JP5655114B2 - Exhaust gas purification system - Google Patents

Description

  The present invention relates to a technology of an exhaust gas purification system provided with an oxidation catalyst and a particulate filter in an exhaust passage of an engine.

  Conventionally, an exhaust gas purification system that purifies exhaust gas by removing particulate matter contained in exhaust gas exhausted from a diesel engine is known. As this exhaust gas purification system, a particulate matter removing device consisting of an oxidation catalyst and a diesel particulate filter (hereinafter referred to as DPF) is arranged in the exhaust passage of the engine, and the exhaust gas is allowed to flow therethrough. There are those that reduce or remove particulate matter contained in the exhaust gas.

  In such an exhaust gas purification system, unburned hydrocarbon (hereinafter referred to as HC), water vapor and the like discharged during idling are adsorbed and accumulated on the surface of the oxidation catalyst or the surface of the DPF. Here, before the oxidation catalyst reaches the activation temperature, unburned HC is adsorbed and accumulated on the oxidation catalyst or DPF, and when the exhaust gas flow rate is increased by starting running in this state, By the exhaust gas, the unburned HC adsorbed on the oxidation catalyst and the DPF is desorbed all at once and discharged as white smoke from the rear end of the exhaust passage into the atmosphere. For this reason, there were problems such as poor visibility and bad odor of the following vehicles.

  In order to solve the above problems, exhaust gas purification systems such as Patent Document 1 and Patent Document 2 have been proposed. The exhaust gas purification system of Patent Document 1 measures the exhaust gas temperature on the inlet side of the filter, and the measured temperature is at a low exhaust gas temperature (unburned HC is not oxidized in the oxidation catalyst but accumulated. The cumulative time of the operating state at such a low exhaust gas temperature is measured. When the accumulated time exceeds a predetermined time, it is determined that a considerable amount of unburned HC has accumulated, and the exhaust gas temperature raising control operation is performed to prevent the generation of white smoke. Further, the exhaust gas purification system of Patent Document 2 is configured to measure the duration of the idling state and reduce the flow rate of the exhaust gas by closing the throttle valve when the duration exceeds a predetermined judgment value. ing. The exhaust gas purification system of Patent Document 2 raises the exhaust gas temperature by reducing the flow rate of the exhaust gas using a throttle valve. Then, by raising the exhaust gas temperature, the oxidation catalyst is heated to the activation temperature, and the adsorbed unburned HC is removed by oxidation, thereby preventing the generation of white smoke.

JP 2004-108320 A Japanese Patent Laid-Open No. 2004-1000066

  However, in the exhaust gas purification system of Patent Document 1, it is determined whether the accumulated time when the exhaust gas temperature is at a low exhaust temperature has reached a predetermined time or more, and when it is determined that the accumulated time has become a predetermined time or more, Since the exhaust gas temperature rise control operation (white smoke prevention operation) is performed, the temperature rise control (white smoke prevention operation) is not performed until the accumulated time elapses, and the white smoke removal is not performed promptly. there were.

  Further, in the exhaust gas purification system of Patent Document 2, whether to perform the white smoke prevention operation is determined based on the duration of the idling state detected from the engine speed, the accelerator opening, and the like. Depending on the operating conditions, the exhaust gas temperature may increase even at the same engine speed and duration. Therefore, even when the exhaust gas temperature is high, there is a problem that unnecessary white smoke removal operation is performed and unnecessary fuel is consumed.

  The present invention has been made to solve such a problem, and provides an exhaust gas purification system capable of accurately performing white smoke prevention operation for preventing the generation of white smoke and suppressing fuel consumption. The purpose is to do.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

In the exhaust gas purification system for purifying the exhaust gas of the engine by providing an EGR device, an oxidation catalyst, and a particulate filter in the exhaust passage of the engine, the oxidation catalyst is discharged before reaching the activation temperature. If unburned hydrocarbon or water vapor adsorbs and accumulates on the surface of the oxidation catalyst or particulate filter and the exhaust gas flow rate increases in this state, the adsorbed unburned hydrocarbon is removed at once. Control for automatically performing white smoke prevention operation that eliminates white smoke released into the atmosphere, and is provided on the outlet side of the particulate filter to detect the temperature of the exhaust gas. Based on the detection means and the detection result of the outlet side temperature detection means, the temperature state of the exhaust gas at the outlet side of the particulate filter is determined. An exhaust gas temperature determining means, and an exhaust gas temperature adjusting means for adjusting the temperature of the exhaust gas based on the determination result of the exhaust gas temperature determining means, and the exhaust gas temperature determining means at the outlet side of the particulate filter. When it is determined that the temperature of the exhaust gas is lower than a predetermined set value, the exhaust gas temperature adjusting means starts the white smoke prevention operation for raising the temperature of the exhaust gas to the activation temperature of the oxidation catalyst, and the exhaust gas temperature The adjusting means includes an intake adjusting means for adjusting the intake throttle of the engine, an exhaust adjusting means for adjusting the exhaust throttle of the engine, and an EGR adjusting means for adjusting the EGR valve of the engine . and it can change the opening and closing speed and the opening and closing timing of an intake throttle, the exhaust adjusting means, the opening and closing speed and the opening and closing of the exhaust throttle Timing and changeable, when starting white smoke prevention operation, the EGR adjusting means, before the start, is to forcibly fully closed the EGR valve of the EGR device.

According to a second aspect of the present invention, in the exhaust gas purification system according to the first aspect, when the engine is in an operating state, the outlet side temperature detecting means acquires the temperature of the exhaust gas at the outlet side of the particulate filter, and the white smoke It is determined whether there is a signal indicating that the prevention operation is performed, and when the exhaust gas temperature determination unit determines that there is no signal indicating that the white smoke prevention operation is performed, the particulate filter obtained from the outlet side temperature detection unit is determined. The temperature of the exhaust gas on the outlet side is compared with the first set temperature, which is the temperature at which the activation of the oxidation catalyst begins, and it is determined whether the temperature of the exhaust gas is lower than the first set temperature, thereby preventing white smoke If it is determined that there is a signal indicating that the operation is to be performed, the temperature of the exhaust gas on the outlet side acquired by the outlet side temperature detecting means and the temperature higher than the first set temperature and the oxidation catalyst is sufficient Comparing the second set temperature is the temperature at which sex is to determine whether to start the white smoke prevention operation.

  As effects of the present invention, the following effects can be obtained.

In the exhaust gas purification system for purifying the exhaust gas of the engine by providing an EGR device, an oxidation catalyst, and a particulate filter in the exhaust passage of the engine, the oxidation catalyst is discharged before reaching the activation temperature. If unburned hydrocarbon or water vapor adsorbs and accumulates on the surface of the oxidation catalyst or particulate filter and the exhaust gas flow rate increases in this state, the adsorbed unburned hydrocarbon is removed at once. Control for automatically performing white smoke prevention operation that eliminates white smoke released into the atmosphere, and is provided on the outlet side of the particulate filter to detect the temperature of the exhaust gas. Based on the detection means and the detection result of the outlet side temperature detection means, the temperature state of the exhaust gas at the outlet side of the particulate filter is determined. An exhaust gas temperature determining means, and an exhaust gas temperature adjusting means for adjusting the temperature of the exhaust gas based on the determination result of the exhaust gas temperature determining means, and the exhaust gas temperature determining means at the outlet side of the particulate filter. When it is determined that the temperature of the exhaust gas is lower than a predetermined set value, the exhaust gas temperature adjusting means starts the white smoke prevention operation for raising the temperature of the exhaust gas to the activation temperature of the oxidation catalyst, and the exhaust gas temperature The adjusting means includes an intake adjusting means for adjusting the intake throttle of the engine, an exhaust adjusting means for adjusting the exhaust throttle of the engine, and an EGR adjusting means for adjusting the EGR valve of the engine . and it can change the opening and closing speed and the opening and closing timing of an intake throttle, the exhaust adjusting means, the opening and closing speed and the opening and closing of the exhaust throttle Timing and changeable, when starting white smoke prevention operation, the EGR adjusting means, before the start, by forcibly fully closed the EGR valve of the EGR device, to prevent the occurrence of white smoke white smoke The prevention operation can be performed with high accuracy and the consumption of fuel can be suppressed.

The exhaust gas temperature adjusting means includes an intake air adjusting means for adjusting an intake throttle of the engine and an exhaust gas adjusting means for adjusting the exhaust throttle of the engine. The intake air adjusting means includes an opening / closing speed and an opening / closing timing of the intake throttle. The exhaust adjustment means can change the opening / closing speed and timing of the exhaust throttle, so that when the engine operating state is in a steady state or a transient state, the intake throttle and / or Alternatively, by changing the opening / closing speed of the exhaust throttle, rapid fluctuations in the engine can be suppressed in a steady state, and the generation of white smoke can be quickly reduced in a transient state.

According to a second aspect of the present invention, in the exhaust gas purification system according to the first aspect, when the engine is in an operating state, the outlet side temperature detecting means acquires the temperature of the exhaust gas at the outlet side of the particulate filter, and the white smoke It is determined whether there is a signal indicating that the prevention operation is performed, and when the exhaust gas temperature determination unit determines that there is no signal indicating that the white smoke prevention operation is performed, the particulate filter obtained from the outlet side temperature detection unit is determined. The temperature of the exhaust gas on the outlet side is compared with the first set temperature, which is the temperature at which the activation of the oxidation catalyst begins, and it is determined whether the temperature of the exhaust gas is lower than the first set temperature, thereby preventing white smoke If it is determined that there is a signal indicating that the operation is to be performed, the temperature of the exhaust gas on the outlet side acquired by the outlet side temperature detecting means and the temperature higher than the first set temperature and the oxidation catalyst is sufficient The second set temperature, which is a characteristic temperature, is compared to determine whether to start the white smoke prevention operation. Therefore, even if it is determined that there is no signal indicating the white smoke prevention operation, the white smoke prevention operation is performed. Even when it is determined that there is a signal to do so, it is possible to determine whether to perform white smoke prevention operation only with the exhaust gas temperature on the outlet side of the particulate filter, so it is possible to accurately perform white smoke prevention operation, Fuel consumption can be suppressed.

1 is an overall schematic diagram of an exhaust gas purification system. The block diagram which shows the control structure of a control apparatus (ECU). The flowchart which shows white smoke abnormal discharge possibility determination. The flowchart which shows a white smoke prevention driving | operation. The flowchart which shows a white smoke prevention driving | operation.

  Hereinafter, the overall configuration of the exhaust gas purification system 100 will be described.

  As shown in FIG. 1, in the engine 20, the intake manifold 24 is provided on one side of the cylinder head 23 and can communicate with a combustion chamber (not shown). An intake passage 25 communicates with the intake manifold 24. The intake passage 25 is provided with an intake throttle 31 having a throttle.

  The intake throttle 31 adjusts the amount of intake air to the intake manifold 24 of the engine 20. The passage area of the intake passage 25 is changed by opening and closing the intake throttle 31, and the amount of intake air to the intake manifold 24 is determined according to the passage area. The intake throttle 31 is connected to a control device (ECU: engine control unit) 50.

  In the engine 20, the exhaust manifold 21 is provided on the other side of the cylinder head 23 and can communicate with a combustion chamber (not shown). An exhaust passage 22 communicates with the exhaust manifold 21. The exhaust passage 22 is provided with an exhaust throttle 32 having a throttle.

  The exhaust throttle 32 adjusts the exhaust amount from the exhaust manifold 21 of the engine 20. The passage area of the exhaust passage 22 is changed by opening and closing the exhaust throttle 32, and the amount of exhaust from the exhaust manifold 21 is determined according to the passage area. The exhaust throttle 32 is connected to the control device 50.

  In addition, an EGR device 40 is provided between the intake passage 25 downstream of the intake throttle 31 and the exhaust passage 22 upstream of the exhaust throttle 32. The EGR device 40 recirculates a part of the exhaust gas exhausted from the exhaust manifold 21 of the engine 20 to the intake air as EGR gas. In the EGR device 40, an EGR passage 41 is provided between the intake passage 25 and the exhaust passage 22 to communicate these. An EGR valve 42 and an EGR cooler 43 are disposed in the EGR passage 41.

  The EGR valve 42 is a valve that adjusts the flow rate of the EGR gas, and is provided in the middle of the EGR passage 41. The passage area of the EGR passage 41 is changed by opening and closing the EGR valve 42, and the recirculation amount of the EGR gas recirculated through the EGR device 40 is determined according to the passage area. The EGR valve 42 is connected to the control device 50. The EGR cooler 43 cools high-temperature EGR gas, and is provided in the middle of the EGR passage 41 and upstream of the EGR valve 42 in the EGR passage 41.

  As shown in FIG. 1, the exhaust gas purification system 100 includes a particulate matter removing device 10 in an exhaust passage 22 connected to an exhaust manifold 21 of an engine 20.

  The particulate matter removing device 10 is a device that removes particulate matter contained in exhaust gas exhausted from the engine 20, and includes an oxidation catalyst 11, a DPF 12, a differential pressure sensor 13, and a temperature sensor 14. It has.

  The oxidation catalyst 11 is provided on the upstream side of the particulate matter removing device 10 and has a monolithic carrier (not shown) in which a grid-like (honeycomb-like) passage is formed in the exhaust gas flow direction (arrow 90). is there. A catalytic metal such as platinum, rhodium or palladium is supported on the monolith support.

  The DPF 12 is a substantially cylindrical honeycomb filter provided on the downstream side of the particulate matter removing device 10. The DPF 12 has a polygonal cross section partitioned by porous partition walls made of ceramics such as cordierite. The DPF 12 is configured by substantially sealing alternately adjacent inlet portions and outlet portions of a plurality of through holes formed in parallel with each other by the partition walls. The partition walls are coated with a catalytic metal such as platinum to carry a catalytic function. The DPF 12 is configured to collect particulate matter contained in the exhaust gas by allowing the exhaust gas of the engine 20 introduced from the inlet side of the DPF 12 to pass through the through hole formed by the partition wall.

  The differential pressure sensor 13 is a sensor that detects a differential pressure between the inlet side and the outlet side of the particulate matter removing device 10, and is a conducting tube having both ends connected to the inlet side and the outlet side of the particulate matter removing device 10, respectively. 15 in the middle. Based on the detection result of the differential pressure sensor 13, the amount of particulate matter accumulated in the DPF 12 is estimated by the control device 50. Further, based on the detection result of the differential pressure sensor 13, the control device 50 determines whether or not to perform regeneration control of the DPF 12.

  The temperature sensor 14 is provided on the outlet side of the particulate matter removing device 10 (DPF 12) as outlet side temperature detecting means. The temperature sensor 14 detects the temperature of the exhaust gas at the outlet side of the particulate matter removing device 10 (DPF 12), that is, the temperature of the exhaust gas immediately after passing through the DPF 12.

  Next, the control configuration of the exhaust gas purification system 100 will be described.

  As shown in FIG. 1, the exhaust gas purification system 100 includes a control device 50.

  The control device 50 performs overall control of the operation of the engine 20 and performs regeneration control of the DPF 12. In the control device 50, a CPU (Central Processing Unit) and ROM, RAM, HDD, etc. as storage devices are connected by a bus. A control program is stored in the storage device.

  A differential pressure sensor 13 and a temperature sensor 14 are connected to the control device 50. The differential pressure on the inlet side and the outlet side of the particulate matter removing device 10 is detected by the differential pressure sensor 13 and input to the control device 50. The control device 50 estimates the amount of particulate matter deposited on the DPF 12 based on the detection result of the differential pressure sensor 13. Further, the temperature of the exhaust gas immediately after passing through the DPF 12 is detected by the temperature sensor 14 and input to the control device 50.

  The control device 50 is further connected with an intake throttle 31, an exhaust throttle 32, an EGR valve 42, and a notification means 60.

  The notification means 60 is means for notifying the operator that the white smoke prevention operation described later is started. For example, the notification unit 60 is configured to provide a display lamp (not shown) on the display panel and to light or blink when the white smoke prevention operation is started. However, the notification means 60 may be configured such that a speaker, a buzzer, or the like is provided on the display panel so that a notification sound is generated during the white smoke prevention operation. Further, the notification means 60 is not limited to the configuration provided on the display panel, and may be configured to be disposed at another position.

  As shown in FIG. 2, the control device 50 is provided with exhaust gas temperature determination means 51, exhaust gas temperature adjustment means 52, white smoke timer 53, and intake throttle timer 57. The exhaust gas temperature determining means 51 acquires the temperature of the exhaust gas immediately after passing through the DPF 12 detected by the temperature sensor 14, and compares the acquired exhaust gas temperature with a predetermined set value set in advance. This is a means for determining the temperature state of the acquired exhaust gas.

  The exhaust gas temperature adjusting means 52 adjusts the intake throttle 31, exhaust throttle 32, and EGR valve 42 according to the determination result of the exhaust gas temperature determining means 51 and the operating state (steady state, transient state) of the engine 20. Thus, the temperature of the exhaust gas flowing through the particulate matter removing device 10 is adjusted. The exhaust gas temperature adjusting means 52 includes an intake air adjusting means 54, an exhaust adjusting means 55, and an EGR adjusting means 56. The intake air adjusting means 54 adjusts the intake air throttle 31 of the engine 20. The intake air adjusting means 54 changes the opening / closing speed and opening / closing timing of the intake throttle 31 according to the determination result of the exhaust gas temperature determining means 51, the operating state of the engine 20, or the detection result of the temperature sensor 14. The exhaust adjusting means 55 adjusts the exhaust throttle 32 of the engine 20. The exhaust adjustment unit 55 changes the opening / closing speed and the opening / closing timing of the exhaust throttle 32 according to the determination result of the exhaust gas temperature determination unit 51, the operating state of the engine 20, or the detection result of the temperature sensor 14. The EGR adjustment means 56 adjusts the EGR valve 42 of the engine 20.

  The white smoke timer 53 counts the time until the white smoke prevention operation described later is started. The white smoke timer 53 can set an arbitrary time. The control device 50 is configured to start the white smoke prevention operation after the white smoke timer 53 starts counting and a preset time set in the white smoke timer 53 elapses.

  The intake throttle timer 57 counts the time until the opening / closing of the intake throttle 31 is started. The intake throttle timer 57 can set an arbitrary time. The control device 50 does not open / close the intake throttle 31 until the count of the intake throttle timer 57 is released, and can shift the timing of closing each throttle so that the intake throttle 31 is not closed before the exhaust throttle 32 is closed. It is configured to be able to.

  Next, the white smoke abnormal discharge possibility determination performed before starting the white smoke prevention operation will be described.

  The exhaust gas purification system 100 performs the white smoke prevention operation described below in order to prevent the abnormal discharge of white smoke generated by the accumulation of unburned HC in the particulate matter removing device 10. First, the exhaust gas purification system 100 determines whether or not white smoke may be abnormally discharged. Then, the exhaust gas purification system 100 performs the white smoke prevention operation based on the result of the determination.

  As shown in FIG. 3, when the engine 20 is in an operating state (S1), the temperature sensor 14 detects the temperature (Tdpf) of the exhaust gas at the outlet side of the particulate matter removing device 10 (DPF 12) (S2). The control device 50 acquires the temperature (Tdpf) of the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) detected by the temperature sensor 14 (S3). Based on the acquired exhaust gas temperature (Tdpf), the control device 50 determines whether there is a signal indicating that the white smoke prevention operation is performed (white smoke flag) (the signal is 1 or 0) ( S4).

  Here, when the engine 20 is in the operating state, the control device 50 repeatedly performs the following series of white smoke abnormal discharge possibility determinations. Further, in the determination of the possibility of abnormal white smoke discharge, when the following predetermined condition is satisfied, the white smoke timer 53 starts counting and a signal indicating that the white smoke prevention operation is performed is issued. The signal indicating that the white smoke prevention operation is performed is not canceled until the white smoke timer 53 is reset. Therefore, it is determined whether or not there is a signal indicating that the white smoke prevention operation is performed in step S4 as a premise of performing the white smoke abnormal discharge possibility determination.

  First, the case where the control device 50 determines in step S4 that there is no signal indicating that the white smoke prevention operation is performed (S4-No) will be described.

  In step S4, when it is determined that there is no signal indicating that the white smoke prevention operation is performed (S4-No), the control device 50 detects the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14. Is compared with a first preset temperature, and it is determined whether or not the exhaust gas temperature (Tdpf) is lower than the first preset temperature (S5). The preset first set temperature here is the lowest temperature at which the oxidation catalyst 11 is activated, in other words, the temperature at which activation starts. When the outlet side temperature of the acquired particulate matter removing device 10 (DPF 12) is lower than the first set temperature, the temperature in the particulate matter removing device 10 is lower than the activation temperature of the oxidation catalyst 11, so HC is not oxidized by the oxidation catalyst 11 and is adsorbed and accumulated on the oxidation catalyst 11 and the DPF 12. Therefore, when the obtained outlet temperature of the particulate matter removing device 10 (DPF 12) is lower than the first set temperature, it is necessary to perform the white smoke prevention operation.

  In step S5, when it is determined that the obtained outlet temperature of the particulate matter removing device 10 (DPF 12) is not lower than the first set temperature (S5-No), that is, it is determined that it is not necessary to perform the white smoke prevention operation. If so, the control device 50 determines whether or not it is necessary to perform regeneration control of the DPF 12 (S6).

  When it is determined in step S6 that it is necessary to perform regeneration control of the DPF 12 (S6-Yes), the control device 50 performs regeneration control of the DPF 12 (S7). When it is determined in step S6 that it is not necessary to perform regeneration control of the DPF 12 (S6-No), the control device 50 detects the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) detected by the temperature sensor 14. The temperature (Tdpf) is acquired (S3).

  In Step S5, when it is determined that the temperature (Tdpf) of the exhaust gas at the outlet side of the acquired particulate matter removing device 10 (DPF 12) is lower than the first set temperature (S5-Yes), that is, white smoke When determining that it is necessary to perform the prevention operation, the control device 50 starts counting of the white smoke timer 53 (S8) and outputs a signal to start the white smoke prevention operation (S9). At this time, the control device 50 operates the notification means 60 to notify that the exhaust gas temperature adjustment means 52 starts to raise the temperature of the exhaust gas, that is, starts the white smoke prevention operation.

  As described above, the control device 50 determines that there is no signal indicating that the white smoke prevention operation is performed (S4-No), and on the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14. When it is determined that the temperature (Tdpf) of the exhaust gas is lower than the first set temperature (S5-Yes), the white smoke timer 53 starts counting (S8) and a signal indicating that the white smoke prevention operation is performed. (S9).

  When the control device 50 issues a signal indicating that the white smoke prevention operation is performed in step S9, the control device 50 determines whether or not a predetermined time (set time) has elapsed since the counting by the white smoke timer 53 started ( S10). Since the control device 50 does not start the white smoke prevention operation unless the set time set in the white smoke timer 53 has elapsed, the control device 50 determines the count of the white smoke timer 53 here.

  In step S10, when it is determined that the predetermined time has elapsed since the counting of the white smoke timer 53 was started (S10-Yes), the control device 50 forcibly controls the EGR valve 42 by the EGR adjustment means 56. It is closed (S11), and white smoke prevention operation is started (S12). In Step S10, when it is determined that the predetermined time has not elapsed since the counting of the white smoke timer 53 is started (S10-No), the control device 50 needs to perform regeneration control of the DPF 12. (S6).

  Next, the case where the control device 50 determines in step S4 that there is a signal indicating that the white smoke prevention operation is performed (S4-Yes) will be described.

  In step S4, when it is determined that there is a signal indicating that the white smoke prevention operation is performed (S4-Yes), that is, when the white smoke timer 53 starts counting and a signal indicating that the white smoke prevention operation is performed is issued. The control device 50 compares the exhaust gas temperature (Tdpf) on the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14 with a preset second set temperature, and acquires the acquired exhaust gas. It is determined whether the gas temperature (Tdpf) is lower than the second set temperature (S13). Here, the preset second preset temperature is a temperature higher than the first preset temperature, and is a temperature at which the oxidation catalyst 11 is sufficiently activated and does not cause melting.

  When it is determined in step S13 that the exhaust gas temperature (Tdpf) on the outlet side of the acquired particulate matter removing device 10 (DPF 12) is not lower than the second set temperature (S13-No), the particulate matter removing device 10 Since the temperature of the exhaust gas is high, there is no need to perform the white smoke prevention operation, and the control device 50 resets the count of the white smoke timer 53 (S14) and cancels the signal indicating that the white smoke prevention operation is performed. (S15). That is, it shifts to normal operation. Then, the control device 50 determines whether or not it is necessary to perform regeneration control of the DPF 12 (S6). On the other hand, when it is determined in step S13 that the exhaust gas temperature (Tdpf) on the outlet side of the acquired particulate matter removing device 10 (DPF 12) is lower than the second set temperature (S13-Yes), the control device 50 Then, it is determined whether or not a predetermined time has elapsed since the counting of the white smoke timer 53 was started (S10). This predetermined time is the time until the white smoke prevention operation is possible, and if the white smoke prevention operation is started when the engine 20 is cold, there is a risk that more white smoke will accumulate and abnormal discharge will occur. Is set to be.

  In step S10, when it is determined that the predetermined time has elapsed since the counting of the white smoke timer 53 was started (S10-Yes), the control device 50 forcibly controls the EGR valve 42 by the EGR adjustment means 56. It is closed (S11), and white smoke prevention operation is started (S12). In Step S10, when it is determined that the predetermined time has not elapsed since the start of the white smoke timer 53 (S10-No), the control device 50 needs to perform regeneration control of the particulate matter removing device 10. It is determined whether or not there is (S6).

  Next, the white smoke prevention operation in the exhaust gas purification system 100 will be described.

  As shown in FIG. 4, when the white smoke prevention operation is started after the determination of the possibility of abnormal white smoke discharge (S12), the temperature sensor 14 performs exhaust on the outlet side of the particulate matter removing device 10 (DPF 12). The gas temperature (Tdpf) is detected (S21). The control device 50 acquires the temperature (Tdpf) of the exhaust gas detected by the temperature sensor 14 (S22). The control device 50 compares the exhaust gas temperature (Tdpf) acquired from the temperature sensor 14 with a first preset temperature, and the acquired outlet temperature of the particulate matter removing device 10 (DPF 12) is the first temperature. It is determined whether the temperature is equal to or higher than one set temperature (S23). Here, the preset first preset temperature refers to the lowest value of the activation temperature of the oxidation catalyst 11 as in the first preset temperature.

  The white smoke prevention operation is an operation of raising the temperature of the particulate matter removing device 10 by opening and closing the intake throttle 31 and the exhaust throttle 32, thereby raising the temperature of the oxidation catalyst 11 to the activation temperature. Here, if the intake throttle 31 and the exhaust throttle 32 are simultaneously closed at a low temperature without considering the temperature state in the particulate matter removing device 10, the amount of air supplied to the engine 20 decreases. The amount of fuel that is not completely burned increases. Therefore, the control device 50 adjusts the opening / closing speed of the intake throttle 31 and the exhaust throttle 32 and the opening / closing timing according to the temperature of the exhaust gas, and the temperature of the exhaust gas rises to the activation temperature of the oxidation catalyst 11. To control.

  First, when the control device 50 determines in step S23 that the temperature (Tdpf) of the exhaust gas on the outlet side of the acquired particulate matter removal device 10 (DPF 12) is equal to or higher than the first set temperature (S23-Yes). Will be described.

  In step S23, when it is determined that the temperature (Tdpf) of the exhaust gas on the outlet side of the acquired particulate matter removing device 10 (DPF 12) is equal to or higher than the first set temperature (S23-Yes), the control device 50 performs the exhaust. A target opening degree of the throttle 32 is obtained (S24). Here, the target opening of the exhaust throttle 32 refers to the opening / closing angle of the exhaust throttle 32 set by a map in accordance with the operating state (steady state, transient state) of the engine 20. Specifically, the target opening degree of the exhaust throttle 32 is obtained from a map of the exhaust throttle 32 set corresponding to the rotational speed or load of the engine 20.

  When the target opening of the exhaust throttle 32 is obtained (S24), the control device 50 obtains the opening / closing speed of the exhaust throttle 32 (S25). The opening / closing speed of the exhaust throttle 32 here is a speed at which the exhaust throttle 32 itself moves when the exhaust throttle 32 is opened / closed, and is determined according to the operating state (steady state, transient state) of the engine 20. Specifically, the opening / closing speed of the exhaust throttle 32 is set according to the rotational speed or load of the engine 20 in a steady state and the rotational speed or load of the engine 20 in a transient state.

  When the opening / closing speed of the exhaust throttle 32 is obtained (S25), the control device 50 instructs the exhaust throttle 32 by using the exhaust adjusting means 55 (S26) to adjust the exhaust throttle 32.

  On the other hand, when it is determined in step S23 that the exhaust gas temperature (Tdpf) on the outlet side of the acquired particulate matter removing device 10 (DPF 12) is equal to or higher than the first set temperature (S23-Yes), the control device 50 determines whether or not there is a signal to activate the intake throttle timer 57 at the same time as performing step S24 described above (S27).

  If it is determined in step S27 that there is no signal for operating the intake throttle timer 57 (S27-Yes), the control device 50 obtains the target opening of the intake throttle 31 (S28). If it is determined in step S27 that there is a signal for operating the intake throttle timer 57 (S27-No), the control device 50 releases the signal for operating the intake throttle timer 57 (S29). A target opening degree of the intake throttle 31 is obtained (S28). Here, the target opening of the intake throttle 31 refers to the opening / closing angle of the intake throttle 31 set by a map according to the operating state (steady state, transient state) of the engine 20. Specifically, the target opening degree of the intake throttle 31 is obtained from a map of the intake throttle 31 created from the rotation speed and load of the engine 20.

  In step S28, when the target opening of the intake throttle 31 is obtained, the control device 50 obtains the opening / closing speed of the intake throttle 31 (S30). The opening / closing speed of the intake throttle 31 here is a speed at which the intake throttle 31 itself moves when the intake throttle 31 is opened / closed, and is determined according to the operating state (steady state, transient state) of the engine 20. Specifically, the opening / closing speed of the intake throttle 31 is set corresponding to the rotational speed or load of the engine 20 in a steady state and the rotational speed or load of the engine 20 in a transient state.

  When the opening / closing speed of the intake throttle 31 is obtained (S30), the control device 50 instructs the intake throttle 31 by using the intake air adjusting means 54 (S31) to adjust the intake throttle 31.

  Thus, after the white smoke prevention operation is started, the temperature (Tdpf) of the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14 is equal to or higher than a preset first set temperature. Is determined (S23-Yes), the white smoke prevention operation is performed by simultaneously adjusting the intake throttle 31 and the exhaust throttle 32. By adjusting the intake throttle 31 and the exhaust throttle 32 at the same time, the flow rate of the exhaust gas flowing through the particulate matter removing device 10 is decreased, and thereby the temperature of the exhaust gas is increased. Then, the oxidation catalyst 11 is heated by the heated exhaust gas flowing through the particulate matter removing device 10.

  Next, when the control device 50 determines in step S23 that the temperature (Tdpf) of the exhaust gas on the outlet side of the acquired particulate matter removal device 10 (DPF 12) is not equal to or higher than the first set temperature (S23-No) ). In other words, when the temperature of the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) is lower than the first set temperature, the timing is shifted after the control for adjusting the exhaust throttle 32 is performed, and the intake throttle 31 is adjusted. Control to adjust.

  If it is determined in step S23 that the temperature (Tdpf) of the exhaust gas at the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14 is not equal to or higher than the first set temperature (S23-No), FIG. As shown, the control device 50 obtains the target opening degree of the exhaust throttle 32 (S41) and obtains the opening / closing speed of the exhaust throttle 32 (S42). At this time, the target opening is obtained from the map in the same manner as described above, and the opening / closing speed is obtained according to the operating state of the engine 20.

  When the target opening and opening / closing speed of the exhaust throttle 32 are obtained (S41, S42), the control device 50 instructs the exhaust throttle 32 by the exhaust adjusting means 55 (S43). 32 is adjusted. Thereafter, the control device 50 determines whether or not there is a signal for adjusting the intake throttle 31 (S44).

  If it is determined in step S44 that there is a signal for adjusting the intake throttle 31 (S44-Yes), the control device 50 obtains the target opening of the intake throttle 31 (S45) and determines the opening / closing speed of the intake throttle 31. Obtain (S46). At this time, the target opening is obtained from the map in the same manner as described above, and the opening / closing speed is obtained according to the operating state of the engine 20. When the target opening degree and opening / closing speed of the intake throttle 31 are obtained (S45, S46), the control device 50 instructs the intake throttle 31 by the intake adjusting means 54 (S47), and the exhaust throttle. 32 is adjusted.

  On the other hand, when it is determined in step S44 that there is no signal for adjusting the intake throttle 31 (S44-No), the control device 50 determines whether there is a signal for operating the intake throttle timer 57 (step S44). S48). First, the case where the control device 50 determines in step S48 that there is a signal for operating the intake throttle timer 57 (S48-Yes) will be described.

  In step S48, when it is determined that there is a signal to activate the intake throttle timer 57 (S48-Yes), the control device 50 is on the outlet side of the particulate matter removing device 10 (DPF 12) detected by the temperature sensor 14. The exhaust gas temperature (Tdpf) is acquired, and the acquired exhaust gas temperature (Tdpf) is compared with a second preset temperature, and the acquired exhaust gas temperature (Tdpf) is equal to or higher than the second preset temperature. It is determined whether or not (S49).

  When it is determined in step S49 that the exhaust gas temperature (Tdpf) on the outlet side of the acquired particulate matter removal apparatus 10 (DPF 12) is lower than the second set temperature (S49-No), the control device 50 A signal to adjust the throttle 31 is issued (S50). Further, when it is determined in step S49 that the exhaust gas temperature (Tdpf) on the outlet side of the acquired particulate matter removing device 10 (DPF 12) is equal to or higher than the second set temperature (S49-Yes), the oxidation catalyst 11 Since the temperature of the exhaust gas is higher than the activation temperature, the process returns to step S3 (FIG. 3).

  On the other hand, if it is determined in step S48 that there is a signal to activate the intake throttle timer 57 (S48-Yes), the control device 50 performs the above-described step S49 and at the same time the count by the intake throttle timer 57 is predetermined. It is determined whether or not the time has passed (S51). The predetermined time here refers to the time from the start of adjustment of the exhaust throttle 32 until the adjustment of the intake throttle 31 becomes necessary. This predetermined time is set because when the exhaust throttle 32 is adjusted, a load fluctuation occurs in the engine 20 and the intake throttle 31 must be adjusted accordingly.

  If it is determined in step S51 that the count of the intake throttle timer 57 has not exceeded the predetermined time (S51-No), the control device 50 continues to determine whether the count of the intake throttle timer 57 has passed the predetermined time or more. Is determined (S51). Further, when it is determined in step S51 that the count of the intake throttle timer 57 has exceeded a predetermined time (S51-Yes), the control device 50 cancels the signal for operating the intake throttle timer 57 (S52). ), A signal to adjust the intake throttle 31 is issued (S50).

  Thus, when it is determined in step S48 that there is a signal to activate the intake throttle timer 57 (S48-Yes), the control device 50 of the particulate matter removing device 10 (DPF 12) acquired by the temperature sensor 14 is used. It is determined whether or not the temperature (Tdpf) of the exhaust gas at the outlet side is equal to or higher than the second set temperature (S49), and at the same time, it is determined whether or not the count of the intake throttle timer 57 has exceeded a predetermined time ( S51). Then, the control device 50 determines that the temperature (Tdpf) of the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) is lower than the second set temperature (S49-No), and / or the intake throttle. When it is determined that the count of the timer 57 has exceeded a predetermined time (S51-Yes), a signal to adjust the intake throttle 31 is issued (S50).

  In step S50, when a signal to adjust the intake throttle 31 is issued, the control device 50 obtains the target opening of the intake throttle 31 (S45) and obtains the opening / closing speed of the intake throttle 31 (S46).

  When the target opening and opening / closing speed of the intake throttle 31 are obtained (S45, S46), the control device 50 instructs the intake throttle 31 by the intake adjusting means 54 (S47). 31 is adjusted.

  Next, the case where the control device 50 determines in step S48 that there is no signal to activate the intake throttle timer 57 (S48-No) will be described. In step S48, when it is determined that there is no signal for operating the intake throttle timer 57 (S48-No), the control device 50 resets the intake throttle timer 57 (S53), and activates the intake throttle timer 57. A signal is output (S54), and the intake throttle timer 57 starts counting (S55).

  When counting by the intake throttle timer 57 is started (S55), the control device 50 determines whether or not the count of the intake throttle timer 57 has exceeded a predetermined time (S51). When it is determined in step S51 that the count by the intake throttle timer 57 has not elapsed for a predetermined time (S51-No), the control device 50 continues to determine whether the count for the intake throttle timer 57 has elapsed for a predetermined time or more. Is determined (S51). In step S51, when it is determined that the count by the intake throttle timer 57 has exceeded a predetermined time (S51-Yes), the control device 50 cancels the signal to activate the intake throttle timer 57 (S52), A signal to adjust the intake throttle 31 is issued (S50).

  As described above, when it is determined in step S48 that there is no signal for operating the intake throttle timer 57 (S48-No), the control device 50 operates the intake throttle timer 57 and then counts the intake throttle timer 57. It is only determined whether or not a predetermined time has passed (S51). When it is determined that the count by the intake throttle timer 57 has exceeded a predetermined time (S51-Yes), a signal to adjust the intake throttle 31 is issued (S50).

  In step S50, when a signal to adjust the intake throttle 31 is issued, the control device 50 obtains the target opening of the intake throttle 31 (S45) and obtains the opening / closing speed of the intake throttle 31 (S46).

  When the target opening and opening / closing speed of the intake throttle 31 are obtained (S45, S46), the control device 50 instructs the intake throttle 31 by the intake adjusting means 54 (S47). 31 is adjusted.

  Thus, after the white smoke prevention operation is started, the temperature (Tdpf) of the exhaust gas on the outlet side of the particulate matter removing device 10 (DPF 12) acquired from the temperature sensor 14 is equal to or higher than a preset first set temperature. If it is determined that this is not the case (S23-No), first, by adjusting the exhaust throttle 32, the temperature of the exhaust gas at the outlet side of the particulate matter removal device 10 (DPF 12) (up to the activation temperature of the oxidation catalyst 11) ( The white smoke prevention operation is performed under the control of increasing Tdpf) and then adjusting the intake throttle 31.

  As described above, the exhaust gas purification system 100 includes the oxidation catalyst 11 and the DPF 12 in the exhaust passage 22 of the engine 20, and in the exhaust gas purification system 100 that purifies the exhaust gas of the engine 20, the outlet side of the DPF 12 Based on the detection result of the temperature sensor 14 (exit side temperature detecting means) disposed on the outlet side and the temperature sensor 14 (outlet side temperature detecting means), the temperature state of the exhaust gas on the outlet side of the DPF 12 is determined. Exhaust gas temperature determining means 51 for determining, and exhaust gas temperature adjusting means 52 for adjusting the temperature of the exhaust gas based on the determination result of the exhaust gas temperature determining means 51, and the exhaust gas temperature determining means 51 of the DPF 12 When it is determined that the temperature of the exhaust gas on the outlet side is less than a predetermined set value, the exhaust gas temperature adjusting means 52 causes the exhaust gas to It is to start the white smoke prevention operation raising the temperature to the activation temperature of the oxidation catalyst 11. With this configuration, it is possible to determine whether to perform control of the exhaust gas temperature adjusting means 52, that is, whether to perform the white smoke prevention operation, only with the exhaust gas temperature at the outlet side of the DPF 12, and thus the white smoke prevention operation is accurately performed. This can be done and fuel consumption can be suppressed.

  Further, the exhaust gas purification system 100 includes an exhaust gas temperature adjusting means 52, an intake air adjusting means 54 that adjusts the intake throttle 31 of the engine 20, and an exhaust gas adjusting means 55 that adjusts the exhaust throttle 32 of the engine 20. The intake adjustment means 54 can change the opening / closing speed of the intake throttle 31 according to the operating state of the engine 20, and the exhaust adjustment means 55 can change the opening / closing speed of the exhaust throttle 32 according to the operating state of the engine 20. To do. With this configuration, when the operating state of the engine 20 is in a steady state or a transient state, the opening / closing speed of the intake throttle 31 and / or the exhaust throttle 32 is changed according to the state, and the engine 20 in the steady state 20 rapid fluctuations can be suppressed, and generation of white smoke can be quickly reduced in a transient state.

  Further, the exhaust gas purification system 100 allows the intake air adjusting means 54 to change the timing for opening and closing the intake throttle 31 with respect to the opening and closing of the exhaust throttle 32 based on the determination result of the exhaust gas temperature determining means 51, thereby adjusting the exhaust gas. The means 55 can change the timing for opening and closing the exhaust throttle 32 relative to the opening and closing of the intake throttle 31 based on the determination result of the exhaust gas temperature determining means 51. With this configuration, the timing at which the other of the intake throttle 31 and the exhaust throttle 32 is opened or closed is determined depending on whether the temperature of the exhaust gas has reached the activation temperature or the set temperature of the oxidation catalyst 11. The amount of unburned fuel mixed in the exhaust gas can be adjusted to reduce white smoke emission.

  Furthermore, the exhaust gas purification system 100 includes a notification unit 60 that notifies that the white smoke prevention operation is started. By configuring in this way, the operator is notified by auditory or visual sense that the white smoke prevention operation is performed, so the operator can easily know that the white smoke prevention operation is performed. it can.

11 Oxidation catalyst 12 DPF
14 Temperature sensor (outlet side temperature detection means)
20 Engine 31 Intake throttle 32 Exhaust throttle 40 EGR device 42 EGR valve 51 Exhaust gas temperature judging means 52 Exhaust gas temperature adjusting means 54 Intake adjusting means 55 Exhaust adjusting means 60 Notifying means 100 Exhaust gas purification system

Claims (2)

In an exhaust gas purification system for providing an EGR device, an oxidation catalyst, and a particulate filter in an exhaust passage of an engine to purify the exhaust gas of the engine,
When unburned hydrocarbons and water vapor discharged before the oxidation catalyst reaches the activation temperature are adsorbed and accumulated on the surfaces of the oxidation catalyst and the particulate filter, and the exhaust gas flow rate increases in this state. , A control that automatically performs white smoke prevention operation to eliminate the adsorbed unburned hydrocarbon at once, and release it into the atmosphere as white smoke,
An outlet side temperature detecting means arranged on the outlet side of the particulate filter for detecting the temperature of the exhaust gas;
Exhaust gas temperature determining means for determining the temperature state of the exhaust gas on the outlet side of the particulate filter based on the detection result of the outlet side temperature detecting means;
Exhaust gas temperature adjusting means for adjusting the temperature of the exhaust gas based on the determination result of the exhaust gas temperature determining means,
When the exhaust gas temperature determining means determines that the exhaust gas temperature on the outlet side of the particulate filter is less than a predetermined set value, the exhaust gas temperature adjusting means increases the exhaust gas temperature to the activation temperature of the oxidation catalyst. Start the white smoke prevention operation to warm,
The exhaust gas temperature adjusting means includes an intake air adjusting means for adjusting the intake throttle of the engine, an exhaust gas adjusting means for adjusting the exhaust throttle of the engine, and an EGR adjusting means for adjusting the EGR valve of the engine,
The intake adjustment means can change the opening / closing speed and opening / closing timing of the intake throttle, and the exhaust adjustment means can change the opening / closing speed and opening / closing timing of the exhaust throttle,
When starting the white smoke prevention operation, the EGR adjusting means forcibly fully closes the EGR valve of the EGR device before the start . The exhaust gas purification system according to claim 1,
When the engine is in an operating state, the outlet side temperature detection means acquires the temperature of the exhaust gas on the outlet side of the particulate filter, determines whether there is a signal to perform white smoke prevention operation,
The exhaust gas temperature judgment means is
When it is determined that there is no signal indicating that the white smoke prevention operation is performed, the temperature of the exhaust gas at the outlet side of the particulate filter obtained from the outlet side temperature detecting means, and the first set temperature that is the temperature at which the activation of the oxidation catalyst begins. To determine whether the temperature of the exhaust gas is lower than the first set temperature,
When it is determined that there is a signal indicating that the white smoke prevention operation is performed, the temperature of the exhaust gas on the outlet side acquired by the outlet side temperature detecting means is higher than the first set temperature and the oxidation catalyst is sufficiently activated. An exhaust gas purification system characterized by comparing with a second set temperature, which is a temperature, to determine whether to start a white smoke prevention operation.

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