JPH0228376Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for a vehicle air conditioner, and in particular to protection of a compressor.

Conventionally, as shown in Utility Model Publication No. 57-42097, a protection device has been known that detects a refrigerant shortage by determining the liquid level in a receiver tank and stops the compressor when a refrigerant shortage occurs. It is.

However, if the compressor were to be completely stopped when there is a shortage of refrigerant, no cooling would be achieved and the comfort of cooling would be significantly impaired. Normally, even if a refrigerant shortage occurs, if the amount of shortage does not interfere with the operation of the compressor, operating the compressor with its capacity reduced can compensate for comfort to a certain extent and prevent a decrease in passenger feeling. However, this was not possible with conventional devices. In addition,
In the above-mentioned conventional protection device, the compressor is stopped after a set time delay after a refrigerant shortage occurs, but even if such measures are taken, the compressor will not operate at all after the set time has elapsed, and the comfort level will still be affected. This will damage the In particular, if the setting time is increased, the compressor may be damaged.

The purpose of the present invention is to provide a compressor with a protective means that stops the compressor when the refrigerant pressure, refrigerant temperature, surface temperature, or engine speed in piping including the compressor reaches a set level. The above disadvantages are eliminated by lowering the compressor by a predetermined value and operating the compressor until the surface temperature or engine speed reaches the set level, and will be described in detail below using examples.

FIG. 1 is a circuit diagram showing an embodiment of a protection device for a vehicle air conditioner according to the present invention, in which 1 is a power source, 2 is an ignition switch,
3 is an air conditioner switch, a relay 5 is connected to the air conditioner switch 3 via a normally closed contact 4, one end of a normally open contact 6 controlled by this relay 5 is connected to the ignition switch 2, and the other end is connected to the ignition switch 2. The end is connected to an electromagnetic clutch 7 which drives the compressor. A relay 8 controlling the contact 4 is grounded via a transistor 9. Temperature detection switches 10 and 1 are connected to the base side of the transistor 9.
The other end of the temperature detection switch 10 is connected to the air conditioner switch 3 via a resistor 12, and the temperature detection switch 11 is connected to the emitter side of the transistor 13. The collector of transistor 13 is connected to resistor 12 and switch 10.
The base side of this transistor 13 is connected to the connection point between resistors 14 and 15. The resistor 14 is connected to the air conditioner switch 3 via a refrigerant shortage detection switch 16. The connection point between the resistor 14 and the resistor 15 is a transistor 17
The emitter side of this transistor 17 is grounded, and the collector side is connected to a series circuit consisting of a warning light 18 consisting of a light emitting diode and a resistor 19.

The temperature detection switches 10 and 11 detect the surface temperature of the compressor, and switch 11 is turned on when the surface temperature reaches, for example, about 120°C, and switch 10 is turned on when the surface temperature reaches about 150°C. The operating level is set as follows.
Further, the refrigerant shortage detection switch 16 is constituted by, for example, a switch that detects the liquid level in the receiver tank, and is turned on when a refrigerant shortage occurs.

The operation of the protection device for a vehicle air conditioner with the above configuration will be explained below using the characteristic diagram shown in FIG. 2.

First, when the ignition switch 5 and the air conditioner switch 3 are on and there is no refrigerant shortage, if the temperature of the compressor rises due to, for example, an oil film running out, and this temperature reaches about 150°C, the temperature detection switch 10 is turned on. turns on, relay 8 is energized, contact 4 is turned off, relay 5 is deenergized,
Since the contact 6 is turned off, the electromagnetic clutch 7 is not driven and the compressor is stopped, so that seizure of the compressor can be prevented. When the surface temperature falls below 150°C, the compressor is driven again. In this manner, the temperature detection switch 10 functions as a protection means for preventing seizure of the compressor. That is, even if there is no shortage of refrigerant, when the temperature exceeds 150° C., the viscosity of the lubricating oil contained in the refrigerant decreases and the lubricity is impaired, so seizure may occur. Note that at this time, the temperature detection switch 11 is also on, but the transistor 13 is off, so the transistor 9 is not controlled by this.

Next, when a refrigerant shortage occurs due to a leak in the piping or the like and the switch 16 is turned on, the transistor 17 is turned on and the warning light 18 lights up to notify of the refrigerant shortage. Further, the base potential of the transistor 13 is set to be the same as the base potential of the transistor 17. When the temperature on the surface side of the compressor gradually rises due to refrigerant shortage and reaches about 120℃, the temperature detection switch 11 is turned on, turning on the transistor 9, turning off the contact 4, turning off the contact 6, and the compressor stops. be done. Therefore, even if there is a refrigerant shortage, the compressor's surface temperature will remain at 120℃, for example.
Since the operation continues until the temperature reaches a certain level, a certain degree of cooling comfort can be ensured. When the above surface temperature drops due to the compressor stopping, switch 1
1 is turned off and the compressor is driven again. In this way, the compressor is turned on and off to maintain the surface temperature at 120°C and is operated at low capacity. This embodiment has a protection means that normally stops the compressor when the surface temperature of the compressor reaches about 150℃, but when there is a shortage of refrigerant, the compressor is turned on and off by lowering the temperature to a level of 120℃. The cooling performance is compensated by driving the air conditioner. Even if the compressor is operated in a state of lack of cooling, it will be stopped when its surface temperature reaches 120℃, which is lower than the normal temperature, so the compressor will not be operated for a long time in a state of lack of refrigerant. There is no risk of damage. In other words, when there is a shortage of refrigerant, there is also a shortage of lubricating oil contained in the refrigerant, which, combined with a decrease in viscosity at high temperatures, may result in loss of lubricity and seizure even in the range of 120°C to 150°C. Stopping the compressor at this point is effective in preventing seizure when there is a shortage of refrigerant.

FIG. 3 is a circuit diagram of another embodiment of the protection device for a vehicle air conditioner according to the present invention, in which a power source 20 is connected to an ignition switch 21 and an electromagnetic clutch 23 via a contact 22. . An air conditioner switch 24 connected to the ignition switch 21 is connected to ground via a relay 25 that controls the contact 22 and a contact 26.
One end of a relay 27 that controls the contact 26 is connected to the collector of a transistor 28, and the other end is grounded. The emitter of the transistor 28 is connected to the air conditioner switch 24, and the base thereof is connected to the output terminal of a comparator 29 via a resistor 30. The above ignition switch 21 is the coil 3
A spark plug control point 32 is connected through the coil 31 and the point 32, and a pulse with a frequency corresponding to the engine speed is obtained from the connection point between the coil 31 and the point 32.
4, 35, 36, 37, a capacitor 38, and a transistor 39.
44, and resistors 45, 46, and 47 to a frequency-voltage conversion circuit 48, and the output voltage V1 of this frequency-voltage conversion circuit 48 has a magnitude proportional to the engine speed. This voltage V1 is applied to the comparator 29
is supplied to the negative input side of the The positive input side of the comparator 29 is connected to the connection point between the resistors 49 and 50. A series circuit of a resistor 51, a refrigerant shortage detection switch 52, and a contact 53 controlled by the relay 27 is connected in parallel with the resistor 50, and a series circuit of a resistor 54 and a refrigerant shortage detection switch 55 is connected. . The air conditioner switch 24 is grounded via a resistor 56, a warning light 57 consisting of a light emitting diode, and the refrigerant shortage detection switch 58. Each of the above refrigerant shortage detection switches 52, 55, 5
8 are turned on when a refrigerant shortage occurs, and they are interlocked with each other.

Here, if there is no refrigerant shortage and the refrigerant shortage detection switches 52, 55, and 58 are off, the voltage on the positive input side of the comparator 29 is between the resistors 49 and 58.
In this embodiment, this voltage Va is set to a voltage corresponding to the engine rotation speed of 6000 rpm. Also, contact 5
3 is off and the switches 52, 55, and 58 are on, the resistor 54 is connected in parallel to the resistor 50, so the voltage on the positive input side of the comparator 29 becomes a voltage Vb smaller than the voltage Va. . In this embodiment, the voltage Vb at this time is set to a voltage corresponding to an engine rotational speed of 5000 rpm.
Next, the contact 53 is on, and the switches 52, 55, 5
8 is on, the resistor 51 is connected to the resistor 50,
54 are connected in parallel, the voltage on the positive input side of the comparator 29 further decreases to the voltage Vc, and the voltage Vc at this time is determined by the engine speed.
The voltage shall be set to correspond to 300 rpm.

The operation of the protection device for a vehicle air conditioner with the above configuration will be explained using the characteristic diagram shown in FIG. 4. When the ignition switch 21 and the air conditioner switch 24 are on,
There is no refrigerant shortage and each switch 52,5
5 and 58 are off, when the engine speed exceeds 6000 rpm which is the high speed rotation level, the output voltage V1 of the frequency-voltage conversion circuit 48 becomes lower than the voltage Va set by the resistors 49 and 50. increases, so the output of the comparator 29 becomes L level, the transistor 28 is turned on, the relay 27 is energized, the contact 26 is turned off, the relay 25 is deenergized, and the contact 22 is turned off, so the electromagnetic clutch 23 is energized. This causes the compressor to be shut down. In other words, as shown in Figure 4, the compressor is stopped when the engine speed reaches a high speed level of 6000 rpm, so it functions as a protective means to prevent damage to the compressor bearings, etc. due to the compressor rotating at high speed. do. At this time, the contact 53 is turned on, but since the switch 52 is turned off, no change is given to the comparator 29.

Next, when the engine speed increases from 3000 rpm or less, when a refrigerant shortage occurs and each switch 52, 55, 58 is turned on, the warning light 57
lights up to notify you of refrigerant shortage. Also switch 5
5 is turned on, the resistor 54 is connected in parallel to the resistor 50, and the positive input side voltage of the comparator 29 becomes the voltage.
Decreases to Vb. On the other hand, since the relay 27 is not yet energized, the contact 53 is off.
Even if the switch 52 is turned on, the resistor 51 is not connected in parallel to the resistor 50. In this way, when the voltage on the positive input side of the comparator 29 becomes Vb, when the engine speed reaches 5000 rpm, the output of the comparator 29 becomes L level, the transistor 28 is turned on, and the relay 27 is energized, so the compressor will be stopped. Therefore, when a refrigerant shortage occurs, the compressor is stopped at a level lower than the high speed rotation level at which a normal compressor is stopped, so the capacity of the compressor can be reduced and damage to the compressor is not caused. In other words, when there is a shortage of refrigerant, there is also a shortage of lubricating oil contained in the refrigerant, resulting in a decrease in lubricity.
Since seizure may occur even in the range of 5000rpm to 6000rpm, stopping the compressor at 5000rpm or higher is effective in preventing seizure when there is a refrigerant shortage. Additionally, the compressor operates until the engine speed reaches 5000 rpm, ensuring cooling performance.

Next, when a refrigerant shortage occurs and the engine speed reaches 5000 rpm and the relay 27 is energized and the compressor is stopped, the contact 53 is turned on, so the switch 52 is turned on at this time. , the resistor 51 and the resistor 54 are connected in parallel to the resistor 50, and the voltage on the positive input side of the comparator 29 drops to the voltage Vc. Therefore, even if the engine speed reaches 5000rpm and becomes slightly lower than 5000rpm, the output of the comparator 29 will not be reversed to the H level, but will only be reversed when the engine speed becomes lower than 3000rpm, and the compressor will be driven again. This means that if the compressor is immediately activated when the engine speed drops slightly below 5000 rpm, the compressor will be operated in a state of insufficient refrigerant, and the compressor cannot be protected. According to this embodiment, the compressor is driven only when the engine speed drops to 3000 rpm, so this problem does not occur. Although the protection device has been described as being activated by detecting the temperature of the compressor, it may be activated when the refrigerant pressure and temperature of the piping system including the compressor reach a certain level.

As explained above, according to the protection device for a vehicle air conditioner according to the present invention, the compressor is stopped when the refrigerant pressure, refrigerant temperature or surface temperature of the piping system including the compressor, or the engine speed reaches a set level. In the protection device for a vehicle air conditioner, the control means lowers the set level of the protection means by a predetermined value based on a signal from the refrigerant shortage detection means, and the control means lowers the set level of the protection means by a predetermined value. Turn off the compressor when the system refrigerant pressure, refrigerant temperature, or surface temperature reaches a level below normal temperature or pressure, or when the engine speed reaches a speed below the normal high speed level. Since the compressor is turned off at the same time, a certain degree of cooling can be achieved while protecting the compressor, and there is no fear that the comfort of the air conditioner will be impaired.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the protection device for a vehicle air conditioner according to the present invention, FIG. 2 is a characteristic diagram for explaining its operation, and FIG. 3 is a vehicle air conditioner according to the present invention. FIG. 4 is a circuit diagram showing another embodiment of the protection device, and FIG. 4 is a circuit diagram for explaining its operation. 1,20...power supply, 21...ignition switch, 3,24...air conditioner switch, 10,
11... Temperature detection switch, 16, 52, 55,
58... Refrigerant shortage detection switch, 18, 57...
Warning light, 40... waveform shaping circuit, 48... frequency voltage conversion circuit.

Claims (1)

[Scope of utility model registration request] In a protection device for a vehicle air conditioner that has a protection means for stopping the compressor when the refrigerant pressure or temperature or surface temperature of the piping system including the compressor side or the engine speed reaches a set level, the refrigerant shortage detection means A protection device for an air conditioner for a vehicle, characterized in that a control device is provided for lowering a set level of the protection device by a predetermined value based on a signal from a vehicle.