JP2003216207A - Controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an increase in temperature because large power is consumed by a circuit for detecting the state of a switch in a controller for controlling a control object in accordance with the state of the switch with a contact for a command or detection. <P>SOLUTION: When switches 2 and 3 with a contact are on, a rated contact current is caused to flow through resistors 12 and 13, and the voltages across both ends of the resistor 12 and the voltages across both ends of the switch 3 are inputted to a control part 8 to detect the states of the switches 2 and 3. Switches 20 and 22 which are turned on when the switches 2 and 3 are on and turned off just after the voltages across both ends of the resistors 12 and 13 are inputted to the control part 8 are serially connected to the resistors 12 and 13. After the switches 20 and 22 are turned off, voltage is applied to the switches 2 and 3 through resistors 21 and 23 to be able to detect the states of the switches. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling a predetermined control target for information given by turning on / off a contact switch.

[0002]

2. Description of the Related Art In various machines, when each part is operated in a predetermined sequence, it is detected that the operation of each part has been completed, an instruction to start or stop the operation of a movable part, or a reversal of the operation direction. A contact switch that is turned on or off when performing various detection operations or command operations is used in order to issue an instruction or to interlock the operation of each unit for safety of operation.
Typical switches of this type are pushbutton switches operated by a driver, limit switches that are driven to turn on or off when a movable part of a machine reaches a predetermined position, and the like. .

A control device for controlling a predetermined controlled object by using control information obtained from this type of contact switch has a DC power supply section for outputting a DC voltage to be applied to the contact switch, and this DC power supply section. From the state where the current is flowing through the contact switch and the state where the current is not flowing are respectively detected as the ON state and the OFF state of the contact switch, and a predetermined value is determined based on the information given by the state of the contact switch. And a control unit for controlling the controlled object.

FIG. 2 schematically shows a configuration example of a conventional control device 1'of this type. 2 and 3 in FIG.
Is a first and second contact switch, 4 is a battery that outputs a voltage VB (for example, 12 [V]), one end of the switch 3 and the negative terminal of the battery 4 are grounded, and the battery 4
The positive electrode terminal of is connected to one end of the contact switch 2.

A power supply terminal 6 and a ground pattern 7 are provided on the circuit board 5 of the controller 1 ', the power supply terminal 6 is connected to the positive terminal of the battery 4, and the ground pattern 7 is connected to the negative terminal of the battery 4. ing. The circuit board 5 also includes a controller 8 including a microcomputer, and a battery 4 applied between the power supply terminal 6 and the ground pattern 7.
Is attached to the control power supply circuit 9 for converting the power supply voltage Vcc (5 V) suitable for driving the microcomputer, and the output voltage of the power supply circuit 9 constitutes the power supply terminal of the microcomputer. Is being applied to.

The circuit board 5 also includes a diode 10 having an anode connected to the other end of the switch 2 of the battery 2.
Diode 1 whose cathode is connected to the other end of switch 3
1, a rated contact current conducting resistor 12 connected between the cathode of the diode 10 and the ground pattern 7, and a rated contact current conducting resistor connected between the anode of the diode 11 and the power supply terminal 6. 13 and an inverter 14 for inverting the voltage signal obtained at both ends of the resistor 12 and inputting it as an interrupt signal INT1 to the signal input port of the control unit 8.
And a buffer circuit 15 whose output terminal is connected to the signal input port of the control unit 8 are attached, and the voltage across the switch 3 passes through the diode 11 and the buffer circuit 15 to the signal input port of the control unit 8 and the interrupt signal INT2. Has been entered as.

In the illustrated controller, the diode 1
0 and the resistor 12 configure a switch state detection circuit 16 that detects the on / off state of the switch 2, and the diode 11 and the resistor 13 configure a switch state detection circuit 17 that detects the on / off state of the switch 3. ing.

In this control device, when the switch 2 is turned on, a current flows from the battery 4 through the switch 2, the diode 10 and the resistor 12, and a high level (H level) voltage signal is applied across the resistor 12. Occur. Here, when the switch 2 is in the ON state, the positive logic signal is obtained at both ends of the resistor 12. That is, the switch state detection circuit 16 that detects the state of the switch 2 is configured to input the signal generated by the switch 2 to the inverter 14 in the positive logic.

The inverter 14 inverts a 12 [V] system voltage signal provided from the resistor 12 side, converts it to a 5 [V] system voltage signal that can be input to the microcomputer, and inputs it to the control unit 8. To do.

When the switch 3 is turned on, a current flows from the control power supply circuit 9 through the resistor 13, the diode 11 and the switch 3, and the input voltage of the buffer circuit 15 changes from high level to low level (L level). descend. That is, the switch state detection circuit 17 that detects the state of the switch 3 outputs the signal generated by the switch 3 to the buffer circuit 15.
It is configured to input in negative logic.

The buffer circuit 15 converts the 12 [V] type voltage signal given through the resistor 13 into a 5 [V] type voltage signal which can be inputted to the microcomputer and inputs it to the control section 8.

It is assumed that the control device controls, for example, a controlled object (load) driven by a motor to move from a first position to a second position in accordance with a drive command,
It is assumed that the contact switches 2 and 3 are command switches that give drive commands and limit switches that are turned on when the controlled object reaches the second position.

In this case, when the switch 2 is turned on and a drive command is given, the inverter 14 controls the controller 8
The signal applied to the input terminal falls from the H level to the L level. The control unit 8 interrupts the fall of the signal supplied from the inverter 14 from the H level to the L level by the interrupt signal IN.
Recognizing as T1, interrupt processing is performed, and in this interrupt processing, a drive current is applied to the motor to move the controlled object toward the second position, and then the process returns to the main routine. When the controlled object reaches the second position and the switch 3 is turned on, the signal given to the control unit 8 through the buffer circuit 15 falls from the H level to the L level. The control unit 8 sends the falling edge of this signal to the interrupt signal INT.
It recognizes as 2 and performs interrupt processing, and in this interrupt processing, the supply of the drive current to the motor is stopped.

In the control device shown in FIG. 2, the voltage of the battery 4 is 12 [V] and the rated contact current energizing resistor 12 is used.
When the resistance value of each of the switches and 13 is R and the voltage drop generated in each of the diodes 10 and 11 is 0.5 [V], the contact current I [A] flowing through each contact of the switches 2 and 3 is It is given by the equation (1).

I = (12−0.5) / R (1) When the contact current I flows, the power P [W] consumed by each of the rated contact current energizing resistors 12 and 13 is as follows. Is given by

P = I ² × R (2) In the control device as shown in FIG.
Since the electric power given by the above formula (2) is consumed through the contact of 3, the heat generation in the resistors 12 and 13 increases,
There is a problem that the temperature of the control device rises.

Particularly in a control device for controlling a machine used in a severe working environment such as an agricultural machine, the oxide insulating film formed on the surface of the contact of the switch is burned and removed by Joule heat (self-cleaning). Therefore, the above-mentioned temperature rise becomes a problem.

Further, in a multifunctional and complicated machine such as an agricultural machine, dozens of contact switches for performing command operation and detection operation may be provided. In this way, a large number of command or detection switches are provided. In the case where the heat exchanger is provided, heat generation in the resistor for energizing the rated contact current becomes significant, and this heat generation may cause a failure of the control device.

Therefore, as shown in FIG. 3, it is necessary to insert a switch circuit composed of the transistor TR1 between the resistor 12 and the ground so that the control section 8 reads the state of the switch 2 (voltage across the resistor 12). Transistor T only while there is
A program executed by the microcomputer of the control unit 8 is configured so that R1 is turned on, and a switch circuit composed of the transistors TR2 and TR3 is inserted between the power supply terminal 6 and the anode of the diode 11 to perform control. A control device 1 "has been proposed in which a program executed by a microcomputer of the control unit 8 is configured so that the transistor TR2 is turned on only while the unit 8 needs to read the state of the switch 3.

With this configuration, the resistor 1 can be used when the operation timing of the switches 2 and 3 can be predicted.
Since it is possible to limit the time during which the current is passed through 2 and 13 to the short time required to read the states of the switches 2 and 3, the resistors 12, 1 can be used more than the control device shown in FIG.
Switch state detection circuit 1 by reducing the power consumption in 3
The heat generation at 6'and 17 'can be reduced.

[0021]

As described above, in the control device shown in FIG. 3, when the timings at which the switches 2 and 3 are operated are known in advance, the control section 8 appropriately controls the transistors TR1 and TR2. To control resistor 1
The effect of saving power consumption in 2 and 13 can be expected.

However, in many machines, such as agricultural machines, which are operated in various operation patterns by the driver's arbitrary operation, the operation timing of the switches 2 and 3 cannot be predicted, and therefore the transistor TR1 is used.
In many cases, it is not possible to shorten the period for holding TR2 and TR2 in the ON state, and it is often impossible to expect the effect of saving the power consumption of the resistors 12 and 13.

For example, the switch 2 is a switch that is turned on when a drive command to be controlled is given and is turned off when the drive is stopped. The timing at which the drive command is given and the drive stop command are given. If the timing to be applied is indefinite, the control unit 2 cannot recognize the drive command or the drive stop command given by the switch 2 unless the transistor TR1 is always kept in the ON state during operation. .

As described above, in the conventional control device, the effect of saving the power consumption of the resistor for converting the operating state of the command and detection switches into the voltage signal could not be expected so much, so that the controller can withstand a high temperature. It was necessary to use a resistor of this type, and it was unavoidable that the control device became bulky.
Further, in the conventional control device, since the control unit which is usually a microcomputer is exposed to the heat generated from the resistor, there is a possibility that the control unit may break down or malfunction.

An object of the present invention is to read the state of a switch into a control unit by supplying a rated contact current to the switch only for a short time even when the timing at which the contact switch performs an ON operation or an OFF operation cannot be predicted. Therefore, it is an object of the present invention to provide a control device capable of saving power consumption and suppressing temperature rise.

Another object of the present invention is to reduce the time required for the rated contact current to flow through the switch and suppress its temperature rise, thereby making it possible to miniaturize the device by using a resistor smaller than the conventional one. It is to provide a control device capable of performing the above.

[0027]

SUMMARY OF THE INVENTION The present invention is directed to a contact switch that is turned on and off to perform a detection operation or a command operation, and a direct current that outputs a direct current voltage to be applied to the contact switch. The state in which current flows from the power source section and the direct current power source section through the contact switch and the state in which the current does not flow are detected as the ON state and the OFF state of the contact switch, and are given according to the state of the contact switch. The control device is provided with a control unit that controls a predetermined control target based on the received information.

In the present invention, the resistance value is set such that the contact point switch is connected in series and the rated contact current flows from the DC power source through the contact point switch when the contact point switch is turned on. When the rated contact current energizing resistor and the reed switch that are turned on are turned on, it is detected that the rated contact current flows through the reed switch and the rated contact current energizing resistor. Sometimes, a contact current control switch provided so as to cut off the rated contact current, and a voltage signal obtained at both ends of a rated contact current energizing resistor or a voltage signal obtained at both ends of a contact switch are provided to the control unit. A signal input circuit to input,
It is connected in series to the contact switch and in parallel to the rated contact current energizing resistor, and is rated while the contact switch is in the ON state after the contact current control switch cuts off the rated contact current. A current limiting resistor having a resistance value set so that a contact current limited to a value smaller than the contact current flows through the contact switch.

In the above control device, when the contact switch is in the off state, the contact current control switch is in the off state, so that the power supply voltage is applied to both ends of the contact switch. When the contact switch is turned on, a contact current flows through the rated contact current carrying resistor and the contact switch. At this time, the voltage across the resistor for energizing the rated contact current rises to a high level, and the voltage across the contact switch goes to a low level. A change in the voltage across the rated contact current energizing resistor or a change in the voltage across the contact switch is input to the control unit through a signal input circuit. After the contact switch is turned on, the contact current control switch is turned off to cut off the rated contact current.At this time, the limited contact current flows to the contact switch through the current limiting resistor, Since the high level voltage across the current limiting resistor or the low voltage across the switch is input to the control unit through the signal input circuit, the state of the contact switch is continuously input to the control unit. When the contact switch is opened, the voltage across the current limiting resistor is in the low level state, and the voltage across the switch is in the high level state, so it is possible to confirm that the contact switch is in the off state. It can be input to the control unit. Further, even after the contact switch is opened, the voltage is applied to the contact switch through the current limiting resistor, so that the state of the contact switch can be continuously detected.

With the above construction, by appropriately setting the resistance value of the resistor for energizing the rated contact current, when the contact switch is in the off state, the oxidation insulation of the contact surface is provided at both ends of the switch. The voltage required to destroy the coating can be applied, and the contact current of the rated value required to thermally destroy the oxide insulation coating can be applied to the switch at the moment the contact switch is turned on. Therefore, the self-cleaning of the contact switch can be performed without any trouble.

Further, since the contact current flowing through the contact switch can be limited to a value smaller than the rated value after the contact switch is turned on, power consumption in the circuit for detecting the switch state can be reduced. The heat generation can be reduced.

The rated contact current energizing resistor for supplying a rated contact current (a sufficiently large current necessary for performing self-cleaning of the contact of the switch) to the reed switch is only energized for a short time. It is possible to downsize the control device by using a small-sized resistor having a smaller capacity than that used conventionally as a contact current conducting resistor.

Further, with the above-mentioned structure, since the heat generation in the circuit for detecting the switch state can be suppressed, it is possible to prevent the temperature of the control device from rising and to cause a failure, and the reliability is improved. Can be improved.

Further, with the above configuration, even if the contact switch operates at a timing that cannot be predicted by the control unit, the change in the state can be read into the control unit, so that the contact command generating the control command or the detection signal is generated. It can be applied regardless of how the switch is used.

In a preferred aspect of the present invention, the resistance value is set so that a rated contact current is caused to flow from the DC power source through the contact switch when the contact switch is connected in series and the contact switch is turned on. In addition to the set rated contact current energizing resistor, an inverter that inverts the level of the voltage obtained at both ends of the rated contact current energizing resistor and inputs the result to the control unit, and a contact switch from the DC power supply unit It is provided to turn on and off the current flowing through the rated contact current energizing resistor, and turns on when the contact switch is turned on while the output voltage of the inverter is at a high level. It turns off when the rated contact current flows through the contact switch and the rated contact current energizing resistor, and the output voltage of the inverter reverses to the low level state. A contact current control switch for interrupting the nominal contact current, series for contact switch, is connected in parallel with respect to the rated contact current energizing resistor,
After the contact current control switch cuts off the rated contact current, the contact current is limited to a value smaller than the rated contact current to keep the inverter input at a high level while the contact switch is in the ON state. A current limiting resistor having a resistance value set so as to flow through the switch is provided.

In such a configuration, no voltage is input to the inverter when the contact switch is in the off state, so the inverter inputs a high-level voltage signal to the control unit. Since the output voltage of the inverter is still at a high level at the moment the contact switch is turned on, the contact current control switch turns on when the switch turns on, and the contact switch and contact current control The rated contact current flows through the switch and the resistor for energizing the rated contact current. As a result, the voltage across the resistor for energizing the rated contact current becomes high level, so that the output voltage of the inverter becomes low level and the contact current control switch is turned off. As a result, the limited contact current flows through the contact switch through the current limiting resistor. While the contact switch is in the ON state, the high level voltage across the current limiting resistor is input to the inverter, so that the output voltage of the inverter is maintained in the low level state. Therefore, the control unit continues to recognize that the contact switch is in the ON state while the contact switch is in the ON state. Further, since the power supply voltage is continuously applied to the contact switch through the current limiting resistor even after the contact switch is turned off, the state of the contact switch can be continuously detected.

In another preferred aspect of the present invention, in addition to the rated contact current energizing resistor, a signal input for inputting a signal of a level corresponding to the level of a voltage signal obtained across the contact switch to the control section. It is provided to turn on / off the current that flows from the circuit and the DC power supply unit through the contact switch and the rated contact current carrying resistor, and the signal input from the signal input circuit to the control unit is in a high level state. The contact current that is maintained in the on state when the contact switch is in the on state and is turned off when the signal input from the signal input circuit to the control unit is in the low level state to cut off the rated contact current. It is connected in series to the control switch and the contact switch, and in parallel to the resistor for energizing the rated contact current, and the contact current control switch cuts off the rated contact current. After the contact switch has been turned on, the contact current limited to a value smaller than the rated current is maintained through the contact switch in order to keep the level of the signal input from the signal input circuit to the control unit at a low level. A current limiting resistor whose resistance value is set so as to flow is provided.

In still another preferred embodiment of the present invention,
It is provided between the rated contact current energizing resistor, one end of which is connected to the positive output terminal of the DC power source through a contact switch, and the other end of the rated contact current energizing resistor, and ground, and the control terminal has a high level. A contact current control switch that is turned on when the voltage signal of is applied and causes the rated contact current to flow to the contact switch through the rated contact current carrying resistor.
A series of inverters that invert the level of the voltage signal obtained at both ends of the rated contact current energizing resistor and apply it to the signal input port of the control unit and to the control terminal of the contact current control switch, and the contact switch Is connected in parallel to the resistor for energizing the rated contact current, and the contact switch is smaller than the rated contact current while the contact switch is in the ON state when the contact current control switch is in the OFF state. A current limiting resistor whose resistance value is set so as to flow a contact current is provided.

In this case, the inverter constitutes a signal input circuit for inputting the voltage signal obtained across the rated contact current carrying resistor to the control section.

In still another preferred embodiment of the present invention, one end of the rated contact current carrying resistor having one end grounded through a contact switch, the positive output terminal of the DC power supply unit and the other end of the rated contact current carrying resistor. A contact current control switch that is provided between the control terminal and the control terminal and that turns on when a high-level voltage signal is input and flows the rated contact current through the contact switch, and the positive-side output of the DC power supply unit. It is provided with one end connected to the terminal and the other end grounded through the contact switch, and the contact switch is rated while the contact current control switch is in the off state when the contact current control switch is in the off state. A current limiting resistor whose resistance value is set so that a contact current smaller than the contact current flows.
A buffer circuit is provided for supplying a voltage signal corresponding to the voltage across the contact switch to the signal input port of the controller and the control terminal of the contact current control switch.

In this case, the buffer circuit constitutes a signal input circuit for inputting a signal of a level corresponding to the level of the voltage signal obtained across the contact switch to the control section.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a control device 1 according to the present invention.
In the same figure, the same parts as those in FIG. 3 are designated by the same reference numerals as those in FIG.

In FIG. 1, 2 and 3 are contact switches,
Reference numeral 4 is a battery that constitutes a DC power supply unit, 5 is a circuit board, and 6
Reference numerals 7 and 7 denote power supply terminals and ground patterns provided on the substrate 5, 8 is a control unit including a microcomputer, 9 is a control power supply circuit, 10 and 11 are diodes, and power supply terminals 6 and ground patterns 7 are batteries. 4 is connected to the positive electrode side output terminal and the negative electrode side output terminal.

Reference numeral 12 is a resistor for energizing the rated contact current provided for the switch 2. One end of the resistor 12 is a direct current through a diode 10 having its cathode directed toward the resistor 12 and the contact switch 2. It is connected to the positive electrode side output terminal of the battery 4 that constitutes the power supply unit.

The other end of the resistor 12 is connected to the collector of an NPN transistor TR1 whose emitter is grounded. This transistor TR1 allows the contact current control switch 2 to be connected.
0 is configured. The contact current control switch 20 is
It is provided between the other end of the rated contact current energizing resistor 12 and the ground, and turns on when a high-level voltage signal is applied to its control terminal (transistor base). Resistor 12 and contact switch 2
A contact current flows through and. In this example, the resistance value of the rated contact current conducting resistor 12 is set so that the rated contact current flows through the contact switch 2 when the contact current control switch 20 is turned on. The rated contact current is set to be large enough to cause the contacts of the switch 2 to be self-cleaned.

Reference numeral 14 denotes an inverter whose output terminal is connected to the signal input port of the control section 8 and the base of the transistor TR1. In this inverter, the voltage signal obtained at both ends of the rated contact current carrying resistor 12 is It is input through the contact current control switch 20.

Reference numeral 21 is a current limiting resistor connected between the cathode of the diode 10 and the ground, and the voltage signal obtained across the resistor is input to the inverter 14. The current limiting resistor 21 is connected to the contact switch 2 in series,
It is connected in parallel to the resistor 12 for energizing the rated contact current, and when the contact current control switch 20 is in the off state, the contact current limited to a value smaller than the rated contact current is provided with the contact switch. 2, the resistance value is set to a value sufficiently larger than the resistance value of the rated contact current carrying resistor 12.

The inverter 14 inverts the voltage signal of 12 [V] system obtained at both ends of the resistor 12 and both ends of the resistor 21, respectively, and is of a 5 [V] system suitable for input to the microcomputer. It is converted into a voltage signal and input to the signal input port of the control unit 8.

Reference numeral 13 is a rated contact current energizing resistor provided for the switch 3, and one end of this resistor 13 is grounded through the contact switch 3. 22 is
A contact current control switch provided between the positive output terminal of the DC power supply unit and the other end of the rated contact current energizing resistor 13. This switch receives a high-level voltage signal at its control terminal. When it is turned on, it is turned on and the rated contact current is passed through the contact switch 3.

In the illustrated example, a PN whose emitter is connected to the power supply terminal 6 and whose collector is connected to the other end of the resistor 13
The contact current control switch 2 includes a P-transistor TR2 and an NPN transistor TR3 whose emitter is grounded and whose collector is connected to the base of the transistor TR2.
2, the rated contact current flows through the contact of the switch 3 when the switch 22 is turned on.

Reference numeral 23 is a current limiting resistor whose one end is connected to the positive output terminal of the battery (DC power supply) 4 and whose other end is grounded through the diode 11 and the contact switch 3. The resistance value of the resistor is sufficiently smaller than the resistance value of the resistor 13 so that a contact current sufficiently smaller than the rated contact current flows through the contact switch 3 when the contact current control switch 22 is in the off state. It is set to a large value.

Reference numeral 15 is a buffer circuit in which the voltage across the switch 3 is input through the diode 11. The output voltage of this buffer circuit is input to the signal input port of the control section 8 and also to the base of the transistor TR3. ing.

In the control device shown in FIG. 1, when the contact switch 2 is in the off state, the voltage signal is not input to the inverter 14, so that the output voltage of the inverter 14 is at the H level. Therefore, the transistor TR
A base current flows through 1, and the transistor is placed in a state in which it can be turned on as soon as a voltage is applied between its collector and emitter.

When the contact switch 2 is turned on, the output voltage of the battery 4 is applied between the collector and emitter of the transistor TR1 through the switch 2, the diode 10 and the resistor 12, so that the transistor TR1 is turned on. The rated contact current flows through the switch 2 through the rated contact current energizing resistor 12.

When the transistor TR1 is in the ON state, current flows from the battery 4 through the diode 10 and the current limiting resistor 21, but the resistance value of the rated current conducting resistor 12 is that of the current limiting resistor 21. Since it is set sufficiently smaller than the resistance value, the transistor TR
When 1 is in the ON state, there is no problem even if most of the contact current flows through the rated current conducting resistor 12.

At this time, since the voltage across the resistor 12 is input to the inverter 14, the output voltage of the inverter 14 changes from H level to L level. The control unit 8 detects the switch 2 from the level change of the output voltage of the inverter 14.
Detects that the is turned from the off state to the on state.

When the output voltage of the inverter 14 becomes L level, the base current stops flowing through the transistor TR1 and the transistor is turned off. Therefore, the rated contact current flowing through the switch 2 is cut off. After the transistor TR1 is turned off, a contact current limited to a value sufficiently smaller than the rated contact current flows from the battery 4 through the switch 2, the diode 10 and the current limiting resistor 21. At this time, since the voltage signal obtained across the resistor 21 is input to the inverter 14, the output voltage of the inverter 14 is maintained at the L level while the switch 2 is in the ON state.

The control unit 8 shown in the figure recognizes the fall of the signal supplied from the inverter 14 from the H level to the L level as an interrupt signal INT1 and performs interrupt processing. In this interrupt processing, a predetermined operation is performed on the controlled object. Perform processing for causing

In the control device shown in FIG. 1, when the switch 3 is in the off state, the voltage of the battery 4 is input to the buffer circuit 15 through the current limiting resistor 23, so that the output voltage of the buffer circuit is increased. Is at the H level. The control unit 8 recognizes that the switch 3 is in the off state from the output state of the buffer circuit.
Further, since the output of the buffer circuit 15 is in the H level state, the transistor TR3 is in the ON state and the base current flows through the transistor TR2, but the switch 3 is in the OFF state, so that the transistor TR2 is held in the OFF state. . Thus, when the switch 3 is off,
Since the contact current control switch 22 is held in the OFF state, no voltage is applied to the rated contact current energizing resistor 13.

When the switch 3 is turned on, a base current flows through the transistor TR2 and the transistor TR2 is turned on.
Resistor 1 for energizing the rated contact current because 2 is turned on.
A rated contact current flows through the switch 3 through the diode 3 and the diode 11. As a result, the switch 3 is self-cleaned.

When the switch 3 is turned on, the output voltage of the buffer circuit 15 changes from H level to L level. The control unit 8 recognizes that the switch 3 is turned on when detecting a change in the output voltage of the buffer circuit.

The control unit 8 shown in the figure recognizes the fall of the voltage signal supplied from the buffer circuit 15 from the H level to the L level as an interrupt signal INT2 and performs an interrupt process. In this interrupt process, a control target is predetermined. Performs processing to perform the operation.

When the output voltage of the buffer circuit 15 becomes L level, the base current stops flowing through the transistor TR3 and the transistor TR3 is turned off. Therefore, the transistor TR2 is also turned off and the contact current control switch 22 is turned on. Turns off. Therefore, the rated contact current flowing through the rated contact current carrying resistor 13 is cut off, and the limited contact current flows from the battery 4 through the current limiting resistor 23. Since the contact current flows from the battery 4 through the current limiting resistor 23 while the switch 3 is in the ON state, the voltage across the switch 3 is fixed to a constant value (sufficiently low value). The control unit 8 recognizes that the switch 3 is in the ON state by reading this voltage.

With the above construction, by setting the resistance values of the rated contact current energizing resistors 12 and 13 appropriately, when the contact switches 2 and 3 are in the off state,
A voltage necessary to destroy the oxide insulation film on the contact surface is applied to both ends of the switch, and the rating required to thermally destroy the oxide insulation film at the moment when the contact switch is turned on. Since the contact current can flow, the self-cleaning of the contact switches 2 and 3 can be performed without any trouble.

Further, after the contact switches 2 and 3 are turned on, the contact current flowing through each of them can be limited to a value smaller than the rated value, so that the circuit for detecting the switch state consumes less power. As a result, heat generation can be reduced.

The rated contact current energizing resistors 12 and 13 for supplying a rated contact current (a sufficiently large current necessary for self-cleaning the contact of the switch) to the contact switches 2 and 3 are energized for a short time. Therefore, it is possible to miniaturize the control device by using a small-sized one having a smaller capacity than those conventionally used as these rated contact current energizing resistors.

Further, with the above-mentioned configuration, the resistors 12 and 1 constituting the circuit for detecting the states of the switches 2 and 3 are formed.
Since it is possible to suppress heat generation in 3, 21, and 23, it is possible to prevent the temperature of the control device from rising and cause a failure, and it is possible to improve reliability.

Further, with the above-mentioned configuration, the states of the switches 2 and 3 can be constantly monitored, and therefore, even when the contact switch operates at a timing that the control unit 8 cannot predict, the change in the state of the contact switch is transmitted to the control unit. Can be read. Therefore, no matter how the contact switch that generates the control command or the detection signal is used, the state of the switch can be detected without consuming a large amount of power.

In the above-mentioned embodiment, the contact switch has two switches.
However, the present invention can be applied to the case where only one contact switch is provided or the case where three or more contact switches are provided.

[0070]

According to the present invention, the following effects can be obtained.

(1) In order to destroy the oxide insulation film on the contact surface at both ends of the contact switch when the contact switch is in the off state by appropriately setting the resistance value of the rated contact current carrying resistor. Since the required contact voltage can be applied and the rated contact current required for thermal destruction of the oxide insulation film can be applied at the moment when the contact switch is turned on, it hinders self-cleaning of the contact switch. Can be done without.

(2) The rated contact current flows through the contact switch only for an extremely short time immediately after the contact switch is turned on, and the contact current is rated after the contact switch is turned on. Since the value can be limited to a value smaller than the value, it is possible to reduce power consumption and heat generation in the circuit that detects the switch state.

(3) Since the rated contact current energizing resistor for supplying the rated contact current to the contact switch is energized only for a short time, it has a small capacity and is smaller than that used conventionally. The size of the control device can be reduced by using the one described above.

(4) Since it is possible to suppress the heat generation of the resistor forming the circuit for detecting the state of the contact switch, it is possible to prevent the temperature of the control device from rising and causing a failure. The reliability can be improved.

(5) Since the state of the contact switch can be constantly monitored, even if the contact switch operates at a timing that cannot be predicted by the control unit, the change in the state can be read into the control unit. Therefore, no matter how the contact switch that generates the control command or the detection signal is used, the state of the switch can be detected without consuming a large amount of power.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a conventional control device.

FIG. 3 is a circuit diagram showing another configuration example of a conventional control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control device, 2, 3 ... Contact switch, 4 ... Battery, 5 ... Circuit board, 8 ... Control part, 12, 13 ... Rated contact current energizing resistor, 20, 22 ... Contact current control switch, 21 , 23 ... Current limiting resistors, TR1 to TR3 ...
Transistor.

Claims (5)

[Claims] 1. A contact switch that is turned on and off to perform a detection operation or a command operation, a DC power supply unit that outputs a DC voltage to be applied to the contact switch, and the DC power supply. A state in which a current is flowing from a part through the contact switch and a state in which the current is not flowing are respectively detected as an on state and an off state of the contact switch, and based on information given by the state of the contact switch. A control unit for controlling a predetermined controlled object by means of a controller connected in series to the contact switch and being turned on by the DC power supply unit when the contact switch is turned on. A rated contact current energizing resistor whose resistance value is set so that the rated contact current flows through the contact switch, and when the contact switch is turned on. And a contact current control switch provided to cut off the rated contact current when it is detected that the rated contact current flows through the contact switch and the rated contact current energizing resistor. A signal input circuit for inputting a voltage signal obtained at both ends of the rated contact current energizing resistor or a voltage signal obtained at both ends of the contact switch to the control unit, and in series for the contact switch, It is connected in parallel to the rated contact current energizing resistor, and when the contact switch is turned on after the contact current control switch cuts off the rated contact current And a current limiting resistor whose resistance value is set so that a contact current limited to a small value flows through the contact switch. 2. A contact switch that is turned on and off to perform a detection operation or a command operation, a DC power supply unit that outputs a DC voltage to be applied to the contact switch, and the DC power supply. The state in which a current is flowing from the part through the contact switch and the state in which the contact current is not flowing are detected as the ON state and the OFF state of the contact switch, respectively, and the information given by the state of the contact switch is detected. In a control device including a control unit that controls a predetermined control target based on the above, the DC power supply unit connects the contact switch to the contact switch in series and turns on the contact switch when the contact switch is turned on. A resistor for energizing the rated contact current whose resistance value is set so that the rated contact current flows through the contact switch, and a resistor for detecting the switch state An inverter that inverts the level of the voltage to be input to the control unit, and is provided so as to turn on and off the current flowing from the DC power supply unit through the contact switch and the switch state detection resistor, and When the contact switch is turned on while the output voltage is at a high level, the contact switch is turned on, and the rated contact current flows through the contact switch and the switch state detection resistor to cause the inverter A contact current control switch that is turned off when the output voltage reverses to a low level state and shuts off the rated contact current, in series with the contact switch, and in the switch state detection resistor. In parallel, the contact current control switch is turned on after the contact current control switch cuts off the rated contact current. A current limiting resistor whose resistance value is set so that a contact current limited to a value smaller than the rated contact current flows through the reed switch to keep the input of the inverter at a high level during A control device comprising: 3. A contact switch that is turned on and off to perform a detection operation or a command operation, a DC power supply unit that outputs a DC voltage to be applied to the contact switch, and the DC power supply. The state in which a current is flowing from the part through the contact switch and the state in which the contact current is not flowing are detected as the ON state and the OFF state of the contact switch, respectively, and the information given by the state of the contact switch is detected. In a control device including a control unit for controlling a predetermined controlled object based on the above, the DC switch is connected in series to the contact switch, and when the contact switch is turned on, the DC power supply unit A resistor for energizing the rated contact current whose resistance value is set so that the rated contact current flows through the contact switch, and the voltage obtained across the contact switch. Signal input circuit for inputting a signal of a level corresponding to the signal level to the control section, and is provided so as to turn on / off the current flowing from the DC power supply section through the reed switch and the rated contact current energizing resistor. A signal input from the signal input circuit to the control unit is in a high level state and is held in the ON state when the contact switch is in the ON state, and is input from the signal input circuit to the control unit. A contact current control switch that is turned off when the signal is in a low level state to cut off the rated contact current, and in series with the contact switch, to the rated contact current energizing resistor. Is connected in parallel to the signal input circuit while the contact current control switch is in the ON state after the contact current control switch cuts off the rated contact current. In order to keep the level of the signal input to the control unit at a low level, the current limiter whose resistance value is set so that the contact current limited to a value smaller than the rated current flows through the contact switch A control device comprising a resistor. 4. A contact switch that is turned on and off to perform a detection operation or a command operation, and a DC voltage that is provided with the negative electrode grounded and is applied to the contact switch. The output DC power supply unit, the state in which a current is flowing from the DC power supply unit through the contact switch and the state in which the current is not flowing are detected as the ON state and the OFF state of the contact switch, respectively, and In a control device comprising a control unit for controlling a predetermined control target based on information given by the state of a contact switch, a rated contact whose one end is connected to the positive output terminal of the DC power supply unit through the contact switch It is provided between the current-carrying resistor and the other end of the rated contact current-carrying resistor and ground, and turns on when a high-level voltage signal is applied to the control terminal. And a contact current control switch that causes a rated contact current to flow through the contact switch through the rated contact current energizing resistor, and the level of the voltage signal obtained across the rated contact current energizing resistor is reversed. An inverter applied to the signal input port of the control unit and applied to the control terminal of the contact current control switch, connected in series to the contact switch and in parallel to the rated contact current energizing resistor. And the resistance value is set so that a contact current smaller than the rated contact current flows through the contact switch while the contact current control switch is in the OFF state while the contact switch is in the ON state. A control device comprising a current limiting resistor. 5. A contact switch that is turned on and off to perform a detection operation or a command operation, and a DC voltage that is provided with the negative electrode grounded and is applied to the contact switch. The output DC power supply unit, the state in which a current is flowing from the DC power supply unit through the contact switch and the state in which the current is not flowing are detected as the ON state and the OFF state of the contact switch, respectively, and In a control device comprising a control unit for controlling a predetermined controlled object based on information given by the state of a contact switch, a rated contact current conducting resistor having one end grounded through the contact switch, and the DC power supply. Is provided between the positive side output terminal of the part and the other end of the rated contact current carrying resistor, and is turned on when a high-level voltage signal is input to the control terminal. And a contact current control switch for flowing a rated contact current through the contact switch, and one end of which is connected to the positive output terminal of the DC power supply unit and the other end of which is grounded through the contact switch. A resistance value is set so that a contact current smaller than the rated contact current flows through the contact switch while the contact current control switch is in the OFF state while the contact switch is in the ON state. A current limiting resistor, and a buffer circuit for applying a voltage signal corresponding to the voltage across the contact switch to the signal input port of the controller and the control terminal of the contact current control switch. Control device.