JP3871334B2 - Push-stop electric cylinder - Google Patents

Description

  The present invention relates to an electric cylinder that converts rotational motion by a motor with a brake mechanism into linear motion by a screw shaft and a nut screwed to the screw shaft, and expands and contracts the rod. More specifically, the rod is overloaded. The present invention relates to a pressing stop type electric cylinder having a function of automatically stopping a motor with a brake mechanism.

In a so-called electric cylinder in which a rod is extended and contracted by screwing a nut to a rotationally driven screw shaft, it is necessary to prevent the rod from being overloaded.
For this reason, a motor with a brake mechanism equipped with a brake that forcibly brakes the rotating shaft by stopping power feeding is used as the motor for rotational drive, and the screw shaft can be moved while being urged in the axial direction by a spring mechanism. A limit switch type electric cylinder that stops power supply to a motor with a brake mechanism by detecting the bending of a spring at the time of pressing a rod with a limit switch is known (for example, see Patent Document 1). .

There is also known a motor current detection type electric cylinder that stops power feeding to a motor with a brake mechanism by detecting an increase in motor current when the rod is pressed (see, for example, Patent Document 2).
Japanese Patent Publication No.58-33431 JP 2002-176746 A

However, in such a conventional limit switch type electric cylinder, since the striker is moved by the bending of the spring to operate the limit switch, it takes a lot of man-hours to adjust the operating point of the limit switch and the pressing force It was difficult to adjust and change.
In addition, since wiring from the limit switch to the control device is required, improvements have been demanded in terms of reducing the size and weight of the device configuration and reducing manufacturing costs.

  In both limit switch and motor current detection electric cylinders, braking by the brake mechanism is performed at the same time as power supply to the motor with the brake mechanism is stopped. That is, the rotation shaft of the motor with the brake mechanism rotates due to inertia. During the operation, since the braking operation by the brake mechanism is performed, the wear of the lining of the brake mechanism is severe, which hinders the extension of the life of the device and the maintenance-free operation.

  Furthermore, the rod pressing force changes due to the rotation of the rotating shaft during the braking time required from when the power supply to the motor with the brake mechanism is stopped until the rotation of the motor with the brake mechanism is completely stopped by braking by the brake mechanism. It was difficult to accurately control the pressing force.

  Accordingly, an object of the present invention is to solve the above-described problems of the conventional electric cylinder, that is, in a state where the rotation shaft of the motor with the brake mechanism is restrained and the rotation of the motor with the brake mechanism is stopped. The brake mechanism can be operated in close contact with the brake plate without sliding, greatly reducing lining wear, extending the life of the equipment, reducing running costs, improving quietness, and reducing the pressing force. An object of the present invention is to provide a pressing stop type electric cylinder capable of improving the control accuracy.

  The invention according to claim 1 is a rod supported so as to be able to protrude and retract with respect to the housing, a screw shaft that is screwed into a nut fixed to the rod, a motor with a brake mechanism that drives the screw shaft to rotate forward and backward, In a pressing stop type electric cylinder provided with a control device for controlling the motor with a brake mechanism, the screw shaft is supported so as to be free to move in the axial direction with respect to the housing, and is generated by the axial movement of the screw shaft. A spring mechanism that absorbs a directional force is mounted between the screw shaft and the rotating shaft of the motor with the brake mechanism, and the brake mechanism of the motor with the brake mechanism is a lining that puts the rotating shaft into a braking state or a released state; A brake plate, and the controller locks the rotating shaft by operating the brake mechanism after the rotating shaft is restrained by an external force applied to the rod. And it is characterized in that it is configured to perform a series of motor control that stops the power supply to the brake mechanism with the motor after actuation of the brake mechanism.

  In addition to the configuration of the pressing stop type electric cylinder according to claim 1, the pressing stop type electric cylinder according to claim 2 has a function in which the control device detects the restraint state of the rotating shaft by detecting the motor current. By providing, the further solution of the subject mentioned above is aimed at.

  Furthermore, in the pressing stop type electric cylinder according to claim 3, in addition to the configuration of the pressing stop type electric cylinder according to claim 2, the control device indicates that the motor current continuously exceeds the reference value for a predetermined time. By detecting this, the above-described problem is further solved by further providing a function of detecting the restrained state of the rotating shaft after a certain period of time has elapsed since the start of the motor with the brake mechanism.

  According to the first aspect of the present invention, a rod supported so as to be able to protrude and retract with respect to the housing, a screw shaft that is screwed into a nut fixed to the rod, and a motor with a brake mechanism that drives the screw shaft to rotate forward and backward. In the pressing stop type electric cylinder provided with the control device for controlling the motor with the brake mechanism, the screw shaft is supported so as to be free to move in the axial direction with respect to the housing, and the axial direction generated by the free movement of the screw shaft in the axial direction is supported. A spring mechanism for absorbing force is mounted between the screw shaft and the rotating shaft of the motor with the brake mechanism, and the brake mechanism of the motor with the brake mechanism includes a lining and a braking plate for bringing the rotating shaft into a braking state or a releasing state; The controller locks the rotating shaft by operating the brake mechanism after the rotating shaft is restrained by an external force applied to the rod, and after the brake mechanism is operated By being configured to perform a series of motor controls to stop power supply to the motor with the rake mechanism, the rotation shaft of the motor with the brake mechanism is restrained, and the rotation of the motor with the brake mechanism is stopped. Since the brake mechanism operates with the lining and the brake plate in close contact with each other without sliding, the wear of the lining of the brake mechanism is greatly increased compared to the case where the brake is operated while a conventional motor with a brake mechanism is rotating. Thus, the life of the apparatus can be extended, the running cost can be reduced, the silence can be improved, and the control accuracy of the pressing force can be improved.

  Further, according to the pressing stop type electric cylinder according to claim 2, in addition to the effect exerted by the pressing stop type electric cylinder according to claim 1, the control device causes the motor current to continuously exceed the reference value for a predetermined time. In order to provide a configuration for detecting the restraint state of the rotating shaft by providing a function for detecting the restraining state of the rotating shaft, a special part such as a rotation detection sensor is incorporated in the apparatus main body. This eliminates the need for simplifying, downsizing, and reducing the manufacturing cost of the apparatus configuration and enables more accurate control of the pressing force.

  Furthermore, according to the pressing stop type electric cylinder according to claim 3, in addition to the effect exerted by the pressing stop type electric cylinder according to claim 2, the braking device takes into account the starting current of the motor with the brake mechanism, By further providing a function of detecting the restraint state of the rotating shaft after a certain period of time has elapsed since the start of the motor with motor, malfunction due to the starting current of the motor with brake mechanism is avoided, and the reliability of the apparatus is improved.

  Hereinafter, an embodiment of the pressing stop type electric cylinder of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram illustrating the main part of the apparatus as a cut surface in order to explain the apparatus configuration of the pressing stop type electric cylinder according to the present invention.

As shown in FIG. 1, the pressing stop type electric cylinder 10 includes a rod 14 supported so as to be able to protrude and retract with respect to a housing 12, a screw shaft 18 screwed into a nut 16 fixed to the rod 14, and the screw A motor 22 with a brake mechanism that drives the shaft 18 to rotate forward and reverse, and a control device 20 that controls the motor 22 with the brake mechanism are provided.
Then, by connecting the support shaft 19 extended to the screw shaft 18 and one rotating shaft 24a of the motor 22 with a brake mechanism with a coupling metal fitting 26 with a gap between the end portions of the respective shafts, The screw shaft 18 is supported so as to be freely movable in the axial direction with respect to the housing 12.

The other rotating shaft 24b of the motor 22 with a brake mechanism is a so-called non-excitation actuating type (spring braking type) in which the rotating shaft 24b is released during power feeding and the rotating shaft is braked when power feeding is stopped. The electromagnetic brake is installed.
This electromagnetic brake is brought into close contact with the brake plate 42 by being urged by a brake spring 44 that also serves as a motor air-cooling fan 42a fixed to the tip of the rotary shaft 24b of the motor with a brake mechanism, and when not supplied with power. An armature 43 with a lining 41 and a magnet coil 45 that generates a magnetic field by feeding are provided.
By supplying power to the magnet coil 45, the armature 43 is instantaneously attracted to the magnet coil side, a gap is generated between the lining 41 and the brake plate 42, and the braking state of the rotating shaft 24b is completely released, so that the brake The motor with the mechanism starts to rotate.
On the contrary, when the power supply to the magnet coil 45 is stopped, the attractive force of the magnet coil 45 disappears, the armature 43 is pushed back to the brake plate 42 side by the brake spring 44, and the lining 41 contacts the brake plate 42. A braking force is generated between the two, and the motor with the brake mechanism enters a braking state.

  In this embodiment, the non-excitation operation type electromagnetic brake as described above is used as the brake mechanism 40. However, power is supplied to an application in which the brake is released at the time of a power failure and no pressing force is required. It is also possible to use an excitation actuated electromagnetic brake in which the brake plate and the lining come into contact with each other to enter a braking state.

  The method of connecting the rotating shaft 24 while allowing the support shaft 19 to move freely in the axial direction by the connecting metal fitting 26 is not particularly limited. A key groove (concave portion) that extends slidably and a key groove (concave portion) that slidably engages therewith is formed on the inner peripheral surface of the coupling metal 26, and the support shaft 19 is pivoted by engaging both of them. The rotary shaft 24 can be connected in a state in which it can freely move in the direction.

Further, a spring mechanism 30 that absorbs an axial force generated by the axial movement of the screw shaft 18 is mounted between the screw shaft 18 and the rotating shaft 24a of the motor with a brake mechanism. If the spring mechanism 30 can smoothly absorb the axial movement of the screw shaft 18 and can create an elastic force that antagonizes the required pressing force, the structure and the type of spring are as follows: It is not particularly limited.
As shown in FIG. 1, the spring mechanism 30 used in this embodiment has a pair of bottomed cylindrical spring holders 34 each having an insertion hole in the center of the bottom surface, and a radial ball bearing 32 fixed to the outside of each bottom surface. Coil springs 38 that can be expanded and contracted are loaded inside the spring holders 34 so that the opening sides face each other.
Then, the spring holder 34 is brought into sliding contact with the inner peripheral surface of a single cylindrical member 36 having a stepped end portion 36 a fixed in the housing 12, and the support shaft 19 is supported by two radial ball bearings 32. is doing. A stopper 17 formed in an enlarged shape is fixed to the end of the screw shaft 18 and is in contact with one radial ball bearing 32.

  Since the spring mechanism 30 having such a structure is used, the support shaft 19 rotates smoothly without being affected by the presence of the spring mechanism 30, and the movement of the spring holder 34 in the axial direction is reliably performed. Furthermore, since the entire end surface of the coil spring 38 abuts against the bottom surface of the spring holder 34, no twisting or twisting occurs when the coil spring is expanded or contracted.

  Next, the operation of the pressing stop type electric cylinder according to the present invention will be described based on the operation explanatory diagram shown in FIG. 2 and the timing chart shown in FIG.

  FIG. 2A shows a state in which the electric cylinder is driven in an unloaded state without joining the driven member to the rod 14 and the tip of the rod 14 protrudes from the fixed position S. That is, the spring mechanism 30 is in a free state, and no pressing force is generated at the tip of the rod 14.

FIG. 2B shows a state in which the driven member 50 is joined to the rod 14 to drive the electric cylinder, and the tip end of the rod 14 is pressed at the fixed position S.
That is, although the screw shaft 18 is rotated by the driving force of the motor 22 with the brake mechanism, the rod 16 is restrained at the fixed position S, so that the nut 16 fixed to the rod 14 moves forward. As a reaction, the screw shaft 18 supported so as to be freely movable in the axial direction moves backward.
As a result, the spring mechanism 30 is degenerated, and an elastic force according to the Hooke's law is generated on the rod 14 as a pressing force.
Further, when the rotation of the motor 22 with brake mechanism is continued, the torque and the pressing force of the motor 22 with brake mechanism finally antagonize and the rotation of the motor 22 with brake mechanism is restricted.

After detecting that the rotation shaft 24a of the motor 22 with brake mechanism is restrained, the brake mechanism 30 of the motor 22 with brake mechanism is operated to brake the rotation shaft 24b as shown in FIG. Put it in a state.
At this time, since the rotation shaft 24a of the motor 22 with the brake mechanism is already constrained, the rotation of the brake plate 42 is stopped, so that the brake plate 42 and the lining 41 are brought into close contact with each other without causing the rotation shaft 24b to slide. Locked.
Therefore, as compared with the case where the brake is operated while the motor with the brake mechanism is rotating, the lining wear is remarkably reduced, and the life of the electric cylinder can be greatly extended. In this way, after the rotating shaft is locked by the brake mechanism 30, the power supply to the motor 22 with the brake mechanism is stopped. Therefore, the pressing force created by the elastic force of the spring mechanism 30 is maintained without the rotating force being reversed after the power supply to the motor 22 with brake mechanism is stopped and the pressing force being reduced.

A series of control regarding the motor 22 with a brake mechanism mentioned above is performed by the control apparatus 20 attached to an electric cylinder.
Here, various methods such as detection by a rotation sensor can be used to detect the rotational shaft restraint state. However, the motor current is detected, and based on the change in the current value, the rotational shaft is restrained. It is particularly preferable that the control device 20 has the function to perform the simplification of the device configuration and accurate control of the pressing force.
Further, by providing the control device 20 with a function of detecting the restraint state of the rotating shaft after a certain period of time has elapsed since the start of the motor with the brake mechanism, the rotating shaft becomes constrained due to a transient increase in the motor current at the start. Therefore, it is possible to further improve the reliability of the apparatus.

A series of motor control performed by the control device 20 will be described in detail with reference to the time chart shown in FIG.
3A shows the change in the rotational speed of the motor with the brake mechanism, FIG. 3B shows the brake current of the motor with the brake mechanism, FIG. 3C shows the operating state of the electromagnetic brake, and FIG. Is the output voltage when the DC voltage Vcc of the control power supply circuit 210 is input to the integrating circuit of a predetermined time constant, FIG. 3 (e) is a voltage value proportional to the motor current, and FIG. The pressing force generated by the cylinder is shown, and the vertical axis shows the change of each value, and the horizontal axis shows the time from the start of the motor.

At the time 0, the electric cylinder is started, and at the same time, the motor with the brake mechanism is connected to the drive power source, and a current flows through the brake mechanism as shown in FIG. 3B, and at time t1 as shown in FIG. The electromagnetic brake is completely released, and the rotary shaft of the motor with the brake mechanism is unlocked.
When the lock of the rotating shaft is released, the rotational speed of the motor with the brake mechanism gradually increases as shown in FIG. 3A, reaches the steady speed at time t2, and the voltage between the terminals of the motor with the brake mechanism and The motor current also reaches a steady value.

When the rod end of the cylinder reaches the fixed position at time t3, the spring mechanism starts to degenerate and receives the elastic force of the spring mechanism, and the rotational speed of the motor with the brake mechanism gradually decreases as shown in FIG. At the same time, since the torque of the motor with the brake mechanism increases, the motor current increases as shown in FIG.
At this time, as shown in FIG. 3F, a pressing force equal to the elastic force of the spring mechanism is generated on the rod. When it is detected that the voltage value proportional to the motor current has reached the reference value E4 (time t4), it is determined that the rotating shaft of the motor with the brake mechanism is substantially restrained, and then a predetermined time T2 has elapsed (time t6). In addition, as shown in FIG. 3B, the brake current is stopped to lock the rotating shaft. The value of T2 is set to a value larger than the time Ts required from when the voltage value E3 proportional to the motor current reaches the reference value E4 until the rotation of the motor with the brake mechanism completely stops.

Here, when the rotation shaft of the motor with the brake mechanism is completely restrained, that is, when the rotation speed becomes 0, not the voltage value E0 proportional to the motor current but E4 which is a value lower than E0 as a reference value. The reason why the stop of the brake current is controlled is that the voltage value E0 is a critical value (asymptotic value). If this value decreases for some reason, the brake current is not stopped forever, and the motor with the brake mechanism This is because there is a risk of overloading.
In order to avoid this, the stability of the control is improved by stopping the brake current after a predetermined time T2 has elapsed after reaching the reference value E4.
Further, as shown in FIG. 3 (e), a transient starting current flows through the motor with the brake mechanism immediately after the motor with the brake mechanism is started, and the voltage value E3 proportional to the motor current temporarily exceeds the reference value E4. Therefore, the reliability of the control can be improved by not performing the above-described control until a predetermined time T1 has elapsed after the start of the motor with the brake mechanism.

  A series of motor control is completed by stopping the power supply to the motor with the brake mechanism after a predetermined time T3 has elapsed (time t8) after the brake current is stopped. The value of T3 is set to a value larger than the time Tc required from when the brake current is stopped until the rotation of the motor with the brake mechanism is completely locked.

The control as described above can be performed by various methods such as a sequential control device combining a relay circuit and a delay circuit, and program control using a microcomputer.
In this embodiment, the control circuit is configured by an electronic circuit using an arithmetic circuit (OP amplifier), a comparison circuit (comparator), and the like. Hereinafter, the control circuit used in this embodiment will be described with reference to FIG.

FIG. 4 shows a circuit diagram of the control device 200 used in this embodiment. The control device includes circuit units of a control power supply circuit 210, a start circuit 230, a motor current detection circuit 240, a pressing detection circuit 250, a brake control circuit 260, a motor control circuit 270, and a brake power supply circuit 280.
Hereinafter, motor control by the control device 200 will be described in the case where the motor 220 with a brake mechanism is rotated forward, that is, when the electric cylinder is moved forward.

Although not shown, when the forward (forward) electromagnetic contactor is closed, three-phase AC power is supplied to the terminals U1, V1, and W1 of the control device 200, and the AC voltage between the terminals U1 and W1 is controlled. Input to the power supply circuit 210.
Then, the control power supply circuit 210 outputs a DC voltage Vcc. The DC voltage Vcc is divided by two resistors 211 and 212 connected in series, and the divided voltage E1 is output to the starting circuit 230, the pressing detection circuit 250, and the brake control circuit 260.

  The divided voltage E1 is input to the negative terminal of the comparator 233 of the starting circuit 230. Further, the output voltage E2 of the integrating circuit composed of the resistor 231 and the capacitor 232 is input to the + terminal of the comparator 233. At this time, according to the time constant defined by the values of the resistor 231 and the capacitor 232, the output voltage E2 of the integrating circuit rises with a delay from the rise of the DC voltage Vcc.

While E1> E2, the output E7 of the comparator 233 is at a low level (Low), is output to the brake control circuit 260, and is input to the + terminal of the comparator 261. The voltage E1 obtained by dividing the DC voltage Vcc by the resistors 211 and 212 is input to the negative terminal of the comparator 261.
At this time, since E7 <E1, the output E8 of the comparator 261 becomes a low level (Low), and the primary side of the two photocouplers 263 and 264 connected in series from the DC voltage Vcc through the resistor 262. Current flows through
The secondary side of one photocoupler 263 is output to the brake power supply circuit 280, and the secondary side of the other photocoupler 264 is output to the outside. The output E8 of the comparator 261 is output to the motor control circuit 270.

On the other hand, the brake power supply circuit 280 operates as follows. When the AC voltage Va is applied between the terminals U1 and W1 of the control device 200, the voltage E13 is output from the half-wave rectifier circuit formed by the diodes 281 and 282, and is configured by the resistor 283, the capacitor 284, and the Zener diode 285. The gate power supply circuit inputs the gate power supply voltage E11 from the gate power supply circuit.
When a current flows to the primary side of the photocoupler 263 of the brake control circuit 260 described above, the secondary side of the photocoupler 263 is turned on, and the resistor 286 connected in parallel between the gate and source of the FET 287 by the gate power supply voltage E11. Current flows, the voltage between the gate and the source of the FET 287 becomes high (High), and the FET 287 becomes conductive. When the FET 287 is turned on, the voltage E13 output from the half-wave rectifier circuit is applied to the magnet coil 223 of the electromagnetic brake, the brake current flows to the magnet coil 223, and the electromagnetic brake is released.

When the DC voltage Vcc of the control power supply circuit 210 rises, the voltage E1 divided by the resistors 211 and 212 is input to the negative terminal of the comparator 271 of the motor control circuit 270, and the DC voltage is applied to the positive terminal. The capacitor 276 is charged from Vcc through the resistor 274, and the charging voltage E9 that rises later than the DC voltage Vcc is input.
When the AC voltage Va is applied between the terminals U1 and W1 and the DC voltage Vcc of the control power supply circuit 210 starts to rise, E1> E9, and the output E10 of the comparator 271 becomes low level (Low) and is connected in series. A current flows from the DC voltage Vcc through the resistor 277 to the primary side of the two photocouplers 7a and 8a, and the secondary side becomes conductive.

  When the secondary sides of the photocouplers 7a and 8a are turned on, gate currents If and Ig flow to the gates of the semiconductor switches 7 and 8 through the resistors 7b and 8b connected to the respective photocouplers. Conduction occurs, and current flows through the motor 221.

Further, when a low level (Low) output E8 is input from the comparator 261 to the motor control circuit 270 by the brake control circuit 260, a current flows from the DC voltage Vcc through the resistors 274 and 273 and the diode 272, and the capacitor 276 Voltage E9 remains E9 <E1, the output E10 of the comparator 271 is kept at a low level (Low), current flows to the primary side of the photocouplers 7a and 8a, and the secondary side becomes conductive, and the resistor Through the gates 7b and 8b, the gate currents If and Ig flow to the gates of the semiconductor switches 7 and 8, the semiconductor switches 7 and 8 become conductive, and the current continues to flow to the motor 221.
As a result, a motor current flows through the motor 221 of the motor 220 with the brake mechanism, a brake current flows through the magnet coil 223 of the electromagnetic brake, the braking state of the electromagnetic brake is released, and the motor 221 starts.

  The motor current flowing through the motor 221 of the motor 220 with brake mechanism is detected by the current transformer 241 of the motor current detection circuit 240. Although the motor current (primary current) detected by the current transformer 241 is alternating current, the secondary current of the current transformer is input to the rectifying and smoothing circuit 242 and converted into a DC voltage E3 proportional to the magnitude of the motor current. , And input to the + terminal of the operational amplifier 246.

  A DC voltage E4 obtained by dividing the DC voltage Vcc by the resistors 243 and 245 and the variable resistor 244 is input to the negative terminal of the operational amplifier 246. When the electric cylinder is in a pressing state and the pressing force increases, the motor current increases. It can be set in advance.

When an overload current flows due to a starting current or pressing state that flows when the motor 221 of the motor 220 with a brake mechanism is started, the DC voltage E3 proportional to the magnitude of the motor current input to the + terminal of the operational amplifier 246 is The DC voltage E4 (reference value) input to the negative terminal of the operational amplifier 246 becomes higher, and the output voltage E5 of the operational amplifier 246 becomes high (High).
On the other hand, when operating with a normal load, the DC voltage E3 proportional to the magnitude of the motor current input to the + terminal of the operational amplifier 246 is the DC voltage input to the − terminal of the operational amplifier 246. It becomes lower than E4 (reference value), and the output voltage E5 of the operational amplifier 246 becomes a low level (Low).

The output voltage E5 from the operational amplifier 246 of the motor current detection circuit 240 is input to an integration circuit including resistors 251 and 253 and a capacitor 252 of the pressing stop circuit 250, and an integrated value E6 as an output thereof is output from the comparator 256. Input to the + terminal.
On the other hand, the voltage E1 obtained by dividing the DC voltage Vcc by the resistors 211 and 212 is input to the negative terminal of the comparator 256. When the motor with a brake mechanism is started, a high level (High) output voltage E5 is input from the motor current detection circuit 240 to the integration circuit by the starting current, and the charging voltage of the capacitor 252 increases, and E6> E1 The output E7 of the comparator 256 is connected to the output of the comparator 233 of the starting circuit 230 described above, and since the output of the comparator 233 is low (low) for a certain time after the start of the motor with the brake mechanism, E7 is Low level (Low).
When the start of the motor with the brake mechanism is completed while the output of the comparator 233 is low (Low), the output of the comparator 256 is low (Low) before the output of the comparator 233 becomes high (High). )become. Therefore, E7 maintains a low level (Low) without malfunctioning due to the starting current.

When the motor with the brake mechanism rotates and the electric cylinder moves forward and becomes pressed, the spring of the electric cylinder is deflected, the motor current increases, and the E5 output voltage of the motor current detection circuit 240 becomes high level (High) again. . The delay time by the integration circuit is determined by the time constants of the resistor 251 and the capacitor 252 so that the time is slightly longer than the time during which the motor shaft is restrained by the reaction force due to the deflection of the spring.
Accordingly, when the electric cylinder is pressed, the motor shaft is restrained, and the motor current increases, E7 becomes high level (High).

  When E7 becomes high level (High), the charging current flows from Vcc to the capacitor 252 through the resistor 255, the diode 254, and the resistor 253, E6> E1, and the output of the comparator 256 is maintained at high level (High). The high level (High) state of E7 is maintained. When the motor current is cut off and E5 becomes low level (Low), current flows from Vcc to the operational amplifier 246 through the resistor 255, the diode 254, and the resistors 253 and 251, and E6> E1, and the comparator 256. Maintains the high level (High), and maintains the high level (High) state of E7.

  When E7 becomes high level (High), E1 and E7 input to the comparator 261 of the brake control circuit 260 become E7> E1, the output voltage E8 of the comparator 261 becomes high level (High), and the photocoupler The current flowing to the primary side of H.263, H.264 is cut off, the secondary side of the photocoupler 263 of the brake power supply circuit 280 is turned off, the gate voltage E12 becomes low level (Low), the FET 287 is turned off, and the brake The current is cut off.

  When the brake current is cut off, the motor current is flowing, but the torque and the pressing force are antagonizing, and the motor shaft is in a restrained state. The motor shaft is locked by the electromagnetic brake while the rotation of the motor shaft is completely stopped.

When E8 becomes a high level (High), a charging current flows from the DC voltage Vcc through the resistor 274 to the capacitor 276 of the motor control circuit 270, the charging voltage E6 of the capacitor 276 increases, and the resistor 274 and the capacitor 276 are turned on. After a time determined by a constant, E9> E1 and the output E10 of the comparator 271 becomes high level (High). When E10 becomes high level (High), the current flowing to the primary side of the photocouplers 7a and 8a is cut off, the secondary side is turned off, the gate currents If and Ig are cut off, and the semiconductor switches 7 and 8 are turned off. The motor current is cut off.
Even if the motor current is cut off, the motor shaft is locked by the electromagnetic brake, so that the electric cylinder maintains the pressing force due to the reaction force of the spring.

  The above is an outline of the control circuit of the present embodiment, but the specific configuration of the control circuit is not limited to this, and various configurations can be used as long as the technical idea of the present invention can be realized. It is possible to apply.

It is explanatory drawing which cut | disconnected a part which shows one Example of the electric cylinder of this invention. It is explanatory drawing explaining operation | movement of the electric cylinder shown in FIG. It is a time chart explaining operation | movement of the electric cylinder shown in FIG. It is explanatory drawing of the control apparatus used for the electric cylinder shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Stopping type electric cylinder 12 ... Housing 14 ... Rod 16 ... Nut 17 ... Stopper 18 ... Screw shaft 19 ... Support shaft 20 ... Control device 22 ... · Motor 24 · · · Rotary shaft 26 · · · Connection fitting 30 · · · Spring mechanism 32 · · · Radial ball bearing 34 · · · Spring holder 36 · · · Cylindrical member 36a · · · Stepped end 38 · · · Coil spring 40 ... Brake mechanism 41 ... Lining 42 ... Brake plate 42a ... Fan 43 ... Armature 44 ... Brake spring 45 ... Magnet coil 200 ... Controller 210 ... Control power supply circuit 220 ... Brake mechanism motor 230 ... Starting circuit 240 ... Motor current detection circuit 250 · Pressing detection circuit 260 ... brake control circuit 270 ... motor control circuit 280 ... Brake power circuit

Claims (3)

A rod supported so as to be able to move in and out with respect to the housing; a screw shaft screwed into a nut fixed to the rod; a motor with a brake mechanism that drives the screw shaft to rotate forward and reverse; and a motor with the brake mechanism. In the pressing stop type electric cylinder provided with the control device,
The screw shaft is supported so as to be axially movable with respect to the housing;
A spring mechanism that absorbs an axial force generated by the axial movement of the screw shaft is mounted between the screw shaft and the rotating shaft of the motor with the brake mechanism,
The brake mechanism of the motor with the brake mechanism includes a lining and a brake plate for bringing the rotating shaft into a braking state or a releasing state,
A sequence in which the control device locks the rotation shaft by operating the brake mechanism after the rotation shaft is restrained by an external force applied to the rod, and stops power supply to the motor with the brake mechanism after the operation of the brake mechanism. It is comprised so that motor control of may be performed, The pressing stop type electric cylinder characterized by the above-mentioned.   2. The control device according to claim 1, wherein the controller has a function of detecting a restraint state of the rotating shaft by detecting that the motor current continuously exceeds a reference value for a predetermined time. Pushing stop type electric cylinder.   The control device further has a function of detecting a restraint state of the rotating shaft after a predetermined time has elapsed after the start of the motor with the brake mechanism, in order to avoid malfunction due to a starting current of the motor with the brake mechanism. A pressing stop type electric cylinder according to claim 2,

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