JP2016050424A - Construction machinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shovel capable of more properly limiting swing torque of an electric motor for a swing motion.SOLUTION: A shovel according to an embodiment of the present invention includes: lower machinery 1; a revolving super structure 3 that is loaded on the lower machinery 1; an electric motor 21 for a swing motion, which swings the revolving super structure 3; an inverter 20 that drives the electric motor 21 for the swing motion; and a controller 30 that controls the inverter 20. The controller 30 makes an upper limit of acceleration torque of the electric motor 21 for the swing motion lower when a temperature of at least one of the electric motor 21 for the swing motion and the inverter 20 is higher.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a construction machine equipped with a turning electric motor.

  An excavator is known that limits the torque output of a turning electric motor when the temperature of cooling water for cooling an inverter connected to the turning electric motor exceeds a predetermined temperature (see Patent Document 1).

JP 2010-222815 A

  However, if the torque output of the turning electric motor is excessively limited during the turning operation, the operation feeling may be deteriorated. Further, if the torque output of the turning electric motor is restricted during the turning deceleration, the deceleration torque of the turning electric motor is restricted, and there is a possibility that the turning stop may be delayed.

  In view of the above, it is desirable to provide a construction machine that can more appropriately limit the turning torque of the turning electric motor.

  A construction machine according to an embodiment of the present invention includes a lower traveling body, an upper turning body mounted on the lower traveling body, a turning electric motor that turns the upper turning body, and an inverter that drives the turning electric motor. And a controller for controlling the inverter, and the controller reduces the upper limit of the acceleration torque of the turning electric motor as the temperature of at least one of the turning electric motor and the inverter increases.

  By the above-mentioned means, a construction machine that can more appropriately limit the turning torque of the turning electric motor is provided.

It is a side view of the shovel which concerns on the Example of this invention. It is a block diagram which shows the structural example of the drive system of the shovel of FIG. It is a block diagram which shows the structural example of the controller mounted in the shovel of FIG. It is a graph which shows an example of the reference table which defines the relationship between an acceleration torque limit value and a load factor. It is a graph which shows an example of the reference table which defines the relationship between a speed limit value and a load factor. It is a flowchart which shows the flow of a turning limitation process. It is a graph which shows the time transition of various physical quantities in a rotation pressing work. It is a figure which shows the time transition of the turning angular velocity, turning energy, and turning torque of the electric motor for turning.

  First, the overall configuration of a construction machine according to an embodiment of the present invention and the configuration of its drive system will be described. FIG. 1 is a side view showing a configuration example of an excavator as a construction machine according to an embodiment of the present invention. Note that the present invention is not limited to the shovel, and can be applied to other construction machines as long as the electric motor for turning is mounted.

  An upper swing body 3 is mounted on a lower traveling body 1 of the shovel shown in FIG. A boom 4 is attached to the upper swing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5. The boom 4, the arm 5, and the bucket 6 are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively. Further, the upper swing body 3 is provided with a cabin 10 and is mounted with a power source such as an engine.

  FIG. 2 is a block diagram showing a configuration example of the drive system of the shovel shown in FIG. In FIG. 2, the mechanical power system is indicated by a double line, the high-pressure hydraulic line is indicated by a thick solid line, the pilot line is indicated by a broken line, and the electric drive / control system is indicated by a thin solid line.

  The engine 11 and the motor generator 12 are connected to two input shafts of the speed reducer 13, respectively. A main pump 14 and a pilot pump 15 as hydraulic pumps are connected to the output shaft of the speed reducer 13. A control valve 17 is connected to the main pump 14 via a high pressure hydraulic line 16. An operation device 26 is connected to the pilot pump 15 via a pilot line 25.

  The control valve 17 is a hydraulic control device that controls a hydraulic system in the shovel. In this embodiment, the control valve 17 is connected to various actuators such as a right traveling hydraulic motor 2A, a left traveling hydraulic motor 2B, a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9 through a high pressure hydraulic line.

  Power storage system 120 includes a power storage device 19, a step-up / down converter 19a, and a DC bus 19b. The power storage device 19 is a capacitor, for example, and is connected to the motor generator 12 via the step-up / down converter 19 a, the DC bus 19 b, and the inverter 18. The power storage device 19 is connected to the turning electric motor 21 via the step-up / down converter 19 a, the DC bus 19 b, and the inverter 20. The step-up / step-down converter 19a is disposed between the power storage device 19 and the DC bus 19b so that the voltage level of the DC bus 19b falls within a certain range according to the operating state of the motor generator 12 and the turning electric motor 21. The control for switching between the step-up operation and the step-down operation is performed. The DC bus 19b is disposed between the step-up / step-down converter 19a and each of the inverter 18 and the inverter 20, and enables transmission and reception of power among the power storage device 19, the motor generator 12, and the turning electric motor 21.

  The inverter 18 outputs a motor drive current to the motor generator 12 according to the torque current command value from the controller 30. Further, the inverter 20 outputs a motor drive current to the turning electric motor 21 in accordance with a torque current command value from the controller 30.

  Each of the inverter 18 and the inverter 20 is mounted with an intelligent power module (IPM) incorporating a transistor constituting the inverter circuit.

  A resolver 22, a mechanical brake 23, and a turning speed reducer 24 are connected to the output shaft 21 </ b> A of the turning electric motor 21.

  The operation device 26 is a device for operating various actuators, and generates a pilot pressure corresponding to the operation content such as the operation amount and the operation direction. The operating device 26 is connected to the control valve 17 via a hydraulic line 27. The control valve 17 moves spool valves corresponding to various actuators in accordance with the pilot pressure generated by the operating device 26, and supplies hydraulic oil discharged from the main pump 14 to the various actuators. The operating device 26 is connected to a pressure sensor 29 via a hydraulic line 28. The pressure sensor 29 converts the pilot pressure generated by the operating device 26 into an electrical signal, and outputs the converted electrical signal to the controller 30.

  The ammeter M <b> 1 is a device that detects a current flowing between the inverter 20 and the turning electric motor 21, and outputs the detected value to the controller 30. Further, the ammeter M1 may output a detected value to another arithmetic processing device capable of executing current feedback control, current monitoring / checking, and the like. In addition, another arithmetic processing unit may be integrated with the inverter 20, for example, and may be comprised as a different body independent from the inverter 20.

  The controller 30 is a control device that performs drive control of the shovel. In this embodiment, the controller 30 is an arithmetic processing unit that includes a CPU and an internal memory. Specifically, the arithmetic processing unit realizes various functions by causing the CPU to execute a drive control program stored in an internal memory.

  FIG. 3 includes a functional block diagram of the controller 30 and shows functional elements used when drive control of the turning electric motor 21 is performed. In the present embodiment, the controller 30 mainly includes a speed command generator 31, a speed limiter 32, a subtractor 33, a PI controller 34, a torque limiter 35, a load factor calculator 36, an acceleration torque limit generator 37, And a speed limit generation unit 38.

  The speed command generation unit 31 generates a speed command value based on an electrical signal from the pressure sensor 29 that represents the lever operation amount of the turning operation lever.

  The speed limiter 32 limits the speed command value below the speed limit value using the speed limit value. In this embodiment, the speed limiter 32 outputs the speed limit value to the subtracter 33 as a speed command value if the speed command value generated by the speed command generator 31 is equal to or greater than the speed limit value. Further, if the speed command value generated by the speed command generation unit 31 is less than the speed limit value, the speed limit unit 32 outputs the speed command value to the subtractor 33 as it is.

  The subtractor 33 outputs a deviation between the speed command value and the current value of the turning speed (actual turning speed) to the PI control unit 34. The actual turning speed is derived from the detection value of the resolver 22 as a turning speed detector, for example. Specifically, the controller 30 derives the actual turning speed based on the change in the rotational position of the turning electric motor 21.

  The PI control unit 34 performs PI control based on the deviation input from the subtractor 33. In the present embodiment, the PI control unit 34 generates a torque current command value so that the actual turning speed approaches the speed command value. Then, the PI control unit 34 outputs the generated torque current command value to the torque limiting unit 35.

  The torque limiter 35 limits the torque current command value below the torque limit value using the torque limit value (including the acceleration torque limit value). In this embodiment, the torque limiter 35 adopts the torque limit value as the torque current command value if the torque current command value is equal to or greater than the torque limit value. Further, if the torque current command value is less than the torque limit value, the torque limiter 35 adopts the torque current command value as it is. Then, the torque limiter 35 outputs the adopted torque current command value to the inverter 20.

  Receiving the torque current command value, the inverter 20 generates a PWM signal according to the torque current command value, and controls a switching element such as a transistor with the generated PWM signal. Further, the inverter 20 may feedback control the torque current command value so as to minimize the deviation between the torque current command value and the current value of the torque current. In this case, the current value of the torque current is a value detected by the ammeter M1, for example.

  The load factor calculation unit 36 calculates the load factor of the turning drive system including the inverter 20 and the turning electric motor 21. In addition, the load factor calculation unit 36 calculates the load factor so that the load factor increases as the temperature of the turning drive system increases. For example, the load factor calculation unit 36 calculates the load factor so that the higher the IPM temperature of the inverter 20 or the higher the temperature of the turning electric motor 21, the higher the load factor. In the present embodiment, the load factor calculation unit 36 calculates the load factor based on the detection value of the ammeter M1. This is because it is estimated that the temperature of the swing drive system increases as the current flowing between the inverter 20 and the swing motor 21 increases. Specifically, the load factor calculation unit 36 integrates the calorific value corresponding to the current value detected by the ammeter M1 for each predetermined control cycle over the most recent predetermined period, and derives the calorific value integrated value in the predetermined period. . In addition, the load factor calculation unit 36 derives the current load factor by subtracting a value (cooling heat amount integrated value) corresponding to the cooling capacity of the cooling circuit in the most recent predetermined period from the heat generation amount integrated value. Note that the cooling heat integrated value may be a value stored in advance, or dynamically based on the output of various sensors that detect the discharge amount of the cooling water pump that constitutes the cooling circuit, the temperature of the cooling water, and the like. It may be derived. In this case, when the state where the magnitude of the instantaneous value of the calorific value corresponding to the detection value of the ammeter M1 is less than the magnitude of the instantaneous value of the cooling heat amount by the cooling circuit continues, the load factor decreases with time. In this way, the load factor calculation unit 36 derives the load factor for each predetermined control cycle, and outputs the load factor to each of the acceleration torque limit generation unit 37 and the speed limit generation unit 38.

  Further, the load factor calculating unit 36 may derive the load factor as an integral value of a value obtained by subtracting a rated current value (a current value that generates an amount of heat corresponding to the cooling capacity of the cooling circuit) from the detected value of the ammeter M1. .

  Further, the load factor calculating unit 36 may measure the temperature of at least one of the inverter 20 and the turning electric motor 21 with a temperature sensor (not shown) and may calculate the load factor based on the measured value, and the measured value may be used as it is. It may be a load factor. Originally, the integrated value of the current flowing through the turning motor 21 or the integrated value of the calorific value corresponding to the current value is the temperature of the turning drive system (for example, the temperature of at least one of the inverter 20 and the turning electric motor 21). This is to estimate the temperature when it cannot be measured properly.

  Further, the load factor calculation unit 36 calculates a plurality of load factors based on the detected value of the ammeter M1 (motor driving current) and the measured value of the temperature sensor (the temperature of the inverter 20 or the turning electric motor 21), A statistical value (for example, maximum value, minimum value, average value) of the plurality of load factors may be adopted as the final load factor.

  If the controller 30 determines that the load factor calculated by the load factor calculation unit 36 exceeds a predetermined overload level, the controller 30 outputs an off command to the inverter 20 to stop the output of the inverter 20, and A brake command is output to the mechanical brake 23 to generate a braking force by the mechanical brake 23. As a result, regardless of whether or not the turning electric motor 21 is turning, the supply of current from the inverter 20 is forcibly cut off and is forcibly stopped by the mechanical brake 23.

  The acceleration torque limit generation unit 37 generates an acceleration torque limit value that limits the acceleration torque to increase (accelerate) the turning speed of the upper swing body 3. In the present embodiment, the acceleration torque limit generation unit 37 generates an acceleration torque limit value according to the load factor calculated by the load factor calculation unit 36, and outputs the generated acceleration torque limit value to the torque limit unit 35. .

  Further, the acceleration torque limit generation unit 37 is calculated by the load factor calculation unit 36 based on the detected value (motor drive current) of the ammeter M1 and the measured value of the temperature sensor (temperature of the inverter 20 or the turning electric motor 21). A plurality of acceleration torque limit values are generated according to each of the load factors, and a statistical value (for example, maximum value, minimum value, average value) of the plurality of acceleration torque limit values is adopted as a final acceleration torque limit value. May be.

  The acceleration torque limit value limits the acceleration torque that increases (accelerates) the turning speed of the upper swing body 3, and decelerates to reduce (decelerate) the swing speed of the upper swing body 3. The torque is not limited, and the holding torque that prevents the upper swing body 3 from rotating is not limited. Therefore, only when acceleration torque is generated, the controller 30 causes the torque limit unit 35 to limit the torque current command value with an acceleration torque limit value less than a predetermined acceleration torque limit standard value.

  Specifically, the controller 30 outputs the acceleration torque limit value from the acceleration torque limit generation unit 37 to the torque limit unit 35 only when it is determined that the acceleration torque is generated. For example, the controller 30 determines whether or not acceleration torque is generated based on the actual turning speed and the speed command value. Here, it is assumed that the actual turning speed and the speed command value are both positive when turning right and negative when turning left. In this case, the controller 30 determines that acceleration torque is generated when the sign of the actual turning speed is the same as the sign of the speed command value and the actual turning speed is closer to zero than the speed command value.

  Instead of outputting the acceleration torque limit value to the acceleration torque limit generation unit 37 only when it is determined that acceleration torque is generated, the controller 30 causes the torque limit unit 35 to execute acceleration torque only when it is determined that acceleration torque is generated. A limit value may be received.

  When the controller 30 determines that no acceleration torque is generated, for example, when deceleration torque or holding torque is generated, the controller 30 sets the torque current command value with a torque limit value set regardless of the variation of the load factor. You may restrict.

  Here, the acceleration torque limit value generated by the acceleration torque limit generation unit 37 will be described with reference to FIG. FIG. 4 is a graph showing an example of a reference table that defines the relationship between the acceleration torque limit value and the load factor.

  As shown in FIG. 4, the acceleration torque limit value is a value LVs in which the load factor value calculated by the load factor calculator 36 is determined as a predetermined limit start level (hereinafter referred to as “limit start level LVs”). Until reaching the predetermined value TL1. The predetermined value TL1 is an upper limit value determined according to the specifications of the turning drive system in order to prevent damage to the turning drive system. Therefore, depending on the magnitude of the predetermined value TL1, even if the load factor is less than the limit start level LVs, the acceleration torque limit value does not necessarily have to be kept constant. The acceleration torque limit value decreases at a constant rate according to the load factor when the load factor exceeds the limit start level LVs, and the load factor is a value LVe (hereinafter referred to as “overload”) determined as a predetermined overload level. Level LVe "), the predetermined value TL2 is reached. The controller 30 forcibly stops the turning electric motor 21 when the load factor reaches the overload level LVe.

  In this way, the acceleration torque limit generation unit 37 derives an acceleration torque limit value corresponding to the current load factor using a reference table stored in advance in an internal memory or the like. The acceleration torque limit value does not necessarily need to be reduced at a constant rate according to the load factor, and may be reduced stepwise or may be reduced nonlinearly.

  Further, the limitation of the acceleration torque has an effect of suppressing the motor drive current flowing from the inverter 20 to the turning electric motor 21. As a result, it is possible to suppress or prevent the load factor from reaching the overload level LVe by suppressing the heat generation amount of the turning drive system.

  With this configuration, the controller 30 can prevent deterioration of the operation feeling related to turning by suppressing or preventing the acceleration torque from rapidly decreasing as soon as the load factor reaches the overload level LVe. In addition, the controller 30 prevents the torque reduction of the turning electric motor 21 from being limited, so that the torque current command value is limited by the acceleration torque limit value only when it is determined that the acceleration torque is generated. , It is possible to prevent the turning stop from being delayed.

  The speed limit generation unit 38 generates a speed limit value as an allowable maximum value of the turning speed of the upper swing body 3. In the present embodiment, the speed limit generation unit 38 generates a speed limit value according to the load factor calculated by the load factor calculation unit 36, and outputs the generated speed limit value to the speed limit unit 32.

  In addition, the speed limit generation unit 38 has a plurality of load factors that are calculated by the load factor calculation unit 36 based on the detection value (motor drive current) of the ammeter M1 and the measurement value of the temperature sensor (the temperature of the inverter 20 or the turning electric motor 21). A plurality of speed limit values may be generated according to each of the load factors, and statistical values (for example, maximum value, minimum value, average value) of the plurality of speed limit values may be adopted as the final speed limit value.

  Here, the speed limit value generated by the speed limit generation unit 38 will be described with reference to FIG. FIG. 5 is a graph showing an example of a reference table that defines the relationship between the speed limit value and the load factor.

  As shown in FIG. 5, the speed limit value remains constant at the predetermined value SL1 until the load factor value calculated by the load factor calculating unit 36 reaches a predetermined limit start level LVs. The predetermined value SL1 is an upper limit value determined in accordance with the specifications of the turning drive system in order to prevent damage to the turning drive system, similarly to the predetermined value TL1. Therefore, depending on the magnitude of the predetermined value SL1, even if the load factor is less than the limit start level LVs, the speed limit value does not necessarily change constantly. The speed limit value decreases at a constant rate according to the load factor when the load factor exceeds the limit start level LVs, and reaches a predetermined value SL2 when the load factor reaches a predetermined overload level LVe.

  In this manner, the speed limit generation unit 38 derives a speed limit value corresponding to the current load factor using a reference table stored in advance in an internal memory or the like. It should be noted that the speed limit value does not necessarily have to be reduced at a constant rate according to the load factor, and may be reduced stepwise or non-linearly.

  Further, the limitation of the allowable maximum value of the turning speed has an effect of suppressing the total deceleration torque (the integrated value of the deceleration torque from the start of deceleration to the stop) required to stop the turning of the upper swing body 3. This is because the total deceleration torque increases as the turning speed at the start of deceleration increases. As a result, it is possible to suppress or prevent the load factor from reaching the overload level LVe by suppressing the amount of heat generated by the swing drive system when stopping the swing of the upper swing body 3.

  With the above configuration, the controller 30 can more reliably suppress or prevent the load factor from reaching the overload level LV2 by using both the limitation of the acceleration torque and the limitation of the turning speed. Limiting the acceleration torque does not prevent the turning speed of the upper swing body 3 from reaching the predetermined value SL1, and the load factor reaches the overload level LV2 when stopping the upper swing body 3 turning at the predetermined value SL1. This is because a situation may occur. Further, it is not possible to prevent the turning speed of the upper turning body 3 from rapidly accelerating only by limiting the turning speed, and a situation occurs in which the load factor reaches the overload level LV2 when the upper turning body 3 accelerates rapidly. To get. However, the present invention does not exclude the configuration that limits only the acceleration torque and the configuration that limits only the turning speed.

  Next, a process in which the controller 30 restricts the drive of the turning electric motor 21 in accordance with the load factor of the turning drive system (hereinafter referred to as “turn restriction process”) will be described with reference to FIG. FIG. 6 is a flowchart showing the flow of the turning restriction process, and the controller 30 repeatedly executes this turning restriction process at a predetermined control cycle.

  First, the load factor calculation unit 36 of the controller 30 calculates the load factor of the turning drive system (step S1). In the present embodiment, the load factor calculation unit 36 calculates the load factor of the turning drive system based on the detection value of the ammeter M1.

  Thereafter, the controller 30 determines whether or not the load factor calculated by the load factor calculator 36 is less than the overload level LVe (step S2).

  When it is determined that the load factor is less than the overload level LVe (YES in step S2), the controller 30 determines whether the load factor is equal to or higher than a predetermined limit start level LVs (step S3).

  When it is determined that the load factor is equal to or higher than the limit start level LVs (YES in step S3), the speed limit generation unit 38 of the controller 30 reduces the speed limit value (step S4). In the present embodiment, the speed limit generation unit 38 refers to a reference table (see FIG. 5) stored in advance in the internal memory, and sets a speed limit value corresponding to the current load factor calculated by the load factor calculation unit 36. derive. Then, the speed limit generation unit 38 outputs the speed limit value smaller than the speed limit standard value SL1 to the speed limit unit 32. As a result, the speed command value generated by the speed command generation unit 31 according to the lever operation amount of the turning operation lever is limited to the speed limit value or less.

  Thereafter, the controller 30 determines whether or not acceleration torque is generated (step S5). In this embodiment, the controller 30 determines that acceleration torque is generated when the sign of the actual turning speed is the same as the sign of the speed command value and the actual turning speed is closer to zero than the speed command value.

  If it is determined that acceleration torque is generated (YES in step S5), the acceleration torque limit generation unit 37 of the controller 30 reduces the acceleration torque limit value (step S6). In this embodiment, the acceleration torque limit generation unit 37 refers to a reference table (see FIG. 4) stored in advance in the internal memory, and the acceleration torque limit corresponding to the current load factor calculated by the load factor calculation unit 36. Derive a value. Then, the acceleration torque limit generation unit 37 outputs the acceleration torque limit value smaller than the acceleration torque limit standard value TL1 to the torque limit unit 35. As a result, the torque current command value generated by the PI control unit 34 is limited to the acceleration torque limit value or less.

  Further, when the acceleration torque limit generation unit 37 reduces the acceleration torque limit value, the controller 30 notifies the operator of the shovel to that effect (step S7). In this embodiment, the controller 30 outputs a control command to an output device (not shown) such as a vehicle-mounted speaker or a vehicle-mounted display. Then, a voice message, text message, buzzer or the like indicating that the acceleration torque limit value has been reduced is output to notify the operator that the acceleration torque limit value has been reduced. The operator who has received the notification recognizes that the load factor is increasing at an early stage, and can move the shovel to an appropriate state before the load factor increases excessively. Note that the controller 30 may notify the operator that the speed limit generation unit 38 has reduced the speed limit value.

  On the other hand, if it is determined that no acceleration torque is generated (NO in step S5), the controller 30 operates the turning drive system without reducing the torque limit value below the predetermined torque limit standard value, and the desired deceleration torque or holding Torque is output. That is, the controller 30 does not limit the deceleration torque and the holding torque to less than the predetermined torque limit standard value even when it is determined that the load factor is equal to or higher than the limit start level LVs. Note that the torque limit standard value in this case means a value adopted during turning deceleration or holding turning regardless of the load factor.

  If it is determined that the load factor is less than the limit start level LVs (NO in step S3), the controller 30 does not reduce the speed limit value to less than the speed limit standard value SL1, and also sets the acceleration torque limit value. The turning drive system is operated without being reduced below the acceleration torque limit standard value TL1 so that a desired turning torque is output.

  If it is determined that the load factor is equal to or higher than the overload level LVe (NO in step S2), the controller 30 forcibly stops the turning of the upper swing body 3 (step S8). In the present embodiment, the controller 30 stops the turning electric motor 21 and generates a braking force by the mechanical brake 23.

  In the above-described turning limit process, the torque limit value is determined after the speed limit value is determined. However, the speed limit value may be determined after the torque limit value is determined. The limit value may be determined concurrently.

  Next, with reference to FIG. 7, the temporal transition of various physical quantities when the excavator performs the turning pressing work will be described. FIG. 7 is a graph showing temporal transitions of various physical quantities when the excavator performs the turning pressing work. Specifically, FIGS. 7A1 to 7D1 show temporal transitions of various physical quantities when the controller 30 does not execute the turning restriction process, and FIGS. 7A2 to 7D2 are controllers. 30 shows the time transition of various physical quantities when the turning restriction process is executed. 7 (A1) and 7 (A2) show the temporal transition of the lever operation amount of the turning operation lever, and FIGS. 7 (B1) and 7 (B2) show the speed command value / actual turning speed over time. Shows the transition. 7 (C1) and FIG. 7 (C2) show the temporal transition of the torque current command value, and FIG. 7 (D1) and FIG. 7 (D2) show the temporal transition of the load factor. Note that the temporal transition of the lever operation amount shown in each of FIGS. 7A1 and 7A2 is the same regardless of whether or not the turning restriction process is executed.

  First, with reference to FIG. 7A1 to FIG. 7D1, time transitions of various physical quantities when the controller 30 does not execute the turning restriction process during the turning pressing operation will be described.

  When the turning operation lever is tilted at time t1 as indicated by the solid line in FIG. 7A1, the speed command value starts increasing at time t1 as indicated by the solid line in FIG. 7B1, and the speed command value is increased at time t2. The limit standard value SL1 is reached. On the other hand, the actual turning speed slightly increases between time t1 and time t2 as indicated by the dotted line in FIG. 7B1, but thereafter remains substantially zero. This is because the upper turning body 3 does not turn even if turning torque is generated due to the turning pressing work. Therefore, the deviation D between the speed command value and the actual turning speed changes while maintaining a relatively large value.

  As shown by the solid line in FIG. 7 (C1), the torque current command value starts increasing at time t1, and reaches the acceleration torque limit standard value TL1 at time t2. Further, since the deviation D between the speed command value and the actual turning speed is a relatively large value after time t2, the torque current command value remains the acceleration torque limit standard value TL1. That is, the inverter 20 continues to supply a relatively large motor drive current to the turning electric motor 21.

  As indicated by the solid line in FIG. 7 (D1), the load factor rises slightly after the rise of the speed command value and the torque current command value, and continues to increase because the supply of motor drive current continues thereafter. Then, the load factor reaches the overload level LVe at time t3.

  When the load factor reaches the overload level LVe, the controller 30 sets the speed command value and the torque current command value to zero, and stops the supply of motor drive current to the turning electric motor 21 by the inverter 20.

  As described above, when the turning restriction process is not executed during the turning pressing operation, the controller 30 forcibly drives the turning electric motor 21 to protect the turning drive system when the load factor reaches the overload level LVe. The upper revolving unit 3 is prevented from turning by the mechanical brake 23. Therefore, the operator cannot turn the upper turning body 3 until the temperature of the turning drive system drops below a predetermined temperature.

  Next, with reference to FIG. 7 (A2) to FIG. 7 (D2), the temporal transition of various physical quantities when the controller 30 executes the turning restriction process during the turning pressing operation will be described. Note that the temporal transition of various physical quantities up to time t2 is the same as the temporal transition shown in FIG. 7A1 to FIG.

  When executing the turning restriction process, the controller 30 determines whether or not acceleration torque is generated when the load factor reaches the restriction start level LVs at time t10 as shown by the solid line in FIG. 7 (D2). In this case, as shown in FIG. 7 (B2), the controller 30 has the same acceleration / deceleration torque because the sign of the speed command value is the same as the sign of the actual turning speed and the actual turning speed is closer to zero than the speed command value. Determine that it occurs. Then, as shown by the solid line in FIG. 7 (C2), the controller 30 reduces the acceleration torque limit value to be less than the acceleration torque limit standard value TL1. The reduction in the acceleration torque limit value results in a reduction in the motor drive current related to the turning electric motor 21. Therefore, the effect of suppressing the temperature rise of each of the inverter 20 and the turning electric motor 21, that is, the effect of suppressing the increase of the load factor is brought about. Note that the load factor does not decrease as long as the amount of heat generated by the motor drive current exceeds the amount of cooling heat generated by the cooling circuit. Therefore, the acceleration torque limit value gradually decreases while decreasing the decrease rate with respect to time as shown by the solid line in FIG. 7 (C2). On the other hand, the load factor gradually increases while decreasing the increase rate with respect to time as shown by the solid line in FIG. 7 (D2).

  With this configuration, the controller 30 gradually (continuously) the torque current command value output to the inverter 20 along the acceleration torque limit value even if the turning operation lever continues to be operated with the same lever operation amount. Can be reduced. Therefore, it is possible to prevent the torque current command value from being suddenly reduced as when the load factor reaches the overload level LVe when the turning restriction process is not executed. As a result, it is possible to prevent the operator from feeling uncomfortable by generating a shock due to a sudden change in the acceleration torque.

  Further, the controller 30 can suppress or prevent the load factor from reaching the overload level LVe by decreasing the acceleration torque limit value according to the increase in the load factor. Therefore, when the turning restriction process is not executed, a situation occurs in which the turning electric motor 21 is forcibly stopped and continuous operation of the shovel becomes impossible as when the load factor reaches the overload level LVe. Can be suppressed or prevented.

  Similarly, when the load factor reaches the limit start level LVs at time t10 as shown by the solid line in FIG. 7 (D2), the controller 30 changes the speed limit value to the speed limit standard as shown by the solid line in FIG. 7 (B2). Reduce to less than value SL1. Further, the speed limit value decreases as the load factor increases. Specifically, as shown by the solid line in FIG. 7 (B2), the rate of decrease gradually decreases while decreasing with respect to time.

  With this configuration, the controller 30 can limit the allowable maximum turning speed of the upper swing body 3 and can suppress or prevent the total deceleration torque necessary for stopping the upper swing body 3 from becoming excessively large. . Therefore, the turning of the upper-part turning body 3 can be stopped while preventing the load factor from reaching the overload level LVe during the turning deceleration without restricting the deceleration torque as when the acceleration torque is restricted. . Further, since the deceleration torque is not limited, it is possible to prevent the turning angle until the turning of the upper turning body 3 is stopped from becoming excessively large. When the load factor reaches the overload level LVe as a result of trying to stop the turning of the upper turning body 3 without limiting the deceleration torque, the controller 30 operates the mechanical brake 23 to turn the upper turning body. The turning of the body 3 is mechanically stopped.

  Next, the relationship among the turning angular velocity ω, turning energy E, and turning torque τ of the turning electric motor 21 will be described with reference to FIG. FIG. 8 is a diagram showing temporal transitions of the turning angular velocity ω, the turning energy E, and the turning torque τ when the upper turning body 3 is turned and stopped. Specifically, FIG. 8A shows the temporal transition of the turning angular velocity ω of the turning electric motor 21, FIG. 8B shows the temporal transition of the turning energy E, and FIG. 8C shows the turning torque. The time transition of τ is shown. Moreover, the transition shown by the solid line in FIG. 8 indicates the transition of various physical quantities when the turning restriction process is not executed. Further, the transition indicated by the broken line in FIG. 8 indicates that the speed limit value is reduced to less than the speed limit standard value SL1 by the turn limit process when the turn limit process is executed, and the acceleration torque limit value is the acceleration torque limit. The transition of various physical quantities when reduced to less than the standard value TL1 is shown.

Further, the turning energy E and the turning torque τ are expressed by the following equations. J represents the moment of inertia of the upper swing body 3. Further, τ ₀ (ω) represents a turning torque necessary to maintain a constant turning angular velocity ω against friction loss and the like, and is larger as the turning angular velocity ω of the turning electric motor 21 to be maintained is larger.

旋回制限処理が実行される場合、すなわち、速度制限値及び加速トルク制限値が標準値未満に低減される場合、時刻ｔａにおいて旋回操作レバーが操作されると、図８（Ｃ）の破線で示すように、旋回トルク（加速トルク）τは時刻ｔａで増大し始め、時刻ｔｂで現在の加速トルク制限値に対応する値τ２となるまで増大する。その後、時刻ｔｄで旋回角速度ωが現在の速度制限値に対応する値ω２に達するまで（図８（Ａ）の破線参照。）、旋回トルク（加速トルク）τは値τ２のまま推移する。旋回トルク（加速トルク）τが値τ２のまま推移する時刻ｔｂから時刻ｔｄまでの期間では、上述の（２）式から分かるように、旋回角速度ωは一定の旋回角加速度で増大する。

When the turning restriction process is executed, that is, when the speed restriction value and the acceleration torque restriction value are reduced to less than the standard value, when the turning operation lever is operated at time ta, it is indicated by a broken line in FIG. Thus, the turning torque (acceleration torque) τ starts to increase at time ta and increases at time tb until it reaches a value τ2 corresponding to the current acceleration torque limit value. Thereafter, the turning torque (acceleration torque) τ remains at the value τ2 until the turning angular velocity ω reaches the value ω2 corresponding to the current speed limit value at time td (see the broken line in FIG. 8A). In the period from the time tb to the time td when the turning torque (acceleration torque) τ remains at the value τ2, the turning angular velocity ω increases at a constant turning angular acceleration, as can be seen from the above equation (2).

When the turning angular velocity ω reaches the value ω2 at time td, the turning torque (acceleration torque) τ is reduced to the minimum value τ3b (= τ ₀ (ω2)) necessary to maintain the current turning angular velocity ω2. (See equation (2).)

  Thereafter, the turning torque (deceleration torque) τ is set to a value τ4 corresponding to the deceleration torque limit standard value at time tg in order to stop the turning of the upper-part turning body 3 at time th. Therefore, the turning angular velocity ω starts to decrease at time tg and reaches a value of zero at time th.

  On the other hand, when the turning restriction process is not executed, when the turning operation lever is operated at time ta, turning torque (acceleration torque) τ starts to increase at time ta as shown by the solid line in FIG. It increases until it reaches a value τ1 corresponding to the acceleration torque limit standard value TL1 at tc. Thereafter, until the turning angular velocity ω reaches a value ω1 corresponding to the speed limit standard value SL1 at time te (see the solid line in FIG. 8A), the turning torque (acceleration torque) τ remains at the value τ1. In the period from time tc to time te when the turning torque (acceleration torque) τ remains at the value τ1, the turning angular velocity ω increases at a constant turning angular acceleration, as can be seen from the above equation (2).

When the turning angular velocity ω reaches the value ω1 at time te, the turning torque (acceleration torque) τ is a minimum value τ3a (= τ ₀ (ω1)> τ3b (= τ) required to maintain the current turning angular velocity ω1. ₀ (ω2))) (see equation (2)).

  Thereafter, the turning torque (deceleration torque) τ is set to a value τ4 corresponding to the deceleration torque limit standard value at time tf in order to stop turning of the upper-part turning body 3 at time th. Therefore, the turning angular velocity ω starts to decrease at time tf and reaches a value of zero at time th.

  Here, when the case where the turning restriction process is executed is compared with the case where it is not executed, the maximum value of the turning angular velocity ω is restricted to about two thirds (≈ω2 / ω1) as shown in FIG. Thus, as shown in FIG. 8B, the maximum value of the turning energy E is limited to about one half (≈E2 / E1). As a result, as shown in FIG. It can be seen that D1 is shortened to D2.

  With the above configuration, the controller 30 reduces the upper limit of the acceleration torque of the turning electric motor 21 as the temperature of at least one of the turning electric motor 21 and the inverter 20 is higher. Specifically, the acceleration torque limit value is reduced as the temperature of at least one of the turning electric motor 21 and the inverter 20 increases, that is, as the load factor of the turning drive system increases. Therefore, the controller 30 can moderate the increase in the load factor even when the load factor continuously increases due to the turning pressing work or the like. Further, the controller 30 can gently reduce the torque current command value, and can more appropriately limit the turning torque of the turning electric motor 21 while preventing a shock caused by a sudden decrease in the acceleration torque.

  Further, the controller 30 calculates a load factor that increases as the temperature of at least one of the turning electric motor 21 and the inverter 20 rises, and reduces the upper limit of the acceleration torque of the turning electric motor 21 according to the increase in the load factor. . Then, as the acceleration torque of the turning electric motor 21 continues at the upper limit, the rate of increase of the load factor with respect to time is gradually decreased. Therefore, it is possible to suppress or prevent the load factor from reaching the overload level.

  The temperature of at least one of the turning electric motor 21 and the inverter 20 is estimated from the integrated value of the current flowing through the turning electric motor 21. Therefore, the controller 30 can estimate the temperature of the turning electric motor 21 and the inverter 20 from the integrated value of the motor drive current related to the turning electric motor 21 without directly measuring the temperature of the electric turning motor 21 and the inverter 20. Therefore, the turning torque of the turning electric motor 21 can be appropriately limited.

  Further, the controller 30 reduces the allowable maximum turning speed of the turning electric motor 21 as the temperature of at least one of the turning electric motor 21 and the inverter 20 is higher. Therefore, the controller 30 can suppress the total deceleration torque when stopping the upper swing body 3 that is turning at the allowable maximum turning speed. As a result, the controller 30 can appropriately stop the upper-part turning body 3 while suppressing or preventing the load factor from reaching the overload level during turning deceleration without limiting the deceleration torque.

  In addition, the controller 30 can prevent the overheating of the turning electric motor 21 by limiting the acceleration torque during the turning pressing work, and the upper turning body 3 can be moved when the turning load such as earth and sand is pushed away and the turning load is suddenly reduced. Rapid acceleration can be prevented. In addition, since the turning speed is limited, the controller 30 can prevent the turning speed of the upper turning body 3 from becoming excessively high when the object to be pressed such as earth and sand is pushed away and the turning load is suddenly reduced.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the controller 30 includes the speed limit generation unit 38, but the speed limit generation unit 38 may be omitted. In this case, as in the case where it is determined that no acceleration torque is generated in the above-described embodiment, the speed limiter 32 uses the speed limit value set regardless of the variation of the load factor to set the speed command value to the speed command value. You may restrict | limit to a limit value or less.

  DESCRIPTION OF SYMBOLS 1 ... Lower traveling body 2A, 2B ... Traveling hydraulic motor 2 ... Turning mechanism 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom Cylinder 8 ... Arm cylinder 9 ... Bucket cylinder 10 ... Cabin 11 ... Engine 12 ... Motor generator 13 ... Reduction gear 14 ... Main pump 15 ... Pilot pump 16 ..High pressure hydraulic line 17 ... Control valve 18 ... Inverter 19 ... Power storage device 19a ... Buck-boost converter 19b ... DC bus 20 ... Inverter 21 ... Turning electric motor 21A ... -Output shaft 22 ... Resolver 23 ... Mechanical brake 24 ... Turning speed reducer 25 ... Pilot line 26 ... Operating device 2 28 ... Hydraulic line 29 ... Pressure sensor 30 ... Controller 31 ... Speed command generator 32 ... Speed limiter 33 ... Subtractor 34 ... PI controller 35 ... Torque limiter 36 ... load factor calculator 37 ... acceleration torque limit generator 38 ... speed limit generator 120 ... power storage system M1 ... ammeter

Claims (4)

A lower traveling body,
An upper swing body mounted on the lower traveling body;
A turning electric motor for turning the upper turning body;
An inverter that drives the electric motor for turning;
A controller for controlling the inverter,
The controller reduces the upper limit of the acceleration torque of the turning motor as the temperature of at least one of the turning motor and the inverter is higher.
Construction machinery. The controller calculates a load factor that increases as the temperature of at least one of the turning motor and the inverter rises, and reduces the upper limit of the acceleration torque of the turning motor according to the increase in the load factor. , The rate of increase of the load factor with respect to time decreases gradually as the acceleration torque of the turning electric motor continues at the upper limit.
The construction machine according to claim 1. The temperature of at least one of the turning motor and the inverter is estimated from an integrated value of a current flowing through the turning motor.
The construction machine according to claim 1 or 2. The controller reduces the allowable maximum turning speed of the turning electric motor as the temperature of at least one of the turning electric motor and the inverter is higher.
The construction machine according to any one of claims 1 to 3.

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