JPH0717345B2 - Variable speed hoist - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control system for a variable speed hoisting machine equipped with an inverter as a variable speed control device for a hoisting motor.

[Conventional technology]

FIG. 4 is a circuit diagram of a conventional variable speed hoisting machine equivalent to that shown in, for example, Japanese Patent Laid-Open No. 59-203097. In FIG. 4, (1) is an inverter to which a three-phase AC power supply is supplied. Wire R, S,
It is supplied from T and outputs a three-phase alternating current in a phase sequence according to a forward rotation or reverse rotation command (not shown). The frequency of this three-phase alternating current is determined by the frequency selection input. When the low frequency selection input terminal L and the common terminal G are short-circuited, 60Hz,
120H when the high frequency selection input terminal H and the common terminal G are short-circuited
Three-phase alternating current of z is output. If neither the low frequency selection input terminal L nor the high frequency selection input terminal H is short-circuited with the common terminal G, the three-phase alternating current is not output. (2) is a hoisting motor, which rotates in a rotating direction and at a speed corresponding to the phase sequence and frequency of the three-phase alternating current output from the inverter unit (1). (3) is a load cell, which is hung from the main body of the hoisting machine and the other end of which is connected to one end of a wire rope wound around a winding cylinder. The load cell is hung from the hanging center part of the wire rope via a hook. The analog signal voltage corresponding to the load of the suspended load is output. A load cell controller (4) opens and closes the relay contacts (4a), (4b1), (4b2) according to the analog signal voltage obtained from the load cell (3). When the load cell (3) detects a load of 50% or more of the rated load, the contact (4a) is closed and the contact (4b1) is opened. When a load exceeding 100% of the rated load is detected, the contact (4b2) is opened.

Next, the operation will be described. When the load is less than 50% of the rating, the relay contact of the load cell controller (4) is open at (4a) and closed at (4b1) and (4b2), and the terminals H and G of the inverter (1) are closed. The two are short-circuited, and the inverter (1) is 120
3-phase AC of Hz is output to the hoisting motor (2) for high speed operation.

When the load is 50% or more and less than 100% of the rating, the relay contacts of the load cell controller (4) are closed (4a) and (4b2), (4
b1) is opened, the terminals L and G of the inverter (1) are short-circuited, and the inverter (1) outputs a three-phase alternating current of 60 Hz to the hoisting motor (2) to operate at low speed.

When the load is 100% or more, the relay contact (4a) of the load cell controller (4) is closed, (4b1) and (4b2) are open, and the terminals L and H of the inverter (1) are either Is not short-circuited with the terminal G, the inverter (1) does not output the three-phase AC and the hoisting motor (2) stops rotating.

[Problems to be Solved by the Invention]

Since the conventional variable speed hoisting machine is configured as described above, the load cell must be mounted between the wire rope and the hoisting machine body, which is expensive and at the same time the hoisting machine is originally required to carry a suspended load. There is a problem that it is not possible to wind up to the upper limit position where it can be wound up, and further, it is necessary to move the upper limit position control device downward.

The present invention is made to solve the above problems, the device can be inexpensive, can be used without lowering the upper limit position where the hoist can originally hoist a suspended load, the upper limit position Variable speed winding that can lower the maximum allowable speed when suspending the rated load, that is, faster than the rated speed, only when the load is light and close to no load, without requiring the lowering of the limiting device. The purpose is to get a good job.

[Means for Solving the Problems]

The variable speed hoisting machine according to the present invention is an inverter capable of outputting a first reference frequency and a second reference frequency higher than the first reference frequency, and the rotation speed is controlled by the output of this inverter. The hoisting motor, the detection means for detecting the rotation speed of the hoisting motor, the hoisting motor
When the rotation speed detected by the detection means is equal to or lower than the preset load judgment reference speed during the unwinding rotation at the reference frequency, the switching means switches the output of the inverter to the second reference frequency. It is a thing.

[Action]

The variable speed hoisting machine according to the present invention uses the hoisting motor at the first reference frequency of the inverter capable of outputting the first reference frequency and the second reference frequency higher than the first reference frequency. If the rotation speed detected by the detection means is equal to or lower than the preset load judgment reference speed during the unwinding rotation, the output of the inverter is switched to the second reference frequency by the switching means.

〔Example〕

An embodiment of the present invention will be described below. In FIG. 1, (1) is an inverter, and three-phase AC power is supplied from R, S, and T. (2) is a hoisting motor, which rotates in a rotating direction and at a speed corresponding to the phase sequence and frequency of the three-phase alternating current output from the inverter (1). (5) is a brake, which locks the hoisting motor (2) so that it does not rotate when it is not energized, and releases it so that the hoisting motor (2) can freely rotate when it is energized. RBu is a normally open pushbutton switch for hoisting operation, and PBd is a normally open pushbutton switch for lowering operation. The push-button switches PBu and PBd are constructed so that they cannot be pushed simultaneously by a mechanical interlock. (6) is a coil of an electromagnetic relay that opens and closes a normally open contact (6a1) that instructs the inverter (1) to output a three-phase alternating current in a phase sequence in which the hoisting motor (2) rotates in the hoisting direction. Reference numeral (7) is a coil of an electromagnetic relay, and at the same time as opening and closing the normally open contact (7a1) that instructs the inverter (1) to output three-phase alternating current in the phase order in which the hoisting motor (2) rotates in the lowering direction. Open contact (7a2)
Open and close. Reference numeral (8) is a coil of an electromagnetic relay, which is energized while the inverter (1) outputs a three-phase alternating current and opens and closes a normally open contact (8a) for energizing the brake (5).
Reference numeral (9) is a rotary encoder, the input shaft of which is coupled to the output shaft of the hoisting motor (2) and rotates simultaneously, and is composed of A phase and B phase which represent the direction and amount of rotation of the hoisting motor (2). Outputs a two-phase signal. Reference numeral (10) is a coil of an electromagnetic relay, which is energized while the inverter (1) outputs a three-phase alternating current having a reference frequency to close the normally open contact (10a). (1
1) is a frequency instruction switching device, which inputs a two-phase signal from the rotary encoder (9), closes the normally open contact (7a2), and also closes the normally open contact (10a), and after a certain time. When the rotation speed of the hoisting motor (2) does not exceed the predetermined load judgment reference speed, the normally open contact (11a) is closed,
Open the normally closed contact (11b).

Next, the operation will be described with reference to FIGS. At time t ₁ , when the push button switch PBd is pressed, the electromagnetic relay coil (7) is energized and the normally open contacts (7a1), (7a2)
Closes. Since the normally closed contact (11b) is closed and the normally open contact (11a) is open, the low frequency (60Hz) selection input terminal L and the common terminal G of the inverter (1) are short-circuited and the low frequency is selected. , The inverter (1) starts increasing the frequency from OHz to 60Hz with a preset slope. When the frequency reaches f ₁ at time t ₂ , the inverter (1) starts output to the hoisting motor (2) and at the same time energizes the electromagnetic relay coil (8), the normally open contact (8a) closes. The brake (5) is energized, the hoisting motor (2) is opened, and the hoisting motor (2) begins to rotate in the lowering direction to increase the speed. At time t ₃ , when 60Hz is reached, the inverter (1) will turn on the normally open contact (10
As a) is closed, the frequency increase stops, so
The hoisting motor (2) is operated at a constant speed at a low speed. The rotation speed S2 of the hoisting motor (2) at this time increases as the ratio of the load to the rated load increases. If the load is light and close to no load, and the ratio of the load to the rated load is smaller than P1, the rotation speed S2 of the hoist motor (2)
However, the frequency instruction switching device (11) closes the normally open contact (11a) and opens the normally closed contact (11b) at the time t ₄ when a predetermined time elapses because the predetermined reference speed S1 is not exceeded. To do. Then, the inverter (1) is short-circuited between the high frequency (120 Hz) selection input terminal H and the common terminal G, and the high frequency is selected.
The frequency starts increasing again up to 120 Hz at a preset inclination, and the hoisting motor (2) speeds up again. When it reaches 120 Hz at time t ₅ , the inverter (1) stops increasing in frequency, so that the hoisting motor (2) is operated at a constant speed at a high speed. When stop pressing the push-button switch PBd at time t _6, the electromagnetic relay coil (7) is de-energized, the normally open contact (7a1), is (7a2) opens. Then, the inverter (1) starts decreasing the frequency until it reaches OHz with a preset inclination, and the frequency instruction switching device (11) opens the normally open contact (11a) and closes the normally closed contact (11b) to close the inverter ( Low frequency (60Hz) selection input terminal L and common terminal G of 1)
Short circuit. At time t ₇ , when the frequency f ₁ is reached, the inverter (1) stops the output to the hoisting motor (2) and at the same time deactivates the electromagnetic relay coil (8), so that the normally open contact (8a) The opening brake (5) is de-energized, and the hoisting motor (2) is locked and stopped.

When the push button switch PBu is pressed, the electromagnetic relay coil (6) is energized and the hoisting motor (2) rotates in the hoisting direction, and the frequency instruction switching device (11) opens the normally open contact (11).
Opening a) and closing the normally closed contact (11b), the inverter (1) is selected at a low frequency, and even if the load is light and near no load, it does not enter into high speed operation, except for other operations. Is similar to the case where the push button switch PBd is pressed.

In addition, although the rotary encoder is provided as the rotation detector of the hoisting motor (2) in the above embodiment, a finger speed generator may be used. In addition, the push button switch is a multi-step push type, and the frequency selection of the inverter is 2 for high frequency and low frequency.
It is possible to select not only stages but also more stages of frequency selection.

Further, the high-speed operation without load has been described, but the high-speed operation with light load may be used.

Further, in the above-described embodiment, the rotation speed of the hoisting motor during the unwinding operation at the reference frequency is judged not to exceed the preset load judgment reference speed after receiving the reference frequency arrival signal from the inverter. Although it is shown that the rotation speed of the hoisting motor at the time of the lowering operation at the reference frequency as in the other invention does not exceed the preset load judgment reference speed, As shown in FIG. 3, it may be performed after exceeding the acceleration completion determination reference speed S3 which is set lower than the load determination reference speed in advance. In this case, the frequency instruction switching device (1) inputs the two-phase signal from the rotary encoder (9), the normally open contact (7a2) is closed, and the rotation speed of the hoisting motor (2) is the acceleration completion judgment criterion. If the rotation speed of the hoisting motor (2) does not exceed the load judgment reference speed after a certain period of time from the judgment that the speed has exceeded the speed, the normally open contact (11a) is closed and the normally closed contact ( Open 11b).

Further, as in another invention, it is determined that the rotation speed of the hoisting motor during the hoisting operation at the reference frequency does not exceed the preset load judgment reference speed. You may make it after it becomes small. In this case, the frequency instruction switching device (11) inputs the two-phase signal from the rotary encoder (9), the normally open contact (7a2) is closed, and the increase in the rotation speed of the hoisting motor (2) stops and changes. When it is determined that the amount has become smaller,
When the rotation speed of the hoisting motor (2) does not exceed the load judgment reference speed, the normally open contact (11a) is closed and the normally closed contact (1
Open 1b).

It should be noted that the method of receiving the reference frequency arrival signal from the above-mentioned inverter, the method of judging that the rotation speed of the hoisting motor has exceeded the acceleration completion judgment reference speed, and the increase in the rotation speed of the hoisting motor is subdued and the change amount is small The method of determining the failure may be carried out alone or in combination.

[Advantages of the Invention] As described above, according to the present invention, an inverter capable of outputting the first reference frequency and the second reference frequency higher than the first reference frequency, and rotating with the output of this inverter The hoisting motor whose speed is controlled, the detection means for detecting the rotational speed of the hoisting motor, and the hoisting motor are the first
When the rotation speed detected by the detection means is equal to or lower than the preset load judgment reference speed during the unwinding rotation at the reference frequency, the switching means switches the output of the inverter to the second reference frequency. Therefore, the device can be inexpensive, can be used without lowering the upper limit position where the hoist can hoist the suspended load, and it is not necessary to move the upper limit position limiting device to the lower side. Only when the load is close to no load, it is possible to obtain a variable speed hoisting machine with good workability that can lower the maximum allowable speed when suspending the rated load, that is, a speed faster than the rated speed.

According to another aspect of the invention, the switching means, after receiving the first reference frequency from the inverter, at a predetermined time,
When the rotation speed is equal to or lower than the load judgment reference speed, the output of the inverter is switched to the second reference frequency, so it can be easily determined that the hoisting motor is operating at the reference frequency, and hoisting during acceleration. There is an effect that it is possible to obtain a variable speed hoisting machine that does not erroneously determine that the load is light when the rotation speed of the motor is still low.

According to still another aspect of the invention, the switching means is configured such that, after the rotation speed exceeds the acceleration completion determination reference speed which is set lower than the load determination reference speed, the rotation speed is the load determination reference speed after a predetermined time elapses. In the following cases, the output of the inverter was switched to the second reference frequency, so it was confirmed that the rotation speed of the hoist motor was sufficiently accelerated at the reference frequency, and that the load was light when the rotation speed had settled. There is an effect that a variable speed hoisting machine that can make a reliable judgment can be obtained.

According to still another aspect of the invention, the switching means sets the output of the inverter to the second reference frequency when the amount of change in the rotation speed of the hoisting motor becomes small and the rotation speed is equal to or lower than the load determination reference speed. Since it is switched, the speed of the hoisting motor is sufficiently accelerated at the reference frequency, and when it is confirmed to be stable, it is possible to obtain a variable speed hoisting machine that can surely and quickly determine that the load is light. is there.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an operation characteristic diagram thereof, and FIG. 3 is a characteristic diagram showing a relationship between a load at a reference frequency and a hoisting speed of a hoisting motor, FIG. 4 is a circuit diagram showing a conventional device. In the figure, (1) is an inverter, (2) is a hoisting motor,
(5) is a brake, (9) is a rotary encoder,
(11) is a frequency instruction switching device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] 1. An inverter capable of outputting a first reference frequency and a second reference frequency higher than the first reference frequency, a hoisting motor whose rotation speed is controlled by the output of the inverter, Detecting means for detecting the rotation speed of the hoisting motor, and when the hoisting motor is being rotated under the first reference frequency, the rotational speed detected by the detecting means is equal to or lower than a preset load judgment reference speed. In this case, the variable speed hoisting machine is provided with a switching means for switching the output of the inverter to the second reference frequency. 2. The switching means, when a predetermined time has elapsed after receiving the first reference frequency from the inverter,
2. The variable speed hoisting machine according to claim 1, wherein the output of the inverter is switched to the second reference frequency when the rotation speed is equal to or lower than the load judgment reference speed. 3. The switching means, when a predetermined time elapses after the rotation speed exceeds an acceleration completion determination reference speed set lower than the load determination reference speed, the rotation speed is equal to or lower than the load determination reference speed. In this case, the variable speed hoisting machine according to claim 1, wherein the output of the inverter is switched to the second reference frequency. 4. The switching means outputs the output of the inverter to the second reference when the rotation speed of the hoisting motor is smaller than the load judgment reference speed when the change amount of the rotation speed is small. The variable speed hoisting machine according to claim 1, wherein the frequency is switched.