JP2003230999A - Press machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press machine in which stable motor drive control can be conducted while miniaturizing power supply facilities and reducing costs. <P>SOLUTION: A motor drive control circuit for a motor is formed by a communication circuit connected to the power supply facilities and a driver circuit to generate and output the power supply for motor drive control connected to the communication circuit, and at the same time, a power storage device, which include a voltage converter and a storage battery between the commutation circuit and the driver circuit and between two poles of the circuits and is capable of storing counter electromotive force generated from the motor during the deceleration of the motor as electric energy. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
Press machine that presses while moving the slide up and down
Related. [0002] BACKGROUND ART Via a drive mechanism (for example, a crank mechanism)
Pressing while raising and lowering the slide by rotating the motor
The conventional press machine to be built is stored in the flywheel
Rotational energy is transmitted through the clutch / brake device.
Selectively transmitting and separating to crankshaft, press operation / stop
It is configured to be. [0003] Thus, the rotational power to the crankshaft is
Accumulated on the flywheel driven by the
Clutch and clutch interposed between the wheel and the crankshaft
When the brake is off and the clutch is on,
It is transmitted from the rye wheel. This allows the crankshaft
Slides connected via connecting rods
Move (lift). Clutch OFF / Brake ON state
Is switched off, the rotational power to the crankshaft is shut off (press
Stop). The driving mechanism is a crank mechanism and
A flywheel, clutch and brake device
With large sliding force (load value)
The slide motion [time t-slide
Position PT (or crank angle θ-slide position PT)]
Since the curve has a sine wave shape, other drive mechanisms (for example,
Knuckle mechanism, link mechanism, etc.)
I cannot take an id motion curve. The drive mechanism is, for example,
In the case of a toggle mechanism (or link mechanism), other drive mechanisms
(For example, a crank mechanism)
I can't take an action curve. [0005] Therefore, the advantage of the crank mechanism (for generating a large load value).
Raw, simple structure, robustness, low cost, etc.)
So-called servo motor drive that rotates the link shaft with a motor
A dynamic press machine is proposed (for example, Japanese Patent Application No. 2001-38).
No. 8835). According to such a press machine,
Various slide motions can be switched and used.
In addition to being able to expand the adaptability to
Compared to the conventional crank mechanism type press machine,
E-wheels, clutches and brakes can be eliminated
Therefore, it is also advantageous in terms of equipment economy and reduction in size and weight.
Shorter life due to frequent operation of clutch and brake device
Will not occur. The servo motor is a motor drive control unit.
Is driven and controlled by a PWM signal generated and output from the. sand
That is, the motor drive control unit controls the current based on the position command signal.
The deviation signal (torque deviation signal) is input and the detected current signal
Signal as feedback signal to generate PWM signal
You. Power supply (DC power supply)
DC rectified from the main power supply (AC power supply) by the rectifier circuit
Power supply. [0007] Problems to be Solved by the Invention
Press-type press machine, as in the
To store the motor rotation power in the flywheel.
Power supply equipment in the factory must be large capacity
There is an inherent problem. That is, a press of a servo motor drive system
For machines, the size depends on the pressing force (load) during press forming.
Current to the motor, otherwise the motor
Only minimal current flows through the Thus, for example, oil
More energy saving compared to pressure pump drive
It is said that it can be. [0009] However, the power supply equipment requires press molding.
Since the maximum current sometimes flows, even if it is not always necessary,
It must be constructed to supply a large current. That is,
The economic burden is heavy, the basic electricity rate rises, and the factory
Affects the layout and consequently the servo motor
One of the factors hindering the spread of drive-type press machines
You can say that. [0010] Such a problem is caused by the fact that the drive mechanism is a crank.
Mode via a different mechanism than the mechanism (for example, screw mechanism)
Pressing while raising and lowering the slide by rotating the table
The same applies to a press machine. An object of the present invention is to reduce the size of power supply equipment and
Stable motor drive control while reducing costs
To provide a press machine driven by a servomotor
You. [0012] For example, in FIG.
Rectifier circuit connected to a power supply equipment 90 for supplying a power supply
(Rectifier diode D) 95 and driver circuit 72B
In a conventional motor drive control circuit consisting of
Occurs when the motor decelerates (the transistor Tr turns on).
External resistance to convert the back EMF into heat and consume it
(The resistance of the motor itself may be used.) Connect R
A resistance heat conversion circuit (resistance heat conversion method)
ing. However, freely control the slide speed
When the motor drive current becomes large,
Therefore, it is not advisable to provide a resistance heat conversion circuit.
Difficult to use. Naturally, for the maximum required current during press molding
It cannot be expected that the power supply equipment 90 has a small capacity and a small size. What
In FIG. 9, C is a rectified DC power supply smoothing capacitor.
It is. [0013] Also, a direct regenerative regeneration replacing the resistance heat conversion system
In the circuit system, as shown in FIG.
Regenerative circuit including transistor Tr connected in parallel with
97 to supply back electromotive force generated during motor deceleration
Returning directly to the equipment 90 (regeneration). According to this,
We can plan energy. However, if the power supply equipment 90 is small,
The regenerative voltage may increase (overvoltage) and cause damage.
Even with this method, the maximum current required during press molding is
To meet the demand for smaller capacity and smaller power supply equipment 90
I can't. Therefore, a conventional press machine is a flywheel.
Energy storage function by
Focus on the motor drive control circuit structure in the motor drive system
If it is, the electric circuit energy in the motor drive control circuit
The idea is to form a capacitor with a storage function
Can be However, this capacitor is
Since the capacity is much larger than that of the capacitor C,
The accommodation box is large enough to affect the side layout
For example, 100 or more pressure-resistant
DENSA maintenance is also difficult to use with press machines. Here, the present invention relates to, for example, a hybrid type
And fuel cell type are becoming increasingly smaller and lower cost.
Focusing on storage batteries that would be
The purpose is to form an energy storage function using a battery.
Is to achieve. That is, according to the first aspect of the present invention, a driving mechanism is provided.
Slide up and down by rotating the motor
In a press machine for processing, a motor for the motor is provided.
The drive control circuit is connected to a rectifier circuit
Generates and outputs the motor drive control power supply connected to the
Rectifier circuit and driver
Voltage converter and storage between the driver circuit and between both poles
Reverse generated from the motor during motor deceleration, including the pond
Install a power storage device that can store electromotive force as electrical energy.
This is a press machine. In the press machine according to the first aspect of the present invention,
When the rectifier circuit rectifies the AC power from the power supply,
Driver circuit provides motor drive control power supply (AC power supply)
Generate and output. As a result, the rotation of the motor is controlled and the
The link shaft rotates and the slide can be moved up and down. At the time of motor deceleration, the reverse
The electromotive force is stored in the power storage device. That is, DC circuit power
The voltage is converted by a voltage converter (for example, 380V →
48V) and stored as electrical energy in the storage battery
You. There is no heat loss compared to the resistance heat conversion method. Ma
In addition, special direct regeneration compared to the direct regeneration circuit method
There is no need to provide a circuit. Increase in regenerative voltage (overvoltage)
Can also be prevented. At the time of press molding, the power storage device (storage battery)
Voltage conversion (for example, from 48V to 380V)
Energy is released (supplied) to the inverter circuit. Toes
Supply all the power equivalent to the maximum load from the power supply equipment
There is no. Thus, it is possible to reduce the capacity of power supply equipment
Quick response when increasing slide speed or restarting
Stable operation is possible. [0020] DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings. The press machine 10 has a structure as shown in FIGS.
The rotation drive control circuit for the motor 30
Connected rectifier circuit 95 and connected to this rectifier circuit 95
Driver circuit that generates and outputs a motor drive control power supply
Rectifier circuit 95 and driver circuit 7
2B and between the two poles.
7 is generated from the motor 30 when the motor is decelerated.
Storage device that can store the back electromotive force as electrical energy
75 prevents regenerative voltage rise during motor deceleration
To achieve a small capacity and small size of the power supply equipment 90
Have been. In FIG. 1, a driving mechanism of a press machine 10 is shown.
Is composed of a crank mechanism 11 including a crank shaft 12 and the like.
Have been. This crankshaft 12 is mounted on bearings 14, 14.
The motor 30 is rotatably supported and has a gear (main gear).
Gear 13, pinion 30G: indirectly via a reduction mechanism)
Are linked. Such gear (reduction mechanism 30G, 13)
Can obtain a much higher slide load value
You. The motor 30 may be directly connected to the crankshaft 12. The driving mechanism of the press machine 10 is a
Not limited to the crank mechanism 11 including the link shaft 12, etc.
(For example, a screw mechanism shown in FIG. 8).
No. In FIG. 8, a screw (for example, a ball screw)
Slide by rotation of rotary motor 30A via mechanism
17 (frame 17P, nut member 17N) can be raised and lowered
To achieve. That is, the ball screw 32 (screw portion)
32S) to rotate the ball screw.
You. Suitable for small machines. This motor 30 is a servo motor drive system.
Formed from an AC (alternating current) servomotor for
A cooling fan 30F is provided integrally. Motor shaft
30S is a state in which rotation is stopped by the stop state holding brake 19.
Can be held (locked). The motor 30 is DC
(DC) Servo motors, lasers without permanent magnets or brushes
It may be formed from a lactance motor or the like. A stove constituting a part of the drive mechanism (11)
The head 16 is fitted at its upper end to the eccentric part of the crankshaft 12.
And a lower end portion is provided with a spherical bearing member (shown in FIG.
(Omitted). In addition, crank machine
As in the case of a conventional press machine with a
Between the slide 16 and the slide 17 to prevent overload of hydraulic release type.
No stop device is provided. Because, in this embodiment, the motor 3
Calculated using 0 drive current (Iu, Iv, Iw)
Monitor the slide load value and play before the load value becomes excessive.
This is because they are formed so that they can be stopped. Overload prevention device
Is to reduce the weight and size of the press machine 10 itself.
It can greatly contribute to cost reduction. The slide 17 is vertically moved on the press frame 1.
It is slidably mounted in the direction. If necessary,
It may be engaged with a light balance device. Crankshaft 12
, The slide 1 is connected via the connecting rod 16.
7 can be driven up and down. The mold is on the slide 17 side
And a lower die on the bolster 2 side. Each of the AC servomotors (30) shown in FIG.
Corresponds to motor drive currents Iu, Iv, Iw of phases U, V, W
The phase current signals Ui, Vi, Wi that are output from the
Is detected by 1 and FIG.
2 is connected. This rotary encoder 35 is basically
Has a number of optical slits and optical detectors,
Output the rotation angle θm of the third motor 30 (crankshaft 12).
However, in the first embodiment, the crank angle θm
(Pulse signal) is a signal corresponding to the vertical position of the slide 17.
Signal converter that converts to PT (pulse signal) and outputs it (Figure
(Not shown). As shown in FIG. 1 and FIG.
The motor 30 and the crankshaft 12
Speed reduction mechanism (30G, 13) interposed between
From the detection axis 12S to respond to this.
Encoder 3 for detecting ride position (slide speed)
7 is provided. Basic configuration / machine of this encoder 37
The function is the same as that of the encoder 35 for motor rotation drive control.
The same is true. In FIG. 2 and FIG.
The fixed selection command drive control unit is different from the setting selection command unit (50) in position.
It is formed by the setting speed control unit 60 and the motor drive control unit 70.
Have been. The position / speed control unit 60 and the motor drive control
The part 70 can be formed integrally. In FIG. 2, the computer 80 has a CP
U (including a clock function) 81, ROM 82, RAM 83,
Operation panel (PNL) 84, display unit (IND) 85 and
And a plurality of interfaces (I / F) 86, 88, 9
1, 92, and a setting selection finger for the press machine 10.
The command part (50) and the like are constituted, and in this embodiment,
A monitoring unit for the entire press machine is formed. The computer 80 has the status of its own device (10).
Various information is displayed on the display unit (IND) 85 for convenience of status judgment.
(For example, crank angle θk, slide position PT,
All of the operation speed, acceleration, load value, etc.)
The part selected using the channel (PNL) 84 is displayed.
It is formed so as to be forceful. The rotation angle of the crankshaft 12 (crank angle
Degree) θk is detected by the encoder 37 and the slide position P
T is the amount of eccentricity of the crankshaft 12, the length of the connecting rod 16,
It is calculated using the crank angle θ and the like. Also slide
Movement speed and acceleration use slide position (PT) information
The load value is calculated by converting the drive current of the motor 30.
Required. The display output mode to the display unit 85 is digital.
It can be done as numerical values or graphic curves. Thus,
Can quickly and accurately grasp the molding status during operation
To produce high quality products efficiently and safely
Can greatly contribute to Each such display output information is stored in a memory (RAM 8
3 or any flash memory or hardware not shown
Disk device). Further
In advance, set thresholds for each value, and
Can be used to stop. The interface (I) of the computer 80
/ F) 86 is the position command signal (PTs) shown in FIGS.
For output, the interface (I / F) 88 is
For detecting the signal (θk) equivalent to the ride speed (position).
The interface (I / F) 91 is a stop state holding brake 1
9 for the control signal, and the interface (I / F) 92
It is for a control signal of the work transfer device 100. In the following, various fixed information and control programs are described.
The program, calculation (calculation) formula, etc. are fixedly stored in the ROM 82.
It is described as stored, but these are rewritten
Flash memory and hard disk drive (HD
D) or the like. Each setting selection command section 50 is provided with a speed setting device (5
1 ... Symbols omitted in the drawing), motion pattern selector
(52 ... not shown in the drawing) and motion command section
(53 ... not shown in the drawing)
The setting slide position signal (setting selection mode) shown in FIG.
). Operation panel 84, slide motion pattern
ROM that stores program and pattern selection control programs
Motion putter formed from 82 and CPU 81
A plurality of modes set and stored in advance using the switch selector (52).
Solution pattern (elapsed time t-slide position PT)
[Or crank angle θk-slide position PT]
Select desired motion pattern (t-PT curve) from
You can choose. Selected motion pattern
(T-PT curve) is set using the speed setting device (51).
Fixed motor rotation speed (or rpm ... slide speed)
Along with [so-called slide stroke number (SPM)]
Output to the motion command unit (53). The speed setting device (51) is connected to the operation panel 84.
And the rotation speed of the motor 30 [for example, 100 r
pm (× reduction ratio γ)] can be set manually
You. When “Auto” is selected, it is selected and set in advance.
The maximum rotation speed [for example, 120 rpm (× reduction ratio)
γ)] is treated as selected. In addition, speed
Set SPM directly with setting device (51) as SPM setting device
May be formed. R storing a motion command program
Motion finger formed from OM 82 and CPU 81
The command unit (53) has a position pulse payout structure
Motion pattern (t-PT curve SMC)
Accordingly, the position command pulse PTs is output. For example, setting using a speed setting device (51)
The motor rotation speed is 120 rpm and the encoder 3
The number of pulses output per rotation (360 degrees) from 5
1 million pulses with a payout cycle time of 5 ms
The pulse output every cycle (5mS)
The number is 10,000 pulses [= (1,000,000 × 12
0) / (60 × 0.005)]. The speed setting device (51) and the motion
Turn selector (52) and motion command unit (53)
Are setters and logistics that can be connected to each computer 80.
Or a network circuit, a sequencer or the like. In FIG. 3, the position / speed control unit 60
Position comparator 61, position control unit 62, speed comparator 63, speed
The control unit 64 includes a current command signal Si
Is output. The speed detector 36
Is included in the position / velocity control unit 60 for convenience of illustration.
It was expressed by. First, the position comparator 61 receives a motion command
Section (53) [81, 82] position command signal output interface
-Set slide position signal input from face 86
(Target value signal) PTs and encoder 35 (considering reduction ratio γ
If it devises, it can also be implemented using 37. )
Actual slide position feedback signal F detected at
PT [θm = (1 / γ) · θk],
A difference signal 差 PT is generated and output. The position control unit 62 receives the input position deviation signal.
△ PT is accumulated, multiplied by the position loop gain,
A degree signal Sp is generated and output. The speed comparator 63 calculates the speed
The speed signal Sp and the speed signal from the speed detector 36 (speed filter
Feedback signal) and the speed deviation signal △ S
Generate and output The speed control unit 64 receives the input speed deviation signal.
No. S is multiplied by the speed loop gain to generate a current command signal Si.
And outputs it to the current control unit 71. This current command signal S
i is substantially a torque signal, but during sliding down
Does not apply press load, so motor torque is almost constant
Since it is necessary to increase or decrease the rotation speed with
The signal level is smaller than when the load value control is being performed. The motor drive controller 70 includes a current controller 71
, PWM control section (driver section) 72 and phase signal generation section 4
0. The current control unit 71 controls each phase (U, U,
V, W) current control units 71U, 71V, 71W.
You. For example, the U-phase current control unit 71U outputs the current command signal (to
Multiply Si by U-phase signal Up
A target current signal Usi is generated, and a U-phase target current signal U
si and the actual U-phase current signal Ui to compare the current deviation signal.
(U-phase current deviation signal) Siu. other
The V and W phase current controllers 71V and 71W also output V and W phase currents.
Deviation signals Siv and Siw are generated and output. The phase signal U input to the current control unit 71
p, Vp, and Wp are generated by the phase signal generation unit 40. 7
3 is a phase motor current detector, and each phase current (value) signal U
i, Vi, Wi are detected and fed back to the current control unit 71.
Click. The PWM control section (driver section) 72 is shown in FIG.
A circuit (not shown) for performing pulse width modulation shown in FIG.
The isolation circuit 72A and the driver 7 shown in FIG.
2B and is output from the current control unit 71 in FIG.
PWM from the current deviation signals Siu, Siv, Siw of each phase
The modulated PWM signals Spwmu, Spwmv, Spw
Generate mw. As shown in FIG. 7, the driver 72B
A switching circuit with a pair of transistors for each phase
Switching (ON / ON) with each PWM signal Spwm.
OFF) is controlled, and each phase motor drive current Iu, Iv, I
w can be output to each phase of the motor. In FIG. 7, the driver (driver turn)
Path) 72B is a rectifier circuit including a rectifier diode D for each phase.
The rectifier circuit 95 is connected to the power supply equipment 90.
It is connected. That is, this driver 72B
Construct an inverter circuit. Here, the rectifier circuit 95 and the driver circuit
(72B) and between the two poles.
A power storage device 75 including a battery 77 is provided. When the motor is decelerated, the storage battery 77
30 while absorbing the back electromotive force
And can be stored as a motor during press molding.
A current can be supplied as a driving power supply. Voltage of storage battery 77
Is selected from, for example, 48V to 200V.
In the embodiment, it is set to 48V. As the storage battery 77, a nickel hydrogen battery is used.
Although it is adopted, even if it is formed from a lithium ion battery etc.
Good. In the future, further miniaturization and cost reduction will progress
Is it possible to use electric vehicles?
Therefore, the embodiment can be more easily realized. The capacity of the storage battery 77 is an example.
For example, the conditional expression [1.02 (Tb−k × Tm) (N /
2)]. Where Tb is the braking torque
(Kg · m) and Tm are the motor torque (Kg · m) and k
Is the motor internal loss constant, N is the deceleration start speed (rpm)
is there. For example, Tb = 100 kg · m, Tm = 2
In the case of 00Kg · m, k = 0.2 and N = 500 rpm
In this case, it is 15300W. Therefore, 16-20k
W is good. The following regenerative voltage rise prevention capacitors
Dramatic downsizing and cost reduction compared to
Can be achieved. Easy to handle and requires little maintenance
There is no. Incidentally, the above-mentioned capacitor type energy
Energy storage function
Capacitor (capacitor for preventing regenerative voltage rise)
Is the condition [1.02 (Tb−k × Tm) (N / 2) ≦
(1/2) × (CV₀ ²)]
The quantity (F) is C and the DC circuit voltage (V) is V₀If
And V₀= 380V (when the power supply voltage is 200V)
C = 0.21F. When the power supply voltage is 400V,
If V₀= 760V. A capacitor for preventing a regenerative voltage rise of 0.21F
The voltage is, for example, withstand voltage (for example, 400 V or 800 V)
Connected with 100 2200μF capacitors
The accommodation volume is large enough to affect the surrounding layout.
Large size and high cost, withstand voltage type capacitor
Maintenance is not familiar with press machines. It is to be noted that the storage battery 77 has an energy storage function.
In case of adoption and construction, rechargeable battery 77 can be charged in advance
And does not discharge even when the main power supply fails,
System problems (waste of energy)
it can. The voltage converter 76 composed of an inverter is
DC circuit voltage (V₀… 380 when the original power supply is 200V
V, 760 V when the main power supply is 400 V).
And the regenerative current
Charge. During press molding, the voltage of the storage battery 77 (above
48V) to the DC circuit voltage (V₀… Original power supply is 200V
380V in case of, 760 in case the source power is 400V
V) while supplying power (current). In the embodiment having such a configuration, the rectifier circuit 95
Rectifies the AC power (source power) from the power supply equipment 90
And the driver circuit (72B) is a power supply for motor drive control.
(AC power supply: each phase motor drive current Iu, Iv, Iw)
Generate and output. Thereby, the rotation of the motor 30 is controlled.
The crankshaft 12 rotates and the slide 17 is started up and down.
Can be. At the time of motor deceleration, the motor 30
The back electromotive force is absorbed by the storage battery 77 and converted into electric energy.
And is accumulated, which is lower than that in the case of the resistance heat conversion method (Fig. 9).
There is no heat loss in comparison. In the case of the direct regeneration circuit method
It is necessary to provide a special direct regeneration circuit compared to (Fig. 10).
There is no. It can also prevent the regenerative voltage from rising (overvoltage).
it can. On the other hand, during press molding,
Energy is released (supplied) to the driver circuit (72B)
Is done. That is, the total power equivalent to the maximum load is
There is no need to supply from. Thus, the power supply equipment 90 is small.
Increase capacity and increase slide speed or restart
In some cases, the response is quick and stable. The AC power from the power supply equipment 90 is rectified.
The ripple at the time of rectification by the circuit 95 is
Smoothing DC power after rectification because it can be removed by function
Can be promoted. [0067] According to the first aspect of the present invention, when the motor is decelerated,
The back EMF generated by the motor is absorbed by the storage battery
Increased regenerative voltage because it is stored as electrical energy
(Overvoltage) can also be prevented. Resistance heat conversion method
There is no heat loss compared to the case of Also, the direct regenerative circuit
It is necessary to provide a special direct regenerative circuit
Absent. Also, during press molding, the battery is
Maximum load because energy is released (supplied) to the circuit
There is no need to supply a significant amount of power from the power supply. Scratch
To reduce the capacity, size, and cost of power supply equipment
At the same time as increasing the slide speed or restarting.
Press operation with fast and stable motor drive control
Can be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a press machine for explaining an embodiment of the present invention. FIG. 2 is a block diagram for explaining a setting selection command unit (computer), a position / speed control unit, and a motor drive control unit. FIG. 3 is a circuit diagram for explaining details of a position / speed control unit and a motor drive control unit. FIG. 4 is a circuit diagram for explaining a current control unit. FIG. 5 is also a diagram for explaining a pulse width modulation operation. FIG. 6 is also a diagram for explaining an isolation circuit. FIG. 7 is a diagram illustrating a power storage device. FIG. 8 is a view for explaining a modification of the driving mechanism. FIG. 9 is a diagram for explaining a conventional example (resistance heat conversion method). FIG. 10 is a diagram for explaining a conventional example (direct regeneration circuit system). [Description of Signs] 10 Press machine 11 Crank mechanism (drive mechanism) 12 Crankshaft 13 Main gear (gear) 17 Slide 30 (30A) AC servomotor (motor) 30G Pinion 32 Ball screw (screw) [Drive mechanism] 35 Motor shaft Encoder 37 crankshaft encoder 40 phase signal generation unit 60 position / speed control unit 70 motor drive control unit (motor drive control circuit) 71 current control unit 72A isolation circuit 72B driver (driver circuit) 75 power storage device 76 voltage from inverter Conversion device 77 Storage battery 80 Personal computer (setting selection command section) 90 Power supply equipment 95 Rectifier circuit 97 Direct regeneration circuit

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Claims (1)

Claims: 1. A press machine for performing press working while raising and lowering a slide by rotation of a motor via a drive mechanism, wherein the motor drive control circuit for the motor is connected to a rectifier circuit connected to a power supply facility. A driver circuit for generating and outputting a motor drive control power supply connected to the rectifier circuit is formed and includes a voltage converter and a storage battery between the rectifier circuit and the driver circuit and between both poles. A press machine comprising a power storage device capable of storing generated back electromotive force as electric energy.