JPH0136058Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement in the control of a compressor in an automotive air conditioner.

A compressor in an automobile air conditioner is generally connected to the automobile engine via an electromagnetic clutch, and driving and stopping of the compressor is controlled by turning on and off the electromagnetic clutch. Conventionally, the electromagnetic clutch was turned on and off to prevent the evaporator from freezing or to adjust the temperature inside the vehicle, but if this was done frequently, it would cause an on/off shock to the compressor drive system, causing the electromagnetic clutch to turn on and off. This will shorten the lifespan of the air conditioner, adversely affect the driving performance of the vehicle, and cause sudden changes in the temperature of the blown air.
Several attempts have been made to minimize the on/off times of electromagnetic clutches.

One such method is known, for example, as shown in Japanese Patent Application Laid-open No. 57-167820, in which the evaporation pressure of the evaporator is adjusted, and when the heat load becomes small, the amount of evaporated refrigerant is limited to provide cooling. This reduces the capacity and reduces the number of times the electromagnetic clutch turns on and off. However, in this method,
Since the flow of refrigerant is restricted, the power consumption for driving the compressor is large, resulting in poor fuel efficiency.

In addition, as another example, for example, JP-A-57-
As shown in Publication No. 160709, a method is known in which the capacity of the compressor is changed. When the heat load decreases, the capacity of the compressor is reduced, thereby reducing the on/off times of the electromagnetic clutch and reducing power consumption. . However, with this system, there is a limit to the low capacity, so if the heat load becomes even smaller, the electromagnetic clutch must be turned off to prevent the evaporator from freezing. There was a drawback that the number of on/off cycles could not be reduced below a predetermined value. In order to overcome this drawback, it would be possible to change the compressor continuously from a no-load operating state to a maximum capacity operating state, but the mechanism for changing the capacity and the configuration of the control circuit would be complicated and expensive. Become.

Therefore, the object of this invention is to eliminate the above-mentioned conventional drawbacks, and to provide an automobile air conditioner that consumes less power, has a simple configuration, and can extremely reduce the number of times the electromagnetic clutch turns on and off. . Therefore, the gist of this invention is to provide a cooling cycle including a compressor connected to an engine via an electromagnetic clutch and an evaporator for evaporating refrigerant, and a capacity variable device that changes the capacity of the compressor into at least two stages. , the evaporation pressure of the evaporator is at least 2
The thermoswitch is equipped with an evaporation pressure adjustment device that adjusts the evaporation pressure in stages, and a thermoswitch that controls the operation of the evaporation pressure adjustment device and the variable capacity device based on the output from the heat load detector. When the heat load becomes less than the first set value, the compressor is switched to a smaller capacity, and when the heat load becomes less than the second set value, which is lower than the first set value, the evaporation pressure of the evaporator is increased to a predetermined value or more. There are restrictions on automotive air conditioners.

Therefore, when the heat load of the compressor decreases, its capacity is first switched from large to small, and then its evaporation pressure is limited to a predetermined level.
Since it is always driven with appropriate cooling capacity, there is no need to turn on and off the electromagnetic clutch during cooling operation.
Moreover, since the evaporation pressure is limited at the stage when the capacity is small, the power consumption is low, and since the control of the capacity and evaporation pressure is combined and carried out by a thermoswitch, the configuration is simple. Therefore, the above problems can be achieved. It is something that can be done.

Examples of this invention will be described below with reference to the drawings.

In FIG. 1, an outline of an embodiment of this invention is shown, and a cooling cycle 1 includes a compressor 2, a condenser 3, a liquid tank 4, an expansion valve 5, an evaporator 6, and an evaporation pressure adjustment device 7, which will be described later, connected to piping. has been configured.

The compressor 2 is connected to an automobile engine (not shown) via an electromagnetic clutch 8, and is also provided with a variable capacity device 9. This variable capacity device 9 changes the angle of the swash plate if the compressor 2 is of the swash plate type, changes the effective number of vanes if the compressor 2 is of the vane type, and also changes the angle of the swash plate if the compressor 2 is of the swash plate type. Change the amount of return,
This includes known methods such as changing the pulley ratio of a belt transmission device interposed between the engine and the compressor 2, and substantially changing the capacity of the compressor 2. These operations are performed by, for example, a solenoid, The capacity of the compressor 2 is switched between two stages: high capacity and small capacity.

The refrigerant gas discharged from the compressor 2 is condensed by the condenser 3, separated into gas and liquid by the liquid tank 4, and expanded by the expansion valve 5 to become low-temperature, low-pressure wet vapor.
It is evaporated by the evaporator 6. The expansion valve 5 is of a heat-sensitive type, and is designed to keep the degree of superheat of the evaporator 6 constant based on the output from the humidity-sensitive tube 5a.

The evaporation pressure regulating device 7 includes a low pressure regulating valve 1 inserted between the compressor 2 and the evaporator 6.
0, a bypass passage 11 that bypasses this low pressure regulating valve 10, and a solenoid valve 12 provided in this bypass passage 11. The low pressure regulating valve 10 is, for example, a known suction throttle valve STV,
When the electromagnetic valve 12 is closed, the throttle amount is adjusted according to the pressure on the outlet side of the evaporator 6, and the evaporation pressure of the evaporator 6 is limited to a predetermined value or more. On the other hand, when the solenoid valve 12 is open, the refrigerant gas exiting the evaporator 6 bypasses the low pressure regulating valve 10 and is sucked into the compressor 2 as it is. In addition, as another embodiment, instead of providing the bypass passage 11 and the solenoid valve 12, the valve body of the low pressure regulating valve 10 may be directly moved by a motor or the like.

The control circuit 13 controls the operation of the capacity variable device 9 and the evaporation pressure adjustment device 7 based on the output from the heat load detector 14 that detects the fin temperature of the evaporator 6 or the temperature of the air passing through the evaporator 6, Further, the operation of the electromagnetic clutch 8 is controlled, and a specific example of the control circuit 13 is shown in FIG.

In FIG. 2, the coil 8 of the electromagnetic clutch
A has one end connected to the vehicle battery 15 and the fuse 1.
6 and a power relay contact 17a, and when the power relay contact 17a is closed, electricity is supplied to drive the compressor. Further, the contact point 17a of the power relay is a normally open contact, and is closed when the coil 17b of the power relay is excited. The coil 17b of this power relay has one end connected to the vehicle battery 15 and the ignition switch 1.
8. It is connected through the fuse 19, the blower switch 20, and the air conditioner switch 21, and the other end is grounded, and the ignition switch 18 and the air conditioner switch 21 are closed, and the blower switch 20 is set to a position other than off. It is energized and energized when it is present. The blower switch 20 is connected to a blower motor 22 via a resistor coil 23, and selection of the blower switch 20 sets the rotational speed of the blower motor 22 and determines the amount of air sent to the evaporator.

Further, in the electromagnetic clutch drive circuit including the coil 8a of the electromagnetic clutch, a thermoswitch 24 is connected in parallel to the coil 8a.
This thermo switch 24 is connected to the heat load detector 1.
It has two changeover switches 24a and 24b that are turned on and off according to the output from 4. Then, one selector switch 24a is turned on and off based on a first set value _t1 (for example, 6°C to 9°C), and when the output from the heat load detector 14 becomes less than this first set value _t1 . Close the solenoid 9a of the variable capacity device.
energize and switch the compressor to small capacity. Further, the other changeover switch 24b is set to the first setting value.
A second set value t ₂ lower than t ₁ (e.g. 0°C to 3°C)
Similarly, when the output from the heat load detection device 14 becomes less than this second set value t2, it closes and energizes the coil _12a of the solenoid valve, thereby limiting the evaporation pressure of the evaporator to a predetermined value or more. .
Note that an appropriate differential is provided for the first and second set values t ₁ and t ₂ .

In the above configuration, the ignition switch 18 is now closed, the blower switch 20 is set to other than off to drive the blower, and the air conditioner switch 21 is turned off.
When closed, the coil 17b of the power relay is energized, so the contact 17a is closed, the coil 8a of the electromagnetic clutch 8 is energized, and the compressor 2 starts to be driven. When the compressor 2 starts driving, the heat load is large and the temperature of the evaporator 6 is higher than the first set value _t1 , so the thermoswitch 2
Both changeover switches 24a and 24b of No. 4 are open, and the compressor 2 has a large capacity and continues to be driven without being restricted by the evaporation pressure. Therefore, the cooling capacity of the compressor 2 is large, and the interior of the vehicle is rapidly cooled. Good cool-down properties are maintained.

Then, the heat load becomes smaller and the evaporator 6
When the temperature becomes lower than the first set value _t1 , one selector switch 24a of the thermo switch 24 closes.
The capacity of compressor 2 is switched to a small capacity. As a result, the power consumption of the compressor 2 is reduced and the cooling capacity is reduced, and if this cooling capacity and the heat load are balanced, the compressor 2 continues to be driven at a small capacity.

Then, when the heat load further decreases and the temperature of the evaporator 6 falls below the second set value _t2 , the other changeover switch 24b of the thermoswitch is also closed, so the solenoid valve 12 of the evaporation pressure regulator 7 is closed. , the operation of the low pressure regulating valve 10 becomes effective, and the compressor 2 remains driven at a small capacity.
Evaporation pressure is limited to a predetermined value or higher. Therefore, since the evaporation pressure of the evaporator 6 is maintained above a predetermined level, there is no risk of freezing, the compressor 2 continues to be driven, and there is no need to turn the electromagnetic clutch 8 on and off.

Note that when the temperature of the evaporator 6 increases due to an increase in the heat load or a decrease in vehicle speed, the above operation is reversed.

In the above embodiment, the evaporating pressure regulator 7, the variable capacity device 9, and the thermoswitch 24 are each switched to two stages, but the invention is not limited to this, and it is possible to switch to three or more stages as long as it is compatible. It can be done.

As mentioned above, according to this invention, as the heat load decreases, the capacity of the compressor is switched to a smaller capacity, and then the evaporation pressure is limited, so the electromagnetic clutch is switched on and off during cooling operation. This eliminates the need for on-off shocks and prevents on-off shocks. Moreover, since the capacity of the compressor is changed, power consumption is reduced, fuel efficiency is improved, and since the capacity of the compressor can be changed in stages, it is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of this invention, and FIG. 2 is an electric circuit diagram showing a control circuit used in the same. 1... Cooling cycle, 2... Compressor, 6
... Evaporator, 7 ... Evaporation pressure adjustment device, 8
...Electromagnetic clutch, 9...Capacity variable device, 10...
...Low pressure regulating valve, 11...Bypass passage, 12...
Solenoid valve, 14...heat load detector, 24...thermo switch.

Claims (1)

[Claims for Utility Model Registration] 1. A cooling cycle including a compressor connected to an engine via an electromagnetic clutch and an evaporator for evaporating refrigerant, a capacity variable device for changing the capacity of the compressor into at least two stages, and the evaporator an evaporation pressure adjustment device that adjusts the evaporation pressure of the thermostat in at least two stages; and a thermoswitch that controls the operation of the evaporation pressure adjustment device and the capacity variable device based on the output from the heat load detector. The switch is
When the heat load becomes less than or equal to the first set value, the compressor is switched to a smaller capacity, and when the heat load becomes less than or equal to the second set value, which is lower than the first set value, the evaporation pressure of the evaporator is changed. An air conditioner for an automobile, characterized in that the air conditioner limits the air to a predetermined level or more. 2. The evaporation pressure regulating device consists of a low pressure regulating valve inserted between the compressor and the evaporator of the cooling cycle, a bypass passage that bypasses this low pressure regulating valve, and a solenoid valve provided in this bypass passage. An air conditioner for an automobile according to claim 1, which is characterized in that: