JPH0127951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a hoisting device for a jib hoisting crane equipped with an inverter-controlled electric hoisting winch.

(Prior Art) Fig. 1 shows an example of a crane having a hoisting jib. A control panel 11 and the like are mounted, and a jib 5 is attached to the front part of the winding body 1 so as to be able to rise and fall freely around a jib foot 23. It is hung on the guide sheave 17 at the top, and is further hung in multiple numbers between the sheave block 19 at the top of the A frame and the bridle 18 connected to the top of the jib 5 via the pendant rope 8. The jib 5 is now undulating. In addition, the hoisting rope 6 wound up and let out by the hoisting winch 2 is connected to a jib point sheave 20 at the top of the jib 5 and a sheave 2 at the hook 9.
1. It is wrapped around a different jib point sheave 22 at the top of the jib 5, and the terminal end is connected to a load detector (load cell) 16 attached to the jib 5. The output signal of the load detector 16 and the output signal of the jib angle detector 10 are input to a moment limiter 12 provided in the control panel 11 for overload prevention.

In such a crane, the luffing winch 3
When the undulating rope is wound at a constant speed, the horizontal movement speed of the hook 9, that is, the suspended load, is equal to the jib angle θ
(See Figure 2) becomes larger as it becomes larger,
Near the upright position of jib 5, the suspended load rapidly
It is dangerous to get close to In particular, in a crane in which the driver's seat is located in front of the application route 1, there is a risk that the suspended load will collide with the driver's seat. As a means to solve such problems, a pole change motor or a parent-child motor is used as the drive device of the hoisting winch 3,
There is also a configuration in which a limit switch is installed that operates when the jib angle reaches a certain angle, and the rotational speed of the hoisting winch 3 is automatically switched to a lower speed side when the jib angle exceeds a certain angle, but the speed change is abrupt. This may cause the suspended load to sway.

(Object of the Invention) In view of the above-mentioned points, an object of the present invention is to provide a jib hoisting device for a jib crane that can smoothly change the hoisting speed without shaking the suspended load too much and ensure safe operation. shall be.

(Structure of the Invention) In order to achieve this object, the present invention includes an electric motor whose speed is controlled by an inverter device as a drive device for the hoisting winch, and a jib angle detector or a signal converter that converts the output thereof. By providing an output characteristic to obtain an output signal of cos θ with respect to the angle θ, and using the output signal as a frequency setting signal of the inverter device,
The present invention is characterized in that the jib hoisting speed is reduced as the jib angle increases.

(Example) The details of the present invention will be explained below. In a general jib crane, the horizontal movement speed V _H of the suspended load when the jib is raised or lowered is determined by solving equations (1) to (5).

V _H = dR/dt...(1) dl/dt=V/n...(2) l ² = (H-Y) ² + (R+X) ² ...(3) L ² = H ² + R ² ... ...(4) θ=tan ^-1 (H/R) ...(5) Here, each symbol other than the above in equations (1) to (5) above has the following meaning as shown in Figure 2. means.

R: Horizontal distance l from the center of the jib foot 23 of the jib 5 to the center of the jib point sheave 20; Distance V between the center of the guide sheave 17 and the center of the jib point sheave 20; Winding and unwinding speed n of the hoisting rope 7; undulation Length L of rope 7; Length X of jib 5; Horizontal distance Y from the center of jib foot 23 to the center of guide sheave 17 at the top of A frame 4; Vertical distance H from the center of the jib point sheave 20 to the center of the jib foot 23 In this embodiment, a nonlinear potentiometer is used as the jib angle detector 10 shown in FIG. As described below, by using the output as a frequency setting signal for the inverter of the motor for driving the hoisting winch, the jib hoisting speed is decreased as the jib angle θ increases.

FIG. 3 shows an inverter-controlled electric motor 13 for driving the hoisting winch 3 in this embodiment (generally, a squirrel cage motor is used as this electric motor).
This is an example of a control circuit. Reference numeral 15 denotes an operation switch, which controls the electric motor 13 in the winding direction of the hoisting rope 7;
It consists of operation switches PB1 and PB2 for instructing rotation in the feeding direction (that is, the upright direction and the lowering direction of the jib 5, respectively). RU and RD are relays that are energized by the operation of these switches PB1 and PB2, and the contact points of these relays are indicated by letters with a or b added to the alphanumeric lowercase letters.

The inverter device 12 of the electric motor 13 once rectifies the three-phase AC input from input terminals R, S, and T, and outputs variable frequency AC output from output terminals U, V, and W.
E is a ground terminal, f and g are control power supply terminals, d and e are rotation direction command input terminals, b is a frequency setting signal input terminal, and a is a start signal self-holding relay. Terminal c is a common terminal for the control circuit, and h is a start signal input terminal. The jib angle detector 10 has a nonlinear output characteristic as shown in FIG.
Output characteristics of cosθ (cosθ= at jib angle of 0 degrees (horizontal)
1, cos=0 at a jib angle of 90 degrees). A signal converter 14 converts the level of the output of the angle detector 10, and its output is applied to the frequency setting signal input terminal f.

In this circuit, the stand-up command operation switch
When PB1 or lodging command operation switch PB2 is operated, relay RU or RD is energized, these a contacts rua or rda are closed, a signal is applied to rotation direction command input terminal d or e, and the rotation direction is commanded. Then, an actuation signal is applied to the start signal input terminal h and the start signal self-holding relay terminal a, and the electric motor 13 rotates in the winding or unwinding direction of the hoisting rope 7. In this case, since a signal with the characteristics shown in FIG. 4 is output as a frequency setting signal to the frequency setting signal input terminal f, the inverter device 12 lowers the frequency as the angle of the jib 5 increases. As the output is increased, the rotational speed of the electric motor 13 becomes lower. That is, the hoisting winch 3 automatically operates at high speed where the jib angle θ is small, and automatically operates at low speed where the jib angle θ is large, reducing the jib hoisting speed. As a result, as shown in FIG. As shown in the figure, in comparison with a general crane, in which the horizontal movement speed of the suspended load increases as the working radius becomes smaller, according to this embodiment, the horizontal movement speed of the suspended load at each working radius increases. The moving speed is almost constant.

In the above embodiment, the jib angle detector 1
Although the output characteristic of the jib angle detector 10 is made nonlinear, the output characteristic of the jib angle detector 10 may be made linear, and the nonlinear characteristic may be obtained by the signal converter 14. Furthermore, in the present invention, such a linear characteristic can be obtained by using a jib angle detector whose output decreases as the jib angle θ increases, or by converting the output of the jib angle detector with a signal converter. For example, as shown in Figure 5, the horizontal movement speed of the suspended load is not constant, but it is close to constant,
Changes in speed are much smaller than before.

(Effects of the Invention) As described above, according to the present invention, even if the hoisting winch is operated continuously, the horizontal movement speed of the suspended load remains constant or close to constant, and the suspended load is It is possible to eliminate the risk of collision with the body, etc. In addition, compared to conventional parent-child motors, etc., the heave speed does not change suddenly.
Since the suspended load can be moved smoothly, the suspended load will not sway. Therefore, according to the present invention, safe driving can be ensured.

[Brief explanation of drawings]

Figure 1 is an overall view of a typical jib crane, Figure 2
The figure is a dimensional diagram of each part of a crane used to explain the principles of the present invention, Figure 3 is a control circuit diagram of a jib hoisting motor showing an embodiment of the present invention, and Figure 4 is the output of a jib angle detector in this embodiment. The characteristic diagram, FIG. 5, is a diagram showing the relationship between the jib angle and the horizontal movement speed of the suspended load in this embodiment in comparison with the conventional example. 3... Lifting winch, 5... Jib, 10... Jib angle detector, 12... Inverter device, 13...
...Electric motor, 14...Signal converter, RU, RD...
relay.

Claims (1)

[Claims] 1. An electric motor whose speed is controlled by an inverter device is provided as a drive device for the hoisting winch, and a jib angle detector or a signal converter that converts its output is provided with an output signal of cos θ for the jib angle θ. The shib is characterized in that the jib hoisting speed is reduced as the jib angle increases by having an output characteristic that obtains the same and using the output signal as a frequency setting signal of the inverter device. Crane jib hoisting equipment. 2. The jib hoisting device for a jib crane according to claim 1, wherein a nonlinear potentiometer is used as the jib angle detector.