JPH0447115A - Exhaust disposal equipment of internal combustion engine - Google Patents

Abstract

PURPOSE:To enable regeneration for good fuel consumption efficiency when a trap is regenerated by injecting fuel into an engine combustion chamber at the end of engine expansion stroke or during exhaust stroke, and supplying very combustible activated fuel to the trap with a catalyst through an oxidation catalyst. CONSTITUTION:An oxidation catalyst 51 and a trap with a catalyst 52 to scavenge particulates are interposed serially in the exhaust passage 50 of an internal combustion engine, and further a bypass passage 53 that detours the trap 52 is provided. When the trap is regenerated, a bypass control means 56 whereinto the signal of a temperature detection means 55 is input controls so that a bypass valve 54 is closed when exhaust temperature is within a specified range of temperature lower than the trap regeneration temperature and higher than that, and opened at the time other than that. Also, fuel is injected by a fuel injection device 58 at the end of engine expansion stroke or during exhaust stroke when the exhaust temperature is within the specified range of temperature by a regenerated fuel control means 57, as well as its injection volume is controlled to increase or decrease in response to exhaust temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is mainly applied to an exhaust treatment device for a diesel engine.

(Prior art) When installing a trap to capture exhaust particulates in the exhaust passage in order to prevent particulates in the exhaust of a diesel engine from being released into the atmosphere, the particulates collected by the trap are As the amount of curate increases, the exhaust pressure increases and the effect on engine performance becomes greater. Therefore, the trap is regenerated by periodically burning and removing the vertinylate, which is mainly composed of carbon, captured in the trap. ing.

In Japanese Utility Model Application No. 61-173712 by the present applicant,
A bypass passage is provided in the exhaust passage upstream of the trap, and an oxidation catalyst is installed in this bypass passage. When a predetermined regeneration period is reached, fuel is supplied upstream of the oxidation catalyst, and this catalyst removes the unused substances in the exhaust gas. The fuel components are oxidized and burned, and the reaction heat is used to burn particulates in the downstream trap for regeneration.

Particulates self-ignite and burn when the exhaust temperature reaches a regeneration temperature of, for example, 400 degrees Celsius or higher, but regeneration combustion is difficult at temperatures below that, so the exhaust temperature during regeneration is detected, and in the region where self-ignition does not occur, Fuel is supplied upstream of the catalyst, which has high low-temperature activity, and the heat of the oxidation reaction raises the exhaust temperature.

(Problem to be solved by the invention) However, depending on the operating conditions of the engine, the exhaust temperature may be low;
Even if fuel is supplied upstream of the catalyst, the oxidation reaction may be insufficient and the particulates in the trap may not burn smoothly. In such cases, more particulates may accumulate in the trap. The exhaust pressure may increase significantly due to clogging, which may significantly reduce operating performance.

Of course, at this time, the fuel supplied to the exhaust gas is not completely combusted, and much of it is emitted as white smoke.

Additionally, in this case, the exhaust gas flows to the oxidation catalyst only during regeneration, and during normal operation, it flows directly into the trap. Therefore, the temperature of the exhaust gas flowing into the trap passes through the oxidation catalyst, and the unburned components in the exhaust gas are oxidized. Therefore, automatic combustion of particulates collected in the trap is limited to continuous combustion, for example, when the exhaust temperature rises above the auto-ignition temperature of carbon. This is limited to situations such as high-load operation.

Therefore, there are fewer opportunities for self-regeneration of the collected particulates, and the interval between regeneration periods cannot be extended.

Furthermore, in addition to particulates whose main component is carbon, exhaust gas may contain large amounts of unburned components (SOF), which burn at relatively low temperatures depending on the operating conditions, and these can be trapped. Difficult to remove by burning.

Therefore, the present invention provides an exhaust treatment device for an internal combustion engine that does not generate white smoke or impair the durability of the trap during regeneration, and that can reliably purify unburned components and increase the chances of self-regeneration during normal operation. The purpose is to provide.

(Means for Solving the Problems) As shown in FIG. 1, the present invention provides an internal combustion engine equipped with a fuel injection device 58 that injects fuel into a combustion chamber in synchronization with engine rotation. An oxidation catalyst 51 interposed in series, a trap 52 with a catalyst for collecting particulates located downstream thereof, a bypass passage 53 through which exhaust gas flows bypassing the trap 52 of the exhaust path Fr450, and a bypass passage that opens and closes. a means 55 for detecting the exhaust gas temperature downstream of the trap, and a means 55 for closing the bypass valve 54 when the exhaust gas temperature detected during trap regeneration is within a predetermined temperature range lower than the trap regeneration temperature and when the temperature is higher than the trap regeneration temperature. , a bypass vibration damping means 56 which opens the bypass valve 54 at other times, and also a bypass damping means 56 that opens the bypass valve 54 when the exhaust temperature is within the predetermined temperature range.
Regeneration fuel control in which fuel is injected during the final stage of the C-kami-kami-ne-ya-dan-bari culm or during the exhaust stroke, and the amount of injection is controlled to increase or decrease according to the exhaust temperature, and fuel injection is stopped when the temperature is outside a predetermined temperature range. means 57.

(Operation) Therefore, when the exhaust gas temperature is within a predetermined temperature range (catalyst activation temperature) during regeneration, the fuel is injected by the fuel injection device 58 at the end of the engine tension stroke or during the exhaust stroke depending on the exhaust gas temperature at that time. Exhaust gas containing a large amount of unburned fuel flows into the oxidation catalyst 51.

As this fuel passes from the high-temperature engine combustion chamber to the exhaust boat and exhaust passage, activation such as atomization and atomization is promoted.
It becomes very susceptible to oxidation.

Therefore, these are oxidized by the oxidation catalyst 51 and then reliably combusted in the catalyzed playing card 52, and the particulates are smoothly combusted in the trap 52 using the reaction heat, and no white smoke is emitted. . At this time, the amount of fuel supplied for regeneration is increased or decreased depending on the activation state of the catalyst, so the amount of regeneration fuel is increased or decreased depending on the activation state of the catalyst.
When the exhaust gas temperature is higher than the above temperature range, the particulates collected in the trap 52 will self-ignite and burn even if there is no fuel supply, so a large amount of particulates will be ignited at once. In order to prevent the trap 52 from becoming abnormally hot due to combustion, in such a case, the fuel supply is stopped and the entire amount of exhaust gas is allowed to flow into the trap 52 to carry away the combustion heat and prevent the trap 52 from burning out. To prevent.

When the exhaust gas temperature is lower than the above temperature range, a complete oxidation reaction cannot be obtained even if fuel is supplied, and white smoke is emitted. Therefore, by stopping the fuel supply and opening the bypass valve 54. , further accumulation of particulates in the trap 52 is prevented, thereby avoiding deterioration of drivability due to an increase in exhaust pressure.

On the other hand, during normal operation, unburned components <SOF> in the exhaust gas are oxidized when passing through the oxidation catalyst 51, and the heat of this reaction relatively increases the exhaust temperature, causing the particles deposited in the trap 52 to become oxidized. Opportunities for automatic regeneration due to self-ignition of the curate are increased, exhaust pressure of the engine is lowered to maintain good fuel efficiency and drivability, and the regeneration interval of the trap 52 is extended to reduce deterioration in fuel efficiency due to regeneration.

(Example) Embodiments of the present invention will be described below based on the drawings.

In Fig. 2, 1 is the engine body, 2 is an intake passage, and 3 is an exhaust passage.In the exhaust passage 3, there is a low-temperature activated honeycomb-type oxidation catalyst 4, and a particulate catalyst in the exhaust gas is located downstream of the honeycomb-type oxidation catalyst 4. A trap 5 with a trapping catalyst is provided.

Bypass passage 7 to flow exhaust gas bypassing trap 5
A bypass valve 8 is interposed in the bypass passage 7.

The bypass valve 8 is opened and closed by switching the pressure introduced into the diaphragm device 8a via the three-way solenoid valve 8b.

A fuel injection pump 6 is provided in the engine combustion chamber to inject fuel at the end of the engine compression stroke depending on the engine operating state, and as described later, this fuel injection pump 6 injects fuel at the end of the engine expansion stroke for regeneration of the trap 5. Fuel is also injected at

As shown in FIG. 3, the fuel injection pump 6 has a housing 2
A low-pressure side feed pump 22 and a high-pressure side plunger pump 23 driven by a drive shaft 24 are disposed inside the fuel pump 1, and the feed pump 22 is connected to a fuel inlet (not shown) from a fuel inlet (not shown).
The fuel sucked in is delivered to a pump chamber 25 inside the housing 21 and guided to the plunger pump 23 through a suction passage 26 that opens into the pump chamber 25.

The plunger 27 of the plunger pump 23 has suction grooves 28 extending in the axial direction around the tip, the same number as the number of cylinders, and a face cam 29 having the same number of cam ridges on the base end. The two face cams rotate together with the drive shaft 24 and lift while climbing over the rollers 31 disposed on the roller ring 30.

Therefore, the plunger 27 reciprocates while rotating, and as it exits, the plunger chamber 32 is removed from the suction groove 28.
When the plunger enters the plunger, the fuel sucked into the plunger chamber 32 is sent under pressure from a distribution boat (not shown) passing through the plunger chamber 32 to the fuel injection nozzle of each cylinder through a delivery valve.

In order to control the injection timing and amount of fuel, a high-speed electromagnetic control valve 34 is interposed in the middle of a fuel circuit 33 that returns fuel from the plunger chamber 32 to the low-pressure pump chamber 25.

By opening and closing the electromagnetic control valve 34, the plunger chamber 32 is selectively opened.

When the electromagnetic control valve 34 closes during the compression stroke of the plunger 27, fuel injection is started, and when the electromagnetic control valve 34 is opened, the injection ends. However, the injection amount is also controlled according to the valve closing period.

The control unit 10 operates this fuel fA and the injection pump 6 near the end of the compression stroke of the engine to perform main injection, and also operates it at the end of the expansion stroke or during the exhaust stroke to perform sub-injection of regeneration fuel. will be provided.

-7-, l-1 (N+4) When the amount of particulates collected in the trap 5 reaches a predetermined value, then The trap 5 is regenerated while controlling the injection amount of regeneration fuel and the operation of the bypass valve 8 according to the exhaust temperature of the trap 5.

A control unit 10 composed of a microcomputer receives a rotation speed signal Ne from an engine rotation speed sensor 11 and a fuel injection pump 6 as signals representative of operating conditions.
The fuel injection amount signal Q from the lever opening sensor 13, the cooling water temperature signal Tw from the engine cooling water temperature sensor 14, and the exhaust temperature sensor 15 installed in the exhaust passage 3 between the oxidation catalyst 4 and the trap 5. The exhaust temperature signal Tin, the exhaust temperature signal Tout from the exhaust temperature sensor 12 installed downstream of the trap 5, and the differential pressure signal ΔP from the differential pressure sensor 16 that detects the difference in exhaust pressure between upstream and downstream of the trap 5 are input, Based on these, the regeneration control of the trap 5 as shown in the flowchart of FIG. 4 is executed.

In FIG. 4, various detection signals Ne, Q, T-,
After reading Tin, Tout, and ΔP and first determining whether or not playback is in progress, S3 determines whether the playback time has been reached.
This is determined by comparing ΔP with the allowable value, which increases with the amount of particulates deposited.

When a predetermined amount of particulates have accumulated and it is time for regeneration, the regeneration flag is turned on in S4, and it is determined in S5 whether the cooling water temperature Tw is 60° C. or higher. If the temperature is 60℃ or higher, it is assumed that the engine has warmed up and the process proceeds to S6.
It is determined whether the trap outlet exhaust gas temperature Tout has reached 500° C., which is the lower limit of the self-regeneration temperature.

If it is below 500℃, then the trap inlet minus 1 air temperature T
In, first, S7 determines whether or not it is above 300°C (lower limit value), and if it is above, the bypass valve 8 is closed and the regeneration time is counted, and S7 corresponds to the upper limit value of fuel supply for regeneration. Compare with 500℃.

When it is below this upper limit, that is, as shown in Figure 5 (a),
When the trap inlet exhaust temperature is in the range of 300'C to 500°C, SIO to S12 adjust the fuel f+ based on the rotational speed at that time according to the map shown in Figure 6 (aHb).
The injection amount Qf is searched, and the fuel injection amount correction coefficient KQ is searched based on the Trump exit exhaust gas temperature, and the fuel injection amount Q2 is calculated as KQXQf.

The fuel injection amount Qf is the amount of injection per injection, and is constant regardless of the rotation speed.On the other hand, the correction coefficient KQ indicates that when the exhaust gas temperature at the trap exit is in the range of 300 to 400°C, the catalyst in the trap 5 is not sufficiently activated. Since it is activated, KQ is set to 1 to supply the necessary and sufficient amount of fuel for regeneration.
In the range of 200 to 300°C, the conversion efficiency of the catalyst in trap 5 is low and white smoke is generated, so in order to prevent this, the coefficient is increased as the conversion efficiency increases ( Furthermore, in the range of 400 to 500°C, fuel reduction is corrected to prevent burnout of the trap 5 and deterioration of the catalyst, so that KQ is set to a value of 1 or less, such that the temperature rises. t・gatte (fuka f small)
fJ-Raka Otsugami KO=1171 Set to a lower value.

On the other hand, if the cooling water temperature is below the set value in S5, 5S1
Proceed to step 4, and set the trap inlet exhaust temperature to the fuel supply upper limit value (5
00℃), and when it is lower than this, Trap 5
It is determined that combustion cannot be carried out at this time, and the process proceeds to S21, where the bypass valve 8 is opened. Similarly, even if the cooling water temperature is above the set value, when the trap inlet exhaust temperature is lower than 300°C (lower limit).

Moving from S7 to 321, the bypass valve 8 is opened to prevent further accumulation of particulates on the tiger knob 5.

Note that when the trap inlet exhaust temperature is higher than the upper limit value in S14, regeneration is possible without supplying fuel, so the S
At 15, the bypass valve 8 is closed, and the regeneration time is set to 1, and the process proceeds to 31B.

In addition, when the trap outlet exhaust temperature is 500°C higher than the trap outlet exhaust temperature in S6, the bypass valve 8 is closed in S22 and the regeneration time is counted, and the process proceeds to 313. Similarly, in S9 the trap inlet exhaust temperature is 50N. When L″1t came,
White - Since regeneration is possible, proceed to S13 while flowing the entire amount of exhaust gas to the traps without directly supplying fuel.

Then, in 313, it is checked whether the playback time count value has reached a predetermined time, and the S
Return to step 1 and repeat the above operation.

When the predetermined regeneration time has elapsed, the process proceeds to S16, where the timer for counting the regeneration time is reset, the regeneration flag is turned off, and the process proceeds to normal operation control from S17 onwards.

This is the same as when it is determined in S3 that the regeneration time has not been reached, and the operating range is searched based on the rotation speed Ne and load (fuel injection amount Q) according to the map shown in Fig. 5(b). I do.

It is determined in S18 whether or not it is in region A, and if the rotation speed and load are both high in region A, the process proceeds to S20 and the bypass valve 8 is closed.On the other hand, if the rotation speed and load are in region B where the rotation speed and load are low, In S19, the trap outlet exhaust temperature is determined and set to 500℃.
When it is higher than -, the process moves to S20 and the bypass valve 8 is closed, but when it is lower, the process moves to S21 and the bypass valve 8 is opened.

When the bypass valve 8 is closed, such as when the load is high, all exhaust gas flows to the trap 5 and particulates are collected.In contrast, at low loads where there is a large amount of unburned components (SOF) but little carbon generation. When the bypass valve 8 is opened, the SOF is oxidized by the oxidation catalyst 4. However, when the exhaust gas temperature at the trap exit is high, there is a risk of burnout of the trap 5, so the bypass valve 8 is closed and the entire amount of exhaust gas is oxidized. The heat from trap 5 is carried away by flowing into trap 5.

Next, the overall effect will be explained.

First, FIG. 7 shows the injection characteristics of the fuel injection pump 6.
During regeneration, in addition to main injection Q1 performed near compression top dead center, sub-injection Q2 as regeneration fuel is performed at the end of the expansion stroke (or during the exhaust stroke).

As described above, this is done by closing the electromagnetic control valve 14 at the end of the expansion stroke, and in this case, the fuel by the sub-injection Q2 is completely combusted because combustion in the combustion chamber is almost completed. When the exhaust valve opens in the next exhaust stroke, the gas is discharged into the exhaust passage 3 while containing many unburned components.

Therefore, when this unburned fuel reaches the oxidation catalyst 4,
The oxidation reaction takes place in the same way as above, but in this case, the activation of atomization, atomization, etc. of the fuel is greatly promoted as it passes through the exhaust boat from the high-temperature combustion chamber, so the oxidation catalyst 4
The reaction becomes extremely good, and even when the exhaust temperature conditions are poor, the generation of white smoke can be reliably avoided.

This sub-injection control is performed by calculating the fuel injection amount Q2 according to the exhaust temperature in steps 810 to S12 in the flowchart of FIG. 4 described above, and injecting this Q2 at the end of the fi expansion stroke. good.

Next, when the amount of accumulated particulates collected in the trap 5 reaches a predetermined value, a regeneration operation is performed, but in this case, after warming up the engine, , that is, the trap inlet exhaust temperature is 300°C to 500°C.
In this range, regeneration is performed while supplying regenerated fuel.

In this case, the amount of fuel supplied is controlled to decrease by 1 in accordance with the trap outlet exhaust temperature, as shown in FIG. In the range of ~400℃, the amount of fuel is necessary and sufficient to burn particulates, but if it is lower than that, the oxidation of the fuel will be insufficient, so the reduction should be corrected according to the catalyst conversion efficiency. However, by stopping the supply at temperatures below 200°C, the generation of white smoke is prevented.

Furthermore, when the temperature exceeds 400°C, there is a danger that the temperature of the trap 5 will rise too much, so to prevent burnout, the amount of fuel is reduced, and when the temperature exceeds 500°C, the fuel supply is stopped.

Figure 5(c) shows the exhaust temperature when regeneration fuel is supplied (
However, when a fixed amount of fuel is supplied, the temperature increases relatively compared to when no fuel is supplied, as shown by the dotted line. When the fuel supply amount is controlled according to the exhaust temperature, the temperature rise is kept to the minimum necessary for regeneration in the trap 5, and the temperature may become unnecessarily high or fuel may be wasted. There is no.

The fuel introduced into the exhaust gas in this way is oxidized by the low-temperature activated oxidation catalyst 4, and then flows into the trap 5, where it further undergoes an oxidation reaction, and the particulate matter collected by the reaction heat is In addition, the amount of regenerating fuel supplied is appropriately controlled according to the trap outlet exhaust temperature in consideration of the conversion efficiency of the trap 5 catalyst, resulting in good fuel consumption efficiency. Can be played.

In addition, the trap inlet exhaust temperature and outlet exhaust temperature are 500℃.
When the exhaust gas exceeds the limit, regeneration is carried out smoothly without supplying fuel, but in this case, by closing the bypass valve 8 and allowing the entire amount of exhaust gas to flow into the trap 5, a large amount of particulates are combusted all at once. The high fever that sometimes occurs,
It is carried away by exhaust gas to avoid burnout or the like due to abnormally high temperature of the trap 5.

On the other hand, if warm-up is not completed or even after the warm-up is completed but the exhaust gas temperature at the trap inlet is below 300°C, the fuel cannot be completely oxidized even if the fuel is supplied upstream of the oxidation catalyst 4, and it is emitted as white smoke. Therefore, in such a case, no regeneration operation is performed even if the regeneration time has been reached.

However, if left as is, the trap 5, on which a large amount of particulates have already accumulated, may become further clogged and the engine operability may be significantly impaired due to an excessive increase in exhaust pressure, so the bypass valve 8 is opened. While avoiding the deterioration of engine performance for the time being, the oxidation catalyst
While reducing the center, wait for the exhaust temperature to rise to a temperature suitable for regeneration.

On the other hand, during normal operation of the engine, that is, when the trap 5 is not regenerated, the bypass valve 8 is
The oxidation catalyst 4 is closed and the particulates in the exhaust are captured by the trap 5. However, in low load ranges where there are few particulates in the exhaust and the main component is SOF, which is an unburnt component, the oxidation catalyst 4 is closed. By allowing the fuel to pass through, these oxidation can be performed reliably, and by opening the bypass valve 8, the exhaust pressure during operation can be lowered, and fuel efficiency and drivability can be maintained favorably.

In addition, since the oxidation catalyst 4 is located at a high temperature part of the exhaust gas upstream of the trap 5, a good reaction can be maintained, and during operation with the bypass valve 8 closed, the oxidation reaction heat of unburned components flows into the trap 5. By relatively increasing the exhaust temperature, it is possible to promote self-ignition of the accumulated particulates. Therefore, even if the regeneration period has not been reached, the collected particulates will automatically ignite if the conditions are good. combusts, thus increasing the required regeneration interval of trap 5;
Furthermore, the reduction in exhaust pressure also minimizes deterioration in fuel efficiency and drivability.

(Effects of the Invention) As described above, according to the present invention, when regenerating a trap, fuel is injected into the engine combustion chamber at the end of the engine expansion stroke or during the exhaust stroke depending on the exhaust gas temperature, and the fuel is activated to be easily combusted. Since the oxidized fuel is supplied to the catalytic trap via the oxidation catalyst, the supplied fuel can be reliably oxidized by the catalyst, and the heat of this oxidation reaction can be used to smoothly burn the collected particulates. Moreover, the amount of regenerated fuel supplied is controlled to increase or decrease according to the exhaust temperature, in other words, according to the catalyst activation state, so regeneration is performed with the most efficient fuel consumption without producing white smoke or the like. be.

On the other hand, when the exhaust temperature is high enough to cause self-ignition, the fuel supply is stopped to avoid trap burnout due to excessive combustion.
In addition, when the exhaust temperature is low and the regeneration temperature cannot be secured even if fuel is supplied, the fuel supply is stopped to prevent the generation of white smoke, and by bypassing the trap and allowing the exhaust to flow, it is possible to prevent trap clogging. Deterioration of engine drivability due to this can be avoided.

In addition, during normal operation, the oxidation catalyst purifies the unburned components contained in the exhaust gas, and the reaction heat can be used to promote self-ignition of the particulates captured in the trap, which allows the regeneration timing to be Even if this is not the case, the trap can self-regenerate, extending the required regeneration interval and preventing deterioration in fuel efficiency and drivability.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of the present invention, FIG. 2 is a schematic configuration diagram showing an embodiment thereof, FIG. 3 is a sectional view of a fuel injection pump, and FIG. 4 is a flowchart of control operations executed by a control unit. Fig. 5(a) is a characteristic diagram showing the region in which recycled fuel is supplied during regeneration. Fig. 5(b) is a characteristic diagram showing the region in which the bypass valve is operated. Fig. 5(e) is a characteristic diagram showing the region in which recycled fuel is supplied during regeneration. A characteristic diagram showing the temperature rise when supplied, Figure 6 (a) is a characteristic diagram of the amount of fuel for regeneration, Figure 6 (b) is a characteristic diagram showing the correction coefficient depending on temperature, and Figure 7 is a characteristic diagram of the fuel injection pump. FIG. 3 is an operational characteristic diagram showing fuel injection. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake passage, 3... Exhaust passage, 4... Oxidation catalyst, 5... Trap, 6... Fuel injection pump, 7... Bypass passage, 8 ...Bypass valve, 10...Control unit, 12.15.
...Exhaust temperature sensor, 16...Differential pressure sensor, 34...
・Solenoid control valve. Figure 382e Figure Ms6 (a) Double drying ridge a (b) Tora Noah exit water 1J1

Claims (1)

[Claims] 1. In an internal combustion engine equipped with a fuel injection device that injects fuel into a combustion chamber in synchronization with engine rotation, an oxidation catalyst is installed in series in the exhaust passage and a trap with a catalyst for collecting particulates is located downstream of the oxidation catalyst. a bypass passage that allows exhaust to flow around the trap in the exhaust passage; a bypass valve that opens and closes the bypass passage; a means for detecting the exhaust temperature downstream of the trap; bypass control means that closes a bypass valve when the temperature is within a low predetermined temperature range and when the temperature is higher than the predetermined temperature range; and a bypass control means that opens the bypass valve at other times; regenerated fuel control means for injecting fuel at the end of the engine expansion stroke or during the exhaust stroke, controlling the injection amount to increase or decrease according to the exhaust temperature, and stopping fuel injection when the temperature is outside a predetermined temperature range. An exhaust treatment device for an internal combustion engine, characterized by: