JPS6145139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an input voltage control circuit for a cooling device, particularly in a cooling device equipped with a compressor driven by supply of electrical energy, when the ambient temperature of the cooling device is extremely low. The present invention relates to an input voltage control circuit for a cooling device that prevents the compressor from being undesirably destroyed and also prevents the windings of the compressor from being undesirably burnt out when the ambient temperature is high.

As a cooling device, for example, a compressor driven by receiving electric energy supply, a condenser to which refrigerant compressed and outputted from the compressor is guided, a capillary, a tube, the capillary, provided downstream of the condenser, Some are known that are equipped with an evaporator installed downstream of the tube. However, this type of cooling device
As described in the specification of the patent application No. 75142, the vibration stroke of the compressor increases undesirably when the cooling device is placed under an extremely low ambient temperature, resulting in damage to the valve chamber. It has the disadvantage of being difficult to store.

It has also been found that when this type of cooling device is operated at high ambient temperatures, a phenomenon occurs in which the windings of the compressor are undesirably burnt out.

The present invention aims to solve the above points,
The purpose is to prevent the valve chamber from being undesirably damaged under extremely low temperatures, and to automatically check the ambient temperature periodically and automatically recover in case the ambient temperature returns to normal temperature. There is. Another purpose is to prevent the winding from being undesirably burnt out at high temperatures. The present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram for explaining the principle of the present invention, and FIG. 2 is an exemplary configuration conceptually representing the present invention.
FIG. 3 shows the configuration of an embodiment of the input voltage control circuit in FIG. 2. In FIG.

FIG. 1 shows an explanatory diagram illustrating the limits of the electrical energy that should be supplied to the cooling device, that is, the limits of the input voltage, with respect to the ambient temperature of the cooling device. In the diagram, line A
is an example of the ambient temperature/limit input voltage characteristic, and represents the limit input voltage at which the valve chamber of the compressor is not affected by the ambient temperature. Line B is an example of the limit ambient temperature characteristic on the low temperature side, and line C is the high temperature limit input voltage. This shows an example of side limit ambient temperature characteristics.

In the case of the present invention, (1) When the ambient temperature is above the indicated temperature T ₀ and below the indicated temperature T ₁ , the input voltage increases in proportion to the temperature rise as shown by the indicated line D ₁ . Given the characteristics, (2) the ambient temperature is line B
That is, when the temperature falls below _T0 , the input voltage is reduced to zero, that is, the supply of electrical energy is stopped, as shown by line _D2 , and (3) after the ambient temperature exceeds line C, that is, temperature T1, the input voltage is reduced to zero, as shown by line _D3 , when the ambient temperature exceeds temperature _T1 . As shown, the input voltage is maintained at a predetermined level. Also, in the state of (2) above, the ambient temperature is periodically checked to enable automatic recovery. That is, when the ambient temperature is extremely low, the supply of electrical energy to the compressor is stopped to prevent undesired loss of the valve chamber, and when the ambient temperature is high, the input voltage to the compressor is reduced. Maintained at a predetermined level to prevent undesired burnout of the compressor windings.

FIG. 2 shows the overall configuration of an embodiment of the present invention. In the figure, 1 is an input voltage control circuit that controls the input voltage to the compressor according to the ambient temperature as described above in FIG. 1, and 2 is an inverter that controls the DC output power of the input voltage control circuit 1. 3 represents a compressor driven by the AC output power from the inverter 2, which is converted into AC power.

FIG. 3 shows the configuration of an embodiment of the input voltage control circuit 1. In the figure, reference numeral 4 denotes a switching element, which is composed of, for example, a transistor _TR1 and an inverter 2.
(Fig. 2), which controls the power supply to
6 is a control circuit that controls the switching element 4; 6 is a temperature detection circuit that detects the ambient temperature and controls the control circuit 5 based on the detection result; 7 is a voltage detection circuit that controls the input of the inverter 2; 8 is an OFF detection circuit that detects the transition of the switching element 4 from the ON state to the OFF state, and 9 is a recovery circuit that controls the OFF state based on the detection result. Each shows a circuit that controls the voltage detection circuit 7 based on a detection signal from the detection circuit 8.

In FIG. 3, the thermistor TH in the temperature detection circuit 6 is constructed of a negative characteristic thermistor having a resistance value corresponding to the ambient temperature. The Zena diode ZD ₂ in the temperature detection circuit 6 is turned off when the ambient temperature is below the temperature T 1 shown in FIG. ₁ , and turned on when the ambient temperature is above the temperature T ₁ . The transistor TR ₆ in the voltage detection circuit 7 is turned off when the ambient temperature is above the temperature T ₀ shown in FIG.
It is turned on when T is below ₀ .

[] When the ambient temperature is at normal temperature, that is, between the temperature T ₀ shown in Figure 1 and the temperature T ₁ shown in Figure 1,
The amount of conduction of transistor TR ₅ is negative characteristic thermistor
Due to TH, it tends to decrease as the ambient temperature increases. Therefore, the transistor of the control circuit 5
The amount of conduction in TR ₄ decreases as the ambient temperature increases, the amount of conduction in transistor TR ₃ increases as the ambient temperature increases, and the amount of conduction in transistor TR ₂ decreases as the ambient temperature increases. As a result, the amount of conduction of transistor _TR1 increases as the ambient temperature increases. Therefore, when the ambient temperature is normal, the output voltage of the input voltage control circuit, that is, the input voltage of the inverter 2 has a characteristic as shown by the line _D1 in FIG.

[] When the ambient temperature is high, that is, above the temperature T ₁ shown in Figure 1, the resistance value of the negative characteristic thermistor TH is small, and therefore the voltage across the terminals of the resistor R ₂ exceeds the zena voltage of the zena diode ZD ₂ . Beyond Zena
Diode ZD ₂ is turned on. Therefore, the base-emitter voltage of the transistor _TR5 is maintained at a predetermined level by the Zener diode _ZD1 and the Zener diode _ZD2 . In other words, the amount of conduction of transistor TR ₅ is maintained at a predetermined level,
As a result, the amount of conduction of transistor _TR1 is maintained at a predetermined level. Therefore, when the ambient temperature is high, the input voltage of inverter 2 will be the line shown in Figure 1.
It has characteristics like D ₃ .

[] When the ambient temperature is in a low state, that is _, below the temperature _T0 shown in FIG. The potential at the point β increases, causing the transistor _TR6 to transition from the off state to the on state.
At the same time as this transistor TR ₆ is turned on, the transistor TR ₄ of the control circuit 5 is completely turned on, the transistor TR ₃ is turned off, the transistor TR ₂ is turned off, and as a result, the transistor TR ₁ is turned off. Therefore, when the ambient temperature is low, the input voltage of the inverter 2 has a characteristic as shown by the line _D2 in FIG. When the transistor _TR1 is turned off, a voltage is instantaneously generated in the resistor _R5 of the on-detection circuit 8, and the generated voltage causes the thyristor PUT to temporarily operate at a predetermined period based on the circuit time constant including the capacitor C. automatically turned on. This thyristor
During the period when PUT is in the on state, the transistor TR ₇ of the recovery circuit 9 is in the on state, and the transistor
TR ₆ is shorted and turned off. Therefore, the transistor TR ₄ of the control circuit 5 is turned off, and as a result, the transistor TR ₁ is turned on. When this transistor TR ₁ is turned on, a current flows through the series circuit of the resistor R ₂ and the negative characteristic thermistor TH, and if the ambient temperature is higher than the temperature T ₀ shown in Figure 1, the transistor TR ₅ is turned on.
is conductive, and the amount of conduction of the transistor _TR1 is determined in accordance with the amount of conduction of the transistor _TR5 . On the other hand, if the ambient temperature is still below the temperature T ₀ , the transistor TR ₆ is turned on again and the transistor TR ₁ is turned off again. Similarly to the above, when the transistor TR ₁ is turned off, the transistor TR ₆ is turned off based on the voltage generated across the resistor R ₅ , the transistor TR ₄ is turned on, the transistor TR ₁ is turned on, and the negative characteristic thermistor TH is turned on. A current flows through. That is, a check of the ambient temperature is performed periodically. That is, if the ambient temperature at the time when current flows through the negative characteristic thermistor TH is above the temperature T ₀ , the transistor TR ₁ becomes conductive and power is supplied to the inverter 2, while the ambient temperature is still at the temperature T _{0 .} If it is below, the transistor _TR1 is turned off. Thereafter, similar operations are repeated. In other words, when the ambient temperature becomes low, power supply to the inverter 2 is stopped. Then, the ambient temperature is detected at a predetermined cycle, and when the ambient temperature returns to normal temperature, the power supply to the inverter 2 is restarted, and on the other hand, when the ambient temperature is still low, the power supply to the inverter 2 is resumed. continues to stop.

As explained above, according to the present invention, when the cooling device is placed in a low temperature state, the power supply to the compressor can be stopped to prevent the valve chamber from being undesirably destroyed, and the cooling device can be When exposed to high temperatures, the power supply to the compressor can be maintained at a predetermined level to prevent burnout due to increased temperature of the windings. Further, when the cooling device is placed in a low temperature state, power supply to the compressor can be automatically restarted when the ambient temperature returns to normal temperature.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the principle of the present invention, FIG. 2 is an embodiment conceptually representing the present invention, and FIG.
The figure shows one embodiment of an input voltage control circuit according to the invention. In the figure, 1 is an input voltage control circuit, 2 is an inverter, 3 is a compressor, 4 is a switching element, 5 is a control circuit, 6 is a temperature detection circuit, 7 is a voltage detection circuit,
8 represents an off detection circuit, 9 represents a recovery circuit, and TH represents a thermistor.

Claims (1)

[Claims] 1. In a cooling device equipped with a vibratory compressor and an inverter that converts DC power into AC power and supplies the AC power to the vibratory compressor, an input voltage control circuit is provided on the input side of the inverter to control the input voltage. The control circuit includes a switching element inserted in series with a power supply circuit for the inverter;
a control circuit for controlling the switching element; and a control circuit for detecting the ambient temperature of the cooling device, maintaining the amount of conduction of the switching element at a predetermined level while the ambient temperature is in a high temperature state, and maintaining the conduction amount of the switching element at a predetermined level when the ambient temperature is in a low temperature state. a temperature detection circuit that controls the control circuit including an operation of turning off conduction of the switching element; a voltage detection circuit that detects the input voltage level of the inverter and controls the control circuit based on the detection result; an OFF detection circuit that detects a transition to OFF and issues an output signal after a predetermined time has elapsed, and the switching element that controls the voltage detection circuit to be turned OFF based on the output signal from the OFF detection circuit. 1. An input voltage control circuit for a cooling device, comprising a return circuit for restoring.