JP4042820B2 - Electric cylinder - Google Patents

Description

The present invention relates to an electric cylinder.

  This type of electric cylinder is used in an injection molding machine as described in Patent Document 1, for example.

  In this injection molding machine, a movable mold provided movably on the frame of the injection molding machine and a fixed mold fixed to the frame via a fixed plate are joined to form a cavity, and contact with the mold. And an injection mechanism for injecting molten plastic into the cavity, and a moving mechanism for causing the injection mechanism to move forward and backward and turn with respect to the mold. For molding, the injection mechanism is moved to the fixed mold by the moving mechanism section, the nozzle included in the injection mechanism passes through the fixed plate and is pressed against the spool bush or nozzle touch section in the fixed mold, and the molten plastic is injected into the cavity. It is made by that.

The electric cylinder constitutes a part of the moving mechanism, and the rod, the outer cylinder that holds the rod so as to be linearly movable, the electric motor, and the motor between the rod and the electric motor in order to convert the rotation of the electric motor into linear motion. It consists of a motion conversion mechanism such as a ball screw composed of a screw shaft and a nut , and a spring unit. The rod is connected to the injection mechanism, and the outer cylinder is connected to the frame.

When the nozzle is crimped to the fixed spool bush, the nut of the ball screw activates the limit switch to stop the motor, and at the same time, the nut pushes the spring unit and the spring force of the spring unit causes the nozzle and spool bush to be crimped or The pressed state is maintained.
Patent No. 3,237,636

Such an electric cylinder, for example, has a spring sag or the like, so that it is necessary to replace the spring unit periodically. Conventionally, this replacement work is simply performed by removing the electric cylinder from the injection molding machine, disassembling the electric cylinder, replacing the spring unit, reassembling the electric cylinder, and reattaching the injection molding machine. Furthermore, even after mounting on the injection molding machine, position adjustment work such as a limit switch inside the electric cylinder is required while operating the electric cylinder. For this reason, it is the present condition that considerable effort and labor are required to replace the spring unit. Furthermore, there has been a concern that malfunctions may occur due to overcurrent caused by a temporary overload or when the motor is started.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electric motor that can easily and quickly replace a spring unit without requiring labor and labor , and that prevents malfunction due to overcurrent caused by a starting current and a temporary overload. To provide a cylinder.

An electric cylinder according to the present invention includes an electric motor, a motion conversion mechanism that is disposed between the electric motor and the rod, and converts rotation of the electric motor into linear motion of the rod, and a driven member connected to the rod and the rod. It is arranged between the spring unit attached to the tip of the rod and the electric motor to supply the electric power while reducing the impact during the pressing operation of the rod by elastic force and maintaining the pressing force when the pressing operation stops An electric drive unit that stops power supply to the electric motor when the power value exceeds a preset reference value, and the electric drive unit includes a start timer circuit and an overcurrent timer circuit, thereby To achieve this goal.

An electric cylinder according to the present invention includes an electric motor, a motion conversion mechanism that is disposed between the electric motor and the rod, and converts rotation of the electric motor into linear motion of the rod, and a driven member connected to the rod and the rod. It is arranged between the spring unit attached to the tip of the rod and the electric motor to supply the electric power while reducing the impact during the pressing operation of the rod by elastic force and maintaining the pressing force when the pressing operation stops An electric drive unit that stops power supply to the motor when the value of the power exceeds a preset reference value;
a) Since the electric drive unit includes a start timer circuit and an overcurrent timer circuit, malfunction due to an overcurrent caused by a start current and a temporary overload can be prevented.
b) The spring unit can be replaced without disassembling the cylinder body.
c) Since the electric power supplied to the motor is controlled from the outside by controlling the operation of the motor, the position adjustment work such as the limit switch is not required even if the spring unit is replaced. Can be performed very easily and quickly.
It can produce a particularly remarkable effect.

  An embodiment of the electric cylinder of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, this electric cylinder has a cylinder body 11 and an electric motor 12. The cylinder body 11 includes an outer cylinder 13. The outer cylinder 13 has a hollow shape with both ends open, and one end is fitted and fixed to the bracket 14. The rod 15 is also hollow with both ends open and is slidably fitted into the outer cylinder 13. The motion converting mechanism for reciprocating linear movement of the rod 15 includes a ball screw having a ball circulation type screw shaft 16 and a nut 17 . The screw shaft 16 penetrates the rod 15 and the end portion that has entered the bracket 14 is rotatably held by the bracket 14 via a bearing. The nut 17 is fitted into the rod 15 and is screwed to the rod 15 to stop its rotation.

The electric motor 12 is composed of, for example, a motor with a brake, and its shaft is positioned in parallel with the rod 15 and is coupled to an extension portion 14 a constituting the bracket 14. The shaft of the electric motor 12 is connected to the screw shaft 16 by a gear train 18. The gear train 18 is built in the extension 14 a of the bracket 14. For this reason, when the electric motor 12 rotates and the rotation is transmitted to the screw shaft 16 by the gear train 18, the nut 17 and the rod 15 move linearly and the rod 15 expands and contracts.

The end of the rod 15, that have spring unit 20 is mounted. The spring unit 20 includes a unit main body 21 and a tip tool 22. The unit main body 21 has a hollow shape with one end opened, and a shaft portion 26 is integrally formed on the closed end side. The tip 22 includes a head 22 a having a bifurcated connecting portion and a neck 22 b extending from the rear end of the head 22 a. The neck 22 b is positioned inside the unit main body 21, and the head 22 a is slid on the unit main body 21. It is inserted movably. The head 22a is guided by a key so as to only move linearly. A disc spring 23 is fitted on the neck 22 b of the tip tool 22. Spring receivers 24 and 25 are positioned at both ends of the disc spring 23 and are fitted to the neck 22 b of the tip tool 22. The spring receiver 24 abuts on the head 22a and can move along the neck 22b together with the head 22a. The position of the spring receiver 25 is fixed by coming into contact with the stopper member 25a screwed into the end wall of the step wall 21a of the hollow hole of the unit main body 21 and the neck 22b. For this reason, when the tip tool 22 moves to the left in FIG. 1, the spring receiver 24 is pushed by the head 22a, and the disc spring 23 is compressed.

  The spring unit 20 is attached to the rod 15 by fitting the shaft portion 26 to the tip of the rod 15 and fitting the connecting pin 27 into the rod 15. The connection pin 27 is prevented from coming off from the connection pin 27 and the rod 15 by a stop pin 28.

The operation and control of the electric cylinder are performed by an electric drive unit 30 outside the cylinder body 11 and the electric motor 12. As shown in FIG. 2, the electric drive unit 30 includes a power feeding circuit 31 and a pressing force detection circuit 32.

  The power feeding circuit 31 includes a cutoff circuit 33 including a relay contact that disconnects between the power source and the electric motor 12 and a rotation direction selection circuit 34 including a relay contact that changes the direction of the current supplied to the electric motor 12.

The pressing force detection circuit 32 includes an electric motor current detection circuit 35, a pressing force setting circuit 36, a comparison circuit 37, a start timer circuit 38, an overcurrent timer circuit 39, and a cutoff control circuit 41. The motor current detection circuit 35 includes a current transformer attached to the power supply cable of the motor 12. The pressing force setting circuit 36 is for setting a reference voltage corresponding to the current when the electric cylinder generates a predetermined pressing force, and continuously setting a certain range of settings centered on the reference voltage by a variable resistor. it can. The comparison circuit 37 is for comparing the output of the motor current detection circuit 35 and the output of the pressing force setting circuit 36, and is composed of, for example, an operational amplifier.
The start timer circuit 38 is for preventing malfunction of the electric cylinder when a current exceeding the current value corresponding to the reference voltage of the pressing force setting circuit 36 is detected by the start current flowing in the electric motor 12. .
When the current exceeding the current value corresponding to the reference voltage of the pressing force setting circuit 36 is detected by an instantaneous overcurrent flowing through the motor 12 due to a temporary overload or the like, the overcurrent timer circuit 39 This is to prevent the malfunction of the.
The cutoff control circuit 41 includes a relay for opening and closing the contactor constituting the cutoff circuit 33. After the start timer circuit 38 times out, a current is passed through the relay coil in accordance with the output of the overcurrent timer circuit 39, The contactor coil is de-energized, the contactor coil is de-energized, the contactor contact is opened, and the current flowing through the motor 12 is interrupted.

In this electric cylinder, when the electric motor 12 operates, the screw shaft 16 rotates, the nut 17 moves linearly, and the rod 15 contracts. As a result, the driven member is pressed against another member, and the nut 17 of the screw shaft 16 is positioned at the inner end of the outer cylinder 13 and comes into contact with the stop 29 incorporated in the bracket 14. The disc spring 23 of the spring unit 20 bends, reduces the impact, and protects the screw shaft 16 and the nut 17. At the same time, the rod 15 continues to push the driven member against other members related to the driven member by the spring force generated by the compression of the disc spring 23 of the spring unit 20.

  When the driven member is pressed against another member, the current value of the power feeding circuit 31 of the electric motor 12 increases. The operational amplifier of the comparison circuit 37 compares the voltage of the pressing force setting circuit 36 with the secondary coil voltage of the current transformer in the motor current detection circuit 35, and outputs a signal because the secondary coil voltage of the current transformer is high. To do. The interruption control circuit 41 causes a current to flow through the relay coil by this output signal, opens the relay contact, opens the contactor contact in the power supply circuit 31, and stops the power supply to the motor 12. At this time, the disc spring 23 of the spring unit 20 gradually increases the value of the current flowing through the power supply circuit 31 of the electric motor 12, so that the current value can be reliably detected. If for some reason the current flowing through the motor 12 becomes abnormally large, the shutoff control circuit 41 causes the current to flow through the relay coil by the output from the operational amplifier of the overcurrent timer circuit 39 to open the relay contact. The contactor contact at 31 is opened to stop power supply to the motor 12.

  When the rotation of the electric motor 12 is reversed, the screw shaft 16 rotates in the opposite direction, the nut 17 and the rod 15 move linearly in the opposite direction, and the rod 15 extends. When the driven member is moved to the initial position and hits a stop or the like, the current value flowing through the motor 12 increases, the overcurrent timer circuit 39 outputs a signal, the current flows through the relay coil of the shutoff control circuit 41, and the relay contact ( b contact) is opened, the coil of the contactor included in the power feeding circuit 31 is de-energized, the contact of the contactor is opened, and power feeding to the motor 12 is stopped.

Figure 3 shows an example of a specific configuration of the electric drive unit 30. Reference numeral 122 is a current transformer, and 121 is a smoothing circuit that rectifies the current flowing through the motor 12 detected by the current transformer 122 to form the motor current detection circuit 35. A variable resistor 125 forms a pressing force setting circuit 36 that sets a voltage signal E2 corresponding to a current flowing through the electric motor 12 when the electric cylinder generates a required pressing force. Reference numeral 129 denotes an operational amplifier forming a first comparison circuit. The fixed resistors 141 and 142, the operational amplifier 143, the resistor 144, and the capacitor 145 that divide the control power supply voltage Vcc so that the electric cylinder does not malfunction even if the pressing force of the rod 15 exceeds the set value due to instantaneous overcurrent. Forms an overcurrent timer circuit 39. Reference numerals 131 and 132 denote resistors for dividing the control power supply voltage Vcc to a voltage E11 corresponding to about 10% of the rated current of the motor 12, and together with the operational amplifier 133, the capacitor 135 and the resistor 134, form a start timer for the motor 12. is doing. 146 is a Zener diode, 147 and 149 are switching transistors, 150 is a relay that de-energizes the coil of the contactor that cuts off the current flowing through the motor 12, and the relay coil forms a cutoff control circuit 41 together with the switching transistors 147 and 149. ing.

  When power is supplied, the control voltage Vcc rises. Since the motor 12 has not been started, even when the control voltage Vcc rises, the low-level voltage signal E1 is input to the negative terminal of the operational amplifier 133. Since the voltage E11 is E11> E1, the output voltage E12 of the operational amplifier 133 is at a high level. Since the output voltage E12 is charged in the capacitor 135 via the resistor 134, the voltage signal E13 becomes high level. The voltage signal E1 of the rectifying and smoothing circuit 121 is input to the plus terminal of the operational amplifier 129, and the voltage signal E2 is input to the minus terminal of the operational amplifier 129. The output voltage E3 of the operational amplifier 129 is at a low level because the motor 12 has not yet started and E1 <E2. The output voltage E23 of the operational amplifier 143 is at a low level because E22 <E21. Therefore, no current flows through the base of the transistor 147, the transistors 147 and 149 are turned off, no current flows through the relay coil of the relay 150, and the relay contact (b contact) is closed.

  When the motor 12 is started, the voltage signal E11 is set to about 10% of the rated current of the motor as described above, so that the output voltage E1 of the smoothing circuit 121 becomes E1> E11, and the output voltage of the operational amplifier 133 E12 changes from high level to low level. The charging voltage of the capacitor 135 is discharged through the resistor 134, and the voltage E13 changes from the high level to the low level. While the voltage E13 is at a high level, no current flows through the base of the transistor 147, the transistors 147 and 149 are turned off, no current flows through the relay coil of the relay 150, the relay contact is closed, and the motor 12 is energized.

At this time, if the starting current exceeds the value set by the variable resistor 125, the output voltage E3 of the operational amplifier 129 becomes high level, and the voltage signal E22 input to the plus terminal of the operational amplifier 143 E3 rises as capacitor 145 is charged through resistor 144. Although the output voltage E23 of the operational amplifier 143 also becomes high level, the charging voltage E13 of the capacitor 135 is discharged through the resistor 134, and the voltage E12 decreases. The voltage E13 is E13> E23-Vb-Vz
(Here, Vb is the base-emitter voltage of the transistor 148, and Vz is the Zener voltage of the Zener diode.)
During this time, no current flows through the base of the transistor 147, so the transistors 147 and 149 are non-conductive, no current flows through the relay coil of the relay 150, and power supply to the motor 12 is maintained.

  While the voltage E13 is E13> E23−Vb−Vz, when the motor 12 enters the rated operation and the motor current reaches the rated value, the output voltage E3 of the operational amplifier 129 becomes low level, and the charging voltage of the capacitor 145 becomes It is discharged through the resistor 134 and the voltage E22 becomes E22 <E21. The output voltage E23 of the operational amplifier 143 becomes low level, the voltage E13 remains at E13> E23−Vb−Vz, the base current does not flow through the transistor 147, the transistors 147 and 149 become non-conductive, and the relay coil of the relay 150 No current flows through the motor 12, and the current of the motor 12 is not interrupted.

  When the electric motor 12 is started in this manner, the rod 15 of the electric cylinder contracts and is crimped to another member related to the driven member, the current flowing through the motor 12 increases. The output voltage E31 of the operational amplifier 129 and the output voltage E23 of the operational amplifier 143 become high level. At this time, the charging voltage of the capacitor 135 is at a low level, and since the voltage E13 is E13 <E23−Vb−Vz, a current flows to the base of the transistor 147, the transistor 147 is turned on, and the transistor 147 Base current flows through resistor 148, transistor 149 conducts, current flows through the relay coil of relay 150, relay contact opens, current of motor 12 is interrupted, motor 12 stops, brakes Operate. The rod 15 continues to push the driven member against the other members by a spring force generated when the disc spring 23 of the spring unit 20 is compressed.

  This electric cylinder is used for an injection molding machine as shown in FIG. 4, for example. The injection molding machine includes a mold clamping mechanism, an injection mechanism, and a control device in the same manner as this known type.

The mold clamping mechanism includes a fixed platen, movable platen, mold clamping cylinder that opens and closes the mold, a tie bar that guides the opening and closing operation of the movable platen, a molded product ejector, and a safety door that prevents workers from being caught in the mold. It has. Of these, only the fixed platen 51 and the movable platen 52 are shown in FIG. Stationary platen 51 is fixed to a frame of the injection molding machine. The movable platen 52 is attached to the frame so as to be linearly movable so as to approach the fixed platen 51 and separate from the fixed platen 51. The mold includes a fixed mold 53 and a movable mold 54, and the fixed mold 53 is attached to the fixed platen 51, and the movable die 54 is attached to the movable platen 52.

The injection mechanism includes a hopper, a material supply device, a heating cylinder, a nozzle, an injection cylinder, and the like. Of these, the hopper and the material feeding device for storing the plastic material is housed in the injection mechanism body 55. The injection cylinder 56 transports, heats, melts, and injects the plastic material fed from the material supply device, and is fixed to the injection mechanism main body 55. The nozzle 57 is joined to the tip of the injection cylinder 56 and is in close contact with the spool bush 58 in the fixed mold 53 at the time of injection to form a molten plastic passage. The injection mechanism main body 55 is mounted on the frame so as to be rotatable in a horizontal plane and to be linearly movable toward the fixed platen 51.

  The electric cylinder according to the present invention is attached to the injection molding machine by connecting the tip tool 22 of the spring unit 20 to the injection mechanism main body 55 by a joint 58 and connecting the bracket 14 to the stationary platen 51 by a joint 59. The injection cylinder 56, the nozzle 57, and the injection mechanism main body 55 as drive members are linearly moved toward the fixed platen 51, or these are rotated back and forth on the paper surface of FIG.

Electric drive unit 30, power supply circuit 31 form part of a control device of the injection molding machine, to the operation unit 42, the pressing force detection circuit 32 is incorporated in the control panel 43.

  In the injection molding, the mold clamping cylinder is operated, the molds 53 and 54 are closed, the electric cylinder is operated, the injection mechanism main body 55 is linearly moved, the nozzle 57 is pressure-bonded to the nozzle touch part or the spool bush 58, and melted. After the plastic is injected from the nozzle 57 into the cavity formed between the molds 53 and 54, the injection mechanism main body 55 is returned to the original position by the electric cylinder, and the molds 53 and 54 are opened.

  When the operator closes the molds 53 and 54 and the operator selects the operation direction of the electric cylinder by the operation device 42, the electric motor 12 is operated and the rod 15 is contracted. As a result, the injection mechanism main body 55 and the injection cylinder 56 are moved to the left in FIG. At this time, the nut 17 of the screw shaft 16 is positioned at the inner end of the outer cylinder 13 and comes into contact with a stop 29 incorporated in the bracket 14, but the disc spring 23 of the spring unit 20 is bent to reduce the impact. The screw shafts 16 and 17 are protected. At the same time, the pressing force of the nozzle 57 against the spool bush 58 is maintained by the deflection of the disc spring 23.

  When the nozzle 57 comes into close contact with the spool bush 58 of the fixed mold 53, the current value of the electric motor 12 increases. The pressing force detection circuit 32 of the electric drive unit 30 opens the relay contact of the interruption circuit 33 of the power supply circuit 31 and stops power supply to the motor 12. Further, in order to open the molds 53 and 54, the operator rotates the electric motor 12 in the opposite direction by the operating device 42, the rod 15 is extended and returns to the state shown in FIG. 4, and the injection mechanism main body 55 moves to the initial position. When the stop is applied, the value of the current flowing through the motor 12 increases, and the electric drive unit 30 stops the power supply to the motor 12. During these molding operations, even if a large current flows through the electric motor 12 of the electric cylinder when the nozzle 57 moves away from the spool bush 58 due to an unexpected overload, the pressing force detection circuit 32 is connected to the power supply circuit 31. The relay contact of the interruption circuit 33 is opened, and power supply to the electric motor 12 is interrupted.

  To replace the spring unit 20, the joint 58 that connects the tip 22 of the spring unit 20 and the injection mechanism main body 55 is removed, the retaining pin 28 is extracted, the connecting pin 27 is extracted, the spring unit 20 is extracted from the rod 15, The spring unit 20 is inserted into the rod 15 and connected to the rod 15 by a connecting pin 27 and a stop pin 28. The stop point of the electric motor 12 is determined by operating the electric motor 12, rotating the knob of the variable resistor in the operation device 42, and stopping the rotation of the knob when a predetermined pressing force is reached. For this reason, the replacement of the spring unit 20 does not require disassembly of the electric cylinder, and does not require any work of operating the cylinder while moving the position of the limit switch and repeating these operations. It can be done quickly.

  Furthermore, the electric cylinder according to the present invention can prevent the mold from falling off when the mold is mounted on the fixed plate and the movable plate by a magnetic force. Depending on the shape of the molds 53 and 54, the adsorption force to the fixed platen 51 and the movable platen 52 becomes smaller than the pressing force of the electric cylinder, and the molds 53 and 54 drop off when the nozzle 57 is pressed against the spool bush 58. May end up. However, in the electric cylinder according to the present invention, the pressing force setting circuit 36 can continuously change the voltage value as a reference of the pressing force, so that, for example, the voltage value corresponding to the pressing force can be changed by a variable resistor. When the pressing force setting circuit 36 is incorporated in the operation device 42, the operator can prevent the molds 53 and 54 from falling off by rotating the operation knob of the variable resistor.

Thus, the electric cylinder according to the present invention can be performed by removing the connecting pin 27, replacing the spring unit 20 with a new spring unit 20, inserting the connecting pin 27, and inserting the stop pin 28. at the outside of the cylinder body 11, without requiring any disassembly of the electric cylinder, the replacement of the spring unit 20 can line Ukoto, moreover, also the pressing force setting for the new spring unit 20 was replaced, the electric drive unit Since it can be performed only by changing the output voltage of the pressing force setting circuit 36 included in the pressing force detection circuit 32 of 30, that is , the operation of operating the electric cylinder and repeating the position adjustment of the limit switch is not required at all. The replacement of the spring unit 20 can be performed very easily and in a short time.

Further, since the disc spring 23 of the spring unit 20 bends at the stroke end of the rod 15 to gently contact the nut 17 and the stop 29, the screw shaft 16 and the nut 17 are hardly damaged.

  Furthermore, since the value of the current flowing through the electric motor 12 is gradually increased by the spring unit 20, voltage detection by the pressing force detection circuit 32 can be performed accurately.

  In the embodiment described above, the pressing force setting circuit 36 of the electric drive unit 30 is configured to generate a discontinuous reference voltage in which a continuous reference voltage is output by a variable resistor. Also good. For example, a plurality of reference voltages are generated by a plurality of fixed resistors, and these are selected by a rotary switch so that the electric drive unit can be used in common for electric cylinders having different thrusts. May be.

1 is a side view with a part broken away showing an embodiment of an electric cylinder of the present invention. It is explanatory drawing which shows the structure of the circuit which drives the electric cylinder shown in FIG. FIG. 3 is an explanatory diagram illustrating an example of a specific configuration of the circuit illustrated in FIG. 2. It is explanatory drawing which shows the use condition of the electric cylinder shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Cylinder main body 12 ... Electric motor 13 ... Outer cylinder 14 ... Bracket 15 ... Rod 16 ... Screw shaft (ball screw)
17 ・ ・ ・Nut (ball screw)
18 ・ ・ ・ Gear train 20 ・ ・ ・ Spring unit 21 ・ ・ ・ Unit body 22 ・ ・ ・ Tip tool 24, 25 ・ ・ ・ Spring receiver 26 ・ ・ ・ Shaft portion of tip tool 27 ・ ・ ・ Connecting pin 28 ・ ・・ Stop pin 29 ・ ・ ・ Stop 30 ・ ・ ・ Electric drive unit 31 ・ ・ ・ Power feeding circuit 32 ・ ・ ・ Pushing force detection circuit 33 ・ ・ ・ Breaking circuit 34 ・ ・ ・ Rotation direction selection circuit 35 ・ ・ ・ Motor current detection Circuit 36 ... Pushing force setting circuit 37 ... Comparison circuit 38 ... Start timer circuit 39 ... Overcurrent timer circuit 41 ... Shut-off control circuit 42 ... Injection molding machine operator 43 ...・ Control panel of injection molding machine 51 ・ ・ ・ Fixed platen 52 ・ ・ ・ Movable platen 53 ・ ・ ・ Fixed mold (mold)
54 ・ ・ ・ Movable type (mold)
55 ... Injection mechanism main body 56 ... Injection cylinder 57 ... Nozzle 58 ... Spool bush 59 ... Joint

Claims (1)

An electric motor,
A motion conversion mechanism that is disposed between the electric motor and the rod and converts rotation of the electric motor into linear motion of the rod;
Is disposed between the driven member connected to said rod and the rod, the tip of the rod to maintain as well as alleviate the impact at the time of pressing operation of the rod by an elastic force, the pressing force during the pressing operation is stopped A spring unit attached to the
An electric drive unit for supplying electric power to the electric motor and stopping power supply to the electric motor when a value of the supplied electric power exceeds a preset reference value ;
The electric cylinder includes a start timer circuit and an overcurrent timer circuit .

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