JP2003201836A - Fuel supply device for catalyst for exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device for a catalyst for exhaust gas which suppresses the production of deposit around the jet hole of an injection nozzle. <P>SOLUTION: The invention includes an electronic control device 25 which injects the fuel into an exhaust port 6d from the injection nozzle 5 in order to secure the exhaust gas purifying action of the catalyst 12 in the operating region in which the catalyst 12 is below its activating temperature. On the other hand, in the operating region in which the catalyst 12 temperature is over the activation level, the control device 25 executes the injection of the fuel appropriately. With this injection of fuel, the tip temperature of the injection nozzle 5 lowers, and production of deposit is suppressed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust catalyst fuel supply device for supplying fuel to an exhaust system of an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in order to reduce NOx contained in exhaust gas, an internal combustion engine uses an exhaust gas recirculation device (hereinafter referred to as EG).
R device) is installed. Although it has been possible to reduce the generation of NOx by such measures, it has not yet been eliminated, and exhaust gas still contains NOx. Therefore, in recent years, a NOx reduction catalyst that reduces NOx in the exhaust gas has been developed, and by using it together with the above measures, the amount of NOx released into the atmosphere is further reduced.

In an internal combustion engine equipped with this NOx reduction catalyst, in order to improve the NOx purification rate of the NOx reduction catalyst, for example, as described in Japanese Patent Laid-Open No. 2001-280125, the injection provided in the cylinder head is performed. Fuel is injected from the nozzle toward the exhaust port and supplied to the NOx reduction catalyst.

Further, the exhaust contains soot produced by incomplete combustion of fuel, etc., and when the exhaust passes through the catalyst, a part of such soot adheres to the catalyst. If this soot is excessively deposited on the catalyst, the pressure loss of the exhaust system increases, the EGR rate rises, and the exhaust emission deteriorates. Further, when the excessively accumulated soot self-ignites, its combustion temperature becomes extremely high, which may cause a problem that the catalyst bed is damaged. However, when the exhaust temperature is high, this soot self-ignites and burns, so that the accumulation of soot on the catalyst is suppressed.
On the other hand, when the exhaust temperature is low, the soot does not self-ignite and its combustion is not promoted, so that the accumulation of soot on the catalyst increases. Therefore, in an operating state in which the exhaust temperature becomes low, fuel is supplied to the exhaust system, and the temperature of the catalyst is raised by burning this fuel with a catalyst, thereby promoting the self-ignition of soot adhering to the catalyst. Has been done.

[0005]

By thus providing the injection nozzle for supplying fuel to the exhaust system of the internal combustion engine, the NOx purification rate can be improved and the soot adhering to the catalyst can be removed. However, since the tip of this injection nozzle is exposed in the exhaust passage, the following problems cannot be ignored.

After injecting the fuel from the injection nozzle, a lag is left at the tip of the nozzle. Further, since the tip of the injection nozzle is exposed in the exhaust passage, soot in the exhaust adheres to the tip of the nozzle. The liquid HC contained in these drip and soot deteriorates and solidifies when the exhaust temperature rises,
This becomes a so-called deposit, which reduces the opening area of the injection hole at the tip of the injection nozzle. If the opening area of the injection hole becomes small as described above, not only a sufficient amount of fuel cannot be supplied, but also the fuel itself cannot be supplied.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel supply device for an exhaust catalyst capable of suppressing the generation of deposits in the vicinity of the injection hole of an injection nozzle. It is in.

[0008]

[Means for Solving the Problems] Means for attaining the above-mentioned objects and their effects will be described below. The invention according to claim 1 is provided with an injection nozzle that is provided in an exhaust system of an internal combustion engine and injects fuel to a catalyst, and when the catalyst is in an activation temperature region where the catalyst is activated, A fuel supply device for an exhaust catalyst that performs injection supply, comprising injection control means that performs injection supply of the fuel by the injection nozzle when the catalyst is in a high temperature region higher than the activation temperature region. Is the gist.

According to this structure, the fuel is injected and supplied from the injection nozzle to the catalyst when it is in the activation temperature range where the catalyst is activated. By supplying this fuel, the exhaust gas purifying action of the catalyst can be suitably exerted. On the other hand, even when the catalyst is in a high temperature region that is higher than the activation temperature region, such fuel injection supply is performed. In this case, heat of vaporization is taken from the injection nozzle as the fuel vaporizes, so that the tip temperature of the injection nozzle (temperature near the injection hole) decreases. Further, the fuel is atomized by being injected, and the atomized fuel is vaporized to lower the ambient temperature near the tip of the injection nozzle. In addition, the vaporized fuel forms a heat insulating layer in the vicinity of the tip of the injection nozzle to suppress direct exposure of the nozzle tip to high temperature exhaust gas. Thus, by intentionally injecting and supplying the fuel even in the temperature range higher than the activation temperature range of the catalyst, the tip temperature of the injection nozzle can be lowered, and the soot after the fuel deteriorates and solidifies. It becomes possible to suppress the generation of deposits and suppress the generation of deposits near the injection holes. Further, the fuel supplied by injection melts the rear dribble soot adhering to the vicinity of the injection hole, so that it is possible to suppress the generation of deposits near the injection hole.

According to a second aspect of the present invention, an injection nozzle provided in the exhaust system of the internal combustion engine for injecting fuel to the catalyst is provided, and the temperature of the catalyst is higher than the self-ignition temperature of soot adhering to the catalyst. In a fuel supply device for an exhaust catalyst that executes fuel injection supply by the injection nozzle when in a low low temperature region, when the catalyst is in a high temperature region that is higher than the low temperature region, The gist of the invention is to include an injection control unit that executes injection supply.

According to this structure, fuel is injected and supplied from the injection nozzle to the catalyst when the temperature of the catalyst is in a low temperature range lower than the self-ignition temperature of the soot adhering to the catalyst. By the supply of this fuel, the self-ignition of soot adhering to the catalyst can be properly performed. On the other hand, even when the catalyst is in the high temperature region higher than the low temperature region, such fuel injection supply is performed. And in this case,
Since the heat of vaporization is taken from the injection nozzle as the fuel vaporizes, the temperature at the tip of the injection nozzle (the temperature near the injection hole) decreases. Also, the fuel is atomized by being injected, and the atomized fuel is vaporized,
The ambient temperature near the tip of the injection nozzle is lowered. In addition, the vaporized fuel forms a heat insulating layer in the vicinity of the tip of the injection nozzle to suppress direct exposure of the nozzle tip to high temperature exhaust gas. As described above, by intentionally injecting and supplying the fuel even in the temperature region higher than the low temperature region, the tip temperature of the injection nozzle can be lowered, and the deterioration and solidification of the soot after the fuel can be suppressed. As a result, it becomes possible to suppress the generation of deposits near the injection holes. Further, the fuel supplied by injection melts the rear dribble soot adhering to the vicinity of the injection hole, so that it is possible to suppress the generation of deposits near the injection hole.

According to a third aspect of the present invention, in the fuel supply device for the exhaust catalyst according to the first or second aspect, the injection control means is such that the catalyst is in the high temperature region based on an engine operating state. It is the gist to judge.

According to this construction, it can be accurately judged that the catalyst is in the high temperature range based on the engine operating state. Therefore, when the catalyst is in the high range, the exhaust gas purification action of the catalyst when setting the fuel injection supply mode is performed. Alternatively, it becomes possible to prioritize the suppression of deposit generation in the injection nozzle over the removal of soot, and it is possible to suppress the generation more favorably.

According to a fourth aspect of the present invention, there is provided an injection nozzle provided in an exhaust system of an internal combustion engine for injecting fuel to a catalyst, and the injection nozzle is provided when the catalyst is in an activation temperature range in which the catalyst is activated. In the fuel supply device for the exhaust catalyst, which intermittently executes the fuel injection supply by the injection period and the injection interval set based on the engine operating state, the injection period set from the set injection period during the set injection interval. The gist of the invention is to include an injection control unit that performs fuel injection supply in a short injection period.

When the injection for exhaust gas purification action by the catalyst is not executed for a long period of time, even if the tip temperature of the injection nozzle is relatively low, the generation of deposits gradually progresses, and there is a possibility that the injection hole may be blocked. is there. According to this configuration, a small amount of fuel is injected during the fuel injection interval set based on the engine operating state, that is, even when fuel injection for the exhaust gas purification action of the catalyst is not performed. for that reason,
Before any fuel or soot is solidified, it is scattered or dissolved and removed from the vicinity of the injection hole. Therefore, it becomes possible to suppress the generation of deposits.

According to a fifth aspect of the present invention, there is provided an injection nozzle provided in the exhaust system of the internal combustion engine to inject fuel to the catalyst, and the temperature of the catalyst is higher than the self-ignition temperature of soot adhering to the catalyst. In the fuel supply device for the exhaust catalyst, which performs the fuel injection supply by the injection nozzle intermittently with the injection period and the injection interval set based on the engine operating state when in the low low temperature region, the set injection The gist of the invention is to include an injection control unit that performs fuel injection supply during an injection period that is shorter than the set injection period during the interval.

When the injection for removing the soot adhering to the catalyst is not executed for a long period of time, even if the tip temperature of the injection nozzle is relatively low, the generation of deposits gradually progresses,
The injection hole may be blocked. According to the configuration,
A small amount of fuel injection is performed during the fuel injection interval set based on the engine operating state, that is, even when fuel injection for removing soot adhering to the catalyst is not performed. Therefore, before the fuel or soot in the tail is scattered or dissolved, the fuel or soot is removed from the vicinity of the injection hole. Therefore, it becomes possible to suppress the generation of deposits.

According to a sixth aspect of the present invention, in the exhaust catalyst fuel supply apparatus according to the third aspect, the engine operating state includes accelerator opening, throttle opening, EGR valve opening, and oxygen in exhaust gas. At least one of the concentration, the NOx concentration in the exhaust gas, the THC concentration in the exhaust gas, the pressure in the exhaust passage, and the engine speed are detected.

There is a close correlation between the exhaust gas temperature and the solidification of the deposit, and the solidification of the deposit is promoted as the exhaust gas temperature increases. Further, the exhaust gas temperature has a close correlation with the engine load and the engine rotation speed, and the exhaust gas temperature increases as the load and engine speed increase.

According to the above construction, as the engine operating state representing the engine load, accelerator opening, throttle opening, EGR valve opening, oxygen concentration in exhaust gas, NOx concentration in exhaust gas, THC concentration in exhaust gas (molecular weight) Different total HC concentration) and at least one of the pressures in the exhaust passage are detected, and the engine speed is also detected. Therefore, it is possible to estimate the exhaust gas temperature by utilizing these detected values, and it is possible to reliably obtain the action and effect of the invention described in claim 3.

The seventh aspect of the present invention is summarized as follows: in the exhaust catalyst fuel supply apparatus according to the third aspect, the exhaust temperature is detected as the engine operating state.
According to this configuration, the exhaust gas temperature, which has a close correlation with the solidification of the deposit, is directly detected, so that the action and effect of the invention according to claim 3 can be reliably obtained.

The invention according to claim 8 is summarized in the fuel supply device for an exhaust catalyst according to claim 3, wherein the fuel injection amount is detected as the engine operating state. According to this configuration, the fuel injection amount is detected as the engine operating state. Since the fuel injection amount has a correlation with the engine heat generated in the engine combustion chamber, the fuel injection amount can be detected and the exhaust gas temperature can be estimated, and the effect of the invention according to claim 2 can be ensured. Can be obtained.

The invention described in claim 9 is from claim 1 to claim 8.
In the fuel supply device for an exhaust gas catalyst according to any one of the above items, the injection control unit forms an exhaust flow in a direction opposite to a direction of fuel injected from the injection nozzle in the exhaust system by pressure pulsation of exhaust gas. The gist of the invention is to temporarily suspend the injection and supply of fuel by the injection nozzle.
When the exhaust flow in the direction opposite to the direction of the fuel injected from the injection nozzle is formed in the exhaust system by the pressure pulsation of the exhaust nozzle, the soot in the exhaust floating near the tip of the injection nozzle will be The generated mist-like fuel adheres and its particle size increases. Then, the soot having the increased particle size may be attached to the tip of the injection nozzle by the exhaust flow, which may promote the clogging of the injection hole due to the generation of deposits.

According to this structure, even during the fuel injection period, when the exhaust flow in the direction opposite to the direction of the fuel injected from the injection nozzle is formed in the exhaust system by the pressure pulsation of the exhaust, the injection is performed. Since the suspension is temporarily stopped, it is possible to suppress the promotion of blockage in the injection hole as described above.

According to a tenth aspect of the present invention, in the fuel supply device for the exhaust catalyst according to any of the first to ninth aspects, the injection nozzle is provided in an exhaust system corresponding to a specific cylinder of the internal combustion engine. The gist of the injection control means is to set the injection and supply timing of the fuel based on the exhaust timing of the specific cylinder.

According to this construction, the fuel injection and supply timing is set based on the exhaust timing in the specific cylinder. Therefore, when the tip temperature of the nozzle becomes the highest, for example, the exhaust valve is opened. Suitable for lowering the temperature of the tip of the injection nozzle by detecting when the tip of the injection nozzle is exposed to the exhaust gas discharged to the exhaust passage of the specific cylinder along with the valve and injecting fuel at this time. It becomes possible to inject and supply fuel at the time.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment in which a fuel supply device for an exhaust catalyst according to the present invention is embodied in a common rail type four-cylinder diesel engine mounted on an automobile will be described below. It will be described in detail with reference to FIGS.

FIG. 1 is a schematic configuration diagram showing a fuel supply device for an exhaust catalyst according to the present embodiment, an engine 1 to which the fuel supply device is applied, and peripheral configurations thereof. The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4a to 4d are attached to the cylinder head 2. These fuel injection valves 4a to 4d are used for the cylinders # 1 to #, respectively.
Fuel is injected into the cylinder of No. 4. Also, the cylinder head 2
Includes an intake port (not shown) for introducing outside air into the cylinder and an exhaust port 6 for discharging combustion gas outside the cylinder.
a to 6d are provided corresponding to the cylinders # 1 to # 4.

The fuel injection valves 4a-4d are connected to a common rail 9 for accumulating high pressure fuel. Common rail 9
Is connected to the supply pump 10. The supply pump 10 sucks fuel in a fuel tank (not shown) and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is supplied to each of the fuel injection valves 4a-4d.
When the valve is opened, the fuel is injected into the cylinder from the injection valves 4a to 4d.

An intake manifold 7 is connected to the intake port (not shown). The intake manifold 7 is connected to the intake passage 3. A throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a-6d. The exhaust manifold 8 is connected to the exhaust passage 26. Exhaust passage 26
A catalyst 12 for reducing NOx is installed midway. This catalyst 12 is a NOx occlusion reduction type catalyst,
When the air-fuel ratio of the exhaust is lean, it stores NOx in the exhaust,
When the air-fuel ratio becomes rich, the stored NOx is reduced and the same N
Decompose Ox. In the case of a diesel engine, the air-fuel ratio of the exhaust gas is usually lean, so it is necessary to make the air-fuel ratio of the exhaust gas rich before the NOx storage amount of the catalyst 12 reaches the limit. Therefore, NO is supplied to the fuel from the injection nozzle 5 described later.
By injecting as x fuel, the air-fuel ratio of the exhaust is made rich. When this process is performed, the NOx storage amount of the catalyst 12 is estimated based on the operating state of the engine 1, the elapsed time after performing NOx reduction, and the like. When this estimated amount exceeds a predetermined amount, fuel is injected from the injection nozzle 5, NOx is released from the catalyst 12, and the same NO
Reduction of x takes place. The injection period and injection interval of the fuel injected at this time are set based on the operating state of the engine 1, the previous fuel injection amount, and the like.

In addition to this, the engine 1 is equipped with an EGR device. This EGR device lowers the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air to reduce NOx.
This is a device that reduces the amount of generation. This device includes an EGR passage 13, which connects the intake passage 3 and the exhaust passage 26,
EGR valve 15 and EGR cooler 1 provided in the R passage 13
It is composed of four. The EGR valve 15 adjusts the opening thereof to adjust the amount of exhaust gas introduced from the exhaust passage 26 to the intake passage 3 (EGR amount). EGR cooler 1
4 reduces the temperature of the exhaust gas flowing in the EGR passage 13.

Further, the engine 1 uses the exhaust pressure to supercharge the intake air introduced into the cylinders.
Is equipped with. An intercooler 18 is provided in the intake passage 3 between the intake-side turbine (not shown) and the throttle valve 16 in order to reduce the temperature of intake air that rises due to supercharging of the turbocharger 11. .

The engine 1 is equipped with various sensors for detecting the engine operating state. For example, the air flow meter 19 detects the amount of intake air in the intake passage 3. The throttle opening sensor 20 detects the opening of the throttle valve 16. The air-fuel ratio sensor 21 detects the air-fuel ratio of exhaust gas. The exhaust temperature sensor 29 detects the exhaust temperature on the downstream side of the catalyst 12. The cylinder discrimination sensor 22 detects the compression top dead center of the specific cylinder. The crank angle sensor 23 detects a rotation angle of a crank shaft (not shown). Further, the crankshaft angle of any cylinder is detected by the output values of the cylinder discrimination sensor 22 and the crank angle sensor 23. The accelerator opening sensor 24 detects the opening of an accelerator pedal (not shown).

The outputs of these various sensors are input to an electronic control unit (hereinafter referred to as ECU) 25. This E
The CU 25 is a read-only memory (RO) that stores in advance a central processing control unit (CPU), various programs, maps and the like.
M), a random access memory (RAM) for temporarily storing calculation results of the CPU, a timer counter, an input interface, an output interface, and the like. Then, by the ECU 25, for example, the fuel injection amount and the fuel injection timing of the fuel injection valves 4a to 4d, the discharge pressure of the supply pump 10, the drive amount of the actuator 17 for opening and closing the throttle valve 16, the opening degree of the EGR valve 15, and the like, Various controls of the engine 1 are performed.

Next, the fuel supply device for the exhaust catalyst according to this embodiment will be described. First, the fuel supply device for the present exhaust catalyst is a device for supplying the fuel used for NOx reduction in the catalyst 12 to the exhaust.

An injection nozzle 5 for supplying fuel to the catalyst 12 is attached to the cylinder head 2. Fuel is injected as fuel from the injection nozzle 5 into the exhaust port 6d of the fourth cylinder # 4. Further, the injection nozzle 5 and the supply pump 10 are connected by a fuel supply pipe 27, and light oil is supplied. The injection nozzle 5 has the same structure as the fuel injection valves 4a to 4d, and the ECU 25 controls the injection amount and injection timing.

FIG. 2 is a sectional view of the exhaust port 6d. An injection hole 28 for injecting fuel is provided at the tip of the injection nozzle 5.
Are formed. The injection hole 28 opens toward the downstream side of the exhaust passage 26. Further, the tip of the injection nozzle 5 is buried in the wall surface of the exhaust port 6d to prevent the deposit from adhering and reduce the exhaust resistance.

The ECU 25 stores a map for setting the fuel injection period and the injection interval based on the accelerator opening and the engine rotation speed. The injection period and the injection set based on this map are stored. Fuel injection from the injection nozzle 5 is controlled according to the interval.

By the way, in this fuel supply system,
If the fuel adhering to the injection hole 28 and the soot in the exhaust gas solidify due to the back-drip and become a deposit to block the injection hole 28, the fuel injection amount may decrease. In the present fuel supply device, the injection condition and the injection mode of the fuel are appropriately set in order to suppress the decrease in the injection amount due to the generation of the deposit. Hereinafter, the relationship between the engine operating state, the exhaust temperature, the nozzle tip temperature, and the flow rate decrease rate, and the fuel injection control mode based on the relationship will be described.

FIG. 3 is a graph showing the tendency of the exhaust temperature with respect to the engine rotation speed and the output torque (load). As shown in the figure, the exhaust temperature rises as the load increases and the rotation speed increases. Also, the broken line in the figure shows the entire engine operating region, and the alternate long and short dash line shows the maximum output torque at a certain engine speed. The shaded area in the figure is the region where fuel injection for NOx reduction is performed. Since the catalyst 12 has a temperature range in which it exhibits an activating action, that is, a so-called temperature window, if the exhaust temperature is too high, even if fuel is injected, NO
The reduction of x is not promoted. Therefore, fuel is not injected in an operating region where the exhaust temperature exceeds the NOx reduction upper limit temperature (in the figure, a white portion surrounded by a broken line showing the entire engine operating region and a curve showing the NOx reduction upper limit temperature).

In addition to the upper limit temperature, the catalyst 1
Fuel is not injected even when the temperature of 2 becomes a temperature equal to or lower than the temperature window. Here, the exhaust temperature becomes lower as the load becomes lower and the rotation speed becomes lower. Therefore, in the region where the load and the engine speed both decrease, the catalyst 12 is basically inactive and fuel should not be injected. However, for example, when the vehicle enters an idle state after normal running, the exhaust gas temperature decreases, but the temperature of the catalyst 12 itself does not immediately decrease due to its heat capacity, and NOx remains for a while even in the low load low rotation state.
In some cases, reduction is possible. Therefore, in the engine 1 used in the present experiment, the elapsed time after the predetermined low load and low rotation is measured by a timer counter or the like, and if the elapsed time does not reach the predetermined time, the temperature of the catalyst 12 is the temperature. If it is estimated that the exhaust gas is in the window or the exhaust gas temperature detected by the exhaust gas temperature sensor 29 is high, the catalyst 1
It is estimated that the temperature of No. 2 is in the temperature window, and the fuel is injected even at low load and low rotation.

FIG. 4 shows the relationship between the exhaust temperature and the tip temperature of the injection nozzle 5. Further, FIG. 5 shows the relationship between the tip temperature and the flow rate decrease rate when the nozzle tip temperature is gradually increased. Here, the flow rate decrease rate is
It is the ratio between the set fuel injection amount and the actually injected fuel injection amount, and the higher the flow rate reduction rate, the smaller the amount of fuel actually injected.

As shown in FIG. 4, the nozzle tip temperature tends to rise as the exhaust temperature rises. Also in FIG.
As shown in FIG.
When 2 exceeds the NOx reduction upper limit temperature, when the nozzle tip temperature THA1 is exceeded, the flow rate decreases, and the flow rate decrease rate tends to increase as the temperature increases thereafter.

Next, the following three patterns were set as engine operating patterns in order to search the relationship between the engine operating state and the flow rate reduction rate. Pattern L: low load and low engine speed range (N
Operation pattern pattern H only in the Ox reduction upper limit temperature or less): Operation pattern pattern L-H only in a high load high rotation range (fuel operation range above the NOx reduction upper limit temperature) in which fuel is not injected Operation pattern in which a low load low rotation range and a high load high rotation range are alternately repeated FIG. 6 is a graph showing the relationship between the engine operating state and the flow rate decrease rate for the above three patterns. As shown in this figure, the flow rate decrease rate is low in the patterns L and H, but the flow rate decrease rate tends to be significantly high in the patterns L-H.

From the respective tendencies shown in FIGS. 4 to 6, the present inventors considered the process in which the flow rate reduction of the injection nozzle 5 occurs as follows. First, in the operating state of the pattern LH, the tip temperature of the injection nozzle 5 and the execution timing of fuel injection have a relationship as shown in FIG. Pattern L
In this operating state, fuel is injected, and fuel dripping remains around the injection hole 28. Further, soot in the exhaust adheres to the periphery of the injection hole 28. In this state, when the operating state becomes the pattern H, the fuel is not injected, so the injection nozzle 5
The temperature of the tip of the liquid HC rises, and the liquid HC in the soot is deteriorated and solidified, and becomes a deposit and adheres to the periphery of the injection hole 28. As shown in FIG. 8, the amount of soot in the exhaust gas (PM amount) increases as the engine operating condition increases under high load and high rotation.
It is presumed that the amount of soot adhering to the periphery of the injection nozzle 5 also increases, which promotes a decrease in the flow rate of the injection nozzle 5. As described above, when the engine 1 is operated in a manner close to the actual operating state, the flow rate of the injection nozzle 5 may decrease.

Therefore, in the present embodiment, even in the engine operating region in which the operating state in the pattern H, that is, the operating state is high load and high rotation, and the exhaust temperature is equal to or higher than the NOx reduction upper limit temperature, the injection nozzle 5 is operated. By injecting the fuel, the temperature at the nozzle tip is lowered, the generation of deposits is suppressed by the solvent action of the fuel, and the decrease in the flow rate of the injection nozzle 5 is suppressed.
That is, in the engine operating region where the exhaust temperature is equal to or higher than the NOx reduction upper limit temperature, when the fuel is injected from the injection nozzle 5, the fuel is vaporized and the latent heat thereof causes the injection nozzle 5
Tip temperature will drop. Further, the fuel is atomized by being injected, and the atomized fuel is vaporized, so that the ambient temperature near the tip of the injection nozzle 5 is lowered. Further, the vaporized fuel forms a heat insulating layer in the vicinity of the tip of the injection nozzle 5 to prevent the nozzle tip from being directly exposed to hot exhaust gas. As a result, the temperature of the tip of the injection nozzle 5 becomes low, and it becomes possible to suppress the generation of deposits and further the reduction in the flow rate of the injection nozzle 5 due to this. Further, the injected fuel acts as a solvent that dissolves the rear drip soot adhering to the vicinity of the injection hole 28, so that the solidification of the rear drip soot can be suppressed, and thus the flow rate reduction of the injection nozzle 5 can be suppressed. Hereafter, fuel injection control for suppressing such deposit generation will be described with reference to FIGS.

FIG. 9 is a flow chart showing the processing procedure for this fuel injection control, and the series of processing shown in the flow chart is executed by the ECU 25 by interruption every predetermined time.

When this processing is started, first, the accelerator opening ACCP and the engine speed NE are read (step 110). Next, it is determined whether or not the accelerator opening ACCP and the engine speed NE are equal to or more than a predetermined value (step 120). This determination is made based on whether both conditional expressions (1) and (2) are satisfied.

ACCP> α1 (1) NE> β1 (2) These predetermined values α1 and β1 are for providing the reducing action of the catalyst 12 when the operating state of the engine 1 becomes a high load and high rotation state. Accelerator opening ACCP when fuel injection is stopped
And engine rotation speed NE, which are obtained in advance by experiments or the like.

If either or both of conditional expressions (1) and (2) are not satisfied (N in step 120)
O), it is in the operating region where fuel injection for the reduction action of the catalyst 12 is performed, and this process is terminated assuming that the flow rate of the injection nozzle 5 does not decrease.

On the other hand, when both conditional expressions (1) and (2) are satisfied (YES in step 120), the map shown in FIG. 10 is referred to and the read accelerator opening ACCP and engine are read. The fuel injection period τ and the injection interval T are set based on the rotation speed NE (step 1
30). This map is stored in the ROM of the ECU 25, and the injection period τ becomes longer as the engine speed and the accelerator opening increase, and the injection interval T becomes shorter as the engine speed and the accelerator opening increase. Is set to. In this way, as the operating state of the engine 1 becomes higher under high load and higher rotation, in other words, as the exhaust temperature becomes higher, the injection period τ becomes longer, the injection interval T becomes shorter, and the fuel injected from the injection nozzle 5 becomes shorter. The quantity will increase. Therefore, as the exhaust gas temperature increases, the action of lowering the tip temperature of the injection nozzle 5 increases. In this embodiment, for example, the injection period τ is 10 to 200 mse.
The injection interval T is set between 0.3 and 60 seconds.

Next, the injection time of the injection nozzle 5 is controlled on the basis of the injection period τ and the injection interval T set as described above, and the fuel corresponding to the engine operating state is injected into the exhaust port 6d (step 140). . In the injection at this time, as shown in FIG. 11, the fuel is injected during the injection period τ and the fuel is not injected during the injection interval T.

After that, this process is repeated every predetermined time. The above fuel injection corresponds to the crank angle of the engine 1.
It is possible to lower the tip temperature of the injection nozzle 5 at any time. However, from the viewpoint of fuel consumption, it is desirable that the fuel injection aiming at suppressing the generation of such a deposit can obtain its effect by injection in the smallest possible amount. Therefore, it is desirable to perform the fuel injection in step 140 of FIG. 9 as follows.

Since the tip of the injection nozzle 5 is installed in the exhaust port 6d of the fourth cylinder # 4, the tip temperature of the injection nozzle 5 becomes highest when the fourth cylinder # 4 is in the exhaust stroke. Therefore, by injecting fuel from the injection nozzle 5 when the fourth cylinder # 4 is in the exhaust stroke, the tip temperature of the injection nozzle 5 can be maintained at a temperature as low as possible. Therefore, in the present embodiment, as shown in FIG. 12, the crankshaft has a compression top dead center TD of the fourth cylinder # 4.
The fuel injection is started when the engine rotates by a predetermined crank angle θA from C. This predetermined crank angle θA
Is set so that when the exhaust gas discharged from the fourth cylinder # 4 passes near the tip of the injection nozzle 5, a heat insulating layer due to fuel injection is already formed near the tip of the injection nozzle 5. There is. Further, since this timing changes depending on the engine rotation speed, the predetermined crank angle θ is set so as to decrease as the engine rotation speed increases.
A is variably set based on the engine rotation speed.

FIG. 13 shows an experimental result for confirming the function and effect of this embodiment. In this experiment, a plurality of the above-mentioned engines 1 are prepared, and each engine A,
When the above-mentioned fuel injection control for suppressing deposit generation is not performed for B and C (indicated as "conventional" in the figure)
When the same process is performed (described as "this embodiment" in the figure)
The flow rate decrease rate was measured. As can be seen from the experimental results of FIG. 13, the flow rate reduction rate is 1 by performing the fuel injection control in the present embodiment, although there are individual differences among the engines.
It was confirmed that it could be suppressed to / 3 to 1/10.

As described above, according to the fuel supply system of the present embodiment, the following effects can be obtained. (1) Conventionally, fuel injection has not been performed in an engine operating state in which the temperature of the catalyst 12 is higher than the NOx reduction upper limit temperature. However, in the present embodiment, fuel is injected even in the above operating state. In this case, heat of vaporization is taken from the injection nozzle 5 as the fuel vaporizes, so that the tip temperature of the injection nozzle 5 decreases. Further, the fuel is atomized by being injected, and the atomized fuel is vaporized, so that the ambient temperature near the tip of the injection nozzle 5 is lowered. In addition, the vaporized fuel forms a heat insulating layer in the vicinity of the tip of the injection nozzle 5 and suppresses direct exposure of the tip of the nozzle to hot exhaust gas. As described above, the tip temperature of the injection nozzle 5 can be lowered by intentionally injecting fuel even in the engine operating state in which the temperature of the catalyst 12 becomes higher than the NOx reduction upper limit temperature. As a result, it is possible to suppress the deterioration and solidification of the soot after the fuel adhering to the vicinity of the injection hole 28 to become a deposit,
It becomes possible to suppress a decrease in the flow rate of the injection nozzle. Further, since the fuel injected and supplied acts as a solvent for dissolving the rear drip soot adhering to the vicinity of the injection hole 28, it is possible to suppress the solidification of the rear drip soot, thereby suppressing a decrease in the flow rate of the injection nozzle 5. You will be able to.

(2) In the present embodiment, the accelerator opening ACCP and the engine rotational speed NE when the engine 1 is in the high-load and high-speed operating state and the fuel injection for providing the reducing action of the catalyst 12 is stopped. And are defined as predetermined values α1 and β1, respectively. Then, it is determined whether or not the read accelerator opening ACCP and engine speed NE are equal to or greater than predetermined values α1 and β1, respectively. Therefore, even in the operating state in which the fuel injection for providing the reducing action of the catalyst 12 is not performed, the operating state in which the fuel injection for suppressing the generation of deposit should be prioritized can be determined.

(3) In the present embodiment, the accelerator opening AC
The fuel injection period τ and the injection interval T are set based on the CP and the engine speed NE. At this time, the injection period τ is longer as the engine speed or the accelerator opening is increased,
Further, the injection interval T is set shorter as the engine speed or the accelerator opening increases. Therefore, as the operating condition of the engine 1 becomes higher under high load and higher rotation, in other words, as the exhaust gas temperature becomes higher, the injection period τ becomes longer, the injection interval T becomes shorter, and the amount of fuel injected from the injection nozzle 5 increases. To be done. Therefore, a suitable amount of fuel injection can be set according to the engine operating state.

(4) In the engine 1 described above, the tip of the injection nozzle 5 is installed in the exhaust port 6d of the fourth cylinder # 4. Therefore, the temperature of the tip of the injection nozzle 5 is the fourth cylinder #
It is highest when 4 is in the exhaust stroke. Therefore, in the present embodiment, the fuel injection start timing is set based on the exhaust timing of the fourth cylinder # 4. As a result, fuel can be injected when the tip temperature of the injection nozzle 5 becomes the highest, and the tip temperature can be appropriately reduced.

(5) In this embodiment, the injection nozzle 5 is attached to the cylinder head 2. Since the injection nozzle 5 only needs to be able to inject and supply fuel to the catalyst 12, it is upstream of the exhaust manifold 8 and the catalyst 12 (engine 1 side).
The exhaust passage 26 may be provided at any position. However, the exhaust manifold 8 and the exhaust passage 26 have a high temperature due to exhaust. On the other hand, the cylinder head 2 is normally cooled by cooling water, and the temperature of the cylinder head 2 is also low in the exhaust manifold 8 and the exhaust passage 26. Therefore, by attaching the injection nozzle 5 to the cylinder head 2,
It is possible to suppress an increase in the temperature of the main body, and thus it is possible to preferably suppress the generation of deposits due to the increase in the nozzle tip temperature.

(Second Embodiment) Since the engine 1 in the first embodiment intermittently exhausts the combustion gas, the pressure in the exhaust port changes from the combustion stroke to the exhaust stroke and the exhaust valve opens. A change occurs, and this pressure change causes a pressure pulsation in the exhaust manifold 8. Further, since the engine 1 is provided with the turbocharger 11, even when the exhaust gas collides with the exhaust side turbine of the turbocharger 11, the exhaust manifold 8 is provided.
Pressure pulsation occurs inside. Due to these pressure pulsations,
The following problems occur when the fuel is injected as described in the first embodiment when the exhaust flow in the direction opposite to the direction of the fuel injected from the injection nozzle 5 is formed in the exhaust port 6d. May occur.

As can be seen from the injection mode shown in FIG. 12 in the first embodiment, when the injection period τ is long, fuel is injected even after the exhaust stroke of the fourth cylinder # 4 is completed. FIG. 14 is an enlarged view of the vicinity of the tip of the injection nozzle 5 shown in FIG. Soot in the exhaust gas floats in the intake port 6d after the exhaust stroke is completed, as shown in FIG. When the mist-like fuel generated on the outer periphery of the fuel injection flow adheres to the soot in the floating state, the particle size increases. Then, when the soot having the increased particle size moves toward the tip of the injection nozzle 5 together with the exhaust flow generated by the pressure pulsation, a part of the soot adheres to the vicinity of the injection hole 28 of the injection nozzle 5. As described above, the adhesion of soot in the vicinity of the injection hole 28 causes a decrease in the flow rate of the injection nozzle 5.

Therefore, in the present embodiment, as in the first embodiment, the fuel injection for lowering the tip temperature of the injection nozzle 5 is performed, and the above problem is dealt with.
The fuel injection is temporarily stopped even during the injection period shown in FIG. The present embodiment is the same as the first embodiment except that this temporary suspension period is provided.

Hereinafter, a processing procedure when the fuel injection is temporarily stopped will be described with reference to FIG. In the engine 1 used in the experiments of FIGS. 3 to 8 by the present inventors, when the third cylinder # 3 is in the exhaust stroke,
It was confirmed that an exhaust flow toward the tip of the injection nozzle 5 as shown in FIG. 14 is generated in the exhaust port 6d of the cylinder # 4 due to the pressure pulsation.

Therefore, in the present embodiment, as shown in FIG. 15, fuel injection is started when the crankshaft rotates by a predetermined crank angle θA from the compression top dead center TDC of the fourth cylinder # 4, while When the crankshaft rotates from the compression top dead center TDC of the third cylinder # 3 by a predetermined crank angle θB, that is, when the third cylinder # 3 is in the exhaust stroke, fuel injection is temporarily stopped. Then, after this temporary injection stop, the injection mode in which fuel injection is started again when the crankshaft rotates by a predetermined crank angle θA from the compression top dead center TDC of the fourth cylinder # 4 is repeated, and the injection periods are divided. τk (τ in FIG. 15
The total sum of 1 to τ3) is set to the injection period τ set in step 120 of FIG. The predetermined crank angle θA has the same value as the predetermined crank angle θA described in the first embodiment. Further, the predetermined crank angle θB is in the exhaust stroke of the third cylinder # 3, and the exhaust port 6 of the # 4 cylinder is used.
The crank angle is set so as to catch the state immediately before the pressure pulsation starts to propagate in d. Further, since this timing changes depending on the engine rotation speed, the predetermined crank angle θB is variably set based on the engine rotation speed so as to decrease as the engine rotation speed increases.

As described above, according to the fuel supply system of the present embodiment, the following effects can be obtained. (1) When the exhaust flow in the direction opposite to the direction of the fuel injected from the injection nozzle 5 is formed in the exhaust port 6d due to the pressure pulsation, the fuel injection is temporarily stopped. Therefore, it is possible to suppress an increase in the particle size of soot in the exhaust gas due to the fuel injected from the injection nozzle 5, and it is possible to prevent soot from adhering to the vicinity of the injection hole 28. Further, since the adhesion of soot can be suppressed, it is possible to further suppress the decrease in the flow rate of the injection nozzle 5 as compared with the first embodiment.

(Other Embodiments) The above embodiment may be modified as follows, and even in that case, the operation and effect according to those embodiments can be obtained.

In each of the above embodiments, as shown in FIG. 16, in the graph showing the tendency of the exhaust temperature with respect to the accelerator opening and the engine speed, the exhaust temperature is NO.
In the operating region R1 where the temperature is lower than the x reduction upper limit temperature, fuel injection for NOx reduction is performed, while in the operating region R2 where the exhaust temperature is equal to or higher than the NOx reduction upper limit temperature, fuel injection for suppressing deposit formation is performed. There is. Here, when the operating state of the engine 1 is near the boundary between the operating regions R1 and R2 and the fuel injection interval is extremely long, the generation of deposits in the injection holes 28 is gradually advanced. Become. Therefore, even in the operating region R1, when the operating state of the engine 1 is near the boundary,
In addition to fuel injection for NOx reduction, fuel injection for suppressing deposit formation may be performed. In this case, for example, as shown in FIG. 17, a small amount of injection for suppressing deposit formation is intermittently performed during a period in which fuel injection for NOx reduction is not performed. The injection for suppressing the generation of the deposit may be performed as long as it is possible to scatter or dissolve the drip or soot adhering to the vicinity of the injection hole 28, and in consideration of suppressing the deterioration of fuel efficiency as much as possible. Is set to be shorter than the injection period for NOx reduction. With such a configuration, even when the injection suspension period of the fuel injected for NOx reduction becomes long, a small amount of fuel is injected during the injection suspension period, and the drool that adheres to the vicinity of the injection hole 28 is discharged. The soot is scattered or melted and is removed from the vicinity of the injection hole 28. Therefore, the rear-dribble soot is not exposed to the exhaust gas for a long time while being attached to the vicinity of the injection hole 28, and it is possible to suppress the deterioration of the rear-drip soot and the decrease in the flow rate of the injection nozzle 5 due to the solidification.

In each of the above embodiments, the fuel injection is started when the fourth cylinder # 4 rotates by the predetermined crank angle θA from the compression top dead center TDC. However,
This is because the tip of the injection nozzle 5 is installed in the exhaust port 6d of the fourth cylinder # 4, and when the tip of the injection nozzle 5 is installed in the exhaust port of another cylinder, it is installed. From the compression top dead center TDC of the cylinder to a predetermined crank angle θ
It may be set so that fuel injection is started when the crankshaft rotates by A.

In the above embodiments, the fourth cylinder # 4
The predetermined crank angle θA is set so that when the exhaust gas passes through the vicinity of the tip of the injection nozzle 5, a heat insulating layer due to fuel injection is already formed near the tip of the injection nozzle 5. On the other hand, the predetermined crank angle θA may be set so that the fuel is injected at the timing when the flow velocity of the exhaust gas passing near the tip of the injection nozzle 5 becomes the highest. In this case, the amount of exhaust gas passing through the tip of the injection nozzle 5 per unit time increases, so the amount of heat received by the injected fuel increases, and its vaporization is promoted.
Therefore, the tip temperature of the injection nozzle 5 can be efficiently lowered.

In the second embodiment, when the crankshaft rotates from the compression top dead center TDC of the third cylinder # 3 by the predetermined crank angle θB, that is, when the third cylinder # 3 is in the exhaust stroke, the Although the injection is paused, the point is that the injection of fuel may be paused when the exhaust flow in the direction opposite to the direction of the fuel injected from the injection nozzle 5 is caused by the pressure pulsation. Further, instead of stopping the injection in this way, the injection amount may be appropriately reduced. For example, in this case, the fuel is intermittently injected, and the injection amount is reduced during the period in which the third cylinder # 3 is in the exhaust stroke, compared to the other periods.

In each of the above-described embodiments, the exhaust temperature, and hence the temperature of the catalyst 12, is estimated from the engine load, and this engine load is detected by the accelerator opening. Here, when the engine load increases, the following tendencies are observed in the following parameters indicating the engine operating state.

The opening of the throttle valve 16 increases, the opening of the EGR valve 15 decreases, the oxygen concentration in the exhaust decreases, the NOx concentration in the exhaust increases, the THC in the exhaust Concentration (total concentration of HC with different molecular weight)
The exhaust pressure in the exhaust passage increases. Therefore, the exhaust temperature can be estimated using at least one of the parameters indicating the operating state and the engine rotation speed.

Since the fuel injection amount injected into the intake passage and the cylinder has a correlation with the engine heat generated in the cylinder, the exhaust temperature can be estimated based on the fuel injection amount. .

Further, an exhaust gas temperature sensor may be installed in the exhaust manifold 8 or the exhaust passage 26 to directly measure the exhaust gas temperature. -In each above-mentioned embodiment, although injection nozzle 5 is attached to cylinder head 2, if it is an upstream side of catalyst 12, the attachment position will be arbitrary.

The internal combustion engine in each of the above embodiments was a diesel engine. However, each of the above-described embodiments can be applied to a gasoline engine that injects fuel into the exhaust gas, and in this case as well, effects similar to those of each of the above-described embodiments can be obtained.

The fuel supply device for the exhaust catalyst in each of the above-described embodiments is premised on that fuel is injected as a reducing agent when the catalyst 12 is in the activation temperature region where the catalyst 12 is activated. In addition, the fuel injection from the injection nozzle 5 is executed even when the catalyst 12 is in a high temperature region higher than the activation temperature region. On the other hand, for example, when the temperature of the catalyst 12 is in a low temperature region lower than the self-ignition temperature of the soot adhering to the catalyst 12, it is premised that fuel injection is performed to promote self-ignition of the soot. In the fuel supply device for the exhaust catalyst, the fuel injection from the injection nozzle 5 may be executed when the catalyst 12 is in a high temperature region higher than the low temperature region in addition to the low temperature region. That is, in FIG. 3, when the NOx reduction upper limit temperature is replaced with the soot self-ignition temperature,
In the shaded region, that is, in the low load and low rotation region, fuel injection is performed to promote soot self-ignition. On the other hand, in the other region, that is, in the high load and high rotation region, fuel injection may be performed to suppress the generation of deposits at the tip portion of the injection nozzle 5.

The fact that the catalyst 12 is in the high temperature range in the exhaust catalyst fuel supply device can be estimated based on the accelerator opening and the engine rotation speed, as in the first embodiment. it can. In addition, the structure shown in each of the above-described modifications can be adopted also in the fuel supply device for the exhaust catalyst.

Further, in this exhaust catalyst fuel supply device, the soot accumulation amount of the catalyst 12 is estimated based on the engine operating condition and the like, and the condition is that the estimated soot accumulation amount is not less than a predetermined amount. First, fuel injection may be performed in the low temperature region.

When the amount of accumulated soot on the catalyst 12 increases, the pressure loss when the exhaust gas passes through the catalyst 12 increases, and the differential pressure of the exhaust pressure before and after the catalyst 12 increases. Therefore, a pressure sensor is provided in front of and behind the catalyst 12 in the exhaust passage 26, and when the difference in exhaust pressure detected by the pressure sensor exceeds a predetermined value, it is estimated that the soot accumulation amount is equal to or more than a predetermined amount. May be.

If the fuel in each of the above-described embodiments and modifications is a fuel for an internal combustion engine that exhibits at least one of an exhaust purification action of a catalyst and an action of promoting self-ignition of soot, It can be anything. Also in this case, it is possible to obtain the effects similar to those of the above-described embodiments and modifications.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a diesel engine and a fuel supply device for an exhaust catalyst applied to the diesel engine.

FIG. 2 is a sectional view of an exhaust port to which an injection nozzle is attached.

FIG. 3 is an explanatory diagram showing a tendency of an exhaust temperature with respect to an engine speed and an output torque (load), and a region where fuel injection for NOx reduction is performed.

FIG. 4 is a graph showing the relationship between the exhaust temperature and the tip temperature of the injection nozzle 5.

FIG. 5 is a graph showing the relationship between nozzle tip temperature and flow rate decrease rate.

FIG. 6 is an explanatory diagram showing a relationship between an engine operation pattern and a flow rate decrease rate.

FIG. 7 is an explanatory diagram showing a tip temperature of the injection nozzle 5 and a fuel injection mode in an operation state of patterns LH.

FIG. 8 is an explanatory diagram showing a tendency of soot generation with respect to engine rotation speed and output torque (load).

FIG. 9 is a flowchart showing a high temperature region injection control process of the exhaust catalyst fuel supply device according to the present embodiment.

FIG. 10 shows an injection period τ and an injection interval T in this embodiment.
A calculation map for obtaining.

FIG. 11 is an explanatory diagram showing a mode of fuel injection and suspension by high temperature region injection control processing.

FIG. 12 is an explanatory diagram showing a fuel injection mode in the first embodiment.

FIG. 13 is a graph showing suppression of reduction in flow rate according to the first embodiment.

FIG. 14 is a schematic view showing a mode in which soot is attached to the tip of the injection nozzle.

FIG. 15 is an explanatory diagram showing a fuel injection mode in the second embodiment.

FIG. 16 is a conceptual diagram showing an operating region for injecting fuel for NOx reduction and an operating region for injecting fuel for suppressing deposit generation.

FIG. 17 is an explanatory diagram showing a fuel injection mode in another embodiment.

[Explanation of symbols]

1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4
a-4d ... Fuel injection valve, 5 ... Injection nozzle, 6a-6d ...
Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, 10 ... Supply pump, 11 ... Turbocharger, 12 ... Catalyst, 13
... EGR passage, 14 ... EGR cooler, 15 ... EGR valve,
16 ... Throttle valve, 17 ... Actuator, 18 ... Intercooler, 19 ... Air flow meter, 20 ... Throttle opening sensor, 21 ... Air-fuel ratio sensor, 22 ... Cylinder discrimination sensor, 23 ... Crank angle sensor, 24 ... Accelerator opening sensor , 25 ... Electronic control unit (ECU), 26 ... Exhaust passage, 27 ... Fuel supply pipe, 28 ... Injection hole, 29 ... Exhaust temperature sensor, # 1 ... First cylinder, # 2 ... Second cylinder, # 3 ... Three
Cylinder # 4 ... the fourth cylinder.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Morio Narita             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F term (reference) 3G084 AA01 BA24 DA10 DA14 DA19                       EC02 EC03 FA10 FA28 FA29                       FA33 FA37                 3G091 AA02 AA10 AA11 AA18 AB06                       BA07 BA14 CA18 CB03 DA01                       DA08 DC05 EA01 EA05 EA07                       EA17 EA32 EA33 EA34 FB02                       FB03 HA04

Claims (10)

[Claims] 1. An injection nozzle provided in an exhaust system of an internal combustion engine for injecting fuel to a catalyst, the injection nozzle supplying the fuel when the catalyst is in an activation temperature region where the catalyst is activated. In the fuel supply device for the exhaust catalyst, the injection control means for performing the injection supply of the fuel by the injection nozzle when the catalyst is in a high temperature region higher than the activation temperature region is provided. Exhaust catalyst fuel supply device. 2. An injection nozzle provided in an exhaust system of an internal combustion engine for injecting fuel to a catalyst, wherein the temperature of the catalyst is in a low temperature region lower than an autoignition temperature of soot adhering to the catalyst. In a fuel supply device for an exhaust catalyst that executes fuel injection and supply by the injection nozzle, injection control that executes injection and supply of the fuel by the injection nozzle when the catalyst is in a high temperature region higher than the low temperature region. A fuel supply device for an exhaust gas catalyst, comprising: 3. The fuel supply device for an exhaust catalyst according to claim 1, wherein the injection control means determines that the catalyst is in the high temperature region based on an engine operating state. 4. An engine is provided with an injection nozzle provided in an exhaust system of an internal combustion engine for injecting fuel to a catalyst, and injecting fuel by the injection nozzle when the catalyst is in an activation temperature region where the catalyst is activated. In an exhaust catalyst fuel supply device that intermittently executes with an injection period and an injection interval set based on an operating state, a fuel is supplied in an injection period shorter than the set injection period during the set injection interval. A fuel supply device for an exhaust catalyst, comprising: an injection control unit that executes the injection supply of 5. An injection nozzle provided in an exhaust system of an internal combustion engine for injecting fuel to a catalyst, wherein the temperature of the catalyst is in a low temperature region lower than an autoignition temperature of soot adhering to the catalyst. In an exhaust system fuel supply device for intermittently performing fuel injection supply by the injection nozzle with an injection period and an injection interval set based on an engine operating state, the injection period set during the set injection interval A fuel supply device for an exhaust catalyst, comprising an injection control means for performing fuel injection supply in a shorter injection period. 6. An accelerator opening degree as the engine operating state,
At least one of the throttle opening, the EGR valve opening, the oxygen concentration in the exhaust gas, the NOx concentration in the exhaust gas, the THC concentration in the exhaust gas, the pressure in the exhaust passage, and the engine speed are detected. A fuel supply device for the exhaust gas catalyst according to claim 1. 7. The fuel supply device for an exhaust gas catalyst according to claim 3, wherein an exhaust gas temperature is detected as the engine operating state. 8. The fuel supply device for an exhaust catalyst according to claim 3, wherein a fuel injection amount is detected as the engine operating state. 9. The injection control means supplies injection of fuel by the injection nozzle when an exhaust flow in a direction opposite to the direction of the fuel injected from the injection nozzle is formed in the exhaust system by pressure pulsation of exhaust gas. 9. The method for suspending
7. A fuel supply device for an exhaust catalyst according to any one of 1. 10. The injection nozzle is provided in an exhaust system corresponding to a specific cylinder of the internal combustion engine, and the injection control means sets an injection supply timing of the fuel based on an exhaust timing of the specific cylinder. Item 10. An exhaust catalyst fuel supply device according to any one of items 1 to 9.