Control system of an internal combustion engine of a construction machine

Abstract

Internal combustion engine control system of a construction machine (1) on which an internal combustion engine (10) with a loader (14) is mounted, comprising: a boost pressure control unit (14C, 14D) configured to control boost pressure; and a control unit (50) which is configured to determine a required torque of the construction machine (1), to set a target boost pressure to control the internal combustion engine (10) based on the determined required torque or a required torque-related amount calculated based on the determined required torque, and to control the boost pressure control (14C, 14D) such that an actual boost pressure approaches the target boost pressure, characterized by the fact that the control (50) calculates the demand torque-related amount based on the demand torque such that the demand torque-related amount increases when the determined demand torque increases, the control (50) adjusts the target boost pressure based on the requested torque or the calculated request-torque-related amount such that the target boost pressure increases while the requested torque or the calculated request-torque-related amount increases, the control (50) performs a gradual reduction process such that the target boost pressure is gradually reduced when the target boost pressure is reduced from a current target boost pressure to a reduced target boost pressure in accordance with a reduced demand torque or a reduced demand torque-related amount when the demand torque or demand torque-related amount is changed to decrease, the control (50) calculates an indicator for maintaining the target boost pressure based on the requested torque or the requested torque-related amount, which relates to an operating pattern of the construction machine (1), the control (50) performs the gradual reduction process by which the target boost pressure is gradually reduced when the indicator for maintaining the target boost pressure is equal to or greater than a gradual reduction threshold and the request torque or the request torque-related amount is changed to be reduced, and the control (50) does not perform the gradual reduction process and sets the reduced target boost pressure as the target boost pressure when the indicator to maintain the target boost pressure is less than the gradual reduction threshold and the request torque or the request torque-related amount is changed to be reduced.

Description

[0001] The present disclosure relates to an internal combustion engine control system that controls an internal combustion engine with a loader mounted on a construction machine. STATE OF THE ART

[0002] Japanese Patent Application Publication No. JP 2016-223285 A discloses a bucket device that drives a hydraulic pump and an electric generator using an internal combustion engine with a loader, describing a hybrid-type bucket device that operates an arm and boom with hydraulic oil and a rotating mechanism with electricity. When an arm operating lever is operated, a controller immediately operates the electric generator driven by the internal combustion engine for a short period of time to apply a small load to the internal combustion engine before applying a large load to the hydraulic pump to increase the engine's fuel injection amount.As a result, a drop in the engine speed when a large load is applied to the hydraulic pump is suppressed by starting to increase the boost pressure by increasing the actual hydraulic pressure load before a large load is applied to the hydraulic pump.

[0003] When a drop in the engine speed occurs in construction machinery that requires high torque, such as during excavation, sufficient torque may not be generated, resulting in reduced work efficiency due to reduced operability. In construction machinery equipped with an internal combustion engine with a supercharger, to generate sufficient torque while maintaining the engine speed, sufficient air must be supplied to the engine by increasing the boost pressure and fuel must be injected according to the required torque.In the bucket device of the publication, a small load is applied to the internal combustion engine by the electric generator, which can be promptly driven immediately before the load on the hydraulic pump increases to start increasing the boost pressure at an earlier time than the normal time, thereby suppressing a drop in the speed of the internal combustion engine.

[0004] However, in the case where the successive operation is performed in which the high-load operation and the low-load operation are alternately repeated, the controller controls the boost pressure such that a high boost pressure is provided during the high-load operation and a lower boost pressure is provided during the low-load operation. It is noted that a predetermined period of time is required to increase the boost pressure from the low boost pressure during the low-load operation to the high boost pressure during the high-load operation. Therefore, even if the controller using the vane device described in the publication starts increasing the boost pressure at an earlier timing than the normal timing, a drop in the engine speed may occur in the above successive operation when the low-load operation is switched to the high-load operation.In particular, in the construction machine operated by an experienced operator, high-load operation and low-load operation are often alternated in a short period of time, so that a drop in speed is likely to occur when the low-load operation is switched to the high-load operation.

[0005] The present disclosure, made in light of the above-described problem, is directed to providing an engine control system of a construction machine on which an engine with a supercharger is mounted, which suppresses a drop in the rotational speed of the engine that occurs when the low load operation is switched to the high load operation even when the successive operation is performed in which the high load operation and the low load operation are alternately repeated.

[0006] DE 10 2008 057 929 A1 discloses a control method for an internal combustion engine of a vehicle, comprising a supercharging device for building up an intake manifold pressure in an intake manifold of the internal combustion engine, and a variable intake valve control for varying an intake cross-section from the intake manifold into a combustion chamber of the internal combustion engine. The intake manifold is arranged between the supercharging device and the intake cross-section. The control method comprises the steps of building up an overpressure in the intake manifold upstream of the intake cross-section, and opening the intake cross-section when a positive load step is required according to a driver's driving behavior in order to achieve rapid filling of the combustion chamber. SUMMARY

[0007] The present object is achieved by the subject matter claimed in independent claim 1; alternatively, the present object is achieved by the subject matter claimed in independent claim 5. The dependent claims show preferred developments of the present invention.

[0008] According to one aspect of the present disclosure, an engine control system of a construction machine is provided on which an internal combustion engine with a supercharger is mounted. The internal combustion engine control system includes a boost pressure controller configured to control a boost pressure, and a controller configured to determine a demand torque of the construction machine, set a target boost pressure, control the internal combustion engine based on the determined demand torque or a demand torque-related amount calculated based on the determined demand torque, and control the boost pressure control such that an actual boost pressure approaches the target boost pressure. The controller calculates the demand torque-related amount based on the demand torque such that the demand torque-related amount increases as the demand torque increases.The controller sets the target boost pressure based on the request torque or the calculated request-torque-related amount such that the target boost pressure increases as the request torque or the request-torque-related amount increases. The controller executes a gradual decrease process such that the target boost pressure is gradually decreased as the target boost pressure decreases from the current target boost pressure to a decreased target boost pressure corresponding to a decreased request torque or a decreased request-torque-related amount.

[0009] Further aspects and advantages of the present disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing an example of high-load operations (excavation operation) of a successive operation in which a construction machine alternately repeats a high-load operation and a low-load operation; Fig. 2 is a view showing an example of the high-load operations (machine rotation operation) of the successive operation performed by the construction machine; Fig. 3 is a view showing an example of the low-load operations (bucket turning operation) of the successive operation performed by the construction machine; Fig. 4 is a view showing the configurations of an internal combustion engine and a hydraulic system mounted on the construction machine; Fig. 5 is a flowchart describing an example of control processes executed by an internal combustion engine control device (a controller) according to a first embodiment; Fig. 6 is a diagram showing examples of operation waveforms when the successive operation is carried out according to the control process of the Fig. 5 shown first embodiment; Fig. 7 is a diagram showing examples of operation waveforms when the successive operation is performed according to the control process of a second embodiment; and Fig. Fig. 8 is a diagram showing examples of operation waveforms when the successive operation is performed by a conventional control system, compared with the first embodiment in Fig. 6 and the second embodiment in Fig. 7. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0010] [An example of the successive operation of a construction machine 1 ( Fig. 1 to Fig. 3) and the configuration of an internal combustion engine and a hydraulic system mounted on the construction machine 1 ( Fig. 4)]

[0011] The following describes an embodiment of the present disclosure with reference to the accompanying drawings. As an example of the construction machine 1, the Fig. 1, Fig. 2 and Fig. 3 will be described in the description of the present embodiment. The construction machine 1 includes a lower traveling body 81 with a crawler, an upper rotating body 82, a boom 83, an arm 84, a bucket 85, and the like.

[0012] Fig. 1, Fig. 2 and Fig. 3 show examples of an excavation operation, a body rotation operation and a bucket rotation operation of the construction machine 1, respectively. For example, an operator operates the construction machine 1 to move sand and gravel loaded on the bucket 85 to a carrier of a transport vehicle by operating the Fig. 1 shown excavation operation (an example of high-load operations), in which sand and gravel are loaded onto the bucket 85, the body rotation operation (an example of high-load operations), in which the bucket 85 is moved to a position above the carrier of the transport vehicle, and the bucket rotation operation (an example of low-load operations), in which the sand and gravel loaded onto the bucket 85 is moved to the carrier of the transport vehicle. By repeating the in Fig. 1 to Fig. The operations shown in Figure 3 are successive operations in which high-load operations and low-load operations occur one after another. The high-load operation and low-load operation correspond to the operation pattern of the construction machine of the present disclosure.

[0013] At the Fig. 1 to Fig. 3, the crawler of the lower traveling body 81 is driven by a travel hydraulic motor 26A ( Fig. 4). The upper rotary body 82 is driven by a rotary hydraulic motor 26B ( Fig. 4) relative to the lower traveling body 81. The boom 83 is rotated in the vertical direction by a boom cylinder 25A relative to the upper rotating body 82, the arm 84 is rotated in the vertical direction by an arm cylinder 25B relative to the boom 83, and the bucket 85 is rotated in the vertical direction by a bucket cylinder 25C relative to the arm 84. The operator operates control components (e.g., a boom lever 23A, an arm lever 23B, and a bucket lever 23C, which are in Fig. 4) provided on an operator's seat to move the construction machine 1 using the crawler of the lower traveling body 81, to rotate the upper rotating body 82, and to operate the boom 83, the arm 84, and the bucket 85.

[0014] The following describes with reference to Fig. 4 an example of the configuration of the internal combustion engine and the hydraulic system mounted on the construction machine 1. Fig. 4 shows an example of the control system that controls the internal combustion engine 10 having a turbocharger 14 for construction machinery. Fig. The control system shown in Fig. 4 includes the engine 10 with the turbocharger 14, a hydraulic pump 21 driven by the engine 10, a valve unit 22 to which hydraulic oil is supplied from the hydraulic pump 21, various control components (e.g., a boom lever 23A) through which operations are input to the valve unit 22, various hydraulic oil drive components (e.g., a boom cylinder 25A), an engine control device 50 that controls the engine 10, and an engine control device 60 that controls the hydraulic pump 21. Note that the turbocharger 14 corresponds to the supercharger of the present embodiment.

[0015] First, the internal combustion engine 10 is described starting from the intake side to the exhaust side of the internal combustion engine 10. The Fig. The internal combustion engine 10 shown in Figure 4 is a diesel engine. Note that parts arranged downstream of a diesel particulate filter (DPF) 43 in an exhaust passage, such as a selective reduction catalyst that purifies nitrogen oxides (NOx), are omitted from the following description.

[0016] An intake air flow rate detector 31 (e.g., an intake air flow rate sensor) is arranged at an inlet of an intake pipe 11A. The intake air flow rate detector 31 outputs a detection signal indicative of the flow rate of intake air of the internal combustion engine 10 to the internal combustion engine control device 50.

[0017] An outlet of the intake pipe 11A is connected to an inlet of a compressor 14B, and an outlet of the compressor 14B is connected to an inlet of the intake pipe 11B. The compressor 14B is rotatable integrally with a turbine 14A, which is driven to rotate by exhaust gas and compresses intake air drawn from the intake pipe 11A to deliver it to the intake pipe 11B. Accordingly, supercharging is achieved. The boost pressure is measured by a compressor downstream pressure detector 32 disposed in the intake pipe 11B downstream of the compressor 14B. The compressor downstream pressure detector 32 is provided, for example, as a pressure sensor and outputs a measurement signal indicative of the pressure in the intake pipe 11B to the engine control device 50.An inlet of the intake pipe 11B is connected to the above-described compressor 14B, and an outlet of the intake pipe 11B is connected to an intake manifold 11C. The intake manifold 11C is connected to an inlet of the internal combustion engine 10. Note that the internal combustion engine control device 50 includes an atmospheric pressure detector 37 (e.g., an atmospheric pressure sensor) and can determine a pressure ratio (a boost pressure) by dividing the pressure measured by the compressor downstream pressure detector 32 by the atmospheric pressure measured by the atmospheric pressure detector 37.

[0018] The internal combustion engine 10 has a plurality of cylinders, each having an injector, namely injectors 41A, 41B, 41C, 41D. The injectors 41A, 41B, 41C, 41D are driven by control signals from the internal combustion engine control device 50 and inject fuel into their corresponding cylinders. The internal combustion engine 10 rotates the hydraulic pump 21.

[0019] The internal combustion engine 10 further includes a rotation detection device 33 and a coolant temperature detector 34. The rotation detection device 33 is provided, for example, by a rotation sensor and outputs a measurement signal indicative of the rotational speed of a crankshaft of the internal combustion engine 10 (i.e., the rotational speed of the engine) to the internal combustion engine control device 50. The coolant temperature detector 34 is provided, for example, as a temperature sensor, measures the temperature of the coolant circulating in the internal combustion engine 10, and outputs a measurement signal indicative of the measured coolant temperature to the internal combustion engine control device 50.

[0020] An outlet of the internal combustion engine 10 is connected to an exhaust manifold 12A, to which an inlet of an exhaust pipe 12B is connected. An outlet of the exhaust pipe 12B is connected to an inlet of the turbine 14A, and an outlet of the turbine 14A is connected to an inlet of an exhaust pipe 12C.

[0021] The turbine 14A is driven to rotate by exhaust gas flowing from the exhaust pipe 12B to the exhaust pipe 12C, thereby driving the compressor 14B to rotate. The turbine 14A has a variable nozzle 14D that can adjust the closing degree (opening degree) of an exhaust gas introduction passage through which exhaust gas drawn from the exhaust pipe 12B is guided to a turbine wheel 14E. The closing degree (opening degree) of the variable nozzle 14D is adjusted by a nozzle driving member 14C (e.g., an electric motor). The nozzle driving member 14C is controlled by a control signal from the engine control device 50. The variable nozzle 14D and the nozzle driving member 14C correspond to the boost pressure control configured to control the boost pressure by the supercharger (turbocharger 14) of the present disclosure.

[0022] An outlet of the exhaust pipe 12C is connected to an inlet of an oxidation catalyst 42, and an outlet of the oxidation catalyst 42 is connected to an inlet of the diesel particulate filter (DPF) 43. Although not shown in the figure, an outlet of the DPF 43 is connected to a urea selective catalytic reduction (urea-SCR) system that purifies nitrogen oxides (NOx) and the like. The oxidation catalyst 42 purifies and oxidizes carbon monoxide (CO) and hydrocarbons (HC) in the exhaust gas, and the DPF 43 collects particulate matter in the exhaust gas. Note that the urea-SCR system may be optional.

[0023] The engine control device 50 corresponds to the controller that detects the operating condition of the engine 10 based on measurement signals from various detection elements including the above-described detection elements, and controls various actuators including the injectors 41A, 41B, 41C, 41D, and the nozzle drive element 14C. The engine control device 50 is configured to send and receive various pieces of information to and from the engine control device 60 via a communication line 50T. For example, the engine control device 50 receives request torque information including a request torque for the hydraulic load of the boom and arm, and determines the torque requested by the engine body based on the request torque in the request torque information.

[0024] The following describes the Fig. 4, connected to the hydraulic pump 21. The hydraulic pump 21 is driven to rotate by the rotational force of the engine 10 and supplies hydraulic oil to a valve unit 22 through a hydraulic oil pipe 21A. The valve unit 22 has a plurality of switching valves, which are switched by operating the operating components, and supplies hydraulic oil to and discharges hydraulic oil from the various hydraulic pressure actuators. The operating components include a boom lever 23A, an arm lever 23B, and a bucket lever 23C. The hydraulic actuators include a boom cylinder 25A, an arm cylinder 25B, a bucket cylinder 25C, a travel hydraulic motor 26A, and a rotary hydraulic motor 26B. For example, when the operator operates the boom lever 23A, the hydraulic oil passage in the valve unit 22 is changed and the boom cylinder 25A is actuated.

[0025] The operating states of the operating components are input from the operating component, e.g., the boom lever 23A, to the engine control device 60. For example, the engine control device 60 detects the operating states of the operating components based on the input signal, calculates the target hydraulic pressure corresponding to the operating states of the operating components, and controls the hydraulic pump 21 based on the calculated target hydraulic pressure so as to adjust the pressure of the hydraulic oil from the hydraulic pump 21. Subsequently, the engine control device 60 calculates the demand torque based on the control state of the hydraulic pump 21 and sends the demand torque information including the demand torque to the engine control device 50 via the communication line 50T.In addition, a signal from an engine control selector 24 is input to the machine control device 60. The engine control selector 24 is provided to set the speed of the internal combustion engine 10, which corresponds to the accelerator pedal of passenger vehicles. The operator sets the control selector 24 to the speed that generates the torque necessary for operating the construction machine. The set speed, which corresponds to the speed set to the engine control selector 24, is included, for example, in the aforementioned request torque information.

[0026] [Examples of the control process ( Fig. 5) and the operating waveform ( Fig. 6) of the internal combustion engine control device 50 (controller) according to the first embodiment]

[0027] The following describes with reference to the Fig. 5 shows an example of the control process of the internal combustion engine control device 50 (which corresponds to the controller) according to the first embodiment. The internal combustion engine control device 50 activates the Fig. 5 at predetermined time intervals (e.g., several milliseconds to several tens of milliseconds) and the process proceeds to step S010. Fig. 6 shows an example of the operating waveform when the signal represented by the flow chart in Fig. The control process shown in Figure 5 is executed.

[0028] In step S010, the engine control device 50 determines the requested torque, the rotational speed, and the boost pressure, and the process proceeds to step S015. For example, the engine control device 50 receives the requested torque information from the engine control device 60, stores the requested torque included in the received requested torque information, determines the engine rotational speed based on the measurement signal from the rotation detection device 33, and stores the determined rotational speed, and determines a boost pressure based on the measurement signals from the compressor downstream pressure detector 32 and the atmospheric pressure detector 37, and stores the determined boost pressure. Note that the requested torque does not need to be determined by receiving the requested torque information, but may be measured or calculated by the engine control device 50.

[0029] The operating waveform in Fig. The request torque shown in Fig. 6 shows an example of the request torque included in the request torque information received by the engine control device 50. In Fig. 6 are the Fig. 1 shown companies (the excavation company) and the one in Fig. 2 (the rotation operation), which corresponds to the high-load operation, is carried out for the period between time t1 and time t2 (and the period between time t3 and time t4, the period between time t5 and time t6 and the period between time t7 and time t8) and the Fig. 3 (the operation in which sand and gravel are transported in the bucket), which corresponds to the low-load operation, is carried out for the period between time t2 and time t3 (and the period between time t4 and time t5, the period between time t6 and time t7, and the time after time t8). In other words, Fig. 6 an example of successive operation in which the high-load operation (the period between time t1 and time t2, the period between time t3 and time t4, the period between time t5 and time t6 and the period between time t7 and time t8) and the low-load operation (the period between time t2 and time t3, the period between time t4 and time t5, the period between time t6 and time t7 and the time after time t8) are alternately repeated. In the Fig. In the example shown in Figure 6, the rotational speed Ns of the internal combustion engine is set to 2000 rpm on the engine control selector 24.

[0030] In step S015, the engine control device 50 calculates the fuel injection amount (the actual fuel injection amount) according to the request torque and the rotational speed, and the process proceeds to step S020. For example, based on the request torque and the rotational speed, the engine control device 50 calculates and stores the fuel injection amount (the actual fuel injection amount) necessary to generate the request torque. It is noted that the calculated fuel injection amount is determined by a Fig. 5 shown process is to be injected into the cylinders of the internal combustion engine 10 using a different control process (not shown). Fig. 6 represents an example of the fuel injection quantity calculated by the engine control device 50, which is used to generate the request torque from Fig. 6 is necessary. The request torque becomes large for the period between time t1 and time t2, the period between time t3 and time t4, the period between time t5 and time t6, and the period between time t7 and time t8 during which the high-load operation is performed, so the fuel injection amount becomes large. The fuel injection amount corresponds to the request torque-related amount for controlling the internal combustion engine, which is calculated based on the request torque. Thus, the fuel injection amount corresponding to the request torque can be calculated. Note that the internal combustion engine control device 50 calculates the fuel injection amount (the request torque-related amount) such that the fuel injection amount (the request torque-related amount) increases as the request torque increases.

[0031] In step S020, the engine control device 50 determines whether the calculated fuel injection amount (the actual fuel injection amount) is equal to or greater than a torque determination threshold Fs. If it is determined that the calculated fuel injection amount (the actual fuel injection amount) is equal to or greater than the torque determination threshold Fs (Yes in step S020), the process proceeds to step S025A. If it is determined that the calculated fuel injection amount (the actual fuel injection amount) is less than the torque determination threshold Fs (No in step S020), the process proceeds to step S025B.

[0032] If the process proceeds to step S025A, the engine control device 50 adds ΔD1 to the stored target boost pressure maintenance indicator (the previous value of the target boost pressure maintenance indicator), renews the target boost pressure maintenance indicator (the current value of the target boost pressure maintenance indicator), and the process proceeds to step S030.

[0033] If the process proceeds to step S025B, the engine control device 50 subtracts ΔD2 from the stored target boost pressure maintenance indicator (the previous value of the target boost pressure maintenance indicator), renews the target boost pressure maintenance indicator (the current value of the target boost pressure maintenance indicator), and the process proceeds to step S030.

[0034] As in Fig. 6, the indicator for maintaining the target boost pressure is a value which is displayed at predetermined intervals (ie, every time the target boost pressure is Fig. 5 is executed) by a count-up process (step S025A) when the fuel injection amount is equal to or greater than the torque determination threshold Fs. The target boost pressure maintenance indicator is reset at predetermined intervals (i.e., every time the Fig. 5 is executed) is decreased by a count-down process (step S025B) when the fuel injection amount is lower than the torque determination threshold Fs. The torque determination threshold Fs is determined through various experiments and simulations. In this example, the target boost pressure maintenance indicator is increased during the period between time t1 and time t2, the period between time t3 and time t4, and the period between time t5 and time t6, and is decreased in the other period. Note that the value of the increased amount ΔD1 may be the same value as or different from that of the decreased amount ΔD2.The increase in the indicator for maintaining the target boost pressure when increasing can be adjusted by adjusting the value of ΔD1 and a decrease in the indicator for maintaining the target boost pressure when decreasing can be adjusted by adjusting the value of ΔD2.

[0035] If the process proceeds to step S030, the engine control device 50 determines whether the stored target boost pressure maintenance indicator (the current target boost pressure maintenance indicator) is equal to or greater than the gradual decrease threshold Ss. If it is determined that the stored target boost pressure maintenance indicator (the current target boost pressure maintenance indicator) is equal to or greater than the gradual decrease threshold Ss (Yes in step S030), the process proceeds to step S035. If it is determined that the stored target boost pressure maintenance indicator (the current target boost pressure maintenance indicator) is less than the gradual decrease threshold Ss (No in step S030), the process proceeds to step S040B.The value of the gradual reduction threshold Ss is determined by the various experiments and simulations.

[0036] If the process proceeds to step S035, the engine control device 50 determines whether the stored fuel injection amount for calculating the target boost pressure (the previous fuel injection amount for calculating the target boost pressure) is greater than the fuel injection amount (the current fuel injection amount). If it is determined that the previous target fuel injection amount for calculating the target boost pressure is greater than the current fuel injection amount (Yes in step S035), the process proceeds to step S040A. If it is determined that the previous target fuel injection amount for calculating the target boost pressure is equal to or less than the current fuel injection amount (No in step S035), the process proceeds to step S040B.For example, when the fuel injection amount is changed to increase, exceeding the fuel injection amount for calculating the target boost pressure while the fuel injection amount for calculating the target boost pressure is gradually decreased, the engine control device 50 immediately sets the fuel injection amount for calculating the target boost pressure as the fuel injection amount.

[0037] If the process proceeds to step S040A, the engine control device 50 updates the current fuel injection amount for calculating the target boost pressure using an equation 1 provided below and proceeds to step S045. With such an equation 1, the fuel injection amount for calculating the target boost pressure can be Fig. 6, the target boost pressure can be gradually reduced from the high fuel injection amount τH to the lower fuel injection amount τL during the period between time t2 and time t3, the period between time t4 and time t5, and the period between time t6 and time t7. The value for N in Equation 1 is determined through various experiments and simulations. Gradually reducing the fuel injection amount for calculating the target boost pressure gradually reduces the target boost pressure, which is calculated based on the fuel injection amount for calculating the target boost pressure.

[0038] The process of step S040A corresponds to the gradual decrease process, which is executed such that the target boost pressure is gradually changed to decrease from the current target boost pressure to the decreased target boost pressure corresponding to the decreased request torque amount (the request torque or the request torque-related amount) when the amount corresponding to the request torque amount is changed to be decreased. By executing the gradual decrease process, the engine control device 50 gradually decreases the target boost pressure. Although it has been described that, as an example of the gradual decrease process in the present embodiment, the request torque-related amount (ie, the target boost pressure) is continuously gradually decreased with time, the request torque-related amount (ie,, the target boost pressure) can be gradually reduced over time. The gradual reduction of the target boost pressure can be achieved in various patterns and is not limited to the patterns described above, which are the pattern in which the target boost pressure is gradually (successively) reduced and the pattern in which the target boost pressure is reduced in steps. The current fuel injection quantity for calculating the target boost pressure = the previous fuel injection quantity for calculating the target boost pressure = (the current fuel injection quantity − the previous fuel injection quantity for calculating the target boost pressure) / N

[0039] If the process proceeds to step S040B, the engine control device 50 uses Equation 2 provided below, in which the current fuel injection amount calculated in step S015 replaces the current fuel injection amount for calculating the target boost pressure, and the process proceeds to step S045. In Equation 2, the current fuel injection amount replaces the current fuel injection amount for calculating the target boost pressure for the time before time t1, the time period between time t1 and time t2, the time period between time t2 and time t3, the time period between time t3 and time t4, the time period between time t5 and time t6, and the time after time t7 in the fuel injection amount for calculating the Fig. 6 shown target boost pressure.

[0040] The process from step S030 to step S040B corresponds to the process that sets the fuel injection amount for calculating the target boost pressure as the fuel injection amount (ie, the process of setting the reduced target boost pressure as the target boost pressure) without using the gradual decrease process (step S040A) when the target boost pressure maintenance indicator is smaller than the gradual decrease threshold Ss and the value related to the request torque (the request torque or the request torque related amount) is changed to be decreased (including the case where the request torque related amount is changed to increase). The current fuel injection quantity for calculating the target boost pressure = the current fuel injection quantity

[0041] If the process proceeds to step S045, the engine control device 50 calculates the target boost pressure based on the current fuel injection amount for calculating the target boost pressure and the engine speed, and the process proceeds to step S050. The target boost pressure can be calculated based on the value corresponding to the request torque (the request torque or the request torque-related amount) and the engine speed. The target boost pressure is calculated such that the target boost pressure increases as the amount related to the request torque increases. In other words, the target boost pressure is set such that the target boost pressure increases as the amount related to the request torque increases.

[0042] In step S050, the engine control device 50 controls the boost pressure control (in this case, the nozzle drive component 14C in Fig. 4) based on the current boost pressure (the boost pressure determined in step S010) and the target boost pressure such that the current boost pressure approaches the target boost pressure.

[0043] As described, when the fuel injection amount is changed to be reduced and the target boost pressure maintenance indicator is equal to or greater than the gradual reduction threshold Ss, the engine control device 50 gradually reduces the fuel injection amount for calculating the target boost pressure from the current fuel injection amount for calculating the target boost pressure to the reduced fuel injection amount by executing the gradual reduction process (step S040A). By gradually reducing the fuel injection amount for calculating the target boost pressure, the target boost pressure is gradually reduced.When the fuel injection amount is changed to decrease and the target boost pressure maintenance indicator is less than the gradual decrease threshold Ss, the engine control device 50 sets the fuel injection amount for calculating the target boost pressure as the decreased fuel injection amount (step S040B). When the fuel injection amount is changed to increase, the engine control device 50 sets the fuel injection amount for calculating the target boost pressure as the decreased fuel injection amount (step S040B).

[0044] According to the Fig. In the conventional control device shown in Figure 8, the target boost pressure is calculated based on the fuel injection amount and the engine speed. When the fuel injection amount drops from the high fuel injection amount τH to the low fuel injection amount τL, for example, at time t4, the target boost pressure immediately drops from the high target boost pressure TpH to the low target boost pressure TpL (refer to reference symbol P32 in Fig. 8). If the fuel injection quantity at time t5 in Fig. 8 increases from the low fuel injection amount τL to the high fuel injection amount τH, the target boost pressure consequently increases from the low target boost pressure TpL to the high target boost pressure TpH. However, there is a large difference between the low target boost pressure TpL and the high target boost pressure TpH. As a result, a large drop in the speed N32 (torque drop) may occur due to the long rise time Td32 of the actual boost pressure and a delay in increasing the engine torque caused by delayed charging.

[0045] According to the Fig. 6, the fuel injection amount for calculating the target boost pressure is calculated based on the fuel injection amount and the indicator for maintaining the target boost pressure by the engine control device 50, and corresponds to the fuel injection amount for calculating the target boost pressure. When the fuel injection amount drops from the high fuel injection amount τH to the low fuel injection amount τL at time t4, in the first embodiment, the fuel injection amount for calculating the target boost pressure does not immediately drop from the high fuel injection amount τH to the low fuel injection amount τL, but gradually decreases from the high fuel injection amount τH to the low fuel injection amount τL, as shown in Fig. 6. When the fuel injection quantity increases from the low fuel injection quantity τL to the high fuel injection quantity τH, the target boost pressure increases accordingly at time t5 from the intermediate target boost pressure TpG, which is then decreasing, but not from the low target boost pressure TpL to the high target boost pressure TpH. At time t5, at which the fuel injection quantity increases from the low fuel injection quantity τL to the high fuel injection quantity τH, the target boost pressure thus increases according to the first embodiment ( Fig. 6) to reduce the small difference from the intermediate target boost pressure TpG to the high target boost pressure TpH, while the target boost pressure is maintained according to the conventional control system ( Fig. 8) by the large difference from the low target boost pressure TpL to the high target boost pressure TpH. Accordingly, the rise time Td12 of the actual boost pressure in Fig. 6 shorter than the rise time Td32 of the actual boost pressure of the conventional control system ( Fig. 8), which suppresses a delay in the increase of the torque of the combustion due to the delayed charging, thereby causing a large drop in the speed, as in Fig. 6 shown by N12, is suppressed (a Fig. 8 Decrease shown by N32 is lower than N12 in Fig. 6 and a torque drop is suppressed). [Second embodiment (FIG. 7)]

[0046] The following describes a second embodiment of the present disclosure with reference to Fig. 7. According to the control process of the second embodiment for the internal combustion engine control device 50, which is not shown in the figure, the indicator for maintaining the target boost pressure and the steps S020, S025A, S025B, S030 are from the Fig. 5 is omitted. When the request torque (or the request torque-related amount (fuel injection amount) is changed to be decreased, the fuel injection amount for calculating the target boost pressure and the target boost pressure are changed as shown in Fig. 7, gradually reduced.

[0047] Although the request torque or the request torque-related amount (fuel injection amount) is changed to be decreased during the period between time t2 and time t3, in the Fig. 6, the fuel injection quantity for calculating the target boost pressure and the target boost pressure is not gradually reduced because the indicator for maintaining the target boost pressure is smaller than the gradual reduction threshold Ss, so that a drop in the speed may occur, as shown by reference symbol N11. Since the indicator for maintaining the target boost pressure in the Fig. 7 is omitted, on the other hand, the fuel injection amount for calculating the target boost pressure and the target boost pressure are gradually reduced during the period between time t2 and time t3, as well as the period between time t4 and time t5, and the period between time t6 and time t7. Accordingly, a drop in the rotational speed does not occur at time t3, as shown by reference symbol N21. The fuel injection amount for calculating the target boost pressure and the target boost pressure are gradually reduced in both Fig. 6 (first embodiment) as well as in Fig. 7 (second embodiment) during the period between time t4 and time t5 and the period between time t6 and time t7 is gradually reduced, a drop in the speed is suppressed (N12, N13 in Fig. 6 and N22, N23 in Fig. 7).

[0048] According to the Fig. 7, the engine control device 50 sets an increased fuel injection amount, which corresponds to the fuel injection amount after it is increased, as the fuel injection amount for calculating the target boost pressure (step S040B in Fig. 5) when the fuel injection amount is changed to increase (times t1, t3, t5, and t7). In addition, the engine control device 50 executes the gradual reduction process (step S040A in Fig. 5) when the fuel injection amount is changed to be decreased (times t2, t4, t6, and t8), and gradually decreases the current fuel injection amount for calculating the target boost pressure toward the reduced fuel injection amount corresponding to the fuel injection amount after it is decreased. This can suppress a drop in the rotational speed even in a case where the demand torque is changed to increase after it is changed to be decreased. [Effects]

[0049] According to the above-described engine control system of the construction machine, even in the case where an experienced operator performs the successive operation in which the high-load operation and the low-load operation are alternately repeated in a short time, a drop in the rotational speed of the engine (drop in torque) is suppressed by gradually reducing the target boost pressure when the operation changes from the low-load operation to the high-load operation, and the operation efficiency can be increased.

[0050] According to the present disclosure, the gradual reduction process is performed such that a change in the target boost pressure becomes gradual when the target boost pressure is reduced from the current target boost pressure to the reduced target boost pressure corresponding to the reduced request torque amount (the request torque amount or the request torque amount) when the request torque amount is changed to be reduced. In other words, for the next time the request torque amount or the request torque amount is changed to increase, the boost pressure is gradually reduced to the reduced target boost pressure when the request torque amount or the request torque amount is changed to be reduced, instead of immediately reducing the target boost pressure to the reduced target boost pressure.Accordingly, even when the successive operation is carried out in which the low load operation and the high load operation are alternately repeated, a drop in the rotational speed of the internal combustion engine can be suppressed when the low load operation is switched to the high load operation, with the result that the working efficiency can be increased.

[0051] According to the present disclosure, the boost pressure can be appropriately reduced by successively gradually or stepwise gradually reducing the target boost pressure during the gradual reduction process.

[0052] According to the first embodiment, the target boost pressure maintenance indicator related to the operation pattern of the construction machine is used to determine whether the gradual reduction process is executed when the demand torque or the demand torque-related amount is changed to be reduced. In a case where the gradual reduction process is not executed, it is determined that the operation pattern is a pattern in which the construction machine does not need to be prepared for the demand torque or the demand torque-related amount to change to increase. In this case, the target boost pressure is reduced according to the reduction in the demand torque or the demand torque-related amount, so that the mechanical loads on various components of the loader can be reduced.

[0053] According to the first embodiment, an appropriate indicator for maintaining the boost pressure can be relatively easily determined according to the operation patterns of the construction machinery.

[0054] According to the second embodiment, the demand torque-related amount can be determined appropriately and easily. The target boost pressure is set based on the fuel injection amount to calculate the target boost pressure, which is gradually reduced as the fuel injection amount (the demand torque-related amount) is changed to be reduced, with the result that a gradual reduction in the target boost pressure can be easily achieved.

[0055] According to the present disclosure, the target boost pressure maintenance indicator related to the operation pattern of the construction machine is used to determine whether the gradual reduction process is executed when the fuel injection amount is changed to be reduced. Thus, a gradual reduction of the target boost pressure can be easily achieved. In a case where the gradual reduction process is not executed, it is determined that the operation pattern is a pattern in which the construction machine does not need to be prepared for a change to increase in the demand torque or the demand torque-related amount. In this case, the target boost pressure is reduced according to the reduction in the demand torque or the demand torque-related amount, so that the mechanical loads on various components of the loader can be reduced.

[0056] The internal combustion engine control system of the construction machine of the present disclosure is not limited to the above-described configuration, control process structure, and operation waveforms, but can be modified, expanded, or reduced within the scope of the present disclosure. For example, the calculation for the gradual reduction is not limited to the above-described calculation method. Any suitable calculation method is applicable as long as the value is gradually reduced. The construction machine is not limited to the excavator but can refer to various construction machines (an industrial vehicle or a commercial vehicle).

[0057] The waveforms of the present embodiments are not limited to Fig. 6 examples shown. The control process is not limited to the Fig.5. Boost pressure control is not limited to the variable nozzle and the nozzle drive component, but may be provided by a bypass pipe that bypasses a turbine and a control valve that controls the opening degree of the bypass pipe. The supercharger is not limited to the mechanical turbocharger described in the present embodiments.

[0058] Although the target boost pressure and the target boost pressure maintenance indicator are calculated using the fuel injection amount (the request torque related amount) in the above-described embodiments, the target boost pressure and the target boost pressure maintenance indicator may be calculated using the request torque related amount (the request torque or the request torque related amount).

[0059] Some implementations are described in connection with thresholds and other types of values. Satisfaction may refer to being greater than, more than, higher than, equal to, or greater than, less than, lower than, or equal to or less than. Values ​​used in the description of the present embodiment are examples and are not intended to limit the scope of the present disclosure.

Claims

[1] Internal combustion engine control system of a construction machine (1) on which an internal combustion engine (10) with a loader (14) is mounted, comprising: a boost pressure control (14C, 14D) configured to control a boost pressure; and a controller (50) configured to determine a demand torque of the construction machine (1), to set a target boost pressure to control the internal combustion engine (10) based on the determined demand torque or a demand torque-related amount calculated based on the determined demand torque, and to control the boost pressure control (14C, 14D) such that an actual boost pressure approaches the target boost pressure, characterized by , that the controller (50) calculates the request torque-related amount based on the request torque such that the request torque-related amount increases as the determined request torque increases, the controller (50) sets the target boost pressure based on the request torque or the calculated request torque-related amount such that the target boost pressure increases while the request torque or the calculated request torque-related amount increases, the controller (50) executes a gradual reduction process such that the target boost pressure is gradually reduced when the target boost pressure is reduced from a current target boost pressure to a reduced target boost pressure corresponding to a reduced request torque or a reduced request torque-related amount when the request torque or the request torque-related amount is changed to decrease, the controller (50) calculates an indicator for maintaining the target boost pressure based on the request torque or the request torque-related amount, which indicator relates to an operating pattern of the construction machine (1), the controller (50) executes the gradual reduction process by which the target boost pressure is gradually reduced when the target boost pressure maintenance indicator is equal to or greater than a gradual reduction threshold and the request torque or the request torque-related amount is changed to be reduced, and the controller (50) does not execute the gradual reduction process and sets the reduced target boost pressure as the target boost pressure when the target boost pressure maintenance indicator is smaller than the gradual reduction threshold and the request torque or the request torque-related amount is changed to be reduced. [2] Internal combustion engine control system according to claim 1, characterized bythat the controller (50) reduces the target boost pressure continuously or gradually over time from the current target boost pressure to the reduced target boost pressure when the gradual reduction process is performed. [3] Internal combustion engine control system according to claim 1 or 2, characterized by , that the controller (50) executes a count-up process at predetermined intervals by which the indicator for maintaining the target boost pressure is increased when the request torque or the request torque-related amount is equal to or greater than a torque determination threshold, and the controller (50) executes a count-down process at the predetermined intervals by which the indicator for maintaining the target boost pressure is decreased when the request torque or the request torque-related amount is less than the torque determination threshold. [4] Internal combustion engine control system according to claim 1 or 3, characterized by , that the request torque-related amount is a fuel injection amount, the controller (50) calculates the fuel injection amount according to the request torque such that the fuel injection amount increases while the determined request torque increases, the controller (50) sets an increased fuel injection amount corresponding to the fuel injection amount after it has been increased as the fuel injection amount for calculating a target boost pressure when the fuel injection amount is changed to increase, the controller (50) sets a reduced fuel injection amount corresponding to the fuel injection amount after it has been reduced as the fuel injection amount for calculating the target boost pressure when the fuel injection amount is changed to be reduced and the indicator for maintaining the target boost pressure is smaller than the gradual reduction threshold, the controller (50) executes the gradual reduction process by which the fuel injection amount for calculating the boost pressure is gradually reduced from the current fuel injection amount for calculating the boost pressure to the reduced fuel injection amount when the fuel injection amount is changed to be reduced and the indicator for maintaining the target boost pressure is equal to or greater than the gradual reduction threshold, and the controller (50) sets the target boost pressure based on the fuel injection amount to calculate the target boost pressure. [5] Internal combustion engine control system of a construction machine (1) on which an internal combustion engine (10) with a loader (14) is mounted, comprising: a boost pressure control (14C, 14D) configured to control a boost pressure; and a controller (50) configured to determine a demand torque of the construction machine (1), to set a target boost pressure to control the internal combustion engine (10) based on the determined demand torque or a demand torque-related amount calculated based on the determined demand torque, and to control the boost pressure control (14C, 14D) such that an actual boost pressure approaches the target boost pressure, characterized by , that the controller (50) calculates the request torque-related amount based on the request torque such that the request torque-related amount increases as the determined request torque increases, the controller (50) sets the target boost pressure based on the request torque or the calculated request torque-related amount such that the target boost pressure increases while the request torque or the calculated request torque-related amount increases, the controller (50) executes a gradual reduction process such that the target boost pressure is gradually reduced when the target boost pressure is reduced from a current target boost pressure to a reduced target boost pressure corresponding to a reduced request torque or a reduced request torque-related amount when the request torque or the request torque-related amount is changed to decrease, the demand torque-related amount is a fuel injection amount, the controller (50) calculates the fuel injection quantity according to the request torque such that the fuel injection quantity increases as the determined request torque increases, the controller (50) sets an increased fuel injection amount corresponding to the fuel injection amount after it has been increased as the fuel injection amount for calculating a target boost pressure when the fuel injection amount is changed to increase, the controller (50) executes the gradual reduction process by which the fuel injection amount for calculating the target boost pressure is gradually reduced from a current fuel injection amount for calculating the target boost pressure to a reduced fuel injection amount corresponding to the fuel injection amount after it has been reduced when the fuel injection amount is changed to be reduced, and the controller (50) sets the target boost pressure based on the fuel injection amount to calculate the target boost pressure. [6] Internal combustion engine control system according to claim 5, characterized bythat the controller (50) reduces the target boost pressure continuously or gradually over time from the current target boost pressure to the reduced target boost pressure when the gradual reduction process is performed.

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