JPS6313920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hoisting control device for a mobile traveling body.

2. Description of the Related Art In conventional traveling moving objects such as cargo handling cranes, squirrel cage induction motors are used as hoisting, traversing, and traveling motors, and are driven by variable voltage and variable frequency power sources. However, due to the characteristics of this squirrel cage induction motor, even if a starting command is given, the starting torque does not instantly reach the required torque needed to lift the load. Therefore, when using a squirrel cage induction motor for hoisting, and when starting it with a suspended load, the starting torque does not reach the required torque at the hoisting place even if a starting command is given, that is, the starting torque does not reach the torque at the hoisting place. If it is smaller, the load will drop once, which may pose a danger to the work. In order to solve this problem, we need to detect the torque of the electric motor in order to generate the necessary hoisting torque in the hoisting motor at the time of starting.
Methods such as detecting motor slippage, detecting motor magnetic flux, or controlling the vector of magnetic flux and current of a motor have been proposed, but all of these methods require various special equipment, making the equipment complex and requiring maintenance. There are some drawbacks.

The present invention has been made in view of this, and even when a squirrel cage induction motor is used for hoisting, a variable voltage variable frequency power source (inverter) is used to start the motor in a manner that ensures and safely lifts a load. ) is applied to the servo lifter of the servo lifter brake, with a simple configuration,
This was done to solve the drawbacks of the conventional method.

The present invention will be explained below based on illustrated embodiments.

FIG. 1 shows an example in which _the present invention is applied to an _overhead crane operated by an operating _device . Equipped with various electric motors such as
A hoisting inverter I ₁ , a traversing inverter _{I 2} , and a traveling inverter I 3 are connected to M 1 , _{M 2 ,} and M ₃ , respectively.
Each inverter is equipped with a regenerative braking unit so that the speed of each electric motor is controlled by a variable voltage variable frequency inverter. In addition, a control device CS is connected to these inverters, and each inverter I ₁ , I ₂ , I ₃ is operated by an operation device C based on commands from the control device CS.
In this system, the control device selectively operates the inverters for hoisting/up/down, traversing, and running in response to commands from an operating device (controller in the driver's cab, pendant switch, etc.), and supplies variable frequency variable voltage to each electric motor. be.

Further, the operating device is equipped with a speed setting device for each of the inverters, and a regenerative braking unit consisting of a group of resistors is connected to each inverter to absorb regenerative power generated due to a sudden change in frequency.

Next, the winding portion will be explained.

The hoisting motor _M1 uses a squirrel-cage induction motor, and the other end of the motor shaft is connected to the drum of the servo lifter brake CB, and the other end is connected to the hoisting drum D via the reducer G.
is connected to.

Further, a variable voltage variable frequency inverter _I1 is connected between the primary side of the hoisting motor _M1 and the power source, and the primary side of the servo lifter brake CB is connected to the secondary side of the inverter.

The operation of the apparatus constructed as described above will be explained first. First, a hoisting command is given by pressing a hoisting button such as a push button switch using the operating device C. If this time is t=o,
The hoisting inverter _I1 is activated via the control device CS, and the output frequency F and output voltage V of the inverter rise from the lowest values Fo and Vo, respectively, at time _t1 .
Reach Ft ₁ and Vt ₁ .

When t=o, the motor starting torque To is smaller than the maximum load torque Tm.

At t= _t1 , the motor torque _Tt1 becomes larger than the maximum load torque Tm. At this time t ₁ , the inverter output frequency Ft ₁ and output voltage
If the setting is made so that the motor of the servo lifter CB can be energized at Vt ₁ to release the operating brake, the motor M ₁ starts to start after time t ₁ and completes at time t ₂ .

Figure 3 shows the motor torque T, inverter output frequency F, and inverter output voltage during time t = 0 (when the controller is commanded), t = t ₁ (when the brake is released), and t = t ₂ (when the motor is started). Changes in each value of V are shown.

It is clear from the above explanation that when t=o, the motor starting torque To is the required torque Tm to lift the load.
Since the servo lifter brake is smaller, Fo, Vo
In some cases, the load is not released and the load is retained, and the load is never lowered. When t=t ₂ is reached, the motor torque t ₁ > tm, and at the same time Ft ₁ , Vt ₁
By applying electricity, the servo lifter CB begins to be released for the first time, and the hoisting motor of the crane starts to start and begins to hoist the load. As the output frequency and output voltage of the inverter increase over time, the brake force is gradually relaxed, and at t= _t2 , the brake is completely released and the preset speed is reached.

According to the present invention, when hoisting the mobile traveling body,
The output frequency output voltage of the inverter is applied to the motor of the servo lifter brake, and the brake is released after the motor torque exceeds the maximum load torque, so safety can be increased without the risk of the load once dropping. Furthermore, it has advantages such as a simple device.

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram of a crane device to which the present invention is applied, Fig. 2 is a block diagram of a hoisting device, and Fig. 3 is an explanation showing changes over time in motor torque, inverter output frequency, output voltage, and motor rotation speed. It is a diagram. _M1 ...Hoisting motor, _I1 ...Hoisting inverter, CS...Control device, C...Operator, CB...Servo lifter brake, G...Reducer, D...Hoisting drum.

Claims (1)

[Claims] 1. In hoisting control of a moving body in which the speed of a drive motor is controlled by an inverter, the output frequency and output voltage of the inverter are applied to a servo lifter brake directly connected to the hoisting motor, and the starting torque of the hoisting motor is When the torque exceeds the required torque for lifting the load, the brake is released so that the load can be safely lifted without falling even if the starting torque of the electric motor is smaller than the required torque for lifting the load. A hoisting control device for a mobile traveling body, characterized by: