JP2012145056A - Exhaust gas purification system for working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purification system for a working machine, which provides a forced generation free from an effect of rapid change of a vehicle body.SOLUTION: Disclosed is the exhaust gas purification system for the working machine. The system is provided with: a filter 20 for capturing PM contained in exhaust gas from an engine 10; a differential pressure sensor 21 for detecting a differential pressure between the upstream and downstream sides of the filter 20; and a controller 22 having a regeneration determination unit 22a for determining whether the forced generation is now needed. The controller 22 includes a change determination unit 22b for determining whether a state quantity relevant to an operation of the engine 10, for example, whether the number N of engine revolutions is rapidly changed. When it is determined by the change determination unit 22b that the number N of engine revolutions is rapidly changed, a determination by the regeneration determination unit 22a is canceled for a predetermined time T in which an effect of rapid change of the number N of engine revolutions is considered to be negligible.

Description

  The present invention is provided in a work machine such as a hydraulic excavator, and purifies exhaust gas of a work machine provided with a filter that removes particulate matter (Particulate Matter: hereinafter referred to as “PM”) contained in engine exhaust. Relates to the device.

  There exists a thing shown by patent document 1 as this type of prior art. This prior art includes a filter that collects PM contained in the exhaust of the engine downstream of the exhaust, an exhaust temperature detector, and a differential pressure detector that detects a differential pressure between the upstream and downstream of the exhaust of the filter. ing. Further, forced regeneration for burning PM collected in the filter is required by comparing the calculation unit for calculating the exhaust flow rate with the differential pressure detected by the differential pressure detector and the determination differential pressure that is a determination threshold. A controller having a regeneration determination unit for determining whether the time has come;

  In the prior art having such a configuration, the detected differential pressure ΔP detected by the differential pressure detector is determined as the reference temperature from the relationship between the exhaust temperature detected by the exhaust temperature detector and the reference temperature of the exhaust. The difference between the pressure difference ΔP1 obtained by converting to the value of the value and the determination pressure difference ΔP2 that is a threshold value at the reference temperature corresponding to the exhaust flow rate calculated by the calculation unit of the controller is compared by the regeneration determination unit of the controller. , ΔP1> ΔP2, it is determined that forced regeneration is necessary.

  In forced regeneration, fuel is injected into the exhaust of an engine, the exhaust temperature is raised using an oxidation reaction by an oxidation catalyst, PM accumulated on the filter is burned and removed, and this clogs the filter. Can be eliminated.

JP 2005-307878 A

  By the way, in the above-described conventional exhaust purification device, if the vehicle is a vehicle such as a truck with abrupt fuel injection amount fluctuation or intake air quantity fluctuation, the exhaust flow rate at that time is stable, and the above-described determination differential pressure ΔP2 is Appropriate values can be calculated. However, in a working machine such as a hydraulic excavator that is a subject of the present invention, there are many sudden fluctuations in the vehicle body such as load fluctuations and rotation fluctuations, and the exhaust flow rate calculated at that time also fluctuates greatly. For this reason, it may happen that an appropriate determination differential pressure ΔP2 cannot be calculated. Therefore, when the prior art is applied to a work machine, when the determination is made by the regeneration determination unit of the controller using the determination differential pressure ΔP2, even if the PM is not actually deposited so much on the filter, It is determined that ΔP1> ΔP2, and there is a possibility that forced regeneration is performed even though it is not necessary. Such unnecessary forced regeneration causes useless fuel injection and deteriorates fuel consumption.

  The present invention has been made from the above-described prior art, and an object of the present invention is to provide an exhaust purification device for a work machine that can realize forced regeneration without the influence of sudden fluctuations in the vehicle body.

  In order to achieve this object, the present invention is provided in a work machine, a vehicle main body to which the work device is attached, and a work machine provided with the engine for driving the work device. A filter that collects particulate matter contained in the exhaust of the engine downstream of the exhaust, a differential pressure detector that detects the differential pressure between the upstream and downstream of the filter, and the differential pressure detector A controller having a regeneration determination unit that determines whether or not forced regeneration for burning the particulate matter collected by the filter has been reached by comparing the differential pressure with a determination differential pressure that is a determination threshold; In the exhaust emission control device for a work machine having the above, the controller has a variation determination unit that determines whether or not a state quantity related to the operation of the engine has suddenly changed. When the variation determination unit determines that the state quantity has suddenly changed, a process for invalidating the determination by the regeneration determination unit for a predetermined time when it is considered that the influence of the state quantity is reduced is performed. It consists of things.

  The present invention has been made by paying attention to the fact that state variables such as the engine speed and the fuel injection amount, which are related to the operation of the engine, suddenly change when the vehicle body suddenly changes. In the present invention, when it is determined by the fluctuation determination unit of the controller that the state quantity related to the operation of the engine has suddenly changed according to the sudden change of the vehicle body, the determination by the determination reproduction unit determines whether to perform forced regeneration. A process of invalidating by the controller, that is, a process of stopping the determination function of the reproduction determination unit is performed for a predetermined time when it is considered that the influence of the sudden fluctuation of the state quantity is reduced. The predetermined time described above is set experimentally or empirically in consideration of load fluctuation that may occur in the corresponding working machine. As a result, the present invention can realize forced regeneration that eliminates the influence of sudden fluctuations in the vehicle body. That is, unnecessary forced regeneration can be suppressed.

  According to the present invention, in the above invention, the controller includes a first calculation unit that calculates an exhaust flow rate, an exhaust flow rate calculated by the first calculation unit, an exhaust flow rate that is preset in the controller, and a determination differential pressure. And a second calculation unit that calculates the determination differential pressure based on a map showing the relationship between

  According to the present invention, in the above invention, a fuel control unit is provided that controls an injection amount of fuel supplied to the engine, and the controller includes a fuel injection amount instruction unit that outputs a control signal for controlling the fuel control unit. An intake air amount detector for detecting an intake air amount supplied to the engine and outputting a detection signal to the controller; an intake air temperature detector for detecting a temperature of the intake air and outputting a detection signal to the controller; An exhaust temperature detector that detects an exhaust gas temperature of the engine and outputs a detection signal to the controller, the controller configured to preset the intake air temperature detected by the intake air temperature detector and the controller Based on the intake air density determined according to the map showing the relationship between the intake air temperature and the intake air density, and the intake air amount detected by the intake air amount detector, An intake weight calculation unit that calculates the exhaust weight based on the intake weight calculated by the intake weight calculation unit and the fuel injection amount specified by the fuel injection amount instruction unit. The controller includes the exhaust gas temperature detected by the exhaust gas temperature detector, and a map indicating a relationship between a plurality of exhaust gas temperatures and a plurality of exhaust gas densities preset in the controller. A process for calculating the exhaust flow rate is performed based on the exhaust density determined accordingly and the exhaust weight calculated by the exhaust weight calculation unit.

  According to the present invention, there is provided an engine speed detector for detecting the engine speed and outputting a detection signal to the controller, wherein a state quantity related to the operation of the engine is the engine speed detection. The engine speed detected by the compressor, the fuel injection amount indicated by the fuel injection amount instruction unit, the intake amount detected by the intake amount detector, and the exhaust flow rate calculated by the first calculation unit of the controller It is characterized by being at least one of the following.

  The present invention is a work machine provided with a work device, and the controller includes a variation determination unit that determines whether or not a state quantity related to engine operation has suddenly changed. When it is determined that there is a sudden change, the reproduction determination unit is configured to invalidate the determination for a predetermined time when it is considered that the influence of the state quantity is reduced. With this configuration, forced regeneration that eliminates the influence of sudden fluctuations in the vehicle body can be realized. That is, unnecessary forced regeneration, which tends to occur due to sudden fluctuations in the vehicle body, can be suppressed, and useless fuel injection can be prevented, thereby improving fuel efficiency in a work machine equipped with an exhaust purification device.

1 is a side view showing a hydraulic excavator cited as an example of a working machine provided with an embodiment of an exhaust purification device according to the present invention. It is a figure which shows the structure of the exhaust gas purification apparatus which concerns on this embodiment with which the hydraulic shovel shown in FIG. 1 is equipped. It is a block diagram which shows the principal part structure of the controller with which this embodiment is equipped. It is a figure which shows the characteristic acquired by this embodiment.

  Embodiments of an exhaust emission control device for a work machine according to the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the hydraulic excavator constituting the work machine includes a traveling body 1 and a revolving body 2 disposed on the traveling body 1. The traveling body 1 and the swivel body 2 constitute a vehicle body. The hydraulic excavator is attached to the swing body 2 so as to be pivotable in the vertical direction. The working device 3 includes a boom, an arm, and the like; the cab 4 provided on the swing body 2; and a counter for ensuring a weight balance. A weight 5 and an engine room 6 disposed between the cab 4 and the counterweight 5 are provided.

  Further, as shown in FIG. 2, the hydraulic excavator includes an engine 10 housed in the engine chamber 6, an air cleaner 11 that removes air sucked into the engine chamber 6, that is, dust in the intake air, and the air cleaner 11. The turbocharger compressor 12 that compresses the intake air that has been cleaned and is guided by the intake passage 30, the intake passages 31 and 32 that lead the intake air compressed by the compressor 12 to the engine 10, and the intake passage 31 and the intake passage. And an intercooler 13 that cools intake air supplied to the engine 10. The hydraulic excavator also includes a turbocharger turbine 14 and an exhaust passage 33 that guide exhaust of the engine 10, and return passages 34 and 35 that recirculate a part of the exhaust of the engine 10 and supply the engine 10 again. An EGR (exhaust gas recirculation) cooler 15 is provided between the recirculation path 34 and the recirculation path 35 and cools the exhaust gas supplied to the engine 10.

  As shown in FIG. 2, the exhaust purification apparatus according to the present embodiment having such a configuration includes a filter 20 that collects PM contained in the exhaust of the engine 10 downstream of the exhaust, and an exhaust upstream of the filter 20. And a differential pressure detector 21 for detecting a differential pressure between the downstream side and the downstream side. Further, in the present embodiment, the PM collected by the filter 20 is burned by comparing the differential pressure detected by the differential pressure detector 21, that is, the detected differential pressure ΔP with the determination differential pressure ΔPo that is a determination threshold. A controller 22 having a regeneration determination unit 22a shown in FIG. 3 for determining whether or not the time for forced regeneration has been reached is provided. When it is determined by the regeneration determination unit 22a that the time at which forced regeneration is necessary has been reached, a control signal is output from the controller 22 to the fuel injection device 28 as shown in FIG. A predetermined amount of fuel is injected so as to be mixed into the fuel.

  Further, in the present embodiment, as shown in FIG. 2, the amount of intake air introduced to the intake passage 30, that is, the intake air amount is detected, and an intake air amount detector 23 that outputs a detection signal to the controller 22; An intake air temperature detector 24 that detects and outputs a detection signal to the controller 22, and an exhaust gas temperature detector 27 that detects the temperature of the exhaust gas guided to the exhaust passage 33 and outputs the detection signal to the controller 22.

  Further, in the present embodiment, as shown in FIG. 3, a fuel control unit 25 that controls an injection amount of fuel supplied to the engine 10 in accordance with a control signal output from a fuel injection amount instruction unit 22 e included in the controller 22. And an engine speed detector 26 that detects the speed of the engine 10 and outputs a detection signal to the controller 22.

  In the present embodiment, as shown in FIG. 3, the controller 22 determines whether or not the state quantity related to the operation of the engine 10, for example, the engine speed detected by the engine speed detector 26 has suddenly changed. The determination by the regeneration determination unit 22a is considered to be less affected by the sudden change in the engine speed when the engine speed is determined to be abruptly changed by the fluctuation determination unit 22b. For a predetermined period of time.

  A determination rotational speed change amount ΔN1 that is a threshold value for determining a sudden change in the engine rotational speed is stored in the controller 22. The fluctuation determination unit 22b compares the determined rotational speed change amount ΔN1 with the actual rotational speed change amount ΔN calculated based on the detection value of the engine speed detector 26, and when ΔN> ΔN1, It is determined that the rotational speed has fluctuated suddenly.

  In addition, the predetermined time described above is set experimentally or empirically in consideration of vehicle body fluctuations such as load fluctuations and rotation fluctuations that may occur in the hydraulic excavator shown in FIG.

As shown in FIG. 3, the controller 22 includes a first calculation unit 22 c that calculates the exhaust flow rate Vex, an exhaust flow rate Vex that is calculated by the first calculation unit 22 c, and a plurality of exhaust flow rates that are preset in the controller 22. And a second calculation unit 22d for calculating the determination differential pressure ΔPo based on a map indicating the relationship between the determination differential pressures and a plurality of determination differential pressures.

  In addition, the controller 22 determines the intake air temperature Tin that is detected according to the intake air temperature Tin detected by the intake air temperature detector 24 and a map that indicates a relationship between a plurality of intake air temperatures preset in the controller 22 and a plurality of intake air densities. An intake weight calculation unit 22f that calculates an intake weight Gin (= f2 × Vin) based on the intake air amount Vin detected by the intake air amount detector 23 is provided.

  Further, the controller 22 calculates the exhaust weight Gex (= Gin + q) based on the intake weight Gin calculated by the intake weight calculation unit 22f and the fuel injection amount q specified by the fuel injection amount instruction unit 22e described above. An exhaust weight calculation unit 22g is provided.

  The first calculation unit 22c of the controller 22 described above is based on the exhaust temperature Tex detected by the exhaust temperature detector 27, and a map showing the relationship between a plurality of exhaust temperatures preset in the controller 22 and a plurality of exhaust densities. Processing for calculating the exhaust flow rate Vex (= Gex / f3) is performed based on the exhaust density f3 obtained accordingly and the exhaust weight Gex calculated by the exhaust weight calculation unit 22g. Further, the regeneration determination unit 22a described above detects the determination differential pressure ΔPo calculated by the second calculation unit 22d according to the exhaust flow rate Vex calculated by the first calculation unit 22c and the detection detected by the differential pressure detector 21. Based on the differential pressure ΔP, it is determined whether or not the time when the forced regeneration is necessary has been reached as described above.

In this embodiment configured as described above, when the load A is relatively stable and the engine speed N is maintained at a constant high speed as indicated by the detection range S1 in FIG. The actual rotational speed change amount ΔN calculated based on the detected value detected in step S is equal to or smaller than the determined rotational speed change amount ΔN1, that is, ΔN ≦ ΔN1, and the engine speed is suddenly changed in the fluctuation determination unit 22b of the controller 22. It is determined that there is no fluctuation. Therefore, the regeneration determination unit 22a functions as normal, and determines whether or not the time when the forced regeneration for burning the PM collected by the filter 20 is necessary, that is, compares the detected differential pressure ΔP with the determined differential pressure ΔPo. A determination is made.

  In this regeneration determination unit 22a, if it is determined that ΔP ≦ ΔPo, it is determined that the time for which forced determination is necessary has not been reached, and a control signal for operating the fuel injection device 28 is not output. In addition, if the regeneration determination unit 22a determines that ΔP> ΔPo, it is determined that the time required for forced regeneration has been reached, and the fuel injection device 28 performs the injection for mixing the fuel into the exhaust of the engine 10 as described above. To do. As a result, the temperature of the exhaust gas rises due to the action of the oxidation catalyst, the PM collected in the filter 20 burns, and clogging of the filter 20 is eliminated.

  Further, in the fluctuation determination unit 22b of the controller 22, when the load A suddenly fluctuates as shown by the detection range S2 in FIG. 4 and the engine speed drops rapidly, for example, it is calculated based on the detected value of the speed detector 26. The actual engine speed change amount ΔN is larger than the determined engine speed change amount ΔN1, that is, ΔN> ΔN1, and the determination process of the regeneration determination unit 22a is set in advance, so that the influence of a sudden change in the engine speed is small. For the predetermined time T that is assumed to be, the process of invalidating is performed by the controller 22.

  According to the present embodiment configured as described above, it is possible to perform forced regeneration excluding the influence due to the sudden fluctuation of the engine speed N, that is, the influence due to the sudden fluctuation of the revolving structure 2 and the traveling body 1. That is, it is possible to suppress unnecessary forced regeneration that tends to occur due to sudden fluctuations in the revolving structure 2 and the traveling structure 1, and to prevent unnecessary fuel injection. Thereby, the fuel consumption in the hydraulic excavator provided with the exhaust purification device can be improved.

  In the above embodiment, the engine rotational speed N is given as the state quantity related to the operation of the engine 10 determined by the fluctuation determination section 22b of the controller 22, but this state quantity is the fuel injection amount instruction section of the controller 22. The fuel injection amount q indicated by 22e, the intake amount Vin detected by the intake amount detector 23, the exhaust flow rate Vex calculated by the first calculation unit 22c, or the like may be used. In addition, a plurality of state quantities among these state quantities may be determined by the variation determination unit 22b.

1 Running body (car body)
2 Revolving body (car body)
3 Working Device 6 Engine Room 10 Engine 12 Turbocharger Compressor 14 Turbocharger Turbine 20 Filter 21 Differential Pressure Detector 22 Controller 22a Regeneration Determination Unit 22b Fluctuation Determination Unit 22c First Calculation Unit 22d Second Calculation Unit 22e Fuel injection amount instruction unit 22f Intake weight calculation unit 22g Exhaust weight calculation unit 23 Intake amount detector 24 Intake temperature detector 25 Fuel control unit 26 Engine speed detector 27 Exhaust temperature detector 28 Fuel injection device A Load N Engine speed ΔP Detection differential pressure ΔPo Determination differential pressure ΔN Actual rotation speed change amount ΔN1 Determination rotation speed change amount

Claims (4)

A work device, a vehicle body body to which the work device is attached, and a work machine provided in the vehicle body body and provided with an engine for driving the work device;
A filter that collects particulate matter contained in the exhaust of the engine downstream of the exhaust, a differential pressure detector that detects a differential pressure between the exhaust upstream and downstream of the filter,
By comparing the differential pressure detected by this differential pressure detector with the judgment differential pressure that is the judgment threshold, it is determined whether or not the time when forced regeneration for burning the particulate matter collected in the filter is necessary has been reached. In an exhaust emission control device for a work machine comprising a controller having a regeneration determination unit for determining,
The controller has a variation determination unit that determines whether or not a state quantity related to the operation of the engine has suddenly changed. When the state determination unit determines that the state quantity has suddenly changed, the regeneration determination is performed. An exhaust emission control device for a working machine, comprising: a process for invalidating a determination by a unit for a predetermined time when the influence of the state quantity is considered to be reduced. The exhaust emission control device for a work machine according to claim 1,
The controller is based on a first calculation unit for calculating an exhaust flow rate, an exhaust flow rate calculated by the first calculation unit, and a map showing a relationship between an exhaust flow rate set in advance in the controller and a determination differential pressure. And an exhaust gas purification device for a work machine, comprising: a second calculation unit that calculates the determination differential pressure. The exhaust emission control device for a work machine according to claim 2,
A fuel control unit configured to inject an amount of fuel supplied to the engine; and the controller includes a fuel injection amount instruction unit configured to output a control signal for controlling the fuel control unit;
An intake air amount detector for detecting an intake air amount supplied to the engine and outputting a detection signal to the controller;
An intake air temperature detector that detects the temperature of the intake air and outputs a detection signal to the controller;
An exhaust temperature detector that detects the exhaust temperature of the engine and outputs a detection signal to the controller;
The controller
The intake air temperature detected by the intake air temperature detector and the intake air density determined according to the map indicating the relationship between the intake air temperature and the intake air density preset in the controller, and the intake air amount detector An intake weight calculation unit for calculating the intake weight based on the intake amount
An exhaust weight calculation unit that calculates the exhaust weight based on the intake weight calculated by the intake weight calculation unit and the fuel injection amount specified by the fuel injection amount instruction unit;
The first calculation unit of the controller is configured to determine an exhaust density determined according to an exhaust temperature detected by the exhaust temperature detector and a map indicating a relationship between an exhaust temperature and an exhaust density preset in the controller. And a process for calculating the exhaust flow rate based on the exhaust weight calculated by the exhaust weight calculation unit. The exhaust emission control device for a work machine according to claim 3,
An engine speed detector that detects the engine speed and outputs a detection signal to the controller;
The state quantity related to the operation of the engine includes the engine speed detected by the engine speed detector, the fuel injection quantity instructed by the fuel injection quantity instruction unit, and the intake quantity detected by the intake quantity detector. And an exhaust gas purification apparatus for a working machine, wherein the exhaust gas purification apparatus is at least one of exhaust gas flow rates calculated by the first calculation unit of the controller.

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