JPS6151492A - 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] 2.100 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. is mounted, a jib 5 is attached to the front part of the revolving body 1 so that it can be raised and lowered freely, and the hoisting rope 7 wound up and let out by the hoisting winch 3 is hung on a guide sheep 17 at the top of the A frame 4, Further, a plurality of prydles 18 are hung between a sheep block 19 at the top of the A frame and a prydle 18 connected to the top of the jib 5 via a pendant rope 8, and the jib 5 is raised or lowered by the operation of the hoisting winch 3. . Still, the hoisting rope 6 wound up and let out by the hoisting winch 2 is attached to a jib point sheep 20 at the top of the jib 5, a sheet 21 of the hook 9, and a different jib point sheep 22 at the top of the jib 5. 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 has been 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, the motor is operated at an output that is much lower than the rated output, which is uneconomical. 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.

[Means for solving problems]

In order to solve the above problems, the crane hoisting device of the present invention includes an electric motor whose speed is controlled by an inverter device as a drive device of the hoisting winch, and also includes an electronic moment limiter. The inverter device is equipped with an electronic moment limiter that outputs a signal every time the actual lifting load exceeds a preset load, regardless of the working radius. The present invention is characterized by comprising at least one circuit that directly transmits a frequency setting power source to the frequency setting potentiometer via a resistor when setting the frequency when there is no output of the signal emitted by the frequency setting potentiometer.

[For production]

With the above configuration, the crane hoisting device of the present invention has the following features:
The maximum speed of the hoisting winch drive motor changes automatically depending on the crane load.

〔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 functions described on page 6, 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 the 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 (not shown) which is excited by a signal generated in a range (W>Wll) exceeding the range (see figure), and 26 is the maximum load W of the lifting load W (see figure 2). This is the b contact of a relay (not shown) that is excited by a signal generated when the voltage exceeds (W>Wl). 2M is a relay that is excited when the contact 25 is closed.

Reference numeral 24 denotes an operation switch which connects the electric motor 13 to the hoisting rope 6.
Switches sw, , sw for commanding rotation in the winding direction and unwinding direction (i.e., the hoisting and hoisting directions and the hoisting and lowering directions, respectively), and the rotation speed (i.e., the hoisting and hoisting and lowering speeds). When the υ potentiometer 23 is operated using a single handle including a potentiometer 23 for commanding, one of the switches sw, , and sw2 is turned on depending on the direction of rotation of the motor. HU and HD are relays for hoisting and lowering operations of 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 the output terminals U, V, and W.E is the ground terminal, and a is the starting signal. A holding 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 an hFi start signal input terminal. A frequency setting potentiometer 23 is used to set the speed of the motor 13.

In this circuit, if the lifting load W detected by the load detector 10 is less than the set load Wo set in the moment limiter 12, the relay contact 25 is open, so the relay 2M is In the inactive state, its b contact 2Mb remains closed and its a contact 2Ma remains open. Therefore, the control power output from the control power supply terminal f is directly input to the potentiometer 23. In this state, when the handle of the operation switch 24 is operated and turned in the direction in which the switch SW is turned on and conductive, the coil of the relay HU is energized, so each contact HTJa of the inverter circuit is closed. The a terminal, the g terminal and the h terminal of the inverter 14, the C terminal and the d terminal, and the f terminal and the potentiometer 23 are in a conductive state, and the motor 13 rotates in a fixed direction (hereinafter this direction is referred to as the winding direction). do. This rotational speed is the maximum hoisting speed (■) of the electric motor 13 depending on how the handle of the operation switch 24 is turned. You can freely choose up to. In addition, when the handle of the operation switch 24 is turned in the opposite direction and the switch SW2 is turned on and becomes conductive, the coil of V-HD is energized, so that each contact of the inverter 900 circuits) [Da is closed. , the a terminal and the g terminal and the h terminal of the inverter 14, the C terminal and the C terminal, and the f terminal and the potentiometer 23 are in a conductive state, respectively, and the electric motor 1
3 rotates in the opposite direction (hereinafter this direction will be referred to as the lowering direction) from when the switch SW is on. This rotation speed also
The maximum hoisting (lowering) speed V of the electric motor 13 is determined by how the knob of the operation switch U is turned.

You can freely choose up to. Note that while the coil of relay HU is energized, the b contact HUb connected in series with relay HD opens and operation of the relay HD is prohibited. HDb is opened 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 25 closes, so the relay 2M is energized, its a contact 2Ma closes, its b contact 2Mb opens, and the control power from the control power terminal f is Power output is via potentiometer 23
It is inputted to via the resistor 15. The resistance value of this resistor 15 is determined as follows.

10 First, potentiometer 2 when the circuit from control power supply terminal f to potentiometer 23 does not pass through resistor 15
If the output voltage from the potentiometer 23 when the output voltage from the potentiometer 23 is passed through the E11 resistor 15 is R2, then the following equation holds true.

However, R1 is the maximum resistance value of the potentiometer 23, R2
indicates the resistance value of the resistor 15. That is, when the lifting load W exceeds the set load horse, the frequency setting voltage is outputted R1/(RI+R2) times less than when it does not exceed the set load. Here, the value of R2 with respect to the resistance value R1 is selected so as to satisfy the following equation.

However, Wl is the maximum lifting load of this crane. The resistance value of the resistor 15 is determined as described above.

Next, the setting of the set load Wo will be explained.

The operating speed of the hoisting motor 13 is proportional to the frequency setting voltage of the inverter 14, so from the above formula, the relationship between the speed of the hoisting motor 13 and the lifting load is as shown in Figure 2. , the output of the motor 13 is set to be constant along the constant output curve A, that is, the relationship w, x v, = Wox vo- (maximum output of the motor 13) is maintained.However, vl is the lifting load. This is the maximum speed when W exceeds the set load Wo.

By determining the set load Wo and the resistance value of the resistor 15 as described above, when the relay 2M is in operation, the output voltage of the frequency setting signal from the potentiometer 23 is set to the maximum rated load W and the moment limiter 12. The set load W that has been set. (where W+ > Wo), the output is multiplied by the ratio (Wo/W+).

Note that even if either relay HU or HD is in operation, if relay 2M is in operation, the output voltage of the frequency setting signal will be CW.
o/w, ) double. When this (Wo /W+:] multiplied signal is input to the frequency setting signal input terminal,
The electric motor 13 has a hoisting (lowering) speed v1 which is the maximum hoisting (lowering) speed vo which is also multiplied by [Wo7/Wl] in any direction of rotation.

By setting as above, as shown by the virtual line in Fig. 2, compared to the capacity of the engaged electric motor (output B) determined by [maximum load W2 x maximum speed V2] in a conventional winch, 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. Figure 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 shifting without permission is possible within this range. Furthermore, it is safe because it can only be operated at low speeds when the load is heavy.

In the above embodiment, the circuit from the control power supply terminal f of the inverter circuit to the potentiometer 23 is two circuits, one directly connected and the other via a resistor, but two or more resistors with different resistance values are used. 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 at least one device that directly transmits a frequency setting power source to a frequency setting potentiometer via a resistor when there is an output of the frequency setting potentiometer when there is no output of the signal emitted by the electronic moment limiter. Because it is equipped with a circuit, the maximum lifting speed changes automatically according to the load, and it is possible to lift heavy loads with a small-capacity electric motor.

Therefore, according to the present invention, it is possible to reduce the capacity of the drive motor of the hoisting device. In addition, as the load increases, the speed of operation is automatically reduced, ensuring safe operation.

[Brief explanation of drawings]

Figures 1(a) and 1(b) are control circuit diagrams of a hoisting motor showing an embodiment of the crane hoisting device of the present invention, and Figure 2 shows the hoisting load and hoisting when the present invention is used. Figure 3 is a diagram showing an example of the relationship between the hoisting speed and the handle stroke of the operation switch when the present invention is used. Figure 4 is an overall diagram of a general jib crane. FIG. 2... Hoisting winch, 12... Electronic moment limiter, 13... Electric motor, 14... Inverter device, 15... Resistor, 23... Potentiometer, separate...
...Operation switch, HU, HD, 2M...Relay.

Claims (1)

[Claims] In a crane equipped with an electric motor whose speed is controlled by an inverter device as a hoisting winch drive device and an electronic moment limiter, the actual lifting load is set in advance as the electronic moment limiter regardless of the working radius. The inverter device has a function of outputting a signal every time a predetermined set load is exceeded, and the inverter device is provided with a frequency setting power supply directly to the frequency setting potentiometer when the signal generated by the electronic moment limiter is not output. and at least one circuit that transmits the frequency setting power to the frequency setting potentiometer via a resistor when the signal emitted by the electronic moment limiter is output. crane hoisting device.