JP2017048744A - Exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system capable of promptly regenerating an oxidation catalyst even when it is deteriorated.SOLUTION: An exhaust emission control system 100 includes: a filter 42 provided in an exhaust passage 47 of an engine 22 to collect particulate matters in exhaust gas of the engine; an oxidation catalyst 41 provided upstream of the filter 42; a reducing agent supply section 49 for supplying a reducing agent to the oxidation catalyst 41; temperature sensors 43, 44 provided in the exhaust passage 47; a heating device 46 provided in the oxidation catalyst 41; a calculation section 71 for calculating a temperature rise rate of the engine exhaust gas in the oxidation catalyst 41 on the basis of detection values obtained by the temperature sensors 43, 44; a determination section 72 for determining whether or not the oxidation catalyst 41 has deteriorated by comparing the temperature rise rate with a threshold value; and a control section 70 for reducing the amount of the reducing agent supplied by the reducing agent supply section 49 and operating the heating device 46 when the determination section 72 determines that the oxidation catalyst 41 has deteriorated.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an engine exhaust purification system.

  In a work machine equipped with a diesel engine as a drive source, restrictions on the emission amount of particulate matter (hereinafter referred to as PM) contained in engine exhaust are strengthened together with NOx, CO, HC, and the like. Therefore, an exhaust purification system including a particulate filter (hereinafter referred to as DPF) that collects PM in engine exhaust has been proposed.

  In this type of exhaust purification system, when the amount of accumulated PM in the DPF increases, the DPF may become clogged and the air permeability may be gradually deteriorated, resulting in a decrease in engine performance. On the other hand, there is a method in which an oxidation catalyst is provided on the upstream side of the DPF, the fuel injected from the exhaust pipe injector is oxidized and burned by the oxidation catalyst, the temperature of the engine exhaust is raised, and PM deposited on the DPF is burned and removed (for example, See Patent Document 1).

JP 2012-127297 A

  Oxidation catalysts can degrade (poison) with repeated use. In such a case, the injected fuel cannot be sufficiently oxidized and burned by the oxidation catalyst, and the engine exhaust cannot be sufficiently heated. Then, there is a possibility that PM deposited on the DPF cannot be removed by combustion.

  Patent Document 1 determines whether or not the heat generation amount of an oxidation catalyst is appropriate, and increases or decreases the fuel injection amount according to the determination to prevent deterioration of the oxidation catalyst. It is difficult to regenerate the oxidation catalyst.

  The present invention has been made in view of the above circumstances, and it is determined whether or not the oxidation catalyst has deteriorated. When it is determined that the oxidation catalyst has deteriorated, the reducing agent supply amount is reduced and the heating device is reduced. It is an object of the present invention to provide an exhaust purification system capable of quickly regenerating an oxidation catalyst while suppressing the generation of surplus fuel by operating the engine.

  In order to achieve the above object, the present invention provides a filter provided in an exhaust passage of an engine for collecting particulate matter in engine exhaust, an oxidation catalyst provided on the upstream side of the filter, and the oxidation catalyst. Based on a detection value of the temperature sensor, a temperature sensor provided in the exhaust passage, a temperature sensor provided in the exhaust passage, a heating device for heating the oxidation catalyst, and a temperature detected by the temperature sensor. A calculation unit that calculates an increase rate, a determination unit that compares the temperature increase rate with a preset threshold value to determine whether or not the oxidation catalyst has deteriorated, and the determination unit that deteriorates the oxidation catalyst. And a control unit that operates the heating device while reducing the supply amount of the reducing agent by the reducing agent supply unit.

  According to the present invention, it is determined whether or not the oxidation catalyst is deteriorated, and when it is determined that the oxidation catalyst is deteriorated, the surplus is reduced by reducing the supply amount of the reducing agent and operating the heating device. It is possible to provide an exhaust purification system that can quickly regenerate an oxidation catalyst while suppressing the generation of fuel.

1 is a partially transparent side view of a work machine according to an embodiment of the present invention. 1 is a schematic view of an exhaust purification system according to an embodiment of the present invention. It is arrow sectional drawing by the arrow III-III line of FIG. It is the figure which looked at the heater which concerns on one Embodiment of this invention from the oxidation catalyst side. It is the schematic which shows the principal part of the control apparatus which concerns on one Embodiment of this invention. It is the figure which showed typically the concept of the deterioration judgment map of an oxidation catalyst. It is a figure which shows the purification performance of the oxidation catalyst which concerns on one Embodiment of this invention. It is the flowchart which showed the procedure for reproduction | regeneration of the oxidation catalyst by the control apparatus which concerns on one Embodiment of invention.

(Constitution)
1. Construction Machine FIG. 1 is a partially transparent side view of a work machine according to an embodiment of the present invention. As shown in FIG. 1, in this embodiment, a so-called hybrid hydraulic excavator will be described as an example of a work machine.

  As shown in FIG. 1, a hydraulic excavator 1 includes a traveling body 10, a revolving body 20 provided on the traveling body 10 so as to be capable of turning, and a shovel mechanism (front working machine) 30 provided on the revolving body 20 so as to be able to be raised and lowered. I have.

  The traveling body 10 is for causing the excavator 1 to travel by itself. The traveling body 10 includes a pair of left and right crawlers 11a and 11b and crawler frames 12a and 12b, a traveling hydraulic motors 13 and 14 that drive the left and right crawlers 11a and 11b, respectively, and a speed reducer (not used) of the traveling hydraulic motors 13 and 14. Etc.). As for the crawlers 11a and 11b and the crawler frames 12a and 12b, only the left one is shown in FIG.

  The revolving unit 20 is mounted on the upper portions of the crawler frames 12 a and 12 b via the revolving frame 21. The turning frame 21 is provided on the upper part of the crawler frames 12a and 12b via a turning wheel so as to be turnable around a vertical axis. Although not particularly illustrated, the turning wheel includes an inner wheel connected to the crawler frames 12a and 12b and an outer wheel connected to the turning frame 21, and the outer wheel is configured to turn with respect to the inner wheel. A turning electric motor (alternator) 25 and a turning hydraulic motor 27 are provided on the turning frame 21. The turning electric motor 25 is supported on the outer ring of the turning wheel together with the turning hydraulic motor 27, and the output shaft is engaged with the inner gear of the inner ring via the speed reducer 26. The turning hydraulic motor 27 is provided coaxially with the turning electric motor 25. The turning electric motor 25 is connected to a capacitor 24 that is a power storage device, and the turning electric motor 25 is driven by power supplied from the capacitor 24. With this configuration, the driving forces of the turning hydraulic motor 27 and the turning electric motor 25 are transmitted to the turning wheels via the speed reducer 26, and the turning body 20 turns together with the turning frame 21 with respect to the traveling body 10.

  The shovel mechanism 30 is a multi-joint structure front working machine including a boom 31, an arm 33, and a bucket 35. The boom 31 is connected to the revolving frame 21 of the revolving structure 20 with a pin or the like so as to be able to move up and down. The arm 33 is connected to the tip of the boom 31 by a pin or the like so as to be rotatable in the front-rear direction. The bucket 35 is pivotally connected to the tip of the arm 33 with a pin or the like. The boom 31, the arm 33, and the bucket 35 are driven by a boom cylinder 32, an arm cylinder 34, and a bucket cylinder 36, respectively. The boom cylinder 32, the arm cylinder 34, and the bucket cylinder 36 are hydraulic cylinders.

  A drive system for driving various actuators is mounted on the revolving frame 21 described above. The drive system includes a hydraulic system 40 that drives the hydraulic actuator, and an electric system that drives the electric actuator. The hydraulic system 40 drives the above-described traveling hydraulic motors 13 and 14, the turning hydraulic motor 27, the boom cylinder 32, the arm cylinder 34, the bucket cylinder 36, and the like. The electric system drives the assist power generation motor 23, the turning electric motor 25, and the like.

2. FIG. 2 is a schematic view of an exhaust purification system according to the present embodiment. In this embodiment, the case where an exhaust gas purification system is applied to the hydraulic excavator 1 (see FIG. 1) is illustrated.

  As shown in FIG. 2, the exhaust purification system 100 includes an oxidation catalyst 41, a DPF 42, temperature sensors 43 and 44, a differential pressure sensor 45, a heater 46, a current supply unit 60, and a control device 70. The exhaust purification system 100 includes an SCR catalyst, a post-stage oxidation catalyst, a silencer, and the like in addition to the components described above, but is omitted in FIG.

  A DPF (Diesel Particulate Filter) 42 is arranged in the middle of the exhaust passage 47 of the engine 22. The DPF 42 is a filter for collecting PM in the engine exhaust 48 flowing through the exhaust passage 47.

  The oxidation catalyst 41 is accommodated in a catalyst container (not shown) or the like, and is disposed in the middle of the exhaust passage 47 so as to be positioned upstream of the DPF 42 in the flow direction of the engine exhaust 48. As the oxidation catalyst 41, for example, a catalyst in which a catalyst component in which at least one kind of noble metal such as platinum, palladium, rhodium or the like is supported on titania, zirconia, alumina or the like is supported on a cordierite honeycomb structure or the like is suitable. However, any catalyst that can oxidize nitric oxide (NO), carbon monoxide (CO), hydrocarbon (HC), etc. in the engine exhaust 48 may be used.

The oxidation catalyst 41 oxidizes a part of NO in the engine exhaust 48 and converts it into nitrogen dioxide (NO ₂ ). Therefore, as described above, by arranging the oxidation catalyst 41 on the upstream side of the DPF 42, the PM collected and deposited by the DPF 42 is supplied from the oxidation catalyst 41 at a relatively low temperature (for example, 350 ° C.). It is oxidized by reaction with NO _2.

  Further, the oxidation catalyst 41 oxidizes HC (unburned fuel), CO, or the like when the engine exhaust 48 is present. In this embodiment, after injecting fuel into the engine cylinder from the injector 49 of the engine 22 (main injection), the fuel is again injected into the engine cylinder from the injector 49 (post injection). At this time, if the post injection timing is significantly delayed with respect to the main injection, the fuel injected from the injector 49 is not burned in the engine cylinder, but is discharged into the exhaust passage 47 as a large amount of unburned fuel. The unburned fuel discharged to the exhaust passage 47 is oxidized by the oxidation catalyst 41 as described above. Then, oxidation heat is generated in the oxidation catalyst 41 and the engine exhaust 48 is heated. Then, the engine exhaust 48 that has been heated raises the temperature of the SCR catalyst that is disposed downstream of the oxidation catalyst 41 in the flow direction of the engine exhaust 48. Thus, in the present embodiment, the injector 49 of the engine 22 functions as a reducing agent supply unit that supplies a reducing agent (fuel) to the oxidation catalyst 41, and the reducing agent is supplied from the injector 49 to the oxidation catalyst 41 by post injection. . In addition, engine oil is lubricated to sliding parts such as a piston, a crankshaft, and a connecting rod of the engine 22 by an engine oil lubrication mechanism (not shown).

  3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 is a view of the heater 46 according to the present embodiment as viewed from the oxidation catalyst 41 side.

  As shown in FIG. 3, the oxidation catalyst 41 is supported on a catalyst carrier 50, and this catalyst carrier 50 is supported by a support material 51 and a casing 52.

  The catalyst carrier 50 carries a catalyst component. The support material 51 and the casing 52 are cylindrical members. The casing 52 covers the outer periphery of the support material 51, and the support material 51 covers the outer periphery of the catalyst carrier 50. The casing 52 is made of metal.

  The heater (heating device) 46 includes brackets 53 and 54, outer casings 55 and 56, heating units 57 and 58, and heat insulating materials 59 and 61. The heater 46 is detachably attached to the catalyst container including the oxidation catalyst 41.

  The outer casings 55 and 56 are metal members, and are formed in a cylindrical shape in a state of being attached to the oxidation catalyst 41 so as to cover the periphery of the casing 52. The outer casings 55 and 56 are provided with brackets 53 and 54 at opposing ends (see FIG. 4), and the brackets 53 and 54 are fastened by bolts 53A, 53B, 54A and 54B with the oxidation catalyst 41 interposed therebetween. By doing so, it is attached to the oxidation catalyst 41.

  The heating units 57 and 58 are provided on the inner peripheral surfaces of the outer casings 55 and 56 so as to face the casing 52 in a state where the heater 46 is mounted on the oxidation catalyst 41. The heating portions 57 and 58 of the present embodiment are heating wires (such as nichrome wires) and meander along the inner peripheral surfaces so as to cover the inner peripheral surfaces of the outer casings 55 and 56 as a whole ( (See FIG. 4). The heat insulating materials 59 and 61 are interposed between the heating portions 57 and 58 and the outer casings 55 and 56, so that heat radiation through the outer casings 55 and 56 is suppressed. In the present embodiment, the surfaces of the heat insulating materials 59 and 61 are brought into contact with the heating portions 57 and 58, and the heating portions 57 and 58 are supported by the heat insulating materials 59 and 61. As the heat insulating materials 59 and 61, an alumina-silicate ceramic fiber, an alumina fiber, a zirconia fiber, a silica fiber, an inorganic fiber such as rock wool and asbestos, an organic fiber such as nylon and kepler, a foamed product such as urethane, or A combination of these can be used.

  As shown in FIG. 2, the capacitor 24 and the turning electric motor 25 are connected to the heater 46 through the current supply unit 60. In the present embodiment, the current supply unit 60 uses electric power obtained by regeneration by the electric motor 25 for turning, electric power stored in the capacitor 24, and the like as a power source for the heater 46.

  The current supply unit 60 includes a relay switch 64 and a coil 65. The relay switch 64 is configured to be switchable between an ON position (connection position) and an OFF position (cutoff position). In the present embodiment, when no current (command signal from the control device 70) flows through the coil 65, the relay switch 64 is in the OFF position, and no current is supplied to the heater 46. On the other hand, when a current flows through the coil 65, the relay switch 64 is switched from the OFF position to the ON position and the current is supplied to the heater 46, and the oxidation catalyst 41 is heated by the heater 46.

  As shown in FIG. 2, the temperature sensor (upstream exhaust temperature sensor) 43 is exhausted so as to be positioned upstream of the oxidation catalyst 41 in the flow direction of the engine exhaust 48 (between the engine 22 and the oxidation catalyst 41). It is provided in the middle of the passage 47. The temperature sensor (downstream exhaust temperature sensor) 44 is provided in the middle of the exhaust passage 47 so as to be located downstream of the oxidation catalyst 41 in the flow direction of the engine exhaust 48 (between the oxidation catalyst 41 and the DPF 42). Yes.

  The differential pressure sensor 45 is for detecting the differential pressure across the DPF 42, and includes an upstream pressure sensor 45A and a downstream pressure sensor 45B. The upstream pressure sensor 45A is provided in the middle of the exhaust passage 47 so as to be positioned upstream of the DPF 42 in the flow direction of the engine exhaust 48 (between the oxidation catalyst 41 and the DPF 42). The downstream pressure sensor 45B is provided in the middle of the exhaust passage 47 so as to be located downstream of the DPF 42 in the flow direction of the engine exhaust 48.

  A control device (ECU (Engine Control Unit 1)) 70 includes a CPU and the like, for example, controls the rotational speed and torque of the engine 22 or clogs the DPF 42 based on the differential pressure detected by the differential pressure sensor 45. It has a function of determining the condition and determining whether or not the DPF 42 needs to be regenerated.

  As shown in FIG. 2, detection signals from the temperature sensors 43 and 44 and the differential pressure sensor 45 are input to the control device 70. That is, the control device 70 is electrically connected to the temperature sensors 43 and 44 and the differential pressure sensor 45. The control device 70 inputs the upstream and downstream engine exhaust 48 temperatures of the oxidation catalyst 41 detected by the temperature sensors 43 and 44, and the upstream and downstream differential pressures detected by the differential pressure sensor 45. To do. The control device 70 also outputs (command) signals to various devices such as the intake control valve 55, the EGR valve 56, and the injector 49 of the engine 22.

  FIG. 5 is a schematic diagram illustrating a main part of the control device 70. As illustrated in FIG. 5, the control device 70 includes a calculation unit 71, a determination unit 72, a storage unit 73, and a control unit 74.

  The calculation unit 71 has a function of inputting detection values of the temperature sensors 43 and 44 and calculating a temperature increase rate ΔTd of the engine exhaust 48 in the oxidation catalyst 41 based on the input detection values. The temperature increase rate ΔTd is the temperature increase amount of the engine exhaust 48 per unit time (set time).

  The determination unit 72 is connected to the calculation unit 71. The determination unit 72 compares the temperature increase rate ΔTd calculated by the calculation unit 71 with a preset threshold value (set value) ΔTs to determine whether or not the oxidation catalyst 41 has deteriorated, and the oxidation catalyst 41 has deteriorated. If it is, it has a function of specifying the degree of deterioration and outputting a signal corresponding to the degree of deterioration. This will be described in detail below.

  FIG. 6 is a diagram schematically illustrating the concept of a deterioration determination map of the oxidation catalyst 41. In FIG. 6, the vertical axis represents the temperature rise amount, the horizontal axis represents time, line A represents a new article, line B represents the deterioration degree “1”, and line C represents the temperature increase rate of the oxidation catalyst having the deterioration degree “2”. Yes. In this embodiment, it is assumed that the oxidation catalyst having the deterioration degree “2” is deteriorated more than the oxidation catalyst having the deterioration degree “1”. The deterioration determination map illustrated in FIG. 6 is stored in the storage unit 73, for example.

  As shown in FIG. 6, the rate of temperature increase of the oxidation catalyst 41 varies depending on the degree of deterioration. As the degree of deterioration of the oxidation catalyst 41 increases, the rate of temperature increase decreases even under the same reducing agent supply amount. Based on the deterioration determination map of the oxidation catalyst 41, the determination unit 72 is deteriorated when the temperature increase rate ΔTd of the oxidation catalyst 41 input from the calculation unit 71 is equal to or less than the threshold value ΔTs (when the inclination is small). And has a function of specifying the degree of deterioration. In the case of FIG. 6, assuming that the threshold value of the temperature increase rate is ΔTst, the temperature increase rate ΔTdA shown by the line A is higher than the threshold value ΔTst (the inclination is large), and the temperature increase rates ΔTdB and ΔTdC shown by the lines B and C are from the threshold value ΔTst. It is on the lower side (the inclination is small). If the temperature increase rate calculated by the calculation unit 71 is ΔTdB, the determination unit 72 determines that the oxidation catalyst 41 has deteriorated and specifies the deterioration degree as “1”. Note that the deterioration degree “1”, the deterioration degree “2”, and the like are examples of expressions indicating the deterioration degree of the oxidation catalyst 41.

  As shown in FIG. 5, the control unit 74 includes a reducing agent supply amount control unit 75 and a heating control unit 76.

  The reducing agent supply amount control unit 75 is connected to the reducing agent supply unit 49. The reducing agent supply amount control unit 75 receives a signal from the determination unit 72, and from the table indicating the relationship between the degree of deterioration of the oxidation catalyst 41 and the reduction amount of the reducing agent supply amount from the reducing agent supply unit 49, the oxidation catalyst. 41 has a function of reducing the amount of reducing agent supplied from the reducing agent supply unit 49 in accordance with the degree of deterioration of 41. Since the reduction amount of the reducing agent is determined by the degree of deterioration of the oxidation catalyst 41, if the degree of deterioration of the oxidation catalyst 41 is large, the reduction amount of the reducing agent increases accordingly. A table indicating the relationship between the degree of deterioration of the oxidation catalyst 41 and the reduction amount of the reducing agent supply amount from the reducing agent supply unit 49 is stored in the storage unit 73, for example.

  The heating control unit 76 is connected to the current supply unit 60. The heating control unit 76 has a function of acquiring a heat amount (supplied heat amount) corresponding to a decrease in the generated heat amount in the oxidation catalyst 41 due to a decrease in the reducing agent supply amount from the reducing agent supply unit 49. In the present embodiment, the heating control unit 76 inputs a reduction amount of the reducing agent supply amount from the reducing agent supply unit 49, and determines the relationship between the reduction amount of the reducing agent supply amount from the reducing agent supply unit 49 and the supply heat amount. The amount of heat supplied to the oxidation catalyst 41 is acquired from the table shown. In addition, the table which shows the relationship between the reduction | decrease amount of the reducing agent supply amount from the reducing agent supply part 49, and supply heat amount is memorize | stored in the memory | storage part 73, for example. Further, a table showing the relationship between the degree of deterioration of the oxidation catalyst 41 and the reduction amount of the reducing agent supply amount from the reducing agent supply unit 49, and the reduction amount of the reducing agent supply amount from the reducing agent supply unit 49 and the supply heat amount The table indicating the relationship may be a different table, but may be a table in which the reduction amount of the reducing agent supply amount and the supply heat amount are associated with the degree of deterioration of the oxidation catalyst 41.

  Here, a method for calculating the amount of heat supplied to the heater 46 will be described.

  FIG. 7 is a diagram showing the purification performance of the oxidation catalyst 41. FIG. 7 illustrates the purification performance of the oxidation catalyst 41 with respect to HC. The vertical axis represents the HC purification rate, the horizontal axis represents the exhaust temperature, the line D represents a new article, and the line E represents a deteriorated oxidation catalyst.

  As shown in FIG. 7, when the oxidation catalyst 41 deteriorates, the HC purification performance shifts to the high temperature side (shifts from line D to line E). That is, when the oxidation catalyst 41 is deteriorated, a higher exhaust temperature is required to obtain the same purification rate as the HC purification rate when the oxidation catalyst 41 is new. The amount of heat supplied to the heater 46 is obtained by calculating the amount of heat corresponding to the shift to the high temperature side. The calculated amount of heat is equal to a decrease in the amount of heat generated in the oxidation catalyst 41 due to a decrease in the amount of reducing agent supplied from the reducing agent supply unit 45.

  In addition to the above-described function, the heating control unit 76 supplies current to the coil 65 to operate the current supply unit 60 so that the supply heat amount acquired from the storage unit 73 is supplied to the oxidation catalyst 41, and supplies current to the heater 46. It has the function to supply.

  In the present embodiment, the heating control unit 76 controls the time (energization time) for maintaining the relay switch 64 at the ON position. Specifically, the heating control unit 76 acquires the energization time from a table indicating the relationship between the supplied heat amount and the time for supplying current to the coil 65. A table showing the relationship between the amount of heat supplied and the time for supplying current to the coil 65 is stored in the storage unit 73, for example. As the magnitude (current value) of the current supplied to the heater 46, for example, a target current value (target current value) is set. In the initial stage, the current value exceeds the target current value, and then the target current value. It is good to make it gradually approach. In addition, it is good also as a structure which controls directly the electric current or voltage supplied to the heater 46, for example not only the structure which controls the time which maintains the relay switch 64 in an ON position.

(Operation)
FIG. 8 is a flowchart showing a procedure for regenerating the oxidation catalyst 41 by the control device 70 according to the present embodiment.

  When the engine 22 of the hydraulic excavator 1 is started, the control device 70 changes the operation region of the engine 22 to the active region of the oxidation catalyst 41 based on whether the exhaust temperature Tn detected by the temperature sensor 43 is equal to or higher than the set temperature Te. It is determined whether or not there is (step S1). If the exhaust temperature Tn is equal to or higher than the set temperature Te (Yes), the control device 70 moves the procedure from step S1 to step S2. On the other hand, when the exhaust temperature Tn is lower than the set temperature Te (No), the control device 70 repeats step S1 until the exhaust temperature Tn becomes equal to or higher than the set temperature Te.

  In step S1, when it is determined that the exhaust temperature Tn is equal to or higher than the set temperature Te, post-injection is started by the reducing agent supply unit 49, and unburned fuel is supplied to the oxidation catalyst 41 (step S2).

  Subsequently, the calculating unit 71 inputs the exhaust temperatures of the inlet and outlet of the oxidation catalyst 41 detected by the temperature sensors 43 and 44, and calculates the temperature increase rate ΔTd of the exhaust temperature based on the equation (1) (step S3). .

ΔTd = (exhaust temperature at the inlet−exhaust temperature at the outlet) / time (1)
Thereafter, the determination unit 72 inputs the temperature increase rate ΔTd from the calculation unit 71 and compares it with the threshold value ΔTs to determine whether or not the oxidation catalyst 41 has deteriorated (step S4). When the temperature increase rate ΔTd is less than the threshold value ΔTs (ΔTd <ΔTs) (Yes), the determination unit 72 determines that the oxidation catalyst 41 has deteriorated and moves the procedure to step S5. Conversely, when the temperature increase rate ΔTd is near the threshold ΔTs (ΔTd = ΔTs) (No), the determination unit 72 determines that the oxidation catalyst 41 has not deteriorated (normal), and the temperature increase rate ΔTd is less than the threshold ΔTs. Step S4 is repeated until.

  When it is determined in step S4 that the oxidation catalyst 41 has deteriorated, the reducing agent supply amount control unit 75 decreases the reducing agent supply amount from the reducing agent supply unit (injector) 49 (step S5).

  Subsequently, the heating control unit 76 acquires the amount of heat supplied from the heater 46 to the oxidation catalyst 41 (step S6), operates the current supply unit 60, and supplies the acquired amount of supplied heat to the oxidation catalyst 41. A current is supplied to the heater 46 (step S7).

  Subsequently, the control device 70 inputs the detection value of the temperature sensor 43, and determines whether or not the exhaust temperature Tg on the upstream side of the oxidation catalyst 41 is equal to or higher than the target temperature Tgs (step S8). If the exhaust temperature Tg is equal to or higher than the target temperature Tgs (Tg ≧ Tgs) (Yes), the control device 70 moves the procedure to Step S9. Conversely, when the exhaust temperature Tg is less than the target temperature Tgs (Tg <Tgs) (No), the control device 70 repeats step S7 until the exhaust temperature Tg becomes equal to or higher than the target temperature Tgs. The target temperature Tgs is a temperature necessary to regenerate the deterioration of the oxidation catalyst 41, and is, for example, a temperature (600 ° C.) at which sulfur is desorbed from the catalyst.

  When the exhaust temperature Tg is equal to or higher than the target temperature Tgs in step S8, the temperature of the oxidation catalyst 41 rises due to the temperature rise of the engine exhaust 48, and catalyst regeneration of the oxidation catalyst 41 is started (step S9).

  Subsequently, the control device 70 determines whether or not an elapsed time tim from the start of catalyst regeneration of the oxidation catalyst 41 is equal to or longer than the set time t1 (step S10). When the elapsed time tim is equal to or longer than the set time t1 (tim ≧ t1) (Yes), the control device 70 moves the procedure to step S11. Conversely, if the elapsed time tim is less than the set time t1 (tim <t1) (No), the control device 70 repeats step S9 until the elapsed time tim becomes equal to or greater than the set time t1.

  When the elapsed time tim is equal to or longer than the set time t1 in step S10, the control device 70 stops the post-injection of the reducing agent supply from the reducing agent supply unit 49 and stops the energization of the heater 46, thereby oxidizing the oxidation catalyst 41. Is finished (step S11).

  The control device 70 repeats the above-described procedure (steps S1 to S11) while the excavator 1 is operating.

(effect)
(1) In this embodiment, when it is determined that the oxidation catalyst 41 has deteriorated, the amount of reducing agent supplied by the reducing agent supply unit 49 is decreased, and the heater 46 is operated to heat the oxidation catalyst 41. ing. Therefore, even when the oxidation catalyst 41 is deteriorated, the temperature of the exhaust 48 can be raised and the oxidation catalyst 41 can be quickly regenerated.

  (2) In this embodiment, the reducing agent supply amount from the reducing agent supply unit 49 is decreased according to the degree of deterioration of the oxidation catalyst 41. Therefore, an amount of fuel suitable for the oxidation performance of the oxidation catalyst 41 can be supplied to the oxidation catalyst 41, and the occurrence of excess fuel (fuel that is not oxidized in the oxidation catalyst 41) can be suppressed. Therefore, it is possible to avoid that excess fuel flows down (slips) downstream of the oxidation catalyst 41.

  (3) In the present embodiment, a current is supplied to the heater 46 so as to supply the oxidation catalyst 41 with an amount of heat corresponding to a decrease in the amount of heat generated in the oxidation catalyst 41 due to a decrease in the amount of reducing agent supplied from the reducing agent supply unit 49. Supply. Therefore, it is possible to avoid supplying more current than necessary to the heater 46, and it is possible to avoid an excessive load on the capacitor 24, the electric motor 25 for turning, and the like.

  (4) In this embodiment, the heater 46 is detachably provided on the catalyst container including the oxidation catalyst 41. Therefore, when a malfunction such as disconnection occurs in the heater 46, the heater 46 can be easily replaced, and the maintainability of the exhaust purification system 100 can be improved.

  (5) In the present embodiment, the exhaust purification system 100 is provided in the hybrid hydraulic excavator 1. Generally, in a hybrid hydraulic excavator, the turning energy when the turning body 20 is decelerated can be recovered and generated by the turning electric motor 25. Therefore, current can be supplied to the heater 46 using the electric power obtained by the power generation in the turning electric motor 25, so that the oxidation catalyst 41 can be heated more efficiently.

(Other)
The present invention is not limited to the embodiments described above, and includes various modifications. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. For example, a part of the configuration of the above-described embodiment can be deleted and replaced.

  In the above-described embodiment, the configuration in which the reducing agent is supplied to the oxidation catalyst 41 by post injection is exemplified. However, the essential effect of the present invention is to provide an exhaust purification system that can be quickly regenerated even when the oxidation catalyst is deteriorated, and is not necessarily limited to this configuration as long as this essential effect is obtained. . For example, an exhaust pipe injector may be separately provided on the upstream side of the oxidation catalyst 41, and the reducing agent may be supplied to the oxidation catalyst 41 by so-called exhaust pipe injection in which unburned fuel is injected from the exhaust pipe injector.

  Further, in the above-described embodiment, when it is determined that the oxidation catalyst 41 has deteriorated, the deterioration degree is specified, the reducing agent supply amount is reduced according to the deterioration degree, and the generated heat amount due to the reduction of the reducing agent supply amount is reduced. The structure which supplies the calorie | heat amount equivalent to a reduced part to the oxidation catalyst 41 was illustrated. However, as long as the essential effects of the present invention described above are obtained, the present invention is not necessarily limited to this configuration. For example, when it is determined that the oxidation catalyst 41 has deteriorated, the reducing agent supply amount may be decreased to a constant supply amount, and a constant amount of heat may be supplied to the oxidation catalyst 41.

  Further, in the above-described embodiment, the case where the heating parts 57 and 58 are formed in a meandering shape that meanders along a surface along the flow direction of the engine exhaust 48 is exemplified, but as long as the oxidation catalyst 41 can be heated, The shape of the heating parts 57 and 58 is not limited. Moreover, although the structure which heats the oxidation catalyst 41 with the heater 46 was illustrated, as long as the oxidation catalyst 41 can be heated, it is not limited to the heater 46. For example, a burner or the like may be used instead of the heater 46. Further, although the configuration including the capacitor 24 as the power storage device is illustrated, a configuration including a battery or the like instead of the capacitor 24 may be used. Further, the case where the capacitor 24 and the electric motor 25 for turning are used as the power source for the heater 46 has been described as an example. However, for example, when the present invention is applied to a normal construction machine that is not a hybrid, a power source is separately prepared. May be.

  22: Engine, 41: Oxidation catalyst, 42: DPF (filter), 43: Upstream exhaust temperature sensor (temperature sensor), 44: Downstream exhaust temperature sensor (temperature sensor), 46: Heater (heating device), 47: Exhaust passage, 48: engine exhaust, 49: reducing agent supply unit, 60: current supply unit, 71: calculation unit, 72: determination unit, 73: storage unit, 74: control unit, 75: reducing agent supply amount control unit, 76: heating control unit, 100: exhaust purification system

Claims (5)

A filter provided in the exhaust passage of the engine for collecting particulate matter in the engine exhaust;
An oxidation catalyst provided upstream of the filter;
A reducing agent supply unit for supplying a reducing agent to the oxidation catalyst;
A temperature sensor provided in the exhaust passage;
A heating device for heating the oxidation catalyst;
A calculation unit that calculates a temperature increase rate of the engine exhaust in the oxidation catalyst based on a detection value of the temperature sensor;
A determination unit that compares the rate of temperature increase with a preset threshold and determines whether or not the oxidation catalyst has deteriorated;
A controller that reduces a supply amount of the reducing agent by the reducing agent supply unit and operates the heating device when the determination unit determines that the oxidation catalyst is deteriorated. Exhaust purification system. The exhaust purification system according to claim 1,
The control unit includes a reducing agent supply amount control unit that is connected to the reducing agent supply unit and reduces a reducing agent supply amount from the reducing agent supply unit according to a degree of deterioration of the oxidation catalyst. Exhaust purification system. The exhaust purification system according to claim 2,
The controller controls the heating device to operate the heating device so as to supply the oxidation catalyst with a heat amount corresponding to a decrease in the amount of heat generated in the oxidation catalyst due to a decrease in the reducing agent supply amount from the reducing agent supply unit. An exhaust purification system comprising a section. The exhaust purification system according to claim 3,
A storage unit storing a relationship between a reduction amount of the reducing agent supply amount from the reducing agent supply unit and a heat amount supplied to the oxidation catalyst;
The exhaust purification system, wherein the heating control unit acquires the heat amount from the storage unit based on a reduction amount of a reducing agent supply amount from the reducing agent supply unit. The exhaust purification system according to claim 1,
The exhaust gas purification system, wherein the heating device is detachably attached to a catalyst container containing the oxidation catalyst.

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