JPS62251415A - Exhaust gas purifying device for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve a purification rate of NOx, by supplying fuel evaporated gas to the upstream side of an exhaust gas purifying device when air-fuel ratio is in a lean state. CONSTITUTION:A catalytic device 26 is provided in an exhaust pipe 24, while air-fuel ratio of a mixture, supplied to an engine, is controlled to a level in the vicinity of the theoretical air-fuel ratio by detecting a signal from an O2 sensor 28. And a supply pipe 42 is connected with the upstream side from the catalytic device 26 of the exhaust pipe 24 so that fuel evaporated gas from a fuel tank can be supplied through an air pump 34 and an evaporated gas supply valve 44. A control circuit 48, if it detects the air-fuel ratio to be in a leaner state than the theoretical air-fuel ratio in the deceleration time or the like of the engine, opens the valve 44 to supply the fuel evaporated gas to the catalytic device 26, and a purification rate of NOx is improved by HC in the catalytic device.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention purifies exhaust gas from internal combustion engines! The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device for an internal combustion engine that can maintain the performance of a catalyst for purifying harmful components in exhaust gas over a long period of time.

(Prior art) Catalyst devices filled with oxidation catalysts or three-way catalysts have been used to purify harmful acids in exhaust gas emitted from engines.Catalysts filled with three-way catalysts The device is
Co, IC, and No. are harmful components in exhaust gas due to their oxidation and reduction effects.

If the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio, C2 will be purified even after combustion.
Since the amount of N0 increases and the reducing action becomes inactive,
If the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio, the oxidation effect becomes inactive and the C05HC purification rate deteriorates. Therefore, in order to simultaneously and efficiently purify the three harmful components in a catalyst device filled with a three-way catalyst, it is necessary to control the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio and combust the air-fuel mixture. In this way, by controlling the air-fuel ratio to near the stoichiometric air-fuel ratio, the three harmful components in the exhaust gas can be simultaneously and efficiently purified, and the catalyst performance can be maintained over a long period of time.

However, during transient times such as during vehicle deceleration, the amount of intake air changes suddenly, making it impossible to control the air-fuel ratio to near the stoichiometric air-fuel ratio, thereby reducing the purification rate of the three harmful components. Also, if the above transient state occurs frequently, the catalyst may become overheated.
There is a problem in that the time of exposure to an excessively large atmosphere or an excessively high IIC atmosphere increases, resulting in a shortened catalyst life.

For this reason, in the past, secondary air was supplied to the exhaust system to reduce CO
, by improving the purification rate of HC and by recirculating exhaust gas into the intake system using an EGR device.

Efforts are being made to reduce emissions.

[Problems to be solved by the invention] However, in the conventional method of improving the purification rate of the No. Furthermore, there are problems in that drivability deteriorates and HC and Co emissions deteriorate due to unstable combustion.

Therefore, the present invention provides an internal sti-conductor that can improve the purification rate of N011 at a lean air-fuel ratio without causing a decrease in engine output, deterioration in triability, and deterioration in HC, Go emissions. The purpose is to provide an exhaust gas purification device.

[Means for solving problems]

To achieve the above object, the present invention provides an air-fuel ratio detection means for detecting an air-fuel ratio, an exhaust gas purification means for purifying harmful components in exhaust gas, and a means for supplying fuel evaporative gas to the upstream side of the exhaust gas purification means. evaporative gas supply means, and control means for controlling the evaporative gas supply means so that fuel evaporative gas is supplied to the upstream side of the exhaust gas purification means when the air-fuel ratio is leaner YM than the stoichiometric air-fuel ratio. It is composed of:

[Effect]

According to the present invention, when the air-fuel ratio is detected by the air-fuel ratio detection means and the detected air-fuel ratio is leaner than the stoichiometric air-fuel ratio,
That is, when the NOx purification rate decreases, the evaporative gas supply means is controlled by the control means, and the fuel evaporative gas is supplied to the upstream side of the exhaust gas purification means that purifies harmful components in the exhaust gas, and the exhaust gas and fuel evaporative gas are The mixed gas with the gas is introduced into the exhaust gas purification means. The exhaust gas at this time is a gas generated by burning a mixture leaner than the stoichiometric air-fuel ratio, so the amount of 0□ is large and the reducing action is inactive. This IC activates the reducing action and NO
The purification rate of 8 can be improved. In addition, by appropriately determining the amount of fuel evaporative gas, the air-fuel ratio can be adjusted to the stoichiometric air-fuel ratio by appropriately determining the amount of fuel evaporative gas. This can be made equivalent to the wandering gas generated when a mixture equal to

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to improve the purification rate of NO8 without introducing exhaust gas into the intake system, so when improving the purification rate of No. deterioration and l(C emission deterioration can be prevented from occurring,
This effect can be obtained.

[Explanation of aspects]

By the way, the present inventors have developed EGl'? When we measured exhaust emissions during deceleration in an internal combustion engine equipped with this device, we found that the moment the throttle valve was closed, the NO□ purification rate peaked and the NOx emissions increased, as shown in Figure 2. I found out what to do.

The reason for this is that the EGR device suppresses the generation of NO8 by recirculating the exhaust gas into the intake system and lowering the combustion temperature, but if the air-fuel ratio of the mixture is leaner than the stoichiometric air-fuel ratio, the exhaust gas Even if the mixture is supplied, the mixture remains lean, and even if this mixture is burned, the catalyst will
As a result, NOx is emitted until the NO8 suppression effect of exhaust gas recirculation becomes large, that is, until the combustion temperature decreases, and the amount of NO8 emissions increases at its peak. considered to be a thing.

In order to prevent such peak NOx emissions, in case B of the present invention, the control means directs the fuel to the upstream side of the exhaust gas purification means when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and the engine is in a deceleration state. The evaporative gas supply means is controlled so that evaporative gas is supplied.

According to this aspect, when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and is in a deceleration state, that is, when the amount of NOx emissions increases at its peak, the fuel evaporative gas is supplied to the upstream side of the exhaust gas purification device, so that the exhaust gas Fuel evaporated gas is mixed with the fuel and introduced into the exhaust gas purification means, and the reduction action becomes active, improving the purification rate of N011 and reducing the peak emission amount of No.

Therefore, according to the above aspect, a unique effect can be obtained in that the peak amount of NO, which occurs during deceleration, can be reduced.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 shows an internal combustion engine equipped with an exhaust gas purification device to which the present invention can be applied, in which a throttle body lO equipped with a throttle valve 8 is arranged downstream of an air cleaner (not shown). ing. This throttle body 10 has a linear throttle opening sensor 12 configured with a potentiometer or the like that detects the opening of the throttle valve 8.
is installed. A surge tank is arranged downstream of the throttle body 10, and this surge tank includes a semiconductor strain resistance type pressure sensor 14 that detects the intake pipe absolute pressure.
is installed. The surge tank is communicated with the combustion chamber of the engine body 16 via the intake manifold 1B and the intake boat. A fuel injection valve 20 is attached to the intake manifold 18 for each cylinder so as to protrude into the intake manifold.

The combustion chamber of the engine body 16 is communicated with a catalyst bag W126 filled with a three-way catalyst via an exhaust boat, an exhaust manifold 22, and an exhaust pipe 24. This exhaust manifold 22 outputs an air-fuel ratio signal that is inverted at the residual oxygen concentration in the exhaust gas corresponding to the stoichiometric air-fuel ratio. A sensor 28 is attached.

A pulley 30 is attached to the output shaft of the engine body 16, and this pulley 30 is connected via a V-belt 32 to a pulley 36 attached to the drive shaft of an air pump 34. This air pump 34 includes a pulley 30 that is rotated by the engine when the electromagnetic clutch is engaged.
It is driven via a V-belt 32 and a pulley 36.

The inlet of the air pump 34 is communicated with a fuel tank and a charcoal canister 40 via an evaporative gas introduction pipe 38. In addition, the outlet of the air pump 34 is
It is connected to the exhaust pipe 24 on the upper and downstream side of the catalyst device 26 via the evaporative gas supply pipe 42 . This evaporative gas supply pipe 42
An evaporative gas supply valve 44, the details of which are shown in FIG. 4, is disposed at.

The evaporative gas supply valve 44 is, as shown in FIG.
Valve body 44B fixed to mover 44A and this mover 44
Solenoid 44 that moves valve body 44B by moving A
One end of the solenoid 44C is grounded via a silicon commutator 44D. Note that 44B is a movable spring, and 44F is a set screw.

The charcoal canister 40 is connected to the throttle body 10 via a conduit 46, and supplies evaporative fuel gas to the intake system in accordance with the opening degree of the throttle valve, as usual.

The throttle opening sensor 12, pressure sensor 14, and 02 sensor 28 are configured by a microcomputer.
It is connected to the #1m circuit 48. And the control circuit 4
8 is ti'' to the fuel injection valve 20, the electromagnetic clutch of the air pump 34, and the solenoid 44C of the evaporative gas supply valve 44.
Ix has been done.

As shown in FIG.
(A/D converter) 52, output ink face circuit 5
4, an input interface circuit 56, a central processing unit (CPU) 58 including a memory such as a read-only memory, and a low voltage power supply 60. The pressure sensor 14 and the throttle opening sensor I2 are connected to the human power interface circuit 50, and the human power interface circuit 56
The 02 sensor 28 is connected to the output interface circuit 54, and the solenoid 4 of the evaporative gas supply valve 44 is connected to the output interface circuit 54.
4C and the electromagnetic clutch of the air pump 34 are connected. As shown in FIG. 6, the above memory stores in advance a map showing the deceleration area expressed by the rate of change ΔS of the throttle opening and the intake pipe pressure, as well as a program for the control routine described below. . The deceleration map in Figure 6 shows the Afl]'I area where the deceleration is maximum, and the B area where the deceleration is at an intermediate value.
The area and deceleration are divided into C areas where the minimum deceleration is possible. In addition, as shown in FIG. 7, the memory shown in ``2'' also contains the time Tp for operating the air pump 34 and the evaporative gas supply, which are predetermined according to the region F, Bml region, and C region in FIG. A table defining the time TV for opening the valve 44 is stored in advance.

Next, the fuel evaporative gas supply routine of this embodiment will be explained with reference to FIG. First, in step lOO, the o2 sensor output is taken in, and in step 102, the o2 sensor output is taken in.
It is determined whether the output of the second sensor indicates that the air-fuel ratio is equal to or not. When it is determined that the o2 sensor output indicates a lean air-fuel ratio, the pressure sensor 14 is
The current intake pipe pressure Vi stored in the memory is acquired by A/D converting the output, and the current intake pipe pressure Vi stored in the memory is acquired by A/D converting the output of the throttle opening sensor 12 in step 106. Take in the opening degree Si. Then, in step 108, the previous throttle opening S is -1 from the current throttle opening Si.
By subtracting , the speed of change ΔS of the throttle opening is determined. In the next step 110, the deceleration G (ΔS, Vi) is calculated based on the current intake pipe pressure Vi taken in in step 104 and the rate of change ΔS of the throttle opening calculated in step 108. The speed G is the 6th
Determine which area of the map it belongs to.

In step 112, based on the area of deceleration G determined in step +10, the air pump 3 is
4 and the evaporative gas supply valve 44
Calculate the time TV for opening the valve. And step 11
At step 4, the electromagnetic clutch of the air pump 34 is engaged to operate the air pump 34, and at the same time, the solenoid of the evaporative gas supply valve 44 is energized to open the evaporative gas supply valve 44. In step llG, step 1
It is determined whether the time Tp1Tv calculated in step 12 has elapsed, and if these times have elapsed, the electromagnetic clutch of the air pump 34 is disengaged in step 118, and the air pump 34 is turned off.
At the same time, the solenoid of the evaporative gas supply valve 44 is demagnetized to close the evaporative gas supply valve 44. Operate the air pump 34 to close the evaporative gas supply valve 44.
By opening the valve, fuel evaporative gas in the fuel tank and charcoal canister 40 are transferred through the evaporative gas introduction pipe 38.
The fuel evaporative gas adsorbed in the catalytic converter 26 is introduced into the air pump 34 , and is further passed through the evaporative gas supply pipe 42 and the evaporative gas supply valve 44 to the exhaust pipe 24 on the upstream side of the catalyst device 26 .
Fuel evaporative gas is supplied to the

As a result of the above, when the air-fuel ratio is lean, the speed of change ΔS of the throttle opening increases. is increased.

FIG. 8 shows the opening time of the evaporative gas supply valve 44 when controlled as described above, along with changes in vehicle speed, O2 sensor output, pressure sensor output, and throttle opening sensor output.

In addition, although the example in which the fuel evaporative gas supply meter is changed in accordance with the deceleration G when the air-fuel ratio is higher than the stoichiometric air-fuel ratio has been described above, the present invention is not limited to this, and the present invention is not limited to this. The fuel vapor gas may be supplied only when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, without changing the supply amount of the fuel vapor gas depending on the speed. That is,
Fuel evaporative gas may also be supplied when the air-fuel ratio is lean other than during deceleration. In addition, we have explained an example in which the air pump is operated and the evaporative gas supply pulp is opened to supply fuel evaporative gas. The supply amount of fuel evaporative gas may be changed by changing the amount of fuel evaporative gas. Further, although an example in which constant fuel evaporative gas is supplied in each region has been described above, the present invention is not limited to this, and the present invention can be applied in each region according to the deceleration G or regardless of the region. The amount of fuel evaporative gas supplied may also be changed.

[Brief explanation of drawings]

Fig. 1 is a flowchart showing a fuel evaporative gas supply routine according to an embodiment of the present invention, Fig. 2 is a diagram showing a conventional peak NO8 generation state, and Fig. 3 is an exhaust gas purification device to which the present invention can be applied. 4 is a cross-sectional view showing details of the evaporative gas supply pulp shown in FIG. 3; FIG. 5 is a block diagram showing details of the control circuit shown in FIG. 3; A diagram showing the corresponding regions, FIG. 7 is a diagram showing a table of operating times of the air pump and evaporative gas supply pulp corresponding to the regions in FIG. 6, and FIG. 8 is a timing diagram showing waveforms of various parts in this example. It is a chart. 8... Throttle valve, lO... Throttle body, 14... Pressure sensor, 20... Fuel injection valve, 26... Catalyst device, 28... O2 sensor, 34... Air pump, 38 ... Evaporative gas introduction pipe, 42... Evaporative gas supply pipe, 44... Evaporative gas supply pulp, 48... Control circuit.

Claims (2)

[Claims] (1) an air-fuel ratio detection means for detecting an air-fuel ratio; an exhaust gas purification means for purifying harmful components in exhaust gas; an evaporative gas supply means for supplying fuel evaporative gas to the upstream side of the exhaust gas purification means; A control means for controlling the evaporative gas supply means so that the evaporative gas is supplied to the upstream side of the exhaust gas purification means when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio;
Exhaust gas purification equipment for internal combustion engines, including (2) The control means controls the evaporative gas supply means so that the fuel evaporative gas is supplied to the upstream side of the exhaust gas purification means when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and is in a deceleration state. An exhaust gas purification device for an internal combustion engine according to claim (1).