JPH06101465A - Double pipe catalyst converter - Google Patents

Abstract

PURPOSE:To suppress reduction of a catalyst temperature in a low speed low load region by causing the flow of exhaust gas to an intercasing gap to the low speed low load region. CONSTITUTION:A catalyst casing is of double pipe structure comprising first and second casings 3 and 5. An opening part 6 is formed in the uppermost stream part of an intercasing gap 4 and an exhaust gas passage 7 is communicated with the intercasing gaps 4. A catalyst carrier 1 is divided into first and second catalysts 1a and 2a with an intercatalyst gas 8 therebetween, a hole 9 through which the intercatalyst gas 8 is communicated to the intercasing gap 4 is formed, and an on-off valve 10 is arranged in the hole 9.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a double-tube catalytic converter.

[0002]

2. Description of the Related Art As a conventional double-tube catalytic converter, for example, there is one shown in FIG. 8 (see, for example, Japanese Utility Model Laid-Open No. 2-126017).

That is, the first containing the catalyst carrier 101
The second casing 104 is arranged with a gap 103 provided on the outer periphery of the casing 102 to improve the heat retention characteristics of the catalyst carrier 101.

[0004]

However, in such a catalytic converter, the double-tube structure converter has a heat retaining effect as compared with the single-tube structure converter, but the low-speed low-load operation state and the like. Depending on the catalyst carrier 101
Since the temperature difference between the outside and the outside air is large, the temperature of the catalyst drops,
There is a problem that the active state may deteriorate.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a double-tube catalytic converter which suppresses a decrease in catalyst temperature in a low speed and low load region. .

[0006]

Therefore, in the present invention, the casing of the catalyst has a double pipe structure composed of the first casing and the second casing, and the casing gap between the first casing and the second casing is the maximum. An opening is provided in the upstream part to connect the casing gap and the exhaust passage to each other, and divide the catalyst into a first catalyst and a second catalyst. The catalyst gap between the first catalyst and the second catalyst and the casing are separated from each other. A hole communicating with the gap was provided, and an opening / closing valve was provided at the hole or the opening of the most upstream part of the gap between the casings.

[0007]

In the low speed and low load region, the exhaust gas is caused to flow between the casing gaps as needed to keep the temperature around the catalyst and suppress the temperature decrease of the catalyst.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the present invention.

A catalyst carrier 1 carrying a catalyst such as ceramics
Are accommodated in the first casing 3 via the holding member 2. A second casing 5 is arranged on the outer circumference of the first casing 3 with a gap 4 between the casings.

An opening 6 is provided in the most upstream part of the inter-casing gap 4 to connect the exhaust passage 7 to the inter-casing gap 4.

The catalyst carrier 1 is divided into a first catalyst 1a and a second catalyst 1b via an inter-catalyst gap 8, and a catalyst in a good active state is used as the first catalyst 1a, so that the conversion efficiency is early. I am trying to In addition, the first catalyst 1a and the second catalyst 1b
Is provided with a hole 9 for communicating the inter-catalyst gap 8 and the casing gap 4, and an opening / closing valve 10 is arranged in the hole 9. The open / close valve 10 may be provided in the opening 6 at the most upstream side.

Next, the operation will be described. The present invention relates to an on-off valve 1
By opening and closing 0, the exhaust gas is caused to flow or be stopped in the inter-casing gap 4, so that the exhaust gas in the inter-casing gap 4 is replaced and the heat retention of the catalyst carrier 1 is improved.

When the on-off valve 10 is opened, the exhaust gas passes through the gap 4 between the casings to warm the catalyst carrier 1 from the outside, and the second catalyst 1
It flows through the inside of b and is purified and discharged. The on-off valve 10
Is closed when the engine is started. that is,
When the temperature of the catalyst is high, it is better to heat it from the outside,
This is because if the amount of bypass flowing through the inter-casing gap 4 is large during cold start or the like, the amount of exhaust gas flowing through the catalyst carrier 1 decreases and it takes time to warm the catalyst carrier 1.

First, a first embodiment of the control operation will be described with reference to the flow chart of FIG. In this embodiment, a timer is provided and the on-off valve 10 is opened and closed periodically to replace the exhaust gas in the inter-casing gap 4.

In step 11, it is judged whether the on-off valve 10 is in the open state or in the closed state. If the open state is the open state, the process proceeds to step 12, and if it is in the closed state, the process proceeds to step 13. At the time of starting, the on-off valve 10 is in the closed state as described above.

In step 12, the time in the open state is read by the timer and the process proceeds to step 14.

The time read in step 12 In step 14 it is determined whether the time that has elapsed than the predetermined time t _2, the step 15 when the elapsed t ₂ or more
If the open / close valve 10 is closed and the time t ₂ has not been reached, the process proceeds to step 17 and the open state is maintained.

When it is determined in step 11 that the on-off valve 10 is not in the open state, the time when the on-off valve 10 is in the closed state is read in step 13 and the process proceeds to step 16.

In step 16, it is judged whether or not the time read in step 13 has passed a predetermined time t ₁ or more, and if it has elapsed, the process proceeds to step 17 to open / close the valve 1.
0 is opened, and when it has not elapsed, the process proceeds to step 15 to continue the valve closed state.

The braking described above is repeated (step 1
8). When the vehicle travels at high speed, the exhaust gas temperature rises and the catalyst temperature rises, so the control operation is stopped, and the control is restarted when the catalyst temperature falls due to low speed traveling or the like.

FIG. 3 shows the effect of this embodiment. In the conventional double-tube catalytic converter, the activation temperature T ₀ of the catalyst or less is reached at an early time t ₀ , but according to the present embodiment, the activation state can be maintained for a long time.

A second embodiment of the control operation of this embodiment will be described with reference to the flow chart of FIG. In this embodiment, a temperature sensor (not shown) is provided in the first catalyst carrier 1a, the on-off valve 10 is opened when the temperature of the catalyst falls below a predetermined temperature, and high temperature exhaust gas is supplied to the inter-casing gap 4. By flowing, the heat retention effect is improved and the temperature drop of the catalyst is suppressed.

In step 21, it is judged whether the catalyst temperature measured by the temperature sensor is higher or lower than a predetermined temperature. If it is higher, the process proceeds to step 22, and if it is lower, the process proceeds to step 23.

At step 22, the on-off valve 10 is closed, and at step 23, the on-off valve 10 is opened to increase the heat retention effect.

Then, the above control operation is repeated (step 24).

FIG. 5 shows the effect of this embodiment. According to this embodiment, a direct effect can be expected.

A third embodiment of the control operation of the present invention will be described with reference to the flowchart of FIG. In this embodiment, when the temperature of the catalyst drops, the ignition timing is temporarily delayed to raise the exhaust temperature, and the high-temperature exhaust gas is caused to flow through the inter-casing gap 4 to positively suppress the temperature drop of the catalyst. It is a thing.

In step 31, it is judged whether the catalyst temperature is higher than a predetermined temperature. If it is higher, the routine proceeds to step 33, where the on-off valve 10 is closed. If it is not higher, the process proceeds to step 32, where the on-off valve 10 is closed, and step 34
Go to.

At step 34, the ignition time is delayed to raise the exhaust gas temperature, and the routine proceeds to step 35.

In step 35, it is detected whether or not the exhaust temperature has risen. If the exhaust gas temperature rise is detected, the process proceeds to step 36, and if not detected, the process returns to step 32.

In step 36, the on-off valve 10 is opened and the high temperature exhaust gas is caused to flow through the inter-casing gap 4 to enhance the heat retention effect of the catalyst.

In step 37, high-temperature exhaust gas is flowed through the inter-casing gap 4 for a certain period of time, and then the on-off valve 10 is closed.

At step 38, the ignition timing is returned to the original value.

Then, the above control operation is repeated (step 39).

FIG. 7 shows the effect of this embodiment. According to the present embodiment, when the decrease in the catalyst temperature is detected, the exhaust gas having a high temperature is made to flow through the inter-casing gap 4, so that the decrease in the temperature of the catalyst can be suppressed and the temperature can always be maintained at the activation temperature T ₀ or higher.

[0036]

As described above, according to the present invention, it is possible to enhance the heat retention effect of the catalyst in the low speed and low load region and suppress the temperature decrease of the catalyst.

Further, since the catalyst is warmed from the surroundings, the temperature distribution of the catalyst can be made uniform and the conversion effect can be enhanced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a double-tube catalytic converter of the present invention.

FIG. 2 is a flowchart showing a first embodiment of the control operation of the present invention.

FIG. 3 is a diagram showing the effect of the first embodiment in comparison with a conventional example.

FIG. 4 is a flowchart showing a second embodiment of the control operation of the present invention.

FIG. 5 is a view showing the effect of the second embodiment in comparison with the conventional example.

FIG. 6 is a flowchart showing a third embodiment of the control operation of the present invention.

FIG. 7 is a diagram showing the effect of the third embodiment in comparison with the conventional example.

FIG. 8 is a sectional view showing a configuration example of a conventional double-tube catalytic converter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Catalyst carrier 3 ... 1st casing 4 ... Casing gap 5 ... 2nd casing 6 ... Opening 8 ... Catalyst gap 9 ... Hole 10 ... Open / close valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location F01N 7/08 A

Claims (1)

[Claims] 1. A catalyst casing comprising a first casing and a second casing.
A double pipe structure including a casing is provided, and an opening is provided in the most upstream part between the casing gaps between the first casing and the second casing to communicate the gap between the casings and the exhaust passage with each other. The catalyst is divided into two catalysts, and a hole for communicating the inter-catalyst gap between the first catalyst and the second catalyst with the inter-casing gap is provided. A double-tube catalytic converter characterized in that