JPH024515B2 - - Google Patents

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. In the figure, 1 is a revolving body, and on the revolving body 1, a hoisting winch 2, a hoisting winch 3, an A-frame 4, a control panel 16, etc. are installed. A jib 5 is mounted on the front part of the revolving structure 1 so as to be able to rise and fall freely, and the hoisting rope 7 that is wound up and let out by the hoisting winch 3 is attached to a guide sheave 17 at the top of the A frame 4.
The sheave block 19 at the top of the A frame and the jib 5 are connected via the pendant rope 8.
The jib 5 is suspended by the operation of the hoisting winch 3.
is becoming undulating. Further, a hoisting rope 6 that is wound and fed out by the hoisting winch 2
is wrapped around the jib point sheave 20 on the top of the jib 5, the sheave 21 on the hook 9, and a different jib point sheave 22 on the top of the jib 5, and the end is connected to the load detector (load cell) attached to the jib 5. )
Connected to 10. 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, and is activated by the signals from the load detector 10 and the jib angle detector 11. It has the function of calculating the load and working radius, comparing them with the stored values, and outputting a signal if the values are exceeded.

In such cranes, the hoisting device handles various loads within the rated load range, but when an electric motor whose speed is controlled by an inverter is used as the drive device for the hoisting winch 2, it is possible 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, hoisting an empty hook requires the highest speed, and when the load is large, it is rarely operated at the highest speed for safety reasons. In other words, in the past, the rated output of an electric motor was determined based on the maximum speed of the maximum load with little possibility of operation, so in most cases, the motor was operated at an output considerably lower than the rated output. It is uneconomical. However, for this reason, if a motor with a small rated output is used as a drive device for a hoisting winch, safe operation becomes impossible.

[Problem to be solved by the invention]

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 is equipped with an electric motor whose speed is controlled by an inverter device as a drive device of the hoisting winch, and is equipped with an electronic moment limiter. The electronic moment limiter is provided with a function of outputting a signal when the actual lifting load exceeds a preset set load regardless of the working radius, and the one circuit that directly transmits the control power supply voltage to the frequency setting potentiometer when there is no output of the signal emitted from the limiter; The present invention is characterized in that it includes at least one circuit that transmits a control power supply voltage to a setting potentiometer via a resistor.

[Effect]

With the above configuration, the crane hoisting device of the present invention can be used to drive the hoisting winch depending on whether the actual hoisting load is less than or above the set load set in the electronic moment limiter. The maximum speed of the electric motor changes automatically, thereby making it possible to effectively utilize the output of the winch drive electric motor.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a crane hoisting device according to the present invention will be described below with reference to FIGS. 1 to 4.

The present invention includes a load detector 10, a jib angle detector 11, and an electronic moment limiter 12 shown in FIG. A function is provided to output a signal when the actual lifting load exceeds a certain preset load.

1a and 1b show the control circuit of the hoisting winch drive motor 13 (generally, a squirrel cage induction motor is used as this motor), and FIG. 1a shows the inverter circuit, Figure b shows a circuit that controls the inverter circuit. ₂₅ is a range (W>
26 is the a contact of a relay (not shown) that is excited by a signal generated when W ₀ ), and 26 is the a contact point of a relay (not shown) where the lifting load W exceeds the maximum rated load W ₁ (see Figure 2) (W > W This is the b contact of a relay (not shown) that is excited by the signal generated when ₁ ). 2
M is a relay that is excited when the contact 25 is closed.

Reference numeral 24 denotes an operation switch, which includes switches SW ₁ and SW ₂ for instructing the electric motor 13 to rotate in the winding direction and the feeding direction of the hoisting rope 6 (that is, in the hoisting direction and the hoisting down direction of the suspended load, respectively). , and a potentiometer 23 for commanding the rotational speed (i.e., winding/lowering speed). When the potentiometer 23 is operated with one handle, either switch SW ₁ or SW ₂ is turned on. Become. HU and HD are relays for lifting and lowering the 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 once rectifies the three-phase AC input from the input terminals R, S, and T, and outputs variable frequency AC output from the output terminals U,
V and W are outputs to the motor 13, E is a ground terminal, a is a starting signal self-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,
f and g are control power supply terminals, and h is a start signal input terminal. 23 is a frequency setting potentiometer, and its force input side includes one circuit directly connected to the control power terminal f via the b contact 2Mb of the relay 2M, a resistor 15, and the a of the relay 2M.
A circuit connected to a control power supply terminal f via a contact point 2Ma.

In this circuit, the load detector 10
If the lifting load W detected by is less than the set load W ₀ set in the moment limiter 12, the relay contact 25 is open, so the relay 2M is inactive, and its b contact 2Mb
remains closed, and the a contact 2Ma remains open. Therefore, the control power supply voltage 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 the switch SW ₁ is turned in the direction to turn on, the coil of the relay HU is energized, so each contact HUa of the inverter circuit is closed, and the inverter 1 is turned on.
4, the a terminal, the g terminal and the h terminal, the c terminal and the d terminal, and the f terminal and the potentiometer 23 are brought into conduction, and the electric motor 13 rotates in a fixed direction (winding direction). The rotation speed of the electric motor 1 depends on how the handle of the operation switch 24 is turned.
You can freely select up to the maximum hoisting speed _V0 of 3. Furthermore, when the handle of the operating switch 24 is turned in the opposite direction and the switch SW ₂ is turned on, the coil of the relay HD is energized, so each contact HDa of the inverter circuit is closed, and the terminals a and g of the inverter 14 and The h terminal, the c terminal and the e terminal, and the f terminal and the potentiometer 23 are brought into conduction, and the motor 13 rotates in the opposite direction (lowering direction) to that when the switch SW ₁ is on. This rotational speed can also be freely selected up to the maximum hoisting (lowering) speed V ₀ of the electric motor 13 depending on how the handle of the operating switch 24 is turned. Note that while the coil of the relay HU is energized, the b contact HUb connected in series with the relay HD opens and operation of the relay HD is prohibited. HDb opens and relay HU operation is prohibited.

On the other hand, when the lifting load W exceeds the set load _W0 , the relay contact 25 closes, so the relay 2M is energized, its a contact 2Ma closes, and its b contact 2
Mb is opened, and the control power supply voltage from the control power supply terminal f is input to the potentiometer 23 via the resistor 15. The resistance value of this resistor 15 is determined, for example, as follows.

First, the output voltage from the potentiometer 23 when the circuit from the control power supply terminal f to the potentiometer 23 does not go through the resistor 15 is E ₁ , and the output voltage from the potentiometer 23 when the circuit goes through the resistor 15 is E 1 . If the output voltage is _E2 , the following formula holds.

E ₂ =R ₁ /R ₁ +R ₂ E ₁ However, R ₁ is the maximum resistance value of the potentiometer 23, and R ₂ is the resistance value of the resistor 15. In this way, when the lifting load W exceeds the set load W ₀ ,
The frequency setting voltage output from the potentiometer 23 is higher than when the setting load is not exceeded.
The output is reduced by R ₁ /(R ₁ + R ₂ ). here,
The value of R ₂ with respect to the resistance value R ₁ is selected so as to satisfy the following equation.

R ₁ /R ₁ +R ₂ =W ₀ /W ₁ However, W ₁ is the maximum rated load of this crane.
The resistance value of the resistor 15 is determined as described above.

Next, the setting of the set load W ₀ will be explained.

The operating speed of the hoisting motor 13 is controlled by the inverter 14.
Since the frequency is proportional to the set voltage, the relationship between the speed of the hoisting motor 13 and the lifting load is as follows from the above formula:
As shown in Fig. 2, the output of the motor 13 is kept constant along the constant output curve A, that is, the relationship W ₁ ×V ₁ = W ₀ ×V ₀ = [maximum output of the motor 13] is maintained. Set. However, _V1 is the maximum speed when the lifting load W exceeds the set load _W0 .

When the set load W ₀ and the resistance value of the resistor 15 are determined as described above, the frequency setting signal output from the potentiometer 23 during the operation of the relay 2M is applied to the maximum rated load W ₁ and the moment limiter 12. The set load W ₀ (however, W ₁ >
W ₀ ) and is output as the ratio [W ₀ /W ₁ ].

Note that even if either of the relays HU and HD is in operation, if the relay 2M is in operation, the output voltage of the frequency setting signal becomes [W ₀ /W ₁ ]. This [W ₀ /
When a signal of [W ₁ ] is input to the frequency setting signal input terminal b, the electric motor 13 has a speed of [W ₀ /W ₁ ] that is lower than the maximum hoisting (lowering) speed V ₀ in any direction of rotation. The hoisting (lowering) speed is V ₁ .

With the above settings, the capacity of the electric motor 13 becomes A compared to the capacity B of the conventional motor determined by [maximum load W ₂ × maximum speed V ₂ ] in the conventional winch shown by the imaginary line in FIG. As shown in the figure, it can be minimized and 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 operating 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 can always check the handle stroke within the maximum range. This allows for smooth continuously variable speed. 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 divided into two circuits: a directly connected circuit and a circuit connected via a resistor.
Although an example of the circuit has been shown, by using two or more resistors with different resistance values and correspondingly increasing the output function of the moment limiter 12, it is also possible to make three circuits or more. The speed is then more precisely controlled, making it more economical and safer.

〔Effect of the invention〕

As described above, in the present invention, the electronic moment limiter has a function of outputting a signal when the actual lifting load exceeds a preset constant load regardless of the working radius, and The inverter device includes a circuit that directly transmits a control power supply voltage to a frequency setting potentiometer when there is no output of the signal generated from the electronic moment limiter, and a circuit that directly transmits the control power supply voltage to the frequency setting potentiometer when the signal generated from the electronic moment limiter is not output. By providing at least one circuit that transmits the control power supply voltage to the frequency setting potentiometer via a resistor when the signal is output, the maximum lifting speed is automatically changed according to the load, A small capacity electric motor can lift a large load. 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 drawings]

1a and 1b are control circuit diagrams of a hoisting motor showing an embodiment of a hoisting device for a crane according to the present invention;
The figure shows an example of the relationship between the lifting load and the hoisting speed, FIG. 3 shows an example of the relationship between the hoisting speed and the handle stroke of the operating switch when the present invention is used, and FIG. is a front view showing the entire general jib crane. 2... Hoisting winch, 12... Electronic moment limiter, 13... Electric motor, 14... Inverter device, 15... Resistor, 23... Potentiometer, 24... Operation switch, HU, HD, 2M …
...Relay, f... Control power supply terminal for the inverter device.

Claims (1)

[Claims] 1. In a crane that is equipped with an electric motor whose speed is controlled by an inverter device as the drive device of the hoisting winch and is also equipped with an electronic moment limiter, the electronic moment limiter is equipped with The inverter device is provided with a function of outputting a signal when a predetermined set load is exceeded, and the inverter device is provided with a frequency setting potentiometer when the signal is not output from the electronic moment limiter. one circuit that directly transmits the control power supply voltage to the meter; and a circuit that transmits the control power supply voltage to the frequency setting potentiometer via a resistor when the signal is output from the electronic moment limiter. A crane hoisting device comprising at least one.