JPH0223117Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electric actuator that drives an output arm using an electric motor, and is particularly suitable for controlling the supply of fuel to an internal combustion engine. The present invention relates to a type actuator.

[Prior Art] As shown in FIG. 1, this type of actuator includes a motor M, a main transistor switch T that turns on and off an armature current supplied to the motor from a DC power supply E, and a reduction gear and first and second position detection switches L1 and L2 that perform detection operations and close when the output arm A is in the first position P1 and the second position P2, respectively. When the drive command switch SW is closed, the output arm A is displaced from the first position P1 to the second position P2, and when the drive command switch SW is opened, the output arm A is displaced from the second position P2. Some devices are equipped with a control circuit C that controls the main transistor switch T so as to return it to the first position P1.

[Problem to be solved by the invention] The control circuit C used in the conventional actuator was configured to cut off the current to the motor M only when each position detection switch was performing a detection operation. However, in such a configuration, the output arm A is in the first position P1 or the second position P2 due to the inertia of the output arm A and the operated member (not shown) connected to the output arm, and the position detection switches L1 and L2 are If you go beyond the sensing area of
There was a problem that the electric motor rotated again and caused an overrun.

Furthermore, in conventional actuators, when the drive command switch SW is closed, a base current flows through the drive command switch to the main transistor switch T to make the main transistor switch conductive, and when the drive command switch SW is opened, the drive A capacitor charged while the command switch is closed is used as a power source, and the charge of the capacitor is discharged to the base current conducting path of the main transistor switch T, thereby making the main transistor switch T conductive. However, such a configuration requires the use of an expensive capacitor with a large capacity, and there is also the problem that the motor can only be rotated for a short period of time because the capacitor quickly discharges.

The purpose of this invention is to prevent the output arm from overrunning under any circumstances, and to reduce the capacitance of the capacitor that serves as a power source for supplying base current to the main transistor switch when the drive command switch is opened. The object of the present invention is to provide an electric actuator that has the following characteristics.

[Means for Solving the Problems] The present invention includes a DC power supply, a motor driven by the DC power supply, an output arm driven by the motor, and a motor in which the output arm is in a first position and a second position. first and second position detection switches that close when they respectively detect that the output arm is in the
The electric motor is controlled to displace the output arm from the second position to the second position, stop at the second position, and return the output arm from the second position to the first position when the drive command switch is opened. The present invention relates to an electric actuator equipped with a control circuit.

In the present invention, the control circuit includes a main transistor switch that turns on and off the current supplied to the motor from the DC power source, and a base current that flows from the DC power source to the main transistor switch through the drive command switch when the drive command switch is closed. A first base current supply circuit that conducts current, a capacitor that is connected to a DC power supply through a drive command switch and is charged by the DC power supply when the drive command switch is closed, and a base current conduction path of the main transistor switch. A first overrun prevention thyristor is connected in parallel to the main transistor switch and prevents the base current from being supplied from the first base current supply circuit to the main transistor switch when conductive; a first overrun prevention thyristor firing circuit that supplies a firing signal to the first overrun prevention thyristor through the second position detection switch; and a transistor switch circuit that conducts when a base current is applied by the charge of the capacitor. a second base current supply circuit that supplies base current from the DC power source to the main transistor switch through the transistor switch circuit; A second overrun prevention thyristor that prevents base current from being supplied from the current supply circuit to the main transistor switch; and a second overrun prevention thyristor from the DC power supply through the transistor switch circuit and the first position detection switch. A second overrun prevention thyristor ignition circuit that provides an ignition signal, and a transistor switch for disconnection control that is connected in parallel to the base current carrying path of the transistor switch circuit and that disconnects the transistor switch circuit when conductive. and a cutoff control transistor switch trigger circuit that supplies a base current from a DC power supply to the cutoff control transistor switch through a drive command switch.

[Function] With the above configuration, when the output arm reaches the first and second positions and the second and first position detection switches are closed, the first and second overrun prevention thyristors are activated. Since it continues to conduct and prevents the supply of base current to the main transistor switch, even if the output arm passes over the sensing area of the position detection switch due to inertia, the arm can be stopped reliably, and the output arm will not overrun. can be prevented.

In addition, as mentioned above, a transistor switch circuit is provided which is turned on by supplying a base current with the charge of the capacitor that is charged while the drive command switch is closed, and the base current is supplied from the DC power source to the main transistor switch through the transistor switch circuit. If configured to supply the base current to the main transistor switch, the discharge current of the capacitor required to continue flowing the base current to the main transistor switch can be reduced, so a capacitor with a small capacity can be used as the capacitor. Base current can continue to flow through the main transistor switch for a long time.

[Embodiments] Examples of the present invention will be described below with reference to the accompanying drawings.

Figure 2 shows an embodiment of the present invention, in which E is a DC power source consisting of a battery, etc., and M
is an electric motor that drives the output arm of the actuator, T is a main transistor switch consisting of an NPN transistor, and SW is closed when moving the output arm from the first position to the second position; This is a drive command switch that is opened when the switch is returned to the first position.

A resistor 2 is connected in parallel to both ends of an armature 1 of a motor M, one end of which is connected to the positive terminal of a DC power supply E, and the other end connected to the collector of an NPN transistor 3 constituting a main transistor switch T. It is connected. The emitter of the transistor 3 is connected to the anode of a diode 4 whose cathode is grounded, and the cathodes of diodes 5 and 6 are commonly connected to the base of the transistor. One end of a resistor 7 is connected to the anode of the diode 5, and the other end of the resistor 7 is connected to the positive terminal of a DC power source E through a drive command switch SW. In this example, a transistor 3 is connected from a DC power source E through a drive command switch SW, a resistor 7, and a diode 5.
Drive command switch
When SW is closed, the main transistor switch T
A first base current supply circuit is configured to supply a base current to.

When the drive command switch SW is closed, the base current is supplied from the DC power supply E through the drive command switch SW to the base current conduction path of the main transistor switch T (in this example, between the base and emitter of transistor 3). T becomes conductive and armature current is supplied to motor M. As a result, the electric motor M rotates, and the output arm A rotates clockwise from the first position P1 to the second position P2 in FIG.

Reference numeral 8 denotes a first overrun prevention thyristor, and this thyristor is connected in parallel to the base current conducting path of the main transistor T. To explain in more detail, the anode of the thyristor 8 is the diode 5.
The cathode of the thyristor is connected to the emitter of the transistor 3, and when the thyristor 8 is turned on, the DC power supply E is connected to the drive command switch SW, the resistor 7, and the diode 5 (the first base current supply circuit (through) to prevent base current from being supplied to the main transistor switch T.

A capacitor 9 is connected in parallel to both ends of the overrun prevention thyristor 8. A capacitor 10 and a resistor 1 are connected between the gate and cathode of the thyristor 8.
1 are connected in parallel, and the gate of the thyristor is connected to the connection point between the resistor 7 and the drive command switch SW through a series circuit of the resistor 12 and the second position detection switch L2. In this example, a circuit from a DC power source E through a drive command switch SW, a second position detection switch L2, and a resistor 12 to the gate of a thyristor 8 provides a first overrun prevention thyristor with an ignition signal. A thyristor ignition circuit for overrun prevention is configured.

When the drive command switch SW is closed, the electric motor M rotates, the output arm A reaches the second position P2, and the second position detection switch L2 is closed. A firing signal is applied to the first overrun prevention thyristor 8 through L2 and the resistor 12, and the thyristor becomes conductive. When this thyristor 8 becomes conductive, the base current to the main transistor switch T is bypassed from the main transistor switch, and the base current is prevented from being supplied to the main transistor switch, so that the main transistor switch T is cut off. , the electric motor M stops.

Once the thyristor 8 is conductive, even if the position detection switch L2 is opened, it remains conductive until the drive command switch SW is opened. Therefore, the output arm A may go too far over the sensing area of the second position detection switch L2 due to inertia and may not be detected. Even if the detection switch L2 is opened, the main transistor switch T remains cut off. Therefore, the output arm A will not overrun the second position.

The anode of the diode 6 connected to the base of the transistor 3 is connected to the collector of a PNP transistor 14 through a resistor 13, and the emitter of the transistor 14 is connected to the positive terminal of a DC power source E. A resistor 15 is connected in parallel between the base and emitter of the transistor 14, and the collector of an NPN transistor 17 is connected to the base of the transistor 14 through a resistor 16. The base of the transistor 17 is connected to the collector of the NPN transistor 18.
The emitter of transistor 17 and the emitter of transistor 3 are connected to each other.
The base of the transistor 19 is connected to the positive terminal of the DC power supply E through the resistor 19 and the drive command switch SW, and is also connected to the anode of the diode 4 through the resistor 20.
The base of 7 is connected to the cathode of a diode 22 through a resistor 21. The anode of the diode 22 is connected to the positive terminal of the DC power supply E through the drive command switch SW, and when the drive command switch SW is closed between the cathode of the diode 22 and the anode of the diode 4, the DC power supply E is connected.
A capacitor 23 that is charged by is connected. In this example, the drive command switch is controlled by transistors 14, 17 and resistors 15, 16, 21.
When the SW is opened, a base current is applied by the charge of the capacitor 23 to form a transistor switch circuit which becomes conductive. Furthermore, the transistor switch circuit, resistor 13, and diode 6 constitute a second base current supply circuit that supplies base current to the main transistor switch when the drive command switch is opened, and when the drive command switch SW is opened. When the transistors 17 and 14 are turned on, a base current is applied to the main transistor switch T through the emitter-collector circuit of the transistor 14, the resistor 13, and the diode 6.

When the drive command switch SW is opened and a base current is applied to the main transistor switch T through the transistor 14, the transistor switch T becomes conductive, the motor M rotates, and the output arm A
The first position P2 rotates toward the first position P1.

In this embodiment, the transistor 18 controls the transistor switch circuit (transistors 14, 1) when the drive command switch SW is closed.
7) is constituted by a transistor switch for cut-off control that maintains the cut-off state, and a circuit from the DC power supply E through the drive command switch SW and the resistor 19 to the base of the transistor 18 performs cut-off control from the DC power supply E through the drive command switch SW. A transistor switch trigger circuit for cut-off control is configured to supply a base current to the transistor switch for use.

That is, when the drive command switch SW is closed, the base current is supplied from the DC power supply E to the transistor 18 through the drive command switch SW and the resistor 19, so the transistor 18 becomes conductive, and the base current conduction path of the transistor switch circuit is closed. (in this example, the base-emitter circuit of transistor 17) is prevented from being supplied with current.
Therefore, transistors 17 and 14 are held in a cut-off state, and base current is prevented from being applied from DC power supply E through transistor 14 to main transistor switch T.

The base current supply circuit of the main transistor switch T also includes a second overrun prevention thyristor 2.
5 are connected in parallel, and when the thyristor 25 becomes conductive, base current is prevented from being supplied from the transistor 14 side to the main transistor switch T. In this example, the anode of the second overrun prevention thyristor 25 is the diode 6.
The cathode of the thyristor 25 is connected to the anode of the diode 4.

A capacitor 27 and a resistor 27 are connected in parallel between the gate and cathode of the thyristor 25, and the gate of the thyristor is connected to the collector of the transistor 14 through the resistor 28 and the first position detection switch L1. Transistor 1 from DC power supply E
4, the first position detection switch L1, and the resistor 28 to the gate of the thyristor 25 constitute a second overrun prevention thyristor ignition circuit that provides an ignition signal to the second overrun prevention thyristor 2. When the first position detection switch L1 is closed while the transistor 14 is conducting, an ignition signal is given to the thyristor 25.

Therefore, when the drive command switch SW is closed, the main transistor switch T becomes conductive and the motor M rotates, and when the output arm A returns to the first position and the first position detection switch L1 is closed, the DC power supply E to the transistor 14 and the first position detection switch L
An ignition signal is applied to the thyristor 25 through the resistor 28 and the resistor 28, and the thyristor 25 becomes conductive. When the thyristor 25 becomes conductive in this manner, the supply of base current to the main transistor switch T is blocked, so that the main transistor switch T is cut off. Since the thyristor 25 remains conductive until the discharge of the capacitor 23 is completed and the transistor 14 is cut off, the first position detection switch L is activated when the output arm A returns to the first position P1.
Even if the sensing area of 1 is exceeded, the main transistor switch T remains cut off. Therefore, the output arm A is prevented from overrunning the first position P1.

In addition, in FIG. 2, 30 is the transistor 14.
This is a protective varistor connected in parallel to both ends of the emitter-collector circuit, the first position detection switch L1, and the series circuit of the resistors 28 and 27.

In the above embodiment, for example, limit switches can be used as the first and second position detection switches L1 and L2. A non-contact switch such as a reed switch that is sensitive to the above can also be used as the position detection switch.

In addition, by combining a switch such as a limit switch or reed switch that performs a detection operation and opens when the output arm reaches the first position P1 or P2, and a switch circuit that closes when the switch opens, the detection operation can be performed. It is also possible to configure the first and second position detection switches to close when the operation is performed.

Further, the drive command switch SW does not necessarily have to be a contact switch, but may be a non-contact switch that operates when appropriate conditions are met or when an appropriate command is given.

[Effect of the invention] As described above, according to the invention, when the output arm reaches the first and second positions and the second and first position detection switches close, respectively, the first and second position detection switches Since the overrun prevention thyristor continues to conduct and blocks the supply of base current to the main transistor switch, even if the output arm passes over the sensing area of the position detection switch due to inertia, the arm can be stopped. This can prevent the output arm from overrunning.

In addition, in the present invention, a transistor switch circuit is provided which conducts by supplying a base current with the charge of the capacitor that is charged while the drive command switch is closed, and the base current is supplied from the DC power source to the main transistor switch through the transistor switch circuit. This makes it possible to reduce the discharge current of the capacitor required to keep the base current flowing through the main transistor switch, allowing the use of a capacitor with a small capacity. This has the advantage that the base current can continue to flow through the main transistor switch for a long time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall structure of an electric actuator to which the present invention is directed, and FIG. 2 is a circuit diagram showing an embodiment of the present invention. E...DC power supply, T...Main transistor switch, M...Motor, A...Output arm, C...Control circuit, L1...First position detection switch, L2
... Second position detection switch, SW ... Drive command switch, P1 ... First position, P2 ... Second position, 1 ... Armature, 3, 14, 17, 18 ...
Transistor, 8...first overrun prevention thyristor, 25...second overrun prevention thyristor, 23...capacitor.

Claims (1)

[Claims for Utility Model Registration] A DC power source, an electric motor driven by the DC power source, an output arm driven by the electric motor, and the output arm being in a first position and a second position, respectively. The first one that closes when detected
and a second position detection switch, which causes the output arm to move to the first position when the drive command switch is closed.
from the position to the second position.
an electric actuator comprising: a control circuit that controls the electric motor so as to stop the electric motor at the position and return the output arm from the second position to the first position when the drive command switch is opened; In the control circuit, the control circuit includes: a main transistor switch that turns on and off the current supplied from the DC power supply to the motor; and when the drive command switch is closed, the control circuit includes a main transistor switch that supplies current from the DC power supply to the main transistor switch through the drive command switch when the drive command switch is closed. a first base current supply circuit through which current flows; a capacitor connected to the DC power source through the drive command switch and charged by the DC power supply when the drive command switch is closed; and the main transistor switch. A first base current supply circuit that is connected in parallel to the base current conduction path of the first base current supply circuit to prevent base current from being supplied to the main transistor switch when the first base current supply circuit becomes conductive.
a first overrun prevention thyristor firing circuit that provides a firing signal from the DC power source to the first overrun prevention thyristor through the drive command switch and the second position detection switch; , a second base current supply circuit comprising a transistor switch circuit that conducts when a base current is applied by the charge of the capacitor, and supplies a base current from the DC power supply to the main transistor switch through the transistor switch circuit; A second base current supply circuit that is connected in parallel to the base current conduction path of the transistor switch and prevents base current from being supplied to the main transistor switch from the second base current supply circuit when conductive.
a second overrun prevention thyristor ignition circuit that provides an ignition signal from the DC power source to the second overrun prevention thyristor through the transistor switch circuit and the first position detection switch; , a transistor switch for cut-off control that is connected in parallel to the base current carrying path of the transistor switch circuit and turns the transistor switch circuit into a cut-off state when conductive; An electric actuator comprising a transistor switch trigger circuit for cutoff control that supplies a base current to a transistor switch for use in the circuit.