JPH08126385A - Motor controller - Google Patents

Abstract

PURPOSE: To obtain a motor controller in which the service life of an electromagnetic switch for regeneration can be sustained for a long term by decreasing the operational frequency thereof as much as possible. CONSTITUTION: A control section 3 controls the coil MG of an electromagnetic switch, having a contact (mg) for regeneration being closed during forward rotation and reverse rotation of a motor 1, to be actuated as is for a predetermined time after an advance command or a retract command is stopped. Consequently, when a next retract or advance command is provided within a predetermined time, the number of operating time of regeneration electromagnetic switch can be decreased by 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor control device, and is particularly useful when applied to an electric motor for running an electric vehicle such as a battery forklift truck when regenerative braking is performed in addition to forward and reverse rotation.

[0002]

2. Description of the Related Art FIG. 1 is a circuit diagram showing a general circuit configuration of a control device for an electric motor for running a battery forklift.

As shown in the figure, the electric motor 1 in this case is a DC direct-winding electric motor, has an armature 1a and a field winding 1b, is driven by a battery 2 as a power source, and is a main circuit chopper. The speed of the transistor T _M is controlled by controlling the conduction time of the transistor T _M.

The control unit 3 controls the conduction of the transistor T _M so that the electric motor 1 rotates at a predetermined speed based on the electric current supplied to the electric motor detected by the current detector 4, and at the time of performing regenerative braking, regenerative braking is performed. The transistor T _G is turned on, the field winding 1b is pre-excited via the resistor R _G, and the operation of each electromagnetic switch is controlled.

There are four types of electromagnetic switches, one for forward rotation of the electric motor 1 (hereinafter referred to as forward movement), the other for reverse rotation (hereinafter referred to as backward movement), regeneration, and full-speed traveling. Each coil has an MF, The MR, MG, and MS symbols are assigned, and the a-contacts are labeled with mf, mr, mg, and ms symbols in the figure.

In these electromagnetic switches, the control unit 3 energizes the coils MF, MR, MG, and MS to make contact points m.
f, mr, mg, ms are each closed, and the coil M
By deactivating F, MR, MG, MS, contact points mf,
mr, mg and ms are released.

Thus, the coils MF and MG are energized when the battery forklift is moving forward, the coils MR and MG are energized when the battery is moving backward, and only one of the coils MF and MR is energized when regenerating. Further, at the full speed running, the coil MS is also energized to short-circuit the transistor T _M by the contact ms and apply the full voltage to the electric motor 1.

The diodes DF1 and DF2 are flywheel diodes, and the diode DG is a regenerative diode for returning a regenerative current to the battery 2. The capacitor C _A , the resistor R _A and the diode D _A are connected to the transistor T.
_It composes the CRD snubber circuit that is the surge absorber for _M.

[0009]

In the control unit 3 as described above, the contacts mf and mg are closed at the time of forward command,
When a reverse command is issued from this state, the contact points mf, m
After g is once opened, the contacts mr and mg are closed.
That is, the contact mg is opened and closed in conjunction with the contacts mf and mr, and is opened during regeneration. Therefore, there is a problem that the frequency of operation of the regenerative electromagnetic switch having the contact mg and the coil MG for operating the contact is high, and the life is short as compared with other electromagnetic switches.

In view of the above problems, the present invention provides a control device for an electric motor which can reduce the frequency of operation of an electromagnetic switch for regeneration as much as possible and can maintain the life of the electromagnetic switch for a long period of time. With the goal.

[0011]

Means for Solving the Problems The structure of the present invention for achieving the above object is to provide an electromagnetic switch for forward rotation and reverse rotation of an electric motor, an electromagnetic switch for regeneration of the electric motor, and a forward rotation for forward rotation of the electric motor. Close the forward rotation contact of the electromagnetic switch and the regenerative contact of the regenerative electromagnetic switch, open the reverse contact of the reverse electromagnetic switch, and open the reverse contact and the regenerative contact during reverse rotation. A control device for an electric motor having a control means for closing the forward rotation contact and opening the forward rotation contact, and further for closing the forward rotation contact or the reverse rotation contact and opening the regeneration contact during regeneration. The control means is configured to control the electromagnetic switch for regeneration so as to maintain the closed state of the regeneration contact for a certain period of time after the forward rotation contact or the reverse rotation contact is opened. To do.

[0012]

According to the present invention having the above-described structure, even if the forward rotation instruction or the reverse rotation instruction of the electric motor is stopped and the forward rotation or reverse rotation contact is opened, the regeneration contact remains closed for a certain period of time. Therefore, if a reverse rotation command or a forward rotation command is issued during that time, the contact for regeneration is maintained in the closed state as it is. That is, even if the rotation direction of the electric motor is reversed, the regenerative electromagnetic switch maintains the closed state without opening its contact once.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings.

This embodiment is also a control device for an electric motor for running a battery forklift. Therefore, the basic circuit configuration is the same as that of the circuit shown in FIG. Only the control algorithm by the control unit is different. Therefore,
A description of the overlapping parts will be omitted.

The control unit 3 in this embodiment energizes the coils MF and MG of the electromagnetic switch on the basis of the forward command to contact the contacts m.
While closing f and mg, the coil MR and MG of the electromagnetic switch are biased based on the backward command to close the contacts mr and mg, which is the same as the conventional one, but the forward command or backward command is stopped. When this is done, the coils MF and MR are simultaneously de-energized as in the conventional case, while the coil MG is controlled so as to maintain the energized state for a certain period of time. Then, when no command is issued even after a lapse of a fixed time, the coil MG is deenergized and the contact mg is opened.

According to this embodiment, as shown in FIG.
At time t₁Forward command S_FIs issued
Then, the coils MF and MG are simultaneously energized. Then time
Interval t ₂Forward command S_FWhen is stopped, the coil MF is
The coil MG is sometimes deenergized, but the coil MG is energized for a certain time T.
Is maintained.

Therefore, the time t before the elapse of the fixed time T
_{When the} reverse command S _R is issued at ₃ , the coil MR is energized and the coil MG is energized.

On the other hand, if no command is issued even after the elapse of the fixed time T, the coil MG is deenergized. This is because the motor 1 is in the stop mode in this case.

That is, according to this embodiment, after the forward movement command or the backward movement command is stopped, if the backward movement command or the forward movement command is issued within a certain time T, the contact mg of the electromagnetic switch for regeneration is
During this period, the number of operations can be reduced by maintaining the closed state without repeating the opening / closing operation.

[0020]

As described above in detail with reference to the embodiments, according to the present invention, the number of times of operation of the electromagnetic switch for regenerating the electric motor can be reduced, so that the service life can be extended accordingly. ..

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a control device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms at various parts in FIG.

[Explanation of symbols]

 1 motor 2 battery 3 control unit MF, MR, MG, MS coil of electromagnetic switch mf, mr, mg, ms contact of electromagnetic switch

Claims (3)

[Claims] 1. An electromagnetic switch for normal rotation and reverse rotation of an electric motor, an electromagnetic switch for regeneration of the electric motor, a contact for normal rotation of the electromagnetic switch for forward rotation and an electromagnetic switch for regeneration when the electric motor is in the normal rotation. The regenerative contact is closed and the reverse contact of the electromagnetic switch for reverse rotation is opened, the reverse contact and the regenerative contact are closed during reverse rotation, and the forward contact is opened, and further during regeneration. In a controller of a motor having a control means for controlling the contact for forward rotation or the contact for reverse rotation to be closed and opening the contact for regeneration, the control means is configured so that the contact for forward rotation or the contact for reverse rotation is opened. A control device for an electric motor, characterized in that it is configured to control an electromagnetic switch for regeneration so as to maintain the closed state of the contact for regeneration for a certain period of time after the start. 2. The electric motor control device according to claim 1, wherein the electric motor is a DC series-wound electric motor using a battery as a power source. 3. The electric motor control device according to claim 1, wherein the electric motor is a direct current winding electric motor that uses a battery as a power source, and is a traveling electric motor of an electric vehicle.