JPS62103492A - Device for protecting car-loaded refrigerator from overcurrent - Google Patents

Abstract

PURPOSE:To prevent the failure of a driving power source generating part by stopping the action of a switching element which is provided on said driving power source generating part, when an overcurrent has flowed in a current detecting element for detecting the load current of said driving power source generating part. CONSTITUTION:When currents which flow in switching transistors TR1, TR2 are increased, voltages generated on both ends of a shunt resistor 49 becomes higher than the voltage of a reference power source 48. Thereby, a comparator 44 outputs a logic H stopping signal, which in turn, is inverted by an inverter 47 and inputted into AND circuits 45, 46. Therefore, both the outputs of the AND circuits 45, 46 become a logic L signal, stopping the action of the transistors TR1, TR2, while stopping the supply of driving power source to a compressor 5.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is directed to an overcurrent protection device for a vehicle-mounted refrigerator. The oscillation of the unit is stopped.

The present invention relates to an overcurrent protection device for a vehicle-mounted refrigerator that protects a compressor drive control device.

(Prior Art) There is a refrigerator that compresses and liquefies a gaseous refrigerant using a vibrating compressor and performs cooling etc. using the heat of vaporization when the liquefied refrigerant evaporates. Conventional.

As an example of a vibrating compressor drive control system used in the refrigerator, there is a system as shown in FIG. In FIG. 4, the vibrating compressor 5 includes switching transistors TR,...
, TR2 are alternately turned on, DC power (2) is alternately applied to the primary windings of the transformer 4 having different polarities, and the drive is controlled so that a resonance state, that is, maximum efficiency is obtained. At this time, the switching transistor TR.

TR2 is alternately switched between a conductive state and a non-conductive state in a manner such as the current waveform shown in FIG. 5, and the switching frequency is controlled to match the resonant frequency of the vibrating compressor 5. More specifically, the pace current "Ill" is alternately supplied from the drive circuit 1-3 to the bases of the switching transistors TR, TR2 so that the collector current "IC" in FIG. 5 is switched. That is, by supplying a so-called trapezoidal waveform as shown in the figures (■ to ■) as a current waveform in which the base current "IB" is multiplied by the current amplification factor "hFE", the points P to P3 in the middle of Fig. 9 are supplied.
By applying the conditions (1), ≧hFEXII+ at positions such as (2), the switching transistors TRI and TR are alternately switched into a conductive state and a non-conductive state, thereby obtaining a driving power source of a desired frequency. Conventionally, as explained above, the compressor 5 has been driven using a drive power source that matches the resonant frequency of the vibrating compressor 5.

In this way, as an overcurrent protection device for a vehicle refrigerator that drives the compressor 5 using a drive power source that matches the resonant frequency of the vibrating compressor 5, a fuse or breaker is used in the main circuit to disconnect the main circuit. By doing so, the in-vehicle refrigerator was protected.

(Problem to be solved by the invention) If the main circuit is cut off with a fuse or breaker, etc.
Because of the slow response time, when a mechanical system such as a compressor breaks down, an overcurrent will flow, and the drive power supply that drives the vibrating compressor will also be destroyed in a chain reaction. Not only the parts, but also the drive power generation section for the electrical system had to be replaced in its entirety. In addition, with overcurrent protection using fuses and breakers, they must be replaced or restored, so the location must be considered when installing the fuse or breaker in a location that is easy to operate from the outside. The disadvantage was that the lines were routed in a complicated manner.

The present invention aims to solve the above-mentioned drawbacks, and uses an electronic circuit that responds quickly when an overcurrent flows to stop the oscillation of the drive power generator that supplies power to the vibrating compressor. Another object of the present invention is to provide an overcurrent protection device for an on-vehicle refrigerator that does not require consideration of the installation location of fuses, breakers, etc., and that operates as dual protection.

(Means for Solving the Problems) Therefore, the overcurrent protection device for an on-vehicle refrigerator of the present invention is a compressor drive control device that controls the drive of a vibrating compressor using a predetermined frequency corresponding to the load. , equipped with a driving power source light/generating part that generates a driving power source of a predetermined frequency,
A compressor drive control device that drives the compressor using the drive power generated by the drive power generation unit, the compressor drive control device including a current detection element for detecting a load current of the drive power generation unit, and A switching stop circuit is provided that stops the operation of the switching element provided in the drive power generation section when a predetermined overcurrent flows through the element, and when an overcurrent flows through the current detection element, the drive power is generated. This feature is characterized in that the oscillation of the compressor is stopped and the compressor drive control device is protected.

(Example) The present invention will be described below with reference to the drawings.

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

Before explaining the overcurrent protection device for an on-vehicle refrigerator according to the present invention, the outline of the on-vehicle refrigerator to which the present invention is applied and the circuit configuration in which the present invention is used will be explained.

In FIG. 2, 1 is a control circuit, 1-1 is a temperature detection section,
1-2 is an arithmetic unit, and 1-3 is a drive circuit.

2.3 is a temperature detector, 4 is a transformer, and 5 is a compressor.

6 represents a condenser, 7 represents a pressure reducer, 8 represents a refrigerator, and 8-1 represents an evaporator.

In the figure, the control circuit 1 includes a temperature detection section 1-1. The refrigerant is compressed and discharged by the compressor 5 and a temperature detector (Ts) 2, which detects the temperature corresponding to the saturated vapor pressure of the refrigerant taken in by the compressor 5. for supplying a drive signal with a frequency such that the compressor 5 is driven in a resonant state based on each signal from the temperature detector (Td) 3 that detects the temperature corresponding to the saturated vapor pressure of the refrigerant. It is something. Note that the temperature detected by the temperature detection unit 1-1 may be considered to be a temperature that substantially corresponds to the pressure of the refrigerant on the suction side and the pressure of the refrigerant on the discharge side.

The vibrating compressor 5, supplied with drive power generated by the drive signal supplied from the control circuit 1, compresses the refrigerant and supplies a mixture of gas and liquid to the condenser 6. It emits heat and liquefies it. Then, the liquefied refrigerant is vaporized in an evaporator 8-1 provided in the refrigerator 8 via the pressure reducer 7, and cools the refrigerator 8 by removing the heat of vaporization. The refrigerant that has absorbed the heat of vaporization is compressed again by the compressor 5. By repeating the clost cycle as described above, the evaporator
The heat removed from the condenser 6 is released in the form of heat. The operation of the control circuit 1 will be described in detail below.

In the figure, a temperature detection section 1-1 is for converting signals detected by temperature detectors (eg, thermistors) 2 and 3 into predetermined electrical signals.

In the figure, the arithmetic unit 1-2 outputs "temperature corresponding to suction pressure" and "
This is to generate a voltage corresponding to the frequency at which the compressor 5 is driven in a resonant state based on the temperature corresponding to the discharge pressure. and.

The drive circuit 1-3 sends a drive signal of a frequency corresponding to the voltage supplied from the calculation unit 1-2 to the transistor T in the figure.
1 DC power supply V CC is supplied to the primary winding of the transformer 4 in the form of a rectangular wave in which the polarity alternately switches to the windings. It is for the purpose of The AC voltage obtained from the secondary winding of the transformer 4 is supplied to the compressor 5, and the compressor 5 is always driven in a resonant state, that is, driven at maximum efficiency.

In the configuration of an embodiment of a vehicle refrigerator in which the present invention is used, as shown in FIG. Since TR, , TRZ are the same as those shown in FIG. 2, their explanation will be omitted.

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, 15.16 is a relay, 1
7.18 is an AND circuit, 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 2 provided in the thermo device 9 is
The indoor temperature of the refrigerator is changed according to the setting No. 4.

The evaporator temperature comparator 10 uses the signal of the indoor temperature of the refrigerator set by the volume 24 and the evaporator 8-
It electrically compares the signal from the temperature detector 2 which is detecting the temperature of the evaporator 8-1, and when the set temperature on the thermo device 9 side becomes higher than the temperature on the evaporator 8-1 side, a logic rLJ is output. The output of the logic rLJ becomes a stop signal for the drive circuit 1-3 via an OR circuit 20 having a negative input terminal, and also becomes a stop signal for the drive circuit 1-3 via an AND circuit 17.
The contact of the transformer 4 is turned off through the relay 16.
．． That is, the supply of DC power to the transistors TRI and TR2 is cut off.

The transformer 11 is used to detect when the in-vehicle refrigerator is connected to a commercial power source and to drop the voltage of the commercial power source. descend and supply.

The AC detector 12 detects whether or not commercial power is input, and when commercial power is input.

Outputs logic rHJ. The logic rHJ becomes a stop signal to the drive circuits 1-3 via the OR circuit 20, turns off the contact of the relay 16 via the AND circuit 17, and connects the transformer 4. That is, transistor TR,.

Cut off the DC power supply to TR2. Further, the contact of the relay 15 is turned on via the AND circuit 18, and AC power is supplied to the transformer 4 via the relay 15.

The surge absorption circuit 13 absorbs the surge voltage of the input DC power supply and supplies the DC power to the drive circuit 1-3, and also outputs the logic rHJ when the voltage of the input DC power supply is higher than a predetermined voltage. Output. The logic rHJ is connected to the drive circuit 1-3 via an OR circuit 19 to the transistor TR.

The output of T R2 is controlled, and the stroke of the compressor 5 is controlled.

The overcurrent detection circuit 14 detects an overcurrent flowing through the transistors TR1 and TR2 together with the shunt 25. When the overcurrent detection circuit 14 detects an overcurrent, it instructs the drive circuit 1-3 to control the transistors TR, TR2. Transistor TRI outputs an output off launch signal that stops operation.

Prevent damage to TR2 etc. The overcurrent detection circuit 14 will be explained in more detail.

Next, the present invention will be explained in more detail using FIG.

In FIG. 1, reference numerals 4, 5. TR+ and TRz correspond to those already explained in FIG.
7 represents an inverter, 48 a reference power source, 49 a shunt resistor, and 50 a breaker.

The oscillator 42 corresponds to the control circuit 1 in FIG.
2 output Q, Q and switching transistor T
A switching stop circuit 43 is connected between R+ and T'Rz.
is connected. The switching stop circuit 43 includes a comparator 4 that compares the voltage of a reference power source 48 and the voltage generated across a shunt resistor 49 as a current detection element.
4. It consists of an inverter 47 and AND circuits 45 and 46.

Now, for some reason, the load current, that is, the transistor T
When the current flowing through R or TR2 increases, the voltage generated across both O and i of the shunt resistor 49 increases 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 supply 48,
Comparator 44 outputs a logic r HJ stop signal. The logic rHJ of the stop signal is inverted by the inverter 47, and the logic "L" is input to the AND circuits 45 and 46. Therefore, the outputs of both the AND circuits 45 and 46 become logic "L", and the switching transistors TR.

Stop the operation of TR2. That is, the drive power to the compressor 5 is no longer supplied, and the compressor 5 is stopped.

As a current detection element, the shunt resistor 49 is replaced with a current detection element.
A transformer can also be used. When a current transformer is used, 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 may be used instead of the resistor 49 shown in the drawing as the current detection element. Using the fuse's own resistance bone as a sensing element, the voltage developed across the fuse is compared to the voltage of the reference power supply 48.

In this case, when the current flowing through the fuse increases, its resistance value increases due to temperature rise, and the voltage generated across the fuse increases, making the overcurrent detection operation faster. When a fuse is used, there is an advantage that 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 explained above, according to the present invention, since an electronic protection device with a fast response speed is added, induced destruction of the drive power generation section that drives the vibrating compressor is reduced, and failure parts are All you have to do is replace it.

By adjusting the operating current of the electronic protection circuit to the specifications, it is possible to set the circuit breaker, fuse, etc. as double protection to a value with sufficient margin.

■4 Since there are fewer chances for fuses to operate, there is no need to consider installing the fuse in a location that is easier to replace than outside.

In addition, when a fuse is used as a current detection element,
Works as a double protection device without the need for a separate breaker etc.

[Brief explanation of drawings]

FIG. 1 shows the configuration of an embodiment of the overcurrent protection device for a vehicle refrigerator according to the present invention, FIG. 2 is a schematic configuration diagram of a vehicle refrigerator in which the present invention is used, and FIG. 3 shows an example of the vehicle refrigerator in which the present invention is used. An example circuit configuration of an on-vehicle refrigerator, FIG. 4 is an explanatory diagram explaining a conventional compressor drive control method, and FIG. 5 is an operation explanatory diagram explaining the operation of the compressor drive control method shown in FIG. 4. It shows. In the figure, 1 is a control circuit, 1-1 is a temperature detection section, 1-2 is a calculation section, 1-3 is a drive circuit, 2.3 is a temperature detector, 4
is a transformer, 5 is a compressor, 6 is a condenser, 7 is a pressure reducer, 8 is a refrigerator, 8-1 is an evaporator, 41 is a drive power generation section, /I2 is an oscillator, 43 is a switching stop circuit, 44
is a comparator. 45 and 46 represent an AND circuit, 47 an inverter, 48 a reference power supply, and 49 a shunt resistor.

Claims (1)

[Claims] A compressor drive control device that controls the drive of a vibrating compressor using a predetermined frequency corresponding to a load, comprising a drive power generation section that generates a drive power supply of a predetermined frequency, and a drive power generation section that generates a drive power supply of a predetermined frequency. A compressor drive control device that drives the compressor using a drive power source, the device further comprising a current detection element for detecting a load current of the drive power generation section, and a current detection element configured to detect a predetermined overcurrent in the current detection element. A switching stop circuit is provided that stops the operation of the switching element provided in the drive power generation section when an overcurrent flows through the current detection element, and stops the oscillation of the drive power generation section when an overcurrent flows through the current detection element. An overcurrent protection device for a vehicle refrigerator, characterized in that it protects a machine drive control device.