JP2016188583A - engine - Google Patents

Abstract

An engine for accurately detecting an ammonia adsorption amount of an SCR catalyst in order to inject an appropriate amount of urea water. An engine includes an upstream NOx sensor, a downstream NOx sensor, a detection unit, an estimation unit, and a summation unit. The upstream NOx sensor detects NOx contained in the exhaust gas upstream of the SCR catalyst. The downstream NOx sensor detects NOx contained in the exhaust gas downstream from the SCR catalyst. The detection unit obtains a NOx purification rate based on detection values of the upstream NOx sensor and the downstream NOx sensor, and obtains an adsorption amount calculation value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate. The estimation unit estimates a NOx purification rate based on at least the temperature of the SCR catalyst and the state of the exhaust gas, and obtains an adsorption amount estimated value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate. The summation unit calculates the ammonia adsorption amount of the SCR catalyst based on the adsorption amount calculation value and the adsorption amount estimation value. [Selection] Figure 6

Description

  The present invention relates to an engine that injects urea water to remove nitrogen oxides contained in exhaust gas.

  Conventionally, an engine that removes NOx (nitrogen oxide) contained in exhaust gas by using selective catalytic reduction (SCR) is known. This type of engine includes a urea water injection unit that injects urea water and an SCR catalyst. The urea water injection unit injects urea water into a path through which the exhaust gas passes. Urea contained in the urea water is hydrolyzed to ammonia by touching high-temperature exhaust gas. The SCR catalyst is made of a material such as zeolite or ceramic that adsorbs ammonia. NOx contained in the exhaust gas is reduced by touching the SCR catalyst that has adsorbed ammonia, and changes into nitrogen and water. Thereby, the amount of NOx emission can be reduced. Patent Documents 1 and 2 disclose this type of technology.

  In the SCR system of Patent Document 1, NOx sensors are arranged on the upstream side and the downstream side of the SCR catalyst, respectively. In this SCR system, the injection amount of urea water is controlled based on the detection values of the upstream and downstream NOx sensors. In Patent Document 1, when the NOx sensor cannot be used (after the engine is started, etc.), the urea water injection amount is set based on the engine speed, fuel injection amount, atmospheric pressure, outside air temperature, and cooling water temperature. Techniques for determining are also disclosed.

  The SCR system of Patent Document 2 estimates the ammonia adsorption amount of the SCR catalyst based on the state of exhaust gas and the like. In this SCR system, a target value of the ammonia adsorption amount is set based on the temperature of the SCR catalyst, and urea water is added (injected) until the ammonia adsorption amount reaches this target value.

JP 2013-72391 A JP2013-155644A

  However, in the configuration in which the injection amount of urea water is determined based on the NOx sensor as in Patent Document 1, when the accuracy of the NOx sensor is low, the ammonia adsorption amount cannot be obtained accurately, and an appropriate amount of urea water is obtained. Can not be injected. Here, since the NOx sensor may detect not only NOx but also ammonia (cross-sensitivity), the NOx detection accuracy may be lowered. Therefore, according to the method of Patent Document 1, an appropriate amount of urea water may not be injected depending on conditions. Moreover, in patent document 1, the structure which calculates | requires ammonia adsorption amount is not disclosed.

  Moreover, in the structure which estimates the ammonia adsorption amount of a SCR catalyst like patent document 2, an accuracy may fall depending on the estimation method. In particular, when the temperature of the SCR catalyst is low, the estimation accuracy of the ammonia adsorption amount may be lowered. Further, even when the catalyst is deteriorated or poisoned, the estimation accuracy of the ammonia adsorption amount may be lowered.

  When the estimation accuracy of the ammonia adsorption amount is low, NOx or ammonia may be discharged to the outside.

  The present invention has been made in view of the above circumstances, and its main object is to provide an engine that accurately detects the ammonia adsorption amount of the SCR catalyst in order to inject an appropriate amount of urea water. is there.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, an engine having the following configuration is provided. That is, the engine includes a urea water injection unit, an SCR catalyst, an upstream NOx sensor, a downstream NOx sensor, a detection unit, an estimation unit, and a summation unit. The urea water injection unit injects urea water into a path through which exhaust gas passes. The SCR catalyst is disposed in a path through which the exhaust gas passes, and adsorbs ammonia obtained from urea injected by the urea water injection unit, thereby removing nitrogen oxides contained in the passing exhaust gas. The upstream NOx sensor detects NOx contained in exhaust gas upstream of the SCR catalyst. The downstream NOx sensor detects NOx contained in exhaust gas downstream from the SCR catalyst. The detection unit obtains a NOx purification rate based on detection values of the upstream NOx sensor and the downstream NOx sensor, and obtains an adsorption amount calculation value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate. The estimation unit estimates a NOx purification rate based on at least the temperature of the SCR catalyst and the state of exhaust gas, and obtains an adsorption amount estimated value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate. The summation unit calculates an ammonia adsorption amount of the SCR catalyst based on the adsorption amount calculation value and the adsorption amount estimation value.

  Thereby, the ammonia adsorption amount can be obtained by two methods (a method using a NOx sensor and a method estimating based on the temperature of the SCR catalyst and the like). Therefore, compared to the case where the ammonia adsorption amount is obtained by using only one method, the influence of the generated error can be suppressed, so that an accurate ammonia adsorption amount can be obtained.

  In the engine, it is preferable that the summation unit calculates the ammonia adsorption amount of the SCR catalyst by weighting the adsorption amount calculation value and the adsorption amount estimation value.

  Thereby, the error in a predetermined condition can be further reduced by using an appropriate weighting factor.

  In the engine, it is preferable that the summation unit decreases the weighting coefficient of the adsorption amount estimated value as the temperature of the SCR catalyst decreases.

  As a result, even when the temperature of the SCR catalyst is lowered and the accuracy of the adsorption amount estimated value is lowered, the ammonia adsorption amount can be accurately obtained by reducing the weighting coefficient of the adsorption amount estimated value.

  In the engine, it is preferable that the summing unit relatively decreases the weight coefficient of the adsorption amount calculation value as the NOx amount detected by the downstream NOx sensor decreases.

  Thereby, even when the amount of NOx contained in the exhaust gas is reduced and the accuracy of the adsorption amount calculation value is reduced, the ammonia adsorption amount can be obtained accurately by decreasing the weighting coefficient of the adsorption amount calculation value. Can do.

  The engine preferably has the following configuration. That is, the engine includes an altitude sensor that detects altitude. The summation unit decreases the weight coefficient of the adsorption amount estimated value as the altitude detected by the altitude sensor increases.

  As a result, even if the accuracy of the adsorption amount estimated value is reduced due to a decrease in intake pressure or a decrease in oxygen contained in the intake air at high altitude, the weight coefficient of the adsorption amount estimated value is relatively decreased, thereby reducing ammonia. The amount of adsorption can be determined with high accuracy.

1 is a perspective view of an engine according to an embodiment of the present invention. Explanatory drawing which shows typically the flow of the intake and exhaust of an engine. The block diagram which concerns on engine control. Formula used when calculating the ammonia adsorption amount. The figure which shows the process which estimates a NOx purification rate from SCR catalyst temperature etc. The figure which shows the process which calculates | requires adsorption amount calculation value and adsorption amount estimated value. The figure which shows the process which calculates | requires the weighting coefficient of adsorption amount estimated value. The figure which shows the process which calculates | requires ammonia adsorption amount from adsorption amount estimated value and adsorption amount calculation value. The side view which shows a mode that the engine of this embodiment was applied to the tractor. The side view which shows a mode that the engine of this embodiment was applied to the combine. The side view which shows a mode that the engine of this embodiment was applied to the skid steer loader.

  Next, embodiments of the present invention will be described with reference to the drawings. First, a basic configuration of the engine 100 of the present embodiment will be described with reference to FIGS. 1 to 3. The engine 100 is a diesel engine and is mounted on an agricultural machine such as a tractor and a construction machine such as a skid steer loader.

  As shown in FIGS. 1 and 2, the engine 100 includes an intake portion 11, a supercharger 12, an intake throttle (intake throttle device) 14, and an intake manifold 15 as intake system members. The gas sucked from the suction portion 11 is compressed by the supercharger 12 and then supplied to the intake manifold 15 via the intake throttle 14. As shown in FIG. 2, an intake air temperature sensor 84 is attached to the intake manifold 15. The intake temperature sensor 84 detects the temperature of the gas in the intake manifold 15 and outputs it to an ECU (Engine Control Unit) 80.

  As shown in FIG. 3, engine 100 includes an ECU 80. ECU80 is provided with the calculating part comprised from CPU etc., and the memory | storage part comprised from ROM, RAM, etc. The calculation unit sends control commands to various actuators in the actuator group based on information from various sensors in the sensor group, and values related to the operation of the engine 100 (for example, fuel injection amount, air intake amount, exhaust gas, etc. The amount of reduction, etc.) is controlled. The storage unit stores various programs and a plurality of control information set in advance with respect to the control of the engine 100. ECU80 is provided with the detection part 80a, the estimation part 80b, and the summing part 80c, as shown in FIG. The processing performed by these will be described later.

  As shown in FIG. 3, engine 100 includes a cooling water temperature sensor 81 that detects the temperature of the cooling water and outputs it to ECU 80, and an atmospheric pressure sensor 82 that detects the atmospheric pressure and outputs it to ECU 80.

  A common rail (not shown) is disposed below the intake manifold 15. The common rail stores fuel at a high pressure and supplies the fuel to an injector 23 (fuel injection device, see FIG. 2) arranged in the cylinder head.

  The injector 23 includes an injector solenoid valve 24 (see FIG. 3). The injector solenoid valve 24 is opened and closed at a timing according to an instruction from the ECU 80 to inject fuel into the combustion chamber.

  The engine 100 includes an engine speed detection sensor 83 that detects the engine speed (rotation speed, rotation speed of the crankshaft per predetermined time). The engine speed detection sensor 83 outputs the detected engine speed to the ECU 80.

  As shown in FIGS. 1 and 2, the engine 100 includes an exhaust manifold 31, an EGR device 32, and an exhaust gas purification device 40.

  An exhaust temperature sensor 85 is attached to the exhaust manifold 31. The exhaust temperature sensor 85 detects the temperature of the gas in the exhaust manifold 31 and outputs it to the ECU 80. A part of the gas that has passed through the exhaust manifold 31 is supplied to the EGR device 32 and the rest is supplied to the exhaust gas purification device 40.

  The EGR device 32 includes an EGR cooler 33, an EGR pipe 34, and an EGR valve 35. The valve opening degree of the EGR valve 35 is controlled by the ECU 80.

  The exhaust gas purification device 40 includes a DPF device 50 and an SCR device 60. The engine 100 includes a support base 41, a case fixing body 42, and a case fastening band 43 as members that support and fix the exhaust gas purification device 40.

  The support base 41 is a rectangular member that is disposed at the upper part of the cylinder head and has an edge bent downward. The case fixing body 42 is a member that is disposed on the upper portion of the support base 41 and contacts the lower side of the DPF device 50 and the SCR device 60. The case fastening band 43 is a flexible member configured to be attachable to the case fixing body 42. The DPF device 50 and the SCR device 60 are fixed by sandwiching the DPF device 50 and the SCR device 60 between the case fixing body 42 and the case fastening band 43.

  The DPF device 50 removes particulate matter (PM) contained in the exhaust gas. The DPF device 50 includes a DPF case 51, an oxidation catalyst 52, and a filter 53.

  The DPF case 51 is a substantially cylindrical hollow member, in which an oxidation catalyst 52 and a filter 53 are disposed. The oxidation catalyst 52 is made of platinum or the like, and is a catalyst for oxidizing (combusting) unburned fuel, carbon monoxide, nitrogen monoxide and the like contained in the exhaust gas. The filter 53 is configured as a wall flow type filter, for example, and collects particulate matter contained in the exhaust gas treated by the oxidation catalyst 52.

  Further, an oxidation catalyst temperature sensor 86, a filter temperature sensor 87, and a differential pressure sensor 88 are attached to the DPF case 51. The oxidation catalyst temperature sensor 86 detects the temperature in the vicinity of the inlet of the DPF case 51 (the exhaust upstream side of the oxidation catalyst 52) and outputs it to the ECU 80. The filter temperature sensor 87 detects the temperature between the oxidation catalyst 52 and the filter 53 (upstream side of the filter 53) and outputs the detected temperature to the ECU 80. The differential pressure sensor 88 detects a pressure difference between the upstream side of the filter 53 (downstream side of the oxidation catalyst 52) and the downstream side of the filter 53, and outputs it to the ECU 80.

  The exhaust gas that has passed through the DPF device 50 is sent to the SCR device 60 via the DPF outlet pipe 44, the urea mixing pipe 45, and the SCR inlet pipe 46. The DPF outlet pipe 44 is connected to the downstream end of the DPF device 50. An upstream NOx sensor 89 that detects the NOx concentration of the exhaust gas is attached to the DPF outlet pipe 44. The upstream NOx sensor 89 outputs the detected NOx concentration to the ECU 80.

  The urea mixing pipe 45 is connected so as to be substantially perpendicular to the DPF outlet pipe 44. The longitudinal direction of the urea mixing tube 45 is parallel to the longitudinal directions of the DPF device 50 and the SCR device 60. In the vicinity of the upstream end of the urea mixing tube 45, a urea water injection unit 47 is attached. The urea water injection unit 47 includes a urea water injection nozzle 47a that injects urea water, and a urea water injection pipe 47b that supplies urea water to the urea water injection nozzle 47a. By injecting urea water into the urea mixing tube 45, urea is hydrolyzed and ammonia is generated.

  The urea water injection unit 47 is controlled by the ECU 80 and a DCU (Dosing Control Unit) 95 to determine whether or not to inject urea water. For example, when the temperature of the exhaust gas has passed the temperature at which urea is hydrolyzed into ammonia, the DCU 95 starts injection of urea water.

  The SCR device 60 removes NOx contained in the exhaust gas introduced through the SCR inlet pipe 46. The SCR device 60 includes an SCR case 61, an SCR catalyst 62, and an ammonia oxidation catalyst 63.

  The SCR case 61 is a substantially cylindrical hollow member, in which an SCR catalyst 62 and an ammonia oxidation catalyst 63 are disposed. The SCR catalyst 62 is made of a material such as zeolite or ceramic that adsorbs ammonia. Ammonia generated by the urea water injection unit 47 injecting the urea water is adsorbed on the SCR catalyst 62. NOx contained in the exhaust gas is reduced by touching the SCR catalyst 62 that has adsorbed ammonia, and changes into nitrogen and water.

  The ammonia oxidation catalyst 63 is a catalyst that prevents the ammonia that has been desorbed from the SCR catalyst 62 and not adsorbed by the SCR catalyst 62 from being released to the outside. The ammonia oxidation catalyst 63 is an oxidation catalyst such as platinum that oxidizes ammonia, and oxidizes ammonia to change it into nitrogen, oxygen monoxide, water, or the like. This oxidation reaction hardly occurs unless the temperature is relatively high (for example, 180 ° C. or higher). The exhaust gas passes through the ammonia oxidation catalyst 63, passes through a predetermined exhaust pipe, and is then discharged to the outside. By providing the urea water injection unit 47 and the SCR catalyst 62 as described above, NOx contained in the exhaust gas can be removed.

  An SCR catalyst inlet temperature sensor 90 is attached upstream of the SCR catalyst 62. The SCR catalyst inlet temperature sensor 90 detects the temperature immediately upstream of the SCR catalyst 62 and outputs the detected temperature to the ECU 80.

  A downstream NOx sensor 91 is attached to the downstream side of the ammonia oxidation catalyst 63. The downstream NOx sensor 91 outputs the detected NOx concentration to the ECU 80.

  Next, control for calculating the ammonia adsorption amount of the SCR catalyst 62 in order to determine the urea water injection amount will be described with reference to FIGS. Hereinafter, the ammonia adsorption amount of the SCR catalyst 62 is simply referred to as “ammonia adsorption amount”.

  First, a method for calculating the ammonia adsorption amount will be described with reference to FIG. The left side of equation (1) in FIG. 4 indicates ammonia supplied to the SCR device 60, and the right side indicates ammonia consumed or discharged by the SCR device 60. The left side of the formula (1) indicates “ammonia supplied by urea water”. The right side of the formula (1) is, in order from the left, “ammonia used to remove NOx”, “ammonia changed to nitrogen”, “ammonia changed to nitrogen dioxide”, “ammonia adsorbed on the SCR catalyst 62” "," Ammonia discharged from the SCR device 60 ".

  Here, “ammonia changed to nitrogen” and “ammonia changed to nitrogen dioxide” can be approximated to zero. Further, since the ECU 80 and the DCU 95 control so that ammonia is not discharged from the SCR device 60, “ammonia discharged from the SCR device 60” can also be approximated to zero. Therefore, equation (1) can be approximated as equation (2).

  Therefore, as shown in the equation (3), “ammonia adsorbed on the SCR catalyst 62” is obtained by subtracting “ammonia used for removing NOx” from “ammonia supplied by urea water”. It is done.

  Here, “ammonia used to remove NOx” can be obtained as shown in Equation (4). Specifically, by integrating the “equivalent ratio according to the reaction formula” to the “difference between the upstream and downstream NOx concentrations of the SCR device 60” and further integrating the “ratio of the molecular weight of ammonia to NOx”, Can be sought. The “difference between the NOx concentration upstream and downstream of the SCR device 60” can be obtained from the NOx purification rate (NOxη) as shown in the equation (5).

  As described above, the ammonia adsorption amount can be determined based on the urea water injection amount and the NOx purification rate. In the present embodiment, the NOx purification rate is obtained by two methods. The first method is a method of obtaining the detection values of the upstream NOx sensor 89 and the downstream NOx sensor 91 by substituting them into the equation (5) in FIG. This process is performed by the ECU 80 (specifically, the detection unit 80a). The second method is a method of estimating the NOx purification rate based on the exhaust gas state and the like. This process is performed by the ECU 80 (specifically, the estimation unit 80b).

  Next, a method for estimating the NOx purification rate will be described in detail with reference to FIG. As shown in FIG. 5, the NOx purification rate is estimated based on the SCR catalyst temperature, the exhaust gas mass flow rate, the NOx amount (concentration) based on the DPF temperature, and the like.

  The SCR catalyst temperature is estimated based on the SCR catalyst inlet temperature, the catalyst volume of the SCR catalyst 62, the exhaust gas mass flow rate, and the like. The method for estimating the SCR catalyst temperature is arbitrary, and a temperature sensor may be provided downstream of the SCR catalyst 62, and the SCR catalyst temperature may be estimated using not only the SCR catalyst inlet temperature but also the SCR catalyst outlet temperature. The SCR catalyst 62 is related to the NOx purification rate because the amount of ammonia that can be adsorbed changes according to the temperature. Further, the mass flow rate of the exhaust gas is obtained by calculation based on the operating state of the engine and the like.

The DPF temperature is obtained based on the temperature detected by the oxidation catalyst temperature sensor 86 or the like. In the DPF device 50, it is difficult to generate NO ₂ when the temperature is high. Therefore, the DPF temperature is related to the NOx purification rate.

  Next, with reference to FIGS. 6 to 8, a process for obtaining the ammonia adsorption amount using the NOx purification rates obtained by two methods will be described.

  FIG. 6 shows a process for obtaining the ammonia adsorption amount based on the NOx purification rates obtained by two methods. The ECU 80 applies the NOx purification rate obtained from the detection values of the upstream NOx sensor 89 and the downstream NOx sensor 91 to the equations (4) and (5) in FIG. 4 and uses the ammonia flow rate used to remove NOx. Ask for. Then, by subtracting the ammonia flow rate used to remove NOx from the ammonia injection flow rate calculated from the urea water injection amount (processing P1 in FIG. 6 and equation (3) in FIG. 4), the NOx sensor. The ammonia adsorption amount (adsorption amount calculation value) based on the detected value is obtained.

  Similarly, the ECU 80 applies the NOx purification rate estimated based on the state of the exhaust gas or the like to the equation (5) in FIG. 4 to obtain the ammonia flow rate used for removing NOx. Then, by subtracting the ammonia flow rate used to remove NOx from the ammonia injection flow rate (processing P2 in FIG. 6, equation (3) in FIG. 4), the ammonia adsorption amount based on the estimated value of the NOx purification rate (Adsorption amount estimated value) is obtained.

  In the present embodiment, the ammonia adsorption amount is obtained by weighting the adsorption amount calculation value and the adsorption amount estimation value. FIG. 7 shows a process for obtaining a weighting coefficient when performing this weighting.

Here, as described above, when the SCR catalyst temperature is low, the sensitivity of NO ₂ and NOx increases, so that the estimation accuracy of the NOx purification rate decreases, and the error in the adsorption amount estimation value increases. Therefore, when the SCR catalyst temperature is low, it is preferable to reduce the weighting coefficient of the estimated adsorption amount.

  Further, ammonia may be contained in the exhaust gas downstream of the SCR catalyst 62. Since the downstream NOx sensor 91 may detect not only NOx but also ammonia, when the NOx concentration is low, the detection accuracy of the NOx concentration is lowered and the error of the adsorption amount calculation value is increased. Therefore, when the detection value of the downstream NOx sensor 91 is low, it is preferable to reduce the weight coefficient of the adsorption amount calculation value. Instead of the SCR catalyst temperature, other temperatures (for example, exhaust gas temperature) may be used.

  In addition, when the engine 100 is used in a highland such as a high mountain, there is a possibility that the accuracy of the adsorption amount estimated value may decrease due to a change in intake conditions and the like. The altitude can be grasped based on the detection value of the atmospheric pressure sensor 82. Therefore, when the atmospheric pressure detected by the atmospheric pressure sensor 82 is low, it is preferable to reduce the weighting coefficient of the adsorption amount estimated value.

  FIG. 7 shows a process for obtaining the weight coefficient (0 ≦ s ≦ 1) of the adsorption amount detection value in consideration of the above situation. 7 and 8 is performed by the summing unit 80c of the ECU 80.

  Further, since the total weighting factor is 1, the weighting factor (0 ≦ t ≦ 1) of the suction amount estimation value can be obtained by subtracting the weighting factor of the suction amount detection value from 1. As shown in FIG. 7, the ECU 80 performs a process of calculating a weighting coefficient based on the SCR catalyst temperature and the detected value of the downstream NOx sensor 91 (process P3). As described above, the weighting coefficient of the adsorption amount detection value decreases as the SCR catalyst temperature decreases, and the weighting coefficient of the adsorption amount detection value increases as the detection result of the downstream NOx sensor 91 decreases.

  Further, the ECU 80 calculates a correction value of the weighting coefficient based on the detection value of the atmospheric pressure sensor 82 (process P4), and adds it to the correction coefficient obtained in the process P3 (process P5), thereby obtaining the adsorption amount detection value. Find the weighting factor. In addition, the method of calculating | requiring a weighting coefficient based on the SCR catalyst temperature, the detected value of the downstream NOx sensor 91, and the altitude is arbitrary. Further, the weight coefficient may be calculated using parameters other than those described above.

  FIG. 8 is a diagram illustrating a process for obtaining the ammonia adsorption amount using the weighting coefficient. The ECU 80 adds the adsorption amount detection value to the weighting coefficient obtained in FIG. 7 (Process P6). Further, the ECU 80 subtracts the weighting coefficient of the suction amount detection value from 1 to obtain the weighting coefficient of the suction amount estimation value (processing P7). The ECU 80 adds the estimated adsorption amount to this weighting coefficient (processing P8). Further, the ECU 80 calculates the ammonia adsorption amount by adding the result of the process P6 and the result of the process P8 (process P9).

  The ECU 80 performs control such as determining the injection amount of urea water using the ammonia adsorption amount obtained as described above. Specifically, since the amount of ammonia that can be adsorbed on the SCR catalyst 62 varies depending on the SCR catalyst temperature, the target ammonia adsorption amount is calculated based on the temperature of the SCR catalyst. Note that the target ammonia adsorption amount can also be calculated in consideration of the NOx concentration contained in the exhaust gas. The ECU 80 determines the injection amount of urea water by performing PID control or the like so that the difference (deviation) between the target ammonia adsorption amount and the ammonia adsorption amount obtained in FIG.

  Next, an example in which the engine 100 described above is applied to an agricultural machine and a construction machine will be described. In the following description, “left side”, “right side” and the like simply mean the left side and the right side in the direction in which the vehicle moves forward.

  First, the tractor 110 including the engine 100 will be described with reference to FIG. The tractor 110 is a work vehicle for agricultural work, and can be equipped with various work machines (attachments) such as a rotary, a loader, a plow, a box scraper, and the like to perform various work using the work machine. it can.

  The tractor 110 includes a vehicle body 111, a pair of left and right front wheels 112, and a pair of left and right rear wheels 113. A bonnet 114 is arranged at the front of the vehicle body 111, and the engine 100 is arranged inside the bonnet 114.

  A radiator 5 is arranged inside the bonnet 114 and opposite the cooling fan 4. An air cleaner 122 is arranged inside the bonnet 114. The air cleaner 122 removes dust and the like contained in the sucked outside air.

  A mission case 115 is disposed between the pair of left and right rear wheels 113. The output of the engine 100 is shifted by the transmission in the transmission case 115 and transmitted to the rear wheel 113 and the work machine.

  At the rear of the mission case 115, a lower link 116, a top link 117, and a PTO shaft 118 are arranged. In addition, on the upper part of the mission case 115, the work implement is connected to the lower link 116 and the top link 117 and is driven by the PTO shaft 118.

  A cabin 119 for an operator to board is disposed above the mission case 115 and behind the hood 114. A driver's seat is provided inside the cabin 119, and a number of operating tools for an operator to operate are provided in the vicinity of the driver's seat.

  A urea water tank 120 and a fuel tank 121 are disposed below the cabin 119. The urea water tank 120 is connected to the urea water injection nozzle 47a by a urea water injection pipe 47b.

  Next, with reference to FIG. 10, the combine 130 provided with said engine 100 is demonstrated. The combine 130 is configured as a so-called self-removing combine. A crawler section 132 for running the machine body 131 is provided below the machine body 131 of the combine 130. Further, the combine 130 is provided with a cutting part 133 in front of the machine body 131 for cutting off the stock of rice grains and wheat.

  The cutting unit 133 includes a plurality of weed bodies and a cutting blade. The plurality of herbaceous bodies define a width for harvesting the culm or scoop up the culm in a fallen state. The cereal buds inserted between the weeds are cut and cut near the root by a cutting blade.

  Further, the cutting unit 133 is connected to the body 131 of the combine 130 via a lifting mechanism (not shown). This elevating mechanism is configured to be able to drive the mowing unit 133 up and down. Thereby, according to the inclination of a farm field, etc., the height of the cutting part 133 can be adjusted to an appropriate height, and cutting can be performed appropriately.

  A threshing device 134 is provided behind the mowing unit 133 and on the left side of the combine 130. The threshing apparatus 134 threshs the cereals harvested by the reaping unit 133. A sorting device 135 is provided below the threshing device 134. The sorting device 135 sorts and takes out the grains threshed by the threshing device 134.

  A Glen tank 136 is provided behind the cutting unit 133 and on the right side of the combine 130. Glen tank 136 stores the grains selected by sorting device 135. The grain stored in the Glen tank 136 is discharged to the outside by the discharge auger 137.

  A cabin 138 for an operator to board is disposed in front of the Glen tank 136. Inside the cabin 138, a driver's seat is provided, and a number of operating tools for an operator to operate are provided in the vicinity of the driver's seat.

  An engine 100 is disposed below the cabin 138. A radiator (not shown) is disposed opposite the cooling fan 4 of the engine 100. Further, a pre-cleaner 139 is disposed behind the cabin 138. Dust and the like are removed from the outside air sucked from the precleaner 139 through an unillustrated air cleaner. A urea water tank 140 is disposed near the engine 100.

  The sawdust from which the grain has been removed from the cereal is conveyed backward, cut into an appropriate length by an unillustrated evacuation cutter device, and discharged outside the machine.

  Next, a skid steer loader 150 including the engine 100 will be described with reference to FIG. The skid steer loader 150 is configured to load a loader device 151 to be described later and perform a loader operation. A pair of left and right crawler units 152 are mounted on the skid steer loader 150. A bonnet 153 is disposed above the crawler unit 152.

  An engine 100 is disposed inside the bonnet 153. A radiator 5 is disposed inside the hood 153 and opposite the cooling fan 4 of the engine 100. A urea water tank 154 is disposed inside the hood 153 and in front of the engine 100.

  A hydraulic pump 155 and a transmission device 156 are disposed in front of the engine 100. The power of the engine 100 is transmitted to the crawler unit 152 via the transmission device 156.

  In front of the hood 153, a cabin 157 on which an operator is boarded is disposed. A driver's seat is provided inside the cabin 157, and a number of operating tools for operation by an operator are provided in the vicinity of the driver's seat.

  In addition, the loader device 151 is capable of rotating to a loader post 158 disposed on both left and right sides, a pair of left and right lift arms 159 rotatably connected to the top of each loader post 158, and a tip end of the lift arm 159. And a bucket 160 connected to.

  Between each loader post 158 and the lift arm 159, a lift cylinder 161 for rotating the lift arm 159 up and down is provided. A bucket cylinder 162 for rotating the bucket 160 up and down is provided between the lift arm 159 and the bucket 160. When the operator operates an operation tool (not shown), the hydraulic pressure of the hydraulic pump 155 is controlled. Thereby, the lift cylinder 161 or the bucket cylinder 162 expands and contracts, and the lift arm 159 or the bucket 160 rotates. The operator can carry out work such as earth and sand in this way.

  As described above, the engine 100 of this embodiment includes the urea water injection unit 47, the SCR catalyst 62, the upstream NOx sensor 89, the downstream NOx sensor 91, the detection unit 80a, and the estimation unit 80b. Part 80c. The urea water injection unit 47 injects urea water into the path through which the exhaust gas passes. The SCR catalyst 62 is disposed in a path through which the exhaust gas passes, and adsorbs ammonia obtained from urea injected by the urea water injection unit 47, thereby removing nitrogen oxides contained in the passing exhaust gas. The upstream NOx sensor 89 detects NOx contained in the exhaust gas upstream of the SCR catalyst 62. The downstream NOx sensor 91 detects NOx contained in the exhaust gas downstream from the SCR catalyst 62. The detection unit 80a obtains a NOx purification rate based on the detection values of the upstream NOx sensor 89 and the downstream NOx sensor 91, and obtains an adsorption amount calculation value that is an ammonia adsorption amount of the SCR catalyst 62 based on the NOx purification rate. The estimation unit 80b estimates the NOx purification rate based on at least the temperature of the SCR catalyst 62 and the state of the exhaust gas, and obtains an estimated adsorption amount that is the ammonia adsorption amount of the SCR catalyst 62 based on the NOx purification rate. The summation unit 80c calculates the ammonia adsorption amount of the SCR catalyst 62 based on the adsorption amount calculation value and the adsorption amount estimated value.

  Thereby, the ammonia adsorption amount can be obtained by two methods (a method using a NOx sensor and a method estimating based on the temperature of the SCR catalyst and the like). Therefore, compared to the case where the ammonia adsorption amount is obtained by using only one method, the influence of the generated error can be suppressed, so that an accurate ammonia adsorption amount can be obtained. Therefore, it is possible to accurately control NOx and ammonia so that they are not discharged to the outside.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  The DCU 95 may perform part of the processing described as being performed by the ECU 80 in the above embodiment. Further, the ECU 80 and the DCU 95 may be configured by one control device.

  In the above embodiment, the adsorption amount calculation value and the adsorption amount estimation value are weighted to obtain the ammonia adsorption amount. However, the adsorption amount calculation value and the adsorption amount are determined according to the SCR catalyst temperature, the detection value of the downstream NOx sensor 91, and the like. Any one of the estimated values may be selected, and the selected value may be used as the ammonia adsorption amount. Even in this case, it corresponds to the process of “calculating the ammonia adsorption amount based on the adsorption amount calculation value and the adsorption amount estimation value”.

  In the above embodiment, the DPF device 50 and the SCR device 60 are located at the top of the engine 100, but the arrangement of the DPF device 50 and the SCR device 60 is arbitrary. For example, the DPF device 50 and the SCR device 60 are arranged relatively far from the cylinder block. May be. Further, in this specification, even if the DPF device 50 and the SCR device 60 are separated from the cylinder block, they are included in the “engine”.

  Although the example which applies this invention to the diesel engine provided with a supercharger was shown above, this invention is applicable also to a naturally aspirated diesel engine.

47 Urea water injection unit 50 DPF device 60 SCR device 61 SCR case 62 SCR catalyst 63 Ammonia oxidation catalyst 80 ECU
82 Atmospheric pressure sensor (altitude sensor)
95 DCU
100 engine

Claims (5)

A urea water injection unit that injects urea water into a path through which exhaust gas passes;
An SCR catalyst that is disposed in a path through which exhaust gas passes and adsorbs ammonia obtained from urea injected by the urea water injection unit, thereby removing nitrogen oxides contained in the exhaust gas that passes through;
An upstream NOx sensor for detecting NOx contained in exhaust gas upstream of the SCR catalyst;
A downstream NOx sensor for detecting NOx contained in exhaust gas downstream from the SCR catalyst;
A detection unit that obtains a NOx purification rate based on detection values of the upstream NOx sensor and the downstream NOx sensor, and obtains an adsorption amount calculation value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate;
An estimation unit that estimates a NOx purification rate based on at least the temperature of the SCR catalyst and the state of exhaust gas, and obtains an adsorption amount estimated value that is an ammonia adsorption amount of the SCR catalyst based on the NOx purification rate;
A summing unit that calculates an ammonia adsorption amount of the SCR catalyst based on the adsorption amount calculation value and the adsorption amount estimation value;
An engine comprising: The engine according to claim 1,
The engine is characterized in that the summation unit calculates an ammonia adsorption amount of the SCR catalyst by weighting the adsorption amount calculation value and the adsorption amount estimation value. The engine according to claim 2,
The engine is characterized in that the summing unit decreases the weighting coefficient of the adsorption amount estimated value as the temperature of the SCR catalyst decreases. The engine according to claim 2 or 3,
The engine is characterized in that the summation unit relatively decreases the weighting coefficient of the adsorption amount calculation value as the NOx amount detected by the downstream NOx sensor decreases. An engine according to any one of claims 2 to 4,
Equipped with an altitude sensor that detects altitude,
The engine is characterized in that the summation unit decreases the weighting coefficient of the adsorption amount estimated value as the altitude detected by the altitude sensor increases.

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