JP2000350495A - Drive device for dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a drive device for a DC motor that can prevent the deterio ration of the contact switch of the DC motor, even when complexly operating the remote control switch of a remote controller at high speed. SOLUTION: An off detection circuit 26 detects the off state of remote control switches 18 and 20 according to the voltage between the terminals of a current detection resistor R, a monostable multivibrator MM outputs an H signal to a NOR circuit 28, and a transistor 24 is turned off, thus preventing a DC motor M from being activated, even when remote control switches 18 and 20 are operated for a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a DC motor.

[0002]

2. Description of the Related Art A DC motor is used for operations such as expansion and contraction of an electric actuator of a nursing bed. In this case, the DC motor is operated, stopped and controlled by a remote controller.
Forward rotation, reverse rotation, etc. are operated.

FIG. 7 is a circuit diagram of a conventional driving device 100, in which c-contact type relay switches 102 and 104 are provided on both sides of a DC motor M, respectively. Primary excitation coils 106, 1 of these relay switches 102, 104
08, a remote control switch 112, 11 is provided on a remote control 110 separate from the drive device 100.
4 are provided.

When the remote control switches 112 and 114 of the remote controller 110 are turned on or off, a current flows from the DC power supply V to the DC motor M through the relay switches 102 and 104, and the DC motor M
Is rotating forward, reverse or stopping.

[0005]

However, since the remote control switches 112 and 114 are manually operated, the remote control switches 112 and 114 may be complicated and operated at high speed.

In this case, an excessive starting current of the DC motor M flows continuously, and the relay switch 10
There is a problem that the life of the 2,104 contacts is significantly shortened due to deterioration or welding.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a DC motor driving device that can prevent the deterioration of the contact switch of the DC motor even when the remote control switch of the remote controller is operated at a high speed and complicated.

[0008]

According to a first aspect of the present invention, there is provided a driving apparatus for a DC motor, wherein a remote control switch provided on a remote control is turned on or off, and a primary excitation connected in series with the remote control switch is provided. A DC motor driving device that operates a DC motor by opening and closing a contact switch interlocked with the primary excitation coil by supplying or not supplying a current to the control coil. A resistor is connected in series, and an off detection circuit for detecting an off state of the remote control switch from a voltage between terminals of the current detection resistor is provided, and a predetermined time from when the off detection circuit detects the off state of the remote control switch is provided. During this time, the switching element is turned off even if the remote control switch is turned on or off. It is provided with a switching element control circuit of state.

According to the DC motor driving device of the present invention, once the remote control switch is turned off, the switching element is turned off for a predetermined time, and during that time,
Even if the remote control switch is turned on or off again, the switching element always keeps the off state, so that the DC motor does not start and the contact switch does not deteriorate.

That is, the switching element is turned off for a predetermined time after the remote control switch is turned off, and the DC motor is not started during the predetermined time regardless of the state of the remote control switch.

According to a second aspect of the present invention, there is provided a DC motor driving device in which a remote control switch provided on a remote control is turned on or off, and a current is supplied to a primary excitation coil connected in series with the remote control switch. Or
In the DC motor drive device that operates a DC motor by opening and closing a contact switch interlocked with the primary excitation coil by not flowing, a switching element and a current detection resistor are connected in series to the remote control switch, and the current detection is performed. An off detection circuit for detecting an off state of the remote control switch is provided from a voltage between terminals of a resistor, and the switching element is operated until a predetermined time elapses from when the off detection circuit detects the off state of the remote control switch. A switching element control circuit is provided for turning off the switching element and holding the switching element off until the remote control switch is turned off.

According to a second aspect of the present invention, the DC motor driving device holds the switching element in an off state until the remote control switch is turned on once the remote control switch is turned on from the time the remote control switch is turned off until a predetermined time elapses. , So as not to start the DC motor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a circuit diagram of a driving device 10 for a DC motor M according to the present invention.

Hereinafter, description will be made with reference to FIG.

On both sides of the DC motor M, c-contact type relay switches 12 and 14 are provided.
2, 14 are connected in series to the DC power supply V after being connected in parallel.

Primary excitation coil 1 of relay switch 12
The DC voltage Vcc is applied to 2a, and the other end
It is connected to a remote control switch 18 provided on a remote control 16 separate from the remote controller 16. Also, the DC voltage Vcc is applied to the primary excitation coil 14a of the relay switch 14,
The remote control switch 20 of the remote control 16 is connected in series.

The other end of the remote control switch 18 and the other end of the remote control switch 20 are connected and then grounded via a resistor R. Further, a collector terminal of a transistor 24 which is a switching element is connected to a connection point 22 between the remote control switch 18 and the remote control switch 20. The emitter terminal of the transistor 24 is grounded via the current detection resistor R1. Also, the transistor 24
An off detection circuit 26 is connected to the emitter terminal of the monostable multivibrator MM. Monostable multivibrator MM and connection point 2
A NOR circuit 28 is provided between the transistor 2 and the transistor 24. Specifically, the output of the NOR circuit 28 is connected to the base terminal of the transistor 24,
The connection point 22 and the output of the monostable multivibrator MM are connected to the two input terminals, respectively.

The operation state of the driving device 10 having the above configuration will be described with reference to the logic table of FIG. 2 and the timing chart of FIG.

The logic table of FIG. 2 shows the state of the two input terminals of the NOR circuit 28, the state of the output, and the state of the transistor 24.

First, a normal operation will be described. In normal operation, the remote control switch 18 of the remote control 16
Alternatively, by turning on / off the remote control switch 20, a current flows through the primary excitation coils 12a and 14a,
The relay switches 12 and 14 operate. When the a contact side and the c contact side of the relay switch 12 are connected and the b contact side and the c contact side of the relay switch 14 are connected, for example, the relay switch 12 rotates forward and the b contact side of the relay switch 12 is connected to the c contact side.
The contact side is connected, and the a contact side of the relay switch 14 and c
When the contact side is connected, it reverses. In other cases, the DC motor M is stopped.

When the DC motor M is driven to rotate forward or reverse, the transistor 24 is turned on,
Since the OFF detection circuit 26 does not detect the OFF state of the remote control switches 18 and 20, both input terminals of the NOR circuit 28 are L and L, and the output is H. Therefore, the transistor 24 is on as described above.

From the above normal state, the remote control switch 18
Alternatively, when the remote control switch 20 is turned off, the voltage between the terminals at both ends of the current detection resistor R decreases, whereby the off detection circuit 26 detects that the remote control switch 18 has been turned off. Then, an off detection signal is output from the off detection circuit 26 to the monostable multivibrator MM, and is output from the monostable multivibrator MM for a predetermined time t1 (for example,
H signal is output for only 0.5 second). Therefore, NO
The output of the R circuit 28 becomes L, and the transistor 24 is turned off. Therefore, no current flows through the primary excitation coil 12a, and the operation of the DC motor M is stopped. This operation stop state corresponds to the aforementioned monostable multivibrator MM.
Output time t1. Even if the operator turns on the remote control switch 18 or the remote control switch 20 during the predetermined time t1, the NOR circuit 2
Only when the input terminal on the side of the connection point 22 of H
Since the output of the circuit 28 remains at L, the transistor 2
4 is turned off. Therefore, even if the operator operates the remote control switches 18 and 20 at high speed during the predetermined time t1, the DC motor M does not start.

When a predetermined time has elapsed, the signal output from the monostable multivibrator MM to the NOR circuit 28 becomes L, so that the transistor 24 is turned on.

Thus, it is possible to perform the normal operation again.

With the drive device 10 as described above, even if the remote control switches 18 and 20 are quickly turned on / off, once the remote control switches 18 and 20 are once turned off, the DC is maintained for a predetermined time t1 thereafter. The motor M stops, and then the remote control switches 18 and 2
Since the DC motor M is not started even if 0 is turned on, the life of the relay switches 12 and 14 is extended. If a predetermined time has elapsed since the remote control switches 18 and 20 were turned off, the remote control switches 18 and 20 are again turned off.
20 allows the DC motor M to be operated, so that it can be used without discomfort. Thus, abnormal overheating of the DC motor M can be prevented.

(Second Embodiment) FIG. 4 is a circuit diagram of a driving device 10 according to a second embodiment. The difference from the first embodiment is that the DC motor M is rotated only in one direction. This is a circuit, and therefore, only one relay switch 12 and one remote control switch 18 are provided. Other structures and effects are the same as in the first embodiment.

(Third Embodiment) FIG. 5 is a circuit diagram of a driving device 10 according to a third embodiment, and FIG. 6 is a timing chart thereof.

A feature of the driving device 10 of the third embodiment is that the switching element 24 is turned off for a predetermined time t1 from the time when the remote control switches 18 and 20 are turned off. In other words, the DC motor M is not started regardless of the states of the motors 18 and 20.

[0030]

As described above, in the DC motor driving device according to the first aspect of the present invention, even if the remote control switch is operated at a high speed, the DC motor does not start for a predetermined time, so that the life of the contact switch is extended. In addition, abnormal overheating of the DC motor can be prevented.

Further, if a predetermined time has elapsed since the remote control switch was turned off, the DC motor can be operated again by the remote control switch, so that it can be used without discomfort.

According to a second aspect of the present invention, the switching device is held in an off state until the remote control switch is turned on once the remote control switch is turned on from the time the remote control switch is turned off until a predetermined time elapses. , The DC motor can be prevented from starting. Therefore, even if the remote control switch is operated at a high speed, the DC motor does not start for a predetermined time, so that the life of the contact switch is prolonged.
It is also possible to prevent abnormal overheating of the DC motor. Furthermore, if a predetermined time has elapsed since the remote control switch was turned off, the DC motor can be operated again by the remote control switch, so that the remote control switch can be used without discomfort.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a driving device for a DC motor according to a first embodiment.

FIG. 2 is a logic table of a NOR circuit.

FIG. 3 is a timing chart of the first embodiment.

FIG. 4 is a circuit diagram of a DC motor driving device according to a second embodiment.

FIG. 5 is a circuit diagram of a DC motor driving device according to a third embodiment.

FIG. 6 is a timing chart of the third embodiment.

FIG. 7 is a circuit diagram of a conventional DC motor driving device.

[Explanation of symbols]

 Reference Signs List 10 driving device 12 relay switch 12a primary excitation coil 14 relay switch 14a primary excitation coil 16 remote control 18 remote control switch 20 remote control switch 24 transistor 26 off detection circuit 28 NOR circuit M DC motor R current detection resistor MM monostable multivibrator

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H571 AA20 BB07 CC01 EE02 FF01 FF09 HA04 HA08 HB01 JJ19 KK10 LL22 LL50 MM02 MM20 PP02 5K048 AA04 BA12 DA01 DC04 EA01 EB02 FC03

Claims (2)

[Claims] A remote control switch provided on a remote controller is turned on or off, and a current is applied to a primary excitation coil connected in series with the remote control switch.
Or in a DC motor drive device that operates a DC motor by opening and closing a contact switch linked to the primary excitation coil by not flowing, connecting a switching element and a current detection resistor to the remote control switch in series, An off detection circuit for detecting an off state of the remote control switch from a voltage between terminals of a current detection resistor, wherein the remote control switch is turned on for a predetermined time from when the off detection circuit detects the off state of the remote control switch; A driving device for a DC motor, comprising: a switching element control circuit that turns off the switching element even when the switching element is in a state or an off state. 2. A remote control switch provided on the remote controller is turned on or off, and a current is applied to a primary excitation coil connected in series with the remote control switch.
Or in a DC motor drive device that operates a DC motor by opening and closing a contact switch linked to the primary excitation coil by not flowing, connecting a switching element and a current detection resistor to the remote control switch in series, An off detection circuit for detecting an off state of the remote control switch from a voltage between terminals of a current detection resistor, wherein the switching is performed until a predetermined time elapses after the off detection circuit detects the off state of the remote control switch. A driving device for a DC motor, further comprising a switching element control circuit for turning off the element and maintaining the off state of the switching element until the remote control switch is turned off.