JPH0765571B2 - In-vehicle refrigerator overcurrent protection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an overcurrent protection device for an on-vehicle refrigerator, and in particular, to drive power generation for supplying power to a vibration type compressor when an overcurrent flows. The present invention relates to an overcurrent protection device for a vehicle-mounted refrigerator, which protects the compressor drive control device by stopping the oscillation of the section.

(Prior Art) There is a refrigerator in which a gaseous refrigerant is compressed and liquefied by using an oscillating compressor, and cooling is performed by using heat of vaporization when the liquefied refrigerant is vaporized. Conventionally, as a vibration type compressor drive control system used in the refrigerator, there is one shown in FIG. 4, for example. In FIG. 4, the oscillating compressor 5 switches the switching transistors TR ₁ and TR ₂ to the conductive state alternately to direct the DC power supply V to the windings on the primary side of the transformer 4 having different polarities. The voltage is applied alternately and the drive is controlled so that the resonance state, that is, the maximum efficiency is obtained. At this time, the switching transistors TR ₁ and TR ₂ are alternately switched between the conducting state and the non-conducting state in the manner shown by the current waveform in FIG. 5, for example, so that they match the resonance frequency of the vibration type compressor 5. The switching frequency is controlled. More specifically, to switch the Figure 5 diagram in the collector current "I _C", the base current "I _B" is alternately supplied from the drive circuit 1-3 to the base of the transistor TR _1, TR ₂ for switching It That is, the base current "I _B" current amplification factor "h _FE"
By supplying a so-called trapezoidal waveform as shown in the figure or shown as the doubled current waveform, by applying the condition of I _C ≧ H _FE × I _{B at the} positions such as points P ₁ to P _{3 in} the figure, switching The transistors TR ₁ and TR ₂ are alternately switched between a conductive state and a non-conductive state to obtain a driving power supply with a desired frequency.
Conventionally, as described previously, the driving power source that matches the resonance frequency of the vibration type compressor 5 is used to drive the compressor 5.

In this way, as the overcurrent protection device for the on-vehicle refrigerator that drives the compressor 5 by using the drive power source that matches the resonance frequency of the vibration type compressor 5, the fuse or breaker is used in the main circuit, and the main circuit is disconnected. By doing so, the refrigerator for the vehicle was protected.

(Problems to be solved by the invention) If the main circuit is cut by a fuse or breaker,
Due to its slow response time, when a mechanical system, such as a compressor, fails, an overcurrent flows, and the drive power source for driving the vibration type compressor is also prone to chain-induced damage. Not only the parts, but also the drive power generation part of the electric system had to be replaced in its entirety. Also, in the case of overcurrent protection using fuses and breakers, it is necessary to replace or restore them, so it is necessary to consider the mounting position such as mounting the fuse or breaker at a position where it is easy to operate from the outside, It had the drawback of being routed in a complicated manner.

The present invention aims to solve the above-mentioned drawbacks, and compresses the drive of the vibration type compressor based on the temperatures corresponding to the saturated vapor pressures of the refrigerant on the inlet side and the outlet side of the compressor, respectively. Combined with the development of technology that can control the compressor, an electronic circuit that responds quickly when an overcurrent flows stops the oscillation of the drive power generator that supplies power to the vibration type compressor. The purpose of the present invention is to provide an overcurrent protection device for a vehicle-mounted refrigerator which operates as double protection at a position where fuses, breakers, etc. do not have to be taken into consideration in its mounting position.

(Means for Solving the Problems) Therefore, the overcurrent protection device for a vehicle-mounted refrigerator according to the present invention uses the desired frequency corresponding to the operation of the vibration type compressor in the refrigerator to perform the vibration type compression. In a compressor drive control device for driving and controlling a compressor, a temperature corresponding to a saturated vapor pressure of a refrigerant sucked by the compressor in an evaporator used in the refrigerator and the compressor in a condenser used in the refrigerator. A drive power source generating unit for generating a drive voltage of the desired frequency based on both signals of the temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the drive power source generating unit is generated. A compressor drive control device for driving the compressor by using the drive voltage, wherein a current detection element for detecting a load current of the drive power source generation unit is provided. And when a predetermined overcurrent flows through the current detecting element,
A switching stop circuit for stopping the operation of the switching element provided in the drive power generation section is provided, and when the overcurrent flows in the current detection element, the oscillation of the drive power generation section is stopped, and the compressor drive control device is provided. It is characterized by being protected.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of an overcurrent protection device for an on-vehicle refrigerator according to the present invention, FIG. 2 shows the schematic configuration of an on-vehicle refrigerator in which the present invention is used, and FIG. 3 shows the present invention. 1 shows a circuit configuration of an embodiment of a vehicle-mounted refrigerator.

Before describing the overcurrent protection device for a vehicle-mounted refrigerator according to the present invention, an outline of a vehicle-mounted refrigerator in which the present invention is used and a circuit configuration in which the present invention is used will be described.

In FIG. 2, 1 is a control circuit, 1-1 is a temperature detector, 1-2
Is a calculation unit, 1-3 is a drive circuit, 2 and 3 are temperature detectors, 4 is a transformer, 5 is a compressor, 6 is a condenser, 7 is a pressure reducer, 8 is a refrigerator, 8-1
Represents an evaporator.

In the figure, the control circuit 1 is composed of a temperature detection unit 1-1, a calculation unit 1-2, and a drive circuit 1-3, and detects the temperature corresponding to the saturated vapor pressure of the refrigerant sucked by the compressor 5. The compressor 5 resonates based on the respective signals from the temperature detector (T _d ) 3 that detects the temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor (T _s ) 2 and the compressor 5. It is for supplying a drive signal having a frequency that is driven in a state. The temperature detection section 1-1
It can be considered that the temperature detected at is substantially the temperature corresponding to the pressure of the refrigerant on the suction side and the pressure of the refrigerant on the discharge side.

The oscillating compressor 5, which is supplied with the driving power generated by the driving signal supplied from the control circuit 1, compresses the refrigerant to supply a mixture of gas and liquid to the condenser 6. It radiates heat to liquefy. Then, the liquefied refrigerant is vaporized by the evaporator 8-1 provided in the refrigerator 8 via the pressure reducer 7 to remove heat of vaporization and cool the refrigerator 8. The refrigerant that has deprived the heat of vaporization is compressed again by the compressor 5. By repeating the closed cycle as described above, the evaporator 8-
The heat taken from 1 is released from the condenser 6 in the form of heat. The operation of the control circuit 1 will be described in detail below.

In the figure, a temperature detector 1-1 is for converting the signals detected by the temperature detectors (for example, thermistors) 2 and 3 into predetermined electric signals.

In the figure, the calculation unit 1-2 determines that the compressor 5 is in the resonance state based on the "temperature corresponding to the suction pressure" and the "temperature corresponding to the discharge pressure" converted into the electric signal form by the temperature detection unit 1-1. It is for generating a voltage corresponding to a driving frequency. Then, the drive circuit 1-3 is the arithmetic unit 1-
A drive signal having a frequency corresponding to the voltage supplied from ₂ is supplied to the transistors TR ₁ and TR ₂ in the figure so that the primary side winding of the transformer 4 is in the form of a rectangular wave from the illustrated DC power supply V _cc. In addition, the electric current is supplied to the windings having different polarities in an alternating manner. 2 of the transformer 4
The AC voltage obtained from the secondary winding is supplied to the compressor 5,
The compressor 5 is always driven in a resonating state, that is, driven with maximum efficiency. In the case of the present invention, switching is performed by a signal from the outside to control the drive circuit as described above, and the vibration type compression flowing in the form corresponding to the current I _C described with reference to FIG. Since the machine current is obtained, it becomes easy to detect the overcurrent by checking the average current value supplied to the drive circuit.

In an embodiment of an in-vehicle refrigerator in which the present invention shown in FIG. 3 is used, reference numerals 1-1, 1-2, _1-3 , 2 to 5, TR ₁ , T
Since R ₂ is the same as that in FIG. 2, its explanation is omitted.

Reference numeral 9 is a thermo device, 10 is an evaporator temperature comparator, 11 is a transformer, 12 is an AC detector, 13 is a surge absorption circuit, 14 is an overcurrent detection circuit, 15 and 16 are relays, 17 and 18 are AND circuits, 19 , 20
Is an OR circuit, 21 is an inverter, 22 and 23 are diodes, 24 is a volume, and 25 is a shunt.

The thermo device 9 is for setting the indoor temperature of the refrigerator, and the volume 24 provided in the thermo device 9 is used.
The room temperature of the refrigerator can be changed according to the setting.

The evaporator temperature comparator 10 electrically compares the signal of the indoor temperature of the refrigerator set by the volume 24 with the signal from the temperature detector 2 which detects the temperature of the evaporator 8-1, and the thermostat 9 The set temperature on the side is the evaporator 8
When the temperature becomes higher than the -1 side temperature, a logic "L" is output. The output of the logic "L" is an OR circuit having a negative input terminal.
It becomes a stop signal to the drive circuit 1-3 via 20 and turns off the contact of the relay 16 via the AND circuit 17, and the direct current to the transformer 4, that is, the transistors TR ₁ and TR ₂ via the relay 16. Turn off the power supply.

The transformer 11 is for lowering the voltage of the commercial power source for detection when the vehicle-mounted refrigerator is connected to the commercial power source. The voltage of the commercial power source is supplied to the AC detector 12 connected to the secondary side. To descend and supply.

The AC detector 12 detects whether or not a commercial power source is input, and outputs a logic "H" when the commercial power source is input. The logic "H" serves as a stop signal to the drive circuit 1-3 via the OR circuit 20, and turns off the contact of the relay 16 via the AND circuit 17 to cause the relay 16 to turn off.
The supply of the DC power to the transformer 4, that is, the transistors TR ₁ and TR ₂ is cut off via the. Further, the contact of the relay 15 is turned on via the AND circuit 18, and the AC power is supplied to the transformer 4 via the relay 15.

The surge absorbing circuit 13 absorbs the surge voltage of the input DC power supply and supplies the DC power to the drive circuit 1-3, and when the voltage of the input DC power supply is higher than a predetermined voltage, the logic “H Is output. The logic “H” is a transistor for the drive circuit 1-3 through the OR circuit 19.
The strokes of the compressor 5 are controlled by controlling the outputs of TR ₁ and TR ₂ .

The overcurrent detection circuit 14 includes a shunt 25 and a transistor TR.
_1, which detects an overcurrent flowing through the TR _2, overcurrent when the detection circuit 14 detects the overcurrent, outputs the off-latch signal to the drive circuit 1-3 for stopping the operation of the transistor TR _1, TR ₂ Is output to prevent damage to the transistors TR ₁ , TR _2, etc. The overcurrent detection circuit 14 will be described in more detail.

Next, the present invention will be described in more detail with reference to FIG.

In FIG. 1, reference numerals 4,5, TR ₁ and TR ₂ indicate the already described second
Corresponding to the one in the figure, reference numeral 41 is a drive power source generating unit,
Is an oscillator, 43 is a switching stop circuit, 44 is a comparator, 45 and 46 are AND circuits, 47 is an inverter, 48 is a reference power supply, 4
9 is a shunt resistance and 50 is a breaker.

The oscillator 42 corresponds to the control circuit 1 in FIG. _2, and a switching stop circuit 43 is connected between the output Q of the oscillator 42 and the switching transistors TR ₁ and TR ₂ . The switching stop circuit 43 is a comparator 44, an inverter 47 and an AND circuit 45 for comparing the voltage of the reference power source 48 with the voltage generated across the shunt resistor 49 as a current detecting element.
It consists of 46.

Now for some reason the load current, ie transistor TR
_{If the} current flowing through ₁ or TR ₂ increases, the shunt resistance 49
The voltage generated at both ends of the voltage rises and becomes higher than the voltage of the reference power supply 48. When the voltage generated across the shunt resistor 49 becomes higher than the voltage of the reference power source 48, the comparator 44 outputs a stop signal of logic "H". The logic "H" of the stop signal is inverted by the inverter 47, and the logic "L" is input to the AND circuits 45 and 46. Thus AND circuit 45 and 46 are both output logic "L" to stop the operation of the transistor TR _1, TR ₂ of the switching. That is, the driving power is not supplied to the compressor 5, and the compressor 5 stops.

A current transformer can be used as the current detecting element instead of the shunt resistor 49. When using a current transformer, it goes without saying that the voltage generated on the secondary side of the current transformer is compared with the voltage of the reference power supply 48.

Further, a fuse in place of the illustrated resistor 49 may be used as the current detecting element. The resistance of the fuse itself is used as a detection element, and the voltage generated across the fuse is used as a reference power source.
Compare with the voltage of 48. In this case, when the current flowing through the fuse becomes large, its resistance value rises due to the temperature rise, the voltage generated across the fuse becomes high, and the operation of overcurrent detection becomes faster. And when using a fuse,
Even if the switching stop circuit 43 does not operate for some reason, the fuse itself blows, and the breaker 50 is not required.

(Effects of the Invention) As described above, according to the present invention, since the electronic protection device having a high response speed is added, the induced breakdown of the drive power source generating unit for driving the vibration type compressor is reduced, and the defective component is damaged. Only need to replace.

By adjusting the operating current of the electronic protection circuit to the specifications, it is possible to make the breaker, fuse, etc. as double protection a value with a margin, and the chances of operating these breakers, fuses, etc. are reduced. There is no need to consider a mounting position that is easy to replace.

When a fuse is used as the current detection element,
Works as a double protection device without separately preparing a breaker.

[Brief description of drawings]

FIG. 1 shows the configuration of an overcurrent protection device for an on-vehicle refrigerator according to the present invention, FIG. 2 shows the schematic configuration of an on-vehicle refrigerator in which the present invention is used, and FIG. 3 shows the present invention. FIG. 4 is an explanatory diagram for explaining a conventional compressor drive control system, and FIG. 5 is an operation explanatory diagram for explaining the operation of the compressor drive control system shown in FIG. Shows. In the figure, 1 is a control circuit, 1-1 is a temperature detection unit, 1-2 is a calculation unit, 1
-3 is a drive circuit, 2 and 3 are temperature detectors, 4 is a transformer, 5 is a compressor, 6 is a condenser, 7 is a decompressor, 8 is a refrigerator, 8-1 is an evaporator, and 41 is a drive power generation unit. Reference numeral 42 is an oscillator, 43 is a switching stop circuit, 44 is a comparator, 45 and 46 are AND circuits, 47 is an inverter, 48 is a reference power supply, and 49 is a shunt resistor.

Front page continued (72) Inventor Naoya Kawakami 3 Hayakawa, Nitta-cho, Nitta-gun, Gunma Prefecture, Hayakawa, Nitta factory, Sawafuji Electric Co., Ltd. (72) Yoshiaki Fujisawa, Nitta-cho, Nitta-cho, Gunma, Hayakawa No. 3 Sawafuji Electric Co., Ltd. Nitta Factory (72) Inventor Noriyoshi Yamada No. 3 Niigata-cho, Nitta County, Gunma Hayakawa, Hayakawa No. 3 Sawafuji Electric Co., Ltd. Nitta Factory (56) Reference JP-A-58-65981 (JP, A) JP-A-58-217786 (JP, A)

Claims (1)

[Claims] 1. An evaporator used in the refrigerator in a compressor drive control device for driving and controlling the vibration type compressor using a desired frequency corresponding to the operation of the vibration type compressor in the refrigerator. Signal of both the temperature corresponding to the saturated vapor pressure of the refrigerant sucked by the compressor and the temperature corresponding to the saturated vapor pressure of the refrigerant compressed and discharged by the compressor in the condenser used in the refrigerator Based on the above, a compressor drive control device comprising a drive power source generating unit for generating a drive voltage of the desired frequency, and driving the compressor using the drive voltage generated by the drive power source generating unit. When a current detection element for detecting the load current of the drive power source generation unit is provided and a predetermined overcurrent flows through the current detection element,
A switching stop circuit for stopping the operation of the switching element provided in the drive power generation section is provided, and when the overcurrent flows in the current detection element, the oscillation of the drive power generation section is stopped, and the compressor drive control device is provided. An overcurrent protection device for an in-vehicle refrigerator, which is characterized by being protected.