JPS62191609A - Unburnt fuel purifing device of alcohol fuel vehicle - Google Patents

Abstract

PURPOSE:To improve ability for purifing unburnt alcohol by providing a bypass passage on an exhaust gas passage located between a catalytic converter and a muffler placed downstream from said converter, and fitting an unburnt alcohol trap into said passage. CONSTITUTION:A bypass passage 15 is provided between an exhaust gas passage 14, where a catalytic converter 13 is mounted for purifing exhaust gas taken out of an engine, and the downstream side of the catalytic converter 13. And, a selector valve 16 is fitted into the branch point of said bypass passage 15 from the exhaust gas passage 14 for making switching control of the bypass passage 15 to the open side when cooling water temperature is below the specified value because of engine starting. An unburnt alcohol trap 17 is mounted on the way of the bypass passage 15 with its downstream side connected to the exhaust gas passage 14 through a check valve 26. Unburnt alcohol adsorbed by the filter 25 of the trap 17 is, when the selector valve 16 switches the bypass passage 15 to the close side, separated in order to be led to an ntake passage 21 through a pasage 30.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for purifying exhaust gas emitted from a vehicle equipped with an engine that uses alcohol as fuel, and particularly to a device for purifying exhaust gas emitted from a vehicle equipped with an engine that uses alcohol as fuel. This invention relates to an unburned fuel purification device for alcohol fueled vehicles that suppresses emissions.

[Conventional technology]

As an unburned fuel purification device for a spark ignition engine that uses alcohol as fuel, a device that uses a catalytic purification device that has been conventionally used in gasoline-powered vehicles is known. This catalytic purification device has a catalytic converter installed on the exhaust pipe between the engine and the muffler, and when the exhaust gas passes through this catalytic converter, unburned fuel, CO, etc. contained in the exhaust gas are removed. Harmful ingredients are removed.

However, in such a catalyst purification device, the activity of the catalyst is weakened at low temperatures, resulting in a reduction in the purification rate of exhaust gas.

Furthermore, since alcohol fuel has a larger fuel increase rate in an unwarmed state (higher A/F) than gasoline, there is a problem that a large amount of unburned alcohol is discharged during or immediately after starting at a low temperature.

Therefore, the present applicant has previously proposed an unburned fuel purification method in which unburned alcohol contained in exhaust gas is temporarily recovered only when the activity of the catalyst is weakened, that is, when the catalytic converter is at a low temperature. A device has been proposed.

FIG. 7 shows an example of the above-mentioned unburned fuel purification device. In the figure, 1 indicates an engine, and an unburned alcohol trap 3 is provided between the engine 1 and the catalytic converter 2. The unburned alcohol trap 3 houses a filter 4 that adsorbs unburned alcohol in the exhaust gas at low temperatures and desorbs it at high temperatures. A bypass passage 5 for bypassing exhaust gas is formed in the filter 4, and a switching valve 6 for opening and closing this bypass passage 5 is formed in the bypass passage 5.
is provided. The switching valve 6 is opened when the activity of the catalyst of the catalytic converter 2 increases, that is, when the temperature of the catalytic converter 2 reaches an upper limit, and the exhaust gas is passed through the filter 4.
It flows directly into the catalytic converter 2 without passing through.

In this way, in the above-mentioned purification device, unburned alcohol is temporarily collected by the filter at low temperatures, and the unburned alcohol is transferred to the catalytic converter after the catalytic converter is in a state where it can perform its normal functions. Since it is designed to be allowed to flow in, there is an advantage that the discharge of unburned alcohol at low temperatures can be suppressed to a small level. Furthermore, since a bypass passage is formed in the filter and a switching valve is provided therein, there are also advantages in that the heat load on the filter is reduced, the ventilation resistance of exhaust gas is reduced, and engine speed is improved.

[Problem that the invention seeks to solve]

However, the above-mentioned unburned fuel purification device still has problems. In the above-mentioned device, the unburned alcohol trap is installed upstream of the catalytic converter, so the temperature of the filter rises significantly in a short period of time after the engine starts, making it difficult to ensure a sufficient amount of unburned alcohol to be adsorbed. . In other words, the filter temperature range (temperature range where fuel adsorption is possible)
Since alcohol is below the boiling point of alcohol, the sharp temperature limit of the filter limits the effective use of the filter to a short period of time after the engine starts, making it difficult to secure a sufficient amount of unburned alcohol to be adsorbed. There's a problem.

In addition, in the above-mentioned purification device, unburned alcohol desorbed from the filter is purified only by the catalytic converter.
Due to the performance of the converter, there is a limit to the amount of unburned alcohol that can be purified.

Furthermore, in the above device, regardless of whether the switching valve is open or closed,
Since the exhaust gas always passes through the hollow part of the filter, there is a problem that the durability of the filter deteriorates due to heat load, and the materials that can be used are extremely limited.

Similar to the previous application, the present invention suppresses the amount of unburned alcohol emitted from alcohol-fueled vehicles at low temperatures, and
The purpose of this patent is to solve the remaining problems of the earlier application mentioned above.

[Means for solving problems]

The unburnt fuel purifying device for an alcohol-fueled vehicle according to the present invention, which meets this objective, includes a catalytic converter for purifying exhaust gas emitted from the engine of a vehicle equipped with an engine that uses alcohol as fuel, and a catalytic converter located downstream of the catalytic converter. A bypass passage for bypassing the IJF gas is provided in the exhaust gas passage between the located muffler, and the flow of the exhaust gas is switched to either the bypass passage or the exhaust gas passage upstream of the bypass passage. a switching valve is provided, and an unburned alcohol trap having a filter that adsorbs unburned alcohol contained in exhaust gas is provided in the bypass passage;
The unburned alcohol trap is provided with unburned fuel supply means for guiding unburned alcohol adsorbed in the unburned alcohol trap to the engine intake passage by means of barge air when the temperature of the catalytic converter rises.

Note that it is desirable to provide the unburned alcohol trap with a heater that heats the filter when the unburned alcohol adsorbed on the filter is purged.

[Effect]

In the unburned fuel purification device for an alcohol-fueled vehicle configured as described above, the flow direction of the exhaust gas that has passed through the catalytic converter is switched by opening and closing the switching valve. That is, when the catalytic converter is at a low temperature and the activity of the catalyst is low, the switching valve is opened and exhaust gas flows only into the bypass passage. Since the bypass passage is provided with an unburned alcohol trap, the unburned alcohol contained in the IF gas that has flowed into the bypass passage is adsorbed and temporarily held by the unburned alcohol trap.

Then, the exhaust gas from which unburned alcohol has been removed flows into the exhaust gas passage again from the bypass passage and is sent to the muffler.

When the temperature of the catalytic converter increases, the bypass passage is closed by the switching valve. That is, when the activity of the catalyst increases, the exhaust gas is not bypassed but flows directly from the catalytic converter into the muffler. At the same time, the unburned alcohol adsorbed in the unburned alcohol trap flows into the engine intake passage together with purge air generated by the unburned fuel supply means and is guided into the combustion chamber. Therefore, unburned alcohol recovered at low temperatures is processed by combustion in the combustion chamber, and the amount of unburned alcohol discharged during low temperature startup is significantly reduced.

Furthermore, since the tJE gas flows through the bypass passage only when the temperature is low, the thermal load on the unburned alcohol trap is reduced, and the durability of the unburned alcohol trap is improved.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the apparatus for purifying unburned alcoholic vehicles according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 and 2 show an unburned fuel purification device for an alcohol fuel vehicle according to a first embodiment of the present invention. In the figure,
11 indicates an engine that uses alcohol as fuel,
Exhaust gas discharged from the engine 11 is transferred to an exhaust pipe 12a.
and is guided to the catalytic converter 13. An exhaust gas passage 14 is located downstream of the catalytic converter 13.
An exhaust pipe 12b is provided, and a muffler 14a is provided at the downstream end of this exhaust pipe 12b.

1) The gas passage 14 is provided with a bypass passage 15 that bypasses the exhaust gas flowing out from the catalytic converter 13. The exhaust gas flowing out from the catalytic converter 13 is transferred to the upstream side of the bypass passage 15, that is, in this embodiment, to the branching part between the bypass passage 15 and the exhaust gas passage 14. A switching valve 16 is provided to switch the flow to the passage.

The switching valve 16 is driven by a diaphragm 17 connected to the switching valve 16, and the diaphragm 1o is driven by a vacuum switching valve (v
svl) 19. One boat of the vacuum switching valve 19 is connected to an intake passage 21 of the engine 11 via a passage 20, and a check valve 22 is provided in the passage 2o. The other boat of the vacuum switching valve 19 can communicate with the atmosphere. Note that a water temperature sensor 23 and a vehicle speed detection sensor 24 are connected to the computer 18.

An unburned alcohol trap 17 is provided in the downstream bypass passage 15 of the switching valve 16 to adsorb unburned alcohol contained in the exhaust gas. A filter 25 housed in the unburned alcohol trap 17 adsorbs unburned alcohol, and the filter 25 is made of a heat-resistant material such as porous ceramic or porcelain.

The filter 25 is formed in a hollow shape, and one end of the hollow portion 25a is open to the switching valve 16 side of the bypass passage 15, and the other end is closed.

Thereby, the exhaust gas flows radially outward from the hollow portion 25a and is discharged into the unburned alcohol trap 17.

A check valve 26 is provided downstream of the unburned alcohol trap 17 in the bypass passage 15, and the downstream side of the check valve 26 is connected to the exhaust gas passage 14 located downstream of the switching valve 16.

The above-mentioned unburned alcohol trap 17 includes a filter 25.
An unburned fuel supply means 27 is connected to the engine 11 for guiding the unburned alcohol adsorbed thereto into the intake passage 21 of the engine 11. The unburnt fuel supply means 27 includes a trap purge inlet 28, a check valve 29, a supply passage 30, and a high metal vacuum isostatic valve (RV S V) 31. purge boat 3
2, orifice 33.

One end of the supply passage 30 opens into the hollow portion 25a of the filter 25, and the other end of the supply passage 30 opens into the intake passage 21 of the engine 11. Intake passage 21 of supply passage 30
The other end of the side is a purge boat 32, and an orifice 33 is provided in this part. Upstream of the purge boat 32 in the supply passage 20, a sensor portion 31a of a bimetallic vacuum switching valve 31 (a bimetallic vacuum switching valve 31 is provided) is configured to detect the engine cooling water temperature. There is. That is, when the cooling water temperature exceeds a predetermined value, the vacuum switching valve 31 is activated and the supply passage 30 is opened.
The hollow portion 25a of the filter 25 and the intake passage 21 are communicated with each other. The trap purge inlet 28 is an inlet that introduces the atmosphere into the unburned alcohol trap 17.
Under filter 25? % on the side. This trap barge port 28 is provided with a check valve 29 to prevent exhaust gas from leaking to the outside from this portion.

Next, the operation in the first embodiment will be explained.

When the engine starts, if the cooling water temperature is lower than the set value, the vacuum switching valve 19 is operated to the atmosphere side by the output signal from the computer 18, and the switching valve 16 opens the bypass passage 15 via the diaphragm 10. driven in the direction. As a result, the exhaust gas discharged from the engine 11 passes through the exhaust pipe 12a and passes through the filter 25 housed in the unburned alcohol trap 17.
It flows into the hollow part 25a of. The exhaust gas that has flowed into the hollow portion 25a passes through the porous portion of the filter 25 from the hollow portion 25a side and is discharged to the outer periphery of the filter 15. in this case,
When the temperature of the filter 25 is low, unburned alcohol contained in the exhaust gas is adsorbed by the filter 25. That is, in the filter 25 in a low temperature state, unburned alcohol contained in the exhaust gas enters the small pores of the filter 25 during the process of the exhaust gas becoming 1j1ia, and the unburned alcohol is absorbed.

If a certain period of time has passed after starting the engine, or if the vehicle speed is detected, the vacuum switching valve 19
operates to the intake manifold negative pressure side, and the switching valve 16
closes the bypass passage 15 and opens the exhaust gas passage 14. Therefore, the exhaust gas is not bypassed and flows only through the exhaust gas passage 14 into the muffler 14.

When the bypass passage 15 is closed by the switching valve 16 and the vacuum switching valve 31 that detects the coolant temperature is activated, the hollow part 25a of the filter 25 is communicated with the intake passage 21. 25
The pressure at a suddenly decreases, and outside air flows from the trap purge inlet 28 through the porous portion of the filter 25 into the hollow portion 25a. At this time, unburned alcohol adsorbed on the filter 25 at low temperatures is removed from the filter 25 by purge air from the outside air and guided to the intake passage 21 of the engine 11 through the supply passage 30. In this case, since the check valve 26 is provided on one side of the bypass passage 15, the exhaust gas will not flow back to the unburned alcohol trap 17 side.

Therefore, unburned alcohol adsorbed by the filter 25 of the unburned alcohol trap 17 at low temperatures is guided into the combustion chamber 11a of the engine 11 and burned and processed together with the air-fuel mixture.

FIG. 2 is a block diagram showing the control method of the first embodiment.

First, when the ignition switch (as shown) is turned on, the calculation of the main routine is started in block 101, and it is checked in block 102 whether or not the engine water temperature exceeds a set value (for example, 5° C.). If the value is below the set value, the vacuum switching valve (VSV) 19 is turned off in block 103, one chamber of the diaphragm IO is communicated with the atmosphere, and the switching valve 16 is closed.

Next, in block 104, it is determined whether or not the engine has been started. If the engine has been started, in block 105, a timer Ts for measuring the elapsed time after starting is activated. In blocks 106 and 107, the vehicle speed ■ and the timer Ts are determined, and both are set under the set conditions (for example, vehicle speed V=Q,
If the timer Ts≦120 seconds) is satisfied, the process returns from block 107 to block 106, and the same process is repeated until one of the conditions is no longer satisfied.

If vehicle speed≠0 or timer Ts>120 seconds,
Proceeding to block 108, the timer Ts is reset, and in block 109, the vacuum switching valve 17 is turned on. As a result, one chamber of the diaphragm communicates with the intake manifold negative pressure, and the switching valve 16 is switched. That is, the exhaust gas passage 15 passing to the muffler 14 side
is opened and the bypass passage 15 is closed.

Note that if the water temperature exceeds the set value in block 102,
If the engine is not started in block 104, the process returns to block 102.

Second Embodiment FIG. 3 shows an unburnt fuel purification device for an alcohol fuel vehicle according to a second embodiment of the present invention. The second embodiment differs from the first embodiment in the configuration of the unburned fuel supply means,
Since other parts are similar to the first embodiment, the same parts are given the same reference numerals as in the first embodiment, and the explanation of the same parts is omitted, and only the different parts will be explained.

In FIG. 3, 30 indicates an unburned fuel supply passage, and the unburned fuel supply passage 30 is provided with a vacuum switching valve (VSV2) 41 that opens and closes this passage. The vacuum valve 41 is connected to the computer 18 and is operated by an output signal from the combiator 18. The computer 18 includes a temperature sensor 42 provided in the catalytic converter 13;
Temperature sensors 43 provided on the filters 25 in the unburned alcohol trap 17 are connected to each other.

In the unburned fuel purification device configured in this way, the catalyst outlet temperature of the exhaust gas and the temperature of the filter 25 are equal to or lower than the set values (for example, the catalyst outlet temperature Tc S is 150°C, the filter temperature Ta≦50°C, and the vehicle speed v = 0), the computer 18 causes the vacuum switching valve 1 to
9 is operated to the atmosphere side, and the vacuum switching valve 41 of the unburned fuel supply passage is closed. As a result, the switching valve 16 operates via the diaphragm 1°,
Bypass passage 15 is opened and exhaust gas is guided to unburned alcohol trap 17.

When the catalyst outlet temperature Tc or the filter temperature Ta is below a set value or when the vehicle speed is detected, the vacuum switching valve 19 is operated to the negative pressure side and the vacuum switching valve 41 is opened. That is, the exhaust gas passes through the muffler 1 which passes through the unburned alcohol trap 17.
4a, and in one of the bypass passages 15, the filter 25 is purged with outside air.

Therefore, there is no problem that unburnt alcohol is not sufficiently purified because the catalyst bed temperature is low even if the engine water temperature is high to a certain extent, which is the case when the engine is left for a long time under low temperature conditions and then restarted after a put soak. That is,
By controlling the switching between adsorption and purge using the filter temperature Ta and the catalytic converter outlet temperature Tc, the filter 2
The adsorption and desorption performance of unburned alcohol in No. 5 is improved, and unburned alcohol can be efficiently removed under a wide range of usage conditions.

FIG. 4 is a block diagram showing a method of controlling the apparatus of FIG. 3.

First, after the calculation of the main routine is started in block 121, vehicle speed (V=0), catalyst outlet temperature (Tc 5150°C), and filter temperature (Ta 650°C) are determined in blocks 122, 123, and 124, respectively.

If all of these conditions are met, the process proceeds to block 105.105, where the vacuum switching valve (VSVI) 19 is turned off and the vacuum switching valve (VSV2) 41 is turned on. That is, the exhaust gas is guided to the unburned alcohol trap 17.

If any of blocks 122, 123, 124 is NO, a jump is made to block 127, Hakineem switching pulp 19 is turned on and vacuum switching valve 41 is turned off. That is, the exhaust gas does not pass through the unburned alcohol trap 17, and instead passes through the muffler 14a.
The filter 25 is purged in the bypass passage 15 (!!11), and the block 126,
After 128, the process returns to block 122 and the above-described calculation is repeated.

Third Embodiment FIG. 5 shows an alcohol fuel tl according to a third embodiment of the present invention.
It shows a car's unburned fuel purification device. The third embodiment is the second
Since this is a detailed description of the embodiment, the explanation of the parts that overlap with the second embodiment will be omitted, and only the different parts will be explained.

In FIG. 5, 17 indicates an unburned alcohol trap. A heater 51 for heating the filter 25 is provided outside the unburned alcohol wrap 17. The heater 51 is connected to a power source 53 via a relay 52, and is turned on and off by the relay 52 connected to the combination coater 18.

That is, when the unburned alcohol adsorbed on the filter 25 is purged, the filter 25 is heated by the heater 51 so that the unburned alcohol is completely desorbed (exploded) from the filter 25.

In the purification device configured in this manner, when the filter 25 is purged, the relay 52 is activated by a signal output from the computer 1B, and the heater 51 is heated. Exhaust gas from an alcohol-fueled r'-1 vehicle contains a large amount of water, and the heat generated by unburned alcohol is several times that of normal gasoline, and when it is removed from the filter 25 (during purging), a large amount of water ( However, heating by the heater 25 improves desorption from the filter 25. Therefore, even if the volume of the filter is the same, by providing a heater, the amount of adsorption per unit volume is increased, and the filter volume can be reduced. It becomes possible to do this.

FIG. 6 shows a control block diagram of the device of FIG.

First, after starting the main routine in block 131, measurement of the energization time oh to the trap heater 51 is started. Next, in blocks 133, 134, and 135, the vehicle speed,
The catalytic converter outlet temperature Tc and filter temperature Ta are determined, and if all are satisfied, block 13 is performed.
6, set θh=o, block 137, block 1
At 38, the vacuum switching valve 19 is turned off and the vacuum switching valve 41 is turned on. That is, the exhaust gas is guided to the unburned alcohol trap, where unburned alcohol is adsorbed. Block 133.1
34. If any of 135 is NO, block 1
39, the temperature at the time of purging the filter 25 (for example, Ta5
70° C.), and if YES, block 140
The operation of the heater 51 is confirmed in block 140a, and if the result is NO, the heater 51 is turned on in block 140a. Then, the heating time is measured in block 140b, and block 1
Proceed to 42. If the result at block 140 is No, the process proceeds to block 141, where the heater 51 is turned off.

In block 142, the heater energization time is determined (for example, Oh≦300 seconds), and if YES, in blocks 143 and 144, the vacuum switching valve 19
is turned on, the vacuum switching valve 41 is turned off, and the process returns to the front link 133. That is, the filter 25
purge is performed. Also, block 139.142
If the determination is NO, then in block 111 the heater 5
1 is turned off and the process proceeds to block 143.

And during the purge period from the start of the purge process to the start of the next purge process after the unburned alcohol intake process? The heater is repeatedly turned on and off for 300 seconds, and the filter temperature is maintained at 70°C or higher.

〔Effect of the invention〕

As explained above, when using the unburned fuel purification device for an alcohol fuel vehicle of the present invention, the following effects can be obtained.

(a) Since the unburned alcohol trap is located downstream of the catalytic converter, the temperature of the filter increases slowly after the engine is started, and the amount of unburned alcohol adsorbed onto the filter increases. As a result, the ability to purify unburned alcohol is increased, and the effect of significantly reducing the emission of unburned alcohol is obtained.

(b) When the catalytic converter is at a high temperature, the switching valve prevents exhaust gas from flowing into the bypass passage, so the heat resistance of the filter due to high heat can be improved. That is, the thermal limitations of the filter material are relaxed, allowing the use of cheaper filters.

Further, if the filter purge control is performed based on the temperature of the catalytic converter and the temperature of the filter, the control conditions can be expanded and unburned alcohol can be efficiently removed.

(d) Furthermore, if the unburnt alcohol trap is provided with a heater that heats the filter, unburned alcohol can be better desorbed from the filter, and the amount of adsorption per unit volume of the filter can be increased.

[Brief explanation of drawings]

FIG. 1 shows an alcohol fuel according to a first embodiment of the present invention.
Fig. 2 is a control block diagram of the apparatus shown in Fig. 1, and Fig. 3 is a system diagram of an unburned fuel purifying device for one vehicle, and Fig. 3 is a system diagram of an unburned fuel purifying device using alcohol salt t' according to a second embodiment of the present invention. A system diagram of the purification device, Fig. 4 is a control block diagram of the device in Fig. 3, Fig. 511
21 is a system diagram of an unburned coal t-1 purifying device for an alcohol fuel vehicle according to the third embodiment of the present invention, FIG. 6 is a control block diagram of the device shown in FIG. 5, and FIG. This is a system diagram of the unburned twisted wood 4 purification system; η proposed by the present applicant. 11・・・・・・・・・・・・・・・・・・Engine 1
3...... Catalytic converter 14... Exhaust gas passage 15...・・・・・・・・・・・・Bypass passage 16・・・・・・・・・・・・・・・・・・Switching valve 17・・・・・・・・・・・・・・・・・・・Unburned alcohol trap 18・・・・・・・・・・・・・・・・
・・Computer 21・・・・・・・・・・・・・・・
・・・Intake passage 25・・・・・・・・・・・・・・・
・・Filter 27・・・・・・・・・・・・・・・・
・Unburned fuel + Jj supply means 51...
... Heater patent applicant Toyota Motor Corporation Figure 2

Claims (1)

[Claims] (1) Exhaust gas is bypassed in an exhaust gas passage between a catalytic converter that purifies exhaust gas emitted from the engine of a vehicle equipped with an engine that uses alcohol as fuel, and a muffler located downstream of the catalytic converter. A bypass passage is provided upstream of the bypass passage to switch the flow of exhaust gas to either the bypass passage or the exhaust gas passage, and a switching valve is provided in the bypass passage,
An unburned alcohol trap having a filter that adsorbs unburned alcohol contained in exhaust gas is provided, and when the temperature of the catalytic converter rises, the unburned alcohol adsorbed in the unburned alcohol trap is transferred to the unburned alcohol trap. An unburned fuel purification device for an alcohol fuel vehicle, characterized in that an unburned fuel supply means is connected to guide the unburned fuel to an intake passage of an engine by purge air.