JP5250145B2 - Engine control device - Google Patents

Description

  The present invention relates to an engine control device used when a hydraulic pump is driven by an engine.

  Conventionally, diesel engines are mounted on construction machines such as hydraulic excavators, bulldozers, dump trucks, and wheel loaders.

  A schematic configuration of a conventional construction machine 100 will be described with reference to FIG. As shown in FIG. 21, the construction machine 100 drives the hydraulic pump 3 using the engine 2 that is a diesel engine as a drive source. As the hydraulic pump 3, a variable displacement hydraulic pump is used, and the capacity q (cc / rev) is changed by changing the tilt angle of the swash plate 3a. Pressure oil discharged from the hydraulic pump 3 at the discharge pressure PRP and the flow rate Q (cc / min) is supplied to the hydraulic actuators 31 to 36 such as the boom cylinder 31 via the operation valves 21 to 26. The operation valves 21 to 26 are actuated by operating the operation levers 41 and 42. By supplying pressure oil to each hydraulic actuator 31-36, each hydraulic actuator 31-36 is driven, and a working machine including a boom, an arm, and a bucket connected to each hydraulic actuator 31-36, a lower traveling body, The upper swing body is activated. While the construction machine 100 is in operation, the load applied to the work machine, the lower traveling body, and the upper turning body constantly changes according to the excavated soil quality, the traveling path gradient, and the like. In accordance with this, the load on the hydraulic equipment (hydraulic pump 3) (hereinafter referred to as oil machine load), that is, the load applied to the engine 2 changes.

  The output P (horsepower; kw) of the engine 2 is controlled by adjusting the amount of fuel injected into the cylinder. This adjustment is performed by controlling the governor 4 attached to the fuel injection pump of the engine 1. As the governor 4, an all-speed control type governor is generally used, and the engine speed n and the fuel injection amount (torque T) according to the load so that the target engine speed set by the fuel dial is maintained. ) And are adjusted. That is, the governor 4 increases or decreases the fuel injection amount so that the difference between the target rotation speed and the engine rotation speed is eliminated.

  FIG. 22 shows a torque diagram of the engine 2. The horizontal axis represents the engine speed n (rpm; rev / min), and the vertical axis represents the torque T (N · m). In FIG. 22, the region defined by the maximum torque line R indicates the performance that the engine 2 can produce. The governor 4 controls the engine 2 so that the torque T does not exceed the maximum torque line R and does not reach the exhaust smoke limit, and the engine speed n does not exceed the high idle speed nH and overspeed. At the rated point V on the maximum torque line R, the output (horsepower) P of the engine 2 becomes maximum. J indicates an equal horsepower curve in which the horsepower absorbed by the hydraulic pump 3 is equal horsepower.

  When the maximum target rotational speed is set by the fuel dial, the governor 4 adjusts the speed on the maximum speed regulation line Fe connecting the rated point V and the high idle point nH.

  As the load on the hydraulic pump 3 increases, the matching point at which the output of the engine 2 and the pump absorption horsepower balance moves to the rated point V side on the highest speed regulation line Fe. When the matching point moves to the rated point V side, the engine speed n is gradually reduced, and at the rated point V, the engine speed n becomes the rated speed.

  If the engine speed n is fixed at a substantially constant high speed in this way, there is a problem that the fuel consumption rate is large (poor) and the pump efficiency is low. The fuel consumption rate (hereinafter referred to as fuel consumption) refers to the amount of fuel consumed per hour and output of 1 kW, and is an index of the efficiency of the engine 2. The pump efficiency is the efficiency of the hydraulic pump 3 defined by volumetric efficiency and torque efficiency.

  In FIG. 22, M indicates an equal fuel consumption curve. The fuel consumption is minimized at M1 that is the valley of the equal fuel consumption curve M, and the fuel consumption increases toward the outside from the fuel consumption minimum point M1.

  As is clear from FIG. 22, the regulation line Fe corresponds to a region where the fuel consumption is relatively high on the equal fuel consumption curve M. For this reason, according to the conventional control method, fuel consumption is large (poor), which is not desirable in terms of engine efficiency.

  On the other hand, in the case of the variable displacement hydraulic pump 3, in general, when the discharge pressure PRP is the same, the larger the pump capacity q (swash plate tilt angle), the higher the volume efficiency and torque efficiency, and the higher the pump efficiency. Are known.

  As is clear from the following equation (1), if the flow rate Q of the pressure oil discharged from the hydraulic pump 3 is the same, the pump capacity q is increased as the rotational speed n of the engine 2 is decreased. Can do. For this reason, if the engine 2 is slowed down, the pump efficiency can be increased.

Q = n · q (1)
Therefore, in order to increase the pump efficiency of the hydraulic pump 3, the engine 2 may be operated in a low speed region where the rotational speed n is low.

  However, as is apparent from FIG. 22, the regulation line Fe corresponds to a high speed region of the engine 2. For this reason, according to the conventional control method, there exists a problem that pump efficiency is low.

  In addition, when the engine 2 is operated on the regulation line Fe, the engine speed decreases when the load is high, which may lead to engine stall.

  Patent Document 1 discloses a control method in which the engine speed is changed according to the lever operation amount and the load, in contrast to the control method in which the engine speed is substantially fixed regardless of the load.

  In Patent Document 1, as shown in FIG. 22, a target engine operating line L0 passing through the minimum fuel consumption point M1 is set.

  Then, based on the operation amount of each operation lever 41, 42, 43, 44, etc., the required rotational speed of the hydraulic pump 3 is calculated, and the first engine required rotational speed corresponding to this pump required rotational speed is calculated. . Further, the required engine horsepower is calculated based on the operation amount of each operation lever 41, 42, 43, 44, etc., and the second required engine speed corresponding to this required engine horsepower is calculated. Here, the second required engine speed is calculated as the engine speed on the target engine operating line L0 in FIG. Then, the engine speed and the engine torque are controlled so that the larger engine target speed of the first and second engine required speeds can be obtained.

  As shown in FIG. 22, when the rotational speed of the engine 2 is controlled along the target engine operation line L0, fuel efficiency, engine efficiency, and pump efficiency are improved. This means that even when the same horsepower is output and the same required flow rate is obtained, the point pt2 on the target engine operating line L0 is the same point on the equal horsepower line J rather than matching at the point pt1 on the regulation line Fe. This is because the matching is performed at a point close to the minimum fuel consumption point M1 on the equal fuel consumption curve M because the pump displacement q is increased from high rotation and low torque to low rotation and high torque. . Further, when the engine 2 is operated in the low rotation region, noise is improved, and engine friction, pump unload loss, and the like are improved.

  In the field of construction machinery, a hybrid construction machine that assists the driving force of an engine with a generator motor is being developed, and many patent applications have already been filed.

  For example, in Patent Document 2, when FIG. 22 is used, the engine 2 is controlled along the regulation line Fe0 corresponding to the set rotational speed set by the fuel dial. When the target rotational speed nr corresponding to the point A where the regulation line Fe0 and the target engine operating line L0 intersect is obtained, and the deviation between the engine target rotational speed nr and the current engine rotational speed n is positive, the generator motor , And the driving force of the engine 2 is assisted by the torque generated by the generator motor. When the deviation is negative, the generator motor is caused to generate power and the electric power is accumulated in the capacitor.

JP-A-11-2144 JP 2003-28071 A

  By the way, in the invention described in Patent Document 1, the target engine speed is determined according to the load of the hydraulic pump 3. Then, as shown in FIG. 22, the matching point moves from B to A toward the high load side on the target engine operating line L0 as the hydraulic pump 3 becomes higher in load. Here, if the work machine hits a hard load such as a hard bedrock, the pump pressure suddenly rises and the relief valve operates, causing extra energy loss. The pump capacity was changed to reduce the relief flow rate.

  However, when the pump capacity is reduced to reduce the relief flow rate, there is a problem that the pump efficiency is lowered. In this case, since the engine speed is higher than the optimum engine speed, there is a problem that the efficiency of the engine is poor.

  The present invention has been made in view of the above, and an object of the present invention is to provide an engine control device that can improve pump efficiency and engine efficiency at high loads such as during relief.

  In order to solve the above-described problems and achieve the object, an engine control apparatus according to the present invention includes a hydraulic pump driven by the engine, a hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied, An operation means for operating each hydraulic actuator, a first target rotation speed setting means for setting a first target rotation speed of the engine, and a maximum target rotation speed of the engine are limited as the load pressure of the hydraulic pump increases. A second target rotational speed calculating means for calculating the second target rotational speed, and a lower target rotational speed that is one of the first target rotational speed and the second target rotational speed, And a rotational speed control means for controlling the engine rotational speed.

  In the engine control apparatus according to the present invention, in the above invention, the first target rotational speed setting means calculates a first target rotational speed of the engine according to an operation amount of the operating means. It is characterized by that.

  In the engine control device according to the present invention, the horsepower for calculating the pump horsepower limit value so that the horsepower that can be absorbed by the hydraulic pump decreases as the load pressure of the hydraulic pump increases. The second target rotation speed calculation means includes a limit value calculation means, and the second target rotation speed calculation means limits the maximum target rotation speed of the engine according to the horsepower limit value of the hydraulic pump calculated by the horsepower limit value calculation means. The second target rotational speed is calculated.

  Further, in the engine control device according to the present invention, in the above invention, when the load pressure of the hydraulic pump exceeds a value smaller than a preset value with respect to the relief pressure, the horsepower that can be absorbed by the hydraulic pump The second target rotational speed calculation means is responsive to the horsepower limit value of the hydraulic pump calculated by the horsepower limit value calculation means. The second target rotational speed is calculated so as to limit the maximum target rotational speed of the engine.

  In the engine control apparatus according to the present invention, the maximum controllable torque that can be absorbed by the hydraulic pump is determined according to the horsepower limit value of the hydraulic pump calculated by the horsepower limit value calculating means. An absorption torque control means is provided.

  The engine control apparatus according to the present invention includes, in the above invention, a generator motor connected to the output shaft of the engine, a capacitor that stores electric power generated by the generator motor and supplies electric power to the generator motor. When the load pressure of the hydraulic pump is suddenly switched from a high state to a low state, the engine of the generator motor until the actual rotational speed of the engine rises to a value set in advance with respect to the target rotational speed And a control means for controlling the engine speed so as to coincide with the target speed by using a torque assist action.

  The engine control apparatus according to the present invention includes, in the above invention, a generator motor connected to the output shaft of the engine, a capacitor that stores electric power generated by the generator motor and supplies electric power to the generator motor. As the load pressure of the hydraulic pump decreases from a high state to a low state, the second target rotational speed increases so that the actual rotational speed of the engine is a value set in advance from the target rotational speed. If it is smaller than the target rotational speed, the actual rotational speed will be equal to the target rotational speed using the engine torque assist action of the generator motor until the actual rotational speed rises to a value smaller than a preset value. And a control means for controlling the engine speed.

  In the engine control apparatus according to the present invention, the first rotation speed setting means sets the first target rotation speed of the engine, and the second target rotation speed calculation means increases the load pressure of the hydraulic pump. And calculating a second target rotational speed for limiting the maximum target rotational speed of the engine, wherein the rotational speed control means is the lower target rotational speed of the first target rotational speed and the second target rotational speed. Since the engine speed is controlled so as to match the engine speed and the engine speed is lowered, the pump efficiency and the engine efficiency at the time of high load such as a relief time can be increased.

FIG. 1 is a block diagram showing a schematic configuration of a construction machine according to an embodiment of the present invention. FIG. 2 is a diagram showing a control flow of the controller shown in FIG. 1 (No. 1). FIG. 3 is a diagram showing a control flow of the target flow rate calculation unit shown in FIG. FIG. 4 is a flowchart showing a processing procedure of the engine target rotational speed addition value calculation unit shown in FIG. FIG. 5 is a diagram showing an example of processing of the target rotation speed addition value calculation unit shown in FIG. FIG. 6 is a diagram showing a processing flow of the pump output restriction calculation unit shown in FIG. FIG. 7 is a torque diagram for explaining processing by the engine target rotational speed addition value calculation unit. FIG. 8 is a diagram showing temporal changes in engine speed and engine torque for explaining processing by the engine target speed addition value calculation unit. FIG. 9 is a diagram illustrating pump output limit values corresponding to each work pattern. FIG. 10 is a diagram showing a control flow of the controller shown in FIG. 1 (part 2). FIG. 11 is a diagram illustrating a processing flow of the assist presence / absence determination unit. FIG. 12 is a diagram for explaining the operation when there is no modulation processing during engine acceleration. FIG. 13 is a diagram for explaining the operation when there is a modulation process during engine acceleration. FIG. 14 is a diagram for explaining the operation when there is no modulation processing during engine deceleration. FIG. 15 is a diagram for explaining the operation when there is a modulation process during engine deceleration. FIG. 16 is a torque diagram used for explaining the embodiment of the present invention. FIG. 17 is a torque diagram used for explaining the embodiment of the present invention. FIG. 18 is a torque diagram used for explaining the embodiment of the present invention. FIG. 19 is a block diagram showing a schematic configuration of a construction machine according to a modification of the embodiment of the present invention. FIG. 20 is a diagram showing a control flow of the controller shown in FIG. FIG. 21 is a block diagram showing a schematic configuration of a conventional construction machine. FIG. 22 is a torque diagram used to explain the prior art.

  Hereinafter, an engine control apparatus according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a case where a diesel engine and a hydraulic pump mounted on a construction machine such as a hydraulic excavator are controlled will be described.

  FIG. 1 is a diagram showing an overall configuration of a construction machine 1 according to an embodiment of the present invention. The construction machine 1 is a hydraulic excavator.

  The construction machine 1 includes an upper swing body and a lower traveling body, and the lower traveling body includes left and right crawler tracks. A work machine including a boom, an arm, and a bucket is attached to the vehicle body. The boom is operated when the boom cylinder 31 is driven, the arm is operated when the arm cylinder 32 is driven, and the bucket is operated when the bucket cylinder 33 is driven. Further, the left crawler belt and the right crawler belt rotate by driving the travel motor 36 and the travel motor 35, respectively. Also, the swing machinery is driven by driving the swing motor 34, and the upper swing body swings via a swing pinion, swing circle, and the like.

  The engine 2 is a diesel engine, and its output (horsepower; kw) is controlled by adjusting the amount of fuel injected into the cylinder. This adjustment is performed by controlling the governor attached to the fuel injection pump of the engine 2, and the engine controller 4 controls the engine including the control of the governor.

  The controller 6 outputs a rotation command value for setting the engine speed to the target speed ncom to the engine controller 4, and the engine controller 4 performs fuel so that the target speed n_com can be obtained by the target torque line L1. Increase or decrease the injection amount. Further, the engine controller 4 outputs engine data eng_data including the engine torque estimated from the engine speed of the engine 2 and the fuel injection amount to the controller 6.

  The output shaft of the engine 2 is connected to the drive shaft of the generator motor 11 via the PTO shaft 10. The generator motor 11 performs a power generation operation and an electric operation. That is, the generator motor 11 operates as an electric motor (motor) and also operates as a generator. The generator motor 11 also functions as a starter that starts the engine 2. When the starter switch is turned on, the generator motor 11 is electrically operated to rotate the output shaft of the engine 2 at a low speed (for example, 400 to 500 rpm) to start the engine 2.

  The generator motor 11 is torque-controlled by an inverter 13. As will be described later, the inverter 13 controls the torque of the generator motor 11 according to the generator motor command value GEN_com output from the controller 6.

  The inverter 13 is electrically connected to the battery 12 via a DC power line. The controller 6 operates using the battery 12 as a power source.

  The battery 12 is configured by a capacitor, a storage battery, or the like, and stores (charges) the power generated when the generator motor 11 generates power. In addition, the battery 12 supplies the electric power stored in the battery 12 to the inverter 13. In this specification, a capacitor that accumulates electric power as static electricity and a storage battery such as a lead battery, a nickel metal hydride battery, or a lithium ion battery are also referred to as a “capacitor”.

  The drive shaft of the hydraulic pump 3 is connected to the output shaft of the engine 2 via the PTO shaft 10, and the hydraulic pump 3 is driven by the rotation of the engine output shaft. The hydraulic pump 3 is a variable displacement hydraulic pump, and the capacity q (cc / rev) is changed by changing the tilt angle of the swash plate.

  Pressure oil discharged from the hydraulic pump 3 at a discharge pressure PRp and a flow rate Q (cc / min) is used for a boom operation valve 21, an arm operation valve 22, a bucket operation valve 23, and a turning operation valve 24. Are supplied to the operation valve 25 for right traveling and the operation valve 26 for left traveling, respectively. The pump discharge pressure PRp is detected by a hydraulic pressure sensor 7 and a hydraulic pressure detection signal is input to the controller 6.

  The pressure oil output from the operation valves 21 to 26 is supplied to the boom cylinder 31, the arm cylinder 32, the bucket cylinder 33, the turning motor 34, the right traveling motor 35, and the left traveling motor 36, respectively. Thereby, the boom cylinder 31, the arm cylinder 32, the bucket cylinder 33, the turning motor 34, the traveling motor 35, and the traveling motor 36 are driven, and the boom, arm, bucket, upper revolving body, and lower traveling body's right and left crawler belts. Operates.

  A right operation lever 41 for work / turning and a left operation lever 42 for work / turning are provided on the right side and the left side of the front side of the driver's seat of the construction machine 1, respectively, and the right operation lever 43 for traveling, A left operation lever 44 for traveling is provided.

  The right operation lever 41 for operation / turning is an operation lever for operating the boom and bucket. The boom and bucket are operated according to the operation direction, and the boom and bucket are operated at a speed corresponding to the operation amount. .

  The operation lever 41 is provided with a sensor 45 that detects an operation direction and an operation amount. The sensor 45 inputs a lever signal indicating the operation direction and the operation amount of the operation lever 41 to the controller 6. When the operation lever 41 is operated in the direction in which the boom is operated, the boom lever signal Lb0 indicating the boom raising operation amount and the boom lowering operation amount according to the tilt direction and the tilt amount with respect to the neutral position of the operation lever 41 is transmitted to the controller. 6 is input. When the operation lever 41 is operated in the direction in which the bucket is operated, the bucket lever signal Lbk indicating the bucket excavation operation amount and the bucket dump operation amount according to the tilt direction and the tilt amount with respect to the neutral position of the operation lever 41. Is input to the controller 6.

  When the operating lever 41 is operated in the direction in which the boom is operated, the pilot pressure (PPC pressure) PRbo corresponding to the tilting amount of the operating lever 41 is the lever tilting direction of each pilot port of the boom operating valve 21. It is added to the pilot port 21a corresponding to (the boom raising direction, the boom lowering direction).

  Similarly, when the operation lever 41 is operated in the direction in which the bucket is operated, the pilot pressure (PPC pressure) PRbk corresponding to the tilting amount of the operation lever 41 is out of the pilot ports of the bucket operation valve 23. It is added to the pilot port 23a corresponding to the lever tilting direction (bucket excavation direction, bucket dumping direction).

  The left operation lever 42 for operation / turning is an operation lever for operating the arm and the upper turning body, and operates the arm and the upper turning body according to the operation direction, and the arm at a speed according to the operation amount. Operate the upper revolving unit.

  The operation lever 42 is provided with a sensor 46 that detects an operation direction and an operation amount. The sensor 46 inputs a lever signal indicating the operation direction and the operation amount of the operation lever 42 to the controller 6. When the operation lever 42 is operated in the direction in which the arm is operated, the arm lever signal Lar indicating the arm excavation operation amount and the arm dump operation amount according to the tilt direction and the tilt amount with respect to the neutral position of the operation lever 42 is obtained from the controller. 6 is input. In addition, when the operation lever 42 is operated in a direction to operate the upper swing body, the turn lever indicating the right turn operation amount and the left turn operation amount according to the tilt direction and the tilt amount with respect to the neutral position of the operation lever 42. The signal Lsw is input to the controller 6.

  When the operation lever 42 is operated in the direction in which the arm is operated, the pilot pressure (PPC pressure) PRar corresponding to the amount of tilt of the operation lever 42 is the lever tilt direction of each pilot port of the arm operation valve 22. It is added to the pilot port 22a corresponding to (arm excavation direction, arm dump direction).

  Similarly, when the operation lever 42 is operated in the direction in which the upper swing body is operated, the pilot pressure (PPC pressure) PRsw corresponding to the tilting amount of the operation lever 42 is changed to each pilot port of the operation valve 24 for turning. Are added to the pilot port 24a corresponding to the lever tilting direction (right turning direction, left turning direction).

  The right traveling lever 43 and the left traveling lever 44 are operating levers for operating the right crawler track and the left crawler track, respectively, and operate the crawler belt according to the operation direction and at a speed corresponding to the operation amount. Activate the track.

  A pilot pressure (PPC pressure) PRtr corresponding to the tilting amount of the operation lever 43 is applied to the pilot port 25a of the right travel operation valve 25.

  The pilot pressure PRtr is detected by the hydraulic pressure sensor 9, and the right traveling pilot pressure PRcr indicating the right traveling amount is input to the controller 6. Similarly, a pilot pressure (PPC pressure) PRtl corresponding to the tilting amount of the operation lever 44 is applied to the pilot port 26 a of the left travel operation valve 26. The pilot pressure PRtl is detected by the oil pressure sensor 8, and the left traveling pilot pressure PRcl indicating the left traveling amount is input to the controller 6.

  Each of the operation valves 21 to 26 is a flow direction control valve, moves the spool in a direction corresponding to the operation direction of the corresponding operation lever 41 to 44, and oils by an opening area corresponding to the operation amount of the operation lever 41 to 44. Move the spool so that the path opens.

  The pump control valve 5 is operated by a control current pc-epc output from the controller 6 and changes the pump control valve 5 via a servo piston.

The pump control valve 5 prevents the product of the discharge pressure PRp (kg / cm ² ) of the hydraulic pump 3 and the capacity q (cc / rev) of the hydraulic pump 3 from exceeding the pump absorption torque Tpcom corresponding to the control current pc-epc. In addition, the tilt angle of the swash plate of the hydraulic pump 3 is controlled. This control is called PC control.

  The generator motor 11 is provided with a rotation sensor 14 that detects the current actual rotational speed GEN_spd (rpm) of the generator motor 11, that is, the actual rotational speed of the engine 2. A signal indicating the actual rotation speed GEN_spd detected by the rotation sensor 14 is input to the controller 6.

  In addition, the livestock battery 12 is provided with a voltage sensor 15 that detects the voltage BATT_volt of the livestock battery 12. A signal indicating the voltage BATT_volt detected by the voltage sensor 15 is input to the controller 6.

  In addition, the controller 6 outputs the generator motor command value GEN_com to the inverter 13 to cause the generator motor 11 to perform a power generation operation or an electric operation. When a command value GEN_com for operating the generator motor 11 as a generator is output from the controller 6 to the inverter 13, a part of the output torque generated by the engine 2 is generated via the engine output shaft. Is generated by absorbing the torque of the engine 2. The AC power generated by the generator motor 11 is converted into DC power by the inverter 13 and is stored (charged) in the battery 12 via the DC power line.

  Further, when a command value GEN_com for operating the generator motor 11 as an electric motor is output from the controller 6 to the inverter 13, the inverter 13 controls the generator motor 11 to operate as an electric motor. That is, electric power is output (discharged) from the battery 12 and the DC power stored in the battery 12 is converted into AC power by the inverter 13 and supplied to the generator motor 11 to rotate the drive shaft of the generator motor 11. As a result, torque is generated in the generator motor 11, and this torque is transmitted to the engine output shaft via the drive shaft of the generator motor 11 and added to the output torque of the engine 2 (the output of the engine 2 is assisted). ). This added output torque is absorbed by the hydraulic pump 3.

  The power generation amount (absorption torque amount) and the motor drive amount (assist amount; generated torque amount) of the generator motor 11 change according to the contents of the generator motor command value GEN_com.

  The controller 6 outputs a rotation command value to the engine controller 4 including the governor, and increases or decreases the fuel injection amount so as to obtain the target rotation speed according to the current load of the hydraulic pump 3. The rotation speed n and torque T are adjusted.

  Next, control processing by the controller 6 will be described. FIG. 2 is a diagram showing a control flow by the controller 6. FIG. 3 is a diagram showing a processing flow of the target flow rate calculation unit shown in FIG. FIG. 4 is a flowchart showing processing of the engine target rotational speed addition value calculation unit shown in FIG. Further, FIG. 6 is a diagram showing a processing flow of the pump output restriction calculation unit shown in FIG.

  First, as shown in FIGS. 2 and 3, in the target flow rate calculation unit 50, the boom lever signal Lbo, the arm lever signal Lar, the bucket lever signal Lbk, the turning lever signal Lsw, the right traveling pilot pressure PRcr, and the left traveling pilot pressure PRcl. Is input, based on these values, the target flow rate Qbo of the corresponding boom cylinder 31, the target flow rate Qar of the arm cylinder 32, the target flow rate Qbk of the bucket cylinder 33, the target flow rate Qsw of the swing motor 34, and the travel for right travel The target flow rate Qcr of the motor 35 and the target flow rate Qcl for each left travel traveling motor 36 are calculated.

  In the storage device in the controller 6, functional relationships 51a, 52a, 53a, 54a, 55a, and 56a between the operation amount and the target flow rate are stored in a data table format for each hydraulic actuator.

  The boom target flow rate calculation unit 51 calculates the boom target flow rate Qbo corresponding to the current operation amount in the boom raising direction or the operation amount Lbo in the boom lowering direction according to the functional relationship 51a.

  The arm target flow rate calculation unit 52 calculates the arm target flow rate Qa corresponding to the current operation amount in the arm excavation direction or the operation amount La in the arm dump direction according to the functional relationship 52a.

  The bucket target flow rate calculation unit 53 calculates a bucket target flow rate Qbk corresponding to the current operation amount in the bucket excavation direction or the operation amount Lbk in the bucket dump direction according to the functional relationship 53a.

  The turning target flow rate calculation unit 54 calculates a turning target flow rate Qsw corresponding to the current operation amount in the right turn direction or the operation amount Lsw in the left turn direction according to the functional relationship 54a.

  The right travel target flow rate calculation unit 55 calculates the right travel target flow rate Qcr corresponding to the current right travel pilot pressure PRcr according to the functional relationship 55a.

  The left travel target flow rate calculation unit 56 calculates the left travel target flow rate Qcl corresponding to the current left travel pilot pressure PRcl according to the functional relationship 56a.

  For calculation processing, the boom raising operation amount, arm excavation operation amount, bucket excavation operation amount, and right turn operation amount are handled as plus operation amounts, and the boom lowering operation amount, arm dump operation amount, bucket dump operation amount. The left turn operation amount is treated as a minus sign operation amount.

  The pump target discharge flow rate calculation unit 60 uses the sum of the hydraulic actuator target flow rates Qbo, Qar, Qbk, Qsw, Qcr, Qcl calculated by the hydraulic actuator target flow rate calculation unit 50 as the pump target discharge flow rate Qsum as follows. Execute the requested process.

Qsum = Qbo + Qar + Qbk + Qsw + Qcr + Qcl (2)
Here, the sum of the target flow rates of the hydraulic actuators is used as the pump target discharge flow rate. The maximum target flow rate among the hydraulic actuator target flow rates Qbo, Qar, Qbk, Qsw, Qcr, Qcl is set as the target of the hydraulic pump 3. The discharge flow rate may be used.

  The first engine target speed calculator 61 calculates a first engine target speed ncom1 corresponding to the pump target discharge flow rate Qsum calculated and output by the target flow rate calculator 50. Here, in the storage device of the controller 6, a functional relationship 61a in which the first engine target rotational speed ncom1 increases as the pump target discharge flow rate Qsum increases is stored in a data table format. As shown below, the first engine target speed ncom1 is the minimum engine that can discharge the pump target discharge flow rate Qsum when the hydraulic pump 3 is operated at the maximum capacity qmax, with the conversion constant α. It is given as the number of revolutions.

ncom1 = Qsum / qmax · α (3)
In the first engine speed calculation unit 61, the first engine target speed ncom1 corresponding to the current pump target discharge flow rate Qsum is calculated according to the functional relationship 61a, that is, the above equation (3).

  The determination unit 62 of the controller 6 determines whether or not the current pump target discharge flow rate Qsum is larger than a predetermined flow rate Qmin. Here, the predetermined flow rate serving as the threshold is set to a flow rate for determining whether or not each of the operation levers 41 to 44 has been operated from the neutral position.

  In the third engine target speed setting unit 68 in the controller 6, as a result of the determination by the determination unit 62, if the current pump target discharge flow rate Qsum is equal to or lower than the predetermined flow rate Qmin, that is, the determination result is NO, 3 is set to a rotational speed nJ (for example, 1000 rpm) near the low idle rotational speed nL of the engine 2. On the other hand, when the current pump target discharge flow rate Qsum is larger than the predetermined flow rate Qmin, that is, when the determination result is YES, the third engine target rotational speed ncom3 is larger than the low idle rotational speed nL of the engine 2. Is set to a large rotational speed nM (for example, 1400 rpm).

  On the other hand, the engine controller 4 to the controller 6 are input with the current engine speed Ne of the engine 2 and the engine torque Te of the engine 2 estimated from the fuel injection amount. The filter 101 in the controller 6 is a filter having a time constant of 0.5 (sec), and outputs an engine torque Te_f obtained by filtering the value of the input engine torque Te. The engine output calculation unit 102 in the controller 6 multiplies the engine speed Ne input from the engine controller 4 by the engine torque Te_f output from the filter 101, and further multiplies the conversion constant Const by the engine output (horsepower) Pe. Is calculated.

  A target engine output calculation unit 103 in the controller 6 calculates a target engine output (horsepower) Pe_aim for a second engine target rotation speed ncom2 to which an engine target rotation speed addition value ncom_add described later is added based on the functional relationship 103a. To do. Note that the initial value of the second engine target speed ncom2 is the first engine target speed ncom1. Here, the function relationship 103a is stored in the storage device in the controller 6, and the target engine output calculation unit 103 outputs the target engine output Pe_aim using the function relationship 103a.

  Here, the functional relationship 103a is obtained from a target horsepower line obtained by multiplying the target torque line L1 shown in FIG. 7 which is the same as the target engine operation line L0 shown in FIG. , Lowered load sensing boundary.

  The engine target rotational speed addition value calculation unit 104 in the controller 6 outputs the engine target rotational speed addition value ncom_add according to the flowchart shown in FIG. In FIG. 4, the engine target rotational speed addition value calculation unit 104 first sets ncom_add “0” as an initial value (step S101). Thereafter, the engine output Pe is acquired from the engine output calculation unit 102, and the target engine output Pe_aim is acquired from the target engine output calculation unit 103 (step S102). Here, the target engine output calculation unit 103 outputs the target engine output Pe_aim using the first engine target speed ncom1 as an initial value, and in subsequent calculations, the second engine target speed ncom2 is sequentially used. The target engine output Pe_aim is output.

  Further, the engine target rotational speed addition value calculation unit 104 calculates a value Iadd obtained by multiplying the value obtained by dividing the target engine output Pe_aim from the engine output Pe by the conversion coefficient Ie (step S103). This value Iadd is a value converted into the engine speed.

  Thereafter, the engine target rotational speed addition value calculation unit 104 is in a state in which the value of the pump discharge flow rate target value Qsum output from the target flow rate calculation unit 50 is changing in the increasing direction or the value is fixed after the increase. Whether or not (step S104). If the value of the pump discharge flow rate target value Qsum changes in the increasing direction or is not fixed after the increase (No in step S104), a process of adding the value Iadd to the engine target rotational speed addition value ncom_add is performed ( Step S106).

  On the other hand, when the value of the pump discharge flow rate target value Qsum changes in the increasing direction or is fixed after being increased (step S104, Yes), it is further determined whether or not the value Iadd is negative. (Step S105). When the value Iadd is not negative (No at Step S105), the process proceeds to Step S106, and processing for adding the value Iadd to the engine target rotational speed addition value ncom_add is performed. On the other hand, if the value Iadd is negative (step S105, Yes), the process proceeds to step S107 without performing the addition process of the value Iadd.

  That is, in the processing of steps S104 to S106, the pump discharge flow rate target value Qsum output by the target flow rate calculation unit 50 is changing in the increasing direction, or the value is fixed after the increase. If the value Iadd is negative, the process of adding the value Iadd to the engine target rotational speed addition value ncom_add is not performed. Specifically, as shown in FIG. 5, when the increase ΔQsum of the pump discharge flow rate target value Qsum is 0 or more, even if the value Iadd becomes negative, the engine target rotation speed addition value ncom_add is changed to the value Iadd. The process of maintaining the current second engine target speed ncom2 is performed without performing the process of reducing the absolute value. If the pump discharge flow rate target value Qsum is 0 or more, even if the value Iadd becomes negative, control is performed so as not to decrease the target engine speed until the operator intends to reduce power by operating the lever. This is to stabilize the system.

  Thereafter, it is determined whether or not the engine target rotational speed addition value ncom_add is positive (step S107). If the engine target rotational speed addition value ncom_add is positive (step S107, Yes), it is further determined whether or not all lever inputs (lever potentiometer signals) are in the neutral state or in the vicinity thereof (step S108). If all lever inputs are not in the neutral state or the vicinity thereof (step S108, No), it is further determined whether or not an assist flag assist_flag described later is true (step S109).

  If the engine target rotational speed addition value ncom_add is positive (Yes at Step S107), all lever inputs are not in the neutral state or its vicinity (No at Step S108), and the assist flag assist_flag is not True (Step S109). , No), a process of adding the engine target rotational speed addition value ncom_add to the first engine target rotational speed ncom1 is performed (step S110), and the second engine target rotational speed ncom2 (corresponding to the corrected engine target rotational speed). Is generated, the process proceeds to step S102, and the above-described processing is repeated.

  On the other hand, when the engine target rotational speed addition value ncom_add is not positive (step S107, No), when all lever inputs are in the neutral state or in the vicinity thereof (step S108, Yes), or when the assist flag assist_flag is True (step) In S109, Yes), without adding the engine target rotational speed addition value ncom_add to the first engine target rotational speed ncom1, the current first engine target rotational speed ncom1 is directly used as the second engine target rotational speed. Is output as a number (corresponding to the corrected engine target speed), the process proceeds to step S102, and the above-described processing is repeated.

  This is because if the engine target rotational speed addition value ncom_add is not positive, it means that the load sensing boundary line is not approached and the load is not large, and it is not necessary to increase the engine rotational speed. In addition, when all lever inputs are in the neutral state or in the vicinity thereof, the operator's intention is given priority. Further, when the assist flag assist_flag is True, it is assisted by the electric motor without increasing the engine speed.

  The engine target rotational speed addition value ncom_add output in this way is added to the first engine target rotational speed ncom1 by the adding unit 105, and is output as the second engine target rotational speed ncom2. The second engine target speed ncom2 is output to the target engine output calculation unit 103 via the branching unit 106.

  The maximum value selection unit 64 in the controller 6 selects the higher engine target speed ncom23, which is the higher one of the second engine target speed ncom2 and the third engine target speed ncom3.

  On the other hand, the pump output restriction calculation unit 70 performs processing according to the flow shown in FIG. In the following, the determination result TRUE is abbreviated as T, and the determination result FALSE is abbreviated as F.

  It is determined that the work pattern of the plurality of hydraulic actuators 21 to 26 is the operation pattern (1) “traveling operation”, and the output limit value Pplimit of the hydraulic pump 3 is adapted to the work pattern “traveling operation”. Is set to Pplimit1.

  The pump output limit calculation unit 70 calculates the output (horsepower) limit value Pplimit of the hydraulic pump 3 according to the work pattern of the plurality of hydraulic actuators 21 to 26.

  As output limit values of the hydraulic pump 3, Pplimit1, Pplimit3, Pplimit4, Pplimit5, and Pplimit6 are calculated in advance. The size of the output limit value of the hydraulic pump 3 is set so as to decrease sequentially in the order of Pplimit1, Pplimit2, Pplimit3, Pplimit4, Pplimit5, and Pplimit6, as shown on the torque diagram shown in FIG. And

  That is, when the right traveling pilot pressure Prcr is larger than the predetermined pressure Kc or when the left traveling pilot pressure Prcl is larger than the predetermined pressure Kc (determination T in step 71), the plurality of hydraulic actuators 21 to 26 are operated. It is determined that the work pattern is the work pattern (1) “traveling operation”, and the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit1 so as to match the work pattern “traveling operation”.

  In the same manner, the following determinations are made in steps 72 to 79. That is, in step 72, it is determined whether or not the right turn operation amount Lsw is larger than the predetermined operation amount Ksw and the left turn operation amount Lsw is smaller than the predetermined operation amount −Ksw.

  In step 73, it is determined whether or not the boom lowering operation amount Lbo is smaller than a predetermined operation amount -Kbo.

  In step 74, whether or not the boom raising operation amount Lbo is larger than a predetermined operation amount Kbo, whether the arm excavation operation amount La is larger than the predetermined operation amount Ka, or whether the arm dump operation amount La is Whether or not the predetermined operation amount −Ka is smaller than that, or whether or not the bucket excavation operation amount Lbk is larger than the predetermined operation amount Kbk, or the bucket dump operation amount Lbk is smaller than the predetermined operation amount −Kbk. It is determined whether or not.

  In step 75, it is determined whether or not the arm excavation operation amount La is larger than a predetermined operation amount Ka.

  In step 76, it is determined whether or not the bucket excavation operation amount Lbk is larger than a predetermined operation amount Kbk.

  In step 77, it is determined whether or not the discharge pressure PRp of the hydraulic pump 3 is smaller than a predetermined pressure Kp1.

  In step 78, it is determined whether or not the arm dump operation amount La is smaller than a predetermined operation amount -Ka.

  In step 79, it is determined whether or not the bucket dump operation amount Lbk is smaller than a predetermined operation amount -Kbk.

  In step 80, it is determined whether or not the discharge pressure PRp of the hydraulic pump 3 is greater than a predetermined pressure Kp2.

  In step 81, it is determined whether or not the discharge pressure PRp of the hydraulic pump 3 is greater than a predetermined pressure Kp3.

  When the determination at step 71 is F, the determination at step 72 is T, and the determination at step 73 is T, the operation pattern of the hydraulic actuators 21 to 26 is an operation pattern of “turning operation and boom lowering operation” ( 2), the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit6 so as to conform to the work pattern.

  When the judgment of step 71 is F, the judgment of step 72 is T, the judgment of step 73 is F, and the judgment of step 74 is T, the work pattern of the hydraulic actuators 21 to 26 is “turn operation and boom”. It is determined that the work pattern (3) is “work machine operation other than lowering”, and the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit1 so as to match the work pattern.

  When the judgment at step 71 is F, the judgment at step 72 is T, the judgment at step 73 is F, and the judgment at step 74 is F, the work pattern of the plurality of hydraulic actuators 21 to 26 is “single operation of turning operation”. It is determined that the operation pattern is “operation” (4), and the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit6 so as to match the operation pattern.

  When the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is T, the judgment of step 76 is T, and the judgment of step 77 is T, the work patterns of the plurality of hydraulic actuators 21 to 26 Is determined to be a work pattern (5) of “when the load is small (for example, work for holding earth and sand) by arm excavation operation and bucket excavation operation”, and the output limit of the hydraulic pump 3 is limited so as to conform to the work pattern. The value Pplimit is set to Pplimit2.

  When the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is T, the judgment of step 76 is T, and the judgment of step 77 is F, the work patterns of the plurality of hydraulic actuators 21 to 26 Is determined to be the work pattern (6) “when the load is large in the arm excavation operation and the bucket excavation operation (for example, excavation work by simultaneous operation of the arm and bucket)”, and the hydraulic pressure is adjusted so as to conform to the work pattern. The output limit value Pplimit of the pump 3 is set to Pplimit1.

  When the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is T, and the judgment of step 76 is F, the work pattern of the plurality of hydraulic actuators 21 to 26 is “arm excavation operation”. The output limit value Pplimit of the hydraulic pump 3 is set to Pplimit1 so as to match the work pattern (7).

  If the determination in step 71 is F, the determination in step 72 is F, the determination in step 75 is F, the determination in step 78 is T, the determination in step 79 is T, and the determination in step 80 is T, a plurality of hydraulic pressures The work pattern of the actuators 21 to 26 is determined to be a work pattern (8) of “when the load is large in the arm earthing operation and the bucket earthing operation (for example, earth and sand pushing work by simultaneous earth and bucket earthing operation)”. Then, the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit3 so as to conform to the work pattern.

  If the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is F, the judgment of step 78 is T, the judgment of step 79 is T, and the judgment of step 80 is F, a plurality of hydraulic pressures The work pattern of the actuators 21 to 26 is determined to be a work pattern (9) of “when the load is small in the arm earthing operation and the bucket earthing operation (for example, the work for returning the arm and the bucket simultaneously in the air)” The output limit value Pplimit of the hydraulic pump 3 is set to Pplimit5 so as to conform to the work pattern.

  If the determination in step 71 is F, the determination in step 72 is F, the determination in step 75 is F, the determination in step 78 is T, the determination in step 79 is F and the determination in step 81 is T, a plurality of hydraulic actuators The work patterns 21 to 26 are determined to be work patterns (10) of “when the load is large due to the single arm earth removal operation (for example, earth and sand pushing work by the arm earth removal work)”, and are adapted to the work pattern. In addition, the output limit value Pplimit of the hydraulic pump 3 is set to Pplimit3.

  If the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is F, the judgment of step 78 is T, the judgment F of step 79 is F and the judgment of step 81 is F, a plurality of hydraulic actuators The work patterns 21 to 26 are determined to be the work pattern (11) “when the load is small (for example, work to return the arm in the air) by the arm single earth removal operation”, and so as to conform to the work pattern. The output limit value Pplimit of the hydraulic pump 3 is set to Pplimit5.

  When the judgment of step 71 is F, the judgment of step 72 is F, the judgment of step 75 is F, and the judgment of step 78 is F, the work pattern of the plurality of hydraulic actuators 21 to 26 is “other work”. The output limit value Pplimit of the hydraulic pump 3 is set to Pplimit1 so as to match the work pattern (12).

  On the other hand, the relief pump output limit value calculation unit 500 receives the discharge pressure PRp of the hydraulic pump 3 and calculates the output limit value Pplimit of the hydraulic pump 3 with respect to the discharge pressure PRp of the hydraulic pump 3. The output limit value Pplimit is calculated based on the functional relationship 500a of the output limit value Pplimit with respect to the discharge pressure PRp so that sudden pump output fluctuation does not occur during relief. This functional relationship is stored in the storage device of the controller 6.

  Thereafter, the minimum selection unit 501 outputs an output limit value Pplimit that is smaller of either the output limit value Pplimit output from the pump output limit value calculation unit 70 or the output limit value Pplimit output from the relief pump output limit value calculation unit 500. Is selected and output.

  Next, the fourth engine target speed calculator 63 in the controller 6 calculates the fourth engine target speed ncom4 corresponding to the output limit value Pplimit selected by the minimum selector 501.

  In the storage device in the controller 6, a functional relationship 63a in which the third engine target rotational speed ncom3 increases as the output limit value Pplimit of the hydraulic pump 3 increases is stored in a data table format.

  In the fourth engine speed calculation unit 63, the current working pattern of the plurality of hydraulic actuators 21 to 26, that is, the fourth engine target speed ncom4 corresponding to the output limit value Pplimit of the hydraulic pump 3 is determined according to the function relation 63a. Calculated.

  The minimum value selection unit 65 selects the engine target speed ncom which is lower of the engine target speed ncom23 selected by the maximum value selection part 64 and the fourth engine target speed ncom4.

  The controller 6 outputs a rotation command value for setting the engine speed n to the target speed ncom to the engine controller 4, and the controller 4 outputs the engine target speed ncom on the target torque line L1 shown in FIG. The fuel injection amount is increased or decreased so that

  Here, as shown in FIG. 7, when the engine 2 and the hydraulic pump 3 are controlled according to the target torque line L1 in which the pump absorption torque Tpcom decreases as the engine speed n decreases, the fuel efficiency, engine efficiency, and pump efficiency are improved. However, there is a problem that the responsiveness of the engine 2 is poor, although effects such as reduction of noise and prevention of engine stall are obtained. For example, even if the operation lever 41 is tilted from the neutral position to start excavation work and the engine 2 is raised from a low speed, the load of the hydraulic pump 3 suddenly increases at the initial stage (transient state) when the lever is started to fall. Therefore, the engine output has no margin for the power of the pump absorption horsepower, and the power for accelerating the engine 2 is insufficient. For this reason, the engine 2 may not be raised to the target rotational speed or may be raised only very slowly.

  In this regard, in this embodiment, the second engine target speed ncom2 is set by adding the engine target speed addition value ncom_add to the first engine target speed ncom1 that matches the current pump target discharge flow rate Qsum. On the other hand, when it is determined that the current pump target discharge flow rate Qsum is larger than a predetermined flow rate (for example, 10 (L / min)), the rotation speed nM (for example, 1400 rpm) larger than the engine low idle rotation speed nL. ) Is set as the third engine target speed ncom3. If the third engine target speed ncom3 is equal to or higher than the second engine target speed ncom2, the engine speed is controlled so that the third engine target speed ncom3 is obtained.

  For this reason, for example, when the operation lever 41 is tilted from the neutral position in order to start excavation work, the engine speed increases in advance and the engine torque increases before the load of the hydraulic pump 3 suddenly increases. There is a margin in power for accelerating 2. For this reason, the engine 2 can be rapidly raised from the low speed range to the target speed, and the response of the engine 2 is improved.

  Further, in this embodiment, the engine target revolution speed addition value calculation unit 104 adds the engine target revolution speed addition value ncom_add to the first engine target revolution speed ncom1. When the current engine output Pe is larger than the target engine output Pe_aim corresponding to the second engine target speed ncom2, the engine target speed addition value calculation unit 104 determines the engine target speed according to the difference. The engine speed is increased by adding the number addition value ncom_add to the first engine target speed ncom1.

  With reference to FIG. 7 and FIG. 8, the engine speed increasing process by the engine target speed addition value calculation unit 104 will be described. For convenience of explanation, description will be made using a torque diagram instead of horsepower. FIG. 7 is a torque diagram showing changes in engine torque with respect to engine speed. This torque diagram is the same as the torque diagram shown in FIG. 22, and the target engine operation line L0 corresponds to the target torque line L1. The load sensing torque boundary line L2 is a line that is lower than the target torque line L1 by a predetermined torque. A line obtained by multiplying the load sensing torque boundary line L1 by the engine speed becomes a load sensing boundary line. Become. The load sensing torque boundary line L2 indicates that a region surrounded by the target torque line L1 and the load sensing torque line L2 is a load sensing region E and is a boundary of the load sensing region E. That is, the load sensing area E is defined as an area approaching the target torque line L1 to some extent, and when approaching the load sensing area E, it is considered that the construction machine is requesting output and the engine speed is increased. I try to speed up.

  FIG. 8 is a diagram showing temporal changes in engine speed and torque when there is a lever input. 7 and 8, the state “1” is an idle state, and the engine speed is GOV_1. When lever input starts at time T1, the engine speed increases in accordance with the lever operation and becomes the state “2”. At time T2 when the lever is fixed, the engine speed becomes GOV_2. In this state “2”, the torque gradually increases as time passes, and at the time T3 at the end of the state “2”, the engine speed and the torque exceed the load sensing torque boundary line L2. That is, the engine speed is equal to or less than the engine speed of the load sensing torque boundary line L2, and the torque is equal to or greater than the torque of the load sensing torque boundary line L2. The state of entering the load sensing region E beyond the load sensing torque boundary line L2 is the state “3”, and in this state “3”, the engine target revolution speed addition value calculation unit 104 performs the engine target revolution speed operation. The added value ncom_add is added to the first engine target speed ncom1 to increase the speed. As a result, in the second half of the state “3”, the engine speed is increased and the torque is also decreased. At the time T4 at the end of the state “3”, the engine speed and the torque are set at the load sensing torque boundary line L2. The engine speed increase process by the engine target rotation speed addition value calculation unit 104 is not performed.

  Thus, in this embodiment, when the engine speed and the torque state enter the load sensing region E, the engine speed is increased assuming that an increase in output is required. In particular, since the engine speed is automatically increased to increase the output without performing the lever operation again for the load applied after the lever operation, the operability for the operator can be improved. That is, the output is automatically increased when a large load is applied.

  In this embodiment, the second engine target speed ncom2 obtained by adding the engine target speed addition value ncom_add to the first engine target speed ncom1 that matches the current pump target discharge flow rate Qsum is set. Thus, the output limit value Pplimit of the hydraulic pump 3 set according to the work pattern of the plurality of hydraulic actuators 21 to 26 and the output limit value for the discharge pressure of the hydraulic pump 3 in consideration of the high load pressure state at the time of relief The minimum output limit value Pplimit of Pplimit is selected, and a fourth engine target speed ncom4 corresponding to the selected output limit value Pplimit is set. If the fourth engine target speed ncom4 is equal to or lower than the engine target speed ncom23, the engine speed is controlled so that the fourth engine target speed ncom4 is obtained.

  That is, in this embodiment, when the relief state is established by the relief pump output limit value calculation unit 500 and the fourth engine target rotation number calculation unit 63, the pump absorption torque is not limited but the engine is not limited. Control to reduce the number of revolutions. In this case, it is possible to obtain the pump output equivalent to the case where the pump absorption torque is limited, and the engine speed is lowered, so that the pump efficiency is not lowered and the engine efficiency is improved, thereby achieving energy saving. And noise can be improved.

  In this embodiment, the fourth engine target speed is determined after selecting the minimum value of the output limit values of the pump output limit calculation unit 70 and the relief pump output limit value calculation unit 500. However, the present invention is not limited to this, and in addition to the processing route of the pump output limit value calculation unit 70 → the minimum value selection unit 501 → the fourth engine target speed calculation unit 63, the relief pump output limit value calculation unit 500 And the fourth engine target speed calculating unit 63 are combined, and the fifth engine target speed corresponding to the fourth engine target speed with respect to the discharge pressure is directly calculated and output to the minimum value selecting unit 65. You may make it do.

  Here, with reference to FIG. 10 and FIG. 11, the assist control process by the controller 6 of the construction machine 1 will be described.

  The engine target speed ncom selected by the minimum value selection unit 65 shown in FIG. 2 is input to the assist control process shown in FIG.

  In the following, calculation processing is performed after converting the engine speed and the engine target speed to the generator motor speed and the generator motor target speed, respectively. However, in the following explanation, the generator motor speed and power generation It is also possible to perform the same calculation process by replacing the motor target rotational speed with the engine rotational speed and the engine target rotational speed, respectively.

  In the generator motor target rotational speed calculation unit 96, the target rotational speed Ngen_com of the generator motor 11 corresponding to the current engine target rotational speed ncom is calculated by the following equation.

Ngen_com = ncom × K2 (4)
Here, K2 is a reduction ratio of the PTO shaft 10.

  In the assist presence / absence determination unit 90, the target rotation speed Ngen_com of the generator motor 11, the current actual rotation speed GEN_spd of the generator motor 11 detected by the rotation sensor 14, and the current voltage BATT_volt of the livestock generator 12 detected by the voltage sensor 15. Based on the above, it is determined whether or not the generator motor 11 assists the engine 2 (assist presence / absence).

  As shown in FIG. 11, in the assist presence / absence determination unit 90, first, the deviation calculation unit 91 calculates a deviation Δgen_spd between the generator motor target rotation speed Ngen_com and the generator motor actual rotation speed GEN_spd.

  Next, in the first determination unit 92, when the deviation Δgen_spd between the generator motor target rotation speed Ngen_com and the generator motor actual rotation speed GEN_spd is equal to or greater than the first threshold value ΔGC1, the generator motor 11 is electrically operated. When the assist flag assist_flag is set to T and the deviation Δgen_spd between the generator motor target speed Ngen_com and the generator motor actual speed GEN_spd is equal to or smaller than the second threshold value ΔGC2 smaller than the first threshold value ΔGC1 Then, it is determined that the generator motor 11 is not electrically operated (however, if necessary, the power is generated and the electric power is stored in the battery 12), and the assist flag is set to F.

  Further, when the deviation Δgen_spd between the generator motor target rotation speed Ngen_com and the generator motor actual rotation speed GEN_spd is equal to or less than the third threshold value ΔGC3, it is determined that the generator motor 11 generates power, and the assist flag assist_flag is set to T. When the deviation Δgen_spd between the generator motor target rotation speed Ngen_com and the generator motor actual rotation speed GEN_spd is equal to or larger than a fourth threshold value ΔGC4 that is larger than the third threshold value ΔGC3, the generator motor 11 is not generated. (However, it is determined that the electric power is generated as necessary and the electric power is stored in the battery 12), and the assist flag is set to F.

  As described above, when the rotational speed deviation Δgen_spd is a plus sign and becomes larger than a certain level, the generator motor 11 is electrically operated to assist the engine 2 because the current engine rotational speed and the target rotational speed are separated. This is to quickly increase the engine speed toward the target engine speed.

  Here, for example, when the load pressure of the hydraulic pump is suddenly switched from a high state to a low state, until the actual engine speed increases to a value set in advance with respect to the target engine speed, the generator motor The engine rotational speed is controlled so as to coincide with the target rotational speed by using the engine torque assist action. That is, when the load pressure of the hydraulic pump is suddenly switched from a high state to a low state, the fourth engine target rotational speed increases and the deviation from the actual rotational speed increases. work.

  Note that, as described above, as the load pressure of the hydraulic pump decreases from a high state to a low state, the fourth engine target speed increases, so that the actual engine speed becomes higher than the engine target speed. If it is smaller than the preset value, the engine speed assist action of the generator motor will be used to match the target speed until the actual speed rises to a value smaller than the preset value than the target engine speed. Thus, the engine speed is controlled.

  Further, when the rotational speed deviation Δgen_spd is larger than a certain value with a minus sign, the generator motor 11 generates power and reversely assists the engine 2. The reason is that when the engine speed is decelerated, the engine speed is quickly increased by generating power. This is because the energy of the engine 2 is regenerated.

  Further, by providing hysteresis between the first threshold value ΔGC1 and the second threshold value ΔGC2, and by providing hysteresis between the third threshold value ΔGC3 and the fourth threshold value ΔGC4, Control hunting is prevented.

  In the second determination unit 93, when the voltage BATT_volt of the battery 12 is within the predetermined range BC1 to BC4 (BC2 to BC3), the assist flag assist_flag is set to T, and when the voltage is outside the predetermined range, Set assist flag assist_flag to F.

  The first threshold value BC1, the second threshold value BC2, the third threshold value BC3, and the fourth threshold value BC4 are set to the voltage value BATT_volt. It is assumed that the first threshold value BC1, the second threshold value BC2, the third threshold value BC3, and the fourth threshold value BC4 increase in this order.

  When the voltage value BATT_volt of the battery 12 becomes equal to or lower than the third threshold value BC3, the assist flag assist_flag is set to T, and when the voltage value BATT_volt of the battery 12 becomes equal to or higher than the fourth threshold value BC4, the assist flag assist_flag is set to F. When the voltage value BATT_volt of the battery 12 becomes equal to or higher than the second threshold value BC2, the assist flag assist_flag is set to T, and when the voltage value BATT_volt of the battery 12 becomes equal to or lower than the first threshold value BC1, the assist flag assist_flag is set to F. .

  As described above, only when the voltage BATT_volt of the battery 12 is within the predetermined range BC1 to BC4 (BC2 to BC3), the assist is made when the voltage is low or high outside the predetermined range. This is to avoid adverse effects such as overcharge and complete discharge applied to the battery 12 by preventing the assist.

  Further, by providing a hysteresis between the first threshold value BC1 and the second threshold value BC2, and providing a hysteresis between the third threshold value BC3 and the fourth threshold value BC4, Control hunting is prevented.

  In the AND circuit 94, when the assist flag assist_flag obtained by the first determination unit 92 and the assist flag assist_flag obtained by the second determination unit 93 are both T, the content of the assist flag assist_flag is finally set to T Otherwise, the content of the assist flag assist_flag is finally set to F.

  The assist flag assist_flag output from the assist presence / absence determination unit 90 is output to the engine target rotation speed addition value calculation unit 104. When the assist flag assist_flag is True, the engine target rotation speed addition value calculation unit 104 An additional output of the rotational speed addition value ncom_add is not performed.

  The assist flag determination unit 95 determines whether or not the content of the assist flag assist_flag output from the assist presence determination unit 90 is T.

  In the generator motor command value switching unit 87, the content of the generator motor command value GEN_com to be given to the inverter 13 is set to the target rotational speed, depending on whether or not the determination result of the assist flag determination unit 95 is T (F). Switch to target torque.

  The generator motor 11 is controlled by rotation speed control or torque control via the inverter 13.

  Here, the rotation speed control is control for adjusting the rotation speed of the generator motor 11 so that the target rotation speed can be obtained by giving the target rotation speed as the generator motor command value GEN_com. The torque control is control for adjusting the torque of the generator motor 11 so that the target torque is obtained by giving the target torque as the generator motor command value GEN_com.

  In the modulation processing unit 97, the target rotational speed of the generator motor 11 is calculated and output. The generator motor torque calculation unit 68 calculates and outputs the target torque of the generator motor 11.

  That is, the modulation processing unit 97 outputs the rotation speed Ngen_com that has been subjected to the modulation process according to the characteristic 97 a with respect to the generator motor target rotation speed Ngen_com obtained by the generator motor target rotation speed calculation unit 96. Instead of outputting the generator motor target rotation speed Ngen_com inputted from the generator motor target rotation speed calculation unit 96 as it is, the rotation speed is gradually increased over time t and from the generator motor target rotation speed calculation unit 96. The input generator motor target rotational speed Ngen_com is reached.

  With reference to the torque diagrams shown in FIG. 12 to FIG. 15, effects when the modulation process is performed with respect to the case where the modulation process is not performed will be described.

  FIG. 12 is a diagram for explaining the movement of the governor when there is no modulation processing during engine acceleration, and FIG. 13 is a diagram for explaining the motion of the governor when there is modulation processing during engine acceleration. FIG. 14 is a diagram for explaining the movement of the governor when the modulation process is not performed when the engine is decelerated, and FIG. 15 is a diagram for explaining the movement of the governor when the modulation process is performed when the engine is decelerated. When a mechanical governor is used as the governor, there is a problem that the speed specified by the governor is delayed from the actual engine speed.

  Consider a case where the engine 2 is accelerated from the low rotation matching point P0 to the high rotation side when the load of the hydraulic pump 3 is large as shown in FIGS. 12 and 13, P2 corresponds to the engine torque, and the total torque P3 of the engine 2 and the generator motor 11 is obtained by adding the assist torque to the engine torque. P1 corresponds to the pump absorption torque, and the sum of the pump absorption torque and the acceleration torque corresponds to the total torque P3.

  As shown in FIG. 12, when there is no modulation processing, an assist torque corresponding to the deviation between the target engine speed and the actual engine speed is generated. When the deviation is large, the assist torque by the generator motor 11 increases corresponding to the large deviation. For this reason, the engine 2 accelerates faster than the movement of the governor, and the actual rotational speed becomes larger than the rotational speed specified by the governor. When the engine 2 accelerates quickly, the fuel injection amount is reduced by adjusting the governor, and the engine torque is reduced. For this reason, although the engine 2 is assisted by the generator motor 11, the engine 2 becomes friction, and the acceleration of the engine 2 does not increase. For this reason, while reducing the fuel injection amount and reducing the engine torque, the engine 2 is lost and the engine 2 is accelerated, resulting in energy loss and the result that the engine 2 is not sufficiently accelerated.

  On the other hand, as shown in FIG. 13, in the case where there is a modulation process, the modulation process is performed on the target engine speed, and the deviation between the target engine speed and the actual engine speed becomes small. A small assist torque is generated in the generator motor 11. For this reason, the movement of the governor follows the acceleration of the engine 2, and the rotational speed designated by the governor matches the actual rotational speed. For this reason, energy loss is reduced and the engine 2 is sufficiently accelerated.

  Next, a case where the engine 2 is decelerated will be described. As shown in FIGS. 14 and 15, consider a case where the engine 2 is decelerated from the high rotation matching point P 0 to the low rotation side when the load of the hydraulic pump 3 is large.

  14 and 15, P2 corresponds to the engine torque, and the total torque P3 of the engine 2 and the generator motor 11 is obtained by adding the regenerative torque to the engine torque. P1 corresponds to the pump absorption torque, and the sum of the pump absorption torque and the deceleration torque corresponds to the total torque P3.

  As shown in FIG. 14, when there is no modulation processing, regenerative torque is generated according to the deviation between the target engine speed and the actual engine speed. When the deviation is large, the regenerative torque by the generator motor 11 is increased corresponding to the large deviation. For this reason, the engine 2 decelerates faster than the movement of the governor, and the actual rotational speed becomes smaller than the rotational speed specified by the governor. When the engine 2 decelerates quickly, the fuel injection amount increases due to the adjustment of the governor, and the engine torque increases. Therefore, the engine 2 decelerates while generating power with the generator motor 11 while increasing the torque. As a result, while the engine 2 increases the torque and the generator motor 11 collects the increased engine energy, the engine 2 is decelerated, and wasteful power generation is performed and fuel is wasted. .

  On the other hand, as shown in FIG. 15, when the modulation process is performed, the modulation process is performed on the target engine speed, and the deviation between the target engine speed and the actual engine speed becomes small. A small regenerative torque is generated in the generator motor 11. For this reason, the movement of the governor follows the deceleration of the engine 2, and the rotational speed designated by the governor matches the actual rotational speed. For this reason, the torque of the engine 2 becomes negative, and the engine 2 decelerates while recovering the speed energy of the engine 2 by the generator motor 11. For this reason, the engine 2 can be decelerated efficiently without causing unnecessary energy consumption.

  In the generator motor torque calculation unit 68, the target torque Tgen_com corresponding to the voltage BATT_volt is calculated based on the current voltage BATT_volt of the livestock generator 12 detected by the voltage sensor 15.

  The storage device has a functional relationship 68a with hysteresis that the target torque Tgen_com decreases according to the increase 68b of the voltage BATT_volt of the battery 12 and increases according to the decrease 68c of the voltage BATT_volt of the battery 12. Stored in table format. This functional relationship 68a is set in order to maintain the voltage value of the battery 12 within a desired range by adjusting the power generation amount of the generator motor 11.

  In the generator motor torque calculation unit 68, the target torque Tgencom corresponding to the current voltage BATT_volt of the battery 12 is output according to the functional relationship 68a.

  When the assist flag determination unit 95 determines that the content of the assist flag assert_flag is T, the generator motor command value switching unit 87 is switched to the modulation processing unit 97 side, and the generator motor target output from the modulation processing unit 97 is output. The rotational speed Ngen_com is output to the inverter 13 as a generator motor command value GEN_com, the rotational speed of the generator motor 11 is controlled, and the generator motor 11 performs an electric action or a power generation action.

  When the assist flag determination unit 95 determines that the content of the assist flag assert_flag is F, the generator motor command value switching unit 87 is switched to the generator motor torque calculation unit 68 side, and the generator motor torque calculation unit 68 The output generator motor target torque Tgen_com is output to the inverter 13 as a generator motor command value GEN_com, the torque of the generator motor 11 is controlled, and the generator motor 11 generates power.

  The pump absorption torque command value switching unit 88 determines the content of the pump target absorption torque T to be given to the control current calculation unit 67 according to whether or not the determination result of the assist flag determination unit 95 is T (F). The first pump target absorption torque Tp_com1 is switched to the second pump target absorption torque Tp_com2.

  The first pump target absorption torque Tp_com1 is calculated by the first pump target absorption torque calculating unit 66.

  That is, the first pump target absorption torque Tpcom1 is given as a torque value on the first target torque line L1 in the torque diagram of FIG. The first target torque line L1 is set as a target torque line such that the target absorption torque Tp_com1 of the hydraulic pump 3 decreases as the engine target speed n decreases.

  The second pump target absorption torque Tpcom2 is calculated by the second pump target absorption torque calculation unit 85. That is, the second pump target absorption torque Tp_com2 is on the second target torque line L12 where the pump target absorption torque becomes larger in the low rotation region than the first target torque line L1 in the torque diagram of FIG. It is given as a torque value.

  The first pump target absorption torque calculator 66 calculates the first pump target absorption torque Tpcom1 of the hydraulic pump 3 corresponding to the engine target speed ncom.

  In the storage device, a functional relationship 66a in which the first target absorption torque Tp_com1 of the hydraulic pump 3 increases in accordance with an increase in the engine target speed n_com is stored in a data table format. This function 66a is a curve corresponding to the first target torque line L1 on the torque diagram shown in FIG.

  FIG. 16 shows a torque diagram of the engine 2. The horizontal axis represents the engine speed n (rpm; rev / min), and the vertical axis represents the torque T (N · m). The function 66a corresponds to the target torque line L1 on the torque diagram shown in FIG.

  In the first pump target absorption torque calculation unit 66, the first pump target absorption torque Tp_com1 corresponding to the current engine target speed n_com is calculated according to the functional relationship 66a.

  In the second pump target absorption torque calculation unit 85, the second pump target absorption torque Tp_com2 of the hydraulic pump 3 corresponding to the generator motor rotation speed GEN_spd (engine actual rotation speed) is calculated.

  In the storage device, a functional relationship 85a in which the second target absorption torque Tp_com2 of the hydraulic pump 3 changes according to the generator motor speed GEN_spd (actual engine speed) is stored in a data table format. This function 85a is a curve corresponding to the second target torque line L12 on the torque diagram shown in FIG. 16, and the pump target absorption torque is larger in the low rotation region than the first target torque line L1. It has the following characteristics. For example, the second target torque line L12 is a curve corresponding to an equal horsepower line, and the characteristic can be adopted so that the torque decreases as the engine speed increases.

  In the second pump target absorption torque calculating unit 85, the second pump target absorption torque Tp_com2 corresponding to the current generator motor rotation speed GEN_spd (engine actual rotation speed) is calculated according to the functional relationship 85a.

  When the assist flag determination unit 95 determines that the content of the assist flag assist_flag is T, the pump absorption torque command value switching unit 88 is switched to the second pump target absorption torque calculation unit 85 side, and the second pump The second pump target absorption torque Tp_com2 output from the target absorption torque calculation unit 85 is output to the subsequent filter processing unit 89 as the pump target absorption torque Tp_com.

  When the assist flag determination unit 95 determines that the content of the assist flag assist_flag is F, the pump absorption torque command value switching unit 88 is switched to the first pump target absorption torque calculation unit 66 side, and the first The first pump target absorption torque Tp_com1 output from the pump target absorption torque calculator 66 is output to the subsequent filter processing unit 89 as the pump target absorption torque Tp_com.

  As described above, the pump absorption torque command value switching unit 88 switches the selection of the target absorption torques Tp_com1 and Tp_com2 of the hydraulic pump 3, that is, the target torque lines L1 and L12 in FIG.

  In the filter processing unit 89, when the selection of the target torque lines L1 and L12 is switched, the pump target absorption torque (second pump target absorption) on the target torque line before switching (for example, the second target torque line L12) is switched. A filter process for gradually changing from the torque Tp_com2) to the pump target absorption torque (second pump target absorption torque Tp_com1) on the target torque line after switching (first target torque line L1) is performed.

  That is, when the selection of the target torque lines L1 and L12 is switched, the filter processing unit 89 outputs the target torque value Tp_com that has been subjected to the filter processing according to the characteristic 89a. When the selection of the target torque lines L1 and L12 is switched, switching is performed from the pump target absorption torque (second pump target absorption torque Tp_com2) on the target torque line (for example, the second target torque line L12) before switching. Instead of switching and outputting the pump target absorption torque (second pump target absorption torque Tp_com1) on the subsequent target torque line (first target torque line L1) as it is, before gradually switching over time t. Pump target absorption line (second target torque line L12) on the target torque line (first target torque line L1) after switching from the pump target absorption torque (second pump target absorption torque Tp_com2) Smoothly reach the absorption torque (second pump target absorption torque Tp_com1).

  Referring to FIG. 16, from the second pump target absorption torque Tp_com2 at the point G on the second target torque line L12, the first pump target absorption torque Tp_com1 at the point H on the first target torque line L1. It gradually changes over time.

As a result, it is possible to suppress a shock applied to the operator and the vehicle body due to a sudden change in torque, and to eliminate a sense of incongruity in the operational feeling.

  The filter process may be performed in both cases where the determination result of the assist flag determination unit 95 is switched from T to F and when the determination result is switched from F to T. Filter processing may be performed only when it is performed. In particular, when the determination result of the assist flag determination unit 95 is switched from T to F and switched from the second target torque line L12 to the first target torque line L1, if the filter process is not performed, the torque decreases rapidly. In many cases, the operator feels uncomfortable. For this reason, when the determination result is switched from T to F and switched from the second target torque line L12 to the first target torque line L1, it is desirable to perform a filtering process.

  The pump target absorption torque Tp_com output from the filter processing unit 89 is given to the control current calculation unit 67. In the control current calculator 67, a control current pc-epc corresponding to the pump target absorption torque Tp_com is calculated.

  In the storage device, a functional relationship 67a in which the control current pc-epc increases as the pump target absorption torque Tp_com increases is stored in a data table format.

  In the control current calculator 67, the control current pc-epc corresponding to the current pump target absorption torque Tp_com is calculated according to the functional relationship 67a.

  A control current pc-epc is output from the controller 6 to the pump control valve 5 to change the pump control valve 5 via the servo piston. The pump control valve 5 prevents the product of the discharge pressure PRp (kg / cm 2) of the hydraulic pump 3 and the capacity q (cc / rev) of the hydraulic pump 3 from exceeding the pump absorption torque Tp_com corresponding to the control current pc-epc. The tilt angle of the swash plate of the hydraulic pump 3 is PC-controlled.

  According to this embodiment, as shown in FIG. 16, the first target torque line L1 is set, in which the target absorption torque of the hydraulic pump 3 decreases as the engine target rotational speed decreases. In addition, a second target torque line L12 is set with respect to the first target torque line L1, which increases the pump target absorption torque in the low rotation range.

  Then, the engine speed is controlled so as to coincide with the engine target speed. For example, when it is determined that the load of the hydraulic pump 3 is small from the operation amount of each operation lever 41 to 44, the engine target rotation speed is set to a low rotation speed nD, and the hydraulic pump 3 is determined from the operation amount of each operation lever 41 to 44. When it is determined that the engine load is large, the engine target speed is set to a high speed nE.

  Then, it is determined whether or not the deviation between the target engine speed and the actual engine speed is equal to or greater than a predetermined threshold value, that is, whether or not the generator motor 11 should assist the engine 2.

  When the deviation between the engine target speed and the actual engine speed is not equal to or greater than a predetermined threshold value, the first target torque line L1 is selected, and the first target speed corresponding to the engine target speed is selected. The capacity of the hydraulic pump 3 is controlled so that the pump target absorption torque on the target torque line L1 is obtained.

  For this reason, when the engine target speed is set to the low speed nD, the governor sets the upper limit torque value at a point D that intersects the first target torque line L1 on the regulation line FeD corresponding to the engine target speed nD. The fuel injection amount is increased or decreased so that the engine 2 and the hydraulic pump absorption torque are balanced. Statically, matching is performed at a point D on the first target torque line L1.

  When the target engine speed is set to the high engine speed nE, the governor sets a point E that intersects the first target torque line L1 on the regulation line FeE corresponding to the engine target engine speed nE as the upper limit torque value. The fuel injection amount is increased or decreased so that the engine 2 and the hydraulic pump absorption torque are balanced. Statically, matching is performed at a point E on the first target torque line L1.

  Therefore, when the assist by the generator motor 11 is not performed, the engine 2 is controlled along the target torque line L1 as in the comparative example, so that the fuel efficiency is improved, the pump efficiency and the engine efficiency are improved, the noise is reduced, and the engine stall is increased. Effects such as prevention can be obtained.

  When the deviation between the target engine speed and the actual engine speed is equal to or greater than a predetermined threshold value, the generator motor 11 is electrically operated. As a result of the generator motor 11 being electrically operated, the torque indicated by the broken line in FIG. 16 is added to the engine torque.

  When the threshold value is equal to or greater than the threshold value, the second target torque line L12 is selected so that the pump target absorption torque on the second target torque line L12 corresponding to the engine speed can be obtained. The capacity of the hydraulic pump 3 is controlled.

  Here, for example, consider a case where the operation lever 41 or the like is tilted from the neutral position in order to start excavation work. In this case, it is necessary to increase the engine speed from a low rotation to a high load matching point E of high rotation.

  When the assist control is not performed, the engine 2 accelerates along the path LN1 in FIG. In the initial stage of starting the excavation work, it is necessary to operate the work implement or the like while increasing the engine rotation (at the time of transition). If there is no assist by the generator motor 2 and no shift to the second target torque line L12, the absorption torque of the hydraulic pump 3 becomes small at the initial stage when the engine speed is increased. For this reason, the start of movement of the work implement is delayed with respect to the movement of the operation lever, causing a reduction in work efficiency and giving the operator an uncomfortable feeling of operation.

  In this embodiment, since the assist by the generator motor 11 is added, the engine 2 is accelerated along the path LN2. In this case, since there is an assist by the generator motor 2, the absorption torque of the hydraulic pump 3 increases at an initial stage when the engine speed increases. For this reason, the work machine starts to move faster than the operation lever, so that a reduction in work efficiency can be suppressed, and an uncomfortable feeling of operation given to the operator can be reduced.

  In the case of the embodiment, the engine 2 accelerates along the path LN3 of FIG. According to the embodiment, the point E is reached from the low rotation speed via the point F on the second target torque line L12. That is, immediately after the operation lever 41 is tilted, the hydraulic pump absorption torque immediately reaches a point F where the torque becomes high, so that the working machine starts to move faster than the operation lever moves. For this reason, the work implement can be instantaneously and powerfully moved without lagging the movement of the operation lever while accelerating the engine 2. This improves work efficiency and does not give the operator a sense of incongruity. If there is no assistance from the generator motor 11 (without the hatched portion shown in FIG. 18) and the transition to the second target torque line L12 is attempted, the engine 2 may be overloaded. In this embodiment, the transition to the second target torque line L12 is guaranteed on the premise of the assist by the generator motor 11.

  In particular, since the engine speed is decreased in the high load pressure state at the time of relief, the deviation between the engine target speed and the actual engine speed becomes large, and immediately after shifting to the relief release state, the engine target speed is However, the actual engine speed remains low, and it takes time until the actual engine speed shifts to the engine target speed. In this embodiment, since the assist control is performed when this large deviation occurs, the actual engine speed can be quickly returned to the engine target speed, and the reduction in the work amount is almost felt. Work can be done.

  In this embodiment, the work implement or the like can be operated with high responsiveness as intended by the operator while improving the engine efficiency, the pump efficiency, and the like.

  This embodiment can also be applied to a construction machine that does not have an assisting function and does not have a generator / motor and a capacitor, like the construction machine shown in FIG. FIG. 19 is a block diagram showing a schematic configuration of a construction machine according to a modification of the embodiment of the present invention. FIG. 20 is a diagram showing a control flow of the controller shown in FIG. This construction machine does not have a generator / motor and a capacitor, and performs the same control flow as the controller shown in FIG.

  In this construction machine, the pump absorption torque calculation unit 66 shown in FIG. 20 calculates the target absorption torque Tp_com of the hydraulic pump 3 corresponding to the engine target speed n_com.

  In a storage device in the controller 6, a functional relationship 66a in which the target absorption torque Tp_com of the hydraulic pump 3 increases as the engine target speed n_com increases is stored in a data table format. This function 66a is a curve corresponding to the target torque line L1 on the torque diagram shown in FIG.

  FIG. 7 shows a torque diagram of the engine 2 as in FIG. 22, where the horizontal axis represents the engine speed n (rpm; rev / min) and the vertical axis represents the torque T (N · m). Yes. The function 66a corresponds to the target torque line L1 on the torque diagram shown in FIG.

  In the pump absorption torque calculator 66, the target absorption torque Tp_com of the hydraulic pump 3 corresponding to the current engine target speed n_com is calculated according to the function 66a.

  In the control current calculator 67, a control current pc-epc corresponding to the pump target absorption torque Tp_com is calculated.

  The storage device in the controller 6 stores a functional relation 67a in which the control current pc-epc increases in accordance with the increase in the pump target absorption torque Tp_com in the form of a data table.

  In the control current calculator 67, the control current pc-epc corresponding to the current pump target absorption torque Tp_com is calculated according to the functional relationship 67a.

  A control current pc-epc is output from the controller 6 to the pump control valve 5 to change the pump control valve 5 via the servo piston. The pump control valve 5 prevents the product of the discharge pressure PRp (kg / cm 2) of the hydraulic pump 3 and the capacity q (cc / rev) of the hydraulic pump 3 from exceeding the pump absorption torque Tp_com corresponding to the control current pc-epc. The tilt angle of the swash plate of the hydraulic pump 3 is PC-controlled.

  Note that this embodiment can also be applied to a construction machine equipped with an electric turning system in which the upper turning body of the construction machine 1 is turned by an electric actuator.

  In the above-described embodiment, the determination that the operation means 41 to 44 is switched from the non-operation state to the operation state is not limited to this, and the operation amount of the operation means 41 to 44 is a predetermined amount. When larger than a threshold value, you may determine with the operation means 41-44 having switched from the non-operation state to the operation state.

DESCRIPTION OF SYMBOLS 1 Construction machine 2 Engine 3 Hydraulic pump 4 Engine controller 5 Pump control valve 6 Controller 7-9 Hydraulic sensor 10 PTO shaft 11 Generator motor 12 Accumulator 31-36 Hydraulic actuator 41, 42 Operation lever 43, 44 Travel lever 50 Target flow rate calculation part 61 First Engine Target Speed Calculation Unit 63 Fourth Engine Target Speed Calculation Unit 64 Maximum Value Selection Unit 65, 501 Minimum Value Selection Unit 70 Pump Output Limit Calculation Unit 101 Filter 102 Engine Output Calculation Unit 103 Target Engine Output Calculation Unit 104 engine target speed addition value calculation unit 105 addition unit 106 branching unit 500 relief pump output limit value calculation unit

Claims (2)

A hydraulic pump driven by an engine;
A hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied;
Operating means for operating each hydraulic actuator;
First target speed setting means for setting a first target speed of the engine;
Second target speed calculating means for calculating a second target speed for limiting the maximum target speed of the engine as the load pressure of the hydraulic pump increases;
A rotational speed control means for controlling the engine rotational speed so as to coincide with the lower target rotational speed of the first target rotational speed and the second target rotational speed;
A generator motor coupled to the output shaft of the engine;
A capacitor that accumulates the power generated by the generator motor and supplies the power to the generator motor;
When the load pressure of the hydraulic pump is suddenly switched from a high state to a low state, the engine torque of the generator motor is increased until the actual rotational speed of the engine rises above a preset value with respect to the target rotational speed. Control means for controlling the engine speed so as to match the target speed using an assist action;
An engine control device comprising: A hydraulic pump driven by an engine;
A hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied;
Operating means for operating each hydraulic actuator;
First target speed setting means for setting a first target speed of the engine;
Second target speed calculating means for calculating a second target speed for limiting the maximum target speed of the engine as the load pressure of the hydraulic pump increases;
A rotational speed control means for controlling the engine rotational speed so as to coincide with the lower target rotational speed of the first target rotational speed and the second target rotational speed;
A generator motor coupled to the output shaft of the engine;
A capacitor that accumulates the power generated by the generator motor and supplies the power to the generator motor;
As the load pressure of the hydraulic pump decreases from a high state to a low state, the second target rotational speed increases, so that the actual rotational speed of the engine is greater than a preset value than the target rotational speed. If the engine speed is smaller than the target rotational speed, the actual rotational speed becomes equal to the target rotational speed using the engine torque assist action of the generator motor until the actual rotational speed rises to a value smaller than a preset value. Control means for controlling the engine speed;
An engine control device comprising:

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