JPH04257675A - Detecting device for shortage of refrigerant in refrigerating plant for vehicle - Google Patents

Abstract

PURPOSE:To prevent positively a lack of lubrication in a compressor or a lack of cooling or heating capability by a method wherein an early sensing of a lack of refrigerant is enabled. CONSTITUTION:A lower pressure in a low pressure passage ranging from an outlet of an adjusting device 4 to an inlet port of a compressor 1 is detected by a pressure sensor 6, the number of rotation of a compressor 1 is detected by a sensor 8 for sensing the number of rotation and it is judged as a shortage of refrigerant when a lower pressure in the low pressure passage and the number of rotation of the compressor 1 are concurrently less than each of predetermined levels under an operation of a controller 7. With such an arrangement, an influence from a variation in the surrounding air temperature is relatively lighter at the lower pressure than at a higher pressure, resulting in that a shortage of refrigerant can be judged at an early stage. When the compressor 1 shows a higher number of rotation, a higher degree of lowering the lower pressure is attained, so that the judgement may not be carried out.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant shortage detection device for detecting refrigerant shortage in a vehicular refrigeration system.

0002

[Prior Art] In a vehicle refrigeration system such as a vehicle air conditioner, if there is a shortage of refrigerant and the amount is about 30 to 50% of the standard amount, not only will the cooling capacity be insufficient, but also due to insufficient circulation of lubricating oil. Problems such as compressor seizure may occur. For this reason, in the past, a pressure switch was provided in the high-pressure path of the refrigeration system, and when the pressure at the time of shutdown was below a certain level, this pressure switch was activated to interlock the compressor magnetic switch.

0003

[Problem to be Solved by the Invention] However, with the above-mentioned protection device for protecting the compressor from a lack of refrigerant,
Because the pressure in the high-pressure path of a refrigeration system fluctuates greatly depending on the outside temperature and engine speed (i.e., this pressure is considerably lower when the outside temperature is low), refrigerant can only be used when virtually no refrigerant is present. There was a problem that the shortage could not be detected.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a refrigerant shortage detection device for a vehicle refrigeration system that can detect refrigerant shortage at an early stage.

[0005]

[Means for Solving the Problems] A refrigerant shortage detection device for a vehicle refrigeration system of the present invention includes a pressure detection means for detecting a low pressure in a low pressure path from an outlet of a throttle to an inlet of a compressor, and a rotation of the compressor. The present invention is characterized by comprising a rotation speed detection means for detecting the number of revolutions, and a refrigerant shortage determination means for receiving signals from each of the means and determining a refrigerant shortage state when the low pressure and the rotation speed are respectively below a predetermined level.

[0006]

[Operation and Effects of the Invention] The pressure detection means detects the low pressure in the low pressure path, the rotation speed detection means detects the rotation speed of the compressor linked to the engine rotation speed, and the refrigerant shortage determination means detects the low pressure and rotation speed. It is determined that there is a refrigerant shortage state when both of the refrigerant and the refrigerant are simultaneously at a predetermined level or lower.

Compared to the pressure in the high pressure path (high pressure) of a vehicle refrigeration system that changes significantly due to fluctuations in outside temperature, the influence of outside air temperature on the pressure in the low pressure path (low pressure) is relatively small. . Furthermore, since the evaporator is affected by the indoor temperature, the low pressure will decrease when the indoor temperature drops, but it is generally not considered that the indoor temperature will drop drastically during cooling, and for these reasons, there is usually no shortage of refrigerant. During operation, the low pressure never falls below a predetermined level (1.5 kg/cm2 in a normal vehicle refrigeration system).

However, when the compressor rotation speed linked to the engine rotation speed is high, the amount of refrigerant circulation increases and the low pressure may drop below the above-mentioned predetermined level. Therefore, in the present invention, when the compressor rotation speed is low, Refrigerant shortage is detected only in In this way, it is possible to eliminate the effects of outside temperature fluctuations and detect refrigerant shortages at an early stage, preventing a decline in cooling capacity and ensuring that increased wear and seizure of the compressor due to insufficient lubricating oil circulation is prevented. can be prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the refrigerant shortage detection device for a vehicle refrigeration system according to the present invention will be described below with reference to FIG. The vehicle refrigeration system consists of a compressor 1, a condenser 2, and a receiver 3.
, the throttle 4 and the evaporator 5 are successively connected through refrigerant piping to form a closed cycle.

A pressure sensor 6 serving as pressure detection means is installed in a low pressure pipe between the evaporator 5 and the compressor 1, and outputs the detected low pressure to a controller 7 consisting of a microcomputer. Further, the rotation speed detection sensor 8 detects the rotation speed of the engine that drives the compressor 1 and controls the engine.
Output to La7. The controller 7 is a refrigerant shortage indicator lamp 1 provided on the air conditioning operation panel 9 on the dashboard.
0 is lit when determining refrigerant shortage.

The refrigerant shortage determination operation of the controller 7 will be explained with reference to the flowchart of FIG. First, check whether the detected low pressure Ps is lower than 1 kg/cm2, and if it is low, reset the flag F to 0 and wait (101).
Check whether it is lower than pm (103), and if it is not, reset the flag F to 0 and return to 101 (1
02). If the engine speed becomes lower than 1800 rpm, check whether flag F is 1 (105),
If not, start the built-in timer set to 30 seconds (107), set flag F to 1, and execute 101.
Return to.

On the other hand, if flag F is 1 in 105,
Check whether the built-in timer has counted 30 seconds or not, and if 30 seconds have not yet passed, return to 101 and set 30.
After seconds have elapsed, it is determined that there is a refrigerant shortage and the refrigerant shortage lamp 10 is turned on. FIG. 3 shows the relationship between low pressure and refrigerant amount in an actual vehicle refrigeration system. Under the conditions that the speed is 1800 rpm or less and the low pressure is 1 kg/cm2 or less, the refrigerant is 350 g, which is a refrigerant shortage state with respect to the standard charging amount of 650 g. On the other hand, at an engine speed of 3600 rpm,
The amount was 430g, which cannot be said to be a refrigerant shortage condition that would cause a lack of lubrication.

Next, the reason for providing a 30 second timer or time limit means in the above flowchart will be explained. When a vehicle refrigeration system is started after being left at a high temperature, a large amount of refrigerant begins to circulate, but initially there is a temporary shortage of refrigerant in the evaporator, causing the evaporator pressure (low pressure) to drop. 1
kg/cm2 or less, and even when the load is low, that is, when the room temperature is very low, the evaporator may cool down and its low pressure may drop to less than 1 kg/cm2.

However, when starting from a state where it has been left at a high temperature,
Since the refrigerant returns to the evaporator within 30 seconds, erroneous operation can be prevented by setting the time limit to 30 seconds. Additionally, if the evaporator 5 cools down and its low pressure drops to 1 kg/cm2 or less, the defrost or other cutting device will operate and the compressor 1 will stop before 30 seconds have elapsed. Misoperation can be prevented by setting a time limit. That is, if a time limit means is provided for detecting the underpressure time during which the low pressure is below a predetermined value. Furthermore, refrigerant shortage can be detected more reliably.

In the above embodiment, a pressure switch can be used instead of the pressure sensor 6 as the pressure detection means. Further, by changing the threshold level of the low pressure, it is possible to detect refrigerant shortage even when the heat pump is in operation. Furthermore, it is also possible to change the rotation speed threshold level according to the pressure value detected by the pressure sensor 6.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the device of the present invention;

[Fig. 2] Flowchart showing the operation of the controller,

[
Figure 3: Characteristic diagram showing the relationship between low pressure and refrigerant amount,

[Explanation of symbols]

6 is a pressure sensor (pressure detection means), 7 is a controller (
8 is a rotation speed sensor (rotation speed detection means),

Claims (1)

[Claims] 1. Pressure detection means for detecting low pressure in a low pressure path from the outlet of the throttle to the inlet of the compressor, rotation speed detection means for detecting the rotation speed of the compressor, and receiving signals from each of the means, A refrigerant shortage detection device for a vehicular refrigeration system, comprising: refrigerant shortage determination means for determining a refrigerant shortage state when a low pressure and a rotation speed are each below a predetermined level.