JP2557422Y2 - Electric hoist - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric hoist which uses an inverter to control a hoisting speed in three stages: a fine speed, a standard speed, and a super high speed.

[0002]

2. Description of the Related Art Conventionally, a three-phase squirrel-cage induction motor has been used as a hoisting motor for an electric hoist, and a normal hoisting speed is generally a single speed. In a cargo handling operation using a single-speed electric hoist, there is a problem that workability is extremely poor, and an electric hoist capable of speed control has been strongly desired.

A hoist with a low-speed device and an inverter hoist have been developed in such a background. The hoist with a low-speed device has a configuration in which a low-speed hoisting drive unit is mechanically added to the standard speed hoisting drive unit via an electromagnetic clutch or the like, and two-stage speed control of standard speed and fine speed can be obtained. is there.

The inverter hoist controls the speed by changing the frequency supplied to the hoist motor.
The output frequency from the inverter is set in two stages, a base frequency (commercial) and a frequency higher than the base frequency (hereinafter, referred to as a high frequency), and the load of the electric hoist is calculated from the load current of the hoisting motor inside the inverter. After electrically detecting the state, a load is applied at a base frequency to operate at a standard speed, and in a no-load state, a high frequency is applied to perform a high-speed operation.

[0005]

In the prior art such as this, the structure of the body is large and the structure is complicated, and the speed set for mechanical control (for example, the standard speed and its speed). (1/8 speed).

In the latter case, there remains a problem that operability is poor. To explain this point in detail, since an electric hoist is required to have a starting torque due to its nature, a starting current of 5 to 6 times the rated current flows at the time of starting. Because of this,
In order to detect a stable load current, the starting current at the time of startup must be cut, and a load detection time of several seconds (within 5 seconds) is required until the load current is stabilized. Then, after detecting the presence or absence of a load inside the inverter, the speed is gradually shifted from the standard speed to the set high speed.

This speed change will be described with reference to FIG. In FIG. 5, the horizontal axis represents time t, and the vertical axis represents hoisting speed v. When the push button switch for operating the electric hoist is turned on, the base frequency is output from the inverter, and the electric motor for hoisting the electric hoist is accelerated to the rated speed v1.
At the same time as the operation, the no-load detection time t1 is required to detect the presence or absence of a load from the load current inside the inverter. When the inverter detects the no-load state, the output frequency of the inverter is switched from the base frequency to the high frequency, and the electric motor for hoisting the electric hoist is accelerated again to the set high speed v2.

As described above, in the latter case, it is possible to perform two-stage speed control between when the load is applied and when there is no load. However, the load state of the electric hoist is electrically detected inside the inverter. Since the speed is controlled, there is a problem that responsiveness is poor and a driver feels uncomfortable in operation. Furthermore, when the driver performs the inching operation, there is still a problem that it is difficult to switch to the high-speed operation even when there is no load. The present invention has been made to solve such problems of the prior art.

[0009]

According to the present invention, there is provided an electric hoist in which the speed of hoisting is controlled by an inverter. And a three-stage push-button switch for hoisting operation of the electric hoist, and when the first-stage contact of the push-button switch is closed, the output frequency of the inverter is reduced. The electric hoist is supplied as a frequency lower than the base frequency to the electric motor for hoisting the electric hoist, and when the second-stage contact of the push button switch is closed, the output frequency of the inverter is set as the base frequency to hoist the electric hoist. And the third-stage contact of the push-button switch is closed and the load detection mechanism detects a load less than a certain value. The, so as to supply to the hoisting motor of the electric hoist the output frequency of the inverter as a frequency higher than the base frequency, in which so as to speed control of the three stages.

[0010]

According to the above construction, when the push-button switch is operated in one step, the hoisting operation in a low speed state is enabled. When the push button switch is operated in two steps, the hoisting operation in the standard speed state is enabled. further,
When the push-button switch is operated in three steps, a mechanical load detection mechanism provided separately from the inverter detects the load state of the electric hoist, and the load detection state allows the hoist in an ultra-high speed state. Enable driving. As described above, in the electric hoist according to the present invention, three-stage speed control can be performed according to the operation of the push button switch and the load state of the electric hoist.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the electric hoist according to the present invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram of the electric hoist according to the present invention. FIG. 2 is a schematic diagram schematically showing the structure of the electric hoist of FIG. 1. FIG. 3 is a block diagram showing an internal configuration of the inverter. FIG. 4 is a hoisting characteristic curve diagram of the electric hoist of FIG.

2, the rotational force of the hoisting motor 1 which is a three-phase induction motor is transmitted to the wire drum 4 which winds the wire rope 3 after being reduced by the speed reducer 2. The wire rope 3 having one end fixed to the wire drum 4 bridges the hook block 5 in the middle thereof, and the other end is fixed to the drum case 7 via a load detection mechanism 6 described later. Reference numeral 8 denotes a hoisting electromagnetic brake, which is a known electromagnetic brake which applies an electric current to an electric motor and simultaneously excites the electric motor to release the braking, and generates a braking force by a spring as soon as the electric current is cut off.

Reference numeral 9 denotes a control box of an electric hoist in which the inverter 10 is built. Reference numeral 11 denotes an operation push button switch which is suspended from the control box 9 by a cable 12. Then, the up button SU and the down button SD of this operation push button switch 11
With this operation, the hoisting motor 1 is rotated forward to perform hoisting, and reversely rotated to perform lowering.

The internal configuration of the inverter 10 will be described with reference to FIG. 3. A three-phase commercial alternating current (3φ, AC) having a frequency of 50 Hz or 60 Hz
To a DC, a smoothing circuit 14 for smoothing the DC, an inverter 15 for converting the smoothed DC to a square wave AC output, and a phase control and frequency of the converter 13 and the inverter 15 Control circuit 16 for control
It is composed of

Reference numeral 17 denotes a frequency command volume. A command specified by the volume 17 is input to the inverter unit 15 via the control circuit 16, and the specified frequency is output from the inverter unit 15. Then, the rotation speed of the hoisting motor 1 is controlled.

Next, an electric circuit diagram of the electric hoist according to the present invention will be described with reference to FIG. The illustration of the switch mechanism and the drive mechanism for performing the traverse motion of the hoist and the traveling motion of the crane when the hoist is used for the crane is omitted. 18 is a three-phase commercial power supply (50 Hz or 60
Hz), which is connected to the electromagnetic brake 8 and the input of the inverter 10 via the emergency overwind limit switch LS2. The frequency command volume 17 is output from the output of the inverter 10.
Is supplied to the hoisting electric motor 1.

The inverter 10 includes CC, ST, F, R, S1,
Each terminal has S2, LOW, PV, FLC, FLA, etc. It has the following functions. DBR is the discharge resistance during regenerative braking. When the terminals CC and ST are short-circuited, the inverter 10
Becomes operable. When the terminals CC and F are short-circuited, a low-frequency (for example, 10 Hz) three-phase alternating current for rotating the hoisting motor 1 forward is output from the inverter 10. When the terminals CC and R are short-circuited, a low-frequency (for example, 10 Hz) three-phase alternating current for reversing the hoisting motor 1 is output from the inverter 10. When the terminals CC, F and S1 are short-circuited, the inverter 10 outputs a three-phase alternating current of a base frequency (for example, 60 Hz) for rotating the hoisting motor 1 forward. When the terminals CC, R, and S1 are short-circuited, the inverter 10 outputs a three-phase alternating current of a base frequency (for example, 60 Hz) for reversing the hoisting motor 1. When the terminals CC, F and S2 are short-circuited, the inverter 10 outputs a high-frequency (for example, 120 Hz) three-phase alternating current for rotating the hoisting motor 1 forward. When the terminals CC and R and S2 are short-circuited, a high-frequency (for example, 120 Hz) three-phase alternating current for inverting the hoisting motor 1 is output from the inverter 10. Electromagnetic contactor MC for electromagnetic brake between terminals LOW and PV
Voltage is generated only while the electromagnetic coil B is connected and the inverter 10 is outputting three-phase alternating current. The inverter between terminals FLC and FLA
10 is equipped with a protection relay RO that is short-circuited only when operation is stopped in some abnormal condition. The terminal FLC is connected to a power supply, and the electromagnetic coil of the protection relay R6 is connected between the terminal FLA and the power supply.

As a result, the protection relay R6 is energized when the inverter 10 enters an abnormal state,
The normally closed contact of the protection relay R6 connected in series between the common terminal CC of the inverter 10 and each terminal opens, and the inverter 10
The instruction to output to is interrupted.

The above-mentioned operation push button switch 11 is composed of an interlocked up button SU and a down button SD. The up button SU and the down button SD are operated in three steps, respectively, and the up button is placed in one step. Eye switch SU1, ascending second-stage switch SU2, ascending third-stage switch SU3, descending first-stage switch
SD1, Descending second-stage switch SD2 and Descending third-stage switch SD
3 contacts are provided.

The ascending first-stage switch SU1 is connected to an electromagnetic coil of a relay R3 via an overwind limit switch LS1. The electromagnetic coil of the relay R4 is connected to the first-row switch SD1. An electromagnetic coil of a relay R2 is connected to a parallel circuit of the ascending second-stage switch SU2 and the descending second-stage switch SD2. An electromagnetic coil of a relay R1 is connected to a parallel circuit of the ascending third-stage switch SU3 and the descending third-stage switch SD3.

Next, the load detection circuit will be described. A load detection mechanism 6 is connected to the normally open contact of the relay R1. The load detection mechanism 6 is constituted by, for example, a load limiter, and is provided near the fixed side of the wire rope 3 (see FIG. 2). The internal switch configuration of the load detection mechanism 6 is as follows.
The internal contact 19 is turned off when the load is heavy, and is turned on when the load is light or no load. The electromagnetic coil of the relay R5 is connected to the internal contact 19 of the load detection mechanism 6.

Next, the operation of the electric hoist configured as described above will be described. When the ascending first-stage switch SU1 is turned on, the electromagnetic coil of the relay R3 is excited, and the normally open contact of the relay R3 connected to the terminal F of the inverter 10 is closed. Thus, the terminals CC and F of the inverter 10 are short-circuited, and the inverter 10 outputs a low-frequency (for example, 10 Hz) three-phase alternating current for rotating the hoisting motor 1 forward. At the same time, a voltage is generated between the terminals LOW and PV of the inverter 10, the electromagnetic coil of the electromagnetic contactor MCB is excited, the main contact of the electromagnetic contactor MCB is closed, and the electromagnetic brake releases the braking. Therefore, the hoisting motor 1 is hoisted at a very low speed.

Similarly, when the lower first stage switch SD1 is turned on, the electromagnetic coil of the relay R4 is excited and the inverter 10 is turned on.
The normally open contact of the relay R4 connected to the terminal R of is closed.
As a result, the terminals CC and R of the inverter 10 are short-circuited, and a low-frequency (for example, 10 Hz) three-phase alternating current for reversing the hoisting motor 1 is output from the inverter 10, and the electromagnetic brake simultaneously releases the braking. Thus, the hoisting electric motor 1 is driven down at a very low speed.

Next, when the ascending second-stage switch SU2 (or the descending second-stage switch SD2) is turned on, the electromagnetic coil of the relay R2 is excited, and the normally open contact of the relay R2 connected to the terminal S1 of the inverter 10 is turned on. Close. This allows the inverter
Short circuit between terminals CC, F (or R) and S1 of 10
10 outputs a three-phase alternating current having a base frequency (for example, 60 Hz) for rotating the hoisting motor 1 forward (or reverse). As a result, the hoisting motor 1 is hoisted (or lowered) at the standard speed.

Next, when the ascending third-stage switch SU3 (or the descending third-stage switch SD3) is turned on, the electromagnetic coil of the relay R1 is excited, and the normally open contact of the relay R1 provided in the load detection circuit section is closed. I do.

At this time, if the load state of the electric hoist is light load or no load, the internal contact 19 of the load detecting mechanism is used.
Is closed, the electromagnetic coil of the relay R5 is excited, the normally open contact of the relay R5 connected to the terminal S2 of the inverter 10 is closed, and the normally closed contact connected to the terminal S1 is open. This allows the terminals CC and F (or R)
And S2 are short-circuited, and the inverter 10 outputs a high frequency (for example, 120 Hz) for rotating the hoisting motor 1 forward (or reverse).
Is output. Thereby, the hoisting motor 1
Is driven up (or down) at a very high speed.

Such three-stage speed control will be described with reference to a hoisting characteristic curve diagram of FIG. In FIG. 4, the horizontal axis represents time t, and the vertical axis represents hoisting speed v. When the ascending first-stage switch SU1 (or the descending first-stage switch SD1) is turned on, the operation is performed at a very slow speed v0 as shown by the curve. In addition, ascending second stage switch SU2 (or descending second stage switch
When SD2) is input, operation is performed at the standard speed v1 as shown by the curve. Then, if the ascending third-stage switch SU3 (or the descending third-stage switch SD3) is turned on and the load state of the electric hoist is light or no load, the super high speed v2 as shown by the curve is used. Driving.

[0028]

As described in detail above, when the operating push button switch is operated in one stage, the winding at the preset fine speed state is performed irrespective of the load state of the electric hoist. When the push-button switch is operated in two steps, the hoisting operation at a standard speed set in advance is enabled. Since the operation at an ultra-high speed set in advance according to the load state of the hoist is enabled, a speed according to the work content can be obtained.

In addition, the three-step operation from a very low speed to a very high speed can be performed smoothly and safely with a single button operation, so that the inching operation is not required at the time of a fine positioning operation, and the load can be reliably secured. Can be transported to a fixed position. When the load hung on the electric hoist is a light load less than a certain value, the operation can be performed at an extremely high speed, so that the work efficiency is remarkably improved. Further, since the load state of the electric hoist is performed by a mechanical load detection mechanism provided separately from the inverter, the operation responsiveness is excellent.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an electric hoist according to the present invention.

FIG. 2 is a schematic diagram schematically showing the structure of the electric hoist of FIG. 1;

FIG. 3 is a block diagram showing an internal configuration of the inverter.

FIG. 4 is a hoisting characteristic curve diagram of the electric hoist of FIG.

FIG. 5 is a hoisting characteristic curve diagram of a conventional electric hoist.

[Explanation of symbols]

 1 Hoisting motor 6 Load detection mechanism 10 Inverter 11 Operation push button switch

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location B66D 1/46 B66D 1/46 F H02P 7/63 302 H02P 7/63 302M

Claims (1)

(57) [Scope of request for utility model registration] 1. An electric hoist in which a hoist speed is controlled by an inverter, a load detecting mechanism for mechanically detecting a load state applied to the electric hoist, and a hoisting operation of the electric hoist. When the first-stage contact of the push-button switch is closed, the output frequency of the inverter is set to a frequency lower than the base frequency and supplied to the electric motor for hoisting the electric hoist. When the second-stage contact of the push button switch is closed, the output frequency of the inverter is supplied as a base frequency to the electric motor for hoisting the electric hoist, and the third-stage contact of the push button switch is closed. And, when the load detection mechanism detects a load less than a certain value, the output frequency of the inverter is set to a frequency higher than a base frequency. The electric hoist is supplied to a motor for hoisting the electric hoist to perform three-stage speed control.