EP0691301A1 - Slewing gear for a crane - Google Patents

Abstract

The rotating parts of the crane are driven by gearing from an electric motor controlled by an actuator in response to measurements of its rotational speed and torque. When the load suspended from the jib is swinging forwards during run-up of the motor and rotation of the jib, the driving torque is reduced as the speed increases. When the load is swinging backwards the torque is maintained at a substantially constant value. <IMAGE>

Description

The invention relates to a slewing gear for a crane, preferably a tower crane rotating below or above, with an electric motor which drives the pinion meshing with a slewing ring of the crane masses to be rotated via a gear and with a device which controls the motor in accordance with the control movements applied to an actuating device.

Known rotating mechanisms of this type have a fluid coupling between the electric motor and the transmission, a brake holding the drive pinion and braking being opened only when the motor has built up such a large torque via the fluid coupling that, for example, wind forces acting on the crane boom cause the torque to reverse Boom is prevented. In this known slewing gear, the start-up basically takes place with a high torque, which, in accordance with the acceleration caused thereby, stimulates a relatively wide swinging of the load. In the known slewing gear, the motor drive is controlled via the motor torque, so that the motor generates a braking counter-torque when the load exerts a pulling moment on the boom due to the oscillation. Such an engine control, however, cannot suppress the undesired oscillation of the load, so that sensitive control of the speed of rotation during rotation and the braking phase is not possible.

The object of the invention is to provide a slewing gear of the type specified at the outset which enables sensitive and precise control of the rotary movement of the boom.

According to the invention, this object is achieved in a slewing gear of the type specified at the outset in that devices for measuring the engine speed and the engine torque are provided and that during the starting and turning operation at an engine speed increasing due to the oscillating load, the drive torque is reduced to zero and at one Back swinging the load the drive torque is essentially maintained. Correspondingly, during the braking phase, the predetermined drop in speed when the load is swinging forward can essentially be maintained by a braking torque applied to the motor, and when the load swings back, the motor torque can be reduced in such a way that the braking torque of the swinging back load is used.

In the slewing gear according to the invention, the drive motor is directly connected to the gear driving the pinion without the interposition of a fluid coupling, so that the drive pinion can be regulated by appropriate control of the drive motor in such a way that the desired drive characteristic is achieved.

By measuring the engine speed and the engine torque, the parameters required for controlling the drive pinion can be recorded. The slewing gear according to the invention is provided with such a drive control that the unavoidable oscillation of the load is damped. This is achieved during the start-up and turning operation in that when the load swings, that is to say pulling, by consciously lowering the engine torque, an increasing engine speed is accepted, which by appropriate Tracking the suspension point of the rope on the boom dampens the oscillating movement. When the load swings back, the motor torque gently rises again from below to maintain the set speed, so that the desired speed is essentially maintained without the movement of the movement being increased again. In the slewing gear according to the invention, the motor torque is regulated so that the desired rotational speed is maintained as possible so that it acts in the sense of damping the pendulum movement.

During the braking phase, the engine torque is again regulated in the sense of damping and suppressing the pendulum movement. This is done in that the predetermined drop in speed is maintained when the load swings in particular during the braking phase, so that the engine torque acts as a brake. When the load swings back, however, the engine torque is reduced in such a way that the braking torque of the swinging back load is used.

Since in the slewing gear according to the invention the engine torque is optimally adapted to the force transmitted from the oscillating load to the boom both during the starting and braking phase and during the turning operation, an optimal damping of the oscillating movement can be achieved.

Due to the speed control of the drive motor according to the invention, it is possible to start gently against any wind loads, without having to build up a large torque which prevents jerky starting.

Due to the control of the drive motor according to the invention, continuously variable rotational speeds can be set with smooth acceleration and deceleration of the rotary movement.

The invention can also be defined in such a way that a rotational speed is specified as a setpoint, that the current rotational speed is determined, that if the setpoint is exceeded, the setpoint is constant or rising and / or if the setpoint falls below, if the setpoint falls in time, the engine torque is reduced to zero and that the current speed of rotation is otherwise regulated to the setpoint.

In the slewing gear according to the invention, the electric motor is coupled with the rotational movement of the boom in a slip-free manner, a detector being provided for determining the rotational speed of the boom and the control unit being designed for controlling according to the method specified above. According to the invention, when the swinging of a load acts in the sense of a desired boom movement, an acting torque of the rotary drive is removed. Here, a control loop is opened for regulating the rotational speed of the boom or the torque acting on the boom. It is thereby achieved that the energy of the swinging load is used for the positive or negative acceleration of the boom and is thereby reduced. As a result, a pendulum movement of the load is damped.

By determining and regulating the speed of rotation of the jib, the crane operator can drive the crane with pinpoint accuracy, especially when wind loads occur. This is supported by a slip-free coupling of the rotary motor to the rotary movement of the boom.

According to an advantageous embodiment, the acting torque is reduced to zero only in the event of deviations in the current rotational speed from the target value, the amounts of which are smaller than a maximum value, and the deviations are otherwise counteracted. This ensures that the current speed of rotation does not deviate too much from a predefined setpoint or a specific setpoint curve.

Another preferred embodiment is characterized in that the acting torque is only changed continuously. This can be achieved, for example, by using an asynchronous motor in conjunction with a leading edge control as the electric motor. A constant change in the torque ensures that jerk-free movement is achieved and the loads on the crane are kept low. Alternatively, an asynchronous motor with electrical frequency control can also be provided.

According to a further preferred embodiment, a harmonious rotary movement of the boom is achieved in that a steady setpoint course is determined in the case of inconsistent setpoint targets. This means that when a new setpoint is entered, it is compared with the previous setpoint and an adapted setpoint curve is run through for adjustment. In this case, a particularly easy movement sequence is achieved in particular if the specific setpoint curve, ie the setpoint curve, represents a continuously differentiable function.

According to a further preferred embodiment, it is provided that the acting torque when the setpoint is undershot by the current rotational speed is reduced to zero only when the setpoint curve falls if the current rotational speed is greater than the target value target. By This measure ensures that when the boom is braked, the speed of rotation of the boom is not slowed down too much, ie below the desired target value.

In the slewing gear according to the invention it is further provided that the greatest driving torque of the motor is limited, so that the construction of the crane cannot be overloaded.

If a rapid braking of the rotation is required, this is done by a special program, after the oscillating leading load is constantly braked by a counter torque. The slewing gear according to the invention thus also enables conventional countering for rapid braking, an electronic control monitoring the countering being provided.

The motor can be a conventional slip ring asynchronous motor, with which different resistance levels can be switched on according to the desired motor characteristics, or an asynchronous motor with a special rotor.

The regulation of the speed and the motor torque can be carried out in the usual way by a phase control on the basis of the set voltage time area, if an asynchronous motor is selected as the drive motor, or by a conventional frequency control.

According to the present invention, the drive is started in a speed-controlled manner, while braking is torque-controlled by reversing the rotating field (so-called "countering").

Braking is automatically braked whenever the control lever is reset to zero. This automatic Braking is initiated particularly smoothly because the actual speed actual value at the beginning of the braking process is adopted as the speed setpoint, which is then reduced to zero after a curve ramp. The difference between this setpoint and the current rotational speed is the setpoint for the braking torque. Since the speed setpoint is equal to the current speed when the braking process is initiated, the braking torque always starts from zero and is therefore completely bumpless.

In addition to the automatic braking process through automatic, torque-controlled locking, the crane operator can increase the acting torque by specifying a setpoint against the current direction of rotation. If the crane operator remains in this counter position, a torque-controlled reversal of the direction of rotation takes place after the braking process. The acting torque can be continuously adjusted from zero to maximum via the control lever, so that it is possible to keep the boom in the "floating" in the wind, which enables particularly sensitive positioning.

The acting torque is limited to a maximum amount in both speed-controlled operation and torque-controlled operation. The reversal of efficiency between driving and braking is particularly taken into account, so that the maximum permissible torque acting on the crane construction is not exceeded.

The maximum torque can be set depending on the length of the boom, which can vary depending on the crane type. Another option for switching over to a maximum amount of the acting torque is provided for different boom positions.

In the case of speed-controlled starting, a special method ensures that the whip effect, which occurs in particular with down-slewing cranes, does not occur as a result of the boom advancing when the boom accelerates. If, due to the load and / or the wind conditions, the rotational speed cannot follow the steady course of the setpoint because the maximum torque cannot be exceeded due to the torque limitation, the further steady increase in the setpoint is stopped if there is a maximum deviation between the setpoint and the current rotational speed until the deviation is again within the intended limit. This ensures that the acting torque is reduced when the boom rushes forward (whip effect) and no further acceleration energy is introduced into the construction.

Fig. 1

ein die Aktivierung der verschiedenen Regler betreffendes Flußdiagramm,

Fig. 2

ein die Drehzahl- und Momentenregler betreffendes Flußdiagramm,

Fig. 3

ein den Bremsregler betreffendes Flußdiagramm und

Fig. 4

ein Flußdiagramm für die Verarbeitung der Reglersignale zur Steuerung des Motors.

Exemplary embodiments of the control of the slewing gear are explained in more detail below with reference to the drawing. In this shows:

Fig. 1

a flow chart relating to the activation of the various controllers,

Fig. 2

a flow chart relating to the speed and torque controllers,

Fig. 3

a flowchart relating to the brake controller and

Fig. 4

a flowchart for the processing of the controller signals for controlling the engine.

According to the flowchart according to FIG. 1, in a first step it is checked whether the rotational speed setpoint set with the control lever is zero. If this is the case, the brake controller activated to initiate braking. Braking is automatically braked whenever the control lever is reset to zero.

If the set speed setpoint is different from zero, a second step is used to check whether the setpoint direction is the same as the direction of rotation. If this is not the case, the brake controller is activated. Has the setpoint direction been changed, i. that is, if a setpoint has been set against the current direction of rotation in order to achieve faster braking, the torque controller is also activated and the speed controller deactivated.

Has the setpoint direction not changed, i. That is, if the direction of rotation has been set against the target direction of rotation due to other influences, the speed controller is activated in a third step and the torque controller is deactivated.

If the setpoint direction is the same as the direction of rotation, it is checked whether the setpoint has been zero since the last change in the direction of rotation. If this is not the case, which corresponds, for example, to the torque-controlled reversal of the direction of rotation after rapid braking by countering and maintaining the counter position, the torque controller is activated and the speed controller deactivated.

If the setpoint was zero when the last direction of rotation was changed, the slewing gear according to the invention is in the start-up and turning mode and accordingly the speed controller is activated and the torque controller is deactivated.

The flow chart shown in FIG. 2 shows the further processing of the set rotational speed setpoint. In the setpoint processing, the setpoint is compared with the actual value and a steady setpoint course to the setpoint target is created. The prepared setpoint is processed together with the measured speed value in the speed controller if it is active.

If the target direction of rotation is the same as the actual direction of rotation, the target value is reduced depending on the speed. The reduced setpoint or the setpoint is processed with the torque characteristic.

3 shows the flow diagram for the brake control system. As long as the brake controller is inactive, the current speed is always saved as the brake controller setpoint. As soon as the brake controller becomes active, a setpoint curve is generated in the form of a ramp from the last saved speed value to 0. This setpoint curve is processed with the measured speed in the brake controller.

Fig. 4 shows a flow diagram for the processing of the controller signals for controlling the motor. The totalizer checks the activity of the controller and determines the current limit with the measured speed. Boom position, current limitation and the measured current are processed in the current regulator in such a way that the power section ensures the operation of the motor according to the invention, which delivers the torque required for the rotation of the crane.

Claims (7)

Slewing gear for a crane, preferably a tower crane rotating below or above,
with an electric motor driving a pinion which meshes with a slewing ring of the crane masses to be turned, and
with a device controlling the motor in accordance with the control movements applied to an actuating device,
characterized,
that devices for measuring the engine speed and engine torque are provided and
that the drive torque is reduced to zero during the start-up and turning operation at an engine speed increasing due to the oscillating load, and the drive torque is essentially maintained when the load swings back. Slewing gear according to the preamble of claim 1, characterized in that during the braking phase, the predetermined drop in speed when the load swings forwards is essentially held by a braking torque applied to the motor, and when the load swings back, the motor torque is reduced in such a way that the braking moment swinging load is exploited. Slewing gear according to claim 1 or 2, characterized in that when the actuating device initiating the rotary movement is actuated, the motor torque increases according to a predetermined time function corresponding to the set desired rotational speed. Slewing gear according to one of claims 1 to 3, characterized in that the greatest driving torque of the motor is limited. Slewing gear according to one of claims 1 to 4, characterized in that the rotation is braked quickly by a special program, according to which the oscillating leading load is continuously braked by a counter torque. Slewing gear according to one of claims 1 to 5, characterized in that the motor is a slip ring asynchronous motor controlled by phase control. Slewing gear according to one of claims 1 to 5, characterized in that the motor is a motor controlled by frequency control.

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