JP2005282535A - Operating device for engine exhaust throttle valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time required for recovery while reducing noise generated at a time of recovery to full open position after retaining an exhaust throttle valve installed in an exhaust system of the engine and operated by a fluid pressure actuator at a closed position. <P>SOLUTION: The exhaust system of a diesel engine is equipped with a diesel particulate filter 81 and a catalyst 82 in an upstream thereof, and the exhaust throttle valve 9 actuated by a fluid pressure actuator 92 is installed in a downstream thereof. A passage communicating to the fluid pressure actuator 92 is provided with an orifice 94 and a capacity chamber 95. If the diesel particulate filter 81 is regenerated under a condition that opening of the exhaust throttle valve 9 is kept small, release speed of the exhaust throttle valve 9 is reduced by the orifice 92 and generated noise is reduced at a time of release of the exhaust throttle valve 9. Also time required for release is shortened by the capacity chamber 95. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a fluid pressure actuator that operates an exhaust throttle valve installed in an exhaust system of an engine, for example, an exhaust throttle valve installed downstream of an exhaust gas aftertreatment device of a diesel engine.

As an important part of environmental measures, regulations for nitrogen oxides (NOx) or hydrocarbons (HC), which are considered harmful components in exhaust gas, are implemented for vehicle engines, while reducing harmful components Various technologies are being developed vigorously. In particular, regulations on diesel engines, particularly diesel engine exhaust gas, have been gradually strengthened in recent years, and there is a tendency that more stringent regulations will be implemented in the future. A diesel engine is an engine that compresses air supplied into a cylinder and injects fuel into air that has become high temperature and pressure and burns it, and generally has higher thermal efficiency than a gasoline engine. Therefore, although the emission amount of carbon dioxide (CO ₂ ) has a characteristic of being reduced by that amount, reduction of particulate matter (particulate: PM) and NOx is strongly demanded.

  In PM, carbon and unburned components of fuel are discharged as fine particles due to incomplete combustion of fuel injected into a cylinder. In a diesel engine, the amount of PM generated increases depending on the operating state due to poor mixing of injected fuel and air. In particular, for the purpose of reducing NOx, when performing so-called EGR, which is mixed with air in a diesel engine cylinder and recirculates exhaust gas, the amount of air supplied into the cylinder is reduced or the maximum combustion temperature Since the amount of generated PM tends to increase due to the decrease in PM, the reduction of PM and the reduction of NOx are contradictory.

In order to prevent the emission of PM, there is a technique of attaching a filter called a diesel particulate filter (DPF) to the exhaust system of a diesel engine and capturing the PM by this DPF. The DPF is usually a ceramic body such as porous cordierite that is provided with a large number of thin passages partitioned in a lattice pattern in the axial direction, and the entrances and exits of adjacent passages are alternately sealed. The exhaust gas of the diesel engine flows downstream through the porous ceramic wall between adjacent passages, and at this time, particulate PM is collected. Some use a fine non-woven fabric made of heat-resistant fibers such as ceramic fibers instead of using a porous ceramic body. In addition, in order to prevent the emission of PM, a technique for mounting an oxidation catalyst device in which a catalyst made of a noble metal such as platinum, palladium or rhodium is coated on the surface of a large number of passages formed in a ceramic carrier is also known. Yes. When the exhaust gas flows through the passage of the oxidation catalyst device, the catalytic action causes PM in the exhaust gas to react with oxygen in the exhaust gas of the diesel engine and be oxidized to be converted to CO ₂ or the like. In some cases, such a catalyst is supported on the surface of the DPF.

  By the way, in the DPF equipped in a vehicle equipped with a diesel engine, PM captured by the repeated operation of the engine accumulates. When a large amount of PM accumulates, the filter becomes clogged and the back pressure of the engine increases, or the accumulated PM burns at a time when the engine exhaust temperature becomes high and heats up to the DPF. There are harmful effects such as damage. In order to prevent such an adverse effect, it is necessary to regenerate the DPF, in which the accumulated PM is removed as appropriate to restore the DPF function. As will be described later, the operating device of the present invention can also be applied to an exhaust throttle valve installed for use during regeneration of a DPF.

  As a regeneration means, a system in which PM is burned by heating with an electric heater or a burner is known. However, when this PM combustion method is adopted, the DPF becomes complicated and expensive due to the combination of an electric heater and the like with the DPF, and at the same time, PM cannot be collected during re-combustion. There arises a problem that the apparatus becomes large in size because a system in which a plurality of DPFs are arranged in parallel in the passage to alternately collect and burn. Based on this problem, in recent years, an oxidation catalyst is installed upstream of the DPF exhaust gas to oxidize unburned components in the exhaust gas and raise its temperature. A method of regenerating DPF by continuously oxidizing and removing during operation is drawing attention. In addition, a method of coating the surface of the DPF instead of installing the catalyst upstream, for example, using a so-called NOx storage reduction catalyst on the upstream surface of the DPF, and utilizing active oxygen generated when NOx is stored and reduced A method of continuously oxidizing and removing the collected PM is also conceivable. A DPF having a catalyst provided upstream of the DPF and continuously removing and regenerating the collected PM is hereinafter referred to as a continuous regeneration DPF.

  Since the continuous regeneration type DPF removes PM by the action of the catalyst provided upstream thereof, the catalyst does not perform sufficiently below the activation temperature of the catalyst, as in a normal catalyst device, and continuously. Playback is not performed. A temperature of about 350 ° C. is necessary as a temperature at which the catalyst is activated and good regeneration is performed, but the exhaust gas temperature is considerably lowered at a low load when the fuel injection amount of the diesel engine is small, and this operation state is maintained for a long time. If continued, the temperature of the catalyst will be below the activation temperature. For this reason, PM is accumulated in the DPF, which causes the DPF to be damaged due to combustion of a large amount of PM when the back pressure of the engine increases or the exhaust gas temperature rises. Therefore, even in a continuous regeneration type DPF, when a certain amount of PM accumulates in the DPF, the PM must be removed by a method such as raising the exhaust gas temperature and activating the catalyst. Regeneration is hereinafter referred to as forced regeneration.

  In order to raise the temperature of exhaust gas from a diesel engine, there is a means called post injection. This is because, during the expansion stroke to the exhaust stroke of a diesel engine, the added fuel is injected into the engine cylinder, and the fuel does not burn in the cylinder, but is oxidized and burned mainly in the exhaust pipe and the catalyst placed there. This increases the temperature of the exhaust gas. Generally, a good effect can be obtained by injecting after the end of the expansion stroke. The post-injection has an advantage that no additional device is required because the added fuel is supplied from the fuel injection nozzle originally provided in the cylinder of the diesel engine. The amount and number of post injections can be controlled to adjust the temperature of the exhaust gas to be heated.

  In addition, if the injection timing of the normal fuel injection of a diesel engine, that is, the fuel injection that is injected in the expansion stroke from the end of the compression stroke and burned in the cylinder of the engine, is delayed, the combustion of the fuel that does not contribute to the engine output torque is caused. As a result, the temperature of the exhaust gas increases. In order to realize such a delay in injection timing, so-called multi-injection is preferable. Multi-injection is performed by dividing fuel injection into multiple parts. In a diesel engine, normally, the fuel that is continuously injected from the end of the compression stroke to the expansion stroke is transferred to an injection method in which the fuel is injected in multiple times. It is possible to easily perform controlled delayed injection.

  Although post injection or multi-injection is an effective means for raising the exhaust gas temperature so as to ensure the activity of the catalyst of the continuous regeneration type DPF, there are cases where sufficient temperature rise cannot be obtained by this alone. Therefore, when an exhaust throttle valve is provided downstream of the continuous regeneration DPF and forced regeneration by post injection or the like is performed, the opening of the exhaust throttle valve is reduced to narrow the exhaust passage, and the heat from the continuous regeneration DPF is reduced. A means for promoting the regeneration of the DPF by activating the catalyst by preventing the diffusion of the catalyst and keeping it warm can be considered. Thus, an exhaust gas aftertreatment device for a diesel engine that combines a continuously regenerating DPF and an exhaust throttle valve is known as disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-343287. If the exhaust gas is throttled, the engine back pressure rises and the load acting on the engine increases, so that the fuel injection amount increases and the exhaust gas temperature further rises. Hereinafter, an exhaust aftertreatment device for a diesel engine will be described with reference to FIG.

  FIG. 6 schematically shows a diesel engine that has a continuously regenerating DPF and an exhaust throttle valve and drives a vehicle. Air is supplied into the cylinder of the diesel engine body 1 through an air cleaner 2 and an intake pipe 3. In the cylinder, fuel is injected from the fuel injection nozzle 4 at the end of the compression stroke, and the injected fuel is mixed with the compressed air and burned in the cylinder to generate power. The exhaust gas after combustion is discharged to the exhaust pipe 5 and a part thereof is recirculated to the intake pipe 3 via the EGR passage 6. The recirculation is performed mainly for the purpose of preventing the generation of NOx, and the amount of exhaust gas recirculated is controlled by the EGR valve 7.

  A continuous regeneration type DPF 8 is installed in the exhaust pipe 5, and an exhaust throttle valve 9 operated by a fluid pressure actuator 92 is installed downstream thereof. The fluid pressure actuator 92 is supplied with a working fluid from a pressure source 93 such as a compressor (air tank) or a vacuum pump mounted on the diesel engine. A three-way solenoid valve 91 is placed in a passage connecting the pressure source 93 and the fluid pressure actuator 92. During normal operation of the diesel engine, atmospheric pressure is applied to the fluid pressure actuator 92 via the three-way solenoid valve 91. And the exhaust throttle valve 9 is held fully open.

  The continuous regeneration type DPF 8 includes a DPF 81 in which a large number of passages are formed in the axial direction of the ceramic body, and an oxidation catalyst 82 disposed upstream thereof. Further, the continuous regeneration type DPF 8 includes a differential pressure sensor 83 that detects a differential pressure between an upstream pressure and a downstream pressure of the DPF 81, an inlet temperature sensor 84 that detects an exhaust gas temperature upstream of the oxidation catalyst 81, and an outlet side. An outlet temperature sensor 85 that detects the temperature of the DPF 81 (inlet side of the DPF 81) is installed, and detection signals from these sensors are input to the engine control device 10 (ECU).

  During operation of the diesel engine, the fuel injected from the fuel injection nozzle 4 burns in the cylinder, and the exhaust gas after combustion is discharged to the exhaust pipe 5. When the exhaust gas passes through the continuous regeneration type DPF 8, the PM in the exhaust gas is captured by the wall surface between the numerous axial passages formed in the DPF 81, and the exhaust gas from which PM is removed is sent downstream of the DPF 81. It is. During the normal operation of the diesel engine, the PM collected and deposited in the DPF 81 is combined with oxygen in the exhaust gas that has become high temperature by the action of the oxidation catalyst 82, and is oxidized and removed.

  However, when the diesel engine is operated at a low load for a long time, the temperature of the exhaust gas is lowered, the activity of the oxidation catalyst 82 is lowered, and the amount of accumulated PM is increased. The differential pressure between the upstream pressure and the downstream pressure increases. When the temperature detected by the inlet temperature sensor 84 and the outlet temperature sensor 85 of the oxidation catalyst 82 decreases and the differential pressure detected by the differential pressure sensor 83 exceeds a predetermined value, the DPF 81 is forcibly regenerated, so that the exhaust gas The ECU 10 outputs a command for performing post injection so as to increase the temperature of the gas. The fuel supplied by the post injection is oxidized and burned in the exhaust pipe 5 or the oxidation catalyst 82, and the exhaust gas temperature becomes high.

  The temperature increase of the exhaust gas due to the post injection is carried out while the vehicle is running, but in the low load region of the engine where the catalyst is not activated, the ECU 10 sets the three-way solenoid valve 91 to further increase the temperature of the exhaust gas. Switch. The working fluid is supplied to the fluid pressure actuator 92 from the pressure source 93, and the opening of the exhaust throttle valve 9 is made very small to strongly restrict the flow of the exhaust gas. As a result, the inside of the continuous regeneration type DPF 8 is kept warm and the load acting on the engine increases, so that the activation of the oxidation catalyst 82 and the regeneration of the DPF 81 are promoted. However, the forced regeneration using the closing of the exhaust throttle valve 9 is performed when the engine is idle while the vehicle is stopped at an intersection or the like. When the vehicle travels again, the exhaust throttle valve 9 is returned to full open. In some cases, the driver may intentionally stop the vehicle and perform forced regeneration using the exhaust throttle valve 9 together.

By the way, when opening the exhaust throttle valve installed in the exhaust pipe, it is known to open the valve by a slow operation. For example, in Japanese Patent Laid-Open No. 2000-337173, an exhaust throttle valve is provided in an exhaust system to promote warming up of a diesel engine, and an orifice is provided in a working fluid passage of a fluid pressure actuator that operates the exhaust throttle valve. When opening the engine from the closed position, a technique for avoiding a sudden change in engine torque by slowing the opening operation is disclosed.
JP 2003-343287 A JP 2000-337173 A

  As described above, in order to oxidize and remove the PM collected by the continuous regeneration type DPF, it is effective to use the exhaust gas at a high temperature by post injection and the exhaust throttle valve in combination. However, if an exhaust throttle valve is provided in the exhaust pipe and the opening thereof is reduced during the forced regeneration of the DPF, the exhaust resistance of the diesel engine is greatly increased, which greatly affects the operation. Therefore, it is desirable that the forced regeneration using the exhaust throttle valve is performed when the vehicle is stopped and the diesel engine is operated in an idle state. Further, since a temporary stop at an intersection or the like often occurs even during operation of the vehicle, when the vehicle temporarily stops during the forced regeneration of the DPF, it is conceivable to use an exhaust throttle valve together.

  In order to drive the temporarily stopped vehicle again, the exhaust throttle valve must be fully opened to return the diesel engine to normal operation. The exhaust throttle valve is returned to the fully open position after the vehicle is intentionally stopped and the exhaust throttle valve is closed for forced regeneration. However, it has been found that an exhaust throttle valve installed downstream of the continuous regeneration type DPF generates loud and harsh noise when it is rapidly returned to full open.

  When the exhaust throttle valve is closed and forced regeneration such as post injection is performed, high-pressure exhaust gas stays upstream of the exhaust pipe. The above noise is caused by the shock pressure wave generated at that time as the exhaust throttle valve opens and the exhaust gas that has accumulated instantaneously drops to near atmospheric pressure and flows into the downstream exhaust pipe. Is. The exhaust gas aftertreatment device such as the continuous regeneration type DPF has a larger cross-sectional area than the exhaust pipe, and a large volume of exhaust gas is stored in the exhaust gas aftertreatment device. It becomes. In order to prevent such noise, the present applicant has found that an exhaust speed relaxation means that gradually opens the exhaust throttle valve is effective, and an orifice is provided in the working fluid passage of the fluid pressure actuator that operates the exhaust throttle valve. A device has been devised to reduce the opening speed of the exhaust throttle valve.

  Decreasing the opening speed of the exhaust throttle valve is effective for reducing noise, but in other aspects, there is a delay in opening, and there is a problem that, for example, it takes time to start after a temporary stop. In particular, the delay increases as the amount of movement of the working fluid required to open and close the exhaust throttle valve increases.

  If the flow of exhaust gas is reduced by reducing the opening of the exhaust throttle valve, a strong force in the valve opening direction acts on the exhaust throttle valve by the high-pressure exhaust gas. In order to counteract this force, the amount and pressure of the working fluid introduced into the fluid pressure actuator are excessive, so a large amount of working fluid must be taken in and out when the exhaust throttle valve is opened. . The present invention reduces the noise when the exhaust throttle valve installed in the diesel engine is opened, and also allows the exhaust throttle valve to which a large amount of working fluid moves to be fully opened in the shortest possible time so that the engine can be started early. The task is to return to normal operation. Such a problem is not limited to the exhaust throttle valve provided for the purpose of regenerating DPF, which is an exhaust gas aftertreatment device of a diesel engine. The present invention is generally applicable to an exhaust throttle valve installed in an exhaust system of an engine.

In view of the above-mentioned problems, the present invention aims to return the exhaust throttle valve installed in the exhaust system of the engine at an early position while reducing the noise when the exhaust throttle valve is held in the closed position and then returning to the fully open position. An orifice and a volume chamber are provided in a passage for supplying a working fluid to a fluid pressure actuator that operates the throttle valve. That is, the present invention
“In an engine in which an exhaust throttle valve operated by a fluid pressure actuator is installed in the engine exhaust system and the opening of the exhaust throttle valve is small in a specific operating state,
The working fluid passage communicating with the fluid pressure actuator is provided with an orifice and a volume chamber. When the opening of the exhaust throttle valve is increased, the orifice is provided through the passage provided with the volume chamber. Working fluid flows "
The engine is characterized by that.

  According to the present invention, as described in claim 2, the exhaust system has a diesel particulate filter that collects particulate matter in the exhaust gas, and a catalyst installed upstream thereof. In a diesel engine that includes a DPF and the exhaust throttle valve is installed on the downstream side of the continuous regeneration type DPF, the exhaust throttle valve can be used as an operating device for the exhaust throttle valve.

  When the exhaust throttle valve operating device of the present invention is applied to the diesel engine of claim 2, the particulate matter deposited on the diesel particulate filter reaches a predetermined amount as described in claim 3. If the vehicle stops and the diesel engine is in an idle state, the fluid pressure actuator is operated so that the opening of the exhaust throttle valve becomes small. Is preferred.

  In the regeneration of the diesel particulate filter described in claim 3, as in claim 4, the added fuel is injected from the fuel injection nozzle in the expansion stroke or the exhaust stroke of the diesel engine, and the regeneration is performed. It is preferable to promote.

  In the present invention, basically, when an exhaust throttle valve operated by a fluid pressure actuator provided in an exhaust system of an engine, for example, an exhaust throttle valve provided for forced regeneration of a DPF, is fully opened, It is applied to a device that reduces the opening speed of the exhaust throttle valve by installing an orifice in the working fluid passage, and is effective for returning the exhaust throttle valve to full opening in as short a time as possible and quickly returning the engine to normal operation. It is a thing. That is, in the present invention, a volume chamber is installed in the working fluid passage of the fluid pressure actuator together with the orifice, and when the exhaust throttle valve is opened, first, the working fluid flows into the volume chamber, and then the exhaust throttle valve is operated by the action of the orifice. Reduce the opening speed of.

  When the flow of exhaust gas is throttled using an exhaust throttle valve such as a butterfly valve, a strong force in the valve opening direction acts on the exhaust throttle valve by the high-pressure exhaust gas of the engine. In order to keep the exhaust gas throttle valve at a throttle position where the valve opening is small against this force, the amount and pressure of the working fluid introduced into the fluid pressure actuator are excessively increased by the amount of the valve throttle position held. ing. When the valve is opened, the working fluid is discharged from the fluid pressure actuator, but the exhaust throttle valve substantially remains in the throttle position until a certain amount of the working fluid is discharged. If only the orifice is installed in the working fluid passage, a certain amount of the excess working fluid will also be delayed due to the throttling action, and the exhaust throttle valve opening speed will decrease during that time. It will be a useless time that does not contribute to. On the other hand, in the present invention, the fixed amount of the working fluid that is initially discharged when the exhaust throttle valve is opened is absorbed by the volume chamber provided in the working fluid passage and is not substantially throttled. There is no time, and the exhaust throttle valve can be fully opened as soon as that time, and the engine can be returned to normal operation.

  According to the exhaust throttle valve operating device of the present invention, the diesel particulate filter for collecting particulate matter in the exhaust gas and the upstream side are installed in the exhaust system of the diesel engine as described in claim 2. The present invention can be applied to an exhaust gas after-treatment device having a formed catalyst, that is, a continuous regeneration type DPF, in which an exhaust throttle valve is installed downstream thereof. In the exhaust throttle valve installed downstream of the continuous regeneration type DPF, it is desirable to reduce the opening speed of the exhaust throttle valve. When the working fluid discharged from the actuator is throttled by the orifice, useless time that does not contribute to a decrease in the opening speed of the exhaust throttle valve is generated, and a response delay occurs. However, when the present invention is applied, it is possible to reduce the noise and to open the exhaust throttle valve with good responsiveness.

  Incidentally, it is disclosed in Patent Document 2 that the valve opening speed is slow when the exhaust throttle valve installed in the exhaust pipe is opened. However, the exhaust throttle valve described therein is located relatively upstream of the exhaust system, and a device with a large volume such as a continuously regenerating DPF is not provided upstream of the exhaust throttle valve. The purpose of slowing down the valve opening speed is to prevent a sudden change in engine torque, and there is no description of noise generated when the exhaust throttle valve is opened.

  When the exhaust throttle valve operating device of the present invention is applied to the diesel engine according to claim 2, the particulate matter accumulated in the DPF reaches a predetermined amount as described in claim 3 and is regenerated. Therefore, the opening of the exhaust throttle valve is made small. The regeneration of the DPF is performed on condition that the vehicle stops and the diesel engine is in an idle state. Under this condition, it is possible to avoid the influence of exhaust gas throttling on vehicle operation. However, when starting after a temporary stop, the engine needs to be quickly brought into normal operation, and the exhaust is exhausted early. The throttle valve must be fully open. The present invention responds to such a request, and by applying the present invention, it is possible to start with a good response while reducing noise and improving drivability (driability).

  Further, as in claim 4, when the added fuel is injected from the fuel injection nozzle in the expansion stroke or exhaust stroke of the diesel engine during the regeneration of the DPF, the fuel is oxidized and burned by the exhaust pipe or the catalyst and exhausted. The temperature of the gas rises and the regeneration of the DPF is promoted.

  Hereinafter, an embodiment in which the exhaust throttle valve operating device of the present invention is applied to an exhaust gas aftertreatment device of a diesel engine will be described with reference to the drawings. FIG. 1 is a schematic view of an exhaust gas aftertreatment device for a diesel engine according to the present invention. Components corresponding to those of the conventional example (FIG. 6) and devices are denoted by the same reference numerals. FIG. 2 schematically shows an exhaust throttle valve and its operating device according to the present invention.

  The basic equipment and operation of the exhaust gas aftertreatment device for a diesel engine according to the present invention is not particularly different from the conventional device shown in FIG. That is, in the cylinder of the diesel engine body 1, the fuel injected from the fuel injection nozzle 4 is mixed with the air supplied from the intake pipe 3 and burned, and the exhaust gas after combustion is discharged to the exhaust pipe 5. Is done. Incidentally, the diesel engine is equipped with a so-called common rail type fuel injection device that injects fuel into each cylinder of the engine by a fuel injection nozzle controlled by a solenoid valve from a fuel storage pipe (common rail). It is possible to inject while precisely controlling the injection timing.

  A continuous regeneration type DPF 8 having a DPF 81 and an oxidation catalyst 82 upstream thereof is installed in the exhaust pipe 5. The DPF 81 is a so-called wall flow type honeycomb filter in which a large number of passages are formed in parallel in a porous ceramic body made of cordierite and the inlets and outlets of the passages are alternately closed, and the exhaust gas Collects PM contained in when passing through the wall surface between passages.

The oxidation catalyst 82 is a catalyst made of a noble metal such as platinum, palladium, or rhodium on the surface of a carrier made of, for example, honeycomb cordierite by coating activated alumina or the like to form a washcoat layer. Those carrying an active ingredient are used. The oxidation catalyst 82 oxidizes HC and CO, which are unburned components in the exhaust gas, to generate H ₂ O and CO ₂ , or oxidizes NO to generate NO ₂ . In such a reaction process of the oxidation catalyst 82, heat is generated and the temperature of the exhaust gas rises. Therefore, PM trapped in the DPF 81 is oxidized and removed, and the DPF 81 is normally regenerated continuously. Of course, it is possible to use other commonly used devices as the DPF 81 or the oxidation catalyst 82. For example, as the DPF 81, a DPF whose surface is coated with a catalyst similar to the above oxidation catalyst or the like is used. It can also be used.

  An exhaust throttle valve 9 is installed downstream of the continuous regeneration type DPF 8. As shown in FIG. 2, the exhaust throttle valve 9 is a commonly used butterfly valve, and is operated by a diaphragm-type fluid pressure actuator 92. Compressed air is guided to the fluid pressure actuator 92 as a working fluid through a passage 97 from a pressure source 93 such as an air tank that stores compressed air of a compressor mounted as an auxiliary machine in a large diesel engine. During normal operation of the diesel engine, atmospheric pressure is guided to the fluid pressure actuator 92 by the three-way solenoid valve 91, and the exhaust throttle valve 9 is held fully open to prevent an increase in exhaust resistance of the diesel engine. Similarly to the conventional example of FIG. 6, the continuous regeneration type DPF 8 includes a differential pressure sensor 83 that detects a differential pressure between the upstream pressure and the downstream pressure of the DPF 81, and exhaust gas on the inlet side and outlet side of the oxidation catalyst 81. An inlet temperature sensor 84 and an outlet temperature sensor 85 for detecting the gas temperatures are provided, and detection signals from these sensors are input to the engine control device 10 (ECU).

  In this embodiment, a diaphragm actuator using compressed air as an operating source is used as the fluid pressure actuator 92, but other fluid pressure actuators can naturally be used. For example, in a relatively small diesel engine including a vacuum pump instead of a compressor, it is preferable to employ a fluid pressure actuator that supplies a negative pressure as a working fluid.

  The present invention is characterized in that an orifice 94 and a volume chamber 95 are installed in a passage 96 connecting the three-way electromagnetic valve 91 for controlling the working fluid of the fluid pressure actuator 92 and the atmosphere. Here, before describing the operation, the configuration and operation of the exhaust gas aftertreatment device of the present invention which is a premise will be first described.

  As described above, when the diesel engine 1 is operated at a low load for a long time, the temperature of the exhaust gas is lowered, the activity of the oxidation catalyst 82 is lowered, and the accumulation amount of PM collected in the DPF 81 is increased. Therefore, it is necessary to perform forced regeneration of the DPF 81 by means such as an increase in injected fuel or post injection. Such forced regeneration is set to be performed automatically, mainly when the vehicle is running, and when the engine is in idle operation due to a temporary stop of the vehicle, the exhaust throttle valve 9 is forced to the throttle position. Playback is set to be performed. However, depending on the driving situation of the vehicle, the accumulated amount of DPF may be large, and forced regeneration using the exhaust throttle valve 9 together with intentionally stopping the vehicle may be required. In the exhaust gas aftertreatment device of the present invention, in order to execute forced regeneration for intentionally stopping the vehicle, a manual regeneration switch 11 operated by the driver is provided, and the driver is informed of the necessity of this forced regeneration. A pilot lamp 12 and a warning lamp 13 are installed.

  When the amount of PM trapped in the DPF 81 increases due to a decrease in the temperature of the exhaust gas, the differential pressure between the upstream pressure and the downstream pressure of the DPF 81 increases. In the present invention, when the temperatures detected by the inlet temperature sensor 84 and the outlet temperature sensor 85 with the oxidation catalyst 82 are equal to or lower than a predetermined value and the differential pressure detected by the differential pressure sensor 83 exceeds the first predetermined value, the pilot The driver is urged to stop the vehicle and press the manual regeneration switch 11 for the forced regeneration using the lamp 12 blinking and the throttle valve 9 together.

  When the driver presses the manual regeneration switch 11 in response to the blinking of the pilot lamp 12, the control device of the exhaust gas aftertreatment device enters a forced regeneration standby state. At this time, when the driver stops the vehicle, returns the accelerator pedal, and the diesel engine 1 is in the idle operation state, the forced regeneration of the DPF 81 using the throttle valve 9 is started. In order to perform this control, the detection signal of the accelerator pedal position sensor 14 and the rotation speed signal from the engine rotation speed sensor 15 input to the ECU 10 are used.

  In this forced regeneration, the three-way solenoid valve 91 is switched to introduce compressed air from the pressure source 93 to the fluid pressure actuator 92, the opening of the exhaust throttle valve 9 is reduced to strongly throttle the exhaust pipe 5, and the diesel engine The feedback control is performed with the idling speed as a target value so as to maintain the idling state. Here, even if the target value of the rotational speed is the idle rotational speed, since the load acting on the diesel engine is increased due to the throttle of the exhaust pipe 5, more fuel is injected than in the normal idle state, As a result, the temperature of the exhaust gas increases. Further, in order to further raise the temperature of the exhaust gas, in this embodiment, both multi-injection and post-injection means are used. That is, by first shifting to the multi-injection, the temperature of the exhaust gas is raised by substantially delaying the injection timing of the fuel injected in the expansion stroke from the end of the compression stroke. After the temperature of the inlet temperature sensor 84 of the oxidation catalyst 82 rises above a certain value by multi-injection, post-injection is performed at the end of the expansion stroke of the diesel engine 1 or at the exhaust stroke. When the temperature of the exhaust gas is raised in advance as described above, a good oxidation reaction in the oxidation catalyst 82 of the fuel added by the post injection is ensured, and the regeneration of the DPF 81 is performed smoothly. It is possible to make more precise adjustments such as dividing the injection amount of the post injection into multiple stages and increasing the injection amount in accordance with the temperature rise of the oxidation catalyst 82.

  Despite the blinking of the pilot lamp 12, if the driver does not operate the manual regeneration switch 11 or forcibly regenerates for some reason, PM will continue to accumulate in the DPF 81 and the differential pressure detected by the differential pressure sensor 83. Increases further. When the differential pressure reaches the second predetermined value as the amount of accumulated PM increases, the flashing cycle of the pilot lamp 12 is shortened so as to flash quickly, thereby prompting the driver to perform early forced regeneration. Accordingly, the warning lamp 13 is turned on when the driver does not perform the forced regeneration in which the vehicle is stopped and PM continues to accumulate and the differential pressure reaches the third predetermined value. The warning lamp 13 gives a warning to the driver because a large amount of PM is accumulated in the DPF 81 in this state, and if forced regeneration is performed, the amount of heat generated by the oxidation combustion of the PM becomes excessive, and the DPF 81 and the like are This is because there is a risk of damage. When the warning lamp 13 is turned on, the driver carries the vehicle into a maintenance shop or the like, and here, the accumulated PM is removed by a method such as so-called backwashing or combustion taking a long time. As described above, the exhaust aftertreatment device of the present invention is provided with a three-stage alarm means according to the amount of accumulated PM, and gives the driver a detailed forced regeneration instruction.

  Here, the operation of the orifice 94 and the volume chamber 95, which is a feature of the present invention, will be described. When forced regeneration is performed with the opening of the exhaust throttle valve being reduced and held at the throttle position as the vehicle is temporarily stopped, the exhaust throttle valve 9 needs to be fully opened when the vehicle re-runs. Returning the exhaust throttle valve to full open is the same as for forced regeneration by intentional stopping as described above. However, when the vehicle is temporarily stopped at an intersection or the like, the exhaust throttle valve 9 is returned to full open in a short time. The vehicle must be started by returning the engine to normal operation at an early stage.

  As described above, when the exhaust throttle valve 9 is opened rapidly, the high-pressure exhaust gas in the continuous regeneration DPF 8 having a large upstream volume is instantaneously released, and a large noise is generated. As shown in FIG. 3, the noise increases as the opening speed of the exhaust throttle valve 9 increases. When the exhaust throttle valve 9 is opened, the three-way electromagnetic valve 91 is switched to release the compressed air, which is the working fluid of the fluid pressure actuator 92, to the atmosphere. In the present invention, the orifice 94 placed in the passage 96 Due to the action, the speed of the fluid pressure actuator 92 at this time becomes a low speed. Therefore, the exhaust throttle valve 9 gradually increases its opening, and it is avoided that the high-pressure exhaust gas stored in the upstream continuous regeneration type DPF 8 is suddenly dropped. The noise generated will be greatly reduced.

  By the way, when the engine is operated with the exhaust throttle valve 9 as the throttle position, an excessive pressure is applied to the fluid pressure actuator 92 by the working fluid introduced from the passage 97 in order to hold the exhaust throttle valve 9 in that position. There is a need. In other words, the pressure in the fluid pressure actuator 92 at this time is the pressure indicated by point A in FIG. 4 showing the relationship between the working fluid pressure and the stroke, and thus the exhaust throttle valve 9 corresponds to the throttle position. It is pressed against a stopper or the like to be opposed to the force in the valve opening direction acting on the stopper. Therefore, even if the three-way solenoid valve 91 is switched when the exhaust throttle valve 9 is opened and the working fluid in the fluid pressure actuator 92 is discharged, the opening degree of the exhaust throttle valve 9 does not change until the pressure drops to the B point. In this period, the high pressure exhaust gas in the continuous regeneration type DPF 8 does not cause a pressure drop. In other words, operating the orifice during this time will unnecessarily delay the opening time regardless of noise reduction.

  In the present invention, a volume chamber 95 is placed together with an orifice 94 in a passage 96 for discharging the working fluid to the atmosphere. Accordingly, the initial amount of the working fluid discharged from the fluid pressure actuator 92 when the exhaust throttle valve 9 is opened is first absorbed by the volume chamber 95. Since the volume chamber 95 is placed in front of the orifice 94, this fixed amount of working fluid is not subjected to the throttling action and moves rapidly to the volume chamber 95, and the pressure in the fluid pressure actuator 92 is almost delayed. Without descending from point A to point B in FIG. Thereafter, the pressure gradually decreases due to the throttle action of the orifice 94, and the opening speed of the exhaust throttle valve 9 is made slow to prevent the generation of noise. Eventually, the pressure of the fluid pressure actuator 92 becomes atmospheric pressure, and the exhaust throttle valve 9 returns to the fully opened position.

  When an actuator using negative pressure as the working fluid is used as the fluid pressure actuator 92, atmospheric pressure is introduced into the fluid pressure actuator 92 from the passage 96 in order to open the exhaust throttle valve 9. Even in this case, since the atmosphere is stored in the volume chamber 95, the atmosphere is first drawn into the fluid pressure actuator 92 without being subjected to the restricting action of the orifice 94, and the excessive negative pressure is instantaneously reduced to release time. Prevent unnecessary delays. That is, even when a negative pressure actuator is used as the fluid pressure actuator 92, a wasteful operation delay of the exhaust throttle valve 9 can be avoided by the same configuration as in this embodiment.

  FIG. 5 shows the operation over time of the operating device of the present invention provided with the volume chamber 95 in comparison with the operating device having only the orifice. When a switching signal is input to the three-way electromagnetic valve 91 to open the exhaust throttle valve 9 and the fluid pressure actuator 92 communicates with the passage 96 to the atmosphere, the operating fluid in the fluid pressure actuator 92 is used in the operating device of the present invention. As a result, the pressure rapidly decreases from point A to point B, as shown by the solid line in FIG. Thereafter, the pressure in the fluid pressure actuator 92 gradually decreases to atmospheric pressure due to the restriction effect of the orifice 94. On the other hand, in the case of having only the orifice, the working fluid discharged from the fluid pressure actuator 92 is subjected to the orifice throttling action from the beginning, and the pressure drop is significantly delayed as shown by the broken line.

  Due to this difference in the pressure drop in the fluid pressure actuator 92, the operating device of the present invention reduces the noise when the exhaust throttle valve 9 is opened and shortens the required time shown by C in FIG. It is done. Therefore, after the vehicle is temporarily stopped, the exhaust throttle valve 9 can be fully opened in a short time, the engine can be returned to normal operation at an early stage, and the vehicle can be started, thereby improving drivability.

  As described in detail above, the present invention aims to return the exhaust throttle valve installed in the exhaust system of the engine at an early position while reducing the noise when the exhaust throttle valve is held in the closed position and then returning to the fully open position. An orifice and a volume chamber are provided in a passage for supplying a working fluid to a fluid pressure actuator that operates the throttle valve. The exhaust throttle valve installed in the exhaust system of the engine is not limited to the exhaust throttle valve provided for the purpose of regenerating the DPF which is the exhaust gas aftertreatment device of the diesel engine described in the embodiment. For example, Patent Document 2 describes a technique for opening an exhaust throttle valve provided for promoting warm-up of an engine at a slow speed. It is also a common technique to use an exhaust throttle valve as a so-called exhaust brake. From the object and configuration of the present invention, it is apparent that the present invention is applicable to such an exhaust throttle valve operating device.

It is the schematic of the diesel engine using the operating device of the exhaust throttle valve of this invention. It is the schematic of the exhaust throttle valve and operating device based on this invention. It is a graph which shows the relationship between an exhaust throttle valve opening speed and a noise level. It is a graph which shows the relationship between the operating pressure of a fluid pressure actuator, and a stroke. It is a figure which shows the action | operation of the operating device of the exhaust throttle valve of this invention. It is the schematic of the conventional diesel engine using an exhaust throttle valve.

Explanation of symbols

1 Diesel engine body 4 Injection nozzle 5 Exhaust pipe 8 Continuous regeneration type DPF
81 DPF
82 Oxidation catalyst 83 Differential pressure sensor 9 Exhaust throttle valve 91 Three-way solenoid valve 92 Fluid pressure actuator 94 Orifice 95 Volume chamber 10 Engine control unit (ECU)
11 Manual regeneration switch 12 Pilot lamp 13 Warning lamp

Claims (4)

An exhaust throttle valve (9) operated by a fluid pressure actuator (92) is installed in the engine exhaust system, and the exhaust throttle valve of the engine that reduces the opening of the exhaust throttle valve (9) in a specific operation state. In the operating device,
When the working fluid passage (96) communicating with the fluid pressure actuator (92) is provided with an orifice (94) and a volume chamber (95), the exhaust throttle valve (9) has a large opening. Is an exhaust throttle valve operating device in which a working fluid flows through a passage (96) provided with the orifice (94) and a volume chamber (95). The engine is a diesel engine, and its exhaust system has a diesel particulate filter (81) for collecting particulate matter in exhaust gas and a catalyst (82) installed on the upstream side thereof. The exhaust throttle valve operating device according to claim 1, further comprising a continuous regeneration type DPF (8), wherein the exhaust throttle valve (9) is disposed downstream of the continuous regeneration type DPF (8). When the particulate matter deposited on the diesel particulate filter (81) reaches a predetermined amount, when the vehicle stops and the diesel engine is in an idle state, the diesel particulate filter 3. The exhaust throttle valve operating device according to claim 2, wherein, in order to regenerate the filter (81), the exhaust throttle valve (9) is operated by the fluid pressure actuator (92) so that the opening degree thereof is reduced. The exhaust gas according to claim 3, wherein when the diesel engine regenerates the diesel particulate filter (81), the diesel engine injects additional fuel from a fuel injection nozzle (4) in an expansion stroke or an exhaust stroke of the diesel engine. Throttle valve operating device.

Images