JPS621845B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bus cooling device.

As a bus cooling device, a sub-engine as a driving source, a compressor driven by the sub-engine,
A so-called sub-engine-driven cooling system is generally used, in which cooling equipment such as a condenser and evaporator, a power transmission system, and an air blowing system such as a blower fan are integrated into a unit and mounted under the floor of the car body (for example, in 1973-
(See Publication No. 27835).

A conventional system diagram of such a sub-engine-driven cooling device is shown in FIG.

That is, the sub-engine 1 directly connects and drives the compressor 9, and also drives the compressor 9 through a power transmission mechanism such as the pulleys 3 and 4, the V-belt hooked thereto, the universal joint shaft 5, and the V-belt hooked around the pulleys 6 and 7. The blower fan 8 is driven to rotate, and the high-pressure, high-temperature refrigerant gas discharged from the compressor 9 is sent to the condenser 10 as shown by the solid arrow.
While passing through the cooling fan 2, the liquid refrigerant is cooled by the air cooling means and enters the liquid receiver 11. Only the liquid refrigerant flows into the expansion valve 12 and enters the evaporator 13 in a low temperature, low pressure gas-liquid mixed state. The circulating air inside the bus is cooled into cold air and the cold air is blown into the room.

The refrigerant that cooled the air while passing through the evaporator 13 is evaporated into gas and is sucked into the compressor 9 again.

The refrigerant circulation circuit is also provided with a bypass circuit that bypasses the refrigerant gas slightly cooled in the condenser 10 to the suction side of the compressor 9 as indicated by the dotted arrow, and the bypass circuit is opened and closed by a control valve 21. Through this control, the flow rate of refrigerant flowing through the evaporator 13 can be controlled.

14 is a radiator for cooling the cooling water of the sub-engine 1, and the cooling water that has cooled the sub-engine 1 reaches the radiator 14 as shown by the chain arrow, where it is radiated by air cooling means by the cooling fan 2 and is then returned to the sub-engine 1. Inflow.

In the conventional device as described above, when the air conditioner is running too high during cooling operation and the indoor temperature becomes cold, the control valve 21 is automatically or manually opened to reduce the refrigerant flow rate in the main circuit and reduce the cooling capacity. The room temperature is controlled, but generally the amount of temperature drop of the air cooled by the evaporator varies depending on the amount of air blown by the blower fan 8, so the amount of temperature drop is approximately 2 degrees Celsius as shown in Figure 4. Therefore, when the room temperature, that is, the inlet air temperature of the evaporator is the appropriate cooling temperature of 25°C, the outlet air temperature will vary from 5 to 7°C, and when the outlet air temperature is about 5°C, the refrigerant evaporation temperature will be -
The temperature will be about 5 to -7°C, and there is a risk that the evaporator will start to frost or freeze.

In order to prevent such problems, a measure has been adopted in the past to provide a thermoswitch 19 that opens the control valve 21 when the outlet air temperature of the evaporator 13 falls below a predetermined value. In order to prevent the influence of condensed water on the outlet side, the thermoswitch 19 must be waterproof. Therefore, even if the temperature difference between on and off temperatures of the thermoswitch 19 itself is about 2°C, the heat capacity of the thermoswitch 19 as a whole is small. The switch 19 will not operate unless the switch 19 is heated or cooled until there is a temperature difference of about 4 to 5 degrees Celsius between the positive and negative sides, and the temperature of the cold air blown out when the bypass circuit is closed and when it is open. The difference is large, and when the bypass circuit opens, the temperature at which the cold air blows suddenly rises, which not only spoils the sense of coolness for passengers, but also causes the average room temperature during cooling to rise to 26-27 degrees Celsius, resulting in a lack of cooling effect. have.

Furthermore, when the control valve 21 opens, the high-pressure refrigerant gas in the condenser suddenly flows to the low-pressure suction side of the compressor, resulting in the generation of refrigerant flow noise, which may cause discomfort to passengers.

The main purpose of the present invention is to eliminate the various drawbacks of the prior art as described above, and the present invention will be explained below with reference to the embodiments shown in FIGS. 1 and 2.

In the present invention, as shown in FIG. 1, a compressor 9 driven by a sub-engine 1, a cooling fan 2
A main refrigerant circuit consisting of a condenser 10, a liquid receiver 11, an expansion valve 12, and an evaporator 13, which are cooled by a In a sub-engine-driven cooling system consisting of a blower fan 8 etc. that is rotationally driven by the sub-engine 1 by a power transmission mechanism such as a V-belt hung on the evaporator 13 (upstream side of circulating air). A radiator 15 is provided in the radiator 15, an air heating circuit A is provided in which cooling water for the sub-engine 1 is circulated through the radiator 15 and then returned to the sub-engine 1, and a hot water control valve 16 is provided in the air heating circuit A. The hot water control valve 16 is configured to control the flow of cooling water to the air heating circuit A by turning on and off in response to a signal from a thermoswitch 20 that is activated by detecting the air temperature at the inlet of the evaporator 13. It is something.

In the device of the present invention configured as described above,
During cooling operation, when the room temperature, that is, the inlet air temperature of the evaporator 13 is above a predetermined value, the thermoswitch 20 is turned off, the hot water control valve 16 is closed, and the air heating circuit A is turned off.
Engine cooling water does not flow through the fan 8, and the indoor air sucked in by the fan 8 is cooled by the evaporator 13 and then blown into the room, and the conventional cooling operation is performed.

When the room temperature falls and the inlet air temperature of the evaporator 13 reaches the temperature that should be the frosting temperature at the evaporator outlet, the thermo switch 20 is turned on, the hot water control valve 16 is opened, and the cooling water (hot water) after cooling the engine releases heat. Vessel 1
5, the indoor air is heated while passing through the radiator 15 and enters the evaporator 13, increasing the inlet air temperature of the evaporator 13 and raising the outlet air temperature to above the frosting temperature to prevent frosting. To prevent.

In this case, the sub-engine 1 only drives the compressor 9, fans 2 and 8, etc., so its load is almost constant.Furthermore, the built-in thermostat in the engine cools the engine when the engine cooling water temperature exceeds a certain value. Water is flowed through the radiator 14 to radiate heat and keep the cooling water temperature almost constant.
The temperature of the cooling water flowing from the air heating circuit A to the radiator 15 is almost constant and stable, and setting the amount of heating of the inlet air of the evaporator 13 is extremely easy.

In addition, as shown in Figure 4, the relationship between the inlet air temperature and outlet air temperature of the evaporator is that, at the average value shown by the thick line, even if the inlet temperature changes by 10°C from 30°C to 20°C, the outlet temperature does not change. The change is about 4.5 degrees Celsius. For example, when the inlet air temperature is 23 degrees Celsius, the thermoswitch 20 operates, the hot water control valve 16 opens, and the radiator 15 heats up the inlet air temperature by about 5 degrees Celsius, then the evaporator 13 The temperature of the outlet air increases by approximately 2°C, making it possible to prevent problems such as frost formation without significantly changing the temperature of the air supplied indoors.

When the inlet air temperature of the evaporator 13 is increased by the radiator 15 and reaches the off-point set temperature of the thermoswitch 20, the thermoswitch 20 is turned off, the hot water control valve 16 is closed, and the cooling water ( Hot water) no longer flows, and the radiator 15 is gradually cooled down by the indoor air until it reaches room temperature, and the thermoswitch 20 is turned on again to open the hot water control valve 16.

As mentioned above, the fact that the change in the outlet air temperature with respect to the change in the inlet air temperature of the evaporator is extremely small means that, as in the present invention, the thermoswitch 20 that operates by sensing the inlet air temperature of the evaporator is provided. In this case, it can be said that even if the range of on/off set temperatures of the thermoswitch 20 is relatively large, the indoor cooling effect will not be significantly impaired, and the thermoswitch 20 is placed on the upstream side of the evaporator 13. Since the thermoswitch 20 is installed at be.

Of course, it is preferable to install the thermoswitch 20 at an intermediate position between the radiator 15 and the evaporator 13 as shown in the first figure, but it should be installed in the hot water passage on the downstream side of the radiator 15 like 20' so that the hot water in the radiator 15 The inlet air temperature of the evaporator 13 may be indirectly detected based on the amount of temperature change of It may be turned on when the inlet air temperature of the radiator 15 is below a predetermined value, and turned off when the outlet air temperature of the radiator 15 reaches a predetermined value.

Fig. 2 shows a case in which all of the devices shown in Fig. 1 are mounted on a frame 17 to form an integrated cooling unit, and this is attached under the floor of the car body with connecting members such as bolts, thereby incorporating an evaporator 13 and a radiator 15. 18
An example is shown in which the air intake port 18' communicates with the interior of the vehicle, and the outlet of the blower fan 8 communicates with a cold air blowing duct provided on the ceiling of the vehicle body, for example, via a riser duct or the like.

In FIG. 2, reference numeral 18'' is a unit inspection opening/closing lid provided on the case 18, and the same reference numerals in FIG. 2 as in FIG. 1 represent the same parts.

As described above, according to the present invention, by controlling the inlet air temperature of the evaporator using the cooling water of the engine, which is the driving source of the cooling device, the evaporator is heated without significantly changing the temperature of the cold air blown into the room. It is possible to prevent frost from forming on the air, significantly improve the feeling of cooling for passengers, and also simplify the equipment and reduce costs.
This can bring about great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a cooling system diagram showing an embodiment of the present invention, Fig. 2 is a front explanatory view showing an example of the unit shown in Fig. 1, Fig. 3 is a conventional cooling system diagram, and Fig. 4 is a diagram of a conventional cooling system. It is a figure showing the relationship between inlet air temperature and outlet air temperature of an evaporator. 1...Sub engine, 9...Compressor, 10...
Condenser, 11...Liquid receiver, 12...Expansion valve, 13
... Evaporator, 14 ... Radiator, 15 ... Heat radiator, 16 ... Hot water control valve, 20 ... Thermoswitch.

Claims (1)

[Claims] 1 In a cooling system using an engine as a driving source,
A radiator is provided on the upstream side of the evaporator in the air flow direction, forming an air heating cooling water circulation circuit in which the engine cooling water flows through the radiator and returns to the engine. A hot water control valve is provided that opens the air heating cooling water circulation circuit when the temperature falls below a predetermined value, and closes the air heating cooling water circulation circuit when the inlet air temperature of the evaporator reaches a predetermined value or higher. A bus cooling device featuring: