JPH1032995A - Drive unit for dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drive unit for a DC motor, which can prevent an arc from being generated at the contact of a relay which changes over the polarity of an armature current. SOLUTION: A transistor TR1 is connected across a DC power supply 1 and a changeover switching circuit 4 which changes over the polarity of an armature current for a motor M. A switch control circuit 7 which controls the transistor TR1 is installed in such a way that, when a forward instruction switch 3A or a reversing instruction switch 3B is closed, a state that the transistor TR1 is turned on is delayed until a moving contact c1 or c2 at a relay in the changeover switching circuit 4 comes into contact with a fixed contact a1 or a2 so as to be stabilized and that, when the forward instruction switch 3A and the reversing instruction switch 3B are opened, the transistor TR1 is set in an off-state before the moving contact c1 or c2 at the relay is separated from the fixed contact a1 or a2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor driving device for controlling supply of an armature current to a DC motor in accordance with a forward rotation command and a reverse rotation command.

[0002]

2. Description of the Related Art When a DC motor is driven, it is necessary to switch the polarity of an armature current when switching its rotation direction. For switching the polarity of the armature current, a changeover switch circuit combining relay contacts is used.

If it is necessary to adjust the rotation speed of the DC motor, it is necessary to adjust the magnitude of the armature current. As a method of adjusting the armature current, a semiconductor switch element is inserted into a current supply circuit of the armature current, and the semiconductor switch element is turned on and off at a predetermined duty ratio to control the armature current by PWM (pulse width modulation control). )
Then, a method of adjusting the average value is widely adopted.

Therefore, in a DC motor driving device for switching the rotation direction and adjusting the rotation speed, a semiconductor switch element for PWM control and a changeover switch are provided between a DC power supply and an armature of the DC motor. A series circuit with the contact of the relay is inserted, and the armature current is supplied to the DC motor through the semiconductor switch element and the contact of the relay.

FIG. 3 shows a configuration example of a conventional DC motor driving device of this type. In the figure, 1 is a DC power supply, 2 is an armature of a DC motor M, 3 is an operation command circuit,
Reference numeral 4 denotes a changeover switch circuit including relay contacts, 5 denotes an armature current control switch circuit, and 6 denotes a PWM control circuit.

In the drive device shown in FIG. 3, the operation command circuit 3 includes a forward rotation command switch 3A and a reverse rotation command switch 3B. When the forward rotation command switch 3A and the reverse rotation command switch 3B are closed, respectively, A rotation command signal and a reverse rotation command signal are generated, and a stop command signal is generated by opening both command switches.

The changeover switch circuit 4 includes an exciting coil RY1
A contact 4A of a first relay driven by an excitation coil RY2, a contact 4B of a second relay driven by an exciting coil RY2,
It consists of arc-extinguishing diodes D2 and D3, and switches the polarity of the current supplied to the armature 2 by switching the contacts 4A and 4B. The contact 4A of the first relay is the first
Input-side fixed contact a1 and first output-side fixed contact b1
When the exciting coil RY1 is deenergized, it contacts the first output-side fixed contact b1 as shown in FIG.
A first movable contact c1 that contacts the input-side fixed contact a1 when Y1 is excited.
1 is connected to one end of the armature 2. The contact 4B of the second relay is connected to the second fixed contact a2 on the input side, the second fixed contact b2 on the output side, and the second fixed output side when the exciting coil RY2 is deenergized, as shown in the figure. A second movable contact c2 that contacts the contact b2 and contacts the input-side fixed contact a2 when the exciting coil RY2 is excited, and the second movable contact c2 is connected to the other end of the armature 2. Have been.

An armature current control switch circuit 5 is provided for turning on and off an armature current flowing through the changeover switch circuit 4, and turns on and off a transistor TR1 as a semiconductor switch element and a base current of the transistor TR1. A control transistor TR2 and resistors R1 to R4 are provided. In this switch circuit 5, when the transistor TR2 is turned on, a base current flows through the transistor TR1 to turn on the transistor TR1.

The PWM control circuit 6 has a transistor TR4 that is turned on and off in response to a PWM control signal Vp having a pulse waveform that changes at a predetermined duty ratio. When the transistor TR4 is turned on and off, When the state becomes the transistor TR2
Are turned off and on.

In the driving device shown in FIG. 3, when the motor is rotated forward, the transistor TR4 of the PWM control circuit 6
And the transistor TR4 is turned on at the same time as the power switch SW is closed,
The transistor TR1 is prevented from turning on. In this state, the power switch SW is closed and the forward rotation command switch 3A is closed. When the power switch SW and the forward command switch are closed, an exciting current flows from the DC power supply 1 to the exciting coil RY1 of the first relay through the diode D1 and the forward command switch 3A. This allows
The movable contact c1 of the first relay contacts the fixed contact a1. In this state, the transistor TR4 of the PWM control circuit 6
Is turned off, the DC power supply 1 outputs the resistors R2 and R4.
Base current is supplied to the transistor TR2 through
The transistor TR2 is turned on. As a result, the transistor TR1 is turned on, so that the DC power supply 1 supplies the transistor TR1—the fixed contact a1—the movable contact c1—
The armature current flows through the path of the armature 2-movable contact c2-fixed contact b2-DC power supply 1, and the motor rotates forward. In this state, when the transistor TR4 of the PWM control circuit 6 is turned on and off, the transistor TR2 is turned on and off, and the transistor TR1 is turned on and off as the transistor TR2 is turned on and off, so that the armature current is turned on and off at a predetermined duty ratio. (PWM control).

When stopping the motor, first, the transistor TR4 of the PWM control circuit is kept on, thereby turning off the transistor TR1 to cut off the armature current. Thereafter, the forward rotation command switch 3A is opened, the exciting coil RY1 is deenergized, and the movable contact c1 is changed to the fixed contact a1.
Disconnect from

To reverse the motor, the reverse rotation command switch 3B is closed, the movable contact c2 of the relay is brought into contact with the fixed contact a2, the transistor TR1 is turned on, and the DC power source 1-transistor TR1- An armature current flows through the path of the fixed contact a2, the movable contact c2, the armature 2, the movable contact c1, the fixed contact b1, and the DC power supply 1. When stopping the motor that is rotating in reverse, the transistor TR4 of the PWM control circuit is turned on and the transistor TR1 is turned on.
Is turned off, the reverse rotation command switch 3B is opened,
The excitation coil RY2 is deenergized, and the movable contact c2 is changed to the fixed contact a.
Disconnect from 2.

[0013]

In the DC motor driving device shown in FIG. 3, when the movable contact c1 of the first relay contacts the fixed contact a1, the movable contact is caused by mechanical vibration of the movable system of the relay. c1 contacts the fixed contact a1,
Bouncing (bounci) away from the fixed contact a1
ng) The phenomenon occurs. When the bouncing phenomenon occurs, an arc is generated between the movable contact c1 and the fixed contact a1, and the contact is consumed. Similarly, a bouncing phenomenon also occurs when the movable contact c2 of the second relay contacts the fixed contact a2, so that an arc is generated between the movable contact c2 and the fixed contact a2, and the contact is consumed.

When switching the direction of rotation of the motor,
While the transistor TR4 of the PWM control circuit 6 is conducting, the forward command switch 3A or the reverse command switch 3
If B is opened, there is no problem, but if the forward command switch or the reverse command switch is opened by mistake when the transistor TR4 of the PWM control circuit is in the off state, the movable contact c1 of the first relay will change to the fixed contact a1. When the movable contact c2 of the second relay is separated from the fixed contact a2, or when the movable contact c2 of the second relay is separated from the fixed contact a2, an arc is generated between the movable contact c1 and the fixed contact a2.

In the apparatus shown in FIG. 3, the diodes D2 and D3 for extinguishing the arc are connected in order to suppress the occurrence of an arc at the contact point of the relay as described above. Then, it was not possible to completely prevent the arc from being generated at the contact point of the relay.

As described above, in the conventional driving device, an arc is generated between the movable contact and the fixed contact due to the bouncing phenomenon that occurs when the movable contact of the relay contacts the fixed contact, and the motor is stopped. If the forward or reverse command switch is operated incorrectly when switching the direction of rotation of the motor, the arc will be generated at the contacts of the relay. There was a problem that it became shorter.

An object of the present invention is to provide a DC motor driving device capable of preventing an arc from being generated between a movable contact and a fixed contact of a relay for switching the polarity of an armature current of a DC motor. It is in.

[0018]

SUMMARY OF THE INVENTION The present invention relates to a forward rotation command signal and a reverse rotation command signal for instructing the DC motor to rotate forward and backward, and a stop instruction signal for instructing the DC motor to stop. And a relay contact which is energized when a forward command signal is generated and when a reverse command signal is generated, and is deenergized when a stop command signal is generated. A switch circuit for switching the polarity of the armature current supplied to the DC motor in response to the signal and the reverse command signal, and a serial connection to the switch circuit for on / off control of the armature current flowing through the switch circuit And a switch circuit for controlling an armature current having a semiconductor switching element according to the present invention.

In the present invention, the semiconductor switch element is turned on when the first delay time has elapsed since the generation time of the forward rotation command signal and when the first delay time has elapsed since the generation time of the reverse rotation instruction signal. And a switch control circuit for turning off the semiconductor switch element when a second delay time has elapsed from the generation time of the stop command signal.

The first delay time is set to be longer than an excitation operation stabilization time required for a contact of the relay to perform a switching operation and settle into a stable state after the relay is excited. In addition, the second delay time is set shorter than the deactivation operation time required after the relay is deactivated to perform the switching operation of the contact of the relay.

The above-mentioned operation stabilization time at the time of excitation is an "initial operation time" which is a time required for the movable contact to come into contact with a predetermined fixed contact after the relay is excited, and an initial operation time after the movable contact comes into contact with the fixed contact. And the "bounce time", which is the time required for the movable contact to stably come into contact with the fixed contact after the bouncing phenomenon of the movable contact is eliminated.

Note that the bouncing phenomenon is a phenomenon in which the movable contact repeatedly contacts and separates from the fixed contact due to mechanical vibration of the movable system of the relay.

With the above configuration, when the forward rotation command signal or the reverse rotation command signal is generated, the semiconductor switch element is held in the off state until the contact of the relay is stabilized, and the contact of the relay is stabilized. Later, the semiconductor switch element is turned on. Therefore, when the bouncing phenomenon occurs in the relay, the armature current does not flow through the contacts of the relay, so that no arc is generated at the contacts of the relay.

When a stop command signal is generated, the contact of the relay performs a switching operation after the semiconductor switch element is turned off, so that the armature current is always cut off by the semiconductor switch element and the arc of the relay contact is generated. Is prevented from occurring.

In the DC motor driving apparatus to which the present invention is applied, in order to adjust the armature current, a PW for turning on and off the semiconductor switch element in response to a PWM control signal.
When the M control circuit is provided, the permission signal is generated when the first delay time has elapsed since the generation time of the forward rotation command signal and when the first delay time has elapsed since the generation time of the reverse rotation instruction signal. A permission signal prohibition signal generation circuit for generating a prohibition signal when a second delay time has elapsed from the generation time of the stop command signal; and a PW signal when the permission signal is generated.
The M control circuit permits the semiconductor switch element to be turned on, and when a prohibition signal is generated, the PWM control circuit prohibits the semiconductor switch element from being turned on and turns the semiconductor switch element off. The switch control circuit can be configured by the on / off control circuit held.

In the drive device to which the present invention is directed, the operation command circuit includes, for example, a normal rotation command signal for instructing the DC motor to rotate forward and a stop command for instructing the DC motor to stop rotating forward. A forward rotation command switch for generating a signal, a reverse rotation command switch for generating a reverse rotation command signal for instructing the DC motor to rotate in reverse, and a stop instruction signal for instructing to stop the reverse rotation of the DC motor. be able to.

In this case, the first and second excitation signals are respectively excited when the forward rotation command signal and the reverse rotation command signal are generated.
And a changeover switch circuit can be configured by the contacts of both relays.

In this case, as the first relay, for example,
A first excitation coil which is set to an excited state and a non-excited state when the forward rotation command switch generates a forward rotation command signal and a stop command signal, a first input-side fixed contact, and a DC power supply A first output-side fixed contact connected to a circuit connected to the negative terminal of the DC motor, and a first excitation coil connected to one end of an armature of the DC motor when the first excitation coil is excited and when the first excitation coil is de-energized. Each having a first movable contact contacting the first input-side fixed contact and the first output-side fixed contact can be used.

The second relay includes a second exciting coil which is turned on and off when the reverse command switch generates a reverse command signal and a stop command signal, respectively. A second input-side fixed contact connected to the input-side fixed contact, a second output-side fixed contact connected to a circuit connected to the negative terminal of the DC power supply, and a second end connected to the armature of the DC motor. And a second movable contact that contacts the second input-side fixed contact and the second output-side fixed contact when the second excitation coil is excited and when the second excitation coil is de-energized, respectively. Can be used.

In this case, the permission signal inhibition signal generation circuit
For example, a charging circuit for charging an integrating capacitor with a first time constant when a forward rotation instruction switch generates a forward rotation instruction signal and when a reverse rotation instruction switch generates a reverse rotation instruction signal, and a forward rotation instruction switch and a reverse rotation instruction switch. And a discharge circuit for discharging the integration capacitor with the second time constant when both stop command signals are being generated, and comparing the voltage across the integration capacitor with a reference voltage to compare the voltage across the integration capacitor. A comparator generates a permission signal when the voltage exceeds the reference voltage, and generates a prohibition signal when the voltage across the integration capacitor is lower than the reference voltage.

When the first and second relays described above are used, the time required from the generation of the forward rotation command signal or the reverse rotation command signal until the integrated voltage exceeds the reference voltage is reduced by the first time. After the excitation coil is excited, the first movable contact comes into contact with the first input-side fixed contact, and the operation stabilization time required for excitation to settle into a stable state, and after the second excitation coil is excited The first time constant is set so as to be longer than any of the excitation operation stabilization times required for the second movable contact to contact the second input-side fixed contact and settle into a stable state.

Further, the time required for the integrated voltage to become equal to or less than the reference voltage after the forward command switch and the reverse command switch generate the stop command signal is determined by the first time after the forward command switch generates the stop command signal. The deactivation time required for the movable contact to separate from the first input-side fixed contact, and until the second movable contact separates from the second input-side fixed contact after the reverse command switch generates a stop command signal. The second time constant is set so as to be shorter than any of the deenergizing operation times required for.

[0033]

1 shows an example of the configuration of a DC motor driving apparatus according to the present invention. In FIG. 1, 1 is an armature of a DC motor M, 2 is a DC power supply for outputting a power supply voltage VB, 3 is an operation command circuit, 4 is a changeover switch circuit, 5 is an armature current control switch circuit, 6 is a PWM control circuit,
Reference numeral 7 denotes a switch control circuit, and reference numeral 8 denotes a control power supply circuit to which the output of the DC power supply 1 is input through a power switch SW. The control power supply circuit 8 has a non-ground side output terminal and a ground side output terminal, and outputs a constant control DC voltage E between both output terminals.

The illustrated DC power supply 1 is composed of a battery whose negative terminal is grounded. The positive terminal of the DC power supply 1 is connected to the emitter of a PNP transistor TR1 as a semiconductor switching element through a power switch SW. I have. The emitter of the transistor TR1 is also connected to the anode of a diode D1, and the cathode of the diode D1 is connected to one end of resistors R1 and R2. Resistance R
The other end of 1 is connected to the base of the transistor TR1 through the resistor R3 and to the collector of the NPN transistor TR2 whose emitter is grounded. The other end of the resistor R2 is connected to the base of the transistor TR2 through the resistor R4. In this example, the transistor T
A switch driving circuit for turning on / off the transistor TR1 (semiconductor switch) according to an on / off control signal described later is constituted by R2, the resistors R1 to R4, and the diode D1, and the armature current control is performed by the driving circuit and the transistor TR1. The switch circuit 5 is configured.

The operation command circuit 3 includes a normal rotation command switch 3A.
And a reverse rotation command switch 3B, and one ends of the switches 3A and 3B are grounded. In this example, when the forward rotation instruction switch 3A is turned on, a forward rotation instruction signal is generated, and when the forward rotation instruction switch 3A is turned off, a stop instruction signal is generated. When the reverse command switch 3B is turned on, a reverse command signal is generated, and when the reverse command switch 3B is turned off, a stop command signal is generated.

In the illustrated example, the changeover switch circuit 4 is constituted by the contacts 4A and 4B of the two relays and the arc-extinguishing diodes D2 and D3. The first relay is the first
And a contact 4A driven by the exciting coil RY1.
One end of Y1 is connected to the other end (non-ground side terminal) of the forward rotation command switch 3A. The second relay comprises a second exciting coil RY2 and a contact 4B driven by the exciting coil RY2.
Is connected to the other end of the reverse rotation command switch 3B.

The first and second excitation coils RY1 and RY
2 are connected in common, and a common connection point of the other ends of both exciting coils is connected to a circuit connected to the cathode of the diode D1 of the armature current control switch circuit 5. Flywheel diodes D4 and D5 are provided at both ends of the first exciting coil RY1 and the second exciting coil RY2, respectively.
Are connected with their anodes facing the command switches 3A and 3B. These diodes D
4 and D5 protect the command switches by absorbing the high voltages induced in the respective exciting coils when the forward command switch 3A and the reverse command switch 3B are opened,
When the forward command switch and the reverse command switch are opened, the exciting coils RY1 and RY2 are kept in the excited state for a short time to delay the return of the contacts of the respective relays.

The contact 4A of the first relay is connected to the first input-side fixed contact a1, the first output-side fixed contact c1, and the first excitation coil RY1 when the first excitation coil RY1 is turned on and off. And a first movable contact c1 that contacts the first input-side fixed contact a1 and the first output-side fixed contact b1, respectively. The first output-side fixed contact b1 is connected to a DC power source 1 through a ground circuit. Is connected to the negative electrode terminal of.

The contact 4B of the second relay is connected when the second input-side fixed contact a2, the second output-side fixed contact c2, and the second exciting coil RY2 are in the excited state and in the non-excited state. And the second movable contact c2 which contacts the second input fixed contact a2 and the second output fixed contact b2, respectively. The second output fixed contact b2 is a first relay. And the output side fixed contact b1 is connected to the negative terminal of the DC power supply 1.

The first fixed contact a1 on the input side and the second fixed contact a2 on the input side are connected in common, and the common connection point of the fixed contacts a1 and a2 is connected to the collector of a transistor TR1 as a semiconductor switch element. ing. One end and the other end of the armature 2 of the DC motor are connected to the first movable contact c1 and the second movable contact c2, respectively.

The arc-extinguishing diodes D2 and D3 are connected between one end of the armature 2 and the ground and between the other end and the ground with their respective anodes facing the ground.

The switch control circuit 7 includes a permission signal prohibition signal generation circuit 7A and an on / off control circuit 7B.

The permission signal prohibiting signal generating circuit 7A includes an integrating circuit 701, a reference voltage generating circuit 702 for generating a reference voltage Vr, and a comparator 703 for comparing the integrated voltage Vi obtained from the integrating circuit with the reference voltage Vr. Consists of

The integrating circuit 701 includes an integrating capacitor C1
A resistor R5 for setting a charging time constant, a resistor R6 for setting a charging / discharging time constant, a resistor R7 for setting a discharging time constant, and a diode D6 for preventing the charging current of the integrating capacitor C1 from flowing through the resistor R7. To generate an integrated voltage Vi across the integrating capacitor C1.

More specifically, the integrating capacitor C
1 is grounded, and the other end (non-ground side terminal) of the integrating capacitor is connected to the control power supply circuit 8 through resistors R5 and R6.
Is connected to the positive output terminal on the positive side. Integration capacitor C
The other end of 1 is also connected to one end of a discharge time constant setting resistor R7, and the other end of the resistor R7 is connected to the anode of a diode D6. The cathode of the diode D6 is a resistor R
It is connected to the connection point between 5 and R6.

The cathode of the diode D6 is also connected to the collector of an NPN transistor TR3 whose emitter is grounded, and the base of the transistor TR3 is connected to the cathode of the diode D7 through a resistor R8. The anode of the diode D7 is connected to the positive output terminal of the control power supply circuit 8 through a resistor R9, and a base current is supplied from the control power supply circuit 8 to the transistor TR3 through the resistor R9, the diode D7 and the resistor R8. The anode of the diode D7 is also connected to the diode D8.
The anodes of the diodes D8 and D9 are connected to the non-ground side terminals of the forward command switch 3A and the reverse command switch 3B, respectively.

In the example shown, a discharging switch for discharging the integrating capacitor is constituted by the transistor TR3, and the forward command switch 3A or the reverse command switch 3B is constituted by the resistors R8 and R9 and the diodes D7 to D9.
Is turned off (when either the forward command signal or the reverse command signal is generated), the discharge switch is turned off, and both the forward command switch 3A and the reverse command switch 3B are opened. A discharge switch control circuit that turns on the discharge switch when the switch is ON (when a stop command signal is generated).

Transistor T constituting discharge switch
R3 is a resistor R9 and a diode D7 from the control power supply circuit 8.
A base current is applied through the resistor R8 and the resistor R8 to be turned on. Forward command switch 3A and reverse command switch 3
B is closed (either the forward rotation command signal or the reverse rotation command signal is generated), the transistor TR3
Is bypassed from the transistor TR3 through the diode D8 or D9 and the command switch 3A or 3B, so that the transistor TR3 is turned off.

When the transistor TR3 is off, the integration capacitor C1 is charged with the first time constant from the control power supply circuit 8 through the resistors R5 and R6. The first time constant is determined by the capacitance of the integrating capacitor C1 and the resistance R
5 and the resistance of R6.

When the transistor TR3 is in the ON state, the electric charge of the integrating capacitor C1 is passed through the series circuit of the resistor R7 and the diode D6 and the parallel circuit of the resistor R6, and the second time constant through the collector-emitter circuit of the transistor TR3. To discharge. The second time constant is determined by the capacitance of the integrating capacitor C1, the resistance of the resistor R7 and the diode D6.
And the parallel combined resistance of the resistor R6 and the collector-emitter circuit of the transistor TR3.

That is, in this example, the control power supply circuit 8 and the resistor R
A circuit for charging the integrating capacitor C1 is constituted by the circuit of 5-resistor R6-integrating capacitor C1-control power supply circuit 8. A discharging circuit of the integrating capacitor is constituted by the integrating capacitor C1, the series circuit of the resistor R7 and the diode D6 and the parallel circuit of the resistor R6, the circuit between the collector and the emitter of the transistor TR3, and the integrating capacitor C1.

A discharge switch control circuit (resistors R8 and R9 and a diode D3) for controlling the on / off of the discharge switch (transistor TR3) according to the states of the charge circuit and the discharge circuit and the normal rotation command switch and the reverse rotation command switch.
7 to D9) constitute an integrating circuit 701.

The reference voltage generating circuit 702 is constituted by a voltage dividing circuit composed of resistors R10 and R11 connected in series between the output terminals of the control power supply circuit 8.
Is divided into a reference voltage Vr across the resistor R11.
Occurs. Let the output voltage of the control power supply circuit be E,
When the resistance values of 10 and R11 are represented by the same reference characters R10 and R11, respectively, the reference voltage Vr is given by the following equation.

Vr = E · R11 / (R10 + R11) (1) The comparator 703 compares the integrated voltage Vi with the reference voltage Vr, and when the integrated voltage Vi exceeds the reference voltage Vr, the enable signal V1 And a prohibition signal V0 is generated when the integrated voltage Vi is lower than the reference voltage Vr. In the illustrated example, the permission signal V1 is a high-level signal, and the prohibition signal V0 is a low-level signal.

The output signal of the comparator 703 is input to the on / off control circuit 7B together with the output of the PWM control circuit 6. The on / off control circuit 7B is a two-input AND circuit AN
1 and one input terminal A1 of the AND circuit AN1 and the positive output terminal of the control power supply circuit 8;
1 comprises resistors R12 and R13 connected between the other input terminal A2 and the positive output terminal of the control power supply circuit 8, respectively. The output signal of the comparator 703 is input to one input terminal A1 of the AND circuit, and the output terminal of the AND circuit is connected to the resistors R2 and R4 of the armature current control switch circuit 5.
Is connected to the connection point. When the potentials of the two input terminals A1 and A2 are both at a high level, the AND circuit AN1 generates an on / off control signal of a high level by satisfying an AND condition. A low-level (ground potential) on / off control signal is generated when in a low-level state. When the AND circuit AN1 is generating a high-level on / off control signal, the transistor TR2 is turned on.
1, a base current flows, and the transistor TR1 is turned on. When the AND circuit AN1 is generating a low level on / off control signal, the transistor TR2
Is turned off, the base current of the transistor TR1 is cut off, and the transistor TR1 is turned off.

The PWM control circuit 6 has a transistor TR4 whose emitter is grounded.
The collector of R4 is the other input terminal A of AND circuit AN1.
Connected to 2. A PWM control signal Vp having a pulse waveform that alternates between a high level state and a low level (ground potential) state at a predetermined duty ratio is input to the base of the transistor TR4, and the PWM control signal is in a high level state. During the period, the transistor TR4 is turned on.

When the high-level permission signal V1 is supplied from the permission signal prohibition signal generation circuit 7A to the input terminal of the AND circuit AN1, the transistor T of the PWM control circuit 6
When R4 is turned on, the potential of the input terminal A2 of the AND circuit AN1 is at a low level.
The output voltage of N1 goes low. When the transistor TR4 of the PWM control circuit 6 is turned off, the potential of the input terminal A2 of the AND circuit AN1 is at a high level, so that the output voltage of the AND circuit AN1 is at a high level. Therefore, when a high-level permission signal is given to A1 at the input terminal of the AND circuit AN1, the output (ON / OFF control signal) of the AND circuit AN1 is in a low level and a high level in accordance with the ON / OFF of the transistor TR4. To turn on / off the transistor TR1 of the armature current control switch circuit. A low-level inhibit signal V0 is input to the input terminal A1 of the AND circuit AN1.
Is applied, the output of the AND circuit AN1 is kept at a low level regardless of the on / off state of the transistor TR4, so that the transistor TR1 of the armature current control switch circuit 5 is kept off. Is done.

That is, the ON / OFF control circuit 7B allows the PWM control circuit 6 to control the ON / OFF of the transistor TR1 (semiconductor switch element) when the permission signal V1 is supplied, and when the prohibition signal V0 is supplied. PW
The on / off control of the transistor TR1 by the M control circuit 6 is inhibited, and the transistor TR1 is kept off.

In the DC motor driving device shown in FIG. 1, when driving the motor M, the power switch SW is first closed. As shown in the figure, when both the forward rotation command switch 3A and the reverse rotation command switch 3B are open (the state where the stop command signal is generated), the exciting current does not flow through the exciting coils RY1 and RY2. Contact 4A and second
The contact 4B of the relay has the movable contacts c1 and c
2 is in contact with the output-side fixed contacts b1 and b2, respectively. At this time, since the armature 2 is disconnected from the DC power supply 1, the electric motor is in a stopped state.

When both the forward command switch 3A and the reverse command switch 3B are open, the charging current is not supplied to the integrating capacitor C1 because the transistor TR3 constituting the discharging switch is on. The voltage across the integrating capacitor C1 is lower than the reference voltage Vr. Therefore, the comparator 703 outputs a low-level inhibit signal V0. In this state, the output of the AND circuit AN1 is at a low level (ground potential) irrespective of the state of the transistor TR4 of the PWM control circuit 6, so that the base of the transistor TR2 of the armature current control switch circuit 5 is maintained. Almost all current flows to the ground circuit through the output stage of AND circuit AN1. Therefore, the transistor TR2 is kept off, and no base current is supplied to the transistor TR1, so that the transistor TR1 is off.

Now, as shown in FIG. 2A, assuming that the forward rotation command switch 3A is closed at time t1, the power supply voltage VB is applied from the DC power source 1 to the exciting coil RY1 through the diode D1 and the forward rotation command switch 3A. Is applied, an exciting current flows through the exciting coil RY1. Time t1
When the exciting current flows through the exciting coil RY1 in FIG.
As shown in (C), the time t2 when the initial operation time T1 (the time required for the exciting current to reach the level required to separate the movable contact c1 from the fixed contact b1) has elapsed.
First, the movable contact c1 separates from the fixed contact b1.
Next, as shown in FIG. 2B, a time required for the movable contact c1 to be displaced from the position of the fixed contact b1 to the position of the fixed contact a1 is added to the switching operation time from the time t1 (the initial operation time T1). At time t3 when (time) T2 (> T1) has elapsed, the movable contact c1 contacts the fixed contact a1. During a predetermined time T3 immediately after the movable contact c1 contacts the fixed contact a1, bouncing of the movable contact c1 separating from the fixed contact a1 or contacting the fixed contact due to mechanical vibration of the movable system of the relay. (Bouncing) phenomenon occurs. The time T3 at which this bouncing phenomenon occurs is called the bounce time. At time t3, the movable contact c1 becomes the fixed contact a.
At time t4 after bounce time T3 (several milliseconds) elapses after contact with contact point 1, vibration of movable contact c1 stops, and movable contact c1 stably contacts fixed contact a1 (stable state). Calm down). At time t1, the exciting coil RY
The time Ton required for the movable contact c1 to settle into a stable state after the excitation current flows through the coil 1 will be referred to as the excitation operation stabilization time. The operation stabilization time Ton at the time of excitation is
= T2 + T3.

When the forward rotation command switch 3A is closed at time t1, the transistor TR3 constituting the discharging switch is turned off, so that the charging current flows from the control power supply circuit 1 to the integrating capacitor C1 through the resistors R5 and R6. Is supplied, and the integrating capacitor C1 is charged with the first time constant. Therefore, the integrated voltage Vi obtained at both ends of the integrating capacitor C1 rises as shown in FIG. At first, since the integral voltage Vi is lower than the reference voltage Vr,
The comparator 703 outputs a low-level inhibition signal V0 as shown in FIG. At time t5 after the first delay time T4 has elapsed from time t1, the integrated voltage Vi exceeds the reference voltage Vr, as shown in FIG.
The comparator 703 outputs a high-level permission signal V1. While the permission signal V1 is being generated, the AND circuit AN1
Since the potential of one input terminal is maintained at a high level, on / off control of the transistor TR1 by the PWM control circuit 6 is permitted.

The capacitance of the capacitor C1 is the same as that of the capacitor C1.
When the resistance values of the resistors R5 and R6 are represented by the same symbols R5 and R6, the first delay time T4 is given by the following equation.

T4 = − (R5 + R6) × C1 × ln {1−q / (C1 × E)} (2) where q is the charging voltage (integrating voltage) Vi of the integrating capacitor C1 is equal to the reference voltage Vr. The electric charge stored in the integration capacitor when they become equal, and is given by: q = C1 × Vr (3)

In the present invention, after the forward rotation command switch 3A generates a forward rotation command signal at time t1, the integrated voltage V
The time (i.e., the first delay time) T4 until i exceeds the reference voltage Vr is determined by the fact that the first movable contact c1 contacts the first input side fixed contact a1 after the first exciting coil RY1 is excited. The charging time constant (first time constant) of the integration capacitor C1 is set so as to be longer than the excitation operation stabilization time Ton required for stabilization. This time constant can be adjusted by the resistance values of the resistors R5 and R6.

When the permission signal V1 is generated, PW
Assuming that the PWM control signal is not supplied to the M control circuit 6 and the transistor TR4 of the control circuit is off, the output of the AND circuit AN1 is at a high level ("1").
), A base current is supplied from the DC power supply 1 to the transistor TR2 through the diode D1 and the resistors R2 and R4. Therefore, the transistor TR2 is turned on, and the transistor TR1 (semiconductor switch element) is turned on. When the transistor TR1 is turned on, the armature current flows through the path of the DC power supply 1—the transistor TR1—the fixed contact a1—the movable contact c1—the armature 2—the movable contact c2—the fixed contact b2—and the motor becomes positive. Rotate. When the transistor TR1 is turned on, the movable contact c1 of the first relay has already been set to the fixed contact a.
1 and has reached a stable state, so the movable contact c1
No arc is generated between the fixed contact a1.

When the armature current is subjected to PWM control, P
A PWM control signal Vp having a pulse waveform that repeats a high level state and a zero level state at a predetermined duty ratio is applied to the base of the transistor TR4 of the WM control circuit 6. When a PWM signal is applied to the base of the transistor TR4,
Since the transistor TR4 repeatedly turns on and off at a predetermined duty ratio, the output of the AND circuit AN1 repeats a low level state and a high level state in synchronization with the on / off operation of the transistor TR4. Thereby, the transistor T
R1 is turned on and off at the same duty ratio as the PWM control signal Vp, and the armature current is PWM controlled.

Next, when the forward rotation command switch 3A is opened at time t6 (a stop command signal is given), FIG.
As shown in (A), the power supply voltage applied to the exciting coil RY1 becomes zero. When the voltage applied to the exciting coil RY1 becomes zero, a voltage having a high polarity is induced in the exciting coil RY1 so as to keep the current flowing therethrough, so that a current flows through the exciting coil RY1 through the diode D4. Until the current attenuates below a predetermined value, the state where the movable contact c1 contacts the fixed contact a1 is maintained.

When the forward rotation command switch 3A is opened at time t6 (a stop command signal is generated), the transistor TR3
Is turned on, the charge of the integrating capacitor C1 is discharged at the second time constant through the series circuit of the resistor R7 and the diode D6, the parallel circuit of the resistor R6, and between the collector and the emitter of the transistor TR3.

After the forward rotation command switch is opened at time t6, when the second delay time T5 elapses and time t7 is reached,
Since the integrated voltage Vi becomes equal to or lower than the reference voltage Vr, the comparator 7
03 outputs a low-level inhibit signal V0. As a result, the output of the AND circuit AN1 becomes low level,
The transistor TR2 is turned off, and the transistor T2 is turned off.
R1 is turned off.

After the normal rotation command switch 3A is opened at time t6, and when the deactivating operation time Toff elapses and reaches time t8, the current flowing from the exciting coil RY1 through the diode D4 fixes the movable contact c1. The movable contact c1 separates from the fixed contact a1 because it attenuates to a value smaller than the level required to keep the contact a1 in contact. After the forward rotation command switch 3A is opened at time t6, a predetermined return time (a time obtained by adding a time required for the movable contact c1 to be displaced from the position of the fixed contact a1 to the position of b1 to the deactivation time Toff). After the elapse of T6 (> Toff), the movable contact c1 returns to the state of being in contact with the fixed contact b1.

After the movable contact c1 comes into contact with the fixed contact b1 at time t9, a bouncing phenomenon occurs for a predetermined bounce time T7. At time t10 when the bounce time T7 elapses from the time t9, the movable contact c1 is changed to the fixed contact b1. Settles in a stable contact state (stable state).

In the present invention, the normal rotation command switch 3A
Is opened (after a stop command signal is generated), the integrated voltage V
The time required for i to become equal to or lower than the reference voltage Vr (second delay time) T5 is determined by moving the movable contact c1 away from the fixed contact a1 after the forward rotation command switch 3A is opened (after the stop command signal is generated). The discharge time constant (second time constant) of the integration capacitor C1 is set so as to be shorter than the deactivation time Toff required before.

In the circuit of FIG. 1, ignoring the resistance of the diode D6 and the resistance of the collector-emitter circuit of the transistor TR3, the parallel combined resistance of the resistors R6 and R7 is represented by R [= R6 R7 / (R6 + R7)], the deactivation operation time Toff is given by the following equation.

Toff = −R × C1 × ln {q / (C1 × E)} (4) q = C1 × Vr (5) With the above setting, the transistor TR1 causes the armature current to After the interruption, the movable contact c1 becomes the fixed contact a1
Moving contact c when interrupting the armature current
An arc can be prevented from being generated between 1 and the fixed contact a1.

When the reverse rotation command switch 3B is closed, the operation is such that the exciting coil RY2 of the second relay is excited,
The operation is the same as that described above except that the movable contact c2 is brought into contact with the fixed contact a2. The movable contact c2 of the second relay
Is in contact with the fixed contact a2, the DC power supply 1—the emitter collector of the transistor TR1—the fixed contact a2—the movable contact c2—the armature 2—the movable contact c1—the fixed contact b1—
An armature current flows in the path of the DC power supply 1, and the motor is reversed. Second when the reverse rotation command switch 3B is opened
The operation of the first relay is the same as the operation of the first relay when the forward rotation command switch is opened. The operations of the permission signal prohibition signal generating circuit 7A and the on / off control circuit 7B when the reverse command switch is operated are the same as the operations when the normal command switch is operated.

In the present invention, the reverse rotation command switch 3B
Is closed (after the generation of the reverse rotation command signal) and the time required for the integrated voltage Vi to exceed the reference voltage Vr (first time).
After the second exciting coil RY2 is excited, the second movable contact c2 becomes the second input-side fixed contact a2.
Operation stabilization time T required to stabilize upon contact with
The charging time constant (first time constant) of the integrating capacitor C1 is set so as to be longer than on. If there is a difference between the energized operation time Ton of the first relay and the energized operation time Ton of the second relay, the first delay time T4 is set longer than the longer energized operation time Ton. Is set so that the charging time constant of the integrating capacitor C1 is longer.

In the present invention, the time (second delay time) T5 required for the integrated voltage Vi to become equal to or lower than the reference voltage Vr after the reverse command switch 3B generates the stop command signal is determined by the following. The deactivation time T required for the movable contact c2 to separate from the fixed contact a2 after occurrence.
The discharge time constant (second time constant) of the integration capacitor C1 is set so as to be shorter than off. The deactivated operation time Toff of the first relay and the deactivated operation time T of the second relay
If there is a difference between the off time and the off time, the discharge time constant of the integrating capacitor C1 is set so that the second delay time T5 is shorter than the shorter deactivation operation time Toff.

In the above example, the PNP transistor TR1 is used as the semiconductor switch element for controlling the armature current. However, the semiconductor switch element may be any element that can be controlled on and off, such as an NPN transistor or FET. It may be composed of another semiconductor switch element.

In the above example, the PWM control circuit 6 is provided. However, the present invention can be applied to a case where the PWM control circuit is not provided. When the PWM control circuit is not provided, the armature current control switch circuit 5
It is used only for turning on and off the armature current when starting and stopping the motor and switching the rotation direction.

In the device shown in FIG. 1, when the PWM control circuit 6 is omitted, the AND circuit AN1 is omitted, and the output terminal of the comparator 703 is directly connected to the resistors R2 and R4 of the switch circuit 5. Just connect it to a point.

FIG. 1 shows only an example of the configuration of the device according to the present invention.
Further, the configuration of the changeover switch circuit 4 is not limited to the illustrated one.

In the example shown in FIG. 1, the integrating capacitor C1
In order to prevent an arc from being generated when the movable contacts c1 and c2 of the relay are separated from the fixed contacts a1 and a2, respectively, the movable contacts c1 and c2 of the relay are connected to the discharge circuit of FIG. Before leaving the fixed contacts a1 and a2, respectively, the integrated voltage Vi is applied to the reference voltage V
Since the discharging of the integrating capacitor C1 may be performed promptly so as to be equal to or less than r, the resistance value of the resistor R7 can be made zero (the resistor R7 is omitted). When the resistance value of the resistor R7 is set to zero, the discharging time constant of the integrating capacitor (the second constant) is determined by the resistance of the diode D6, the resistance of the collector-emitter circuit of the transistor TR3, and the capacitance of the integrating capacitor C1. Is determined.

[0084]

As described above, according to the present invention, when a forward rotation command signal or a reverse rotation command signal is generated, the semiconductor switch element for controlling the armature current to turn on and off until the contact point of the relay becomes stable. Is kept in the off state, and the semiconductor switch element is turned on after the contact of the relay is stabilized, so that the armature current flows through the contact of the relay when the bouncing phenomenon occurs in the relay. This can prevent the occurrence of an arc at the contact of the relay. Further, when the stop command signal is generated, the switching operation of the relay contact is performed after the semiconductor switch element is turned off, so that an arc can be prevented from being generated at the relay contact.

As described above, according to the present invention, since the armature current is always turned on and off by the semiconductor switch element, an arc is generated at the contact point of the relay constituting the circuit for switching the polarity of the armature current. This prevents the contact from being consumed, thereby extending the life of the relay.

Further, since it is possible to prevent an arc from being generated at the contact point of the relay, it is possible to prevent the electromagnetic noise generated by the arc from adversely affecting peripheral control circuits and devices.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration example of a DC motor driving device according to the present invention.

FIG. 2 is a waveform diagram showing voltage waveforms at various parts in FIG. 1 and on / off operations of relay contacts.

FIG. 3 is a circuit diagram showing a configuration of a conventional DC motor driving device.

[Explanation of symbols]

 Reference Signs List 1 DC power supply 2 Armature of DC motor 3 Operation command circuit 3A Forward command switch 3B Reverse command switch 4 Changeover switch circuit 4A First relay contact a1 First input fixed contact b1 First output fixed contact c1 First movable contact RY1 First excitation coil 4B Second relay contact a2 Second input-side fixed contact b2 Second output-side fixed contact c2 Second movable contact RY2 Second excitation coil 5 Armature current Control switch circuit TR1 transistor (semiconductor switch element) TR2 transistor R1 to R4 resistor 6 PWM control circuit TR4 transistor 7 switch control circuit 7A permission signal prohibition signal generation circuit 701 integration circuit C1 integration capacitor R5 to R9 resistance D6 to D9 diode TR3 transistor 702 Reference voltage generation circuit 703 Comparator 7B ON / OFF control circuit

Claims (3)

[Claims] An operation command circuit for generating a forward rotation command signal and a reverse rotation command signal for instructing the DC motor to rotate forward and backward, and a stop command signal for instructing to stop the DC motor, The relay is energized when the forward command signal is generated and when the reverse command signal is generated, and includes a relay contact that is deenergized when a stop command signal is generated. The forward command signal and the reverse command signal And a switch circuit for switching the polarity of the armature current supplied to the DC motor in accordance with the above, and connected in series to the switch circuit for on / off control of the armature current flowing through the switch circuit. A DC motor drive device comprising: an armature current control switch circuit having a semiconductor switch element; When the time has elapsed, and when the first delay time has elapsed from the generation time of the reverse rotation command signal, the semiconductor switch element is turned on, and when the second delay time has elapsed from the generation time of the stop instruction signal. A switch control circuit for turning off the semiconductor switch element, wherein the first delay time is an exciting time required for a contact of the relay to perform a switching operation and settle to a stable state after the relay is excited. The second delay time is set to be shorter than the deactivation operation time required until the contact of the relay performs a switching operation after the relay is deactivated. A DC motor driving device, characterized in that: 2. An operation command circuit for generating a normal rotation command signal and a reverse rotation command signal for instructing the DC motor to rotate forward and reverse, and a stop command signal for instructing to stop the DC motor, The relay is energized when the forward command signal is generated and when the reverse command signal is generated, and includes a relay contact that is deenergized when a stop command signal is generated. The forward command signal and the reverse command signal And a switch circuit for switching the polarity of the armature current supplied to the DC motor in accordance with the above, and connected in series to the switch circuit for on / off control of the armature current flowing through the switch circuit. Armature current control switch circuit having semiconductor switch element, and PWM
A PWM control circuit for turning on and off the semiconductor switch element in response to a control signal, wherein the first delay time has elapsed from the generation time of the forward rotation command signal, and the generation of a reverse rotation command signal A permission signal prohibition signal generation circuit that generates a permission signal when a first delay time elapses from a time, and generates a prohibition signal when a second delay time elapses from the generation time of the stop command signal; The PWM control circuit permits the semiconductor switch element to be turned on when a permission signal is generated, and the PWM control circuit turns the semiconductor switch element on when the prohibition signal is generated. And an on / off control circuit for inhibiting the semiconductor switch element from being turned off, wherein the first delay time is after the relay is excited. The excitation operation stabilization time required for the contacts of the relay to perform a switching operation and settle to a stable state is set longer, and the second delay time is such that the contacts of the relay are switched after the relay is deenergized. A DC motor driving device, which is set to be shorter than an operation time at the time of deenergization required to perform the operation. 3. A direct-current power supply, a forward-rotation command switch for generating a forward-rotation command signal for instructing a forward rotation of the DC motor and a stop-command signal for instructing a stop of the forward rotation of the DC motor; An operation command circuit comprising: a reverse rotation command signal for instructing the DC motor to rotate in the reverse direction; and a reverse rotation command switch for generating a stop command signal for instructing to stop the reverse rotation of the DC motor, and the forward rotation command switch. A first excitation coil which is brought into an excited state and a non-excited state when a forward rotation command signal is generated and a stop command signal is generated, a first input side fixed contact, and a negative terminal of the DC power supply, respectively. A first output-side fixed contact connected to a circuit connected to the DC motor, and connected to one end of an armature of the DC motor so that the first excitation coil is excited and de-energized. A first relay having a first movable contact that contacts the first input-side fixed contact and the first output-side fixed contact, respectively, when the reverse command switch generates a reverse command signal. A second excitation coil which is brought into an excited state and a non-excited state when a stop command signal is generated, a second input-side fixed contact connected to the first input-side fixed contact, and a DC power supply, respectively. Connected to the circuit connected to the negative terminal of
And the second input-side fixed contact connected to the other end of the armature of the DC motor when the second excitation coil is excited and de-energized, respectively. And a second relay having a second movable contact in contact with the second output-side fixed contact; and a circuit connected to a connection point between the first and second input-side fixed contacts and a positive terminal of the DC power supply. Provided between
An armature current control switch circuit having a semiconductor switch element for turning on and off an armature current flowing from the DC power supply through contacts of first and second relays; and PWM control for turning on and off the semiconductor switch element in response to a PWM control signal. A DC motor drive device comprising: a first time constant for charging the integrating capacitor when the forward command switch generates a forward command signal and when the reverse command switch generates a reverse command signal. An integrating circuit having a charging circuit and a discharging circuit for discharging the integrating capacitor with a second time constant when both the forward command switch and the reverse command switch generate a stop command signal; and both ends of the integrating capacitor. Is compared with the reference voltage, and when the voltage across the integrating capacitor exceeds the reference voltage, the enable signal A permission signal prohibition signal generation circuit including a comparator that generates a prohibition signal when the voltage across the integration capacitor is equal to or lower than a reference voltage; and the PWM when the permission signal is generated. A control circuit permits the semiconductor switch element to be turned on, and when the inhibit signal is generated, the PWM control circuit prohibits the semiconductor switch element from being turned on and turns off the semiconductor switch element. An on-off control circuit for maintaining a state, a time required from the generation of the forward rotation command signal or the reverse rotation command signal until the integral voltage exceeds the reference voltage, after the first excitation coil is excited, An operation stabilization time during excitation required for the first movable contact to contact the first input-side fixed contact and settle to a stable state; and before the second excitation coil is excited. Wherein such second movable contact is longer than any of the second input-side fixed contact in contact with steady state excitation operation stabilization time required to settle the first
The time required for the integrated voltage to become equal to or less than the reference voltage after the forward command switch and the reverse command switch generate the stop command signal is determined by the forward command switch generating the stop command signal. And the deactivating operation time required for the first movable contact to separate from the first input-side fixed contact, and the second operation after the reverse command switch generates a stop command signal.
Wherein the second time constant is set so as to be shorter than any of the deenergizing operation times required for the movable contact to move away from the second input-side fixed contact.