JPH0617655A - Exhaust gas purifying device of diesel engine - Google Patents

Abstract

PURPOSE:To decrease a quantity of soot in exhaust gas by cooling intake air by means of cooling cycle, and also controlling to enhance intake air cooling capacity temporarily when delay of intake air supply in response to an increase in a fuel supply quantity is detected. CONSTITUTION:A turbosupercharger 8, an intercooler 12 and an evaporator 13 for cooling intake air are arranged in the intake passage 7 of an engine body 1. Coolant of a cooling device 14 provided with a coolant control valve 19, etc., is circulated through the evaporator 13, and then a coolant control valve 23 is interposed therebetween. Respective coolant control valves 19, 23 are controlled based on various detection signals from various sensors 26-29 by a control unit U, respectively, and then intake air cooling capacity by means of the evaporator 13 is varied. At the time, delay of supplying the intake air in response to an increase in a fuel supply quantity by a fuel injection valve 4 is detected. At the time of this detection, the intake air cooling capacity is controlled to be temporarily increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for a diesel engine.

[0002]

2. Description of the Related Art Many engines, especially engines with a supercharger, are provided with cooling means for cooling intake air. As this cooling means, there is one utilizing a refrigeration cycle provided with a compressor mechanically driven by an engine (Japanese Patent Laid-Open No. 61-65014, Japanese Patent Laid-Open No. 61-65014).
-126319, JP-A-61-53423). Cooling of the intake air using such a refrigeration cycle is mainly performed from the viewpoint of improving the charging efficiency and preventing knocking.

[0003]

By the way, recently,
Exhaust gas purification in a diesel engine has become a problem, and how to reduce soot (particulates) has become a major problem. This soot becomes a particular problem when the supply of intake air is delayed with respect to an increase in the amount of fuel supplied to the combustion chamber, such as when the engine is accelerated, that is, when the excess air ratio is temporarily reduced.

Therefore, it is an object of the present invention to provide an exhaust gas purifying apparatus for a diesel engine which can reduce soot in the exhaust gas.

[0005]

In order to achieve the above object, the present invention has the following configuration. That is, the intake air cooling means for circulating the refrigerant to forcibly cool the intake air, the cooling capacity adjusting means for adjusting the cooling capacity of the intake cooling means, and the intake air for increasing the fuel supply amount to the combustion chamber. A delay detecting means for detecting a supply delay, and a cooling capacity control for controlling the cooling capacity adjusting means when the supply delay of the intake air is detected by the delay detecting means to temporarily increase the cooling capacity of the cooling means. Means and are provided.

The delay detecting means may detect when the engine is accelerating, for example, when the engine is accelerating based on an increase change in the accelerator opening. In this case, the cooling capacity of the cooling means can be increased for a predetermined period of time after the increase change in the accelerator opening is detected.

When the cooling means is operated at least in the high load area and the delay of the intake air is detected by the delay detecting means in the high load area,
The cooling capacity of the operated cooling means can be increased.

The cooling means may be a refrigeration cycle equipped with a compressor mechanically driven by an engine. In this case, the cooling capacity adjusting means can be configured by a variable rotation ratio transmission mechanism interposed between the engine and the compressor. That is,
The cooling capacity of the cooling means can be increased by increasing the ratio of the compressor rotation speed to the engine rotation speed. In this case, further comprising deceleration detection means for detecting deceleration of the engine, and when deceleration of the engine is detected, the rotation ratio of the transmission mechanism may be changed to a state in which the cooling capacity of the cooling means increases. it can.

The fuel injection pump for pumping the fuel to the combustion chamber may have an all speed governor characteristic.

[0010]

According to the present invention, when the intake air amount is smaller than the increased fuel amount and the air surplus ratio is reduced, the intake air temperature is increased by increasing the cooling capacity of the cooling means. By further reducing it, soot in the exhaust gas can be significantly reduced. That is, the soot can be significantly reduced as a whole by the soot reduction due to the ignition delay due to the decrease in the temperature of the intake air and the soot reduction due to the acceleration of the oxidizing action due to the increase of the air surplus ratio, that is, the oxygen concentration.

By adopting the structure described in claim 2, it is possible to reduce the soot at the time of acceleration by temporarily stopping the temporary decrease of the air surplus ratio at the time of acceleration.

With the structure as described in claim 3, while the acceleration is easily detected by the general method of increasing the accelerator opening, the air surplus ratio is temporarily reduced to increase the soot. The soot during acceleration can be reduced by a simple method as a whole by setting the period to be performed as a predetermined time from the increase change in the accelerator opening.

With the structure as described in claim 4, it is possible to reduce soot while reducing NOx which is a problem at the time of high load.

With the structure as described in claim 5, the cooling capacity of the cooling means can be made extremely large to effectively reduce the soot when necessary, and the cooling capacity can be unnecessarily increased in the normal state. It is preferable for improving fuel efficiency.

With the structure as described in claim 6, it is preferable for increasing the absolute cooling capacity of the refrigeration cycle and sufficiently lowering the intake air temperature for reducing the soot.

With the configuration as described in claim 7, the refrigerating capacity of the refrigerating cycle is set in advance in preparation for the next acceleration expected after deceleration, that is, at the time of acceleration in which the air surplus ratio decreases and soot becomes a problem. By raising it,
During this acceleration, the intake air temperature can be promptly lowered to effectively reduce the soot.

With the structure as described in claim 8, even if the accelerator is slightly depressed, the maximum fuel injection amount is once obtained, that is, the intake air supply delay is apt to occur frequently. It is effective in reducing soot in a diesel engine having an injection pump.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a diesel engine main body,
The engine body 1 is an in-line four-cylinder engine in which four cylinders 2 are arranged in series, and its crankshaft is indicated by reference numeral 3.

Each cylinder 2 is provided with an electronically controlled fuel injection nozzle 4 as a fuel supply means. Each of the fuel injection nozzles 4 is connected to an electronically controlled fuel injection pump 5, and a driving force is applied to the fuel injection pump 5 by the crankshaft 3. Of course, the fuel injection pressure of each fuel injection nozzle 4 (hereinafter referred to as the injection pressure) is to be adjusted by the fuel injection pump 5. The injection pressure of the fuel injection pump 5 is 3 per square cm.
The pressure is as high as 00 to 1500 kg.

In the embodiment, the fuel injection pump 5 has an all speed governor characteristic as shown in FIG. That is, for example, when the accelerator is slightly stepped on from the idle state as shown by the point A, the fuel injection amount once reaches the maximum fuel injection amount, and then the fuel injection amount corresponding to the accelerator opening at the point A It has the following characteristics.

As is known, an exhaust passage 6 and an intake passage 7 are connected to each cylinder 2, respectively. A turbine wheel 8 a of a turbocharger 8 is arranged in the exhaust passage 6. On the other hand, the compressor wheel 8b of the turbocharger 8 is arranged in the intake passage 7, and therefore,
When the turbine wheel 8 is rotated by the exhaust energy, the compressor wheel 8b is also rotated via the shaft 8c, so that supercharging (turbo supercharging) is performed.

Further, the exhaust passage 6 is provided with a relief passage 9 that bypasses the turbine wheel 8a. The waist gate valve 1 is provided in the relief passage 9.
0 is provided for this waist gate valve 10
The drive actuator 11 adjusts its opening.

In the intake passage 7, the compressor wheel is provided.
An air-cooling type intercooler 12 and an intake-air cooling evaporator 13 are arranged in this order from the rule 8b toward the downstream side.
The refrigerant of the vehicle interior air cooling refrigeration system 14 is circulated in the evaporator 13. That is, the refrigerating device 14
As is known, the compressor 15, the condenser 16, the refrigerant storage tank 17, the expansion valve 18, the vehicle interior refrigerant control valve 19,
The vehicle interior evaporator 20 is provided. The compressor 15 is driven by the crankshaft 3 via a variable pulley 21, an electromagnetic clutch 22 and the like.

By changing the pulley ratio of the variable pulley 21, the compressor 15 with respect to the engine speed is changed.
The ratio of the rotational speeds of the compressors can be changed, and as the pulley ratio, that is, the rotational ratio increases (the rotational speed of the compressor 15 increases), the output energy of the compressor 15 increases and the refrigerating capacity of the refrigerating apparatus 14 increases. Is increased.

The evaporator 20 is provided in the refrigerating device 14.
Further, the evaporator 13 is attached so as to bypass the control valve 19, and an intake air cooling refrigerant control valve 23 is interposed between the evaporator 13 and the refrigerating device 14. The intake control valve 23 and the vehicle compartment control valve 1
The intake air cooling capacity of the evaporator 13 can also be changed by changing the opening ratio with respect to 9.

The bottom of the evaporator 13 and the evaporator
The intake passage 7 downstream of the engine 13 is connected to the intake passage 7 by a passage 24 that is sufficiently thinner than the intake passage 7, and a control valve 24, which is an on-off valve, is connected to the passage 24. This allows
When the control valve 24 is opened during engine operation, the evaporator 1
The dew condensation water accumulated at the bottom of 3 is sucked into the intake passage 7 through the passage 24 by the Venturi effect.

Reference numeral U in FIG. 1 is a control unit composed of, for example, a microcomputer, and the control unit U is, as is known, a CPU, a ROM, a RAM, and a CLO.
It has CK and so on. Various signals from the sensors 26 to 30 are input to the control unit U. The sensor 26 detects the amount of depression of the accelerator pedal 29, that is, the accelerator opening that is the engine load. The sensor 27 detects the engine cooling water temperature. The sensor 28 detects the engine speed. The sensor 29 detects the vehicle interior temperature. The sensor 30 detects the atmospheric temperature. On the other hand, from the control unit U, the fuel injection nozzles 4, the fuel injection pump 5, the drive actuator 11, the variable pulley 21,
A control signal is output to the control valves 19, 23 and 25.

Next, the control contents of the control unit U will be described. Basically, as shown in Table 1 below, intake air cooling (5 types in the embodiment) is performed in accordance with the operating state of the engine (5 types in the embodiment). O of the cooling action by the evaporator 13)
N, OFF, fuel injection timing, fuel injection pressure, and maximum boost pressure are set and changed. Among these, the priority order of control is, in order from higher priority to lower priority, during warm-up (when cold), during low temperature, during acceleration, at high altitude, and during normal operation. However, during acceleration during which the control according to the present invention is performed, special control is performed as described later. In addition, the cooling action by the evaporator 13 is turned on and off.
The FF is performed by opening and closing the intake cooling control valve 23, but it is premised that the compressor 15 is driven when the cooling action of the evaporator 13 is ON.

[0029]

[Table 1]

Next, of the control contents of the control unit U, the portion relating to the present invention is shown in the flow chart of FIG.
An explanation will be given with reference to the chart. In the following description, it is assumed that the compressor 15 is driven, the intake cooling control valve 23 is opened, and the intake air is cooled by the evaporator 13. In such a state, at least the engine high load is applied. Done in time. First, S
After the signal from the sensor is input in step 1, in step S2, the pulley ratio (basic pulley ratio) PR of the variable pulley 21 is set.
A is determined according to the atmospheric temperature as shown in FIG.

At S3, it is judged if the temperature inside the vehicle is higher than a predetermined temperature. YE in this S3 determination
In the case of S, in S4, the pull ratio PRA determined in S2 is multiplied by a predetermined increase correction coefficient α (α> 1) to obtain a large pull ratio, that is, the cooling capacity of the refrigerating device 14. Is corrected to a value in the increasing direction. This S4
After that, the process proceeds to S5, but if the determination in S3 is NO,
The process proceeds to S5 without passing through S4.

At S5, it is judged if the vehicle is accelerating. Whether or not the vehicle is accelerating is determined by checking whether or not the amount of increase in the accelerator opening per predetermined time period, that is, the rate of change in the increasing direction of the accelerator opening is equal to or greater than a predetermined value. If YES in the determination in S5, S
6, the control valve 23 for cooling the intake air is fully opened, and then S
At 7, it is determined whether or not it is during rapid acceleration. This determination is made based on the rate of change in the increasing direction of the accelerator opening similarly to the determination in S5, and the determination threshold value at that time is set to be larger than the determination threshold value at S5. .

When the determination in S7 is YES, in S8, the vehicle compartment cooling control valve 19 is closed to cut the vehicle compartment cooling, and the process proceeds to S9. When the determination in S7 is NO, the process proceeds to S9 without passing through S8.
In this S9, it is determined whether or not the flag is 1. When this flag is 1, it indicates that the cooling capacity of the refrigeration system 14 is being increased during deceleration, and the flag is initially 0. Since it has been initialized to S9
The determination is NO.

After S9, in S10, the pull ratio PRA determined in S2 or S4 is multiplied by a predetermined increase correction coefficient β (β>α> 1), so that the intake air by the evaporator 13 is increased. The Pulley ratio is corrected to a value in which the cooling capacity is further increased.

After S10, in S11, the signal corresponding to the pull ratio PRA determined as described above is
It is output to the variable pulley 21 (realization of the determined pulley ratio PRA). Thereafter, in S12, it is determined whether or not a predetermined time has elapsed since the acceleration was detected in S5. This S1
If the determination in No. 2 is NO, the process returns to S11, and the increase state of the intake cooling capacity by the evaporator 13 is continued. When the determination in S12 is YES, the flag is reset to 0 in S13, and in S14, the openings of the control valves 19 and 23 are gradually returned to the openings during normal operation.

When the determination in S5 is NO, it is determined in S15 whether the flag is 1. Initially, the determination in S15 is NO and the process proceeds to S16. In S16, it is determined whether or not the vehicle is decelerating. The determination as to whether or not the deceleration is made is performed, for example, by checking whether or not the accelerator opening is zero and the engine speed is equal to or higher than a predetermined speed.

If the determination in S16 is YES, the flag is set to 1 in S17, and then in S18.
The pull ratio PRA determined in S2 or S4 is multiplied by a predetermined increase correction coefficient β (same as S10), and S19
This increased pull ratio PRA is realized at.
After S19, it is determined in S20 whether or not a predetermined time has elapsed since the deceleration detection in S16.
If the determination is NO, the process returns to S5.

The S5 at the time of shifting from S20 to S5
If the determination is NO, the determination in S15 is YES,
At this time, the process proceeds to S19 without passing through S116 to S18, and the actual pulley ratio of the variable pulley 31 continues to be held at the pulley ratio PRA corrected by the increase correction coefficient β.

When the determination in S5 is YES after the determination in S20 is NO, the determination in S9 is YES, and in this case, the pull ratio PRA is already increased and corrected for acceleration in S9. Therefore, at this time, the process proceeds to S11 without passing through S10.

When the determination in S20 is YES, the acceleration is not detected within the predetermined time in S20 after the deceleration is detected. At this time, the process proceeds to S13 described above,
The acceleration / deceleration control is switched to the normal operation state control. Of course, when the determination in S16 is NO, it is not related to the acceleration / deceleration control, and in this case, the pull ratio PRA determined in S2 or S4 is realized in S21.

Of the above-mentioned control contents, what is focused on during acceleration and during deceleration is shown in FIG. 4 as a time chart. In FIG. 4, t1 is when deceleration is detected, and t1
2 is the acceleration detection time that is performed within a predetermined time (corresponding to S20 in FIG. 6) from the deceleration detection, and t3 is the time when a predetermined time (corresponding to S12 in FIG. 6) has elapsed from the acceleration detection time. After t3, the control valves 19, 23 are operated by the time T4.
Although the opening of each of the control valves is gradually returned to the normal state before acceleration / deceleration control (corresponding to S14 of FIG. 4), the control valve 19 or 23 may be returned to the normal opening state all at once. Good.

As shown by t2 to t3 in FIG. 4, the intake cooling capacity by the evaporator 13 is maintained for a predetermined time from the time when the acceleration is detected, that is, a time corresponding to the period when the air surplus ratio decreases and the soot increases. Is increased, soot can be reduced in the exhaust gas during this acceleration. In particular, when the load is high, NOx in the exhaust gas is also a problem,
NOx is also reduced due to the increase in intake air cooling. FIG. 5 shows the effect of reducing soot and NOx at the time of rapid acceleration under the high load condition.

When deceleration is detected, the
Since the cooling ratio of the refrigeration system 14 is increased and the cooling capacity of the refrigeration system 14 is increased, the intake air is quickly cooled sufficiently by the evaporator 13 during acceleration, which is often performed after deceleration. By doing so, soot can be sufficiently reduced from the initial stage of acceleration.

While the cooling capacity of the refrigerating apparatus 14 is adjusted in response to the vehicle compartment cooling request by the processing of S3 and S4 in FIG.
By the process of 8, the entire cooling capacity of the refrigeration system 14 is used for cooling the intake air at the time of sudden acceleration, and soot at the time of sudden acceleration is sufficiently reduced.

During deceleration, as shown by the broken line in FIG.
Controlling at least one of fully opening the vehicle interior control valve 19 and fully closing the intake air control valve 23 is preferable for sufficiently cooling the vehicle interior.

FIG. 7 shows another embodiment of the present invention. In this embodiment, the pump 41 is connected to the passage 24 for dew condensation water, and the injection nozzle 42 is connected to the tip of the passage 24 so that the control unit U controls the valve opening timing and opening degree of the injection nozzle 42. It is the one. That is, the dew condensation water accumulated at the bottom of the evaporator 13 can be supplied from the intake passage 7 to the combustion chamber by opening the injection nozzle 42 at the time of the above-described acceleration, particularly at the time of acceleration under a high load condition. Is further preferable to reduce soot and reduce soot. Further, the dew condensation water may be constantly supplied to the intake passage 7 little by little with the opening of the injection nozzle 42 reduced, and the injection nozzle 42 may be fully opened at the time of acceleration detection. Of course, the use of the injection nozzle 42 is also preferable in that the condensed water is supplied to the intake passage 7 in the state of being atomized to reduce the temperature of the intake air. Further, as shown in FIG. 8, the engine rotation speed and the engine load may be used as parameters, and the condensed water may be injected from the injection nozzle 42 only in the operating region where the NOx is large. In this case, the NOx is large. It is also possible to increase the injection amount under different operating conditions.

[Brief description of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an oil speed governor characteristic of a fuel injection pump.

FIG. 3 is a diagram showing a basic setting example of a pull ratio.

FIG. 4 is a time chart showing a control example of the present invention.

FIG. 5 is a diagram schematically showing the effect of the present invention.

FIG. 6 is a flow chart showing a control example of the present invention.

FIG. 7 is a main part system diagram showing another embodiment of the present invention.

8 is a diagram showing a preferable injection area and an injection amount of condensed water in the embodiment shown in FIG.

[Explanation of symbols]

 1: Engine body 4: Fuel injection nozzle 5: Fuel injection pump 7: Intake passage 13: Evaporator (for intake air cooling) 14: Refrigeration device 19: Refrigerant control valve (for vehicle compartment cooling) 23: Refrigerant control valve (intake air (For cooling) 21: Variable pulley 26: Sensor (accelerator opening) 28: Sensor (engine speed) U: Control unit U

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masatsugu Sakimoto, No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Mitsunori Kondo No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Stock In-house (72) Inventor Keiji Araki 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Corporation

Claims (8)

[Claims] 1. An intake air cooling means for circulating a refrigerant to forcibly cool intake air, a cooling capacity adjusting means for adjusting a cooling capacity of the intake cooling means, and an increase in a fuel supply amount to a combustion chamber. Delay detection means for detecting a supply delay of intake air; and when the delay detection means detects a supply delay of intake air, the cooling capacity adjusting means is controlled to temporarily increase the cooling capacity of the cooling means. An exhaust gas purifying apparatus for a diesel engine, comprising: a cooling capacity control means. 2. The method according to claim 1, wherein the delay detecting means detects that the engine is being accelerated. 3. The delay detection means according to claim 2, wherein the delay detection means detects that the engine is accelerating based on an increase change in the accelerator opening, and the cooling capacity control means causes the delay detection means to open the accelerator. The cooling capacity of the cooling means is increased for a predetermined time period from the time when the increase in the temperature is detected. 4. The cooling means according to claim 1, wherein the cooling means is operated at least in a high load area, and when the delay detection means detects a supply delay of intake air in the high load area, the operation is performed. The cooling capacity of the cooling means is increased. 5. The refrigerating cycle according to claim 1, wherein the cooling means includes a compressor mechanically driven by an engine. 6. The cooling capacity adjusting means according to claim 5, comprising a variable rotation ratio transmission mechanism interposed between the engine and the compressor to increase the ratio of the compressor rotation speed to the engine rotation speed. As a result, the cooling capacity of the cooling means is increased. 7. The deceleration detecting means for detecting deceleration of the engine according to claim 6, further comprising: when the deceleration of the engine is detected by the deceleration detecting means, the rotation ratio of the transmission mechanism is the cooling of the cooling means. It is changed to a state in which the ability increases. 8. The fuel injection pump according to claim 1, wherein the fuel injection pump for pumping the fuel into the combustion chamber is an open source.
Luspid governor having characteristics.