JP2002291269A - Braking device for flywheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device capable of safely and securely stopping, in a short period of time, a flywheel of a forging press at the time of the stop operation, not through mechanical braking but through electrical braking. SOLUTION: A braking circuit 12 is provided in parallel at a power supply circuit which supplies power from a switchboard 11 to a motor 5 that drives a flywheel 2 of a forging press 1, to which braking circuit alternate current power is supplied from the power line when power supply to the motor 5 through the power supply circuit is cut off at the time of stopping operation, which alternate current power is then converted into direct current power and supplied to the motor 5, thereby causing the magnetic field produced by the direct current to electrically brake the rotation of the flywheel 2 connected to the motor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flywheel braking device for a forging press.

[0002]

2. Description of the Related Art A forging press is a press machine for lowering a ram into a mold placed on a machine bed to press and deform a material in the mold to forge a metal material as a product. A flywheel is always provided on the extension of the main shaft that moves the cylinder up and down with the crankshaft. This flywheel operates the ram from ascending to descending without stopping the rotation of the main shaft during continuous processing of a metal material into a product, thereby reducing the ram from descending to ascending.
This is required to suppress the power consumption of the motor required for the molding operation per turn as small as possible, and the power consumption is effectively used by accumulating rotational energy in the flywheel.

[0003] A forging press apparatus which uses such a flywheel to effectively use power consumption is provided by:
When the operation of forging is completed on a daily basis or after a series of forging operations, the power is cut off and the device is stopped. However, the rotation of the flywheel is forcibly stopped. Flywheel brakes are generally provided. In this flywheel brake, the lining is pressed against the flywheel by an air cylinder, and the rotation is stopped by mechanical frictional force.

[0004]

However, the flywheel of the forging press has a large mass and a large rotary inertia, so that turning off the power supply to the motor for driving the flywheel requires several tens of minutes due to the rotational energy held by the motor. It takes a considerable amount of time to continue idling and stop naturally. If the flywheel keeps spinning even after the work is completed, there will be dangerous situations that may cause unexpected situations such as accidents, so it is necessary to forcibly stop so as not to leave such situations .

As described above, the forging press apparatus employs mechanical braking means using a flywheel brake as a means for forcibly stopping the flywheel, but the brake lining has a long length. Wear out over time and must be replaced. In addition, while the flywheel is large, the flywheel brake is provided as an auxiliary only for stopping braking at the end of driving, so the braking force is small, and it takes about 30 to 30 to
A relatively long braking time of about 40 seconds is required. Further, in the case of a mechanical brake, since the brake means is pressed against the flywheel from one side, a bending moment is added to the main shaft of the flywheel, which may adversely affect the bearing of the main shaft.

[0006]

According to the present invention, as a means for solving the above-mentioned problems, a power supply circuit for supplying power to an electric motor for rotatingly driving a main shaft to which a flywheel of a forging press is connected is provided. When the power is cut off by the switch signal, power is input from the power supply line by the signal, the AC power is converted into DC power, and a braking circuit that supplies the DC power to the stator of the motor to brake the motor. A power supply switch for inputting power to the braking circuit, a transformer for adjusting the impedance of the circuit, and a rectifying circuit using a diode for converting AC power supplied through the transformer into DC power. The flywheel braking device thus configured was used.

[0007] The flywheel braking apparatus of the present invention having the above-described structure stops the idle rotation of the flywheel by the electric braking force when the operation of the forging press is stopped. When the power supply circuit that supplies power to the electric motor is interrupted by the switch signal for stopping operation, power is supplied from the power supply circuit to the braking circuit. The braking circuit converts the supplied three-phase AC power into DC power, and supplies the DC power to the stator winding of the motor.

When the DC power is applied to the stator windings, the resulting magnetic field acts in a direction to prevent the rotation of the rotor of the motor connected to the flywheel, which is still rotating, and the electric power is generated. Dynamic braking acts on the electric motor, thereby braking the rotation of the flywheel.

In the braking circuit, the impedance is adjusted by appropriately setting the capacity of the transformer with respect to the electric motor.
This allows the braking time to be adjusted. The rectifier circuit uses a diode to rectify the current and at the same time prevent the backflow power from flowing. If a noise filter is inserted into the three-phase AC power sent from the transformer to the rectifier circuit, the power from the transformer can be supplied stably.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a power supply system for supplying power to the power section of the forging press 1. In the forging press 1, an upper end of a slide (not shown) is connected to a crankshaft 3 which is a main shaft to which a flywheel 2 is connected, and the rotational force of a motor 5 is transmitted to the flywheel 2 via an endless belt 4. The slide is driven up and down to forge a metal material in a mold on a machine bed. Power is supplied to the motor 5 from a power supply line via a switchboard 11 operated by a control signal from a control circuit 10.

When a start signal is sent from the switch S via the control circuit 10 to the switchboard 11, the switch in the switchboard 11 is turned on to supply power and drive the motor 5. The current and voltage at the time of starting the motor and at the time of rated operation are appropriately adjusted by control from the control circuit 10. In order to stop the motor 5 having such a power supply circuit when the forging press 1 is completed for one day or a series of operations, in this embodiment, a brake circuit 12 is provided in parallel with the power supply circuit. The DC power converted by the braking circuit 12 is supplied to a stator winding of the motor 5 to apply an electric braking force to the motor 5.

As shown in FIG. 2, the braking circuit 12 is connected so that power is supplied from a power supply line on the primary side of the motor 5, and the supplied AC power is supplied to a breaker (Br).
12a, the transformer 12 via the knife switch 12b
c. The impedance is adjusted in the transformer 12c, the safety of the AC power is guaranteed by a fuse (Fu) 12d, and the noise component included in the AC power is removed by a noise filter (Fi) 12e to supply stable power to the rectifier circuit 12f. Sent. The rectifier circuit 12f is configured using a diode to rectify AC power and prevent a reverse current from flowing.

The DC power rectified by the rectifier circuit 12f is:
It is supplied to the stator winding of the motor 5 and the flywheel 2
A magnetic field of DC power applied to the stator acts on the rotor of the motor 5 which is directly connected to the motor to prevent the rotation of the motor, thereby braking the rotation of the motor 5. Although not shown, the switchboard 11
There is provided a means for adjusting the current and voltage of the three-phase AC power of the power supply line supplied to the motor 5 according to the fluctuation state of the motor 5 at the time of starting, at the time of load, at the time of light load, and the like. The control means is controlled by a control signal from the control circuit 10, and when a stop signal from the switch S is sent to the switch 11a shown in FIG.
The power supply to is cut off. Then, at the same time as the power supply to the motor 5 is cut off, the knife switch 12b of the control circuit 12 is turned on by a signal from the control circuit 10 to supply power.

In the power supply circuit including the braking circuit 12 of the forging press configured as described above, when the operation of the forging press 1 is stopped, the rotation of the motor 5 is stopped by the braking circuit 12 to stop the rotation of the flywheel 2. Can be. When the forging press 1 completes one day or a series of machining operations, a stop signal is input from the switch S to the control circuit 10, and the control signal shuts off power to the motor 5 through the switch 11a of the switchboard 11. At the same time, the knife switch 12b of the braking circuit 12 is turned on to supply power. In the braking circuit 12, as described above, the three-phase AC power is rectified by the rectification circuit 12f, and the DC power is supplied to the stator winding of the motor 5.

However, even if the power supply from the power supply line to the motor 5 is interrupted, the motor 5 continues to rotate due to the rotational inertia of the flywheel 2 immediately after the interruption because the rotational energy of the flywheel 2 is large. . Therefore, an electric braking force acts so as to prevent the rotation of the rotor by the action of the magnetic field by the DC power supplied from the braking circuit 12, and the rotation of the motor 5 is rapidly reduced. At this time, when the rotor rotates in the magnetic field of the stator winding to which the DC power from the braking circuit 12 is supplied, a regenerative current is generated in the motor 5, but the power supply line is cut off. Therefore there is no backflow. The impedance of the transformer 12c is adjusted by appropriately setting its capacity with respect to the motor 5, whereby the braking time is adjusted.

The motor 5 by the braking circuit 12 as described above
In the case of stop braking, a complete stop is achieved in a much shorter time than stop braking by a mechanical flywheel brake. It can be seen that the braking time is extremely short from the following data obtained by actually measuring the electric braking by the braking circuit 12 when the mechanical wheel brake is provided in the illustrated example.

Forging press 2500 tons Motor capacity 150 kw Flywheel rotation speed 60 RPM Flywheel possessed energy 140,300 kgM Flywheel natural stop time 10 minutes 48 seconds ・ Electric brake (for transformer capacity 13 KVA) Stop in 20 seconds ・ Mechanical brake In the above embodiment, the conventional mechanical braking brake was omitted, and instead, the braking circuit 12 was arranged in parallel with the power supply circuit to actuate the electric braking brake. Of course, the mechanical braking brake may be used as a safety measure after the electrical safety stop.

[0018]

As described above in detail, in the flywheel braking device of the present invention, power is supplied to the power supply circuit to the motor of the forging press by the stop signal when the operation is stopped, and the AC power is supplied. A braking circuit that converts the DC power to electric power and sends it to the electric motor to provide a braking force that prevents the rotation of the rotor is provided in parallel, so that the flywheel idles using electrical braking force instead of mechanical braking means. An effect is obtained that braking can be performed, and the braking time can be shortened so that braking can be performed safely and reliably.

[Brief description of the drawings]

FIG. 1 is a power supply system diagram of a driving unit of a forging press according to an embodiment.

FIG. 2 is a schematic system diagram of a power supply circuit including a braking circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Forging press 2 Flywheel 3 Crankshaft 4 Endless belt 5 Motor 10 Control circuit 11 Switchboard 12 Braking circuit 12c Transformer 12e Noise filter 12f Rectification circuit

Claims (2)

[Claims] 1. A power supply circuit for supplying power to a motor that rotationally drives a main shaft to which a flywheel of a forging press is connected is connected to a power supply circuit. Is entered,
The AC power is converted into DC power, a braking circuit for supplying the DC power to the stator of the motor to brake the motor is provided in parallel, a power switch for inputting power to the braking circuit, and a circuit switch. A transformer to adjust the impedance,
A flywheel braking device comprising: a rectifier circuit using a diode that converts AC power supplied through the transformer into DC power. 2. The flywheel braking device according to claim 1, wherein a noise filter is provided in a line for sending power output from the transformer to a rectifier circuit.