JPS6111190Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is an automatic winching device that performs hoisting, lowering, and traversing, which are the main operations of electrical machinery for cargo handling. It is an object of the present invention to provide a temperature control device that prevents overheating, burnout, and wear of switching contacts due to frequent flow of current through them.

In general, most electric hoists and cranes have a single hoisting speed or traversing speed, and those with two or more speeds require various speed control devices and are therefore expensive. In order to improve the inconvenience of such single-speed specifications, manual low-speed operation is possible.
This allows for correct positioning in required operations such as winding up. However, during positioning using such low-speed operation, the winching operation is repeated in forward and reverse directions, which may cause overheating of the winching motor, burnout of the windings, or malfunction of the switching contacts of the circuit that controls the motor. There were problems such as wear and tear. Particularly when winching is performed frequently and for a long period of time, there is a risk that the above-mentioned opening/closing contacts may be welded due to overheating, causing a runaway accident.

The present invention was developed to improve such conventional problems, and in particular detects the temperature of the electric motor and the above-mentioned switching contacts, and changes the inching interval using a voltage-frequency converter, so that the above-mentioned temperature is always constant. It is an object of the present invention to provide a temperature control device for an automatic winching device that performs control and monitoring to ensure that the temperature is controlled and monitored.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a temperature control circuit showing an example of the temperature control circuit, 1 is an input terminal for inputting preset temperature information, and a comparator 2 is connected to this to input temperature information of the motor and switching contacts and the above set temperature. information is compared. A voltage-frequency converter 3 is connected to this comparator 2. A voltage controlled oscillator is used here which converts changes in voltage level into changes in frequency. A signal that sets the period T ₂ of the oscillation pulse is input to this. 4 is a timer to which a signal for setting the time width _T1 of the oscillation pulse is input. Reference numeral 5 designates an inching motor driven by the output of the timer 4, and the winding temperature of the motor 5 is detected by a temperature sensor 6 and fed back to the comparator 2.

FIG. 2 is a circuit diagram showing details of FIG. 1, in which the temperature sensor 6 includes a balanced circuit consisting of a thermistor 7, a voltage dividing resistor 8, a voltage dividing variable resistor 9, and an input resistor 10;
The comparator 2 consists of an operational amplifier 11 and a feedback resistor 12 that determines its amplification factor, and a variable resistor 13 that determines the temperature setting voltage input to the input terminal 1, and a variable resistor 13 that determines the temperature setting voltage input to the input terminal 1, and the setting voltage and the input resistance 15 via the resistor 14. It consists of an operational amplifier 16 to which the output voltage of the operational amplifier 11 is input via a Zener diode 18 connected to the output of the operational amplifier 16, and output voltage dividing resistors 19 and 20. Further, the voltage-frequency converter 3 includes a variable resistor 22 connected to the IC element 21 to set the initial value of the pulse period T ₂ , a resistor 31 commonly connected to the variable resistor 22 to the IO element 21, and a base. A transistor 3 is connected to the cathode of the Zener diode 18 via a resistor 32, and causes current to flow through the resistor 31 when turned on.
Consists of 0. Regarding the resistor 31, when the Zener diode 18 is turned on, current flows through the resistor 31 through the transistor 30, so that the period _T2 of the pulse becomes a value determined by the resistor 31. Further, the timer 4 consists of an IC element 23 connected to a variable resistor 24 that determines the pulse width _T1 . Furthermore, relays 25 and 26 for controlling winching operation are connected to the output side of this IC element 23 via switches 27 and 28. It is assumed that relays 25 and 26 control winching for hoisting and lowering, respectively.

Next, the operation of the temperature control circuit having such a configuration will be described.

The temperature of the motor is determined by the thermistor 17 of the temperature sensor 6.
A voltage output proportional to the temperature change is applied to the operational amplifier 16. Also,
This voltage output is applied to the operational amplifier 16 together with the voltage set by the variable resistor 13 for voltage comparison, and the comparison difference output voltage is input to the IC element 21 forming the voltage controlled oscillator of the voltage-frequency converter 3. Here, the pulse output shown in FIG. 3 is obtained in response to voltage changes. The period T ₂ of this pulse is adjusted by a variable resistor 22. This pulse output is also applied to the IC element 23 of the timer 4, and its pulse width is adjusted by the variable resistor 24. When the switch 27 or 28 is closed, the relay 25 or 26 is activated.
T ₁ and cycle T ₂ , and winching is performed while supplying voltage to the motor at this timing.
That is, the temperature of the electric motor is controlled to be kept constant using this timing.

Here, since the time change in temperature with respect to the input voltage of the voltage-frequency converter is considered to be a first-order lag, the Laplace transformed block diagram of the system in FIG. 1 is as shown in FIG. 4.

According to this, the output temperature coefficient T ₀ has a relationship with the input set temperature T _S as follows: T ₀ =A/S+τ+AKT _S (1). Here, S is a variable involved in temperature change, and A, τ, and K are constants determined by the system. Here, since the steady-state value of T ₀ is S = 0, T ₀₀ = A/τ + AKT _S ......(2) Therefore, in order to make T ₀ the target value, T _S should be changed to T _S = (K+τ/A)T ₀ ......(3) It is necessary to do so. FIG. 5 shows the relationship between the output ΔT of the comparator 2 and T ₀ , and the winching period T ₂ is inversely proportional to this output ΔT.
The steady value T ₀₀ of T ₀ is a function of constants A and K, and when the pulse width T ₁ and period T ₂ are changed, the steady value
T ₀₀ also changes. By the way, as shown in FIG. 2, the comparator 2 has a limiter function by the Zener diode 18 connected to the output side of the operational amplifier 16, so as shown in FIG. 6, T ₀ becomes T ₀
When it is smaller than _Z , the comparator output ΔT is maintained at a constant value T _Z . and zener diode 1
8 is on, the transistor 30 is on, and current flows through the resistor 31, and the pulse period _T2 from the voltage-frequency converter 3 is
The temperature of the motor increases because it reaches a constant short value determined by this resistor 31. Here, assuming that the steady-state value when the transistor 30 is on is T _0T , when △T>T _Z , the transistor 30 is turned on and the temperature of the motor tends to rise toward T _0T , and △T<T _Z When , the transistor 30 is turned off, so the temperature of the motor tends to decrease toward T ₀₀ . Therefore, since the temperature of the motor is maintained at the temperature T _0Z determined by the Zener voltage of the Zener diode 18, constant temperature characteristics can be obtained. That is, the temperature of the motor can be maintained below a certain value. At this time, it is necessary that T _0T >T _0Z >T ₀₀ =A/τ+AKT _S (5), and the winching period T ₂ remains constant until the temperature reaches T _0Z . In this way, by limiting the upper limit of the output △T of comparator 2, △T
The pulse period is set to a value corresponding to △T until △T reaches its upper limit, and the pulse period is set to a constant value after △T reaches its upper limit, thereby limiting the increase in motor temperature. , can prevent winding burnout. Furthermore, by utilizing the above technology in the switching device of the inching control circuit, overheating of the switching contacts can be prevented, and runaway accidents due to contact welding can also be prevented. The above-mentioned switches 27 and 28 can be connected to other relay circuits and timer circuits, and the operating modes of these switches can be arbitrarily selected to perform automatic winching and manual constant speed operation according to the above-mentioned timings. Winch operation can be performed arbitrarily.

In summary, according to the present invention, the temperature of the switching contacts of the electric motor and its control circuit is detected, the winching interval is changed by a voltage-frequency converter, and the temperature is controlled to a constant value. , it is possible to prevent overheating and burnout of the electric motor and the switching contacts, and it is possible to extend their lifespan and reduce maintenance costs. In particular, since the welding of the opening/closing contacts is completely avoided, runaway accidents of motors and control circuits caused by welding that have occurred in the past are prevented, and safety is significantly improved, which has various practical disadvantages.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the temperature control circuit according to the present invention, Fig. 2 is a specific circuit diagram thereof, Fig. 3 is a waveform diagram of the timer output, and Fig. 4 is a block diagram obtained by Laplace transform of the system in Fig. 1. Diagram, Figure 5 is the 4th
A graph showing the relationship between the timer output △T and the temperature output T ₀ of the system shown in the figure. Figure 6 is also a graph showing the timer output △
It is a graph when temperature control is performed with T constant. 1...Reference temperature setting input terminal, 2...Comparator,
3... Voltage-frequency converter, 4... Timer,
5...Motor, 6...Temperature sensor, 18...Output control means.

Claims (1)

[Scope of utility model registration request] Temperature detection means for a motor or its start-up switching contact, and a temperature comparison means that compares the detected temperature output and a reference set temperature input, extracts the deviation thereof, and has a limiter function that limits the upper limit of the deviation. a voltage-frequency conversion means for obtaining a pulse with a frequency corresponding to the output signal from the temperature comparison means; a timer for setting the pulse width of the pulse from the voltage-frequency conversion means; 1. A temperature control device for an automatic winching device, comprising: output control means for controlling winching using pulses that are output and whose pulse width is set by the timer.