JPH1198618A - Controller for fork lift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fork lift controller capable of enhancing the controllability of its running DC shunt motor. SOLUTION: A current flows as shown by arrow (e) at a fall time of a field current flowing in the field coil 13 of a running motor from junction A to junction B, and the inductance energy of the field coil 13 is absorbed by a capacitor 23. If a second and a third field chopper devices 9 and 10 are turned on. when the field current becomes zero, a current flows as shown by arrow (f) and the capacitor 23 discharges. If the terminal-to-terminal voltage of the capacitor 23 or the potential VQ of the other end Q of the capacitor 23 decreases and becomes equal to or lower than a specified value, a switching device 25 is turned off, and a current flows from the field coil 19 of a loading motor to the field coil 13 of the running motor as shown by arrow (g), and the rise time of the field current flowing in the field coil 13 from junction B to junction A is shortened.

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 a forklift, and more particularly to a control device capable of switching the direction of a field current of a shunt motor for traveling in a short time.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional forklift controller having a DC shunt motor for traveling and cargo handling. One end of a switch 2 is connected to the positive electrode of the battery 1, and the armature 3, the armature current detector 4 and the armature chopper element of the DC shunt motor for traveling are connected between the other end of the switch 2 and the negative electrode of the battery 1. 5 are connected in series. A flywheel diode 6 is connected in parallel with the armature 3 and the armature current detector 4 connected in series with each other, and a snubber capacitor 7 is connected between the other end of the switch 2 and the negative electrode of the battery 1. ing. A series circuit of first and second field chopper elements 8 and 9 and third and fourth field chopper elements 10 and 11 are provided between both ends of the snubber capacitor 7.
Are connected in parallel to each other and connected to each other. In the field current control circuit section 12, between the connection point A of the first and second field chopper elements 8 and 9 and the connection point B of the third and fourth field chopper elements 10 and 11 The field winding 13 of the traveling motor and the traveling field current detector 14 are connected in series.

Further, an armature 15, an armature current detector 16 and an armature chopper element 17 of a DC shunt motor for cargo handling for driving a hydraulic pump for cargo handling (not shown) are connected in series between both ends of the snubber capacitor 7. A flywheel diode 18 is connected in parallel with a series circuit of the armature 15 and the armature current detector 16. Further, a field winding 19, a field current detector 20, and a field chopper element 21 of the loading motor are connected in series between both ends of the snubber capacitor 7, and the field winding 19 and the field current detector 20 are connected to each other. A flywheel diode 22 is connected in parallel with the series circuit.

The loading and unloading motor is driven by turning on / off the armature chopper element 17 and the field chopper element 21 by a drive circuit (not shown), and the armature chopper element 5 and the first to fourth field chopper elements. 8 to 1
The on / off control of 1 drives the traveling motor. The traveling motor needs to be rotated in opposite directions according to the forward / backward movement of the vehicle. However, by switching the direction of the field current flowing through the field winding 13, the rotation direction is reversed.

For example, when a current is applied to the field winding 13 from the connection point A to the connection point B, the first field chopper element 8
To turn on / off the fourth field chopper element 11. When the fourth field chopper element 11 is turned on, the first field chopper element 8, the field winding 13, the field current detector 14, and the fourth field chopper element 11 are supplied from the battery 1 or the snubber capacitor 7. , The current flows to the battery 1 or the snubber capacitor 7, and when the fourth field chopper element 11 is turned off, the inductance energy of the field winding 13 causes the field current detector 14, A current flows to the field winding 13 via the third field chopper element 10 and the first field chopper element 8.

Here, when the direction of the field current flowing through the field winding 13 is switched to flow from the connection point B to the point A, the field current needs to be temporarily set to zero. At this time, when the first and fourth field chopper elements 8 and 11 are turned off, the inductance energy of the field winding 13 causes the field winding 13 to output the field current detector 14 and the third field chopper. Field winding 13 via element 10, battery 1 or snubber capacitor 7, second field chopper element 9.
Current flows to the battery 1 or snubber capacitor 7
Then, the inductance energy of the field winding 13 is absorbed and consumed by the field resistance. As a result, the field current gradually attenuates to zero. Thereafter, by turning on the second and third field chopper elements 9 and 10, a field current flows through the field winding 13 from the connection point B to A.

[0007]

However, when the direction of the field current is switched as described above, even if the field current is once set to 0, the current is attenuated because the inductance of the field winding 13 is large. And the field current is 0
And the current flows in the opposite direction, the field winding 13
However, there is a problem that the rise of the current is delayed due to the large inductance. Therefore, it takes time to switch the direction of the field current, and there is room for improvement in the controllability of the DC shunt motor for traveling. The present invention has been made to solve such a problem, and an object of the present invention is to provide a control device for a forklift capable of improving the controllability of a DC shunt motor for traveling.

[0008]

A control device for a forklift according to the present invention is a control device for a forklift having a DC shunt motor for traveling and cargo handling, which absorbs inductance energy of a field winding of the traveling electric motor. And the direction of the current is connected so that the inductance energy of the field winding of the traction motor is absorbed by the capacitor when the current flowing through the field winding of the traction motor falls while being connected to the capacitor. The limiting diode is connected to the field winding of the loading motor and the current flowing through the field winding of the loading motor when the current flowing through the field winding of the traveling motor rises. And a switching element for supplying to the winding. When the current flowing through the field winding of the traction motor rises, the current stored in the capacitor causes the current to flow through the field winding of the traction motor. The current flowing through the motor can be supplied to the field winding of the traveling motor.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Embodiment 1 FIG. FIG. 1 shows a control device for a forklift according to Embodiment 1 of the present invention. One end of a switch 2 is connected to the positive electrode of the battery 1, a snubber capacitor 7 is connected between the other end of the switch 2 and the negative electrode of the battery 1, and an electric motor of a traveling DC shunt motor is connected between both ends of the snubber capacitor 7. The armature 3, the armature current detector 4, and the armature chopper element 5 are connected in series. A flywheel diode 6 is connected in parallel with the armature 3 and the armature current detector 4 connected in series with each other. A field current control circuit unit 12 including first to fourth field chopper elements 8 to 11 is connected to a negative electrode of the battery 1. In the field current control circuit section 12, between the connection point A of the first and second field chopper elements 8 and 9 and the connection point B of the third and fourth field chopper elements 10 and 11 A field winding 13 and a field current detector 14 of the traveling motor are connected in series. Further, a capacitor 23 for absorbing inductance energy of the field winding 13 is connected between the field current control circuit section 12 and the other end of the switch 2, and a current direction limiting diode 24 is connected in parallel with the capacitor 23. A series circuit with the field current switching element 25 is connected.

Further, between both ends of the snubber capacitor 7,
An armature 15, an armature current detector 16 and an armature chopper element 17 of a DC shunt motor for cargo handling for driving a hydraulic pump (not shown) for cargo handling are connected in series.
A flywheel diode 18 is connected in parallel with the series circuit of the armature current detector 16. Further, the field winding 1 of the loading motor is connected between both ends of the snubber capacitor 7.
9, the field current detector 20 and the field chopper element 21 are connected in series, and the connection point C between the field current detector 20 and the field chopper element 21 and the connection point D between the diode 24 and the field current switching element 25 Is connected to the flywheel diode 22.

That is, the control device according to the first embodiment differs from the conventional control device shown in FIG. 5 in that a capacitor 23 is connected between the field current control circuit section 12 and the other end of the switch 2. Diode 24 in parallel with capacitor 23
And a series circuit of a field current switching element 25 and one end of a flywheel diode 22 are connected to a connection point D between the diode 24 and the field current switching element 25.

Next, the operation of the control device will be described. First, the voltage and current applied to the armature 3 of the traveling motor are controlled by turning on / off the armature chopper element 5. When the armature chopper element 5 is on, the switch 1 from the battery 1, the armature 3, the armature current detector 4
And a current flows to the battery 1 via the armature chopper element 5, and when the armature chopper element 5 is off,
A current flows from the armature 3 to the armature 3 via the armature current detector 4 and the flywheel diode 6. Similarly,
The voltage and current applied to the armature 15 of the loading motor are controlled by turning on / off the armature chopper element 17. When the armature chopper element 17 is on, the switch 1 from the battery 1, the armature 15, the armature current detector 1
6 and the armature chopper element 17, a current flows to the battery 1. On the other hand, when the armature chopper element 17 is off, the armature 15 flows to the armature 15 via the armature current detector 16 and the flywheel diode 18. Current flows.

The field formed by the field winding 13 of the traveling motor is the first to the first in the field current control circuit 12.
The control is performed by turning on / off the fourth field chopper elements 8 to 11. For example, when a current flows through the field winding 13 from the connection point A to the connection point B, the first field chopper element 8 is turned on and the fourth field chopper element 11 is turned on / off.
Turn off. When the fourth field chopper element 11 is on, the switching element 25 and the diode 2 are switched from the battery 1 or the snubber capacitor 7 as shown by an arrow a in FIG.
4. A current flows to the battery 1 or the snubber capacitor 7 via the first field chopper element 8, the field winding 13, the field current detector 14, and the fourth field chopper element 11.
When the fourth field chopper element 11 is turned off, the field winding 1
As shown by the arrow b in FIG. 1, the inductance energy of the magnetic field 3 passes through the field winding 13, the field current detector 14, the third field chopper element 10, and the first field chopper element 8. A current flows to the field winding 13.

On the other hand, the field formed by the field winding 19 of the electric motor for cargo handling is controlled by turning on / off the field chopper element 21. When the field chopper element 21 is turned on, the battery 1 or the snubber capacitor 7 passes through the field winding 19, the field current detector 20, and the field chopper element 21 as shown by an arrow c in FIG. Alternatively, current flows to snubber capacitor 7. When the field chopper element 21 is turned off, the inductance energy of the field winding 19 causes the field current detector 20, the flywheel diode 22, and the switching device to switch from the field winding 19 as shown by an arrow d in FIG. A current flows to the field winding 19 via the element 25.

Here, in order to switch the direction of the field current flowing through the field winding 13 to flow from the connection point B to the point A in order to rotate the traveling motor in the reverse direction,
In order to temporarily reduce the field current to 0, the first and fourth field chopper elements 8 and 11 are turned off, for example, at time t1 shown in FIG. At this time, the inductance energy of the field winding 13 causes the capacitor 23 to pass through the field current detector 14 and the third field chopper element 10 from the field winding 13 as shown by an arrow e in FIG. Current flows into the
Further, the current flows to the field winding 13 via the battery 1 or the snubber capacitor 7 and the second field chopper element 9. As a result, the inductance energy of the field winding 13 is rapidly absorbed by the capacitor 23, the field current flowing through the field winding 13 is attenuated and the capacitor 23 is charged as shown by the curve R in FIG. . At this time the charge stored in the capacitor 23 because the reverse polarity to the battery 1, than potential V _P of the one end P of the capacitor 23 connected to the switch 2, which is connected to the field current control circuit section 12 If the potential _{V Q} at the other end Q of the capacitor 23 becomes higher. In FIG. 2, the potentials _VP and _VQ are represented by setting the potential of the negative electrode of the battery 1 to 0, and the field current flowing through the field winding 13 in the conventional control device of FIG. Is shown by the curve S.

When the cargo handling operation is not performed,
At time t1 when the first and fourth field chopper elements 8 and 11 were turned off, the field chopper element 21 was turned on, and the field current flowing through the field winding 19 of the loading motor was changed as shown by a curve T in FIG. To increase. Then, when the field current reaches a predetermined value, the field current is controlled by turning on / off the field chopper element 21. Here, when the switching element 25 is turned off, the field current 19
0, a current flows into the capacitor 23 or the field winding 13 of the traveling motor via the diodes 22 and 24,
When the switching element 25 is turned on, the flow of current from the field winding 19 is stopped. Therefore, by the potential V _Q of the other end Q of the voltage across or the capacitor 23 of the switching element 25 the capacitor 23 is turned on when greater than the predetermined value, is turned off when the predetermined value or less, the capacitor 23
It is possible to control the maximum value of the potential V _Q of the other end Q of.

Thus, at time t2, the field winding 13
Is completely absorbed by the capacitor 23, the field current becomes zero. Here, the second and third
When turning on the field chopper element 9 and 10, the potential V _Q of the other end Q of the capacitor 23 by the charge stored in the capacitor 23 is higher than the potential V _P of the end P, an arrow f in FIG. 1 As shown in FIG.
To the third field chopper element 10, the field current detector 1
4. Field winding 13, capacitor 23 via second field chopper element 9 and battery 1 or snubber capacitor 7.
The current starts to flow to. Thus, the capacitor 23 is discharged, the potential V _Q of the other end Q of the voltage across or the capacitor 23 of the capacitor 23 is reduced, and becomes equal to or less than the predetermined value at time t3, switching element 25 is turned off, in Figure 1 As shown by the arrow g, the field winding 19, the field current detector 20, the diodes 22 and 24, the third field chopper element 10, the field current detection of the loading motor from the battery 1 or the snubber capacitor 7 A current flows to the battery 1 or the snubber capacitor 7 via the switch 14, the field winding 13 of the traveling motor, and the second field chopper element 9. For this reason,
Decrease in the potential V _Q of the other end Q of the voltage across or the capacitor 23 of the capacitor 23 is prevented, the rise time of the field current flowing toward the A field winding 13 from the connection point B is shortened.

Since the current value of the field winding 19 is determined by the control of the electric motor for cargo handling, its maximum value is limited during the cargo handling operation. As a result, the voltage across the capacitor 23 or the voltage of the capacitor 23 is reduced. the holding force of the potential V _Q at the other end Q is reduced.

At time t4 when the value of the field current from node B to A detected by the field current detector 14 reaches a predetermined value which occupies a certain ratio with respect to the target value, the switching element 25 is turned on. Is turned on, and if no cargo operation is performed at this time, the field chopper element 21 is further turned off. As a result, the charge of the capacitor 23 gradually approaches 0, and the switching element 2 is switched from the battery 1 or the snubber capacitor 7.
5, a current flows to the battery 1 or the snubber capacitor 7 through the diode 24, the third field chopper element 10, the field current detector 14, the field winding 13 of the traveling motor, and the second field chopper element 9. Begins to flow.

In this way, the direction of the field current flowing through the field winding 13 is switched from the connection point B to the connection point A. When the field current falls, the inductance energy of the field winding 13 is reduced. Since the energy is absorbed by the capacitor 23 and the energy accumulated in the capacitor 23 and the inductance energy of the field winding 19 of the cargo handling motor are used at the time of rising, the fall time and the rise time are shortened. Therefore, the direction of the field current flowing through the field winding 13 can be switched in a short time,
It is possible to improve the controllability of the DC shunt motor for traveling.

Embodiment 2 FIG. FIG. 3 shows a control device for a forklift according to Embodiment 2 of the present invention. This control device is different from the device of the first embodiment shown in FIG. 1 in that a capacitor 23 connected between the field current control circuit 12 and the other end of the switch 2, a current direction limiting diode 24, The switching element 25 is connected between the field current control circuit section 12 and the negative electrode of the battery 1. Also,
The field winding 19, the field current detector 20, and the field chopper element 21 of the electric motor for cargo handling are arranged in order from the negative electrode side to the positive electrode side of the battery 1, contrary to the device of the first embodiment. Even with such a configuration, the same effects as in the first embodiment can be obtained. That is, the field winding 1 of the traveling motor
3, the capacitor 23 absorbs the inductance energy of the field winding 13 when the field current falls, and uses the energy accumulated in the capacitor 23 and the inductance energy of the field winding 19 of the cargo handling motor when rising. Thus, the direction of the field current flowing through the field winding 13 can be switched in a short time.

Embodiment 3 FIG. FIG. 4 shows a control device for a forklift according to Embodiment 3 of the present invention. This control device is different from the device of the first embodiment shown in FIG. 1 in that the capacitor 23 connected between the field current control circuit unit 12 and the other end of the switch 2 is replaced with the field current control circuit unit 12.
And connected in parallel. With such a configuration, each of the field chopper elements 8 to
Since the switching surge 11 is absorbed by the capacitor 23, it is necessary to increase the size of the capacitor 23. However, the same effect as in the first or second embodiment can be obtained.

[0023]

As described above, according to the control device for a forklift according to the present invention, a capacitor for inductance energy absorption, a diode for current direction limitation and a switching element are added to the conventional control device. The fall time and the rise time of the field current flowing through the field winding of the traveling motor can be reduced, and the controllability of the traveling motor is improved. Also, only when switching the traveling direction, the current flowing through the field winding of the cargo handling motor is supplied to the field winding of the traveling motor and used, so that the controllability of the traveling motor is reduced while suppressing energy loss. Improvement can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing an operation of the control device according to the first embodiment.

FIG. 3 is a circuit diagram showing a control device for a forklift according to a second embodiment.

FIG. 4 is a circuit diagram illustrating a control device for a forklift according to a third embodiment.

FIG. 5 is a circuit diagram showing a conventional forklift control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 3 Armature of traveling motor 5, 17 Armature chopper element 7 Snubber capacitor 8 First field chopper element 9 Second field chopper element 10 Third field chopper element 11 Fourth field chopper Element 12 Field current control circuit section 13 Field winding of running motor 15 Armature of loading motor 19 Field winding of loading motor 23 Capacitor 24 Diode 25 Switching element

Claims (2)

[Claims] 1. A control device for a forklift having a DC shunt motor for traveling and cargo handling, comprising: a capacitor for absorbing inductance energy of a field winding of the traveling motor; A diode for limiting the current direction so that the inductance energy of the field winding of the traveling motor is absorbed by the capacitor when the current flowing through the field winding of the driving motor falls; and a field winding of the loading motor. And a switching element for supplying a current flowing through the field winding of the cargo handling motor to the field winding of the traveling motor when the current flowing through the field winding of the traveling motor rises. A control device for a forklift, comprising: 2. The switching device according to claim 1, wherein said switching element causes a current to flow through a field winding of said traveling motor by energy stored in said capacitor when a current flowing through said field winding of said traveling motor rises. The control device for a forklift according to claim 1, wherein a current flowing through a field winding of the motor is supplied to a field winding of the traveling motor.