JP2914045B2 - Catalyst warm-up 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 catalyst warm-up device for an internal combustion engine for realizing early warm-up of a catalytic converter provided in an exhaust system.

[0002]

2. Description of the Related Art In general, a catalytic converter provided in an exhaust system of an internal combustion engine raises a catalyst temperature by exhaust gas and, when activated, sufficiently purifies harmful components in the exhaust gas. It is. As a result, during the period from the start of the engine to the time when the catalyst temperature is increased by the exhaust gas, the harmful components in the exhaust gas are released to the atmosphere without being sufficiently purified, and contribute to air pollution. There is a need for early warm-up of the catalytic converter at times.

[0003] Prior to activation of the catalyst, secondary air is supplied upstream of the catalytic converter in the engine exhaust system, and unburned fuel in the exhaust gas is ignited by an ignition plug together with this air and burned. Although a catalyst warm-up device intended to warm up early is known, it is difficult to reliably burn the unburned fuel due to its small amount. Japanese Patent Application No. 3-85430 proposes a catalyst warming-up device for supplying hydrogen, which is a combustible, in order to ensure the combustion upstream of the catalytic converter.

[0004]

According to the above-mentioned prior art, the early warm-up of the catalytic converter before the activation of the catalyst can be surely realized. However, two methods for supplying secondary air and hydrogen to the engine exhaust system are required. The necessity of the device causes a considerable increase in cost.

Accordingly, it is an object of the present invention to provide a catalyst warm-up device for an internal combustion engine that enables reliable early warm-up of a catalytic converter before activation of a catalyst without significantly increasing costs.

[0006]

According to the first aspect of the present invention, a catalyst warm-up device for an internal combustion engine is provided with a catalytic converter provided in an exhaust system of the internal combustion engine and an ignition provided in the exhaust system upstream of the catalytic converter. A plug, a combustible material supply means for supplying a combustible material to the vicinity of the ignition plug, and the combustible material so that the combustible material is supplied to the vicinity of the ignition plug when a catalyst temperature of the catalytic converter is equal to or lower than a predetermined value. A first control means for controlling a material supply means, and a second control means for controlling the ignition plug so that ignition is performed when the combustible material is supplied to the vicinity of the ignition plug, wherein the combustible material is provided. Is supplied to the vicinity of the ignition plug, the mixture in the combustion chamber is set to be leaner than the stoichiometric air-fuel ratio.

The catalyst warming device for a second internal combustion engine according to the present invention is the catalyst warming device for the first internal combustion engine, wherein the combustible material is supplied to the vicinity of the spark plug.
The fuel cell system further comprises third control means for increasing the amount of intake air supplied to the combustion chamber as compared to when the combustibles are not supplied to the vicinity of the ignition plug.

[0008] The catalyst warm-up device for a third internal combustion engine according to the present invention is the catalyst warm-up device for the second internal combustion engine, wherein the combustible material is supplied to the vicinity of the spark plug.
The fuel injection amount is determined based on the engine operating state excluding the intake air amount.

[0009]

According to the above-described catalyst warm-up device for the first internal combustion engine, when the catalyst temperature of the catalytic converter is equal to or lower than the predetermined value, the first control means causes the combustible material supply means to remove the combustible material upstream of the exhaust system catalytic converter. Is supplied to the vicinity of the ignition plug provided at the same time, and at the same time, ignition by the ignition plug is executed by the second control means. At this time, the mixture in the combustion chamber is set to be leaner than the stoichiometric air-fuel ratio. Upstream of the catalytic converter in the exhaust system, the combustibles are ignited by the spark plug together with the air not used for combustion in the combustion chamber and are reliably burned, and the heat of the combustible material quickly warms up the catalytic converter.

According to the catalyst warm-up device for the second internal combustion engine described above, the third control means controls the time when the combustible material is supplied near the spark plug when the combustible material is not supplied near the spark plug. In order to increase the amount of intake air supplied to the combustion chamber, the combustibles are ignited by the spark plug together with the air not used for combustion in the combustion chamber, and are reliably burned, and the heat is used to quickly warm up the catalytic converter. Is realized, and when the combustibles are not supplied to the vicinity of the ignition plug, the optimal air-fuel ratio can be set according to the operating state of the engine.

According to the third catalyst warm-up device for an internal combustion engine, when the combustible is supplied to the vicinity of the ignition plug, the fuel injection amount is determined based on the engine operating state excluding the intake air amount. The third control means increases the amount of intake air supplied to the combustion chamber when the combustible is supplied near the spark plug compared to when the combustible is not supplied near the spark plug;
The combustibles are ignited by the ignition plug together with the air not used for combustion in the combustion chamber and are reliably burned, and the heat allows for early warm-up of the catalytic converter. At this time, the engine speed is prevented from increasing.

[0012]

FIG. 1 is a schematic view showing an entire internal combustion engine provided with a catalyst warm-up device according to the present invention. In the figure,
1 is an engine, 2 is an exhaust passage, and 3 is an intake passage. The engine 1 is a lean burn engine that achieves low fuel consumption. A catalytic converter 4 for purifying harmful components in the exhaust gas is arranged in the exhaust passage 2, and an ignition plug 5 is installed upstream of the catalytic converter 4. A hydrogen generator 6 for generating combustible hydrogen by electrolysis of water or the like is provided. The hydrogen generator 6 and a spark plug 5 in the exhaust passage 2 are provided.
The vicinity is connected by a hydrogen supply passage 8 having an electromagnetic valve 7.

The intake passage 3 has a throttle valve 9 upstream of the surge tank 3a and communicates with an air cleaner 10, between which an air flow meter 1 for detecting the amount of intake air.
1 is provided. A control device 14 is provided which is responsible for ignition control of the spark plug 5, opening / closing control of the solenoid valve 7, and control of the opening degree of the throttle valve 9 via a drive device 13. The control device 14 includes the air flow meter 11 described above. Besides, a cooling water temperature sensor 15 for detecting the engine cooling water temperature, and a catalyst temperature sensor 1 for detecting the catalyst temperature of the catalytic converter 4
6, a rotation sensor (not shown) for detecting the engine speed, and the like are electrically connected.

The control device 14 executes the ignition control of the ignition plug 5 and the opening / closing control of the solenoid valve 7 in accordance with the first flowchart shown in FIG. 2 during the period from the start of the engine to the start of the vehicle. The throttle valve 9 opening control, engine fuel injection amount control, and engine ignition timing control are executed according to the second flowchart. Also,
Subsequent control of the engine fuel injection amount is executed based on the intake air amount detected from the air flow meter 11 so as to obtain an optimum air-fuel ratio for each operation state.

First, in step 101, it is determined whether or not the current rotational speed N obtained from the rotational sensor is equal to or higher than a predetermined rotational speed N '(for example, 500 rpm) indicating that the engine has been started. .
When this determination is affirmed, the routine proceeds to step 102, where the catalyst temperature T is detected using the catalyst temperature sensor 16, and it is determined whether or not this temperature T is equal to or higher than the catalyst activation temperature T '. When this determination is denied, it is determined in step 103 whether the elapsed time t after the completion of the engine start has reached a predetermined value t '. The predetermined time t ′ is a time during which the hydrogen generator 8 can supply hydrogen.

If this determination is denied, step 104
, The flag F is set to 1. Then step 1
At 05, the solenoid valve 7 is opened, hydrogen is supplied from the hydrogen generator 8 to the vicinity of the ignition plug 5 in the exhaust passage 2, and at step 106, ignition of the ignition plug 5 is performed. On the other hand, when the determination in step 102 or 103 is affirmative, that is, when it is not necessary to warm up the catalyst, or when the elapsed time t has reached the predetermined value t ′, step 10
At 7, the flag F is set to 2. Then step 1
In step 08, the electromagnetic valve 7 is closed, the supply of hydrogen to the vicinity of the ignition plug 5 in the exhaust passage 2 is stopped, and in step 109, the ignition of the ignition plug 5 is stopped.

If the determination in step 101 is negative, that is, if the engine is being started, step 110 is executed.
Then, the flag F is set to 0, and the above-described processing from step 108 is performed.

Next, the second flowchart will be described. First, in step 201, it is determined whether or not the flag F set to each value in the first flowchart is 0. When this determination is affirmative, that is, during engine startup, in step 202, the fuel injection amount τ is determined based on the current rotational speed N, and then, in step 203, the engine temperature is measured using the cooling water temperature sensor 15. Expressed cooling water temperature TH
W is detected, and the air-fuel ratio A / F of the air-fuel mixture is determined based on the cooling water temperature THW at this time. The air-fuel ratio A / F is set to a value near the stoichiometric air-fuel ratio in order to ensure starting, and is set to a slightly rich side due to a decrease in the cooling water temperature THW.

Next, in step 204, the opening degree θ of the throttle valve 9 is determined in consideration of the fuel injection amount τ at this time so that the air-fuel ratio A / F is obtained. The ignition timing A is determined.

On the other hand, when the determination in step 201 is denied, that is, after the engine start is completed, step 206
, The fuel injection amount τ is determined based on the current rotational speed. Then, in step 207, it is determined whether the flag F is 1. When this determination is affirmed, that is, when hydrogen is being supplied to the exhaust passage 2, the routine proceeds to step 208, where the air / fuel ratio A / A is determined based on the cooling water temperature THW at this time from the map M1 shown by the solid line in FIG. Determine F and step 2
In step 09, the opening degree θ of the throttle valve 9 is determined so as to achieve the air-fuel ratio A / F in consideration of the fuel injection amount τ at this time. In step 210, the optimum ignition timing A at this time is determined. You.

When the determination in step 207 is denied, that is, when the supply of hydrogen to the exhaust passage 2 is stopped, the process proceeds to step 211, and the cooling at this time is determined from the map M2 shown by the dotted line in FIG. The air-fuel ratio A / F is determined based on the water temperature THW, and in step 212, the opening degree θ of the throttle valve 9 is determined so as to become the air-fuel ratio A / F in consideration of the fuel injection amount τ at this time. In step 213, the optimum ignition timing A at this time is determined.

Map M2 used in step 211
Is a map of an air-fuel ratio generally used in idling operation after completion of engine start in a normal lean-burn engine. The stoichiometric air-fuel ratio is set so that the cooling water temperature THW is reduced to a relatively low first predetermined cooling water temperature THW1. The air-fuel ratio is set so that the air-fuel ratio gradually rises above that. The map M1 used in step 208 indicates that the cooling water temperature THW is a relatively high second predetermined cooling water temperature THW2.
In the above, it is set the same as the map M2, but below that, it is set to the value at the second cooling water temperature THW2 in the map M2. Further, the engine ignition timing suitable for the air-fuel ratio determined in each map is determined so as to be advanced as the air-fuel ratio is higher, that is, the leaner, so as to prevent deterioration of combustion.

According to these controls, the air-fuel ratio control and the ignition timing control optimal for the start are performed until the start of the engine 1 is completed, and the start can be ensured. Further, in the idling operation state after the start of the vehicle until the vehicle starts moving, if the catalyst temperature is low and the catalyst is in an inactive state at this time, the vicinity of the ignition plug 5 provided upstream of the catalytic converter 4 in the exhaust passage 2 is provided. Is supplied with hydrogen. Since the air-fuel ratio at this time is controlled to be always lean by the map M1, air not used for combustion of the engine 1 is discharged together with the exhaust gas, and this air is discharged by the ignition plug 5 together with the aforementioned hydrogen. The catalyst is ignited and burned, and the heat instantaneously heats the catalyst. At this time, the fuel injection amount τ is determined based on the engine speed, and the increase in the intake air amount makes the air-fuel ratio of the air-fuel mixture lean, thereby preventing the engine speed from lowering. You.

Next, when the catalyst reaches the activation temperature or reaches the hydrogen supply possible time depending on the performance of the hydrogen generator 6, the supply of hydrogen to the exhaust passage 2 is stopped.
The ignition by the ignition plug 5 is also stopped. The air-fuel ratio at this time is determined by a general control (leave M
It is determined according to 2), and it is on the stoichiometric air-fuel ratio side as compared to when hydrogen is supplied. In particular, when the cooling water temperature is low, the operation based on the stoichiometric air-fuel ratio is performed. As a result, when the catalyst is not at the activation temperature, the amount of air not used for combustion in the exhaust gas is reduced, so that the exhaust gas temperature can be increased accordingly, and further heating of the catalyst becomes possible. . Further, even if the air-fuel ratio control based on the map M2 is omitted and a lean-burn engine in which the air-fuel ratio control based on the map M1 is performed until the vehicle starts is used, reliable combustion of hydrogen in the exhaust passage is guaranteed. Early warm-up of the catalyst is achieved.

It is very difficult to burn unburned fuel in the engine combustion chamber in the exhaust passage 2 using the spark plug 5 for warming up the catalyst because the amount of unburned fuel is small. However, by newly supplying a combustible material such as hydrogen as in the present embodiment, the combustion in the exhaust passage becomes reliable, and at this time, the unburned fuel described above is simultaneously burned, and The amount of unburned fuel, which is a harmful component of, can be significantly reduced.

Although hydrogen is used as a combustible in this embodiment, it is clear that other combustibles can be used. Further, the air-fuel ratio control at the time of supplying hydrogen is performed only with the intake air amount instead of the fuel injection amount in order to maintain the rotation speed, but the opening degree of the throttle valve 9 increases with the increase of the intake air amount. Therefore, considering that the pumping loss of the engine piston is reduced, the fuel injection amount can be reduced accordingly.

Of course, in the air-fuel ratio control at the time of supplying hydrogen, instead of controlling the opening of the throttle valve 9, an idle speed control valve that bypasses the throttle valve 9 may be provided and controlled. It is.

[0028]

As described above, according to the catalyst warm-up device for an internal combustion engine according to the present invention, by supplying combustibles to the exhaust passage, combustion in the exhaust passage for warming up the catalyst can be ensured. At this time, the required air can be obtained by making the air-fuel ratio in the engine combustion chamber leaner than the stoichiometric air-fuel ratio.
Since the air not used for the combustion is used, a secondary air supply device to the exhaust passage is not required, and the cost can be reduced accordingly. Also, when supplying combustibles, the amount of intake air supplied to the engine combustion chamber is increased, and the air-fuel ratio is made thinner so that combustibles can be burned. Can be operated. Further, at the time of supplying the combustibles, the fuel injection amount is determined based on the engine operation state excluding the intake air amount, and the amount is increased only by the intake air amount. The amount is not increased, and an increase in the number of revolutions can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall schematic view of an internal combustion engine equipped with a catalyst warm-up device according to the present invention.

FIG. 2 is a first flowchart for control.

FIG. 3 is a second flowchart for control.

FIG. 4 is a map for determining an air-fuel ratio used in a second flowchart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Exhaust passage 4 ... Catalytic converter 5 ... Spark plug 6 ... Hydrogen generator 7 ... Control valve 8 ... Hydrogen supply device 9 ... Throttle valve 14 ... Control device 15 ... Cooling water temperature sensor 16 ... Catalyst temperature sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-191411 (JP, A) JP-A-4-116218 (JP, A) JP-A-51-23622 (JP, U) Field (Int.Cl. ⁶ , DB name) F01N 3/36 F01N 3/20 F02D 41/04 305

Claims (3)

(57) [Claims] 1. A catalytic converter provided in an exhaust system of an internal combustion engine, an ignition plug provided upstream of the catalytic converter in the exhaust system, and a combustible material supply means for supplying a combustible material near the ignition plug. First control means for controlling the combustible material supply means such that the combustible material is supplied to the vicinity of the spark plug when the catalyst temperature of the catalytic converter is equal to or lower than a predetermined value; and Second control means for controlling the ignition plug so that ignition is performed when the combustible is supplied to the vicinity of the ignition plug. A catalyst warm-up device for an internal combustion engine, wherein the catalyst warm-up device is set leaner than the fuel ratio. 2. A third control for increasing the amount of intake air supplied to the combustion chamber when the combustible is supplied near the ignition plug, compared to when the combustible is not supplied near the ignition plug. The catalyst warm-up device for an internal combustion engine according to claim 1, further comprising: means. 3. The internal combustion engine according to claim 2, wherein when the combustible is supplied to the vicinity of the ignition plug, a fuel injection amount is determined based on an engine operating state excluding an intake air amount. Catalyst warm-up device.