JPS6151493A - Lifting device for crane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hoisting device for a jib hoisting crane equipped with an inverter-controlled electric hoisting winch and an electronic moment limiter.

[Conventional technology]

Fig. 4 shows an example of a crane having a hoisting jib. A jib 5 is attached to the front part of the revolving body 1 so as to be able to be raised and lowered freely, and the hoisting rope 7 that is taken up and let out by the hoisting winch 3 is hung on a guide sheep 17 at the top of the A frame 4. , Furthermore, a plurality of prydles 18 are connected to the sheep block 19 at the top of the A frame and the bottom part 3 of the jib 5 via the pendant rope 8, and the jib 5 is hoisted by the operation of the hoisting winch 3. It looks like this. The hoisting rope 6 taken up and unwound by the hoisting winch 2 includes a jib point sheave 20 at the top of the jib 5, a sheave 21 at the hook 9, and a jib point sheave 22 at the top of the jib 5, which is different from the above. The hook is turned, and the end is connected to a load detector (load cell) 10 attached to the jib 5.

The load detector 10 converts the tension of the hoisting rope 6 into an electric signal, and its output signal is sent to the control panel 16 along with the output signal of the jib angle detector 11 which converts the angle of the jib 5 into an electric signal. Electronic moment limiter 1 installed in
2 is input. The moment limiter 12 is a device for preventing overload, and stores the rated load according to the working radius for each jib length in advance. Based on the signal, the actual load and working radius are calculated and compared with the stored values.
It has a function to output a signal when this value is exceeded.

In such a lane, the hoisting device handles various loads within the rated load range, but if an electric motor whose speed is controlled by an inverter is used as the drive device for the hoisting winch 2, it will be able to hoist the maximum load at the maximum speed. Conventionally, the capacity of an electric motor is determined by this maximum output. However, from an operational point of view, the highest speed required is hoisting up an empty hook, and when the load is large, it is rarely operated at the highest speed for safety reasons.

That is, conventionally, the rated output of an electric motor was determined based on the maximum speed of the maximum load with little possibility of operation.
In most cases, it is uneconomical to operate at a power that is much lower than the rated power. However, for this reason, if a motor with a small rated output is used as a drive device for the hoisting winch, safe operation becomes impossible.

[Problem that the invention seeks to solve]

In view of the above-mentioned points, the present invention aims to solve the problem that the output of the drive motor of the hoisting winch is not effectively utilized and a part of the capacity is wasted.

Page 5 [Means for Solving the Problems] In order to solve the above problems, the crane hoisting device of the present invention includes an electric motor that performs multi-speed control in an inverter device as a drive device of the hoisting winch. In addition, in a crane equipped with an electronic moment limiter, the electronic moment limiter has a function of outputting a signal every time the actual lifting load exceeds a preset set load regardless of the working radius. , the inverter device includes a circuit that directly transmits a speed control signal of the motor from a frequency setting potentiometer when there is no output of the signal generated by the electronic moment limiter; The present invention is characterized by comprising at least one circuit that converts the speed control signal of the motor at a constant ratio and transmits the converted signal from a frequency setting potentiometer when the signal is output.

[Effect]

With the above-described configuration, the hoisting crane of the present invention -, 6-
, :(f The device automatically changes the maximum speed of the hoisting winch drive motor according to the load of the crane.

〔Example〕

Hereinafter, one embodiment of the crane hoisting device of the present invention will be described in the first embodiment.
This will be explained with reference to FIGS. 4 to 4.

In the present invention, the load detector 10 shown in FIG.
Jib angle detector 11 and electronic moment limiter 12
In addition to the above functions, the moment limiter has a function of outputting a signal every time the actual lifting load exceeds a preset constant load regardless of the working radius.

FIGS. 1(a) and 1(b) show a control circuit of the electric motor 13 for driving the hoisting winch 2 (generally, a squirrel cage induction motor is used as this electric motor),
FIG. 1(a) shows an inverter circuit, and FIG. 1(b) shows a circuit for controlling the inverter circuit. 25 is a set load W in which the lifting load W detected by the load detector 10 is stored in the moment limiter 12 in advance. (Second
26 is a contact a of a relay γ (not shown) which is excited by a signal generated in a range (w > wo) exceeding the range (w > wo), where the lifting load W is the maximum load W (see figure 2). b of a relay (not shown) that is energized by a signal generated when (W > WI) exceeds (see)
It is a point of contact. 2M is a relay that is excited when the contact 25 is closed.

24 is an operation switch, which connects the electric motor 13 to the hoisting rope 6.
Switches SW, SW2 for commanding rotation in the winding direction and unwinding direction (i.e., hoisting and lowering directions of the suspended load, respectively), and switches SW2 for commanding rotation speed (i.e., hoisting and lowering speeds). When the υ potentiometer 23 is operated with one handle, the switch sw, ,
One of sw2 is turned on. HU and HD are relays for hoisting and lowering a suspended load, respectively. In addition, what is shown by the code|symbol which added a or b to the code|symbol of each relay is an a contact or a b contact of each relay.

On the other hand, the inverter device 14 of the electric motor 13 has an input terminal R
, S, and T, and output variable frequency AC output to the motor 13 through output terminals U, V, and W, E is the ground terminal, and a is the starting signal self-holding. A relay terminal, b is a frequency setting signal input terminal, C is a common terminal for the control circuit, d and e are rotation direction command input terminals, 12g is a control power supply terminal, and h is a start signal input terminal. Reference numeral 23 is a frequency setting potentiometer, which can set the speed of the electric motor 13.

In this circuit, the lifting load W detected by the load detector 10 is the set load W set in the moment limiter 12. In the following cases, since the relay contact 25 is open, the relay 2M is in an inactive state, its b contact 2Mb remains closed, and its a contact 2Ma remains open. Therefore, the output from the potentiometer 23 is directly input to the frequency setting signal input terminal.

In this state, operate the handle of the operation switch to switch SW.

When turned in the direction that turns on and conducts, relay I (
Since the coil U is energized, each contact (rUa) of the inverter circuit is closed, and the C terminal of the inverter 14, the C terminal and the h terminal, the C terminal and the d terminal, and the f terminal and the tension meter 23, respectively. A conductive state is established, and the electric motor 13 rotates in a fixed direction (hereinafter, this direction will be referred to as the winding direction). This rotational speed is the maximum hoisting speed of the electric motor 13 depending on how the knob of the operation switch 24 is turned. You can freely choose up to. In addition, when the handle for each operation switch is turned in the opposite direction and the switch SW2 is turned on and becomes conductive, the coil of the relay HD is energized, so each contact HDa of the inverter circuit is closed, and the C terminal of the inverter 14 is turned on. and C terminal and h terminal, C terminal and C terminal, f
The terminal and the potentiometer 23 are brought into conduction, and the motor 13 rotates in a direction opposite to that when the switch SW is on (hereinafter, this direction will be referred to as the lowering direction). This rotational speed is also determined by the maximum hoisting (lowering) speed V of the electric motor 13 depending on how the knob is turned for each operation switch.

You can freely choose up to. Note that while the coil of relay HU is energized, the b contact HTJb connected in series with relay HD opens, and the operation of relay HD is prohibited. b contact HDb
opens, and the operation of relay HU is prohibited.

On the other hand, when the lifting load W exceeds the set load Wo, the relay contact portion closes, so the relay 2M is energized.

The a contact 2Ma closes, the b contact 2Mb opens, and the output from the potentiometer 23 is inputted to the frequency setting signal input terminal via the converter 15. This converter 15 is
The input signals are the maximum rated load W of the crane and the set load W set in the moment limiter 12. (However, WI>Wo) is outputted at a ratio CWo/W, :E times. Note that even if both the relays HU and HD are in operation, if the relay 2M is in operation, the output voltage of the frequency setting signal will be doubled by (wo /Wl). This [wo
/W+:] When the multiplied signal is input to the frequency setting signal input terminal, the electric motor 13 reaches the maximum hoisting (lowering) speed V regardless of the rotation direction. Yoshimo Cwo/w
+) The hoisting (lowering) speed becomes multiplied by v1. As shown in FIG. 2, the relationship between each speed and load is such that the output of the motor 13 is constant along the constant output curve A, that is, W,
V, = W,) X Vo = (maximum output of electric motor 13)].

---Page By setting as above, the capacity of the motor (output B) determined by [maximum load W2 x maximum speed V2] in the conventional winch, as shown by the imaginary line in Fig. 2. Compared to the above, the capacity of the electric motor 13 can be minimized, which is economical. Moreover, since the maximum speed automatically changes depending on the load, operation is easy. FIG. 3 is a diagram showing the relationship between the handle stroke of the operation switch 24 and the hoisting speed for each load. Even if the stroke is the same, the speed changes depending on the load, so the operator always needs to adjust the handle stroke at the same time. Smooth uncontrolled speed is possible within the range of . Furthermore, it is safe because it can only be operated at low speeds when the load is heavy.

In the above embodiment, the frequency setting circuit has two circuits, one directly connected and the other via a converter, but by using two or more converters with different characteristics, the moment limiter 12
By correspondingly increasing the output capability of the circuit, it is possible to have three circuits or more, in which case the speed can be more precisely controlled, making it even more economical and safe.

〔Effect of the invention〕

As described above, in the present invention, the electronic moment limiter has a function of outputting a signal every time the actual lifting load exceeds a preset set load regardless of the working radius, and The inverter device includes a circuit that directly transmits a speed control signal of the motor when there is no output of the signal generated by the electronic moment limiter, and a circuit that directly transmits the speed control signal of the motor when there is an output of the signal generated by the electronic moment limiter. Equipped with at least one circuit that converts the speed control signal of the motor at a fixed ratio and transmits it from the frequency setting potentiometer, the maximum lifting speed changes automatically according to the load, and the small-capacity motor can Can lift large loads. Therefore, according to the present invention, it is possible to reduce the capacity of the drive motor of the hoisting device. Further, as the load increases, the speed automatically becomes lower, so safe operation is ensured.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are control circuit diagrams of a hoisting motor showing an embodiment of the crane hoisting device of the present invention, and Figure 2 is a control circuit diagram of a hoisting motor using the present invention. A diagram showing an example of the relationship between the load and the hoisting speed, FIG. 3 is a diagram showing an example of the relationship between the hoisting speed and the handle stroke of the operation switch when using the present invention, and FIG. It is a front view showing the whole jib crane. 2... Hoisting winch, 12... Electronic moment limiter, 13... Electric motor, 14... Inverter device, 15... Converter, 23... Potentiometer, U
...Operation switch, HU, HD, 2M...Relay.

Claims (1)

[Scope of Claims] 1. In a crane that is equipped with an electric motor whose speed is controlled by an inverter device as a hoisting winch drive device and is also equipped with an electronic moment limiter, the electronic moment limiter can be used as a hoisting winch to control the speed regardless of the working radius. The inverter device is provided with a function of outputting a signal every time the lifting load exceeds a predetermined set load, and the inverter device is provided with a function of outputting a signal every time the lifting load exceeds a preset set load, and the inverter device is provided with a function of outputting a signal directly when the signal emitted by the electronic moment limiter is not output. one circuit that transmits a speed control signal of the motor from a frequency setting potentiometer; and a circuit that converts the speed control signal of the motor at a fixed ratio when the signal is output from the electronic moment limiter and sets the frequency. A hoisting device for a crane, characterized in that it comprises at least one circuit transmitting from a potentiometer. 2. At least one circuit converts the speed control signal of the electric motor at a fixed ratio and transmits it from the frequency setting potentiometer, converting it at a ratio between the maximum rated load of the crane and the set load of the electronic moment limiter and transmitting it. A crane hoisting device according to claim 1.