JPH06257424A - Adsorption quantity estimation device in hydrocarbon adsorption/separation apparatus for internal combustion engine - Google Patents

Abstract

PURPOSE:To estimate HC adsorption quantity in adsorbent, by providing an after-purge output measurement means for measuring oxygen sensor output and an adsorption quantity estimation means for estimating the adsorption quantity of hydrocarbon in adsorbent. CONSTITUTION:Adsorbent 5, for adsorbing hydrocarbon in exhaust, is provided in a sub passage 3b. A purge valve 10 is provided, which is controlling flow water in exhaust to the adsorbent 5 by valve-opening action to separate hydrocarbon from the adsorbent 5. The purge valve 10 is opened temporarily to introduce part of exhaust from an engine 1 to the adsorbent 5 from a purge inlet passage 8. HC, adsorbed here, is separated to be led to the vicinity of an oxygen sensor 13 from a purge outlet passage 9. The air fuel ratio of exhaust is measured by the oxygen sensor 13 provided at the down stream of the purge outlet passage 9 direct before the valve-opening. An exhaust air fuel ratio is measured by the same oxygen sensor 13 after a given time from the valve- opening. Adsorption quantity is estimated based on the difference, etc., of these measured values, and thus, purge timing can be appropriately controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorption amount estimation device for a hydrocarbon (hereinafter referred to as "HC") adsorption / desorption device used as an exhaust gas purification device for an internal combustion engine.

[0002]

2. Description of the Related Art Immediately after starting an internal combustion engine, a relatively large amount of HC is contained in the exhaust gas from the engine, and the temperature of the three-way catalyst does not reach the activation temperature, so it is difficult to purify the HC. Therefore, as an exhaust gas purification device for an internal combustion engine, HC in the exhaust gas is adsorbed by an adsorbent when it is cold, such as immediately after the engine is started, and desorbed (purged) after completion of warming up and purified by a three-way catalyst. An HC adsorbing / desorbing device has been proposed (see JP-A-63-68713, etc.).

[0003]

However, in such a conventional HC adsorption / desorption device, it is not possible to estimate the adsorption amount to the adsorbent, so the purge time and amount should be controlled optimally. Therefore, it is impossible to detect the degree of adsorption amount, and in some cases, the performance of the adsorbent cannot be fully utilized.

In view of such circumstances, it is an object of the present invention to make it possible to estimate the amount of HC adsorbed on the adsorbent.

[0005]

Therefore, according to the present invention, the adsorbent that adsorbs HC in exhaust gas and the flow of exhaust gas to the adsorbent are controlled by a valve opening operation to desorb HC from the adsorbent. In an HC adsorbing / desorbing device for an internal combustion engine, which is provided with at least a purge valve, as shown in FIG. 1, an oxygen sensor 13 is provided in the passage of HC desorbed from the adsorbent, while the purge valve is operated under predetermined operating conditions. Purge valve opening means A for opening the valve
An initial output measuring means B for measuring the oxygen sensor output immediately before the valve opening, a post-purge output measuring means C for measuring the oxygen sensor output a predetermined time after the valve opening, and the adsorbent in the adsorbent based on these measured values. Adsorption amount estimating means D for estimating the adsorption amount of HC is provided to configure an adsorption amount estimating device.

[0006]

In the above structure, the oxygen sensor output is read and measured under a predetermined operating condition which is determined in advance as a condition for estimating the adsorption amount, and then the purge valve is temporarily opened to remove the adsorbent from the adsorbent. Desorb HC. Then, the oxygen sensor output is read again and measured after a predetermined time from the valve opening, and the adsorbed amount of HC on the adsorbent is estimated from the difference between these measured values.

[0007]

EXAMPLES Examples of the present invention will be described below. FIG. 2 shows the system configuration. Exhaust gas from the engine 1 reaches the exhaust pipe 3 via the exhaust manifold 2. A three-way catalyst 4 is provided in the middle of the exhaust pipe 3. And three-way catalyst 4
The downstream exhaust pipe 3 includes a main passage 3a and a sub passage 3b parallel to the main passage 3a.
And an adsorbent 5 for HC containing activated carbon or zeolite as a main component is provided in the sub passage 3b.

In order to control the flow of exhaust gas into the main passage 3a and the sub passage 3b, a main passage valve 6 is provided in the main passage 3a, and the sub passages are provided upstream and downstream of the adsorbent 5 in the sub passage 3b. Valves 7, 7 are interposed. Also, for the adsorbent 5,
The purge inlet passage 8 from the exhaust manifold 2 is connected to the adsorbent 5 and the purge outlet passage 9 from the adsorbent 5 serves as a three-way catalyst as a purge passage for desorbing and processing the HC adsorbed thereto. 4 is connected to the exhaust pipe 3 upstream. In the purge inlet passage 8 and the outlet passage 9, a purge valve 10,
10 are installed.

Here, the main passage valve 6, the auxiliary passage valve 7,
Opening and closing of 7 and purge valves 10 and 10 are performed by a control unit 11 with a built-in microcomputer. Also,
An oxygen sensor 12 is provided at the collecting portion of the exhaust manifold 2, and its signal is input to the control unit 11. This is used to control the amount of fuel supplied to the engine 1.

Further, the purge outlet passage 9 in the exhaust pipe 3
An oxygen sensor 13 is provided on the downstream side of the open end of the three-way catalyst 4 and on the upstream side of the three-way catalyst 4, and the signal thereof is also input to the control unit 11. This is used to estimate the amount of HC adsorbed. The HC adsorption / desorption control will be described. At a low temperature immediately after the engine 1 is started, the main passage valve 6 is closed, the auxiliary passage valves 7, 7 are opened, and the purge valves 10, 10 are closed. Therefore, the exhaust gas from the engine 1 passes through the three-way catalyst 4, is then guided to the side of the sub passage 3b and flows into the adsorbent 5, and the HC in the exhaust gas is adsorbed by the adsorbent 5. Therefore, even if the three-way catalyst 4 is inactive, the release of HC in the exhaust gas to the atmosphere is prevented.

When the warm-up progresses to a certain extent, the adsorption capacity of the adsorbent 5 is lost, and the three-way catalyst 4 is almost activated, so that the adsorption of HC is terminated and the desorption is prevented.
Main passage valve 6 opened, sub passage valves 7, 7 closed, barge valves 10, 10
Control to close. Therefore, the exhaust gas from the engine 1 is exhausted through the main passage 3a after passing through the three-way catalyst 4. When the warm-up is completed, the main passage valve 6 is opened, the auxiliary passage valves 7 and 7 are closed, and the barge valves 10 and 10 are opened at a predetermined time for desorption of HC. Therefore, a part of the exhaust gas from the engine 1 is introduced into the adsorbent 5 from the purge inlet passage 8, the HC adsorbed therein is desorbed, and is guided from the purge outlet passage 9 to the upstream side of the three-way catalyst 4. Get burned. Therefore, the H desorbed from the adsorbent 5
C is introduced into the three-way catalyst 4 and purified.

Next, the HC adsorption amount estimation device in such an HC adsorption / desorption system will be described. The HC adsorption amount estimation device is realized by the microcomputer in the control unit 11 executing an adsorption amount estimation routine shown in the flowchart of FIG. 3, for example.
Note that this adsorption amount estimation routine is performed under a predetermined operating condition (for example, during steady operation) that is set in advance as a condition for estimating the adsorption amount.
It is executed when is satisfied.

First, the flow chart of FIG. 3 which is the first embodiment will be described with reference to the time chart of FIG. Step 1 (denoted as S1 in the figure. The same applies hereinafter)
Then, the exhaust air-fuel ratio (A / F) is detected by reading the output of the oxygen sensor 13, and this is set as V ₀ . In step 2, the purge valves 10 and 10 are opened for a certain period of time (see FIG. 4). As a result, a part of the exhaust gas from the engine 1 is introduced into the adsorbent 5 from the purge inlet passage 8, the HC adsorbed therein is desorbed, and the oxygen sensor from the purge outlet passage 9 is released.
It is led to 13 neighborhoods.

In step 3, it is judged whether or not a predetermined time Δt has elapsed since the purge valves 10 and 10 were opened, and the predetermined time Δt was determined.
When the time has elapsed, go to step 4. In addition, the opening time of the purge valves 10 and 10 is Δt or less. In step 4, by reading the output of the oxygen sensor 13 again, the exhaust air-fuel ratio (A /
F) is detected and this is designated as V ₁ .

In step 5, the oxygen sensor output V ₁ after the purge valve is opened to the oxygen sensor output V ₀ before the purge valve is opened.
The exhaust air-fuel ratio change amount (rich increase amount) Δd = V ₁ −V ₀ before and after the purge valve is opened is calculated by subtracting (see FIG. 4). In step 6, the adsorption amount Q is obtained by searching from the exhaust air-fuel ratio change amount Δd by referring to a predetermined table.

When the amount Q of HC adsorbed on the adsorbent 5 is estimated in this way, the purge timing and the like from the adsorbent 5 is controlled based on this result. In the first embodiment, the step 1 corresponds to the initial output measuring means, the step 2 corresponds to the purge valve opening means, and the step 4 corresponds to the post-purge output measuring means. The steps 5 and 6 correspond to the adsorption amount estimating means.

Next, the flowchart of FIG. 5, which is the second embodiment, will be described. Steps 1 to 4 are the first
The same as the embodiment of In step 5 ′, the oxygen sensor output V ₀ before opening the purge valve, the oxygen sensor output V ₁ after opening the purge valve, and the time Δt are used to determine the change amount Δd / Δt = (V _{1 of the} exhaust air-fuel ratio with time. Calculate −V ₀ ) / Δt.

In step 6 ', a predetermined table is referred to, and the adsorption amount Q is obtained by searching from the time change amount Δd / Δt of the exhaust air-fuel ratio. In this way, by estimating the adsorption amount Q from the time change amount Δd / Δt of the exhaust air-fuel ratio, it is possible to adapt to the difference in desorption characteristics of the adsorbent 5. In the second embodiment, the steps 5'and 6'correspond to the adsorption amount estimating means.

Next, the flowchart of FIG. 6 which is the third embodiment will be described. In step 11, the oxygen sensor 13
The exhaust air-fuel ratio (A / F) is detected by reading the output of the above, and this is set as V ₀ . In step 12, purge valve 1
Open 0 and 10 for a certain period of time. As a result, part of the exhaust gas from the engine 1 is introduced into the adsorbent 5 from the purge inlet passage 8, the HC adsorbed therein is desorbed, and is guided from the purge outlet passage 9 to the vicinity of the oxygen sensor 13.

In step 13, it is judged whether or not a predetermined time Δt _{1 has} elapsed from the opening of the purge valves 10 and 10, and the predetermined time Δt _{1 is} reached.
When t _{1 has} elapsed, the process proceeds to step 14. In step 14,
The exhaust air-fuel ratio (A / F) is detected by reading the output of the oxygen sensor 13 again, and this is taken as V ₁ . Step 15
In an oxygen sensor output V ₀ which before the purge valve opening, from the purge valve opening and the oxygen sensor output V ₁ of the post-Delta] t _1, time Delta] t
_{From 1} , the change amount of the exhaust air-fuel ratio with time Δd ₁ / Δt ₁ =
Calculate (V ₁ −V ₀ ) / Δt ₁ .

In step 16, a predetermined Δd / Δt-
Referring to the Q table, the time variation of the exhaust air-fuel ratio Δd ₁ /
The adsorption amount Q ₁ is obtained from Δt ₁ by searching (see FIG. 7). In step 17, it is determined whether or not a predetermined time Δt ₂ (> Δt ₁ ) has elapsed since the purge valves 10, 10 were opened, and when the predetermined time Δt _{2 has} elapsed, the process proceeds to step 18. The opening time of the purge valves 10 and 10 is set to Δt ₂ or less.

In step 18, the output of the oxygen sensor 13 is output again.
The exhaust air-fuel ratio (A / F) is detected by reading
This is V₂And In step 19, before opening the purge valve
Oxygen sensor output V₀From the purge valve opening Δt₂After acid
Elementary sensor output V₂And time Δt₂And from the air-fuel ratio time
Change Δd ₂/ Δt₂= (V₂-V₀) / Δt₂Calculate
To do.

In step 20, a predetermined Δd / Δt-
Referring to the Q table, the time variation of the exhaust air-fuel ratio Δd ₂ /
The adsorption amount Q ₂ is obtained from Δt ₂ by searching (see FIG. 7). In step 21, a predetermined Δd / Δt-Q table is referred to and the adsorption amount Q is obtained from (Q ₂ −Q ₁ ) / (Δt ₂ −Δt ₁ ) by searching. As described above, in this embodiment, the amount of change in time (Q ₂ −
The adsorption amount Q is estimated from Q ₁ ) / (Δt ₂ −Δt ₁ ). According to this, it is possible to deal with a change in the desorption capacity of the adsorbent.

In the third embodiment, the step 11 corresponds to the initial output measuring means, the step 12 corresponds to the purge valve opening means, and the steps 14 and 18 correspond to after the purge. Corresponds to the output measuring means, steps 15, 16,
The parts 19, 20, and 21 correspond to the adsorption amount estimation means. Next, the flowchart of FIG. 8 which is the fourth embodiment will be described with reference to the timing chart of FIG.

In the fourth embodiment, the valve opening operation of the purge valves 10 and 10 is repeated at regular intervals, and the adsorption amount of the adsorbent 5 is estimated from the change in the rich increase amount for each small purge. is there. At step 31, the exhaust air-fuel ratio (A / F) is detected by reading the output of the oxygen sensor 13,
This is V ₀ .

In step 32, the purge valves 10 and 10 are opened for a fixed time (first time). In step 33, purge valve 1
It is determined whether or not a predetermined time Δt has elapsed from the first valve opening of 0 and 10, and when the predetermined time Δt has elapsed, the routine proceeds to step 34. In addition, the opening time of the purge valves 10 and 10 is Δt or less.
In step 34, the exhaust air-fuel ratio (A / F) is detected by reading the output of the oxygen sensor 13 again, and this is set to V ₁ .

In step 35, the air-fuel ratio change amount (rich increase amount) Δd is obtained by subtracting the initial oxygen sensor output V ₀ before the purge valve opening from the current oxygen sensor output V ₁ after the purge valve opening. to calculate ₁ = V ₁ -V _0. Step
At 36, it is determined whether or not a predetermined time Δt 'has elapsed from the detection of the exhaust air-fuel ratio.
Proceed to 37.

In step 37, the purge valves 10 and 10 are opened for a fixed time (second time). In step 38, purge valve 1
It is determined whether or not a predetermined time Δt has elapsed from the second valve opening of 0 and 10, and when the predetermined time Δt has elapsed, the process proceeds to step 39. In step 39, the output of the oxygen sensor 13 is read again to detect the exhaust air-fuel ratio (A / F), and this is detected as V
_Set to ₂ .

At step 40, the air-fuel ratio change amount (rich increase amount) Δd is obtained by subtracting the initial oxygen sensor output V ₀ before the purge valve is opened from the current oxygen sensor output V ₂ after the purge valve is opened. to calculate the ₂ = V ₂ -V _0. Step
At 41, it is judged whether or not a predetermined time Δt 'has elapsed from the detection of the exhaust air-fuel ratio, and if the predetermined time Δt' has elapsed, a step
Proceed to 42.

In step 42, the purge valves 10 and 10 are opened for a certain period of time (third time). In step 43, purge valve 1
It is determined whether or not a predetermined time Δt has elapsed from the third valve opening of 0 and 10, and when the predetermined time Δt has elapsed, the routine proceeds to step 44. In step 44, the exhaust air-fuel ratio (A / F) is detected by reading the output of the oxygen sensor 13 again, and this is detected as V
_Set to ₃ .

In step 45, the air-fuel ratio change amount (rich increase amount) Δd is obtained by subtracting the initial oxygen sensor output V ₀ before the purge valve is opened from the current oxygen sensor output V ₃ after the purge valve is opened. ₃ = to calculate the V ₃ -V _0. Step
At 46, the following value is calculated, and based on this value, the adsorption amount Q is obtained by searching from a predetermined table.

[K ₁ (Δd ₁ −Δd ₂ ) + K ₂ (Δd ₂
-Δd ₃ )] / 2 However, K ₁ ≤K _{2 In} this fourth embodiment, the step 31 corresponds to the initial output measuring means, and the steps 32, 37 and 42 open the purge valve. It corresponds to the valve means, and the steps 34, 39 and 44 correspond to the output measuring means after purge, and the steps 35, 40 and
The parts 45 and 46 correspond to the adsorption amount estimation means.

[0033]

As described above, according to the present invention, the amount of HC adsorbed on the adsorbent can be accurately estimated, and the purge timing from the adsorbent can be appropriately controlled based on this. The effect of becoming is obtained.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention.

FIG. 2 is a system diagram of an embodiment of the present invention.

FIG. 3 is a flowchart of an adsorption amount estimation routine showing the first embodiment.

FIG. 4 is a time chart of the first embodiment.

FIG. 5 is a flowchart of an adsorption amount estimation routine showing a second embodiment.

FIG. 6 is a flowchart of an adsorption amount estimation routine showing a third embodiment.

FIG. 7 is a characteristic diagram of the third embodiment.

FIG. 8 is a flowchart of an adsorption amount estimation routine showing a fourth embodiment.

FIG. 9 is a time chart of the fourth embodiment.

[Explanation of symbols]

 1 engine 2 exhaust manifold 3 exhaust pipe 3a main passage 3b auxiliary passage 4 three-way catalyst 5 adsorbent 6 main passage valve 7 auxiliary passage valve 8 purge inlet passage 9 purge outlet passage 10 purge valve 11 control unit 12, 13 oxygen sensor

Claims (1)

[Claims] 1. An internal combustion engine comprising at least an adsorbent that adsorbs hydrocarbons in exhaust gas, and a purge valve that controls the flow of exhaust gas to the adsorbent by a valve opening operation to desorb hydrocarbons from the adsorbent. In a hydrocarbon adsorption / desorption device, an oxygen sensor is provided in the passage of hydrocarbons desorbed from the adsorbent, while a purge valve opening means for opening the purge valve under predetermined operating conditions and oxygen immediately before opening Initial output measuring means for measuring the sensor output, post-purge output measuring means for measuring the oxygen sensor output after a predetermined time from the valve opening, and adsorption for estimating the adsorption amount of hydrocarbons in the adsorbent based on these measured values An adsorption amount estimation device provided with an amount estimation means.