusting the ignition timing of the rich-burning cylinder and the ignition timing of the lean-burning cylinder, the output torque of the rich-burning cylinder and the lean-burning cylinder is made substantially equal to suppress torque fluctuations generated in the engine. ing.

  Further, for example, in Patent Document 2, when the engine is dither controlled so that rich combustion and lean combustion are switched, in-cylinder injection is performed for a cylinder that performs rich combustion and port injection is performed during the intake stroke. Thus, a technology is disclosed in which the output torque of the cylinder is suppressed, the output torques of the rich-burning cylinder and the lean-burning cylinder are made substantially equal, and torque fluctuations generated in the engine are suppressed.

JP-A-4-308311 JP 2007-332867 A

However, in the technique disclosed in Patent Document 1, it is necessary to create a map for setting the ignition timing according to the air-fuel ratio in order to adjust the ignition timing of the rich burning cylinder and the ignition timing of the lean burning cylinder. There is a problem that man-hours for creating a map are required.
The technique disclosed in Patent Document 2 requires an injector that injects fuel into the intake port and an injector that injects fuel directly into the cylinder. That is, two injectors are required for one cylinder, which causes a problem that the structure of the engine is complicated and the cost is increased.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an internal combustion engine that can suppress torque fluctuation when dither control is performed so that rich combustion and lean combustion are switched even if the engine body has one injector per cylinder. .

  In order to solve the above-mentioned problems, claim 1 of the present invention provides an engine body, a catalyst device for purifying exhaust gas disposed in an exhaust pipe of the engine body, and each cylinder so that rich combustion and lean combustion are switched. A control device for supplying oxygen and unburned gas to the exhaust gas by dither control for setting the fuel injection amount to the exhaust gas and feeding the catalyst device with the reaction heat of the oxygen and unburned gas And an internal combustion engine configured to include. The control device sets the fuel injection amount to each cylinder so that the output torque of the cylinder that performs rich combustion is equal to the output torque of the cylinder that performs lean combustion.

According to claim 1, the engine body is dither controlled so that the rich combustion and the lean combustion are switched, and the exhaust gas containing oxygen and unburned gas is sent to the catalyst device, and the catalyst device is driven by the reaction heat of oxygen and unburned gas. In a warm-up internal combustion engine, the output torques of the rich-burning cylinder and the lean-burning cylinder can be made equal.
Therefore, the engine body can be dither controlled so that torque fluctuation does not occur.

  The internal combustion engine according to claim 2 of the present invention is characterized in that one of the plurality of cylinders provided in the engine body is a rich cylinder that performs rich combustion, and the other is a lean cylinder that performs lean combustion. .

According to the second aspect, one of the plurality of cylinders provided in the engine body can be richly burned, and all the other cylinders can be lean burned.
Therefore, the engine body can be dither controlled so that the rich combustion and the lean combustion are switched.

  In the internal combustion engine according to claim 3 of the present invention, the air-fuel ratio of the exhaust gas sent from the engine body to the catalyst device is stoichiometric when the control device performs the dither control of the engine body. It is characterized by.

According to the third aspect, when the engine body is dither-controlled, the air-fuel ratio of the exhaust gas sent to the catalyst device can be stoichiometric.
Therefore, the exhaust gas can be efficiently purified by the catalyst device.

  Further, the internal combustion engine according to claim 4 of the present invention is characterized in that the control device corrects the fuel injection amount to each cylinder based on the rotational speed and the intake pressure of the engine body.

  According to the fourth aspect, the fuel injection amount to each cylinder can be changed based on the state of the engine body, and the output torque of the cylinder can be varied according to the load of the engine body.

  According to the present invention, it is possible to provide an internal combustion engine capable of suppressing torque fluctuations even when an engine body having one injector per cylinder is subjected to dither control so that rich combustion and lean combustion are switched.

(A) is a figure which shows the structural example of an internal combustion engine, (b) is a figure which shows the cylinder which carries out rich combustion, and the cylinder which carries out lean combustion. It is a graph which shows the relationship between the output torque of a cylinder, and an air fuel ratio. It is an example of the engine state map which shows the state of an engine main body. It is a flowchart which shows the procedure in which ECU warms up a catalyst apparatus.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
As shown in FIG. 1A, the internal combustion engine 1 according to the present embodiment includes, for example, a four-cylinder engine main body 2 including four cylinders 2c, and each of intake manifolds 8 connected to the four cylinders 2c. Includes one injector 2b for injecting fuel Fu.
Furthermore, a supercharger 7 such as a turbocharger that compresses the air G1 taken from the atmosphere via the air cleaner 7a and sends it to the intake manifold 8, and an intercooler 7b that cools the air G1 compressed by the supercharger 7 are provided. It is equipped.
In addition, the internal combustion engine 1 without the supercharger 7, the air cleaner 7a, and the intercooler 7b may be used.

The internal combustion engine 1 is controlled by an ECU (Engine Control Unit) 5 as a control device.
The ECU 5 is composed of, for example, a microcomputer (not shown), a microcomputer (ROM) including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and a peripheral circuit. Is executed to control the internal combustion engine 1.

For example, the ECU 5 transmits a control signal to the throttle valve 4 to adjust the opening degree according to the operation amount of a throttle pedal (not shown), and adjusts the flow rate of the air G1 flowing through the intake manifold 8.
In addition, a control signal is transmitted to each of the plurality of injectors 2b to control the fuel injection amount of each injector 2b. That is, the fuel injection amount to each cylinder 2c is controlled.
The ECU 5 controls each cylinder 2c of the engine body 2 to a preset air-fuel ratio (A / F) by controlling the flow rate of the air G1 flowing through the intake manifold 8 and the fuel injection amount of the injector 2b. .

The method in which the ECU 5 sets each cylinder 2c to a preset air-fuel ratio A / F is not limited. For example, the opening of the throttle valve 4, the fuel injection amount of the injector 2b, and the air-fuel ratio A / F A map indicating the relationship is stored in advance in a ROM (not shown).
Since the flow rate of the air G1 flowing through the intake manifold 8 changes according to the opening degree of the throttle valve 4, the ECU 5 refers to the map according to the opening degree of the throttle valve 4 and determines the fuel injection amount of the injector 2b. By adjusting, each cylinder 2c can be set to a preset air-fuel ratio A / F.

The fuel Fu pumped from the fuel tank 6 by the fuel pump 6a is pressurized by a high-pressure pump (not shown) and then sent to the delivery pipe 2a. The intake manifold 8 connected to each cylinder 2c of the engine body 2 by the injector 2b. Is injected into.
Hereinafter, the injection of the fuel Fu into the intake manifold 8 is referred to as the injection of the fuel Fu into the cylinder 2c.
An injector 2b may be provided so that the fuel Fu is directly injected into each cylinder 2c.

Air G1 taken in from the atmosphere via the air cleaner 7a is compressed by the supercharger 7 and then cooled by the intercooler 7b. Then, after the flow rate is adjusted by the throttle valve 4, it flows through the intake manifold 8 via a surge tank (not shown), is mixed with the fuel Fu injected from the injector 2b, and is supplied to each cylinder 2c of the engine body 2. .
The mixed gas of the air G1 and the fuel Fu supplied to each cylinder 2c of the engine body 2 is combusted in each cylinder 2c and discharged as exhaust gas G2, and flows through the exhaust manifold 9 which is an exhaust pipe, and is exhausted. It is fed into the catalyst device 3 disposed in the manifold 9.

Harmful components such as carbon monoxide, hydrocarbons, and nitrogen compounds contained in the exhaust gas G2 are oxidized and reduced by the action of the catalyst provided in the catalyst device 3, and become harmless carbon dioxide, water, and the like.
That is, the exhaust gas G2 is purified by the catalyst device 3 and released to the atmosphere as a release gas G3 that does not contain harmful components.

  However, the catalyst provided in the catalyst device 3 cannot exhibit a sufficient effect when the temperature is lower than the predetermined activation temperature, and cannot efficiently purify the exhaust gas G2. For example, when the internal combustion engine 1 is started, since the temperature of the catalyst provided in the catalyst device 3 is lower than a predetermined activation temperature, the catalyst device 3 is warmed up and the temperature of the catalyst is quickly increased to the predetermined activation temperature. It is necessary to raise it.

In the present embodiment, a cylinder 2c that performs rich combustion with more fuel Fu than the theoretical air-fuel ratio and a cylinder 2c that performs lean combustion with less fuel Fu than the theoretical air-fuel ratio are provided in the engine body 2 to warm the catalyst device 3. To work.
In the richly burning cylinder 2c, unburned gas containing carbon monoxide is generated. Then, the unburned gas is contained in the exhaust gas G 2, flows through the exhaust manifold 9, and is sent to the catalyst device 3.
Further, oxygen is generated in the lean-burning cylinder 2c (a lot of unburned oxygen is included). Unburned oxygen is contained in the exhaust gas G 2 and flows through the exhaust manifold 9 and is sent to the catalyst device 3.
In the catalyst device 3, oxidation heat is generated when carbon monoxide contained in the unburned gas is oxidized with oxygen. The oxidation heat generated at this time heats the catalyst of the catalyst device 3, and the catalyst device 3 is warmed up.

  In the case of the internal combustion engine 1 provided with the supercharger 7 driven by the exhaust gas G2, such as a turbocharger, the path from the engine body 2 to the catalyst device 3 is long and the catalyst device 3 is heated by the exhaust gas G2. Temperature does not rise easily. Therefore, a method of warming up the catalyst device 3 with heat of oxidation when carbon monoxide contained in the unburned gas is oxidized is effective.

As shown in FIG. 1B, when the cylinder numbers are assigned to the four cylinders 2c of the four-cylinder engine body 2 in the order of 1 to 4, the ECU 5 according to the present embodiment (see FIG. )), When warming up the catalyst device 3 (see FIG. 1A), for example, rich combustion is performed in the cylinder 2c (second cylinder 2c2) with the cylinder number 2 and the other cylinders 2c (first The air-fuel ratio A / F of each cylinder 2c is set so that lean combustion is performed in the cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4).
Then, the ECU 5 controls the injector 2b (see (a) of FIG. 1) of each cylinder 2c to adjust the fuel injection amount to each cylinder 2c so that each cylinder 2c is set to the set air-fuel ratio A / F.

With this configuration, when the carbon monoxide contained in the unburned gas generated in the second cylinder 2c2 is oxidized in the catalyst device 3 by the oxygen generated in the other cylinder 2c, heat of oxidation is generated, and the oxidation is performed. The catalyst device 3 can be warmed up by heat.
Hereinafter, the cylinder 2c that performs rich combustion (in this embodiment, the second cylinder 2c2) is referred to as a rich cylinder, and the cylinder 2c that performs lean combustion (in this embodiment, the first cylinder 2c1, the third cylinder 2c3, the fourth cylinder) 2c4) is referred to as a lean cylinder.

For example, when the 4-cylinder engine body 2 shown in FIG. 1B ignites in the order of the first cylinder 2c1, the second cylinder 2c2, the fourth cylinder 2c4, and the third cylinder 2c3, the rich in the second cylinder 2c2. When combustion is performed and lean combustion is performed in the other cylinders 2c (first cylinder 2c1, third cylinder 2c3, fourth cylinder 2c4), the engine body 2 switches between rich combustion and lean combustion.
Control of the engine body 2 that switches between rich combustion and lean combustion in this way is referred to as dither control.
Then, the ECU 5 shown in FIG. 1A dithers the engine body 2 to warm up the catalyst device 3.

When the engine body 2 is dither controlled, the ECU 5 increases the fuel injection amount to the second cylinder 2c2 (see FIG. 1B), which is a rich cylinder, more than the fuel injection amount at the ideal air-fuel ratio (stoichiometric). The fuel injection amount to the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 (see FIG. 1B), which are lean cylinders, is made smaller than the fuel injection amount in stoichiometry.
That is, the ECU 5 sets the fuel injection amount to each cylinder 2c so that the rich combustion and the lean combustion of the engine body 2 are switched, and injects the fuel Fu of the set fuel injection amount from the injector 2b to Dither control.

However, when the ECU 5 performs dither control on the engine body 2, if the output torque differs between the rich cylinder and the lean cylinder, torque fluctuation occurs in the engine body 2.
For example, the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 (see FIG. 1B) whose output torque of the second cylinder 2c2 that becomes a rich cylinder (see FIG. 1B) is a lean cylinder. When the output torque is larger than the output torque, the output torque of the engine body 2 pulsates so that the output torque periodically increases, and torque fluctuation occurs in the engine body 2.

  For example, the ECU 5 suitably adjusts the ignition timing of the second cylinder 2c2 (see FIG. 1B) that is a rich cylinder and the other cylinder 2c that is a lean cylinder (see FIG. 1B). By configuring, it is possible to suppress the occurrence of torque fluctuation in the engine body 2. However, it is necessary to create a map showing the detailed relationship between the air-fuel ratio A / F and the ignition timing, and it takes time to create the map.

  Therefore, the ECU 5 according to the present embodiment has the output torque of the second cylinder 2c2 (see FIG. 1 (b)) serving as the rich cylinder and the other cylinder 2c (see FIG. 1 (b)) serving as the lean cylinder. The air-fuel ratio A / F of each cylinder 2c is set so that the output torque becomes equal. Then, each cylinder 2c is set to the set air-fuel ratio A / F, and the engine body 2 is dither controlled so that torque fluctuation does not occur.

FIG. 2 is a graph showing the relationship between the output torque of the cylinder and the air-fuel ratio A / F. The vertical axis shows the output torque Trq of the cylinder 2c, and the horizontal axis shows the air-fuel ratio A / F.
As shown in FIG. 2, the air-fuel ratio A / F is divided into a lean injection side where the air-fuel ratio A / F is high and a rich injection side where the air-fuel ratio A / F is low, centering on stoichiometry.
On the other hand, the output torque Trq of each cylinder 2c (see FIG. 1A) is small on the rich injection side where the air-fuel ratio A / F is low, and increases as the air-fuel ratio A / F increases.
Then, it rises to the peak value on the rich injection side from the stoichiometry, and thereafter falls toward the lean injection side.
That is, the peak center of the output torque Trq is shifted to the rich injection side from the stoichiometry.

  For example, as shown in FIG. 2, there are two air-fuel ratios A / F (AF1, AF2) at which the output torque Trq becomes Tq1, AF1 is the air-fuel ratio A / F on the rich injection side from stoichiometric, and AF2 is from stoichiometric. In the case of the air-fuel ratio A / F on the lean injection side, if the rich cylinder is the air-fuel ratio AF1 and the lean cylinder is the air-fuel ratio AF2, the output torque Trq for both the rich cylinder and the lean cylinder becomes Tq1, and the rich cylinder and the lean cylinder The output torque Trq can be made equal.

  Therefore, the ECU 5 (see FIG. 1A) according to the present embodiment switches between rich combustion and lean combustion, for example, when the catalyst device 3 (see FIG. 1A) is warmed up. When the dither control is performed in FIG. 1 (a), the air-fuel ratio of each cylinder 2c (see FIG. 1 (a)) is set so that the output torque Trq of the lean cylinder and the output torque Trq of the rich cylinder become equal. A / F is set, and further, the fuel injection amount to each cylinder 2c is set according to the set air-fuel ratio A / F.

However, when the lean combustion and the rich combustion are switched by such dither control, when all the cylinders 2c (see FIG. 1A) are stoichiometric, the unburned gas concentration and the oxygen concentration in the exhaust gas G2 The ratio (the exhaust gas air-fuel ratio Ae / Fe) may be different.
That is, the air-fuel ratio Ae / Fe of the exhaust gas G2 may change by dithering the engine body 2 (see FIG. 1A).

The catalytic device 3 (see FIG. 1A) is most efficient when the air-fuel ratio Ae / Fe of the exhaust gas G2 generated when all the cylinders 2c (see FIG. 1A) are stoichiometric. The exhaust gas G2 is configured to be purified.
That is, it can be said that the state of the exhaust gas G2 generated when all the cylinders 2c are stoichiometric is stoichiometric of the air-fuel ratio Ae / Fe of the exhaust gas G2.
Therefore, when the air-fuel ratio Ae / Fe of the exhaust gas G2 is changed by the dither control, the air-fuel ratio Ae / Fe of the exhaust gas G2 is deviated from the stoichiometry, and the exhaust gas G2 cannot be purified efficiently by the catalyst device 3.

In the present embodiment, as shown in FIG. 1B, rich combustion is performed in the second cylinder 2c2, and lean combustion is performed in the other cylinders 2c (first cylinder 2c1, third cylinder 2c3, and fourth cylinder 2c4). .
Therefore, the ratio of the number of lean cylinders to rich cylinders is 3: 1.

Therefore, with the stoichiometric reference, the decrease in the air-fuel ratio A / F of the rich cylinder when the increase in the air-fuel ratio A / F of the lean cylinder is set to 1, and each cylinder 2c (FIG. 1) The air-fuel ratio A / F of each cylinder 2c is set so that the output torque Trq of (a) of FIG.
That is, in the number of rich cylinders that is 1/3 times that of the lean cylinder, the amount of change in the air-fuel ratio A / F from stoichiometry is set to three times the amount of change in the air-fuel ratio A / F of the lean cylinder.

  For example, as shown in FIG. 2, when the peak center of the output torque Trq is shifted by 10% from the stoichiometric side toward the rich injection side, 30 to 30 from the stoichiometric ratio among the combinations of air-fuel ratios A / F at which the output torque Trq becomes equal. The air-fuel ratio AF1 that becomes the% rich injection side and the air-fuel ratio AF2 that becomes the 10% lean injection side from the stoichiometry are selected.

That is, the ECU 5 shown in FIG. 1 (a) uses the fuel injection amount (hereinafter referred to as the rich fuel injection amount) to the second cylinder 2c2 (see FIG. 1 (b)), which is a rich cylinder, as the fuel in stoichiometry. It is set to 30% increase from the injection amount (hereinafter referred to as normal fuel injection amount).
By setting the rich fuel injection amount in this way, the air-fuel ratio A / F of the second cylinder 2c2 serving as the rich cylinder becomes the air-fuel ratio AF1 on the side of 30% rich injection from the stoichiometric.
Further, the ECU 5 is a fuel injection amount (hereinafter referred to as a lean fuel injection amount) to the cylinder 2c that is a lean cylinder (the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 shown in FIG. 1B). Is set to a 10% reduction from the normal fuel injection amount.
By setting the lean fuel injection amount in this way, the air-fuel ratio A / F of the cylinder 2c that becomes the lean cylinder becomes the air-fuel ratio AF2 on the lean injection side from the stoichiometric ratio.

As described above, when the rich fuel injection amount and the lean fuel injection amount are set, the increase amount from the normal fuel injection amount of the fuel injection amount to the second cylinder 2c2 (see FIG. 1B) that is a rich cylinder is increased. The fuel injection amount to the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 (see FIG. 1B), which are lean cylinders, is offset by a decrease amount from the normal fuel injection amount.
Therefore, the total amount of fuel injection into all cylinders 2c is equal to the total amount of fuel injection when all cylinders 2c are normal fuel injection amounts.
In other words, the total amount of fuel injection to all the cylinders 2c is equivalent to the total amount of fuel injection when all the cylinders 2c are stoichiometric, and the air-fuel ratio A / F of all the cylinders 2c is stoichiometric. It becomes a state that can be considered.
The air-fuel ratio Ae / Fe of the exhaust gas G2 generated in the engine body 2 is the same as the air-fuel ratio when the air-fuel ratios A / F of all the cylinders 2c are stoichiometric. That is, the air-fuel ratio Ae / Fe of the exhaust gas G2 becomes stoichiometric.

  Further, the air-fuel ratio AF1 of the rich cylinder at the set rich fuel injection amount and the air-fuel ratio AF2 of the lean cylinder at the set lean fuel injection amount are selected from combinations of air-fuel ratios A / F at which the output torque Trq is equivalent. Therefore, the second cylinder 2c2 (see (b) of FIG. 1) that is a rich cylinder and the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 (see FIG. 1) that are lean cylinders. 1 (see (b)) is equivalent to the output torque Trq.

Therefore, even if the engine main body 2 is dither controlled with the second cylinder 2c2 as a rich cylinder and the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 as a lean cylinder, the engine main body 2 can maintain the air-fuel ratio Ae / Fe. Exhaust gas G2 is exhausted.
That is, when the ECU 5 performs dither control of the engine body 2, the air-fuel ratio Ae / Fe of the exhaust gas G2 becomes stoichiometric.
Furthermore, the output torque Trq of all the cylinders 2c becomes equal.

As described above, the ECU 5 (see FIG. 1A) according to the present embodiment has a four-cylinder engine body 2 (FIG. 1) when warming up the catalyst device 3 (see FIG. 1A). When the dither control is performed with one cylinder 2c (see (a) of FIG. 1) being a rich cylinder, the air-fuel ratio AF1 on the injection side 30% richer than the stoichiometric ratio and the stoichiometric ratio from the combination of the air-fuel ratio A / F where the output torque Trq becomes equal. Accordingly, the air-fuel ratio AF2 on the 10% lean injection side is selected.
Then, the ECU 5 sets the rich fuel injection amount to be 30% higher than the normal fuel injection amount, and sets the air-fuel ratio A / F of the rich cylinder (second cylinder 2c2 shown in FIG. 1B) to the air-fuel ratio AF1. At the same time, the lean fuel injection amount is set to 10% lower than the normal fuel injection amount, and the air-fuel ratio A / of the lean cylinder (the first cylinder 2c1, the third cylinder 2c3, the fourth cylinder 2c4 shown in FIG. 1B) is set. Let F be the air-fuel ratio AF2.
As described above, the ECU 5 according to the present embodiment sets the air-fuel ratio Ae / Fe of the exhaust gas G2 so that the air-fuel ratio A / F of all the cylinders 2c (see FIG. 1A) can be regarded as stoichiometric. The engine body 2 can be dither controlled by stoichiometry.

  Further, the air-fuel ratio AF1 of the second cylinder 2c2 (see FIG. 1B) that is a rich cylinder and the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 that are lean cylinders (see FIG. 1B). ) Is the air / fuel ratio A / F selected from the combination of the air / fuel ratios A / F at which the output torque Trq is equal, the output torques Trq of all the cylinders 2c are equal. Therefore, torque fluctuation does not occur in the engine body 2.

Note that when the air-fuel ratio A / F of the rich cylinder is changed from the stoichiometric air-fuel ratio AF1 to the 30% rich injection side, and the air-fuel ratio A / F of the lean cylinder is changed from the stoichiometric air-fuel ratio AF2 to the 10% lean injection side. As shown in FIG. 2, the output torque Trq generated by each cylinder 2c (see FIG. 1A) is fixed at Tq1, so the output torque Trq of the engine body 2 (see FIG. 1A) is The output torque Tq1 generated by each cylinder 2c is fixed.
Therefore, the ECU 5 (see FIG. 1A) cannot adjust the output torque of the engine body 2 while the engine body 2 is dither controlled.

Therefore, the ECU 5 of the present embodiment shown in FIG. 1A is configured so that, for example, when the engine body 2 is in a state where the rotational speed is high and the intake pressure is high (high-speed rotation / high intake pressure state), It is determined that the required torque to the engine body 2 is high due to the driver's request, for example, in order to drive the equipped vehicle at high speed. And it is set as the structure which stops the dither control of the engine main body 2, and controls the engine main body 2 normally.
That is, when the driver runs the vehicle at a high speed, the vehicle is prioritized over the warm-up of the catalyst device 3. With this configuration, it is possible to prevent the traveling performance when the vehicle is traveling at high speed from being deteriorated due to warming up of the catalyst device 3.

When the engine main body 2 (see FIG. 1A) is in an idling state, the required torque (idle torque ATq) for the engine main body 2 travels by a vehicle equipped with the internal combustion engine 1 (see FIG. 1A). For example, the ECU 5 refers to the graph shown in FIG. 2 to set the air-fuel ratio A / F of the rich cylinder to the idle torque because it is lower than the required torque of the engine main body 2 (the engine main body 2 in the running state). The air-fuel ratio AF3 on the rich combustion side corresponding to ATq may be set, and the air-fuel ratio A / F of the lean cylinder may be set to the air-fuel ratio AF4 on the lean combustion side corresponding to the idle torque ATq.
That is, when the engine body 2 is in the idling state, the ECU 5 corrects the rich fuel injection amount and the lean fuel injection amount when the engine body 2 is in the traveling state, and the rich fuel injection amount when the engine body 2 is in the idling state. The lean fuel injection amount may be set.

  With this configuration, the ECU 5 shown in FIG. 1A can warm up the catalyst device 3 without increasing the rotational speed in the idling state when the engine body 2 is in the idling state. Therefore, consumption of the fuel Fu more than necessary can be suppressed.

For example, the ECU 5 is preferably configured to determine the state of the engine body 2 based on the rotational speed of the engine body 2 measured by a tachometer (not shown) and the intake pressure of the engine body 2 measured by an intake pressure gauge (not shown). is there.
In the case of this configuration, the ECU 5 refers to an engine state map 20 showing the state of the engine body 2 as shown in FIG. 3, and based on the rotational speed of the engine body 2 and the intake pressure of the engine body 2, The state of the main body 2 is determined.

As shown in FIG. 3, when the point indicating the rotational speed and the intake pressure of the engine body 2 (see FIG. 1A) is in the “idling state” region of the engine state map 20 (point P1), the ECU 5 (See (a) of FIG. 1) determines that the engine body 2 is in an idling state.
When the point indicating the rotational speed and the intake pressure of the engine body 2 is in the “traveling state” region of the engine state map 20 (point P2), the ECU 5 determines that the engine body 2 is in the traveling state.
Furthermore, when the point indicating the rotational speed and intake pressure of the engine body 2 is in the “high speed rotation / high intake pressure state” region, which is the region outside the “idling state” and “running state” of the engine state map 20. (Point P3), the ECU 5 determines that the engine body 2 is in the high speed rotation / high intake pressure state.
The engine state map 20 shown as an example in FIG. 3 is preferably created in advance based on the performance of the engine body 2 and stored in a ROM (not shown) of the ECU 5.

When the ECU 5 (see FIG. 1A) determines that the engine body 2 (see FIG. 1A) is in the idling state based on the engine state map 20, the engine body 2 is in the running state. The rich fuel injection amount at this time is corrected, and the rich fuel injection amount is set so as to realize the rich combustion side air-fuel ratio AF3 corresponding to the idle torque ATq obtained by referring to the graph shown in FIG.
If the air-fuel ratio AF3 is the air-fuel ratio A / F on the X% rich injection side from the stoichiometric, the ECU 5 sets the rich fuel injection amount to be X% higher than the normal fuel injection amount, and the air-fuel ratio A / F of the rich cylinder is stoichiometric. To X% rich injection side.
The value of X% is a characteristic value of the engine main body 2 determined based on the relationship between the idle torque ATq and the air / fuel ratio A / F.

Further, the ECU 5 corrects the lean fuel injection amount when the engine body 2 is in the traveling state, and realizes the lean combustion side air-fuel ratio AF4 corresponding to the idle torque ATq obtained by referring to the graph shown in FIG. The lean fuel injection amount is set as follows.
If the air-fuel ratio AF4 is the air-fuel ratio A / F on the Y% lean injection side from the stoichiometric, the ECU 5 sets the lean fuel injection amount to Y% less than the normal fuel injection amount, and the stoichiometric air-fuel ratio A / F of the lean cylinder is set. To Y% lean injection side.
The value of Y% is a characteristic value of the engine main body 2 determined based on the relationship between the idle torque ATq and the air-fuel ratio A / F.

In this embodiment, the ECU 5 shown in FIG. 1A refers to the engine state map 20 based on the rotational speed of the engine body 2 and the intake pressure, and determines that the engine body 2 is in an idling state. . When it is determined that the engine body 2 is in the idling state, the rich fuel injection amount and the lean fuel injection amount when the engine body 2 is in the traveling state are corrected.
Therefore, the ECU 5 according to the present embodiment corrects the fuel injection amount based on the rotation speed of the engine body 2 and the intake pressure.

  When the ECU 5 determines that the engine body 2 is in the high speed rotation / high intake pressure state based on the engine state map 20, the ECU 5 stops the dither control of the engine body 2 for warming up the catalyst device 3. Normally, the engine body 2 is controlled.

With reference to FIG. 4, a procedure (hereinafter referred to as a warm-up procedure) in which the ECU 5 (see FIG. 1A) warms up the catalyst device 3 will be described (see FIGS. 1 to 3 as appropriate).
The warm-up procedure may be configured to be incorporated as a subroutine in a program executed by the ECU 5 and executed appropriately by the ECU 5, for example.

When the ECU 5 does not start warming up of the catalyst device 3 (step S1 → No), the ECU 5 ends the warming up procedure and returns, but when starting warming up of the catalyst device 3 (step S1 → Yes). Then, it is determined whether the engine body 2 is in a high speed rotation / high intake pressure state (step S2).
The method for determining whether or not the ECU 5 starts to warm up the catalyst device 3 in step S1 is not limited. For example, when the internal combustion engine 1 includes a thermometer (not shown) that measures the temperature of the catalyst device 3 and the temperature of the catalyst device 3 measured by the thermometer (not shown) is lower than a predetermined value that is set in advance, the catalyst device 3 Is determined to start warming up (step S1 → Yes).

  In step S2, the ECU 5 determines the engine state map based on the rotational speed of the engine body 2 measured by a tachometer (not shown) and the intake pressure of the engine body 2 measured by an intake pressure gauge (not shown) as described above. 20, it is determined whether the engine body 2 is in a high speed rotation / high intake pressure state.

  When the engine body 2 is in a high speed rotation / high intake pressure state (step S2 → Yes), the ECU 5 causes the engine body 2 to rotate at a high speed / high suction in order to drive the vehicle equipped with the internal combustion engine 1 at a high speed. It is determined that the engine is in the atmospheric pressure state, and the warm-up procedure is terminated and the process returns. If the engine body 2 is not in the high speed rotation / high intake pressure state (step S2 → No), is the engine body 2 in the idling state? It is determined whether or not (step S3).

As described above, the ECU 5 refers to the engine state map 20 shown in FIG. 3 and determines the state of the engine body 2 based on the rotational speed of the engine body 2 and the intake pressure.
When it is determined that the engine body 2 is not in the idling state (step S3 → No), the ECU 5 determines that the engine body 2 is in the traveling state. Then, the ECU 5 increases the rich fuel injection amount by 30% of the normal fuel injection amount (step S4), and decreases the lean fuel injection amount by 10% of the normal fuel injection amount (step S5).

  Then, the ECU 5 controls each injector 2b to inject the fuel Fu with the set rich fuel injection amount into the second cylinder 2c2, and inject the fuel Fu with the set lean fuel injection amount into the other cylinders 2c. .

The rich fuel injection amount that is 30% increase of the normal fuel injection amount is injected into the second cylinder 2c2, and rich combustion is performed, and the normal fuel injection is injected into the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4. A lean fuel injection amount that is a 10% reduction in the amount is injected and lean combustion occurs.
Then, the carbon monoxide contained in the unburned gas generated in the second cylinder 2c2 that performs rich combustion, and the oxygen generated in the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 that perform lean combustion include the catalyst device 3. Oxidation reaction generates heat of oxidation and warms up the catalyst device 3.

  On the other hand, when the ECU 5 determines that the engine main body 2 is in the idling state (step S3 → Yes), the rich fuel injection amount is increased by X% of the normal fuel injection amount (step S6), and the lean fuel injection amount is set as the normal fuel. The injection amount is reduced by Y% (step S7).

As described above, when the engine body 2 is in the idling state, the ECU 5 corresponds to the air-fuel ratio AF3 of the second cylinder 2c2 that is a rich cylinder corresponding to the idle torque ATq, and the first cylinder 3c1 and the third cylinder 2c3 that are lean cylinders. , And the air-fuel ratio AF4 of the fourth cylinder 2c4 are set.
Then, the carbon monoxide contained in the unburned gas generated in the second cylinder 2c2 that performs rich combustion, and the oxygen generated in the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 that perform lean combustion include the catalyst device 3. Oxidation reaction generates heat of oxidation and warms up the catalyst device 3.
Further, when the engine body 2 is idling, the ECU 5 can dither control the engine body 2 while maintaining the torque of the engine body 2 at the idle torque ATq.
Therefore, the engine body 2 is dither controlled without increasing the rotation speed, and the consumption of fuel Fu more than necessary can be suppressed.

  Note that the air-fuel ratio AF3 of the rich cylinder and the air-fuel ratio AF4 of the lean cylinder when the engine body 2 is in the idling state are based on the output torque ATq and the like when the engine body 2 is in the idling state from the graph shown in FIG. The value is set in advance.

  Then, the ECU 5 controls each injector 2b to inject the fuel Fu with the set rich fuel injection amount into the second cylinder 2c2, and inject the fuel Fu with the set lean fuel injection amount into the other cylinders 2c. .

As described above, the ECU 5 of the internal combustion engine 1 according to the present embodiment shown in FIG. 1A is configured so that the rich combustion and the lean combustion are switched when the catalyst device 3 is warmed up. The catalyst device 3 is warmed up by heat of oxidation when carbon monoxide contained in the unburned gas generated in the rich cylinder is oxidized in the catalyst device 3 by oxygen generated in the lean cylinder.
As described above, when the ECU 5 performs dither control of the engine body 2, if the output torque Trq of the rich cylinder and the lean cylinder are different, torque fluctuation occurs in the engine body 2. However, the ECU 5 according to the present embodiment By setting the air-fuel ratio A / F of each cylinder 2c so that the torque Trq and the output torque Trq of the lean cylinder are equal, it is possible to suitably suppress occurrence of torque fluctuation in the engine body 2. There is an effect.

Further, the ECU 5 according to this embodiment sets the fuel injection amount to each cylinder 2c according to the number of rich cylinders and lean cylinders.
As shown in FIG. 1B, in the case of a four-cylinder engine body 2 having four cylinders 2c, that is, a first cylinder 2c1, a second cylinder 2c2, a third cylinder 2c3, and a fourth cylinder 2c4, the ECU 5 is For example, dither control is performed so that rich combustion is performed in the second cylinder 2c2 and lean combustion is performed in the other cylinders 2c.

At this time, since the ratio of the number of lean cylinders to rich cylinders is 3: 1, as shown in FIG. 2, when the peak center of the output torque Trq is shifted by 10% from the stoichiometric side toward the rich injection side, the ECU 5 ( In FIG. 1 (a), among the combinations of the air-fuel ratios A / F at which the output torque Trq becomes equal, the air-fuel ratio AF1 that is 30% rich from the stoichiometric side and the 10% lean injection side from the stoichiometric side The air-fuel ratio AF2 is selected. Then, the ECU 5 increases the rich fuel injection amount to the second cylinder 2c2 that performs rich combustion (see FIG. 1B) by 30% of the normal fuel injection amount, and the other cylinder 2c that performs lean combustion ((( The lean fuel injection amount to (b) is reduced by 10% of the normal fuel injection amount.
As a result, the air-fuel ratio A / F of all the cylinders 2c can be regarded as stoichiometric, and the air-fuel ratio Ae / Fe of the exhaust gas G2 can be stoichiometric.
And the outstanding effect that the carbon monoxide of the unburned gas contained in exhaust gas G2 can be efficiently oxidized with the catalyst apparatus 3 is produced.
Further, an excellent effect is obtained in that the output torques Trq of all the cylinders 2c can be made equal.

In the present embodiment, the rich combustion cylinder 2c is the second cylinder 2c2 shown in FIG. 1B, but one of the first cylinder 2c1, the third cylinder 2c3, and the fourth cylinder 2c4 is rich combustion. Needless to say, it may be configured to do so.
Further, the cylinder 2c that performs rich combustion may be different every time the ignition of all the cylinders 2c makes one round without fixing the cylinder 2c that performs rich combustion.
For example, when the 4-cylinder engine main body 2 shown in FIG. 1B first ignites from the first cylinder 2c1 to the third cylinder 2c3, the second cylinder 2c2 performs rich combustion, and then from the first cylinder 2c1 to the first cylinder 2c1. When igniting up to three cylinders 2c3, the cylinder 2c that performs rich combustion may be different so that the third cylinder 2c3 performs rich combustion.

  Further, in the graph shown in FIG. 2, when the deviation from the stoichiometric peak center of the output torque Trq is not 10%, the output torque Trq is equal when the ratio of the number of lean cylinders to rich cylinders is 3: 1. And the air-fuel ratio A / F of the rich cylinder and the lean so that the increase in the rich fuel injection amount from the normal fuel injection amount is three times the decrease in the lean fuel injection amount from the normal fuel injection amount. What is necessary is just to set the air-fuel ratio A / F of a cylinder.

Furthermore, for example, the present invention can be applied to an internal combustion engine 1 including a 6-cylinder or 8-cylinder engine body 2.
In the case of a 6-cylinder or 8-cylinder engine body 2, when the ratio of the number of lean cylinders to rich cylinders is m: n, the output torque Trq is equal, and the rich fuel injection amount is calculated from the normal fuel injection amount. The rich fuel injection amount and the lean fuel injection amount may be set so that the increase amount of the fuel is m / n times the decrease amount of the lean fuel injection amount from the normal fuel injection amount.
With this configuration, the increase amount of the rich fuel injection amount from the normal fuel injection amount can be offset by the decrease amount of the lean fuel injection amount from the normal fuel injection amount, and the air-fuel ratio A / F of all the cylinders 2c. Can be considered to be stoichiometric. Then, the air-fuel ratio Ae / Fe of the exhaust gas G2 can be stoichiometric.
Furthermore, dither control can be performed without generating torque fluctuations in the engine body 2.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Engine main body 2c Cylinder 3 Catalytic device 5 ECU (control device)
8 Intake manifold 9 Exhaust manifold (exhaust pipe)
G2 exhaust gas

Claims (4)

The engine body,
A catalyst device disposed in an exhaust pipe of the engine body for purifying exhaust gas;
Oxygen and unburned gas are included in the exhaust gas by dither control to set the fuel injection amount to each cylinder so that rich combustion and lean combustion are switched, and the reaction between the oxygen and the unburned gas is performed. In an internal combustion engine configured to include a control device that warms up the catalyst device with heat,
The controller is
An internal combustion engine, wherein an amount of fuel injection to each cylinder is set so that an output torque of the cylinder that performs rich combustion is equal to an output torque of the cylinder that performs lean combustion.   2. The internal combustion engine according to claim 1, wherein one of the plurality of cylinders included in the engine body is a rich cylinder that performs rich combustion, and the other is a lean cylinder that performs lean combustion. When the control device dither-controls the engine body,
The internal combustion engine according to claim 1 or 2, wherein an air-fuel ratio of the exhaust gas sent from the engine body to the catalyst device is stoichiometric. The controller is
The internal combustion engine according to any one of claims 1 to 3, wherein a fuel injection amount to each of the cylinders is corrected based on a rotation speed and an intake pressure of the engine body.

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