JPH0575281U - Electric hoist - Google Patents

Abstract

(57) [Abstract] [Purpose] The size of the aircraft is reduced to simplify the structure, and
Allow the hoisting speed to be controlled in three steps. [Structure] A load detection mechanism 6 for detecting a load state applied to an electric hoist is provided, and a push button switch 11 for hoisting operation of the electric hoist is operated in three stages. When the first-stage contact of the push button switch 11 is closed, a frequency lower than the base frequency is supplied to the hoisting motor 1,
If the second contact of push button switch 11 is closed,
When the base frequency is supplied to the hoisting motor 1, the third contact of the pushbutton switch 11 is closed, and the load detection mechanism 6 detects a load below a certain value, a frequency higher than the base frequency. Is supplied to the hoisting electric motor 1. With this, three-stage speed control can be performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electric hoist which uses an inverter to control a hoisting speed in three stages of a fine speed, a standard speed and an ultrahigh speed.

[0002]

[Prior Art]

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

The hoist with a fine speed device and the inverter hoist are developed under such a background. The hoist with fine speed device has a structure in which a fine speed hoisting drive unit is mechanically added to the standard speed hoisting drive unit via an electromagnetic clutch, etc., 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 hoisting motor, and the output frequency from the inverter is a base frequency (commercial) and a frequency higher than the base frequency (hereinafter, (High frequency)), the load condition of the electric hoist is electrically detected from the load current of the hoisting motor inside the inverter, and then the base frequency is applied to the standard condition in the load condition. There is one that operates at high speed and applies a high frequency in a no-load state to perform high speed operation.

[0005]

[Problems to be solved by the device]

 In the former one of such conventional techniques, the structure of the airframe is large and the structure is complicated, and only the speed set for mechanical control (for example, standard speed and 1/8 speed thereof) can be obtained. There is a problem that can not be done.

Further, the latter one has a problem that the operability is poor. Explaining this point in detail, since the electric hoist requires a starting torque due to its nature, a starting current 5 to 6 times the rated current flows at the time of starting. Therefore, in order to detect a stable load current, it is necessary to cut off the starting current at the time of startup, and it takes several seconds (within 5 seconds) for load detection until the load current stabilizes. Then, after detecting the presence or absence of a load inside the inverter, the speed gradually shifts from the standard speed to the set high speed.

This change in speed 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 pushbutton 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 condition, the output frequency of the inverter is switched from the base frequency to the high frequency, and the hoisting electric motor of the electric hoist is accelerated again to the set high speed v2.

As described above, in the latter one, although it is possible to perform two-stage speed control with load and without load, the load state of the electric hoist is electrically detected inside the inverter. Since the speed is controlled by using the speed control, the responsiveness is poor and there is a problem that the driver feels uncomfortable in operation. Furthermore, when the driver performs an inching operation, there remains a problem that it is difficult to switch to high-speed operation even when there is no load. The present invention has been made as a solution task to eliminate such problems of the conventional technology.

[0009]

[Means for Solving the Problems]

 As a means for solving the above problems, the present invention provides an electric hoist in which a hoisting speed is controlled by an inverter, and includes a load detection mechanism that mechanically detects a load state applied to the electric hoist. At the same time, the pushbutton switch for hoisting operation of the electric hoist is operated in three steps, and when the first contact point of the pushbutton switch is closed, the output frequency of the inverter is set to a frequency lower than the base frequency. When the second stage contact of the pushbutton switch is closed, it is supplied to the hoisting electric motor of the electric hoist and is supplied to the hoisting electric motor of the electric hoist with the output frequency of the inverter as the base frequency. When the third contact point of the push button switch is closed and the load detection mechanism detects a load less than a certain value, the inverter It is supplied to the electric Hui hoisting motor strike the output frequency as a frequency higher than the base frequency, in which so as to speed control of the three stages.

[0010]

[Action]

 With the above configuration, when the push button switch is operated by one step, the hoisting operation can be performed in the fine speed state. When the push button switch is operated in two steps, hoisting operation at standard speed is possible. Furthermore, when the pushbutton switch is operated in three stages, the mechanical load detection mechanism provided separately from the inverter detects the load state of the electric hoist, and this load detection state causes an ultra high speed state. Allows hoisting operation. As described above, in the electric hoist according to the present invention, the speed can be controlled in three stages depending on the operation of the push button switch and the load state of the electric hoist.

[0011]

【Example】

 An embodiment of the electric hoist according to the present invention will be described below with reference to 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 shown in FIG. FIG. 3 is a block diagram showing the internal configuration of the inverter. FIG. 4 is a winding characteristic curve diagram relating to the electric hoist of FIG. 1.

To explain the structure with reference to FIG. 2, the rotational force of the hoisting electric motor 1 which is a three-phase induction motor is reduced by the speed reducer 2 and then transmitted to the wire drum 4 for winding the wire rope 3. The wire rope 3 having one end fixed to the wire drum 4 spans a 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 is an electromagnetic brake for hoisting, which is a known one in which a current is passed through the electric motor and, at the same time, it is excited to release the braking, and when the current is cut off, a spring immediately generates a braking force.

Reference numeral 9 is an electric hoist control box having an inverter 10 built-in. Reference numeral 11 is a push button switch for operation which is suspended from the control box 9 by a cable 12. Then, by operating the ascending button SU and the descending button SD of the operation push button switch 11, the hoisting electric motor 1 is normally rotated to wind up and reversely to be wound down.

The internal configuration of the inverter 10 will be described with reference to FIG. 3. A converter section 13 for converting three-phase commercial alternating current (3φ, AC) having a frequency of 50 Hz or 60 Hz into direct current, and a smoothing circuit 14 for smoothing this direct current, The inverter section 15 for converting the smoothed direct current into a square wave alternating current output, and the converter section 13 and the control circuit 16 for controlling the phase and frequency of the inverter section 15 are provided.

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

Next, a circuit diagram of the electric hoist according to the present invention will be described with reference to FIG. Illustration of the switch mechanism and drive mechanism for the traverse movement of the hoist and the traveling movement of the crane when the hoist is used for a crane is omitted. Reference numeral 18 is a three-phase commercial power supply (50 Hz or 60 Hz), which is connected to the electromagnetic brake 8 and the input part of the inverter 10 via the emergency overwinding limit switch LS2. From the output section of the inverter 10, the frequency designated by the frequency command volume 17 is supplied to the hoisting electric motor 1.

The inverter 10 has terminals such as CC, ST, F, R, S1, S2, LOW, PV, FLC, and FLA, and has the following functions. DBR is the discharge resistance during regenerative braking. When the terminals CC and ST are short-circuited, the inverter 10 is ready for operation. When the terminals CC and F are short-circuited, the inverter 10 outputs a low-frequency (for example, 10 Hz) three-phase alternating current that normally rotates the hoisting motor 1. When the terminals CC and R are short-circuited, the inverter 10 outputs a low-frequency (for example, 10 Hz) three-phase AC that reverses the hoisting motor 1. When the terminals CC, F, and S1 are short-circuited, the inverter 10 outputs a three-phase alternating current having a base frequency (for example, 60 Hz) that normally rotates the hoisting motor 1. When the terminals CC, R, and S1 are short-circuited, the inverter 10 outputs a three-phase alternating current having a base frequency (for example, 60 Hz) that reverses the hoisting motor 1. When the terminals CC, F, and S2 are short-circuited, the inverter 10 outputs a three-phase alternating current having a high frequency (for example, 120 Hz) that normally rotates the hoisting motor 1. When the terminals CC, R, and S2 are short-circuited, the inverter 10 outputs a three-phase alternating current with a high frequency (for example, 120 Hz) that reverses the hoisting motor 1. The electromagnetic coil of the electromagnetic contactor MCB for electromagnetic brake is connected between the terminal LOW and PV, and voltage is generated only while the three-phase AC is output from the inverter 10. In the inverter between the terminals FLC and FLA, there is provided a protection relay RO that is short-circuited only when the operation of the inverter 10 is stopped due to some abnormal condition. The terminal FL C is connected to the power supply, and the electromagnetic coil of the protection relay R6 is connected between the terminal FL A and the power supply.

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

Further, the above-mentioned operation push button switch 11 is composed of an interlocked ascending button SU and descending button SD, and the ascending button SU and descending button SD are respectively operated in three steps, and ascending one step. It is provided with each contact of an eye switch SU1, an ascending second stage switch SU2, an ascending third stage switch SU3, a descending first stage switch SD1, a descending second stage switch SD2 and a descending third stage switch SD3.

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

Next, the load detection circuit section will be described. The load detection mechanism 6 is connected to the normally open contact of the relay R1. The load detection mechanism 6 is composed of, for example, a load limiter or the like, 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 composed of on / off control contacts that turn off the internal contact 19 during heavy load and turn on during light load 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 thus configured 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. As a result, 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 that normally rotates the hoisting motor 1. At the same time, a voltage is generated between the terminal LOW and PV of the inverter 10, the electromagnetic coil of the electromagnetic contactor MCB for electromagnetic brake is excited, the main contact of the electromagnetic contactor MCB is closed, and the electromagnetic brake releases the braking. Therefore, the hoisting electric motor 1 is hoisted at a very low speed.

Similarly, when the descending first stage switch SD1 is turned on, the electromagnetic coil of the relay R4 is excited and the normally open contact of the relay R4 connected to the terminal R of the inverter 10 is closed. As a result, the terminals CC and R of the inverter 10 are short-circuited, and the inverter 10 outputs a low-frequency (for example, 10 Hz) three-phase alternating current that reverses the hoisting motor 1, and at the same time the electromagnetic brake releases the braking. Then, the hoisting electric motor 1 is hoisted 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 opened. Make a circuit. As a result, the terminals CC and F (or R) and S1 of the inverter 10 are short-circuited, and from the inverter 10, a three-phase alternating current with a base frequency (for example, 60 Hz) that causes the hoisting motor 1 to rotate normally (or reverse). Is output. As a result, the hoisting motor 1 is hoisted (or hoisted) 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. To do.

At this time, if the load condition of the electric hoist is light load or no load, the internal contact 19 of the load detection mechanism is closed, the electromagnetic coil of the relay R5 is excited, and the terminal S2 of the inverter 10 is excited. The normally open contact of the relay R5 connected to is closed and the normally closed contact of the terminal S1 is opened. As a result, the terminals CC and F (or R) of the inverter 10 and S2 are short-circuited, and a high-frequency (for example, 120 Hz) three-phase AC that causes the hoisting motor 1 to rotate normally (or reverse) is generated from the inverter 10. Is output. As a result, the hoisting electric motor 1 is hoisted (or hoisted) at a very high speed.

Such three-stage speed control will be described with reference to the winding 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, operation is performed at the fine speed v0 as shown by the curve. When the ascending second-stage switch SU2 (or the descending second-stage switch SD2) is turned on, operation is performed at the standard speed v1 shown by the curve. Then, if the ascending 3rd stage switch SU3 (or the descending 3rd stage switch SD3) is turned on and the load condition of the electric hoist is light load or no load, at the super high speed v2 shown in the curve. Drive.

[0028]

[Effect of the device]

 As described in detail above, this invention makes it possible to perform hoisting operation at a preset fine speed state regardless of the load state of the electric hoist when the pushbutton switch for operation is operated in one stage. When the pushbutton switch is operated in two steps, hoisting operation is possible at the standard speed set in advance, and when the pushbutton switch is operated in three steps, the load condition of the electric hoist Since it is possible to operate at a very high speed set in advance, it is possible to obtain a speed according to the work content.

In addition, since three-step operation from fine speed to ultra-high speed can be performed smoothly and safely with one button operation, there is no need for inching operation during fine positioning work, and the suspended load can be secured. In addition, it can be transported to a fixed position. When the load suspended on the electric hoist is less than a certain value, the work efficiency can be remarkably improved because the operation can be performed at an extremely high speed. Furthermore, since the load of the electric hoist is detected by a mechanical load detection mechanism that is provided separately from the inverter, the operation response is excellent.

[Brief description of 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 shown in FIG.

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

4 is a hoisting characteristic curve diagram relating to the electric hoist of FIG. 1. FIG.

FIG. 5 is a winding characteristic curve diagram relating to an electric hoist of a conventional example.

[Explanation of symbols]

 1 Hoisting motor 6 Load detection mechanism 10 Inverter 11 Pushbutton switch for operation

Claims (1)

[Scope of utility model registration request] 1. An electric hoist configured to control a hoisting speed by an inverter, comprises a load detection mechanism for mechanically detecting a load state applied to the electric hoist, and hoisting operation of the electric hoist. When the push button switch for the electric switch is operated in three steps and the first contact of the push button switch is closed, the output frequency of the inverter is supplied to the hoisting electric motor of the electric hoist as a frequency lower than the base frequency. When the second-stage contact of the pushbutton switch is closed, the output frequency of the inverter is used as the base frequency to supply the hoisting electric motor of the electric hoist, and the third-stage contact of the pushbutton switch is closed. In addition, when the load detection mechanism detects a load below a certain value, the output frequency of the inverter is set to a frequency higher than the base frequency. Then, the electric hoist is configured to be supplied to the hoisting electric motor of the electric hoist so as to perform speed control in three stages.