JPS61167302A - Self-propelled truck - Google Patents

Abstract

PURPOSE:To prevent a terminal voltage from rising or a self-driven truck from traveling at an overspeed by connecting a resistor between terminals of a drive motor when the truck becomes a descent traveling state so that the motor becomes a generating mode. CONSTITUTION:When a current IM flows to a motor 10, a forward voltage drop VF occurs at a diode 13, and a current (i) flows to the LED14a of a photocoupler 14. Thus, the LED14a emits a light, and a PTr14b becomes ON. Accordingly, a transistor 11 remains OFF state, and a resistor 12 is disconnected from between the terminals of the motor 10. When the rotating speed of the motor 10 rises so that the terminal voltage VM of the motor 10 approaches the voltage of a power source 8, the current IM reduces almost to zero. Thus, the transistor 11 is switched to ON, the resistor 12 is connected to between the terminals of the motor 10, and the motor 10 becomes a generating braking state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a self-propelled cart for a transportation system using rails, and particularly to a self-propelled cart that can run stably even on a descending rail portion.

[Background of the invention]

In recent years, large hospitals have installed rails along predetermined routes, such as the ceilings of hallways and walls of rooms, and used self-propelled carts that automatically travel on these rails to move goods to their destinations. Conveyance systems designed to convey documents and documents have come into use. Incidentally, such a system is disclosed in, for example, Japanese Unexamined Utility Model Publication No. FJli 52-9991 and Japanese Utility Model Application Publication No. 52-24689.

Such a conveyance system, for example, as shown in Figure 2,
A self-propelled cart 2 runs on a rail 1 to transport goods, etc. For this purpose, the rail 1 is provided with a pair of power supply rails 3 and 4, as shown in FIG. The self-propelled trolley 2 is equipped with sliding electronics 5.6s, f me l--71z
mth Hibiki + 7Pi J&I-tAJ, SouJ P-T
h 'ffi k JL. In addition, in FIG. 2, 7 represents an operation panel, and in FIG. 3, 8 represents a power source.

By the way, in such a transportation system, the rail 1 is often installed along a vertical surface such as a wall of a room.
Therefore, as shown in Fig. 2, there is a vertical rail section 1', and when the self-propelled trolley 2 travels in the downward direction on this section, the traveling motor goes into power generation mode due to gravitational energy and supplies power. There is a problem in that the voltage between the rails 3 and 4 increases greatly from the rated value, causing the motor to overheat or the self-propelled trolley 2 to run at excessive speed, resulting in a dangerous situation.

At this time, if electric power is absorbed from the motor rotating in the power generation mode, the above-mentioned voltage increase can be prevented, and there is no possibility that the self-propelled trolley 2 will overspeed due to the power generation brake being applied.

Therefore, in the past, a resistor was connected between the power supply rails 3 and 4, and the dynamic brake was applied by this resistor.
The disadvantage is that the current spreads out, resulting in wasteful power consumption.

On the other hand, instead of this method of connecting a resistor between the power supply rails, a third resistor is installed only on the rail portion where the self-propelled trolley travels downward.
A method has also been proposed in which a power supply rail is provided and the resistor is connected between the terminals of the self-propelled trolley's motor only at this part, but this method has the disadvantage of requiring the installation of an extra power supply rail. There is. Note that these methods are disclosed in, for example, Japanese Unexamined Patent Publication No. 56-27412.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to connect a resistor between the terminals of the motor only when the self-propelled truck is in a downward traveling state and the traveling motor is in the power generation mode. To provide a self-propelled trolley which is connected to the vehicle and can reliably prevent an increase in terminal voltage and overspeed running.

[Summary of the invention]

In order to achieve this object, the present invention provides a switch means that is turned on only when the current flowing into the travel motor from the power supply side becomes less than a predetermined value, and connects a resistor between the terminals of the motor by this switch means. It is characterized by the following points.

[Embodiments of the invention]

EMBODIMENT OF THE INVENTION Hereinafter, the self-propelled trolley according to the present invention will be explained in detail with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which 10 is a running motor, 11 is a switching transistor, 12 is a power absorption resistor, 13 is a current detection diode, 1
Reference numeral 4 designates a 7-opto coupler, 15° and 16 designate resistors for current limiting, and the rest are the same as in the case of FIGS. 2 and 3. Note that 14α is a light emitting diode (LFtD) that serves as a light emitting portion of the photocoupler 14, and 146 is a phototransistor (PTr) that serves as a light receiving portion.

Next, the operation of this embodiment will be explained.

The driving motor 10 is a direct current motor such as a shunt field type, a separately excited field type, or a permanent magnet field type, and is connected to a power source 8 by a control circuit (not shown) and is driven to travel in a direction. At this time, the magnitude of the torque generated by the motor 10 is approximately proportional to the current IM, and the rotational speed is approximately proportional to the voltage vM.

On the other hand, when current flows through the motor 10, a forward voltage drop Va appears in the diode 13, and as a result, a current i flows in the LID 14a of the photocoupler 14.
flows. Then, LED14α emits light and P'I'r1
46 is turned on, which causes the voltage between the base and emitter of transistor 11 to be approximately zero, so that transistor 11 remains off and resistor 12 is disconnected from the terminals of motor 10.

Next, suppose that while the self-propelled trolley 2 is traveling in this manner, it enters the vertical rail portion 1' shown in FIG. 2 from above.

When this happens, acceleration due to gravity acts on the self-propelled trolley 2, increasing its traveling speed, and the rotational speed of the motor 10 increases. As a result, the terminal voltage vM of the motor 10
The current error decreases to almost zero when the pressure increases accordingly.

Therefore, this results in a voltage drop V? of the diode 13? becomes almost zero, and as a result, the LE of Photo Cub 514
Dl 4a goes out, PTr14b switches off,
Along with this, a resistor 1 is connected to the base of the transistor 11.
Current flows through 6 and transistor 11 is turned on. As a result, the resistor 12 is connected to the motor 10.
This means that it is connected between the terminals of

On the other hand, since the motor 10 is constituted by a DC motor such as a shunt field type, a separately excited field type, or a permanent magnet field type as described above, its terminal voltage vM is higher than the voltage of the power supply 8. In the high state, it automatically operates in the power generation mode, and as a result, when the resistor 12 is connected between the terminals of the motor 10, a current IR flows from the motor 10 to the resistor 12, and as a result, the motor 10 generates a torque in the opposite direction, enters a dynamic braking state, and operates to suppress the acceleration of the self-propelled trolley 2.

Therefore, the resistance value of this resistor 12 is now set to a predetermined value, so that the terminal voltage vM of the motor 10 when a predetermined value of current IR flows is maintained at a value approximately equal to the voltage of the power supply 8. By doing so, the traveling speed when the self-propelled trolley 2 is traveling down the vertical rail portion 1' can be kept almost the same as the traveling speed when traveling on the horizontal rail. , it is possible to sufficiently suppress the terminal voltage vM of the motor 10 from increasing significantly from the rated value.

Eventually, when the self-propelled trolley 2 reaches the horizontal rail, the acceleration effect due to gravity disappears, the rotational speed of the motor 10 decreases, and the terminal voltage vM begins to decrease. As a result, when the terminal voltage vM drops below the voltage of the power source 8, the current error starts flowing from the power source 8 again, and the motor 10 generates torque and operates in the electric mode. On the other hand, when a current error flows from the power supply 8 in this way, a forward voltage drop v7 appears again in the diode 13, and as a result, the transistor 11 is turned off and the resistor 12 is disconnected from between the terminals of the motor 10. It will be released and the vehicle will return to normal driving condition.

Therefore, according to this embodiment, when the self-propelled trolley 2 is accelerated by an external force such as gravity while traveling, the resistor 12 is automatically connected between the terminals of the motor 10, and the dynamic braking function is activated. Therefore, increases in the terminal voltage of the traveling motor and the traveling speed of the bogie can be sufficiently suppressed without wasting power consumption or requiring the installation of extra rails.

In the above embodiment, the detection output for on/off control of the switching transistor 11 is obtained by the forward voltage drop (7) of the diode 13 connected in series with the driving motor 10. A substantially constant voltage V can be obtained almost regardless of the magnitude of the current error, and reliable operation can always be obtained.

Further, in this embodiment, since the photocoupler 14 is used, current detection and control of the switching transistor can be electrically isolated, and the circuit configuration can be simplified.

〔Effect of the invention〕

As explained above, according to the present invention, the power absorption resistor is automatically connected and disconnected in order to obtain the electric braking function of the driving motor, so the problems of the prior art are solved. A self-propelled transport system that does not consume unnecessary power, does not require the installation of extra rails, and can always reliably suppress increases in motor terminal voltage and bogie running speed, resulting in stable running. The trolley can be easily provided.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a self-propelled trolley according to the present invention, Fig. 2 is an explanatory diagram of a transport system, and Fig. 3 is a feed i! of the transport system. It is an explanatory diagram of a system. 1...Traveling rail, 2...Self-propelled trolley, 3.4.
...Power supply rail, 5.6... Sliding electronics, 7... Operation panel, 8... Power supply, 10... Traveling motor, 11...
- Switch transistor, 12... Power absorption resistor, 16... Current detection diode, 14... Photocoupler.

Claims (1)

[Claims] 1. In a self-propelled truck equipped with a traveling electric motor that operates by switching between an electric mode and a power generation mode depending on terminal voltage and rotational speed, a current flowing into the electric motor from the power supply side is provided. A detection means for detecting the detection, a switch means for controlling on/off according to the detection output of the detection means, and a resistor for absorbing the power generated by the electric motor are provided, and the on/off of the resistor is controlled as described above. A self-propelled trolley characterized by being configured to operate using a switch means. 2. Claim 1, characterized in that the detection means includes a diode connected in series with the motor, and is configured to obtain the detection output by a forward voltage drop of the diode. A self-propelled trolley. 3. The self-propelled trolley according to claim 1, characterized in that signal transmission between the detection means and the switch means is implemented by a photocoupler.