WO2016027480A1

WO2016027480A1 - Control device for construction vehicle engine

Info

Publication number: WO2016027480A1
Application number: PCT/JP2015/054186
Authority: WO
Inventors: 佐藤　真也; 星野　雅俊; 石川　広二
Original assignee: 日立建機株式会社
Priority date: 2014-08-19
Filing date: 2015-02-16
Publication date: 2016-02-25
Also published as: JP2016041924A; JP6305869B2

Abstract

A control device for a construction vehicle engine is equipped with: an engine (21) that drives a hydraulic pump (24); a load ratio moving average value calculation unit (504) that calculates a moving average value for the engine load ratio, obtained by executing a process for smoothing a time series of the load ratio of the engine (21); and an engine control unit (103) that adjusts the output of the engine (21). In an operating region of the engine (21) as defined by the rotational frequency and the load of the engine (21), a first operating region (R1), comprising a region from no load to full load, and a second operating region (R2), which is narrower than the first operating region (R1), are set. The engine control unit (103) adjusts the output of the engine (21) such that the moving average value of the engine load ratio remains within the second operating region (R2).

Description

Engine control device for construction machinery

The present invention relates to an engine control device for a construction machine in which a hydraulic pump is driven by an engine.

A hydraulic excavator that is a construction machine generally generates pressure oil by a hydraulic pump that uses an engine that is an internal combustion engine (mainly a diesel engine) as a drive source, and a hydraulic actuator such as a travel motor, a swing motor, and a hydraulic cylinder by the pressure oil. Is driven to perform a desired operation (traveling operation, turning operation, excavating operation, etc.) in the hydraulic excavator.

The engine is a driving force for driving a hydraulic pump in a hydraulic excavator, but the hydraulic excavator engine is used in a high-load operation compared to a vehicle engine such as a truck because of the nature of the work, and the frequency of the high-load operation is high.

For example, Japanese Unexamined Patent Application Publication No. 2010-121373 discloses a technique for reducing the engine load of a hydraulic excavator. In this document, an assist motor is added as a power source of the pump in addition to the engine (so-called hybrid power configuration), the required hydraulic pump power load is separated into a direct current component and an alternating current component, and the direct current component is exchanged with the engine. By causing the component to be borne by the motor, rapid load fluctuations on the engine are suppressed, and the burden on the engine is alleviated.

JP 2010-121373 A

】 The use form of the engine is completely different between the hydraulic excavator and the vehicle such as a truck, and as a result, the design concept of the engine is inevitably different. Therefore, even if the technique of the above-mentioned document is applied, it is difficult to divert it as an engine of a hydraulic excavator without adding a special specification change to the vehicle engine. Therefore, usually, (1) engine designed exclusively for hydraulic excavators is premised on high load operation, or (2) engine parts are strengthened by changing specifications to withstand high load operation on vehicle engines. There is a need to.

Therefore, regarding the manufacture of an excavator engine, if it is possible to divert the excavator as an engine of a hydraulic excavator without using the method (2) above and without making any special specification change, It can be one means of greatly reducing the manufacturing cost of construction machines such as the first.

In connection with this point, although the transient engine load can be reduced in the method of the above-mentioned document, the steady reduction of the engine load is not taken into consideration. In other words, the technique of this document allows continuation of high-load operation (steady engine load) in a hydraulic excavator as in the past, and does not take into consideration reducing the frequency and duration. Therefore, the engine load cannot be reduced to the extent that the vehicle engine can be used as the hydraulic excavator engine, and it is still necessary to prepare the hydraulic excavator engine by the above method (1) or (2). In other words, the problem of enormous man-hours and costs for engine development still cannot be solved.

An object of the present invention is to use a low-priced engine (for example, a vehicular engine) that is regularly used at a lower load than a construction machine engine and has established a mass production system in a construction machine without any special specification change. There is in making it possible.

In order to achieve the above object, an engine control device for a construction machine according to the present invention calculates an engine load index value indicating an engine driving a hydraulic pump and a time-dependent tendency of parameters related to the engine load. A load index calculation unit; and an output adjustment unit that adjusts the output of the engine. The engine operating range defined by the engine speed and load includes a range from no load to full load. 1 operation region and a second operation region that is included in the first operation region and narrower than the first operation region are set, and the output adjustment unit has the engine load index value within the second operation region. The output of the engine is adjusted so as to fall within the range.

According to the present invention, since the frequency and time during which the engine is operated at a high load can be reduced, the engine that is normally used at a lower load than the engine of the construction machine can be used in the construction machine without any special specification change. This can reduce the manufacturing cost of construction machinery.

The figure which shows the external appearance of a hydraulic shovel (1st Embodiment). The figure which shows the system configuration | structure of a hydraulic excavator (1st Embodiment). 1 is a diagram showing a system configuration around an engine (first embodiment). FIG. The figure which shows the fundamental view regarding engine load control (1st Embodiment). The figure which shows the view regarding the engine load factor reference value setting in engine load control (1st Embodiment). The figure which shows the time chart at the time of engine load control non-implementation. The figure which shows the time chart at the time of engine load control implementation (1st Embodiment). The figure which shows the control logic structure around an engine (1st Embodiment). The figure which shows the control flowchart regarding engine load control (1st Embodiment). The figure which shows the system configuration | structure of a hydraulic excavator (1st Embodiment). 1 is a diagram showing a system configuration around an engine (first embodiment). FIG. The figure which shows the time chart at the time of engine load control non-implementation. The figure which shows the time chart at the time of engine load control implementation (1st Embodiment). The figure which shows the control logic structure around an engine (1st Embodiment). The figure which shows the control flowchart regarding engine load control (1st Embodiment). The figure which shows the difference in the load factor distribution of the engine for vehicles, and the engine for hydraulic excavators.

Before describing the embodiment of the present invention, first, main features included in the engine control device and the construction machine according to the embodiment of the present invention will be described.

(1) A construction machine engine control device according to the present embodiment, which will be described later, includes an engine that drives a hydraulic pump and a load that calculates an engine load index value that indicates a tendency of a parameter related to the load of the engine to change over time. An index calculation unit (for example, an engine load factor moving average value calculation unit 504 described later) and an output adjustment unit (for example, an engine control unit 103 described later) for adjusting the output of the engine; The engine operating region defined by the load includes a first operating region consisting of a region from no load to full load, and a second operating region included in the first operating region and narrower than the first operating region. Is set, and the output adjustment unit adjusts the output of the engine so that the engine load index value falls within the second operation region. It is characterized in.

One method of procuring engines to be installed in construction machinery is for engines that are premised on installation on machinery other than construction machinery (for example, vehicles including trucks), and the mass production system has been established and the price is low. There is a method of mounting a new engine on a construction machine after changing specifications (engine strengthening) that can withstand frequent heavy load operation on the construction machine. As an engine used in this method, for example, there is an engine for a vehicle such as a truck. The engine load factor (the maximum engine torque at a certain rotational speed (N in FIG. 16) (total The distribution of the actual torque (the ratio of T in the figure) to the load) is concentrated in a lower area relatively far from the maximum torque (full load) as shown in FIG. On the other hand, the distribution of the engine load factor in the hydraulic excavator (construction machine) is frequently concentrated near the maximum torque as shown in FIG. 16, and the high load frequency is higher than that in the case of using in a vehicle. The stress acting on the engine is great. Therefore, when a hydraulic excavator is developed based on a vehicle engine as in the above method, various measures for adding high load resistance to the vehicle engine are necessary. There was a problem that it would lead to longer time and higher costs.

In response to this type of problem, as described above, the first operation region and the second operation region are set as the operation region of the engine, and the time change tendency of the parameter related to the load of the engine is shown. When a construction for adjusting the engine output so that the engine load index value falls within the second operating region is adopted in the engine control device for construction machinery, the steady engine load is narrower than the first operating region. Since it is restricted on and inside the contour line of the operation region, it is possible to avoid a situation where the engine is frequently used in a state close to the full load. Therefore, even when an engine designed mainly for use in a load within a predetermined range less than the full load is mounted on a construction machine, by limiting the operating range of the engine within the second operating range, Since it is avoided that the engine is continuously used at a high load that deviates from the predetermined range, it is easy to divert the engine to the construction machine, and the manufacturing cost of the engine for the construction machine, and thus the manufacturing cost of the construction machine, can be reduced. It can be greatly reduced.

In the present invention, the main purpose of using the engine load index value indicating the temporal change tendency of the parameter related to the engine load for control is to eliminate instantaneous fluctuations (micro fluctuations) of the engine load. This is because the tendency of the engine load change is grasped by paying attention to the macro fluctuation of the engine load. As described above, when the “trend” of the time change of the parameter rather than the time change of the parameter is used as a criterion for output adjustment, it is acceptable to use the engine load momentarily exceeding the upper limit value of the second operation region. Therefore, it can suppress that work amount and operativity fall notably.

In the engine load index value in the above (1), a reference value (for example, an upper limit value of the second operation region determined in order to continuously use the engine in a predetermined range from no load to less than full load) The engine load factor reference value (the truck normal load factor upper limit value), which will be described later, is set, and the reference value is preferably less than the full load. As a result, even if an engine designed mainly for use in a load within a predetermined range less than the full load (for example, use in the second operation region) is mounted on a construction machine, the operation region of the engine is By limiting to the second operating region, it is possible to avoid the engine being continuously used at a high load that deviates from the predetermined range.

As a specific example of the engine load index value in the above (1), there is one that uses a value obtained by accumulating a time series of parameters related to the engine load as the engine load index value. The reference value in this case is a value that increases in proportion to an increase in time while referring to the accumulated value of the engine load index value when the engine is continuously used at the upper limit value in the predetermined range. For example, there is a method of setting the reference value so that the value is defined as a function of time that monotonously increases with time. In this case, the engine output is adjusted so that the engine load index value, which is a time-series cumulative value of the parameter, is held below the reference value.

As another specific example of the engine load index value in the above (1), a numerical value obtained by performing a smoothing process on a time series of parameters related to the engine load is used as the engine load index value. There is something. As the reference value in this case, there is a method in which a value less than the value of the parameter when the engine is at full load is set as the reference value. In this way, when the construction for adjusting the engine output so that the engine load index value obtained through the smoothing process is kept below the reference value is adopted in the engine control device for construction machinery, the smoothing process and the engine The output adjustment function allows the engine load to momentarily increase beyond the reference value, but the steady engine load is limited to below the reference value (that is, less than the full load value). It is possible to avoid a situation where the engine is frequently used in a state close to the load (this case will be described in detail in each embodiment described later).

It should be noted that as the time constant used during the smoothing process, for example, the thermal time constant of the engine body can be used in consideration of the responsiveness of the engine temperature accompanying the engine load fluctuation. Specific examples of the smoothing process include a moving average (for example, a simple moving average, a weighted moving average, and a cumulative moving average) and a filter process (for example, a low-pass filter process).

(2) The “reference value” in the above (1) is preferably set according to the specifications of the engine mounted on the construction machine, and when the load range (normal range) in which the engine is normally used is generally determined. Preferably, the reference value is set to the upper limit value of the load range. If the reference value is set in this way, the engine will not be used outside the normal load range. Therefore, the engine is designed and manufactured under the concept that it is not assumed to be used in construction machinery. Even if it is, it can be easily used for construction machinery. In addition, there are vehicles such as trucks, etc., where the normal range of the engine is generally determined. However, even if the normal range of the engine is determined, as long as the value is less than the upper limit value of the normal range, the value may be set as the reference value.

Further, the “reference value” in the above may be a constant value regardless of the engine speed, or may be changed for each engine speed. As a specific example of the latter case, the maximum engine torque for each rotation speed is set as a reference value setting reference, and the torque corresponding to what percentage (for example, 70%) of the maximum engine torque at each rotation speed is set as a reference value. There is something. When drawing a curve with the maximum torque “convex upward” as shown in the upper part of FIG. 16, the reference value draws an upward convex curve located below the curve drawn by the maximum torque.

(3) As the “parameter related to the engine load” in (1) above, for example, engine torque, engine speed, engine intake pressure, engine cylinder pressure, fuel injection amount, turbine speed in the turbocharger, or There are various parameters (engine state parameters) indicating the engine state, including the required torque of the hydraulic pump and the like. Two or more of these parameters may be used as the parameter, or other parameters may be used as long as the engine load can be determined directly or indirectly.

As another specific example of the “parameter related to the engine load” in the above (1), an engine load or an engine load factor can also be used. The engine load can be estimated from at least one of the above-described engine condition parameters, and can be estimated from, for example, at least one of the engine torque, the fuel injection amount, and the required torque of the hydraulic pump. The engine load factor in the above indicates the ratio of the engine torque to the engine maximum torque at the rotational speed.

Note that “parameters related to the engine load” can be acquired from output values of various sensors mounted on the construction machine, calculated values or stored values of a computer (including a microcomputer) mounted on the construction machine. Various means are possible, such as acquisition from. For example, among the engine state parameters, the engine speed, the engine intake pressure, the engine cylinder pressure, the turbine speed, etc. can be obtained from the output value from the sensor. For example, the fuel injection amount can be calculated by the engine control unit. is there.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view of a hydraulic excavator 1 (hydraulic construction machine, hydraulic working machine) according to an embodiment of the present invention. The hydraulic excavator 1 includes an articulated front working device (working device) 2 including a boom 6, an arm 7, and a bucket 8 that rotate in a vertical direction, and a vehicle body 3 including an upper swing body 4 and a lower traveling body 5. The base end (right end in the figure) of the boom 6 of the front working device 2 is supported by the front portion of the upper swing body 4 so as to be rotatable with respect to the vertical direction.

FIG. 2 is an overall system configuration diagram of the excavator 1 according to the first embodiment of the present invention. In FIG. 2, thick black arrows indicate the flow of pressure oil from the hydraulic pump 24 to the

actuators

31, 42, 9, 10, and 11, and thick white arrows indicate the

actuators

31, 42, 9, 10, and 11. 11 shows the flow of return oil from 11 to the pump 24 via the tank 26. Moreover, the thin black arrow in FIG. 2 has shown the supply direction of motive power or electric power.

As is clear from FIG. 2, the hydraulic excavator of the present embodiment is a so-called hybrid hydraulic excavator provided with a diesel engine 21 and a motor 22 as a drive source of the hydraulic pump 24. The diesel engine 21, the assist motor 22, and the hydraulic pump 24 are mechanically connected, and the hydraulic pump 24 is driven by a sum of shaft outputs of the engine 21 and the assist motor 22 (total output).

Further, the assist motor 22 is electrically connected to the battery 23, and when the motor 22 is powered, the hydraulic pump 24 is driven by receiving electric power from the battery 23. Note that, when a predetermined condition is satisfied, the assist motor 22 functions as a generator. At that time, the assist motor 22 is driven by the shaft output of the engine 21 to generate electric power, and the electric power at the time of power generation is stored in the battery (power storage device) 23.

In the hydraulic pump 24, the hydraulic oil sent from the hydraulic oil tank 26 is compressed into pressure oil and sent to the control valve 25. The control valve 25 is based on an operation command from an operator via an operation lever (not shown), supplied pressure oil to the traveling hydraulic motor 42 required for the traveling operation, and a swing hydraulic motor 31 necessary for the upper swing body operation. Pressure oil supplied to the

hydraulic cylinders

9, 10, 11 necessary for the operation of the work device 2, and unnecessary pressure oil is returned to the hydraulic oil tank 26.

The swing hydraulic motor 31 uses the pressure oil distributed from the control valve 25 as a power source, and drives the upper swing body 4 via the swing reduction device 32 and the swing gear 33. The traveling hydraulic motor 42 is driven by pressure oil sent from the control valve 25 via the center joint 41, and drives the crawler 44 via the traveling speed reduction device 43. For the working device 2 (the boom 6, the arm 7, and the bucket 8), the boom cylinder 9, the arm cylinder 10, and the bucket cylinder 11 are driven based on the pressure oil distributed from the control valve 25. As a result, the boom 6 is driven. Each of the arm 7 and the bucket 8 is controlled in accordance with a desired operation instructed by an operator via an operation lever.

FIG. 3 is a diagram showing a hydraulic excavator engine according to the first embodiment and a peripheral system configuration. A diesel engine 21 and an assist motor 22 are directly connected to the hydraulic pump 24 via an output shaft 305 as a power source for driving the hydraulic pump 24, and a battery 23 is electrically connected to the assist motor 22. ing. As a control unit for controlling these, a main control unit 101 that is a computer that controls the center of the hydraulic excavator 1, a display device that displays the state of the hydraulic excavator toward the operator, and processing related to display on the display device. A monitor unit 102 in which a computer to be executed is unitized, an engine control unit 103 that is a computer that controls the engine 21, a motor control unit 104 that is a computer that controls the assist motor 22, and the state of the battery 23 are monitored. There is a battery control unit 105 or the like that is a computer, and these control units (computers) 102, 103, 104, and 105 are mainly information about the main control unit 101. They are interconnected by Ttowaku.

The power control related input to the main control unit 101 includes a key switch 201 for starting and stopping the engine 21, an engine control dial 202 for an operator to specify the number of revolutions of the engine 21, and the state of the hydraulic excavator 1. Auto idle switch 203 for optimizing the idling speed according to the power, power mode switch 204 for the operator to adjust the output of engine 21 (engine 12 and motor 22), traveling operation, upper swing body operation, working device There is an operation lever signal 205 or the like output from the operation lever that instructs the operation.

Further, as information from the peripheral control unit, the engine control unit 103 determines whether the engine 21 is operating or abnormal, the motor control unit 104 determines whether the assist motor 22 is operating or abnormal, and the battery control unit 105 indicates the battery 23. Information such as the amount of stored electricity and the presence or absence of abnormality is input to the main control unit 101.

As functions of the power system in the main control unit 101, in addition to controlling the output of the hydraulic pump 24 on the basis of the input information, the power system upper management such as power distribution of the engine 21 and the assist motor 22 is performed. In response, the engine control unit 103 and the motor control unit 104 control the diesel engine 21 and the assist motor 22, respectively. Thereby, the main control unit 101 and the engine control unit 103 function as a control device (engine control device) for the diesel engine 21.

The engine 21 includes a fuel injection device 301 that injects fuel based on a target fuel injection amount command from the engine control unit 103, an exhaust manifold 302, a turbocharger 303 having a turbine, an exhaust pipe 304, and a DPF device 401. I have.

A rotation sensor 306 for detecting the engine speed is attached to the output shaft 305 of the engine 21, and the rotation sensor 306 outputs a detection value to the engine control unit 103. The supercharging pressure sensor 307 detects the supercharging pressure of the turbocharger (supercharger) 303 and outputs it to the engine control unit 103.

The DPF device 401 includes an oxidation catalyst 403 and a PM collection filter 403. An intake air temperature sensor 404 is installed between the oxidation catalyst 403 and the PM collection filter 403, and a DPF differential pressure sensor 405 that detects a differential pressure across the PM collection filter 403 is installed. Detection values of both

sensors

404 and 405 are output to the engine control unit 103.

Next, FIG. 4 shows a basic concept regarding engine load control performed by the hydraulic excavator 1 according to the present invention. In FIG. 4, the load of the engine 21 is indicated by the engine torque T at the engine speed N at that time.

In the present embodiment, as the engine 21, a truck engine is used among vehicle engines such as a passenger car and a freight car (for example, a truck) whose main work is traveling. Vehicle engines, including truck engines, are usually used at low loads compared to the use of engines in construction machinery, and the price is low because mass production systems have been established. The engine 21 is based on a truck engine corresponding to the rated output of the hydraulic pump 24, and switches the power control content according to the strength of the load pattern of the hydraulic pump 24.

The purpose of the engine load control performed in the present embodiment is to bring the engine load distribution (engine torque distribution in FIG. 4) during operation of the hydraulic excavator closer to the load distribution of the truck engine. It can be installed as an excavator engine without major specification changes.

Therefore, in FIG. 4, the first operation region R1 and the second operation region R2 are set as two-dimensional engine operation regions defined by the engine speed and the engine torque. The first operation region R1 is a normal operation region of the hydraulic excavator that is defined in a range from no load (torque zero) to full load (maximum engine torque at each number of turns), and the maximum engine torque (full load at each rotation speed). This corresponds to a point on the line T1 drawn by the set of) and a region located below the line T1. The second operation region R2 is set in consideration of an operation region (normal region) that is normally used in a truck engine, and the second operation region R2 is a predetermined value from no load to less than full load (less than T1). An operation region defined by a range up to (a value on T2), and a region located below the line T2 and a point on the line T2 drawn by a set of predetermined values set to less than T1 at each rotational speed Corresponds to this. As a result, the second operation region R2 is included in the first operation region R1, and the area thereof is narrower than that of the first operation region R1. That is, if the engine is operated in the second operation region R2, the engine load can be continuously reduced as compared with the case where the engine is operated in the first operation region R1.

The torque line T2 is a set of engine load reference values (details will be described later) at each rotation speed, and in the example of FIG. 4, coincides with the upper limit value of the engine load in the track normal range (track normal load upper limit value). The torque line T2 may be set so as to be included in the track normal range, and it is not always necessary to match the track normal load upper limit value as in the example of FIG. Furthermore, the torque line T2 in the example of FIG. 4 is set to a value that is substantially parallel to the downward movement of the torque line T1, but if the torque line T2 is positioned below the torque line T1 at any number of rotations. It is assumed that it is not limited to the example of FIG. The specific logic of the engine load control performed in this embodiment is shown below.

(1) At light load pattern First, when the load of the hydraulic pump 24 (hydraulic pump absorption torque) is small and the average load of the engine 21 (engine load index value) is less than or equal to the value on the torque line T2 (second operation region) (When included in R2), it is determined that the "light load pattern is in effect", and normal engine load control is performed in the first operation region R1 as shown in the lower right diagram in FIG. The engine load is controlled according to the absorption torque. At this time, since the engine load is controlled in the second operation region R2 and the hydraulic pump absorption torque can be output by the engine 21 alone, the assist by the motor 22 is not performed.

(2) During high-load continuous operation Next, when the hydraulic pump load is large and the average load (engine load index value) of the engine 21 exceeds the torque line T2, it is determined that the operation is during high-load continuous operation. 4, the engine torque is limited (reduced) to the torque level of the engine load reference value T2, which is the upper limit value of the second operation region R2, with respect to the required torque for the engine 21 exceeding T2. . Then, in order to compensate for the difference between the engine torques T1 and T2, the assist motor 22 performs torque assist. In this case, when the motor 22 is unusable due to a small amount of power stored in the battery 23, the engine is temporarily switched to the engine single operation (for example, until the motor 22 becomes usable).

In FIG. 4, the load of the engine 21 is indicated by the engine torque. However, in the description of FIG. 5 and subsequent drawings, the load of the engine 21 is first expressed as a ratio of the engine torque to the engine maximum torque at the engine speed at that time. It is indicated by a certain “engine load factor”. Then, a time-series simple moving average (engine average load factor) of the engine load factor is adopted as an index value (engine load indicator value) indicating the engine load. Furthermore, instead of the engine load reference value of FIG. 4, the “engine load factor reference value” is used in the description of FIG. 5 and the following, and in the following, the engine load index value is held below the engine load factor reference value. A case where engine load control (engine load control) is performed will be described.

First, the concept regarding the setting of the “engine load factor reference value” will be described with reference to FIG. FIG. 5 shows the distribution of operating points (combinations of engine speed and engine load factor) of the truck engine on a general road. On the straight line “rated torque” in the figure, the engine is at full load, and the engine load factor is 100%.

As shown in this figure, the load factor distribution of the engine in the truck can be regarded as a normal distribution, and is almost concentrated in the range of the average value of engine load factor ± 2σ. Therefore, the range of the engine load factor average value ± 2σ is regarded as a normal range (load factor normal range) in the truck engine, and the upper limit value is set as the engine load factor reference value. The upper limit value of the engine load factor distribution is statistically frequently found in the engine load factor range of 50 to 70%. Therefore, the engine load factor is preferably set to 70% or less. In other words, in terms of the engine load, it is a guideline to set the engine load factor reference value to a load of 70% or less of the total engine load.

Next, the specific control contents of the engine load control will be described using the time charts shown in FIGS. In the hydraulic excavator according to FIGS. 6 and 7, the relationship between the hydraulic pump absorption torque and the engine drive torque is always maintained by engine speed feedback control, which will be described later, and the hydraulic pump absorption torque changes stepwise. The engine driving torque is also configured to follow in synchronization. In FIGS. 6 and 7, the hydraulic pump load factor moving average value, which is a time-series moving average of the hydraulic pump load factor, and the engine load factor moving average value, which is the time-series moving average of the engine load factor, are indicated by bold lines. An engine load factor reference value determined based on a load factor distribution of a truck engine which is a base of a hydraulic excavator engine is indicated by a broken line. The bold hydraulic pump load factor moving average value and the engine load factor moving average value respond slowly to feedback control and smoothing processing with respect to step changes in the hydraulic pump absorption torque and engine drive torque.

FIG. 6 shows, as a comparison target of the first embodiment of the present invention (see FIG. 7), the hydraulic pump load factor (the hydraulic pump absorption torque converted into the load factor) and the engine when engine load control is not performed. The time chart of a load factor (what converted engine drive torque into a load factor) is shown. When attention is paid to the magnitude relationship between the engine load factor moving average value and the engine load factor reference value in FIG. 6, the engine load factor moving average value exceeds the engine load factor reference value in the sections of time T1 to T3 and T5 to T8. The engine load is high compared to the features of the base engine (truck engine).

On the other hand, FIG. 7 shows a time chart of the hydraulic pump load factor and the engine load factor when the engine load control according to the first embodiment is performed. The engine load factor moving average value reaches the engine load factor reference value at time T1 as in the case of non-execution of the engine load control of FIG. 6, but here the engine load control functions to limit the engine torque. Thus, the engine load factor is reduced to the engine load factor reference value level. In order to prevent a shortage of power with respect to the required pump absorption torque due to a decrease in engine torque (engine output (output)) as a result of this engine load control, Compensating with the output of the assist motor 22 (that is, executing the engine assist by the assist motor 22), and executing the cooperative control in which the total output of the engine 21 and the motor 22 satisfies the required pump absorption torque, Avoid degradation and deterioration of operability.

By the way, in the present embodiment, when the storage amount (SOC) of the battery 23 falls below the target SOC by the engine assist of the assist motor 22, the hydraulic pump load factor and the engine load factor fall below the engine load factor reference value. The battery charge amount is recovered by switching the assist motor 22 from the power running mode to the power generation mode and driving the assist motor 22 with the engine 21. Therefore, in FIG. 7, even when the hydraulic pump load factor decreases at time T2, the engine is continuously driven within the range where the engine load factor reference value is the upper limit, and the assist motor 22 generates power. (Time T2 to T4). Specifically, power generation is started at time T2 when the hydraulic pump load factor and the engine load factor fall below the engine load factor reference value, and power generation occurs at time T4 when the hydraulic pump load factor and the engine load factor exceed the engine load factor reference value. Ended (suspended).

Thereafter, when a hydraulic pump load with a high load factor is generated again from time T4 to T7, the engine load factor is reduced to the engine load factor reference value level and the engine torque is reduced as in the processing from time T1 to T2. The insufficiency is assisted by the assist motor 22 and the cooperative control by the engine 21 and the motor 22 is performed.

Incidentally, whether or not the engine assist by the assist motor 22 can be performed is determined in consideration of the amount of power stored in the battery 23. In the present embodiment, when the battery 23 storage amount (SOC) is reduced to the lower limit due to engine assist by the assist motor 22 (time T6), the assist motor 22 cannot be driven, so at the time T6. The driving of the assist motor 22 is stopped and the engine is switched to the single operation (time T6 to T7). Thereafter, in the same manner as at times T2 to T4, for the purpose of recovering the battery power storage amount to the target value, the engine is continuously driven within the range where the engine load factor reference value is the upper limit, and electric power is generated (time T7 to T7 T9). Here, the battery charge amount that determines whether or not the assist motor 22 can perform the engine assist is set as the “lower limit value”. However, whether or not the engine assist is performed is determined based on other SOC values. Also good.

Next, an outline of a control block for realizing engine load control according to the first embodiment will be described with reference to FIG. The hydraulic excavator 1 according to the present embodiment includes a main control unit 101, a monitor unit 102, an engine control unit 103, a battery control unit 105, a motor control unit 104, a hydraulic pump 24, and the like as control units and actuators related to engine load control. It has.

Here, the main control unit 101 and its peripheral calculation blocks will be described. The main control unit 101 includes a target engine speed calculation unit 501, an engine load factor reference value calculation unit 502, an engine load factor calculation unit 503, an engine load factor moving average value calculation unit 504, and a motor drive torque request during power generation. A value calculation unit 505, a hydraulic pump absorption torque request value calculation unit 506, an engine torque limit value calculation unit 507, a motor assist torque basic value calculation unit 508, and a hydraulic pump absorption torque target knowledge calculation unit 509 are provided.

The target engine speed calculation unit 501 calculates the target engine speed based on the input of the engine control dial 202 shown in FIG. 3 and transmits the calculation result to the engine control unit 103 and the motor control unit 104. To do. Further, the engine control unit 103 performs feedback control related to the engine speed based on the difference between the received target engine speed and the actual engine speed, and keeps the engine speed at the target value. Further, in the motor control unit 104, when the engine speed does not converge to the target value only by the engine speed feedback control, such as when the engine torque is limited, the target engine speed and the actual engine speed Feedback control based on the motor torque determined using the difference in the numbers as input is performed on the assist motor 22 in parallel to assist the convergence of the engine speed to the target value.

The engine load factor reference value calculation unit 502 calculates an engine load factor reference value based on various parameters indicating the engine state input from the engine control unit 103. For example, when the engine load factor reference value is a value that changes according to the engine speed, the engine load factor reference value is calculated based on the engine speed at that time. In addition, when the engine load factor reference value is a constant value, a constant value is output to the engine torque limit value calculation unit 507.

The engine load factor calculation unit 503 calculates the engine load factor based on parameter information (for example, fuel injection amount) related to the engine load input from the engine control unit 103. For example, the engine torque is estimated by inputting the fuel injection amount, the maximum engine torque at the engine speed is calculated by inputting the engine speed, and the ratio of the engine torque to the maximum engine torque becomes the engine load factor.

The engine load factor moving average value calculation unit 504 performs a moving average process on the engine load factor time-series data calculated by the engine load factor calculation unit 503 to obtain an engine load factor moving average value (engine load index value). calculate. By taking the moving average, instantaneous fluctuations in the engine load factor are discarded, and the fluctuation tendency of the engine load factor can be easily grasped.

In the power generation motor drive torque request value calculation unit 505, a motor necessary for carrying out motor power generation with the target of a desired charged amount based on information on the charged amount (SOC) of the battery 23 input from the battery control unit 105. Calculate the drive torque. Further, the hydraulic pump absorption torque request value calculation unit 506 is based on the hydraulic lever absorption torque (hydraulic pump) necessary for the hydraulic pump 24 to generate desired pressure oil based on the operation lever signal information 205 shown in FIG. Required torque).

In the engine torque limit value calculation unit 507, the magnitude relationship between the engine load factor reference value input from the calculation unit 502 and the engine load factor moving average value input from the calculation unit 504, and the motor during power generation input from the calculation unit 505 The engine torque limit value is calculated in consideration of information such as the drive torque request value and the hydraulic pump absorption torque request value input from the calculation unit 506, and this is calculated using the engine control unit 103, the monitor unit 102, and the motor assist torque basic value calculation. Transmit to the means 508. The specific contents of the processing executed by the engine torque limit value calculation unit 507 of the present embodiment will be described in detail with reference to FIG.

The engine control unit 103 functions as an output adjusting unit that adjusts the output (output) of the engine 21, and includes a feedback control unit 103a and a torque limiting unit 103b. The output of the engine 21 can be quantified by, for example, the engine output proportional to the product of the engine torque and the engine speed, or the engine torque.

The feedback control unit 103a of the present embodiment determines the target value of the engine torque by feedback control so that the difference between the target engine speed and the actual engine speed decreases. Then, if the target value of the engine torque input from the feedback control unit 103a is equal to or less than the engine torque limit value input from the engine torque limit value calculation unit 507, the torque limiter 103b sets the engine torque target value as the target fuel. A command value is output to the engine 21 in terms of the injection amount. That is, the torque of the engine 21 is controlled to the target value determined by the feedback control unit 103a. On the other hand, when the engine torque target value exceeds the engine torque limit value from the feedback control unit 103a, the engine torque limit value is converted into a target fuel injection amount and a command value is output to the engine 21. That is, in this case, the torque of the engine 21 is controlled to be reduced to the engine torque limit value, and becomes a value smaller than the initial target value.

The motor assist torque basic value calculation unit 508 calculates a motor assist torque basic value based on the difference between the engine torque limit value and the hydraulic pump absorption torque request value, and transmits it to the motor control unit 104. The hydraulic pump absorption torque target value calculation unit 509 calculates a hydraulic pump absorption torque target value based on the hydraulic pump absorption torque request value from the calculation unit 506, and transmits a command value to the hydraulic pump 24.

Next, a calculation flowchart of the engine load control logic executed by the hydraulic excavator according to the first embodiment will be described with reference to FIG.

After the calculation is started in calculation step S601, the engine load factor reference value calculation unit 502 calculates the engine load factor reference value A (see the following formula 1) in calculation step S602. The engine load factor reference value in the present embodiment is a value less than 1, for example, 0.7.

A = ENGLD_RATIO_REF (1)

Next, the engine torque B (see the following formula 2) is obtained from the engine control unit 103 in calculation step S603.

B = ENGTRQ (2)

Next, the maximum engine torque C (see Equation 3 below) is obtained from the engine control unit 103 in calculation step S604.

C = ENGTRQ_MAX (3)

Next, in calculation step S605, the engine load factor calculation unit 503 calculates the engine load factor D (see the following equation 4) from the engine torque B and the maximum engine torque C.

D = ENGLD_RATIO = B / C (4)

Next, in calculation step S606, the engine load factor moving average value calculation unit 504 performs a moving average process in time series of the engine load factor D, thereby obtaining an engine load factor moving average value E (see Equation 5 below). Calculate.

E = ENGLD_RATIO_AVE = average (D) (5)

Next, in calculation step S607, the power generation motor drive torque request value calculation unit 505 generates the power generation motor drive torque request value F (see Equation 6 below) based on the battery SOC or the like obtained from the battery control unit 105. Calculate.

F = REQ_GEN_ENGTRQ (6)

Next, in calculation step S608, the hydraulic pump absorption torque request value calculation unit 506 calculates the hydraulic pump absorption torque request value G (see the following formula 7) based on the operation lever signal and the like.

G = REQ_GEN_PMPTRQ (7)

Next, in calculation step S609, the engine torque limit value calculation unit 507 calculates the engine load factor request value H (described below) from the power generation motor drive torque request value F, the hydraulic pump absorption torque request value G, and the maximum engine torque C. (See equation 8).

H = (F + G) / C (8)

Next, in calculation step S611, it is determined whether or not it is necessary to execute engine load control, which is a feature of the present invention. Specifically, the engine torque limit value calculation unit 507 determines whether or not the engine load factor moving average value E and the engine load factor request value H are higher than the engine load factor reference value A, respectively. Judge whether or not to execute.

E ≧ A (9)
H ≧ A (10)

Here, when the above formulas (9) and (10) are not established in the calculation step S611 (in the case of No), the process proceeds to the calculation step S631. On the other hand, when the above equations (9) and (10) are satisfied (in the case of Yes), the process proceeds to calculation step S612.

In calculation step S612, the battery SOC (I (see the following equation 11)) and the battery SOC lower limit threshold (J (see the following equation 12)) at that time are obtained from the battery control unit 105.

I = BAT_SOC (11)
J = BAT_SOC_SL (12)

Next, in calculation step S613, it is determined whether or not the battery SOC (I) is higher than the battery SOC lower limit threshold (J). That is, it is determined whether or not engine assist by the assist motor 22 is possible.

I ≧ J (13)

Here, in the calculation step S613, when the calculation formula (13) is not established (in the case of No), the process proceeds to the calculation step S631. When the calculation formula (13) is satisfied (in the case of Yes), the process proceeds to calculation step S614.

In calculation step S614, the engine torque limit value calculation unit 507 calculates an engine torque limit value K (see the following formula 14).

K = C x A (14)

Next, in calculation step S615, the motor assist torque basic value calculation unit 508 calculates a motor assist torque basic value L (see the following formula 15). That is, a value obtained by subtracting the engine torque limit value K from the hydraulic pump absorption torque request value G is set as the motor assist torque basic value L.

L = GK (15)

Next, in calculation step S616, the hydraulic pump absorption torque target value calculation unit 509 calculates the hydraulic pump absorption torque target value M (see the following equation 16) based on the hydraulic pump absorption torque request value G.

M = G (16)

Next, in calculation step S617, the engine control unit 103 controls the engine torque with the engine torque limit value K, and the motor control unit 104 controls the motor torque with the motor assist torque basic value L. Motor-assisted cooperative control is performed.

Next, in calculation step S618, the fact that the engine torque limit control has been performed is transmitted to the monitor unit 102, and that effect (for example, a warning) is displayed on the monitor. Thereafter, the process proceeds to calculation step S631, the engine load control related to the control cycle is terminated, and the process returns to calculation step S601.

In the example of FIG. 9, the fact that the engine torque limit has been executed in the calculation step S618 is displayed on the monitor in the cab of the hydraulic excavator 1. However, in accordance with or instead of this, the outside of the hydraulic excavator 1 is displayed. You may transmit to the installed computer. When the computer is owned and managed by the owner or management company of the excavator 1, for example, the time when the engine torque limit control is executed can be recorded in the computer. This can be used as an index for determining the maintenance time of the hydraulic excavator.

As described above, the engine load control content in the first embodiment is that the engine load factor moving average value is always calculated and the engine load factor moving average value exceeds the engine load factor reference value. The engine torque is reduced to lower the engine load factor moving average value to the engine load factor reference value level, and the assist motor 22 is driven for the deficiency with respect to the required hydraulic pump absorption torque, Implement coordinated control of engine and motor.

This makes the engine load factor at the time of excavator operation close to the engine load factor equivalent to that of a truck engine and reduces the load on the engine, thereby facilitating the diversion of the truck engine. Furthermore, if the engine load factor of a hydraulic excavator can be reduced and controlled to the same level as a vehicle engine, an inexpensive general-purpose vehicle engine can be installed as a hydraulic excavator engine without major specification changes. This makes it possible to greatly reduce the manufacturing cost of hydraulic excavators. Further, by compensating for the decrease in the engine torque with the motor torque of the assist motor 22, it is possible to avoid a decrease in work and a deterioration in operability.

The parameters relating to the load of the engine 21 are not limited to the engine load factor used above, but as alternative parameters, engine torque, engine speed, engine intake pressure, engine cylinder pressure, fuel injection amount, and turbine rotation in the turbocharger At least one of various parameters indicating the engine state (engine state parameter) may be used, and a calculated value related to the engine load calculated from at least one of these parameters is used. You may do it.

The smoothing process applied to the engine load factor in time series uses not only the simple moving average process used above, but also other moving average processes including cumulative moving averages and filter processes including low-pass filter processes. May be. In the case where the time constant is used in the smoothing process, the time constant may be determined based on the thermal time constant of the engine body.

In the first embodiment, the upper limit value of the engine load factor for trucks is set as the engine load factor reference value. However, the upper limit value may be variable according to the soundness of the engine based on this value. For example, when an abnormality relating to engine failure or fuel properties is recognized, the engine load factor reference value may be reduced below a default value (the reference value described above).

Next, a second embodiment according to the present invention will be described with reference to FIGS. Unlike the hybrid type of the first embodiment, the hydraulic excavator of the second embodiment is a standard type hydraulic excavator in which the drive source of the hydraulic pump is only an engine. In the following, the system configuration will be described focusing on the differences from the hybrid hydraulic excavator of the first embodiment.

FIG. 10 is a diagram showing an overall system configuration of the excavator 1 in the second embodiment. The overall system configuration is almost the same as that of the first embodiment, but for the standard excavator, the configuration in which the assist motor 22 and the battery 23 are removed from the configuration diagram of the first embodiment shown in FIG. It has become.

FIG. 11 is a diagram showing a hydraulic excavator engine according to the second embodiment and the surrounding system configuration. This is also almost the same configuration as the configuration of the first embodiment shown in FIG. 3, but for a standard hydraulic excavator, it is a hybrid related device (assist motor 22, battery 23) and control unit (motor control unit 104). The battery control unit 105) has been removed.

Next, specific control contents of engine load control in the second embodiment will be described with reference to time charts shown in FIGS. FIG. 12 shows a time chart of the hydraulic pump load factor and the engine load factor when engine load control is not performed as a comparison target of the second embodiment (see FIG. 13) of the present invention. When engine load control is not performed, the engine load factor moving average value exceeds the engine load factor reference value at times T1 to T3, and this is a section where the load on the engine is large.

On the other hand, FIG. 13 shows a time chart of the hydraulic pump load factor and the engine load factor when the engine load control according to the second embodiment is performed. In the second embodiment, the engine torque is limited to the engine load factor reference value level by limiting the engine torque from time T1 to time T2 when the engine load factor moving average value reaches the engine load factor reference value. At the same time, the hydraulic pump absorption torque (hydraulic pump load factor) is reduced to the same level as the engine load factor in synchronization with the engine torque limitation.

Although this work temporarily reduces the work load, the engine load factor moving average value can be kept within a desired range, and the engine generated when the hydraulic pump absorption torque is excessive with respect to the engine torque Since the stall is avoided, the minimum operability can be secured.

Next, the main control unit 101 and its peripheral calculation blocks in the second embodiment will be described with reference to FIG. The difference from the calculation block of the first embodiment shown in FIG. 8 is that the motor control unit 104, the battery control unit 105, and the motor assist torque basic value calculation unit 508 are excluded as external control units. .

The hydraulic pump absorption torque target value calculation unit 509 is based on the hydraulic pump absorption torque request value output from the hydraulic pump absorption torque request value calculation unit 506 and the engine torque limit value output from the engine torque limit value calculation unit 507. Then, the hydraulic pump absorption torque target value in the hydraulic pump absorption torque limitation synchronized with the engine torque limitation is calculated.

Next, a calculation flowchart of the engine load control logic executed by the excavator according to the second embodiment will be described with reference to FIG.

After the calculation is started in calculation step S601, the engine load factor reference value A (see the following formula 21) is calculated in calculation step S602. The engine load factor reference value in the present embodiment is a value less than 1, for example, 0.7.

A = ENGLD_RATIO_REF (21)

Next, the engine torque B (see the following formula 22) is obtained from the engine control unit 103 in calculation step S603.

B = ENGTRQ (22)

Next, the maximum engine torque C (see Equation 23 below) is obtained from the engine control unit 103 in calculation step S604.

C = ENGTRQ_MAX (23)

Next, in calculation step S605, the engine load factor calculation unit 503 calculates the engine load factor D (see the following equation 24) from the engine torque B and the maximum engine torque C.

D = ENGLD_RATIO = B / C (24)

Next, in calculation step S606, the engine load factor moving average value calculation unit 504 performs a moving average process in time series of the engine load factor D, thereby obtaining an engine load factor moving average value E (see the following Expression 25). Calculate.

E = ENGLD_RATIO_AVE = average (D) (25)

Next, in calculation step S608, the hydraulic pump absorption torque request value calculation unit 506 calculates the hydraulic pump absorption torque request value G (see the following equation 26) based on the operation lever signal and the like.

G = REQ_GEN_PMPTRQ (26)

Next, in calculation step S609, the engine torque limit value calculation unit 507 calculates the engine load factor request value H (see the following Expression 27) from the hydraulic pump absorption torque request value G and the maximum engine torque C.

H = G / C (27)

E ≧ A (28)
H ≧ A (29)

Here, when the above formulas (28) and (29) are not established in the calculation step S611 (in the case of No), the process proceeds to the calculation step S631. On the other hand, when the above equations (28) and (29) are satisfied (in the case of Yes), the process proceeds to calculation step S621.

In calculation step S621, the engine torque limit value calculation unit 507 calculates the engine torque limit value K. Specifically, the hydraulic pump absorption torque is gradually reduced from the torque value G to a value corresponding to the engine load factor reference value C × A with time, and more specifically calculated by the following equation (30). To do.

K = max (G x reduction factor, C x A) (30)

Next, in calculation step S622, the hydraulic pump absorption torque target value calculation unit 509 calculates a hydraulic pump absorption torque target value M (see the following equation 31) based on the engine torque limit value K.

M = K (31)

Next, in calculation step S623, the engine control unit 103 controls the engine torque with the engine torque limit value K, and the hydraulic pump absorption torque target value calculation unit 509 controls the hydraulic pump 24 with the hydraulic pump absorption torque target value M. Thus, engine torque limitation and output limitation of the hydraulic pump 24 are performed.

Next, in calculation step S624, the fact that the engine torque limit control has been performed is transmitted to the monitor unit 102, and that fact (for example, a warning) is displayed on the monitor. Thereafter, the process proceeds to calculation step S631, the engine load control related to the control cycle is terminated, and the process returns to calculation step S601.

As described above, the engine load control content in the second embodiment is that when the moving average value of the engine load factor is constantly calculated and the engine load factor moving average value exceeds the engine load factor reference value, The engine torque is lowered to lower the engine load factor moving average value to the engine load factor reference value level, and the hydraulic pump absorption torque is reduced in synchronization with the engine torque limit.

Therefore, also in this embodiment, while avoiding deterioration in operability, the engine load factor at the time of excavator operation can be brought close to the engine load factor equivalent to that of a truck engine. It can be installed as an excavator engine without changing specifications.

In the above description, the engine load factor moving average value E (that is, the actual value of the engine load factor) and the engine load factor requirement value H are the engine load factor reference values in the calculation step S611 of FIG. 9 and FIG. It is determined whether or not the engine load control is executed, and it is determined whether or not only the engine load factor moving average value E, which is the actual value of the engine load factor, is higher than the engine load factor reference value A. The effect of the present invention is exhibited even if it is determined whether or not the engine load control is executed. However, as described above, when it is determined whether both the actual value E and the required value H are higher than the reference value A and whether or not the engine load control is executed, the engine load (for example, engine torque) is determined. There is an advantage that hunting can be prevented.

In the above description, a hydraulic excavator has been described as an example of the construction machine. However, the present invention can also be applied to other construction machines including a wheel loader that drives a hydraulic pump by an engine to drive various hydraulic actuators. It is.

Further, the present invention is not limited to the above-described embodiment, and includes various modifications within the scope not departing from the gist thereof. For example, the present invention is not limited to the one having all the configurations described in the above embodiment, and includes a configuration in which a part of the configuration is deleted. In addition, part of the configuration according to one embodiment can be added to or replaced with the configuration according to another embodiment.

In addition, each configuration relating to the above-described computer, functions and execution processing of each configuration, and the like are realized by hardware (for example, logic for executing each function is designed by an integrated circuit). Also good. Further, the configuration related to the computer may be a program (software) in which each function related to the configuration of the computer is realized by being read and executed by an arithmetic processing device (for example, CPU). Information related to the program can be stored in, for example, a semiconductor memory (flash memory, SSD, etc.), a magnetic storage device (hard disk drive, etc.), a recording medium (magnetic disk, optical disc, etc.), and the like.

In the above description of each embodiment, the control line and the information line are shown to be understood as necessary for the description of the embodiment, but all the control lines and information lines related to the product are not necessarily included. It does not always indicate. In practice, it can be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 1 ... Hydraulic excavator, 2 ... Working apparatus, 3 ... Vehicle body, 4 ... Upper turning body, 5 ... Lower traveling body, 6 ... Boom, 7 ... Arm, 8 ... Bucket, 9 ... Boom cylinder, 10 ... Arm cylinder, 11 ... Bucket cylinder, 21 ... diesel engine, 22 ... assist motor, 23 ... battery, 24 ... hydraulic pump, 25 ... control valve, 26 ... hydraulic oil tank, 31 ... turning hydraulic motor, 32 ... turning speed reducer, 33 ... turning gear, DESCRIPTION OF SYMBOLS 41 ... Center joint, 42 ... Travel hydraulic motor, 43 ... Travel reduction device, 44 ... Crawler, 101 ... Main control unit, 102 ... Monitor unit, 103 ... Engine control unit, 104 ... Motor control unit, 105 ... Battery control unit, 201 ... Key switch, 202 ... Engine controller Tall dial, 203 ... auto idle switch, 204 ... power mode switch, 205 ... operating lever signal, 301 ... fuel injection device, 302 ... exhaust manifold, 303 ... turbocharger, 304 ... exhaust pipe, 305 ... output shaft, 306 ... rotation Sensor: 307 ... Supercharging pressure sensor, 401 ... DPF device, 402 ... Oxidation catalyst, 403 ... PM collection filter, 404 ... Exhaust temperature sensor, 405 ... DPF differential pressure sensor, 501 ... Target engine speed calculation unit, 502 ... Engine load factor reference value calculation unit, 503 ... Engine load factor calculation unit, 504 ... Engine load factor moving average value calculation unit, 505 ... Motor drive torque request value calculation unit during power generation, 506 ... Hydraulic pump absorption torque request value calculation unit, 507 ... Engine torque limit value calculation unit, 508 ... Motor assist torque base Value calculation unit, 509 ... hydraulic pump absorption torque target value calculation unit

Claims

An engine that drives a hydraulic pump;
A load index calculation unit for calculating an engine load index value indicating a tendency of time change of a parameter related to the engine load;
An output adjustment unit for adjusting the output of the engine,
The engine operating region defined by the engine speed and the load includes a first operating region consisting of a region from no load to full load, and the first operating region included in the first operating region. A narrow second operating range is set,
The engine control device for a construction machine, wherein the output adjustment unit adjusts the output of the engine so that the engine load index value falls within the second operation region.
The engine control device for a construction machine according to claim 1,
The engine load index value is obtained by performing a smoothing process on a time series of parameters related to the engine load,
The engine load index value is set with a reference value that is an upper limit value of the second operation region that is determined to continuously use the engine in a predetermined range of less than full load.
The engine control device for a construction machine, wherein the reference value is set to a value less than the value of the parameter when the engine is at full load.
The construction machine engine control device according to claim 2,
The engine is a vehicle engine designed for vehicles;
The engine control apparatus for construction machinery, wherein the reference value is set to an upper limit value of the engine load index value in a normal range of the vehicle engine.
The construction machine engine control device according to claim 3,
The engine control apparatus for construction machinery, wherein the reference value is set to a value when the engine load is 70% or less of the total load.
The construction machine engine control device according to claim 4,
The parameters relating to the engine load include engine torque, engine speed, engine intake pressure, engine cylinder pressure, fuel injection amount, turbine speed in the turbocharger, required torque of the hydraulic pump, engine load, and engine load. An engine control device for a construction machine, characterized in that it is one of the ratios.
The construction machine engine control device according to claim 4,
The engine control device for a construction machine, wherein the smoothing process is calculated by a moving average or a filter process.
The engine control device for a construction machine according to claim 1,
A motor for assisting the engine;
The construction machine engine control device according to claim 1, wherein the motor compensates for a decrease in the engine output when the engine output decreases due to the output adjustment of the engine by the output adjustment unit.
The engine control device for a construction machine according to claim 1,
The engine control device for a construction machine, wherein the hydraulic pump reduces the output in accordance with the decrease in the engine output when the engine output decreases due to the output adjustment of the engine by the output adjusting unit.
The engine control device for a construction machine according to claim 7,
A power storage device in which electric power supplied to the motor is stored;
The engine control device for a construction machine, wherein whether or not the engine can be assisted by the motor is determined in consideration of the amount of power stored in the power storage device.