JPH11311119A - Secondary air supplier for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exhaust emission control by setting up the temperature of a catalyst controlling the exhaust of an operating cylinder, to a proper range in this device which stops a supply of fuel to a partial cylinder, making this cylinder suspendible, and uses the exhaust out of this suspended cylinder as secondary air to be fed to an exhaust passage of the operating cylinder. SOLUTION: A flow regulating valve 11 to be controlled by a controller 9 inputting a signal out of a sensor 12 detecting a catalyst temperature T is interposingly installed in a secondary air passage 5, and the discharge of air flowing into the secondary air passage 5 is controlled according to the catalyst temperature T. In addition, at the specified period of time after stopping a supply of fuel to a cylinder 21 , exhaust gas out of this suspended cylinder 21 is introduced into the secondary air passage 5, whereby any exhaust gas mixed with residual fuel is prevented from being fed to an operating cylinder 22 in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary air supply device for supplying secondary air to an exhaust passage upstream of a catalyst of an internal combustion engine and secondary-burning the exhaust gas to promote activation of the catalyst. The present invention relates to a secondary air supply device applied to an internal combustion engine in which fuel supply to some cylinders is stopped and the cylinders can be deactivated.

[0002]

2. Description of the Related Art A general secondary air supply device for an internal combustion engine is provided with a dedicated air pump such as an electric type for supplying secondary air, but the fuel supply to some cylinders is stopped. In the internal combustion engine in which some of the cylinders can be deactivated, the deactivated cylinder functions as an air pump to discharge air to the exhaust passage.

Conventionally, focusing on this point, a secondary air passage branched from the exhaust passage of some of the cylinders that can be stopped and connected to the exhaust passage of the other cylinder upstream of the exhaust purification catalyst is provided. When fuel supply to some of the cylinders is stopped, exhaust gas from some of the cylinders is introduced into the secondary air passage, and is supplied as secondary air to the exhaust passage of the other cylinder. An unnecessary secondary air supply device has been proposed (see JP-A-8-334016).

[0004]

In the above-mentioned prior art, when fuel supply to some of the cylinders is stopped, all of the exhaust gas (secondary air) from the cylinder flows into the exhaust passage of another cylinder. Excessive or insufficient supply of the secondary air may cause the catalyst temperature to deviate from the proper range of the catalyst purification performance, and deteriorate the exhaust emission.

In view of the above, the present invention has been made to improve the exhaust emission by controlling the catalyst temperature so as to be in an appropriate range of the catalyst purification performance in a secondary air supply device using a stopped cylinder as an air pump. It is an issue.

[0006]

Means for Solving the Problems In order to solve the above problems,
The present invention is a secondary air supply device for an internal combustion engine capable of stopping fuel supply to some cylinders and suspending some cylinders, wherein the secondary air supply device is branched from an exhaust passage of the some cylinders. A secondary air passage connected upstream of the exhaust gas purifying catalyst in an exhaust passage of another cylinder is provided, and when the fuel supply to some of the cylinders is stopped, exhaust gas from some of the cylinders In the apparatus for introducing into the passage and supplying it to the exhaust passage of the other cylinder as secondary air, a flow control means for controlling a flow rate of air flowing through the secondary air passage in accordance with a catalyst temperature is provided.

According to this, the flow rate of the secondary air is controlled in accordance with the catalyst temperature, the catalyst temperature can be maintained in a proper range of the catalyst purification performance, and the exhaust emission can be improved. Also, deterioration of the catalyst can be prevented.
It is desirable to use the actual detected temperature of the exhaust purification catalyst as the catalyst temperature as a parameter for controlling the flow rate of the secondary air, but it is also possible to use the catalyst temperature estimated from the engine water temperature and the like.

By the way, even if the cylinder is stopped by stopping the fuel supply, the fuel remaining in the intake passage or the like is mixed into the exhaust from the stopped cylinder, and the exhaust is supplied to the exhaust passage of the working cylinder. Exhaust emissions deteriorate. in this case,
At a predetermined time after stopping the fuel supply to some of the cylinders, exhaust from the some of the cylinders is introduced into the secondary air passage, and the predetermined time is set to a time when the discharge of the residual fuel is completed. If it is set, exhaust mixed with fuel can be prevented from being supplied to the exhaust passage of the working cylinder, and the exhaust emission can be further improved.

Further, there is a possibility that secondary air will be continuously supplied even if the catalyst temperature becomes high due to a failure of the flow control means. In this case, when the state in which the catalyst temperature is equal to or higher than the predetermined temperature continues for a predetermined period, the introduction of the exhaust gas from the partial cylinders into the secondary air passage is stopped, so that the flow rate control means may fail. Even if the supply of secondary air is stopped, the catalyst temperature can be lowered to an appropriate range, and fail-safe operation can be achieved.

[0010]

Figure 1 DETAILED DESCRIPTION OF THE INVENTION shows an internal combustion engine comprising a V-type 6-cylinder engine, the first exhaust in the first exhaust passage 3 ₁ connecting to three cylinders 2 of the _first bank 1 ₁ of the engine the purification catalyst 4 ₁ interposed, and the second bank 1 ₂ 3 of the engine
A second exhaust passage 3 ₂ leading to number of cylinders 2 ₂ is interposed a second exhaust gas purifying catalyst 4 _2.

Each of the cylinders 2 ₁ and 2 ₂ is supplied with fuel from a fuel injection valve (not shown).
By stopping fuel supply to the cylinders 2 ₁ bank 1 ₁ the gas cylinder 2 ₁
To be able to pause.

[0012] pauses cylinders 2 of the _first bank 1 _1, the gas cylinder 2 ₁ air to the first exhaust passage 3 ₁ to function as an air pump is discharged. Therefore, the secondary air passage 5 connected to the branch has been second second exhaust purification catalyst 4 ₂ upstream portion of the exhaust passage 3 ₂ from the first exhaust passage 3 ₁ is provided, the first bank 1
When the fuel supply stop to the _first cylinder 2 _1, and the exhaust from the gas cylinder 2 ₁ to be supplied as secondary air to the second exhaust passage 3 _2.

[0013] The first exhaust passage 3 _1, open position to open the passage 3 ₁ (position of the imaginary line shown), and a freely switch closed position to block the passage 3 ₁ (indicated by a solid line position) off valve 6 is provided, the secondary air passage 5 at switching to the closed position of the opening and closing valve 6 is exhausted from the cylinders 2 ₁ are to be introduced. At the open position of the on-off valve 6, the branch opening 5a of the secondary ventilation passage 5 is closed by the on-off valve 6, and the cylinder 2
At the time of operation ₁ , the high-temperature exhaust gas is prevented from flowing into the secondary air passage 5.

The on-off valve 6 is opened and closed by a negative pressure actuator 7 having a diaphragm 7a connected to an operation lever 6a via a rod 6b, and controls a control pressure chamber 7b of the negative pressure actuator 7. The switching valve 8 is selectively connected to the atmospheric pressure passage 8a and the negative pressure passage 8b connected to the intake passage of the engine via the switching valve 8, and the switching valve 8 is controlled by the controller 9 to switch the opening and closing of the on-off valve 6.

[0015] The secondary air passage 5, the check valve 10 which permits flow only from the first exhaust passage 3 ₁ side to the second exhaust passage 3 ₂ side, and the flow regulating valve 11 is interposed . Flow regulating valve 11 is adapted to be controlled by the controller 9, the controller 9, the second exhaust gas purification catalyst 4 ₂ in the exhaust gas temperature just below, i.e., a temperature sensor 12 for detecting the catalyst temperature T
From the controller 9 and the controller 9 controls the catalyst temperature T
The opening degree of the flow regulating valve 11 is controlled to increase or decrease in accordance with. Thus, the controller 9, the flow regulating valve 11, and the temperature sensor 12
Thus, a flow rate control means for controlling the flow rate of the air flowing through the secondary air passage 5 in accordance with the catalyst temperature T is constituted.

The contents of the control by the controller 9 are as shown in FIG. 2. First, in step S1, it is determined whether or not the condition is the secondary air supply condition. Specifically, a state in which the exhaust purification catalyst is not activated before the completion of warm-up is set as a secondary air supply condition, and it is determined whether or not the secondary air supply condition is based on the cooling water temperature of the engine. If the condition is the secondary air supply condition, the process proceeds to step S2, and it is determined whether the condition is the cylinder deactivation condition. Can pause the cylinders 2 of the _first bank 1 ₁ is when to maintain the operation also stable in operation of only the cylinders 2 of the _second bank 1 _2, medium Specifically, the engine speed Ne is low Speed range (for example, 1500 rpm <Ne)
Cylinder stop when the vehicle speed V is equal to or higher than the start completion speed (for example, V> 15 km / h) and the throttle opening θ is low (for example, 0.5 ° <θ <20 °). Judge as conditions.

[0017] If the cylinder deactivation conditions, to stop the fuel supply to the cylinder 2 _one step of the first bank 1 ₁ S3, the routine goes to step S4, starts counting from the time of stopping fuel supply The time t1 of the first timer is a predetermined time Yt1
Is determined. Then, while t1 <Yt1, the on-off valve 6 is held in the open position in step S5, and t1 ≧
When Yt1, the process proceeds to step S6 and the on-off valve 6
The switched to the closed position, to introduce the exhaust gas from the cylinders 2 of the _first bank 1 ₁ to the secondary air passage 5. The predetermined time Yt1 is:
After stopping the fuel supply, all of the cylinders of the first bank 1 ₁ 2
The time is set in accordance with the time required until the residual fuel is completely discharged from the fuel cell, for example, about 1 second. Thus, the never contaminating exhaust of residual fuel is supplied to the second exhaust passage 3 _2. Instead of the timer, a counter that counts the number of rotations of the crankshaft after stopping the fuel supply is used, and when the count number of the counter reaches a predetermined number, the on-off valve 6 is switched to the closed position. Is also good.

The on-off valve 6 proceeds to step S7 is switched to the closed position, the second exhaust gas purifying catalyst 4 _second catalyst temperature T is activation temperature TL (about 350 ° C.) and degradation under temperature TH (about 80
(0 ° C.). If T <TL, the process proceeds to step S8 to increase the opening of the flow control valve 11, and if T> TH, the process proceeds to S9.
The process proceeds to step (3) to decrease the opening of the flow control valve 11,
If L ≦ T ≦ TH, the process proceeds to step S10 to maintain the opening of the flow control valve 11 at the previous value. Thus, when the catalyst temperature T is lower than the activation temperature TL, the supply amount of the secondary air increases, and the secondary combustion of the exhaust increases the catalyst temperature T, and
When the catalyst temperature T exceeds the deterioration temperature TH, the supply amount of the secondary air decreases, the secondary combustion of the exhaust gas is suppressed, and the catalyst temperature T decreases, and the catalyst temperature T falls between the activation temperature TL and the deterioration temperature TH. Within the proper range between. As a result, exhaust emissions are improved and catalyst deterioration is also prevented.

It is determined whether or not the time t2 of the second timer for measuring the duration of the state where the catalyst temperature T has exceeded the deterioration temperature TH has reached a predetermined time Yt2 between steps S4 and S6. Step S11 is provided, and t2 ≧ Yt2
When it is has discontinued introduction of the on-off valve 6 proceeds to step S5 and the open position, the exhaust from the cylinders 2 of the _first bank 1 ₁ into the secondary air passage 5. Thus, the flow control valve 1
If the flow rate of the secondary air does not decrease even if T> TH due to a failure such as 1 and the state of T> TH continues for a predetermined time Yt2, the introduction of the secondary air into the secondary air passage 5 itself There is aborted, overheating deterioration of the exhaust purification catalyst 4 ₂ is prevented,
Fail safe is achieved. Here, the predetermined period Yt
2 is set to a value slightly larger than the maximum value of the duration of T> TH when the flow control is performed normally, for example, 3 seconds. When t2 ≧ Yt2, the cylinder deactivation may be stopped and the on-off valve 6 may be switched to the open position. Also, the second
The timer may be replaced with a counter for counting the number of rotations of the crankshaft after T> TH, and the opening / closing valve 6 may be switched to the open position when the counted number of the counter reaches a predetermined number.

[0020]

As is apparent from the above description, according to the present invention, since the flow rate of the secondary air supplied by the air pump function of the deactivated cylinder can be controlled so that the catalyst temperature is in an appropriate range, the exhaust emission is reduced. To improve and
Catalyst deterioration can also be prevented.

[Brief description of the drawings]

FIG. 1 shows an example of the apparatus of the present invention.

FIG. 2 is a flowchart showing a secondary air supply control program.

[Explanation of symbols]

2 ₁ , 2 ₂ cylinders 3 ₁ , 3 ₂ Exhaust passage 4 ₁ , 4 ₂ Exhaust purification catalyst 5 Secondary air supply passage 6 On-off valve 9 Controller 11 Flow control valve 12 Temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301T (72) Inventor Morio Fukuda 1-4-1 Chuo, Wako-shi, Saitama Japan Honda Co., Ltd. Inside the Technical Research Institute

Claims (3)

[Claims] 1. A secondary air supply device for an internal combustion engine capable of stopping fuel supply to some of the cylinders and suspending the operation of some of the cylinders, wherein the secondary air supply device is branched from an exhaust passage of the some of the cylinders. A secondary air passage connected upstream of the exhaust purification catalyst in the exhaust passage of the other cylinder is provided, and when the fuel supply to some of the cylinders is stopped, the exhaust from some of the cylinders is Introducing into the air passage and supplying as secondary air to the exhaust passage of the other cylinder, comprising a flow control means for controlling a flow rate of the air flowing through the secondary air passage according to a catalyst temperature. Secondary air supply device for an internal combustion engine. 2. The exhaust system according to claim 1, wherein exhaust gas from the at least one cylinder is introduced into the secondary air passage at a predetermined time after the supply of fuel to the at least one cylinder is stopped. Secondary air supply device for internal combustion engine. 3. The method according to claim 1, wherein when a state in which the catalyst temperature is equal to or higher than a predetermined temperature continues for a predetermined period, introduction of exhaust gas from the partial cylinders into the secondary air passage is stopped. 3. The secondary air supply device for an internal combustion engine according to 2.