JP6426064B2 - engine - Google Patents

Description

  The present invention relates to an engine provided with an exhaust gas purification device.

  2. Description of the Related Art Conventionally, an engine is known which sets a maximum injection amount of fuel based on a limited injection amount calculated according to a plurality of operating conditions. Patent Document 1 discloses this type of engine.

  In the engine of Patent Document 1, the reference maximum injection amount calculated based on the target engine speed of the engine and the coolant temperature of the engine, the atmospheric pressure limited injection amount calculated based on the target engine speed and the atmospheric pressure, and excess air The smallest value among the black smoke limited injection amount (λ limited injection amount) calculated based on the ratio is set as the final maximum injection amount (maximum fuel injection amount), and the elapsed time since the start of the engine is completed When the time is less than the predetermined time or when the coolant temperature is less than the predetermined temperature, a value obtained by increasing the reference maximum injection amount by the predetermined amount is set as the final maximum injection amount. According to Patent Document 1, this configuration can provide an engine that stabilizes the operating state regardless of the operating environment and the mode of use.

JP, 2014-25441, A

  In the configuration of Patent Document 1, the black smoke limited injection amount is calculated using the excess air ratio (λ) and the black smoke limited injection amount map (λ base map) stored in the control unit. Since the excess air ratio is obtained by dividing the air-fuel ratio by the theoretical air-fuel ratio, the calculation requires the amount of oxygen contained in the mixture in the cylinder (so-called air mass). Therefore, the calculation of the excess air ratio requires an amount of air taken into the cylinder, and in a configuration where exhaust gas recirculation (exhaust gas recirculation) is performed to return the exhaust gas to the intake side and re-inhale, the cylinder is The amount of EGR gas to be inhaled is also required.

  The amount of air taken into the cylinder and the amount of EGR gas can be determined by theoretical calculation using a known equation. However, for example, when the difference between the pressure on the exhaust side and the pressure on the intake side is small, it is difficult to accurately determine the EGR recirculation amount, so it is possible to constantly calculate the amount of oxygen contained in the mixture in the cylinder with high accuracy. However, the calculation accuracy of the excess air ratio may decrease.

  If a negative error occurs in the excess air ratio obtained by the calculation, the black smoke limited injection amount calculated based on the excess air ratio becomes too small. As a result, the fuel injection amount is restricted more than necessary, and there is a possibility that the output reduction or the engine stall may occur particularly in the transition period (the period when the acceleration of the vehicle or the loading of the load is performed).

  On the other hand, when an error on the positive side occurs in the excess air ratio obtained by the calculation, the black smoke limited injection amount calculated based on the excess air ratio λ becomes excessive. As a result, the restriction of the fuel injection amount is insufficient and a large amount of black smoke is generated, which may result in the need to frequently regenerate the exhaust gas purification device (DPF: Diesel Particulate Filter).

  The present invention has been made in view of the above circumstances, and its object is to calculate the fuel injection amount in both cases where the amount of oxygen (air mass) contained in the mixture in the cylinder can be calculated with high accuracy. To provide an engine that can be appropriately limited.

Means and effect for solving the problem

  The problem to be solved by the present invention is as described above, and next, means for solving the problem and its effect will be described.

  According to an aspect of the present invention, an engine having the following configuration is provided. That is, the engine includes an exhaust gas purification device and a control unit. The exhaust gas purification device purifies the exhaust gas. The control unit determines the limited injection amount, which is the upper limit value of the fuel injection amount, based on the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio. The lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio differs depending at least on the amount of accumulated particulate matter collected by the exhaust gas purification device.

  By making the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio different on the basis of the accumulated amount of particulate matter in this manner, the fuel injection can be performed taking into account that the calculation accuracy of the air mass may change depending on, for example, the exhaust pressure. The amount can be limited appropriately. For example, if the deposition amount of particulate matter is small and the calculation accuracy of air mass is expected to be low, the lower limit value of the excess air ratio is intentionally decreased (or the upper limit of the fuel / air ratio is intentionally increased). Thus, it is possible to prevent a decrease in output due to the fuel injection amount being excessively limited, an engine stall or the like. On the other hand, when there is a large amount of accumulated particulate matter and it is expected that the calculation accuracy of the air mass is high, the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio should be a value that should originally be (or a value near it) As a result, it is possible to avoid the generation of unburned fuel and the increase in the regeneration frequency of the exhaust gas purification device due to the insufficient restriction of the fuel injection amount.

  The above-described engine preferably has the following configuration. That is, the control unit corrects the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio based on the deposition amount of the particulate matter collected by the exhaust gas purification device. The control unit obtains the limited injection amount using the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio after the correction.

  As described above, the fuel injection amount is properly adjusted according to the situation by correcting the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio according to the deposition amount of the particulate matter deposited in the exhaust gas purification device. Can be limited to

  The above-described engine preferably has the following configuration. That is, the control unit obtains the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio based on the engine speed and the fuel injection amount. The control unit determines a correction reference amount of the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio based on the engine speed and the fuel injection amount, and at least a correction coefficient of the deposition amount of the particulate matter Ask based on The control unit corrects the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio using a value obtained by multiplying the correction reference amount by the correction coefficient.

  As a result, the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio can be appropriately corrected in consideration of the engine speed, the fuel injection amount, and the accumulated amount of particulate matter in a combined manner. Therefore, a reduction in engine output, engine stall, or clogging of the exhaust gas purification device can be further suitably prevented.

  The above-described engine preferably has the following configuration. That is, the engine includes an intake air temperature detection unit that detects an intake air temperature. The control unit determines the correction coefficient based on at least the deposition amount of the particulate matter and the intake air temperature detected by the intake air temperature detection unit.

  Thus, the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio can be corrected in consideration of the intake air temperature, for example, to prevent the generation of unburned fuel or black smoke when the intake temperature is high. can do.

  The above-described engine preferably has the following configuration. That is, information for obtaining the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio based on the engine rotational speed and the fuel injection amount is previously stored in the control unit according to the deposition amount of the particulate matter. Multiple stored. The control unit obtains a lower limit value of the excess air ratio or an upper limit value of the fuel-air ratio based on the information corresponding to the deposition amount of the particulate matter among the plurality of pieces of stored information.

  Thereby, the fuel injection amount can be appropriately limited in accordance with the situation.

  The above-described engine preferably has the following configuration. That is, this engine includes a supercharger, an atmospheric pressure detection unit, and a coolant temperature detection unit. The supercharger compresses and sucks air using energy of exhaust gas. The atmospheric pressure detection unit detects the atmospheric pressure in the operating environment. The coolant temperature detection unit detects a coolant temperature. The control unit controls a fuel injection amount so as not to exceed a minimum value among a reference limited injection amount, a boost pressure limited injection amount, and the limited injection amount. The reference limited injection amount is obtained based on an engine speed, the coolant temperature detected by the coolant temperature detection unit, and the atmospheric pressure detected by the atmospheric pressure detection unit. The boost pressure limited injection amount is determined based on the engine speed and the boost pressure of the supercharger. The limited injection amount is obtained based on the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio.

  Thereby, according to the various operation states of an engine, it can control appropriately so that the injection quantity of an engine may not become excessive. For example, when the engine is operated at a high altitude, the influence of the atmospheric pressure on the injection amount can be avoided. In addition, it is possible to prevent a decrease in output, clogging of the exhaust gas purification device, and the like due to a response delay of the turbocharger in a transition period such as acceleration or load insertion. When the air mass calculation accuracy is low because the amount of accumulated particulate matter is small, excessive restriction of the amount of fuel injection can be prevented, and thus reduction in engine output and engine stall can be avoided more preferably. On the other hand, when the calculation accuracy of the air mass is high because the amount of PM deposition is large, the insufficient limitation of the fuel injection amount can be prevented, so that the increase in the regeneration frequency of the exhaust gas purification device can be suitably avoided.

FIG. 1 is a schematic plan view of an engine according to a first embodiment of the present invention. Explanatory drawing which shows typically the flow of the intake of an engine, exhaust air, and fuel supply. The functional block diagram which shows the structure of ECU. The block diagram explaining the restriction | limiting of the fuel injection quantity in an engine. FIG. 5 is a block diagram illustrating in detail the excess air ratio limiting block of FIG. 4; Schematic explaining a correction coefficient curve. The block diagram which shows the excess air ratio restriction | limiting block in the engine of 2nd Embodiment in detail. Schematic explaining a correction coefficient map. The block diagram which shows the excess air ratio restriction | limiting block in a modification in detail.

  Next, embodiments of the present invention will be described with reference to the drawings. First, the outline of the engine 100 will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic plan view of an engine 100 according to an embodiment of the present invention. FIG. 2 is an explanatory view schematically showing the flow of intake, exhaust and fuel supply of the engine 100. As shown in FIG. FIG. 3 is a functional block diagram showing the configuration of the ECU 90. As shown in FIG.

  The engine 100 of the present embodiment is a diesel engine, and is mounted on, for example, a working machine, a ship, or the like. The engine 100 includes an engine body 10 and an ECU (engine control unit) 90 which is a control unit.

  The engine body 10 includes an intake unit 2 for drawing air from the outside, a cylinder (not shown) having a combustion chamber 3, and an exhaust unit 4 for discharging the exhaust gas generated in the combustion chamber 3 by the combustion of fuel to the outside. As the main configuration.

  The intake unit 2 includes an intake pipe 21 that is an intake passage. Further, the intake unit 2 includes a supercharger 22, an intake valve 27, and an intake manifold 28, which are disposed in order from the upstream side in the direction in which intake flows in the intake pipe 21.

  The intake pipe 21 is an intake passage, and is configured to connect the supercharger 22, the intake valve 27, and the intake manifold 28. The air drawn from the outside can flow into the intake pipe 21.

  As shown in FIG. 2, the supercharger 22 includes a turbine 23, a shaft 24 and a compressor 25. One end of the shaft 24 is connected to the turbine 23 and the other end is connected to the compressor 25. The turbine 23 is configured to rotate using exhaust gas. The compressor 25 coupled to the turbine 23 via the shaft 24 rotates as the turbine 23 rotates. Due to the rotation of the compressor 25, the air purified by the air cleaner (not shown) can be compressed and forcibly sucked.

  The intake valve 27 changes the cross-sectional area of the intake passage by adjusting the opening degree thereof in accordance with the control command from the ECU 90. Thus, the amount of air supplied to the intake manifold 28 can be adjusted through the intake valve 27.

  The intake manifold 28 is configured to distribute the air supplied from the intake pipe 21 according to the number of cylinders of the engine body 10 and supply the air to the combustion chambers 3 of the respective cylinders.

  An intercooler (not shown) is installed downstream of the compressor 25 of the supercharger 22 for cooling the compressed air sucked by the supercharger 22 by heat exchange with cooling water or flowing air (ie, wind). You may.

  In the combustion chamber 3, the air supplied from the intake manifold 28 is compressed, and fuel is injected into the high-temperature compressed air to spontaneously burn the fuel and push the piston to move. The power thus obtained is transmitted to an appropriate device downstream of the power via a crankshaft or the like.

  Further, the engine 100 of the present embodiment is provided with a not-shown cooling water circulation system for preventing the engine body 10 from being overheated by the combustion of fuel. The cooling water circulation system is configured to circulate the cooling water to a cooling jacket (not shown) or the like formed on a cylinder head or the like of the engine main body 10 and exchange heat with the cooling jacket or the like of the engine main body 10.

  Subsequently, a configuration for performing fuel supply and injection in the engine 100 of the present embodiment will be briefly described. As shown in FIG. 2, the engine 100 includes a fuel tank 81 for storing fuel, a fuel filter 82, a fuel pump 83, a common rail 84, and an injector 85.

  The fuel sucked by the fuel pump 83 passes through the fuel filter 82, thereby removing dust and dirt mixed in the fuel. Thereafter, the fuel is supplied to the common rail 84. The common rail 84 stores fuel at high pressure and distributes and supplies the fuel to the plurality of injectors 85.

  The injector 85 includes an injector solenoid valve (fuel injection valve) 86 for injecting fuel into the combustion chamber 3. The injector solenoid valve 86 opens and closes at a timing according to the instruction of the ECU 90, whereby the injector 85 injects the fuel into the combustion chamber 3. By controlling the opening and closing of the injector 85, the fuel injection amount can be adjusted.

  Exhaust gas generated by combustion of fuel in the combustion chamber 3 is discharged from the combustion chamber 3 to the outside of the engine main body 10 through the exhaust unit 4.

  The exhaust unit 4 includes an exhaust pipe 41 which is a passage for exhaust gas. Further, the exhaust unit 4 includes an exhaust manifold 42 and a DPF 60 which is an exhaust gas purification device, which are disposed in order from the upstream side in the direction in which the exhaust gas flows in the exhaust pipe 41.

  The engine body 10 is provided with an EGR device 50, and a part of the exhaust gas can be recirculated to the intake side via the EGR device 50, as shown in FIG. The EGR device 50 is provided with an EGR cooler 51 and an EGR valve 52. The EGR cooler 51 cools the exhaust gas returned to the intake air. The EGR valve 52 is configured to be able to adjust the amount of recirculation of the exhaust gas. The EGR device 50 with the cooling function configured in this way can lower the maximum combustion temperature, for example, at the time of high load operation of the engine 100, so the amount of NOx (nitrogen oxide) generated can be reduced.

  The exhaust pipe 41 is an exhaust gas passage, and is configured to connect the exhaust manifold 42 and the DPF 60. The exhaust gas discharged from the combustion chamber 3 can flow into the exhaust pipe 41.

  The exhaust manifold 42 guides the exhaust gas generated in each combustion chamber 3 to the exhaust pipe 41 so as to supply the exhaust gas to the turbine 23 of the turbocharger 22.

  In addition, an exhaust valve (not shown) capable of adjusting the amount of exhaust gas may be provided between the turbine 23 of the turbocharger 22 and the DPF 60.

  The DPF 60 is provided at the outlet of the exhaust pipe 41 as shown in FIGS. 1 and 2. The DPF 60 includes an elongated casing. The DPF 60 also includes an oxidation catalyst 61 and a soot filter 62. The oxidation catalyst 61 and the soot filter 62 are disposed inside the casing. The soot filter 62 is disposed downstream of the oxidation catalyst 61 in the direction in which the exhaust gas flows inside the casing. Exhaust gas introduced into the DPF 60 from the exhaust pipe 41 is purified by the soot filter 62 and then discharged out of the engine 100.

  The oxidation catalyst 61 is made of platinum or the like, and can promote the oxidation of carbon monoxide, nitrogen monoxide or the like contained in the exhaust gas. By the action of the oxidation catalyst 61, nitrogen monoxide in the exhaust gas is oxidized to unstable nitrogen dioxide. Then, the oxygen released as nitrogen dioxide returns to nitric oxide is supplied for the oxidation of PM trapped by the downstream soot filter 62.

  The soot filter 62 can filter exhaust gas by collecting particulate matter (PM: Particulate Matter) consisting of soot and the like in the exhaust gas. Further, the PM can be oxidized in the soot filter 62.

  Note that although the amount of PM deposited in the soot filter 62 gradually increases as the engine body 10 operates, the control (regeneration control) to burn and remove the PM is performed at an appropriate timing, thereby depositing You can reduce the amount. The deposition of PM on the soot filter 62 affects the reflux of the EGR gas through the increase of the exhaust pressure due to the increase of the flow resistance. In the following description, removing the PM deposited in the soot filter 62 by oxidizing it may be referred to as DPF regeneration.

  The ECU 90 illustrated in FIG. 2 includes a CPU that executes various arithmetic processing and control, and a ROM and a RAM as a storage unit, and is disposed in the engine main body 10 or in the vicinity thereof. In the present embodiment, as shown in FIG. 1, the ECU 90 is disposed in the engine body 10.

  The ECU 90 can obtain the rotational speed of the engine body 10, the intake flow rate (intake air amount), the excess air ratio λ, the exhaust flow rate, the exhaust temperature, etc. based on the detection results output from various detection units and sensors. it can. And ECU90 can control the engine main body 10 based on the said information regarding the state of the engine main body 10 acquired from various sensors.

  As described above, the excess air ratio λ is obtained by dividing the air-fuel ratio by the stoichiometric air-fuel ratio. If the excess air ratio is too small (if the amount of fuel is too large), this may cause the generation of unburned fuel and black smoke. Therefore, in the present embodiment, the lower limit is set so that the excess air ratio λ does not become too small. doing. The ECU 90 obtains the lower limit value (λ lower limit value) of the excess air ratio λ by calculating based on the rotational speed and the fuel injection amount. Further, the ECU 90 can correct the above-described λ lower limit value based on the deposition amount of PM.

  As a detection unit and sensor for acquiring information on the state of the engine body 10, for example, a rotation speed detection unit 91, a fuel injection amount detection unit 92, a cooling water temperature sensor 93, an atmospheric pressure sensor 71, an intake pressure sensor 72, The exhaust temperature sensor 75, the exhaust pressure sensor 74, the differential pressure sensor 76, the oxidation catalyst temperature sensor 77, and the soot filter temperature sensor 78 can be mentioned. Each sensor will be described below.

  The rotation speed detection unit 91 can be configured, for example, as a crank sensor that detects the rotation of a crankshaft (not shown) of the engine body 10.

  The fuel injection amount detection unit 92 can be configured to be obtained, for example, by calculating the fuel injection amount based on the command value from the ECU 90 to the injector solenoid valve 86 described above.

  The coolant temperature sensor 93 detects the temperature of the coolant of the engine 100, and is configured as a temperature sensor disposed at an appropriate position of the coolant path in the coolant circulation system described above.

  The atmospheric pressure sensor 71 detects the atmospheric pressure of the environment when the engine 100 is in operation. The pressure sensor is configured as a pressure sensor disposed at an appropriate position of the engine 100.

  The intake pressure sensor 72 detects the pressure of the gas (EGR mixture) in the intake manifold 28. The intake temperature sensor 73 detects the temperature of the gas in the intake manifold 28.

  The exhaust pressure sensor 74 detects the pressure of the gas (exhaust) in the exhaust manifold 42. The exhaust temperature sensor 75 detects the temperature of the gas in the exhaust manifold 42.

  The differential pressure sensor 76 detects, in the DPF 60, a pressure difference between the upstream side of the soot filter 62 (the downstream side of the oxidation catalyst 61) and the downstream side of the soot filter 62. The ECU 90 can calculate the deposition amount of PM deposited on the soot filter 62 based on the detection result of the differential pressure sensor 76. Note that the method of calculating the deposition amount of PM is not limited to this, and for example, the deposition amount of PM can be estimated and obtained based on the operation history of the engine 100 or the like.

  The oxidation catalyst temperature sensor 77 detects the temperature near the inlet of the DPF 60 (upstream of the oxidation catalyst 61). That is, the temperature of the exhaust gas at the inlet of the DPF 60 can be detected using the oxidation catalyst temperature sensor 77.

  The soot filter temperature sensor 78 detects the temperature between the oxidation catalyst 61 and the soot filter 62 (upstream of the soot filter 62).

  As shown in FIG. 3, a plurality of control information (specifically, control map and control curve) for calculating various parameters for controlling the operation of the engine 100 are stored in the ECU 90. As an example of control information, a base restriction map for calculating a value (base restriction injection amount) serving as a base for restriction of a fuel injection amount, an atmospheric pressure restriction map for calculating an atmospheric pressure restriction injection amount, a boost pressure restriction Boost pressure limitation map for calculating the injection amount, λ lower limit map for calculating the lower limit (λ lower limit) of the allowable excess air ratio λ, correction standard for calculating the correction amount of λ lower limit An amount map and a correction coefficient curve etc. can be mentioned. The details of each control information will be described later.

  Next, in the engine 100 of the present embodiment, setting of the maximum fuel injection amount related to control of the fuel injection amount in the ECU 90 will be described. FIG. 4 is a block diagram for explaining the limitation of the fuel injection amount in engine 100.

  The ECU 90 of the engine 100 according to the present embodiment is a base stored in advance in the ECU 90 based on the rotational speed of the engine 100 detected by the rotational speed detection unit 91 and the coolant temperature detected by the coolant temperature sensor 93. The base limit injection amount is determined using the limit map. This base restriction map can be expressed as a two-dimensional table in which the maximum injection amount is associated with the combination of the rotational speed and the coolant temperature.

  Further, the ECU 90 obtains the atmospheric pressure restriction injection amount using the atmospheric pressure restriction map stored in advance in the ECU 90 based on the rotational speed of the engine 100 and the atmospheric pressure detected by the atmospheric pressure sensor 71. This atmospheric pressure restriction map can be expressed as a two-dimensional table in which the maximum injection amount is associated with the combination of the rotational speed and the atmospheric pressure. Then, the ECU 90 calculates the reference limited injection amount by subtracting the atmospheric pressure limited injection amount from the base limited injection amount.

  Furthermore, the ECU 90 obtains a boost pressure limited injection amount using a boost pressure limit map stored in advance in the ECU 90 based on the rotational speed of the engine 100 and the boost pressure of the supercharger 22. This boost pressure restriction map can be expressed as a two-dimensional map in which the combination of the rotation speed and the boost pressure is associated with the maximum injection amount.

  Furthermore, the ECU 90 calculates the lower limit value (λ lower limit value) of the excess air ratio λ in the excess air ratio restriction block described later, and substitutes the value of the air mass into the lower limit value of the excess air ratio to obtain the maximum injection amount. The λ limited injection amount (limited injection amount) which is The details of the calculation of the λ limited injection amount will be described later.

  Thereafter, the ECU 90 selects the minimum value among the reference limited injection amount, the boost pressure limited injection amount, and the λ limited injection amount, and sets the minimum value as the maximum fuel injection amount of the engine 100. Then, the ECU 90 controls the fuel injection amount of the engine 100 so as not to exceed the maximum fuel injection amount. As described above, the engine 100 can be operated by appropriately limiting the fuel injection amount from various points of view.

  Subsequently, the calculation of the λ limited injection amount based on the lower limit value of the excess air ratio λ will be described in detail with reference to FIG. FIG. 5 is a block diagram showing the excess air ratio limiting block of FIG. 4 in detail. FIG. 6 is a schematic diagram for explaining the correction coefficient curve.

  As shown in FIG. 5, the excess air ratio limiting block comprises a basic limiting block and a correction block.

  In the basic limiting block, the lower limit (λ lower limit) of the allowable excess air ratio λ is obtained using the λ lower limit map stored in advance in the ECU 90 based on the rotational speed of the engine 100 and the fuel injection amount. The λ lower limit map can be expressed as a two-dimensional table in which the λ lower limit is associated with the combination of the rotational speed and the fuel injection amount.

  In the engine 100 of the present embodiment, the λ lower limit value in the above λ lower limit value restriction map is set intentionally smaller than a value which should be originally determined corresponding to the rotation speed of the engine 100 and the fuel injection amount. . Details will be described later.

  In the correction block, based on the rotational speed of the engine 100 and the fuel injection amount, the correction reference amount map, which is stored in advance in the ECU 90, is used to obtain a correction reference amount which is a basic value for correcting the λ lower limit value. . The correction reference amount map can be expressed as a two-dimensional table in which the correction reference amount is associated with the combination of the rotational speed and the fuel injection amount.

  Further, in the correction block, a correction coefficient is determined using a correction coefficient curve stored in advance in the ECU 90 based on the amount of PM deposition in the DPF 60 obtained by calculation. The correction coefficient curve can be expressed as a one-dimensional table in which the PM deposition amount is associated with the correction coefficient.

  Thereafter, in the correction block, the λ correction amount is obtained by multiplying the correction reference amount by the correction coefficient.

  Then, the ECU 90 corrects the λ lower limit value obtained in the basic restriction block by adding the λ correction amount obtained in the correction block, and obtains the corrected λ lower limit value. The corrected λ lower limit value obtained is output from the excess air ratio limiting block.

The corrected lower limit λ is a general equation for determining the excess air ratio λ;
λ = (Air / Fuel) / (Stoichiometric air fuel ratio)
Is used to determine the upper limit value of Fuel using Specifically, while substituting the corrected λ lower limit value into the part of λ in the above equation, Air is calculated by a known method based on exhaust pressure, intake pressure, etc. The amount of oxygen contained in the air (air mass) is substituted. Thereby, the upper limit value of Fuel (that is, the λ limited injection amount Q) can be obtained.

  Here, the amount of oxygen contained in the mixture in the cylinder is affected by the ratio of EGR gas in the mixture. The amount of EGR gas recirculated from the exhaust side to the intake side can be calculated with relatively good accuracy if the difference between the exhaust pressure and the intake pressure is large, but if the difference between the exhaust pressure and the intake pressure is small, the calculation accuracy is too low I can not expect it. In this way, there may be situations where it can be expected that the air mass (the term Air in the above equation) can be calculated with high accuracy, and situations where it can not.

  In the above equation, if the calculation accuracy of the air mass (Air) is low, the upper limit value of Fuel may be excessive or excessive. In particular, if there is an error on the positive side of the calculated value of air mass (Air), the upper limit value of Fuel becomes too small and the output of the engine 100 decreases, and in the worst case, an engine stall may occur.

  Therefore, it is conceivable to set the lower limit value of the excess air ratio λ intentionally smaller than the value that should be originally, so that the decrease in the output of the engine 100 does not occur even if the calculation accuracy of the air mass decreases as described above. . By securing a certain margin in this manner, it is possible to prevent the upper limit value of the fuel injection amount Fuel from becoming too small even if a positive error occurs in the calculated value of the air mass (Air). The workability of the mounted device can be maintained well.

  However, the calculated value of the air mass (Air) does not always have an error on the positive side. Therefore, if the lower limit value of λ is simply reduced as described above, for example, if there is almost no error in the calculated value of the air mass (Air), the upper limit value of the fuel injection amount Fuel is calculated more. Due to the insufficient injection amount limitation, a large amount of PM may be generated, and the DPF 60 may have to be regenerated frequently.

  In this respect, in the engine 100 according to the present embodiment, the λ lower limit value determined in the basic restriction block is more intentionally set than the value to be originally determined corresponding to the rotational speed of the engine 100 and the fuel injection amount as described above. It is set small. On the other hand, in the correction block, if it is expected that the calculation accuracy of the air mass is relatively high because the PM deposition amount in the DPF 60 is large and the exhaust pressure is large, the λ lower limit value should be increased. Correction). Thus, the fuel injection amount can be appropriately limited in accordance with the operating condition of engine 100.

  Specifically describing the operation of the correction block described above, the ECU 90 determines a basic correction amount (correction reference amount) of the λ lower limit value using the correction reference amount map based on the engine speed and the fuel injection amount. . Further, the ECU 90 obtains a correction coefficient using the correction coefficient curve based on the PM deposition amount. Then, the ECU 90 obtains the λ correction amount by multiplying the correction reference amount by the correction coefficient.

  FIG. 6 shows a correction coefficient curve for obtaining the correction coefficient based on the PM deposition amount. As shown in FIG. 6, when the deposition amount of PM is less than a fixed amount, it is expected that the calculation accuracy of the air mass will be low because the exhaust pressure does not increase so much, in order to prevent the excessive limitation of the injection amount. In addition, the correction coefficient is set such that a value close to the λ lower limit value (a value lower than the value to be originally present) obtained in the basic restriction block is output from the excess air ratio restriction block. On the other hand, if the deposition amount of PM is a certain amount or more, it is expected that the calculation accuracy of the air mass can be secured to a certain degree because the exhaust pressure increases, so it is inherent (instead of the λ lower limit value determined in the basic restriction block) The correction factor is set such that a value close to the power λ lower limit value is output from the excess air ratio limiting block.

  Thus, the engine 100 according to the present embodiment appropriately limits the fuel injection amount in terms of the excess air ratio λ while considering that the calculation accuracy of the air mass may change according to the operating state of the engine 100. Can. That is, when the calculation accuracy of the air mass is low, the upper limit value of the fuel injection amount is calculated using the lower limit (or the value near it) of the excess air ratio λ intentionally set small, while the calculation accuracy of the air mass In the case where is high, the upper limit value of the fuel injection amount can be calculated using the lower limit value (or the value in the vicinity thereof) of the excess air ratio λ which should be originally. Therefore, it is possible to prevent a decrease in output when the air mass calculation accuracy is low, and to preferably avoid an increase in the regeneration frequency of the DPF 60 due to a large amount of PM generation when the air mass calculation accuracy is high.

  As described above, the engine 100 according to the present embodiment includes the DPF 60 and the ECU 90. The DPF 60 purifies the exhaust gas. The ECU 90 determines the λ limited injection amount, which is the upper limit value of the fuel injection amount, based on the lower limit value (λ lower limit value) of the excess air ratio λ. The λ lower limit value differs depending on the deposition amount of PM collected by the DPF 60.

  As described above, by making the λ lower limit value different based on the deposition amount of PM, it is possible to appropriately limit the fuel injection amount in consideration of the fact that the calculation accuracy of the air mass may change depending on, for example, the exhaust pressure. For example, when the deposition amount of PM is small and it is expected that the calculation accuracy of the air mass is low, lowering the λ lower limit intentionally reduces the output due to the fuel injection amount being excessively limited, engine stall, etc. It can be prevented. On the other hand, when the deposition amount of PM is large and the calculation accuracy of the air mass is expected to be high, setting the λ lower limit value to a value that should be originally (or a value in the vicinity) It is possible to avoid the generation of fuel and the increase of the regeneration frequency of the DPF 60.

  Further, in the engine of the present embodiment, the ECU 90 corrects the λ lower limit value based on the deposition amount of PM collected by the DPF 60. The ECU 90 obtains the λ limited injection amount using the corrected λ lower limit value.

  As described above, the fuel injection amount can be appropriately limited according to the situation by correcting the λ lower limit value according to the deposition amount of PM accumulated in the DPF 60.

  Further, in the engine 100 of the present embodiment, the ECU 90 obtains the λ lower limit value (before correction) based on the rotational speed of the engine 100 and the fuel injection amount. Further, the ECU 90 obtains the correction reference amount of the λ lower limit value based on the rotation speed of the engine 100 and the fuel injection amount, and obtains the correction coefficient based on the deposition amount of PM. Then, the ECU 90 corrects the λ lower limit value using a value obtained by multiplying the correction reference amount by the correction coefficient.

  Thus, the λ lower limit value can be appropriately corrected in consideration of the rotational speed of the engine 100, the fuel injection amount, and the deposition amount of PM in a combined manner. Therefore, a reduction in engine 100 output, engine stall, or clogging of the DPF 60 can be further suitably prevented.

  In addition, the engine 100 of the present embodiment includes a supercharger 22, an atmospheric pressure sensor 71, and a cooling water temperature sensor 93. The turbocharger 22 compresses and sucks air using energy of exhaust gas. The atmospheric pressure sensor 71 detects atmospheric pressure in the operating environment. The coolant temperature sensor 93 detects the coolant temperature. The ECU 90 controls the fuel injection amount so as not to exceed the minimum value among the reference limited injection amount, the boost pressure limited injection amount, and the λ limited injection amount. The reference limited injection amount is obtained based on the rotational speed of the engine 100, the coolant temperature detected by the coolant temperature sensor 93, and the atmospheric pressure detected by the atmospheric pressure sensor 71. The boost pressure limited injection amount is determined based on the engine 100 speed and the boost pressure of the supercharger 22. The λ limited injection amount is obtained based on the λ lower limit value.

  Thereby, according to the various operation states of an engine, it can control appropriately so that the injection quantity of an engine may not become excessive. For example, when the engine is operated at a high altitude, the influence of the atmospheric pressure on the injection amount can be avoided. In addition, it is possible to prevent a decrease in output, clogging of the exhaust gas purification device, and the like due to a response delay of the turbocharger in a transition period such as acceleration or load insertion. When the calculation accuracy of the air mass is low because the amount of PM deposition is small, it is possible to prevent the fuel injection amount from being excessively limited, and thus it is possible to more preferably avoid the reduction in output and engine stall. On the other hand, when the calculation accuracy of the air mass is high because the amount of PM deposition is large, the insufficient limitation of the fuel injection amount can be prevented, so that the increase in the regeneration frequency of the exhaust gas purification device can be suitably avoided.

  Next, a second embodiment will be described. FIG. 7 is a block diagram showing the excess air ratio limiting block in the engine of the second embodiment in detail. FIG. 8 is a schematic diagram for explaining the correction coefficient map. In the description of the present embodiment, members that are the same as or similar to the above-described embodiment may be assigned the same reference numerals in the drawings, and descriptions thereof may be omitted.

  As is known, when the intake air temperature is high or low, the possibility that black smoke is generated or the exhaust gas temperature is excessively increased. Taking this point into consideration, the engine of the present embodiment is configured to correct the λ lower limit value based on the intake air temperature, in addition to the PM deposition amount described above.

  Specifically, in the present embodiment, instead of the correction coefficient curve, the correction coefficient for multiplying the correction reference amount is the PM deposition amount obtained by calculation, and the intake air temperature detected by the intake air temperature sensor 73 , Using the correction coefficient map based on. The correction coefficient map can be expressed as a two-dimensional table in which the correction coefficient is associated with the combination of the PM deposition amount and the fuel injection amount. The processing other than the above is the same as that of the above-described first embodiment.

  FIG. 8 schematically shows a correction coefficient map for obtaining a correction coefficient based on the PM deposition amount and the intake air temperature. As shown in FIG. 8, the correction coefficient has a value closer to the λ lower limit value (a value lower than the value that should be present) obtained in the basic limit block as the deposition amount of PM decreases and as the intake air temperature decreases. It is set to be output from the excess air ratio limiting block. In addition, the correction factor is a value close to the λ lower limit which should be inherent (rather than the λ lower limit determined by the basic limit block) as the PM deposition amount is larger and the intake air temperature is higher is the excess air limit block It is set to be output from. As a result, when the intake air temperature becomes high, the λ lower limit value is corrected to the increase side, so the fuel injection amount is sufficiently limited, and the generation of black smoke and the like can be prevented.

  As described above, the engine of the present embodiment includes the intake air temperature sensor 73. An intake air temperature sensor 73 detects an intake air temperature. The ECU 90 obtains a correction coefficient based on the amount of PM deposition and the intake air temperature detected by the intake air temperature sensor 73.

  Thus, the λ lower limit value can be corrected in consideration of the intake air temperature as well, so that generation of unburned fuel or black smoke can be prevented, for example, when the intake air temperature is high.

  Next, a modification of the first embodiment will be described. FIG. 9 is a block diagram showing the excess air ratio limiting block in the modification in detail. In the description of the present modification, the same or similar members as or to those of the above-described embodiment may be denoted by the same reference numerals as those of the embodiment, and the description thereof may be omitted.

  In the engine of the present modification, a plurality of λ lower limit maps for obtaining the λ lower limit value based on the engine speed and the fuel injection amount are prepared in advance in the air excess rate restriction block according to the PM deposition amount. It is done. In these λ lower limit value maps, λ lower limit values corresponding to values corrected by the correction block in the first embodiment described above are stored.

  In the example of FIG. 9, the λ lower limit value map is stored in the ECU 90 in each of three stages: when the deposition amount of PM is large (more), middle (middle), and smaller (less). The ECU 90 selects the λ lower limit map corresponding to the deposition amount of PM from the three λ lower limit maps according to the deposition amount of PM obtained from the detection result of the differential pressure sensor 76, and the λ lower limit map Is used to find the λ lower limit value based on the engine speed and the fuel injection amount.

  By switching the λ lower limit map according to the PM deposition amount in this manner, substantially the same effect as the first embodiment described above in which the λ lower limit is corrected according to the PM deposition amount can be achieved. The number of λ lower limit maps is not limited to three, and may be two or four or more. Also, for example, when the deposition amount of PM is intermediate between a small amount and a medium amount, the value obtained by a small λ lower limit value map and the value obtained by a λ lower limit value map may be appropriately interpolated to obtain a λ lower limit value good.

  As described above, in the engine of the present modification, the ECU 90 determines in advance the λ lower limit value map for obtaining the λ lower limit value based on the engine speed and the fuel injection amount according to the PM deposition amount. Multiple are stored. The ECU 90 obtains the λ lower limit value based on the λ lower limit value map corresponding to the deposition amount of PM among the plurality of stored λ lower limit value maps.

  Thereby, the fuel injection amount can be appropriately limited in accordance with the situation.

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

  In the first embodiment and the second embodiment, the λ lower limit value stored in the λ lower limit value map of the basic restriction block is intentionally set smaller than the value that should be originally. However, it is also possible to set the λ lower limit value that should be present in the λ lower limit map as it is. In this case, on the correction block side, the λ lower limit value is decreased when the PM deposition amount is small, and the λ correction amount is output so that the λ lower limit value is hardly decreased when the PM deposition amount is large. Just do it.

  The correction coefficient curve of FIG. 6 and the correction coefficient map of FIG. 8 are an example and can be variously changed.

  The various control information (for example, the λ lower limit map, the correction reference amount map, the correction coefficient curve, the correction coefficient map) is not limited to being expressed in the form of a map and a curve. It can also be configured to

  In the above embodiment and the like, the lower limit value of the excess air ratio λ is obtained and corrected in the excess air ratio restriction block, and the limited injection amount is calculated based on this. However, instead of the lower limit value of the excess air ratio λ, the upper limit value of the fuel / air ratio can be obtained and corrected to calculate the limited injection amount. Specifically, the ECU 90 is provided with a fuel / air ratio limiting block instead of the air excess ratio limiting block, and the upper limit value of the fuel / air ratio is acquired by a map etc. in the basic limiting block among the fuel / air ratio limiting blocks. The upper limit value of the fuel-air ratio may be corrected by the correction block, and the limited injection amount (fuel-air ratio limited injection amount) may be determined from the upper limit value of the fuel-air ratio. The technical meaning is the same whether using the upper limit value of the excess air ratio or the lower limit value of the fuel / air ratio.

  The engine 100 of the present invention can also be applied to machines other than work vehicles and ships (for example, generators).

22 Turbocharger 60 DPF (Exhaust gas purification system)
71 Atmospheric pressure sensor (atmospheric pressure detector)
72 Intake pressure sensor (intake temperature detection unit)
90 ECU (control unit)
93 Cooling water temperature sensor (cooling water temperature detector)
100 engines

Claims (6)

An exhaust gas purification device for purifying exhaust gas;
A control unit which obtains a limited injection amount which is an upper limit value of a fuel injection amount based on a lower limit value of an excess air ratio or an upper limit value of a fuel-air ratio;
Equipped with
An engine, wherein the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio differs at least according to the deposition amount of the particulate matter collected by the exhaust gas purification device. The engine according to claim 1, wherein
The control unit corrects the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio based on the deposition amount of the particulate matter collected by the exhaust gas purification device,
The control unit determines the limited injection amount by using a lower limit value of the excess air ratio or an upper limit value of a fuel-air ratio after the correction. The engine according to claim 2, wherein
The control unit determines a lower limit value of the excess air ratio or an upper limit value of the fuel-air ratio based on an engine speed and a fuel injection amount.
The control unit determines a correction reference amount of the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio based on the engine speed and the fuel injection amount, and at least a correction coefficient of the deposition amount of the particulate matter Based on
The control unit corrects the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio using a value obtained by multiplying the correction reference amount by the correction coefficient. The engine according to claim 3, wherein
It has an intake temperature detection unit that detects the intake temperature,
The control unit determines the correction coefficient based on at least the deposition amount of the particulate matter and the intake air temperature detected by the intake air temperature detection unit. The engine according to claim 1, wherein
A plurality of pieces of information for obtaining the lower limit value of the excess air ratio or the upper limit value of the fuel / air ratio based on the engine speed and the fuel injection amount are stored in advance in the control unit according to the deposition amount of the particulate matter. And
The control unit is characterized in that the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio is obtained based on the information according to the deposition amount of the particulate matter among the plurality of stored information. And an engine. The engine according to any one of claims 1 to 5, wherein
A supercharger that uses the energy of exhaust gases to compress and inhale air;
An atmospheric pressure detection unit that detects atmospheric pressure in the operating environment;
A coolant temperature detection unit that detects coolant temperature;
Equipped with
The control unit
A reference limited injection amount determined based on an engine rotational speed, the coolant temperature detected by the coolant temperature detection unit, and the atmospheric pressure detected by the atmospheric pressure detection unit;
A boost pressure limited injection amount determined based on the engine speed and the boost pressure of the supercharger,
The limited injection amount determined based on the lower limit value of the excess air ratio or the upper limit value of the fuel-air ratio;
An engine characterized by controlling a fuel injection amount so as not to exceed a minimum value of the above.

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