JP2554444Y2 - Travel control device of forklift - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forklift traveling control device suitable for use in switching the traveling direction of a forklift.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a configuration of a conventional traveling control circuit of a forklift. It should be noted that the figure is simplified for explanation. In the figure, when the operator operates the forward / reverse switch 1 to switch to forward movement and depresses the accelerator 3, the forward contactor F and the powering contactor G enter and the contacts Fa and Ga are turned on (reverse to the illustration). State), and the CPU 2 turns on the transistor Tr1. As a result, current flows through the path of battery B → contact Ga → motor M → contact Fa → field winding 5 → contact Ra of reverse contactor R → transistor Tr1. In this case, the pulse width of the transistor Tr1 is controlled, and the ON time at the start of driving is set to a predetermined short time. Therefore, the motor current immediately after the start of driving is extremely small. And the transistor Tr1
Gradually increases, the current flowing through the motor M and the field winding 5 increases, the motor M rotates, and the rotation is transmitted to the wheels via gears in the transmission T, and the forklift Drive forward. Also, CP
U2 increases the current in accordance with a preset acceleration. Next, when the forklift is switched from the forward state to the reverse state, the reverse is selected by the forward / reverse switch 1 while the accelerator 3 is depressed. As a result,
The forward contactor F and the powering contactor G are cut off, the contacts Fa and Ga are turned off, the reverse contactor R is entered, and the contact Ra is turned on. At this time, since the field becomes reverse polarity, when the transistor Tr1 is turned off, the motor M → the contact Ra → the field winding 5
A regenerative current flows through the route of the flywheel diode SR1 → the battery B → the regenerative diode SR3, and the regenerative brake is applied. Then, when the regeneration is completed, the powering contactor G is turned on and the contact Ga is turned on, so that current is supplied to the motor. At this time, the direction of the current flowing through the field winding 5 is opposite to that at the time of forward movement, the motor M rotates in the reverse direction, and the forklift moves backward. Also, when the vehicle is switched from the reverse traveling state to the forward traveling, the forward traveling starts after the regenerative brake is applied in the same manner as described above. Note that SR2 shown in FIG. 3 is a diode for plucking.

[0003]

By the way, at the time when the regeneration is completed, the forklift is still traveling in the previous direction, and in this state, the powering contactor enters, the motor rotates in the reverse direction, and the predetermined rotation occurs. When the drive current is sequentially increased so as to increase the acceleration, there is a problem that the driver feels a large acceleration (shock) in the opposite direction depending on the situation. The present invention has been made in view of the above circumstances, and aims to provide a travel control device for a forklift in which a driver does not feel a large acceleration even when the traveling direction is switched during traveling. I have.

[0004]

In order to solve the above problems, a driving direction switching means for instructing a rotation direction of a motor serving as a driving source for driving a forklift, and a driving current supplied to the motor in accordance with a specified acceleration. In a travel control device of a forklift having acceleration control means for gradually controlling the value of the vehicle, a travel direction is switched by the travel direction switching means, a vehicle speed sensor for detecting a vehicle speed, a pressure sensor for detecting the weight of the loaded load. In this case, the vehicle speed obtained based on the output signal of the vehicle speed sensor exceeds a preset reference vehicle speed, and the load weight obtained based on the output signal of the pressure sensor is equal to or less than the preset reference weight. In this case, a command value smaller than the acceleration command value at the time of starting is supplied to the acceleration control means.

[0005]

When the traveling direction is switched under a certain condition, the acceleration command value when starting traveling in the opposite direction decreases.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. In this figure, parts corresponding to the respective parts in FIG. 3 described above are denoted by the same reference numerals, and description thereof is omitted. In the figure, reference numeral 10 denotes a pressure sensor for detecting the weight of the load loaded on the forklift, and reference numeral 11 denotes a speed sensor for detecting the speed of the forklift. Output signals from these sensors are supplied to the CPU 2.

Next, the operation of this embodiment having the above configuration will be described. The operation of this embodiment is substantially the same as the operation of the above-described conventional circuit, except for the operation when the traveling direction is switched during traveling. The operation in this case will be described below with reference to the flowchart shown in FIG. First, when the traveling direction is changed during traveling, the vehicle speed is detected in step SP1 of FIG. This detection is performed based on the output signal of the speed sensor 11. Next, in step SP2,
The weight of the load is detected based on the output signal of the pressure sensor 10. Then, it is determined whether or not the vehicle speed is higher than a preset reference speed (step SP3). If "NO", driving in the reverse direction is performed without changing the acceleration as in the conventional case (step SP5). This is because if the speed in the previous direction is sufficiently small, the driver will not feel a shock without changing the acceleration. On the other hand, if the determination in step SP3 is “YES”, it is determined whether the weight of the load is greater than a preset reference weight (step SP4). The determination in step SP4 is "Y
In the case of "ES", the driving in the reverse direction is performed without changing the acceleration as in the above-described case (step SP5). This is because if the load weight is large to some extent, the actual acceleration does not increase so much even if the drive current is increased, and the driver does not feel a shock without changing the acceleration. If "NO" is determined in the step SP4, the process proceeds to a step SP6, in which the acceleration is reduced by a predetermined ratio and the driving in the reverse direction is performed. Therefore, the rate of increase of the drive current at the time of reverse starting decreases. As described above, when the speed in the previous direction is equal to or higher than the reference speed and the load weight is equal to or lower than the reference weight, the acceleration in the reverse drive is reduced. That is, it is determined when the driver feels a shock if the acceleration is not changed, and the acceleration is changed only in this case.

[0008]

As described above, according to the present invention, when the traveling direction is switched under certain conditions, the acceleration command value at the time of starting traveling in the opposite direction becomes lower. Even when the switching is performed during traveling, the driver does not feel a large acceleration.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing the operation of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional forklift driving circuit.

[Explanation of symbols]

 Reference Signs List 1 forward / reverse switching device 1 2 CPU 3 accelerator M motor F forward contactor Tr1 transistor R reverse contactor 10 pressure sensor 11 speed sensor

Claims (1)

(57) [Scope of request for utility model registration] 1. A traveling direction switching means for instructing a rotation direction of a motor serving as a traveling drive source of a forklift, and acceleration control means for gradually controlling a value of a driving current supplied to the motor in accordance with a specified acceleration. A traveling speed sensor for detecting a vehicle speed, a pressure sensor for detecting a weight of a loaded load, and an output signal from the vehicle speed sensor when the traveling direction is switched by the traveling direction switching means. If the obtained vehicle speed exceeds the preset reference vehicle speed and the load weight obtained based on the output signal of the pressure sensor is equal to or less than the preset reference weight, a value smaller than the acceleration command value at the time of starting. A travel control device for a forklift, wherein the command value is supplied to the acceleration control means.