JP2010095906A - Construction machine and slewing controlling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the sharply accelerated slewing of an upper slewing body gives an operator an unpleasant feeling and causes load collapse to invite a dangerous situation when an unstable load, such as earth and sand, is moved. <P>SOLUTION: A first conversion table 61 defines the relation between an elapsed time from a time of operation of an operating device 52 and a limit torque 1 for an electric motor 25. A second conversion table 62 defines the relation between slewing operation quantity information output from the operating device 52 and a limit torque 2 for the electric motor 25. A third conversion table 63 defines the relation between slewing operation quantity information output from the operating device 52 and a target rotating speed of the electric motor 25. A minimum selecting circuit 64 receives input of the limit torques 1 and 2 and a target torque to select the minimum of the absolute values of these three torques as a torque limit value, and supplies a torque limit value control signal 100 to a slewing inverter 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a construction machine that drives an upper turning body mounted on a lower traveling body to turn by an electric motor, and a turning control device for the construction machine.

2. Description of the Related Art Conventionally, a construction machine is known in which an upper swing body placed on a lower traveling body is driven to rotate by an electric motor. When supplying the rotation speed control signal and the torque control signal to the inverter that controls the electric motor, the target rotation speed and the limit torque are obtained based on the operation signal corresponding to the operation amount of the operation lever. For example, the absolute value is obtained by comparing the torque value obtained by feedback control from the deviation between the target rotational speed of the motor and the actual rotational speed with a limit torque value that is defined in advance corresponding to the operation amount of the operation lever. It is known that a torque value having a smaller value is instructed to an inverter as a torque limit value (Patent Document 1).
JP 2006-112114 A

However, since the torque limit value of the motor is uniquely determined according to the operation amount of the operation lever and the feedback control amount, the maximum torque is set in a large operation amount range exceeding the set acceleration section. become.
As a result, for example, when the operator operates the operating lever stepwise to the maximum degree with the intention of the maximum turning speed, the stepped maximum torque is generated at the same timing as that operation, and the sudden acceleration turning is performed. In addition, there is a problem that when an unstable load such as earth and sand is moved, a spillage occurs and it becomes a dangerous state.

The construction machine according to claim 1 is a construction machine that drives an upper swing body mounted on a lower traveling body to rotate by an electric motor, and an operation unit that outputs a swing operation signal for rotating the upper swing body; A first torque setting unit that sets a maximum value of a driving torque generated by the electric motor according to an elapsed time after the turning operation signal is output; and an electric motor that is determined in advance corresponding to the turning operation signal. Based on the deviation between the rotational speed and the actual rotational speed of the electric motor, a second torque setting unit that sets a target torque value of the electric motor, and the maximum value of the driving torque set by the first torque setting unit And a torque limit value designating unit for designating a torque limit value of the electric motor by referring to the target torque value set by the second torque setting unit, and corresponding to the turning operation signal A rotational speed designating unit that designates a predetermined motor rotational speed as the target rotational speed of the motor, the torque limit value designating unit, the torque limit value designated by the rotational speed designating unit, and the target rotational speed. And a motor control unit that drives the motor.
A turning control device according to claim 5 is issued in response to an operation of an operation lever for turning the upper turning body in a turning control device for a construction machine that turns the upper turning body using an electric motor controlled by an inverter. An operation signal input means for inputting a turning operation signal; a first torque setting means for setting a maximum value of a driving torque generated by the electric motor according to an elapsed time after the turning operation signal is inputted; A second torque setting means for setting a target torque value of the motor based on a deviation between a predetermined motor rotation speed corresponding to a turning operation signal and an actual rotation speed of the motor; The electric motor using the maximum value of the driving torque set by the torque setting means and the target torque value set by the second torque setting means as reference data Torque limit value designating means for designating a torque limit value, rotation speed designating means for designating a predetermined motor rotation speed corresponding to the turning operation signal as a target rotation speed of the motor, and the torque limit value designating And an output means for supplying the torque limit value and the target rotational speed designated by the rotational speed designation means to a control input terminal of the inverter.

  According to the present invention, when setting the torque limit value of the electric motor that turns the upper turning body, the maximum value of the turning torque is defined according to the elapsed time after the turning operation signal is output. Even if the turning operation is performed rapidly, it is possible to perform rotation control so that an excessive turning shock does not occur in the upper turning body.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment 1>
FIG. 1 is an overall configuration diagram of a hydraulic excavator to which the present invention is applied. In this figure, the lower traveling body 10 includes a pair of crawlers 11 and a crawler frame 12 (only one side is shown in FIG. 1), and a pair of traveling hydraulic motors 13 and 14 that independently drive and control each crawler 11 (FIG. 2). And a speed reduction mechanism (not shown).

  The upper swing body 20 includes a swing frame 21, an engine 22 provided on the swing frame 21, a generator 23 driven by the engine 22, a battery 24 that stores electric power generated by the generator, and a generator 23. Alternatively, the motor includes a turning electric motor 25 driven by electric power from the battery 24 and a speed reduction mechanism (not shown) that decelerates the rotation of the turning electric motor 25. A turning mechanism 26 for turning the turning body 20 (turning frame 21) is provided. The turning speed of the upper turning body 20 is proportional to the rotation speed of the turning electric motor 25.

  The upper swing body 20 has a boom 31 that can be raised and lowered, a boom cylinder 32 that drives the boom 31, an arm 33 that is rotatably supported near the tip of the boom 31, and an arm 33 that is driven. An excavator mechanism (hereinafter referred to as an articulated front working unit) 30 including an arm cylinder 34, a bucket 35 rotatably supported at the tip of the arm 33, and a bucket cylinder 36 for driving the bucket 35. Is installed. Furthermore, on the swing frame 21 of the upper swing body 20, a hydraulic pump 41 (see FIG. 2) for driving and controlling the boom cylinder 32, the arm cylinder 34, and the bucket cylinder 36, and a hydraulic control valve provided for each cylinder A hydraulic control system 40 (see FIG. 2) having 42 (see FIG. 2) is mounted.

  The operating device 52 includes an operation lever that can be tilted leftward, neutrally, and rightward to allow the upper swing body 20 to turn left, neutral, and right. A turning operation amount signal corresponding to the operation amount of the operation lever is output from the operation device 52.

  FIG. 2 is a block diagram showing a power transmission path of the hydraulic excavator shown in FIG. In this figure, a thick line indicates a mechanical drive system, a middle line indicates a hydraulic drive system, a thin line indicates an electrical drive system, and a broken line indicates a control signal system. As shown in the figure, the driving force of the engine 22 is transmitted to the hydraulic pump 41. The hydraulic control valve 42 discharges operating oil to the boom cylinder 32, the arm cylinder 34, the bucket cylinder 36, the left traveling hydraulic motor 13, and the right traveling hydraulic motor 14 in response to an operation command from an operation control unit (not shown). Volume control and discharge direction control are performed.

  The driving force of the engine 22 is transmitted to the generator 23 via the speed increasing mechanism 29. The generator 23 generates a predetermined AC voltage, and the generated AC voltage is converted into a DC voltage by the converter 27 and stored in the battery 24. The DC voltage from the converter 27 or the battery 24 is supplied to the inverter 28. The inverter 28 supplies a pulse signal having a predetermined voltage and frequency to the turning electric motor 25. When the electric motor 25 is decelerated, the electric power regenerated by the electric motor 25 is stored in the battery 24. The converter 27 controls the power generation amount of the generator 23 according to the control signal output from the control device 51.

  The turning inverter 28 receives the torque limit value control signal 100 and the target rotational speed control signal 200 (described later in detail) output from the control device 51, and controls the driving torque and rotational speed of the turning electric motor 25. The type and rating of the turning electric motor 25 are appropriately selected according to the application.

  Reference numeral 53 denotes a rotation speed sensor that detects the rotation speed of the turning electric motor 25. The rotation speed of the turning electric motor 25 is detected by counting the number of pulses output from a pulse encoder (not shown) within a unit time. To do. The control device 51 inputs an actual rotation speed signal output from the rotation speed sensor 53 and a turning operation amount signal output from the operation device 52. Then, the torque control signal and the speed control signal (the limit value control signal 100 and the target rotation speed control signal 200) are supplied to the turning inverter 28 through signal processing described in detail later.

  FIG. 3 is a block diagram showing a circuit configuration of the control device 51. As described with reference to FIG. 2, the turning operation amount from the operation device 52 and the actual rotation speed from the rotation speed sensor 53 are input to the control device 51 as input information. The control device 51 includes three conversion tables 61, 62, and 63.

  The first conversion table 61 is an “elapsed time → restricted torque 1” conversion table that defines the relationship between the elapsed time after the operation device 52 is actuated and the limit torque 1 of the electric motor 25. The second conversion table 62 is a “swing operation amount → limit torque 2” conversion table that defines the relationship between the swing operation amount information output from the operation device 52 and the limit torque 2 of the electric motor 25. The third conversion table 62 is a “turning operation amount → target rotation speed” conversion table that defines the relationship between the turning operation amount information output from the operating device 52 and the target rotation speed of the electric motor 25.

More specifically, the “elapsed time → limit torque 1” conversion table 61 uses a turning operation input by the operation device 52 as a trigger, and a predetermined time set in advance according to the turning direction indicated by the turning operation input. Within the range, limit torque 1 proportional to the elapsed time from the start of operation input is output.
From the “turning operation amount → limiting torque 2” conversion table 62, the limiting torque 2 is output according to the turning operation amount. From the “turning operation amount → target rotation speed” conversion table 63, the target rotation speed is output according to the turning operation amount.

  The subtracter 65 calculates a deviation between the target rotation speed and the actual rotation speed. The calculated deviation is input to the PID controller 66, and the target torque is calculated. Since the calculation characteristics in the PID controller 66 are known design matters, the description thereof is omitted. The minimum value selection circuit 64 inputs the limit torque 1, the limit torque 2, and the target torque, and selects the torque that minimizes the absolute value of each torque as the torque limit value. Then, the torque limit value control signal 100 is supplied from the minimum value selection circuit 64 to the turning inverter 28. The target rotation speed from the “turning operation amount → target rotation speed” conversion table 63 is input to the subtractor 65 and is simultaneously supplied to the turning inverter 28 as the target rotation speed control signal 200.

  If a first-order lag element is provided downstream of the “turning operation amount → limit torque 2” conversion table 62, for example, if a large torque is generated stepwise in the conversion table 62, the shock can be reduced. On the contrary, if a small torque is generated in a stepped manner in the conversion table 62, the first-order delay is effective and the rise of the torque is delayed, resulting in a slow turn response to the operation lever input. End up. Therefore, it is not a good idea to arrange a delay element downstream of the conversion table 62.

-Actions and effects of the first embodiment-
(1) The torque generated by the turning electric motor 25 is linearly delayed even when the turning operation amount becomes a step-like input as shown in FIG. Stand up with a time delay. In other words, even when the turning operation amount is a step-like input, the conventional example as shown in FIG. 4B is not achieved, and a time limit is provided for the amount of change in the torque limit value. As a result, even if the turning operation amount is suddenly increased, smooth turning can be performed without giving an excessive shock to the operator.

  (2) For the same reason as described above, even when there is a sudden rise in the amount of turning operation, no sudden rotational torque is applied to the front working unit 30. Can be avoided.

-Modification in Embodiment 1-
(1) As shown in FIG. 3, when determining the torque limit value, the torque value having the minimum absolute value was selected from the three torque values (limit torque 1, limit torque 2, target torque). However, it is not always necessary to refer to the three pieces of torque information. That is, the limit torque 2 from the “turning operation amount → limit torque 2” conversion table 62 can be omitted. However, the “elapsed time → limit torque 1” conversion table 61 is indispensable.

(2) In FIG. 3, the minimum value selection circuit 64 is used to obtain the final torque limit value. However, depending on the working environment of the hydraulic excavator, it is not always necessary to select the torque having the minimum absolute value. . For example, when an emergency work is being performed, the completion of the work may be prioritized over the shock received by the operator. In this case, the output of the “elapsed time → limit torque 1” conversion table 61 is output. Ignoring settings are also possible. Further, when the hydraulic excavator is operated from a remote place such as wireless control, it is not necessary to consider the shock given to the operator, so that the output of the “elapsed time → limit torque 1” conversion table 61 can be set to be ignored. Is possible.
However, even when urgent work or remote control work is performed, in order to prevent spillage from the bucket 35, it is necessary to avoid a sharp turn when handling soil that contains a large amount of moisture. In that case, it is necessary to adopt the output of the “elapsed time → limit torque 1” conversion table 61.
From the above, according to the working environment of the hydraulic excavator, (b) a comparison process by the minimum value selection circuit 64 is performed in order to minimize the drive torque, or (b) “elapsed time → limit torque 1” conversion table. It is possible to select whether to give priority to the limit torque 1 output from 61 or (c) to give priority to the target torque output from the PID controller 66.

(3) The “elapsed time → limit torque 1” conversion table 61 described so far is operated within a predetermined time range set in advance in response to a turning operation instruction by the operation device 52 as described in FIG. A limit torque 1 proportional to the elapsed time from the start of input is output. However, the following modifications are possible without being limited to such characteristics.
5A to 5D are diagrams illustrating various characteristics of the conversion table 61. FIG. First, in FIG. 5A, the drive torque increases linearly with time. The slope of the straight line should not cause a starting shock. In FIG. 5B, the drive torque increases in a first-order lag with the passage of time. The first-order lag time constant is set so as not to cause a starting shock. In FIG. 5C, the driving torque increases in two steps as time passes. The torque required for starting is secured at the first stage so as not to delay the start of movement, and the time to reach the second stage is set so as not to cause a starting shock. FIG. 5 (D) is a variation of the characteristics of FIG. 5 (C), and is similar in that it has two stages so as not to delay the start of movement. However, since a sudden increase in torque induces a shock to the upper-part turning body, the torque is generated in a ramp shape having a slight inclination in both the first stage and the second stage. Note that when turning the upper swinging body using a hydraulic motor, the target turning torque is not achieved at once, but the characteristic of a relief valve is once used as a relief valve characteristic. A familiar operator can feel operability without a sense of incongruity according to the two-stage torque characteristics as shown in FIG.

<Embodiment 2>
FIG. 6 is an overall configuration diagram of a hydraulic excavator according to the second embodiment. FIG. 7 is a block diagram showing a circuit configuration of a control device 51A according to the second embodiment. FIG. 8 is a diagram illustrating characteristics of the “elapsed time → limit torque 1” conversion table 61a shown in FIG. The second embodiment will be described below with reference to these drawings.

  In the second embodiment, a boom angle sensor 71, an arm angle sensor 72, and a bucket angle sensor 73 are newly provided. The boom angle, arm angle, and bucket angle measured by the boom angle sensor 71, arm angle sensor 72, and bucket angle sensor 73 are sent to the control device 51A. Then, by calculating together with the length, weight of the boom / arm / bucket and the center of gravity of the boom / arm / bucket which are input in advance by the moment of inertia calculator 74, the swiveling of the articulated front working unit 30 is performed. A moment around the axis (moment of inertia) is calculated. Furthermore, by calculating together with the weight center of gravity of the upper swing body 20, the moment of inertia including the upper swing body 20 and the articulated front working unit 30 is calculated. More specifically, the moment of inertia is large in the posture in which the multi-joint type front working unit 30 is extended in the horizontal direction, and the moment of inertia is small in the posture folded as shown in FIG.

  When a certain amount of torque is generated in the turning electric motor 25, the acceleration is increased when the moment of inertia is small. Therefore, when the torque is suddenly increased, the acceleration shock is increased. Therefore, the moment of inertia calculated by the moment of inertia calculator 74 is sent to the “elapsed time → limit torque 1” conversion table 61a to prevent a shock corresponding to the moment of inertia. That is, the “elapsed time → limit torque 1” conversion table 61a has a plurality of tables with different torque gradients with respect to the elapsed time, as shown in FIG. 8, and selects a table that does not cause a shock according to the moment of inertia. The limit torque 1 is output.

  As the “elapsed time → restricted torque 1” conversion table 61a, instead of having a plurality of tables, the torque gradient with respect to the elapsed time may be given as a function using the moment of inertia as a variable.

-Actions and effects of the second embodiment-
According to the second embodiment, since the moment of inertia is calculated in consideration of the posture of the articulated front working unit 30, a turning shock caused by the turning acceleration can be more accurately prevented.

<Embodiment 3>
FIG. 9 is an overall configuration diagram of a hydraulic excavator according to the third embodiment. FIG. 10 is a block diagram showing a circuit configuration of a control device 51B according to the third embodiment. The third embodiment will be described below with reference to these drawings.

In Embodiment 3, in addition to the boom angle sensor 71, the arm angle sensor 72, and the bucket angle sensor 73, the load cell 75 which measures a bucket weight is provided.
The bucket weight measured by the load cell 75 is sent to the control device 51B. Then, the inertia moment calculator 74a calculates the boom angle / arm angle / bucket angle, the length / weight of the boom / arm / bucket inputted in advance, and the center of gravity of the boom / arm / bucket. As a result, a moment (moment of inertia) around the turning axis of the multi-joint type front working unit 30 including earth and sand loaded on the bucket 35 is calculated. Further, by calculating together with the weight center of gravity of the upper swing body 20, the moment of inertia including the upper swing body 20 and the articulated front working unit 30 is calculated. More specifically, the moment of inertia is large in the posture in which the multi-joint type front working unit 30 is extended in the horizontal direction, and the moment of inertia is small in the posture folded as shown in FIG.

  When a torque of a certain magnitude is generated in the turning electric motor 25, the acceleration becomes larger when the moment of inertia is smaller, so that the acceleration shock when the torque is suddenly increased becomes larger. Therefore, the moment of inertia calculated by the moment of inertia calculator 74a is sent to the “elapsed time → limit torque 1” conversion table 61b to prevent a shock corresponding to the moment of inertia. That is, the “elapsed time → limit torque 1” conversion table 61b has a plurality of tables with different torque gradients with respect to the elapsed time, as shown in FIG. 8, and does not generate a shock corresponding to the moment of inertia. Select and output the limit torque 1.

  As the “elapsed time → restricted torque 1” conversion table 61b, instead of having a plurality of tables, the torque gradient with respect to the elapsed time may be given as a function using the moment of inertia as a variable. Further, when measuring the bucket weight, instead of the load cell 75, it may be obtained by calculation from any one or more of the cylinder pressures of the boom cylinder 32, the arm cylinder 34, and the bucket cylinder 36, the boom angle, the arm angle, and the bucket angle. Good.

-Actions and effects of the third embodiment-
According to the third embodiment, the moment of inertia is calculated in consideration of the posture of the articulated front working unit 30 and the use state (weight) of the bucket as the working state of the articulated front working unit 30. Thus, the turning shock caused by the turning acceleration can be more accurately prevented.

<Embodiment 4>
FIG. 11 is an overall configuration diagram of a hydraulic excavator according to the fourth embodiment. FIG. 12 is a block diagram showing a circuit configuration of a control device 51C according to the fourth embodiment. FIG. 13 is a diagram illustrating characteristics of the “elapsed time → limit torque 1” conversion table 61c shown in FIG. A fourth embodiment will be described below with reference to these drawings.

  In Embodiment 4, in addition to the configuration of FIG. 9 (Embodiment 3), an inclination sensor 76 for measuring the inclination of the vehicle body is provided. The vehicle body inclination angle measured by the inclination sensor 76 is sent to the control device 51. Then, the inertia moment calculator 74b calculates the boom angle / arm angle / bucket angle / bucket weight, the length / weight of the boom / arm / bucket inputted in advance, and the center of gravity of the boom / arm / bucket. Thus, the torque generated by the multi-joint type front working unit 30 including the earth and sand loaded on the bucket and the upper swing body 20 around the swing axis by receiving gravity is calculated. The moment of inertia calculated by the moment of inertia calculator 74b is sent to the “elapsed time → limit torque 1” conversion table 61c.

  Torque generated by gravity on the slope works to turn the upper swing body 20. For example, assuming that the clockwise torque is positive and the clockwise torque T0 is applied due to gravity, the vehicle does not turn unless a torque equal to or greater than T0 is generated counterclockwise. Therefore, in the “elapsed time → limit torque 1” conversion table 61c, as shown in FIG. 13B, an offset of T0 is given in advance as a counterclockwise (negative) torque limit. Similarly, when the counterclockwise torque T0 is applied due to gravity, the torque does not turn unless a torque equal to or greater than T0 is generated in the clockwise direction. Therefore, as shown in FIG. As shown in FIG.

  In the fourth embodiment described above, the moment of inertia is calculated by further adding the inclination angle to the third embodiment (= calculating the moment of inertia based on the posture of the front working unit and the bucket weight) 3. Yes. However, the moment of inertia may be calculated based only on the tilt angle, or the moment of inertia may be calculated based on the attitude of the front working unit and the tilt angle.

-Actions and effects of the fourth embodiment-
According to the fourth embodiment, by providing the tilt sensor 76, it is possible to calculate the moment of inertia considering the tilt of the vehicle body. As a result, the turning acceleration can be more accurately limited to prevent a turning shock.

The above description is merely an example, and the present invention is not limited to the above-described embodiments and modifications unless the features of the present invention are impaired.
It is also possible to combine the embodiment and one of the modified examples, or to combine the embodiment and a plurality of modified examples.
It is possible to combine the modified examples in any way.
Furthermore, other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

1 is an overall configuration diagram of a hydraulic excavator according to Embodiment 1. FIG. It is a block diagram which shows the power transmission path | route of the hydraulic shovel shown in FIG. 2 is a block diagram illustrating a circuit configuration of a control device according to Embodiment 1. FIG. FIG. 6 is a diagram for explaining the operation and effect according to the first embodiment. FIG. 6 is a diagram illustrating various characteristics of an “elapsed time → limit torque 1” conversion table according to the first embodiment. FIG. 3 is an overall configuration diagram of a hydraulic excavator according to a second embodiment. FIG. 5 is a block diagram showing a circuit configuration of a control device according to Embodiment 2. FIG. 10 is a diagram illustrating various characteristics of an “elapsed time → limit torque 1” conversion table according to the second embodiment. 6 is an overall configuration diagram of a hydraulic excavator according to Embodiment 3. FIG. FIG. 6 is a block diagram illustrating a circuit configuration of a control device according to a third embodiment. FIG. 6 is an overall configuration diagram of a hydraulic excavator according to a fourth embodiment. FIG. 6 is a block diagram showing a circuit configuration of a control device according to Embodiment 4. FIG. 10 is a diagram illustrating various characteristics of an “elapsed time → limit torque 1” conversion table according to the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lower traveling body 20 Upper turning body 22 Engine 22
23 Generator 24 Battery 25 Turning motor 28 Turning inverter 30 Articulated front working unit 31 Boom 33 Arm 35 Bucket 51 Control device 52 Operation device 53 Rotational speed sensor

Claims (5)

In a construction machine that drives an upper swinging body placed on a lower traveling body by an electric motor,
An operation unit for outputting a turning operation signal for turning the upper turning body;
A first torque setting unit that sets a maximum value of a drive torque generated by the electric motor according to an elapsed time after the turning operation signal is output;
A second torque setting unit that sets a target torque value of the electric motor based on a deviation between a predetermined electric motor rotation speed corresponding to the turning operation signal and an actual rotation speed of the electric motor;
Torque that specifies a torque limit value of the electric motor by referring to the maximum value of the driving torque set by the first torque setting unit and the target torque value set by the second torque setting unit A limit value specification part;
A rotation speed designating unit that designates a predetermined motor rotation speed corresponding to the turning operation signal as a target rotation speed of the motor;
An electric motor controller that drives the electric motor with the torque limit value and the target rotational speed specified by the torque limit value specifying unit and the rotational speed specifying unit as control inputs;
A construction machine comprising: The construction machine according to claim 1, further comprising:
A third torque setting unit that sets a predetermined limit torque value corresponding to the turning operation signal;
The torque limit value designating part is
The maximum value of the driving torque set by the first torque setting unit, the target torque value set by the second torque setting unit, and the limit torque set by the third torque setting unit A torque value that minimizes the absolute value of these three torque values is designated as the torque limit value of the motor.
Construction machinery characterized by that. In the construction machine according to claim 1 or 2, further,
Detecting means for detecting a posture or a working state of an articulated front working unit driven in accordance with an operation output from the operation unit;
Calculating means for calculating the moment of inertia of the upper-part turning body including the front working unit based on a detection signal output from the detection unit;
The construction machine characterized in that the torque limit value designating unit designates a torque limit value of the electric motor with reference to the moment of inertia. In the construction machine according to claim 1 or 2, further,
An inclination angle detecting means for detecting an inclination angle formed by a rotation surface of the upper swing body with a horizontal plane;
Calculation means for calculating the moment of inertia of the upper-part turning body including the multi-joint type front working unit based on the inclination angle output from the inclination angle detection means;
The construction machine characterized in that the torque limit value designating unit designates a torque limit value of the electric motor with reference to the moment of inertia. In a turning control device for a construction machine that turns an upper turning body using an electric motor controlled by an inverter,
An operation signal input means for inputting a turning operation signal issued in response to an operation of an operation lever for turning the upper turning body;
First torque setting means for setting a maximum value of drive torque generated by the electric motor according to an elapsed time after the turning operation signal is input;
Second torque setting means for setting a target torque value of the electric motor based on a deviation between a predetermined motor rotation speed corresponding to the turning operation signal and an actual rotation speed of the electric motor;
Torque limit designating a torque limit value of the electric motor with reference to the maximum value of the driving torque set by the first torque setting means and the target torque value set by the second torque setting means. Value specification means,
A rotation speed designation means for designating a predetermined motor rotation speed as a target rotation speed of the electric motor in response to the turning operation signal;
Output means for supplying the torque limit value and the target rotation speed specified by the torque limit value specifying means and the rotation speed specifying means to a control input terminal of the inverter;
A turning control device comprising:

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