Control device for construction machinery and construction machinery equipped with the same

Abstract

To provide a control device of a construction machine capable of settling engine speed at an early stage, and a construction machine equipped with the control device.SOLUTION: An engine control device 100A is equipped with an engine speed sensor 101, and a control device 50. The control portion 50 executes feedforward control that computes load torque speed Trs that is time change of load torque Tr applied to an engine 10 on the basis of discharge amount Q instructed to a first hydraulic pump 11, and corrects a target rotation number according to at least the load torque speed, and a feedback control that corrects the target rotation number according to difference between the inputted target rotation number Nd of the engine rotation number Nr detected by the engine speed sensor 101.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a control device for construction machinery and construction machinery equipped with the same.

Background Art

[0002] Conventionally, construction machinery having an engine, a hydraulic pump that discharges hydraulic oil by the driving force of the engine, and an actuator that is driven by receiving the supply of hydraulic oil from the hydraulic pump is known. The engine is rotationally driven so as to achieve a target rotational speed. On the other hand, the hydraulic pump receives a command value of the discharge amount (tilt command) and is driven so as to achieve the discharge amount. The hydraulic pump and the engine are connected via a coupling device such as a coupling. When an operator performs an operation for driving the actuator, the torque of the hydraulic pump becomes a load torque on the engine. As a result, the rotational speed of the engine may not be able to maintain the target rotational speed, and it may not be possible to ensure a desirable operability according to the operator's operation.

[0003] Patent Document 1 discloses an engine control technique that combines feedforward control and feedback control in order to improve the operability in such construction machinery. Specifically, the engine control device includes a required load calculation means for calculating, as a required load, the output of the engine necessary to drive the hydraulic pump in accordance with the operation of the actuator, and an engine controller. When the required load is calculated by the required load calculation means, the engine controller includes a feedforward control means for adding a preset fuel injection increase amount according to the required load to the fuel injection amount of the engine, and when the fuel injection amount is increased by the feedforward control means, if the deviation between the peak value of the actual rotational speed and the target rotational speed exceeds a predetermined determination threshold value, injection amount correction means for decreasing and correcting the preset fuel injection increase amount.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technology described in Patent Document 1, since the relationship between the load torque and the correction command amount of the engine speed is fixed in advance, the correction amount is added to the target speed regardless of the speed (time change) of the load torque. For this reason, as long as the magnitude of the load torque does not change, the state where the command correction amount is added to the target speed is maintained. Therefore, even when the load torque is static, the engine speed does not become static at the target speed, and there is a problem that the fuel consumption deteriorates.

[0006] An object of the present invention is to provide a control device for a construction machine capable of quickly stabilizing the engine speed and a construction machine equipped with the same.

Means for Solving the Problems

[0007] Provided by the present invention is a control device for a construction machine including an engine, an engine controller that controls the engine according to a rotational speed command signal, a variable displacement hydraulic pump that is driven by the engine and discharges hydraulic oil, and an actuator that operates by receiving the supply of the hydraulic oil from the hydraulic pump. The control device includes a rotational speed detection unit that detects the rotational speed of the engine, and a control unit that corrects the input target rotational speed of the engine and inputs the rotational speed command signal to the engine controller. The control unit can execute feedforward control and feedback control respectively. In the feedforward control, the control unit calculates the load torque speed applied to the engine based on the discharge amount commanded for the hydraulic pump, and corrects the target rotational speed at least according to the load torque speed. In the feedback control, the control unit corrects the target rotational speed according to the deviation between the target rotational speed and the rotational speed detected by the rotational speed detection unit. The load torque speed is the time change of the load torque applied to the engine.

[0008] According to this configuration, the feedforward control executed by the control unit suppresses the amount of engine rotational speed reduction with respect to the load torque of the hydraulic pump, and the feedback control can quickly stabilize the engine rotational speed at the target rotational speed. In particular, in the feedforward control, since the correction amount of the target rotational speed is determined according to the load torque speed, in the case where the input speed is slow and the amount of rotational speed reduction is small even with the same load torque, it is possible to suppress the correction amount, quickly stabilize the engine rotational speed, and suppress the fuel consumption of the engine more than the conventional engine control device.

[0009] In the above configuration, it is further provided with a pressure detection unit that detects the pump pressure of the hydraulic pump, and it is desirable that the control unit calculates the load torque speed based on the discharge amount, the rotational speed detected by the rotational speed detection unit, and the pump pressure detected by the pressure detection unit.

[0010] According to this configuration, the latest load torque speed can be easily calculated from the actual rotational speed of the engine and the pump pressure of the hydraulic pump.

[0011] In the above configuration, it is further provided with an operation detection unit that detects that the actuator is operating. When the operation detection unit detects that the actuator is operating, it is desirable for the control unit to stop the execution of the feedforward control.

[0012] According to this configuration, during the operation of the construction machine, it is possible to prevent the execution of the feedforward control according to the variation of the load torque speed and suppress the excessive rotational speed variation of the engine.

[0013] In the above configuration, in the feedforward control, it is desirable for the control unit to correct the target rotational speed so that the larger the calculated load torque speed, the larger the target rotational speed.

[0014] According to this configuration, even when the speed of the load torque acting on the engine is large, by setting a large correction value for the target rotational speed, it is possible to reduce a sudden decrease in the rotational speed of the engine.

[0015] In the above configuration, in the feedforward control, it is desirable for the control unit to set the maximum value of the correction value of the target rotational speed according to the load torque speed and correct the target rotational speed so as to maintain the maximum value for a certain period of time.

[0016] According to this configuration, since the maximum value of the rotational speed correction value in the feedforward control is maintained for a certain period of time, the rotational speed command for the engine is maintained in a region where it is high, and it is possible to further reduce the decrease in the rotational speed immediately after the generation of the load torque.

[0017] In the above configuration, a supercharging pressure detection unit for detecting the supercharging pressure of the engine is further provided, and in the feedforward control, it is desirable for the control unit to correct the target rotational speed according to the load torque speed and the supercharging pressure detected by the supercharging pressure detection unit.

[0018] According to this configuration, even in a configuration where the output characteristics of the engine change according to the boost state of the engine, it is possible to appropriately correct the target rotational speed according to the supercharging pressure, and it is possible to prevent the overshoot (fuel consumption deterioration) of the rotational speed due to unnecessary correction during high supercharging.

[0019] In the above configuration, an operating device for operating the actuator and an input unit for inputting the target rotational speed of the engine are further provided, and the control unit may set the discharge amount commanded to the hydraulic pump according to the operation amount of the operating device.

[0020] According to this configuration, with respect to the operation of the actuator by the operator, the control unit suppresses the amount of engine rotational speed decrease with respect to the load torque of the hydraulic pump by the feedforward control executed, and can quickly stabilize the engine rotational speed at the target rotational speed by the feedback control.

[0021] Further, provided by the present invention is a construction machine. The construction machine includes an engine, a variable displacement hydraulic pump driven by the engine to discharge hydraulic oil, an actuator that operates by receiving the hydraulic oil discharged from the hydraulic pump, and a control device for the construction machine as described above that controls the rotational speed of the engine.

[0022] According to this configuration, it is possible to provide a construction machine capable of quickly stabilizing the rotational speed of the engine.

Effects of the Invention

[0023] According to the present invention, it is possible to provide a control device for a construction machine capable of quickly stabilizing the engine speed, and a construction machine equipped with the same.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0025] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0026] Figure 1 shows a hydraulic excavator 100 (construction machine) equipped with an engine control device 100A (Figure 2) according to an embodiment of the present invention. This hydraulic excavator 100 includes a crawler-type lower traveling body 1 capable of traveling on a traveling surface, an upper revolving body 2 (machine body) mounted on the lower traveling body 1 so as to be capable of revolving around a turning center axis perpendicular to the traveling surface, and a work attachment 3 mounted on the upper revolving body 2. The work attachment 3 includes a boom 4 supported by the upper revolving body 2 so as to be able to move up and down, an arm 5 rotatably connected to the tip of the boom 4, and a bucket 6 rotatably connected to the tip of the arm 5. The upper revolving body 2 has a revolving frame 2S and a cab 2A.

[0027] The hydraulic excavator 100 further includes a boom cylinder 7 that operates to cause the boom 4 to move up and down with respect to the upper revolving body 2, an arm cylinder 8 that operates to cause the arm 5 to rotate with respect to the boom 4, and a bucket cylinder 9 that operates to cause the bucket 6 to rotate with respect to the arm 5.

[0028] Figure 2 is a hydraulic circuit diagram of the engine control device 100A (control device) according to the present embodiment. As shown in Figure 2, the engine control device 100A includes a first hydraulic pump 11 (hydraulic pump) and a second hydraulic pump 12 connected to an engine 10, a first pump pressure sensor 11P, a second pump pressure sensor 12P, a tank T, a pilot pump 20, the boom cylinder 7, the arm cylinder 8, a boom control valve 15, an arm control valve 16, a first valve proportional valve 21, a second valve proportional valve 22, a third valve proportional valve 23, a fourth valve proportional valve 24, a lever lock valve 25, an operation unit 30, a control unit 50, and an ECU 55. In Figure 2, the illustration of the bucket cylinder 9, the swing motor provided in the swing frame 2S, and the hydraulic circuit related thereto is omitted.

[0029] Engine 10 receives a fuel injection command signal and rotates by injecting fuel in an amount corresponding to the signal, generating a driving force. Engine 10 has an engine speed sensor 101 (rotation speed detection unit) and a supercharging pressure sensor 102. Engine speed sensor 101 detects the rotation speed of engine 10 and inputs a signal corresponding to the detection result to control unit 50. Similarly, supercharging pressure sensor 102 detects the supercharging pressure of engine 10 and inputs a signal corresponding to the detection result to control unit 50.

[0030] First hydraulic pump 11 mainly discharges hydraulic oil for operating boom cylinder 7. Second hydraulic pump 12 discharges hydraulic oil for operating arm cylinder 8. Pilot pump 20 supplies pilot oil to each valve proportional valve. First hydraulic pump 11, second hydraulic pump 12, and pilot pump 20 are connected to the output shaft of engine 10 via a coupling joint and are driven by engine 10. In FIG. 2, the connection between engine 10 and pilot pump 20 is not shown.

[0031] In this embodiment, first hydraulic pump 11 and second hydraulic pump 12 are variable displacement hydraulic pumps. In other words, first hydraulic pump 11 has first pump proportional valve 111, and second hydraulic pump 12 has second hydraulic pump proportional valve 121. These proportional valves open in response to a command signal received from control unit 50 and adjust the discharge amount (tilt) of first hydraulic pump 11 and second hydraulic pump 12.

[0032] First pump pressure sensor 11P (pressure detection unit) detects the pump pressure of first hydraulic pump 11 (the pressure of the hydraulic oil discharged from first hydraulic pump 11). Similarly, second pump pressure sensor 12P detects the pump pressure of second hydraulic pump 12 (the pressure of the hydraulic oil discharged from second hydraulic pump 12). Signals corresponding to the pump pressures detected by these pump pressure sensors are input to control unit 50.

[0033] The boom cylinder 7 is an actuator that operates to cause the boom 4 to perform a boom lowering operation and a boom raising operation by receiving the supply of hydraulic oil discharged by the first hydraulic pump 11. The boom cylinder 7 includes a cylinder body and a piston rod that includes a partition portion (piston portion) that partitions the cylinder body into a head chamber and a rod chamber and is relatively movable with respect to the cylinder body. In the boom cylinder 7, it is possible to extend so as to cause the boom 4 to perform the boom raising operation by receiving the hydraulic oil discharged by the first hydraulic pump 11 into the head chamber, while it is possible to contract so as to cause the boom 4 to perform the boom lowering operation by receiving the hydraulic oil discharged by the first hydraulic pump 11 into the rod chamber.

[0034] The arm cylinder 8 is an actuator that operates to cause the arm 5 to perform an arm pushing operation and an arm pulling operation by receiving the supply of hydraulic oil discharged by the second hydraulic pump 12. The arm cylinder 8 also includes a cylinder body and a piston rod that includes a partition portion (piston portion) that partitions the cylinder body into a head chamber and a rod chamber and is relatively movable with respect to the cylinder body.

[0035] As shown in FIG. 2, a boom operation detection sensor 7S is attached to the boom cylinder 7, and an arm operation detection sensor 8S is attached to the arm cylinder 8. The boom operation detection sensor 7S can detect the driving state of the boom 4 by detecting the expansion and contraction stroke of the boom cylinder 7. Similarly, the arm operation detection sensor 8S can detect the driving state of the arm 5 by detecting the expansion and contraction stroke of the arm cylinder 8. In the present embodiment, the boom operation detection sensor 7S and the arm operation detection sensor 8S are stroke sensors, but in other embodiments, they may be angle sensors that detect the angles of the boom 4 and the arm 5.

[0036] The boom control valve 15 is interposed between the first hydraulic pump 11 and the boom cylinder 7, and opens and closes to change the flow rate of the hydraulic oil supplied from the first hydraulic pump 11 to the boom cylinder 7. Specifically, the boom control valve 15 is a pilot-operated three-position directional control valve having a boom lowering pilot port 151 and a boom raising pilot port 152.

[0037] When no pilot pressure is input to either the boom lowering or the boom raising pilot ports 151, 152, the boom control valve 15 is held at the neutral position P2, blocking the passage between the first hydraulic pump 11 and the boom cylinder 7. A relief valve (not shown) is disposed at the portion between the first hydraulic pump 11 and the boom control valve 15.

[0038] When a boom lowering pilot pressure is input to the boom lowering pilot port 151, the boom control valve 15 is switched from the neutral position P2 to the boom lowering position P1 by a stroke corresponding to the magnitude of the boom lowering pilot pressure. Thereby, the boom control valve 15 opens to allow the hydraulic oil to be supplied from the first hydraulic pump 11 to the rod chamber of the boom cylinder 7 at a flow rate corresponding to the stroke, and also to allow the hydraulic oil to be discharged from the head chamber of the boom cylinder 7. As a result, the boom cylinder 7 is driven in the boom lowering direction at a speed corresponding to the boom lowering pilot pressure.

[0039] When a boom raising pilot pressure is input to the boom raising pilot port 152, the boom control valve 15 is switched from the neutral position P2 to the boom raising position P3 by a stroke corresponding to the magnitude of the boom raising pilot pressure. Thereby, the boom control valve 15 opens to allow the hydraulic oil to be supplied from the first hydraulic pump 11 to the head chamber of the boom cylinder 7 at a flow rate corresponding to the stroke, and also to allow the hydraulic oil to be discharged from the rod chamber of the boom cylinder 7. As a result, the boom cylinder 7 is driven in the boom raising direction at a speed corresponding to the boom raising pilot pressure.

[0040] The arm control valve 16 is interposed between the second hydraulic pump 12 and the arm cylinder 8, and performs an opening / closing operation so as to change the flow rate of the hydraulic oil supplied from the second hydraulic pump 12 to the arm cylinder 8. Specifically, the arm control valve 16 is a pilot-operated three-position directional control valve having an arm push pilot port 161 and an arm pull pilot port 162.

[0041] When no pilot pressure is input to either the arm push or arm pull pilot ports 161, 162, the arm control valve 16 is held at the neutral position P5, blocking between the second hydraulic pump 12 and the arm cylinder 8. Note that a relief valve (not shown) is disposed at the portion between the second hydraulic pump 12 and the arm control valve 16.

[0042] When an arm push pilot pressure is input to the arm push pilot port 161, the arm control valve 16 is switched from the neutral position P5 to the arm push position P4 at a stroke corresponding to the magnitude of the arm push pilot pressure. Thereby, the arm control valve 16 opens to allow the hydraulic oil to be supplied from the second hydraulic pump 12 to the rod chamber of the arm cylinder 8 at a flow rate corresponding to the stroke, and also to allow the hydraulic oil to return from the head chamber of the arm cylinder 8 to the tank. Thereby, the arm cylinder 8 is driven in the arm push direction at a speed corresponding to the arm push pilot pressure.

[0043] When the arm pull pilot pressure is input to the arm pull pilot port 162 of the arm control valve 16, the valve is switched from the neutral position P5 to the arm pull position P6 with a stroke corresponding to the magnitude of the arm pull pilot pressure. Thereby, the valve is opened to allow the hydraulic oil to be supplied from the second hydraulic pump 12 to the head chamber of the arm cylinder 8 at a flow rate corresponding to the stroke, and to allow the hydraulic oil to return from the rod chamber of the arm cylinder 8 to the tank. As a result, the arm cylinder 8 is driven in the arm pull direction at a speed corresponding to the arm pull pilot pressure.

[0044] The operation unit 30 is disposed in the cab 2A and receives various operations for operating the hydraulic excavator 100 by the operator. The operation unit 30 includes a boom operation unit 31, an arm operation unit 32, a dial switch 33, and a lever lock switch 34.

[0045] The boom operation unit 31 (operation device) receives a boom lowering operation and a boom raising operation for causing the boom 4 to perform a boom lowering operation and a boom raising operation, respectively. Specifically, the boom operation unit 31 includes a boom operation lever 31A for receiving an operation for driving the boom cylinder 7, and a boom command output unit 31B.

[0046] The boom operation lever 31A is a member that can rotate in response to the boom lowering operation and the boom raising operation by the operator. The boom lowering operation and the boom raising operation are operations for rotating the boom operation lever 31A in opposite directions to each other.

[0047] The boom command output unit 31B inputs a command signal corresponding to the operation to the control unit 50 in conjunction with the boom raising operation and the boom lowering operation applied to the boom operation lever 31A. The command signal includes information corresponding to the operation direction and the operation amount of the boom operation lever 31A.

[0048] The arm operation unit 32 (operation device) receives an arm pushing operation and an arm pulling operation for causing the arm 5 to perform an arm pushing motion and an arm pulling motion, respectively. Specifically, the arm operation unit 32 includes an arm operation lever 32A that receives an operation for driving the arm cylinder 8, and an arm command output unit 32B.

[0049] The arm operation lever 32A is a member that can rotate by receiving an arm pushing operation and an arm pulling operation by the operator. The arm pushing operation and the arm pulling operation are operations for rotating the arm operation lever 32A in opposite directions to each other.

[0050] The arm command output unit 32B inputs a command signal corresponding to one of the arm pushing operation and the arm pulling operation applied to the arm operation lever 32A to the control unit 50 in conjunction with the operation. The command signal includes information corresponding to the operation direction and operation amount of the arm operation lever 32A.

[0051] The dial switch 33 receives an input of the target rotational speed of the engine 10. In the present embodiment, the dial switch 33 is a rotatable dial and is operated (rotated) by the operator to set the target rotational speed of the engine 10. The dial switch 33 includes an operation amount transmission unit (not shown). When the operator rotates the dial switch 33 to set the target rotational speed, a signal (operation amount signal, rotational speed signal) corresponding to the target rotational speed is input to the control unit 50 by the operation amount transmission unit.

[0052] The lever lock switch 34 is a switch for switching the supply and cutoff of pilot oil to the boom control valve 15 and the arm control valve 16. When the lever lock switch 34 is set to ON, a command signal (drive signal) is input to the lever lock valve 25 so as to allow the supply of pilot oil to the first valve proportional valve 21, the second valve proportional valve 22, the third valve proportional valve 23, and the fourth valve proportional valve 24. On the other hand, when the lever lock switch 34 is set to OFF, a command signal is input to the lever lock valve 25 so as to prevent the supply of pilot oil to the first valve proportional valve 21, the second valve proportional valve 22, the third valve proportional valve 23, and the fourth valve proportional valve 24.

[0053] The first valve proportional valve 21 and the second valve proportional valve 22 operate so as to allow the pilot pressure corresponding to the operation input to the boom operation lever 31A of the boom operation unit 31 to be input from the pilot pump 20 to the boom control valve 15. Similarly, the third valve proportional valve 23 and the fourth valve proportional valve 24 open so as to allow the pilot pressure corresponding to the operation input to the arm operation lever 32A of the arm operation unit 32 to be input from the pilot pump 20 to the arm control valve 16. In other embodiments, the boom operation unit 31 and the arm operation unit 32 may have remote control valves, and the pilot pressures of the boom control valve 15 and the arm control valve 16 may be directly adjusted according to the operation amounts received by the boom operation lever 31A and the arm operation lever 32A. Also, each lever may be an electric lever.

[0054] The lever lock valve 25 is arranged to be interposed between the pilot pump 20 and each valve proportional valve. The lever lock valve 25 opens by receiving a signal (lock release signal) corresponding to the state of the lever lock switch 34 from the control unit 50, and switches between a state allowing the supply of pilot oil to each valve proportional valve and a state blocking it.

[0055] The control unit 50 sets a correction value for the target rotational speed input to the dial switch 33, and inputs a command signal corresponding to the correction value to the ECU 55. FIG. 3 is a block diagram of the control unit 50 of the engine control device 100A according to the present embodiment.

[0056] The control unit 50 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory) that stores a control program, a RAM (Random Access Memory) used as a working area for the CPU, and the like. The control unit 50 functions to include each functional unit of an arithmetic unit 501, a determination unit 502, and a storage unit 503 by the CPU executing the control program stored in the ROM. These functional units do not have a physical entity and correspond to units of functions executed by the control program. Note that all or part of the control unit 50 is not limited to being provided inside the hydraulic excavator 100, and may be arranged at a position different from the hydraulic excavator 100 when the hydraulic excavator 100 is remotely controlled. Further, the control program may be transmitted from a remote server (management device), cloud, or the like to the control unit 50 inside the hydraulic excavator 100 and executed, or the control program may be executed on the server or cloud, and various generated command signals may be transmitted to the hydraulic excavator 100.

[0057] The arithmetic unit 501 executes arithmetic processing required in various processes executed by the control unit 50. The determination unit 502 executes determination processing required in various processes executed by the control unit 50. The storage unit 503 stores parameters and threshold values required in various processes executed by the control unit 50.

[0058] Further, the control unit 50 receives various signals from the boom operation lever 31A, the arm operation lever 32A, the dial switch 33, the lever lock switch 34, the engine speed sensor 101, the supercharging pressure sensor 102, the first pump pressure sensor 11P, the second pump pressure sensor 12P, the boom movement detection sensor 7S, and the arm movement detection sensor 8S. Furthermore, the control unit 50 inputs various command signals to the ECU 55, the first pump proportional valve 111, the second hydraulic pump proportional valve 121, the first valve proportional valve 21, the second valve proportional valve 22, the third valve proportional valve 23, the fourth valve proportional valve 24, and the lever lock valve 25.

[0059] In particular, the control unit 50 converts the operation lever amount signal received from the operation unit 30 into a target pump discharge command signal and inputs it to the first pump proportional valve 111 and the second hydraulic pump proportional valve 121. Also, the control unit 50 converts the operation lever amount signal received from the operation unit 30 into a target valve spool stroke amount command signal and inputs it to the first valve proportional valve 21, the second valve proportional valve 22, the third valve proportional valve 23, and the fourth valve proportional valve 24. Furthermore, the control unit 50 converts the dial switch operation amount received by the dial switch 33 into a target engine speed command signal.

[0060] The ECU (Engine Control Unit) 55 receives a speed command signal (command signal) from the control unit 50 and controls the engine 10 to rotate at a predetermined actual speed with a fuel injection amount corresponding to the speed command signal.

[0061] In this embodiment, the control unit 50 is capable of performing feedforward control and feedback control. In the feedforward control, the control unit 50 determines the discharge amount Q (discharge amount command) of the first hydraulic pump 11 and the second hydraulic pump 12 according to the operation amount of the operation input to the operation unit 30, and from the discharge amount Q, the rotation speed Nr detected by the engine rotation speed sensor 101, and the pump pressures P detected by the first pump pressure sensor 11P and the second pump pressure sensor 12P, calculates the load torque speed Trs which is the time change of the load torque Tr applied to the engine 10, and sets a correction value for the target rotation speed of the engine 10 at least according to the load torque speed. On the other hand, in the feedback control, the control unit 50 sets a correction value for the target rotation speed of the engine 10 according to the deviation between the target rotation speed Nd (rotation speed command) input through the dial switch 33 and the rotation speed Nr detected by the engine rotation speed sensor 101.

[0062] Hereinafter, a mode in which the first hydraulic pump 11 discharges hydraulic oil toward the boom cylinder 7 and the rotation speed of the engine 10 is adjusted as the boom operation unit 31 of the operation unit 30 is operated will be described. FIG. 4 is a flowchart showing the engine control process executed by the control unit 50 in the engine control device 100A according to this embodiment. FIG. 5 is a graph showing the transition of the engine rotation speed in the hydraulic excavator 100 equipped with the engine control device 100A. In FIG. 5, the rotation speed command value to the ECU 55 is shown by a broken line graph, and the actual rotation speed of the engine 10 is shown by a solid line graph. FIG. 6 is a graph showing the relationship between the operation amount of the operation lever and the flow rate of the hydraulic pump in the hydraulic excavator 100 equipped with the engine control device 100A. FIG. 7 is a graph showing the relationship between the load torque speed and the rotation speed correction amount of the engine 10 in the hydraulic excavator 100 equipped with the engine control device 100A.

[0063] In the hydraulic excavator 100, when the operator starts the engine key in the cab 2A, the engine 10 starts (step S1 in FIG. 4). At this time, the dial switch 33 is set to the default setting (Low idle), the lever lock switch 34 is in the OFF state, and the pilot hydraulic circuit is closed by the lever lock valve 25. That is, the operation unit 30 is in the non-operation state. At this time, as shown by the arrow A in FIG. 5, the engine 10 is rotating at the idle speed.

[0064] Next, the operator operates the dial switch 33 to set the target rotational speed of the engine 10 (step S2). Next, the determination unit 502 of the control unit 50 determines whether the lever lock switch 34 has been operated to the ON state (step S3). Here, when the lever lock switch 34 is set to the ON state, the pilot hydraulic circuit is opened (YES in step S3). When the lever lock switch 34 is in the OFF state (NO in step S3), the determination unit 502 repeats the determination in step S3 until the lever lock switch 34 is set to the ON state. At this time, as shown by the arrow B in FIG. 5, the engine 10 in the no-load state is rotating at the target rotational speed (actual rotational speed).

[0065] When the lever lock switch 34 is set to the ON state, the determination unit 502 determines whether there is a lever operation input to the boom operation lever 31A of the operation unit 30 (step S4). Here, when there is a lever operation input (YES in step S4), the control unit 50 starts the forward forward control (FF control). When there is no lever operation input (NO in step S4), the determination unit 502 repeats the determination in step S4.

[0066] When feedforward control is started (step S5), the arithmetic unit 501 calculates the load torque speed (step S6). At this time, the arithmetic unit 501 determines the required pump flow rate Q (L / min) from the amount of operation received by the operation lever 31A of the operation unit 30 and the map information shown in FIG. 6 stored in the storage unit 503 in advance. Further, the arithmetic unit 501 calculates the required pump tilt q (cc / rev) based on the following formula 1 from the actual engine speed Nr (rpm) of the engine 10 detected by the engine speed sensor 101 and the above-mentioned required pump flow rate Q.

Equation

[0067] Furthermore, the arithmetic unit 501 calculates the output torque of the latest first hydraulic pump 11, that is, the load torque Tr (Nm), based on the following formula 2 from the required pump tilt q calculated based on formula 1 and the actual pump pressure P (MPa) (pump pressure) detected by the first pump pressure sensor 11P.

Equation

[0068] In addition, the arithmetic unit 501 calculates the load torque speed Trs (Nm / sec) by differentiating the load torque Tr calculated by formula 2 with the sampling time Δt (sec) as shown in the following formula 3.

Equation

[0069] Next, the arithmetic unit 501 determines a correction value ΔNff for the target engine speed command from the characteristic value map of FIG. 7 stored in the storage unit 503 in advance with respect to the load torque speed Trs calculated by Expression 3 (step S7). In the characteristic value map, the correction value is set such that the larger the calculated load torque speed Trs, the larger the correction value ΔNff for the target engine speed command. Note that a regression equation of a graph as shown in FIG. 7 is stored in the storage unit 503 in advance, and the arithmetic unit 501 may calculate the correction value ΔNff based on the regression equation.

[0070] In the present embodiment, the engine control device 100A can acquire information corresponding to the supercharging pressure detected by the supercharging pressure sensor 102 of the engine 10. For this reason, it is desirable that a plurality of characteristic value maps are stored in the storage unit 503 according to the supercharging pressure (a plurality of pressure regions) of the engine 10. When the engine 10 is a supercharged engine, the possible output is determined by the magnitude of the supercharging pressure. For this reason, as described above, by setting the correction value ΔNff according to the supercharging pressure, more stable rotational speed control can be performed.

[0071] Next, the control unit 50 inputs a command signal obtained by reflecting the correction value ΔNff determined as described above in the target engine speed input to the dial switch 33 to the ECU 55 (step S8, FF engine speed command correction). The ECU 55 that has received the command signal corresponding to such a corrected engine speed corrects the fuel injection amount command value and the like corresponding to the correction amount, and increases the actual engine speed of the engine 10. In the present embodiment, as shown by the arrow C in FIG. 5, the control unit 50 inputs a command signal to the ECU 55 so as to maintain the maximum value of the correction value of the target engine speed for a certain period of time.

[0072] Eventually, due to the sudden increase in the actual load torque immediately after the start of operation of the boom operation lever 31A, the engine speed temporarily decreases as shown by the arrow D in FIG. 5. However, since the engine speed command value is maintained at a high level by the feedforward control in advance, a high fuel injection state is maintained, and the decrease in the engine speed of the engine 10 can be suppressed.

[0073] After issuing a rotational speed command to ECU 55, the determination unit 502 of the control unit 50 determines whether the actuator (ACT), that is, the boom cylinder 7, has accelerated (step S9). In other words, in response to the discharge command to the first pump proportional valve 111 of the first hydraulic pump 11 and the valve stroke command to the boom control valve 15 described above, it is determined whether the hydraulic oil has flowed into the boom cylinder 7 and the boom 4 has been driven. Here, when the boom cylinder 7 is accelerating (YES in step S9), the control unit 50 ends the execution of the feedforward control (step S10) and shifts to the feedback control (FB control) (step S11). If the boom cylinder 7 is not accelerating in step S9 (NO in step S9), the storage unit 503 repeats the acceleration determination of the boom cylinder 7 in step S9.

[0074] When the feedback control is started in step S11, the calculation unit 501 calculates the rotational speed deviation (step S12). At this time, the calculation unit 501 calculates the deviation between the target rotational speed Nd (rpm) of the engine 10 set by the dial switch 33 and the actual engine rotational speed Nr (rpm) detected by the engine rotational speed sensor 101. Further, the calculation unit 501 calculates a rotational speed correction command value in the feedback control based on the deviation calculated above (step S13). In this embodiment, as shown in Equation 4 below, the deviation between the target rotational speed Nd (rpm) and the actual engine rotational speed Nr (rpm) is directly used as the rotational speed correction value ΔNfb.

Equation

[0075] Then, the control unit 50 inputs a command signal (corrected engine rotational speed command) corresponding to the calculated rotational speed correction value ΔNfb to the ECU 55 (step S14, arrow E in FIG. 5). The ECU 55 that has received the command signal corrects the fuel injection amount command and the like according to the correction amount, so that the rotational speed of the engine 10 is controlled to approach the target rotational speed (arrow F in FIG. 5).

[0076] Furthermore, the determination unit 502 of the control unit 50 determines whether the lever lock switch 34 has been switched to the OFF state (step S15). Here, when the lever lock switch 34 is in the OFF state (YES in step S15), the control unit 50 ends the feedforward control (step S16) and ends the engine control in FIG. 4. On the other hand, in step S15, when the lever lock switch 34 remains in the ON state (NO in step S15), the control unit 50 repeats the processing after step S12. That is, the feedback control continues to be executed so that the deviation between the actual engine speed and the target engine speed becomes zero.

[0077] As described above, in this embodiment, in response to the operation of the boom operation lever 31A and the load torque accompanying the rotation of the first hydraulic pump 11 acting on the engine 10, the control unit 50 can execute feedforward control and feedforward control respectively.

[0078] According to such a configuration, the control unit 50 suppresses the amount of engine 10 speed reduction with respect to the load torque of the first hydraulic pump 11 by feedforward control executed by the control unit 50, and can quickly stabilize the engine 10 speed at the target speed by feedback control. In particular, since the command correction amount in the feedforward control is determined according to the load torque speed, under conditions where the input speed is slow and the amount of speed reduction is small even with the same load torque, optimal speed correction control is possible while suppressing the correction amount. Therefore, the engine 10 speed can be quickly stabilized, and the fuel consumption of the engine 10 can be suppressed more than that of the conventional engine control device. Further, since the pump discharge amount command input by the control unit 50 to the first pump proportional valve 111 does not change according to the fluctuation of the engine speed, the pump discharge command is set by the operation amount input by the operator to the boom operation lever 31A, and flow compensation according to the operation amount becomes possible. Further, the engine 10 speed can be adjusted only by inputting a command signal corresponding to the corrected target speed to the ECU 55. As a result, since the correction control of the engine 10 speed does not intervene in the control parameters on the ECU 55 side, it is not necessary to change the designs of the engine 10 and the ECU 55 for the speed control, and the development period can be shortened and the cost can be reduced.

[0079] Furthermore, in the present embodiment, the control unit 50 calculates the load torque speed Trs from the set pump discharge amount Q, the rotation speed Nr detected by the engine speed sensor 101, and the pump pressure P of the first hydraulic pump 11 detected by the first pump pressure sensor 11P in the feedforward control.

[0080] Therefore, the latest load torque speed can be easily calculated from the actual rotation speed of the engine 10 and the discharge pressure of the first hydraulic pump 11.

[0081] Further, in the present embodiment, the engine control device 100A further includes a boom operation detection sensor 7S (operation detection unit) that detects that the boom cylinder 7 is operating. Then, after the boom operation lever 31A has received an operation for driving the boom cylinder 7, when the boom operation detection sensor 7S detects that the boom cylinder 7 is operating, the control unit 50 stops the execution of the feedforward control.

[0082] Therefore, it is possible to prevent the execution of the feedforward control according to the variation in the load torque speed during the operation of the hydraulic excavator 100, and suppress excessive rotational speed variation of the engine 10.

[0083] Also, in the present embodiment, in the feedforward control, the correction value is set such that the larger the calculated load torque speed, the larger the correction value of the target rotational speed.

[0084] According to such a configuration, even when the load torque speed acting on the engine 10 is large, by setting a large correction value of the target rotational speed, it is possible to reduce the amount of rapid decrease in the rotational speed of the engine 10.

[0085] Furthermore, in the present embodiment, in the feedforward control, the control unit 50 sets the maximum value of the correction value of the target rotational speed of the engine 10 according to the load torque speed, and corrects the target rotational speed so as to maintain the maximum value for a certain period of time.

[0086] According to such a configuration, since the maximum value of the rotational speed correction value in the feedforward control is held for a certain period of time, the rotational speed command value for the ECU 55 is held in a high region, and the amount of rotational speed decrease immediately after the generation of the load torque can be further reduced.

[0087] Furthermore, in the present embodiment, the engine control device 100A further includes a supercharging pressure sensor 102 (supercharging pressure detection unit) that detects the supercharging pressure of the engine 10. Then, in the feedforward control, the control unit 50 corrects the target rotational speed according to the load torque speed and the supercharging pressure detected by the supercharging pressure sensor 102.

[0088] According to such a configuration, even in a configuration where the output characteristics of the engine 10 change depending on the boost state of the engine 10, it is possible to set an appropriate correction amount of the target rotational speed according to the supercharging pressure, and prevent the overshoot (fuel consumption deterioration) of the rotational speed due to unnecessary correction during high supercharging.

[0089] As described above, the engine control device 100A according to the present invention and the hydraulic excavator 100 equipped with the same have been described. However, the present invention is not limited thereto, and for example, the following modified embodiments can be adopted.

[0090] (1) In the above embodiment, the boom operation lever 31A is operated and the load torque of the first hydraulic pump 11 is applied to the engine 10. However, in a machine that performs automatic operation, instead of the operation amount of the operation lever, the control unit 50 calculates the operating speeds or operating amounts of the boom 4, the arm 5, and the bucket 6 respectively, which are calculated to operate the work attachment 3 based on the target position, target plane, target posture, or target trajectory, etc. in the work, and uses them as operation commands to control the discharge amounts of the first hydraulic pump 11 or the second hydraulic pump 12 based on the operation commands.

[0091] (2) Also, in the above embodiment, the dial switch 33 is a rotatable dial, and it has been described in the aspect that the operator operates (rotates) the dial switch 33 to set the target rotational speed of the engine 10. However, in a machine that performs automatic operation, instead of rotating the dial switch 33, the control unit 50 may set the target rotational speed based on the work, operation, and machine state, etc. performed by the excavator 100.

[0092] (3) In the above-described embodiment, the boom operation lever 31A is operated and the load torque of the first hydraulic pump 11 is applied to the engine 10. The same applies to the second hydraulic pump 12. Further, when both the boom operation lever 31A and the arm operation lever 32A are operated and the load torques of the first hydraulic pump 11 and the second hydraulic pump 12 are respectively applied to the engine 10, the same arithmetic processing as described above may be executed based on the sum of the load torques of the respective pumps.

[0093] (4) Further, in the above-described embodiment, the hydraulic excavator 100 includes the first hydraulic pump 11 and the second hydraulic pump 12, but the present invention is not limited thereto, and one of the first hydraulic pump 11 and the second hydraulic pump 12 may be omitted. In such a case, the hydraulic oil discharged from the other hydraulic pump is supplied to the boom cylinder 7 and also supplied to the arm cylinder 8.

[0094] (5) Further, the tip attachment of the work attachment 3 is not limited to the bucket, and may be other tip attachments such as a grapple, a crusher, a breaker, a fork, etc. Further, the construction machine on which the control device of the present invention is mounted is not limited to the hydraulic excavator, and may be other construction machines.

[0095] (6) In the previous embodiment, the machine body is the lower traveling body 1, but the machine body is not limited to one that can travel like the lower traveling body 1, and may be a base installed at a specific location and supporting the upper swing body 2.

[0096] (7) In the present invention, correcting a predetermined command value such as the rotational speed may be to input a signal corresponding to the corrected command value to the input destination after correcting the command value, or to input the signal corresponding to the predetermined command value to the input destination after correcting it. In other words, the correction target may be the command value itself or the value (magnitude) of the signal corresponding thereto.

Description of reference numerals

[0097] 1 Lower traveling body 10 Engine 100 Hydraulic Excavator 100A Engine Control Device (Control Device) 101 Engine Speed Sensor (Speed Detection Unit) 102 Supercharger Pressure Sensor (Supercharger Pressure Detection Unit) 11 First Hydraulic Pump 111 First Pump Proportional Valve 11P First Pump Pressure Sensor (Pressure Detection Unit) 15 Boom Control Valve 151 Boom Lowering Pilot Port 152 Boom Raising Pilot Port 2 Upper Swing Structure 20 Pilot Pump 21 First Valve Proportional Valve 22 Second Valve Proportional Valve 25 Lever Lock Valve 3 Work Attachment 30 Operation Unit (Operation Device) 31 Boom Operation Unit 31A Boom Operation Lever 31B Boom Command Output Unit 33 Dial Switch (Rotation Speed Input Unit) 34 Lever Lock Switch 4 Boom 5 Arm 50 Control Unit 501 Calculation Unit 502 Judgment Unit 503 Memory Unit 55 ECU (Engine Controller) 6 Bucket 7 Boom Cylinder (Actuator) 7S Boom Operation Detection Sensor (Operation Detection Unit) 8 Arm Cylinder 8S Arm Operation Detection Sensor 9 Bucket Cylinder

Claims

1. A control device for a construction machine, comprising: an engine; an engine controller that controls the engine according to a rotational speed command signal; a variable displacement hydraulic pump driven by the engine; and an actuator that operates upon receiving the supply of hydraulic oil from the hydraulic pump, a rotational speed detection unit that detects the rotational speed of the engine, a control unit that corrects the target rotational speed of the engine input thereto and inputs the rotational speed command signal to the engine controller, the control unit calculating a load torque speed applied to the engine based on a discharge amount commanded for the hydraulic pump and correcting the target rotational speed according to the load torque speed by means of feed-forward control, and correcting the target rotational speed according to a deviation between the target rotational speed and the rotational speed detected by the rotational speed detection unit by means of feedback control, the control device for a construction machine being provided with the control unit.

2. further comprising a pressure detection unit that detects the pump pressure of the hydraulic pump, wherein the control unit calculates the load torque speed based on the discharge amount, the rotational speed detected by the rotational speed detection unit, and the pump pressure detected by the pressure detection unit, the control device for a construction machine according to Claim 1.

3. further comprising an operation detection unit that detects that the actuator is operating, wherein the control unit stops the execution of the feed-forward control when the operation detection unit detects that the actuator is operating, the control device for a construction machine according to Claim 1 or 2.

4. wherein, in the feed-forward control, the control unit corrects the target rotational speed such that the greater the calculated load torque speed, the greater the target rotational speed, the control device for a construction machine according to any one of Claims 1 to 3.

5. wherein, in the feed-forward control, the control unit sets a maximum value of a correction value of the target rotational speed according to the load torque speed and corrects the target rotational speed so as to maintain the maximum value for a certain period of time, the control device for a construction machine according to any one of Claims 1 to 4.

6. further comprising a supercharging pressure detection unit that detects the supercharging pressure of the engine, wherein, in the feed-forward control, the control unit corrects the target rotational speed according to the load torque speed and the supercharging pressure detected by the supercharging pressure detection unit, the control device for a construction machine according to any one of Claims 1 to 5.

7. an operating device for operating the actuator; an input unit for inputting a target rotational speed of the engine; further comprising: The control device for a construction machine according to any one of claims 1 to 6, wherein the control unit sets the discharge amount commanded to the hydraulic pump according to an operation amount of the operating device.

8. an engine; a variable displacement hydraulic pump driven by the engine to discharge hydraulic oil; an actuator that operates by receiving the hydraulic oil discharged from the hydraulic pump; a control device for a construction machine according to any one of claims 1 to 7, which controls the rotational speed of the engine; A construction machine comprising:

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