JPH0154620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the operation of a variable capacity compressor, which is particularly suitable for vehicle air conditioning, and is capable of changing its working capacity depending on load conditions.

Conventionally, as a method for controlling the operation of a variable capacity compressor in a vehicle cooling system, a pressure sensor detects the pressure of refrigerant gas that is sucked into the compressor after heat exchange by an evaporator installed in a duct, that is, the suction gas pressure. However, if the suction gas pressure falls below the set value as the operating time passes,
There was one in which a capacity down signal was output from the controller to the capacity switching mechanism of the compressor. (Japanese Patent Application Laid-open No. 55-160187 by the same applicant) However, the above-mentioned control method has a limited capacity control range, so when the cooling capacity is excessive even with a small capacity such as dehumidification, the damper is opened and the heater is turned off. The defect was that the amount of heating by the engine was increased, which caused extra work to be done to heat up an area that was too cold, increasing power loss.

In addition, the applicant has recently proposed a control method in which the capacity is switched when the cabin temperature reaches a set value, but in addition to increasing the power loss mentioned above,
Since it is controlled independently of the evaporator temperature,
There was a risk of frost forming on the evaporator.

The purpose of the present invention is to reduce the temperature difference between the outlet air temperature of the evaporator, the temperature of the outlet air heated by a heating means such as a heater, and the outlet air temperature when the cooling load is large, or the temperature of the air in the cooling room. When one of the temperature differences between the temperature and the set cooling room temperature reaches the set value, the compressor capacity is switched and controlled in a large capacity range with high cooling capacity, and when the cooling load is small, the suction gas pressure and suction gas When any one of the temperature, the degree of superheating of the suction gas, the degree of superheating of the discharged gas, or the outlet air temperature reaches a set value, the capacity of the compressor is switched and controlled in a small capacity range with low cooling capacity. Variable capacity compression in air conditioners allows the compressor to be operated efficiently according to the load to reduce power loss, prevent evaporator frosting, and reduce the number of damper adjustments. The purpose of this invention is to provide a method for controlling the operation of a machine.

Hereinafter, first to fourth embodiments in which the present invention is embodied as an operation control method for a variable capacity compressor for vehicle air conditioning will be described with reference to the drawings.

First, a general overview of the vehicle cooling system used in the control method of each embodiment will be explained with reference to FIG. Therefore, in this embodiment, the operating capacity is set in four or more stages (for example,
The compressor uses a compressor that can switch capacity (two stages in a large capacity area and two stages in a small capacity area).

At the discharge flange 4 and suction flange 5 of the compressor 2, a condenser 6, which constitutes a refrigeration cycle, is installed.
A receiver 7, an expansion valve 8 and an evaporator 9 are connected in series.

On the other hand, inside the duct 10, a fan 11, the evaporator 9, a damper 12, and a heater 13 using the cooling water of the engine 1 are sequentially arranged. The temperature of the air blown out can be adjusted to a desired temperature.

Between the evaporator 9 and the damper 12, that is, at the outlet of the evaporator 9, the temperature of the air passing there (hereinafter referred to as the evaporator outlet air temperature Te)
A temperature sensor 15 is provided to detect the outlet temperature Te. This temperature sensor 15
A controller 16 is connected between the controller 16 and the capacity switching mechanism 3, and in this embodiment, a temperature comparison/discrimination circuit (not shown) of the controller 16 sets a predetermined set temperature Te2 (for example, 5° C. ) and temperature sensor 1
When the outlet air temperature Te of the evaporator 9 detected by 5 is compared with the outlet air temperature Te of the evaporator 9, and when the outlet temperature Te reaches the set value Te2, an operation circuit (not shown) of the controller 16 sends a signal to the capacity switching mechanism 3. On the other hand, a capacity down signal is output in a large capacity area, and conversely, the outlet temperature Te is a set value Te higher than the set value Te2.
1 (for example, 10℃), the capacity switching mechanism 3
In contrast, a capacity up signal is output in the large capacity area.

The temperature of the air passing through the outlet 14 of the duct 10 (hereinafter referred to as the duct outlet air temperature Tf
A temperature sensor 17 is arranged to detect the temperature (or simply referred to as the blowout temperature Tf), and this temperature sensor 17
The signal detected by
A predetermined set temperature difference △Tfe2 (for example, 5°C) is compared and determined, and when the temperature difference △Tfe reaches the set value △Tfe2, the controller 16 outputs a capacity down signal in the large capacity area, and vice versa. When the set value ΔTfe1 (for example, 3° C.) is smaller than the set value ΔTfe2, a capacity up signal is output in the large capacity region.

On the other hand, a temperature sensor 18 for detecting the cabin air temperature Tr (hereinafter simply referred to as cabin temperature Tr) is installed at an appropriate location in the cabin that is not exposed to direct sunlight, wind, etc.
The signal detected by this temperature sensor 18 is input to the controller 16, and the comparison circuit of the controller compares the temperature with the preset cabin temperature Tc (for example, 25°C). When the difference △Trc reaches the set temperature difference △Trc2 (for example, 2°C), the controller 16 outputs a capacity down signal in the large capacity range, and conversely, the set value △Trc1 (for example, 5°C), a capacity up signal is output in the large capacity range.

Furthermore, a pressure sensor 19 and a temperature sensor 20 are provided in the middle of the pipe connecting the evaporator 9 and the suction flange 5 to detect the pressure and temperature of the gas sucked into the compressor. The suction gas pressure Ps detected by the pressure sensor 19 is input to the controller 16, and when the same pressure Ps reaches a set pressure Ps2 (for example, 0.5 Kg/cm) preset by the comparison/discrimination circuit of the controller 16, The controller 16 outputs a capacity down signal in the small capacity area, and conversely outputs a set value Ps1 larger than the set value Ps2 (for example, 3Kg/
cm), a capacity up signal is output in the small capacity range. Similarly, the temperature sensor 20
The intake gas temperature Ts detected by is the set temperature Ts
2 (for example, 0°C), the controller 16 outputs a small capacity down signal, and conversely, the set value
When the set value Ts1 (for example, 10° C.) is greater than Ts2, a capacitance up signal is output in the small capacitance region.

Furthermore, the controller 16 controls the suction gas temperature.
Degree of superheating at the suction state point in the Mollier (P-i) diagram determined by Ts and suction gas pressure Ps
When Tsh reaches the set superheat degree Tsh2 (for example, 5°C) stored in advance by the controller 16, the controller 16 outputs a capacity down signal in the small capacity range, and conversely, the set value Tsh2 is set higher than the set value Tsh2. Value Tsh1
(for example, 15°C), it has a function to output a capacity up signal in a small capacity range. moreover,
The controller 16 stores the discharge gas pressure Pd and temperature Td detected by a pressure/temperature sensor (not shown) connected to the pipe connecting the discharge flange 4 and the condenser 6, as well as the superheat degree Tsh in the suction state described above. The degree of superheating Tdh at the discharge state point determined by is the set value Tdh2,
It has a function to output a capacity down (up) signal in a small capacity area when Tdh1.

Next, a first embodiment of the control method of the present invention will be described with reference to FIG. 2 based on the vehicle cooling system configured as described above.

This embodiment shows a case where the controller 16 determines that the outlet temperature Te and the suction gas pressure Ps have reached predetermined set values. Specifically, when the cooling load is large, the outlet temperature Te and The compressor is switched and controlled alternately in a large capacity range using set values Te1 and Te2, and when the cooling load is small, the compressor is switched and controlled in a small capacity range using the suction gas pressure Ps and set values Ps1 and Ps2. .

Now, when the electromagnetic clutch is turned on by a start switch (not shown) of the air conditioner, the compressor is driven at full capacity. The compressed refrigerant gas discharged from the discharge flange 4 is sent to the evaporator 9 via the condenser 6, the receiver 7 and the expansion valve 8, where it is heat exchanged with the air forcibly transferred by the fan 11. It is sucked into the compressor through the suction flange 5. The outlet temperature Te of the evaporator 9 gradually decreases as the operating time h passes, but when the clutch is turned on, the compressor
For a while after 100% operation, the temperature inside the vehicle is still high, so the cooling load is large and heat exchange is performed efficiently, causing the outlet temperature Te to drop rapidly.
After that, as the operating time passes, the temperature inside the vehicle decreases and the heat exchange efficiency decreases, and the outlet temperature increases.
The decline in Te also becomes gradual, and the same exit temperature Te
When it reaches the set value Te2, the controller 16 outputs a capacity down signal, and the capacity switching mechanism 3 reduces the capacity of the compressor in the large capacity range.

Even if the capacity is reduced in this way, if the cooling capacity of the compressor is somewhat large, the outlet temperature Te and the suction gas pressure Ps will gradually drop as shown by the solid line in Figure 2, and when the pressure Ps reaches the set value Ps2. A capacity down signal is output from the controller 16 at a small capacity, and the compressor is operated at the minimum capacity. After that, the cabin temperature rises and the outlet temperature Te and intake gas pressure Ps rise, and when this pressure Ps reaches the set value Ps1, the capacity is increased in the small capacity range, but the outlet temperature Te remains at the set value.
Since it is lower than Te1, the compressor is operated in the capacity up state in the small capacity range, and after that, the set value Ps2,
Ps1 alternately raises and lowers the capacity in the small capacity area.

On the other hand, if the compressor is in a capacity-up state in the small capacity range and the cooling capacity is insufficient, the outlet temperature Te and suction pressure Ps will rise, as shown by the two-dot chain line in Figure 2.
When the temperature Te reaches the set value Te1, a capacity up signal is output from the controller 16, and switching control is performed to a capacity down state in the large capacity range. After that, the set value Te2,
Capacity switching in the large capacity area is performed alternately by Te1.

In this way, in the first embodiment of the present invention, when the cooling load is small, the suction pressure Ps and the set value Ps
1. Ps2 is used to control the capacity of the compressor alternately in the small capacity range, so the extra work of overheating the cold is reduced, the compressor is operated in an efficient state, and the power is increased. Loss can be reduced, and the suction gas pressure passing through the evaporator 9 can be reduced.
Since Ps is detected, the capacity of the compressor can be minimized to prevent frosting before the temperature of the evaporator drops below 0°C.

Further, after the cabin temperature reaches a temperature suitable for the passengers and the cooling load becomes small, the damper 12 is rotated to increase the amount of heating by the heater 13 in order to prevent excessive cooling. In this case, the outlet temperature can be controlled by switching the compressor in a small capacity range using the suction gas pressure Ps, regardless of the outlet temperature Te.
The blowout temperature Tf is set by setting Te higher than the set value Te2.
The temperature difference ΔTfe between the output temperature Te and the outlet temperature Te can be made smaller, and therefore, it is easier to adjust the cabin temperature by adjusting the damper, and the number of times the damper needs to be adjusted can be reduced.

In this first embodiment, in the case of gas shortage, the cooling capacity of the evaporator is reduced and the outlet temperature Te is higher than the set value Te2, resulting in large capacity operation, so the way the suction gas pressure Ps decreases is As a result, there is an advantage that gas shortage can be easily detected by detecting an abnormal drop in the same pressure Ps. This means that the degree of superheating of the suction gas is determined by the suction gas pressure Ps and the suction gas temperature Ts.
This also applies to the fourth embodiment described later in which the compressor is switched and controlled in a small capacity range using Tsh, and in this case, gas shortage can be detected by detecting an abnormal increase in the degree of superheat Tsh.

Next, a second embodiment of the control method of the present invention will be described with reference to FIG.

This embodiment shows a case where the controller 16 determines that the temperature difference △Tfe between the outlet temperature Tf and the outlet temperature Te and the suction gas temperature Ts have reached preset values. When the load is large, the compressor is controlled to switch capacity in a large capacity range using the temperature difference △Tfe between the outlet temperature Tf and the outlet temperature Te and the set values △Tfe1, △Tfe2, and when the cooling load is small, the intake gas temperature Ts and the setting are controlled. The values Ts1 and Ts2 are used to control capacity switching in a small capacity range. Since the damper 12 is closed at the beginning of operation when the cooling load is large, the temperature difference ΔTfe is small, and the suction temperature Ts is also high, so the compressor is operated in an increased capacity state in the large capacity range. When cooling progresses and the cabin temperature reaches an appropriate temperature, the damper 12 is opened to prevent excessive cooling, and a portion of the air is heated by the heater 13 to raise the blowout temperature Tf. Then, the temperature difference △Tfe increases, and this becomes the set value △Tfe2
When this happens, the compressor is switched to a reduced capacity state in the large capacity range, and the cooling capacity is reduced.

If the cooling capacity is slightly excessive even when the compressor is switched to the capacity down state in the large capacity range, the suction temperature Ts will drop as shown by the solid line in Figure 3, and when this temperature Ts reaches the set value Ts2, the control will start. The compressor 16 outputs a signal for switching to a capacity down state in the small capacity region, and the compressor is operated at the minimum capacity. Then the suction temperature
When Ts increases to the set value Ts1, the controller 16
A capacity up signal is output in the small capacity area, but
Since the temperature difference ΔTfe has not reached the set value ΔTfe1, the compressor is operated in a capacity-up state in the small capacity range. Thereafter, similarly, the capacity switching control in the small capacity region of the compressor is performed alternately using the set values Ts1 and Ts2.

On the other hand, the capacity of the compressor has been increased in the small capacity range, but when the cooling capacity is insufficient, the third
As shown by the two-dot chain line in the figure, the outlet temperature Te increases and the temperature difference △Tfe becomes smaller. When △Tfe reaches the set value △Tfe1, a capacity up signal is output from the controller 16, and the compressor has a large capacity. The area is switched to capacity up state. Similarly, the setting value △Tfe2,
Capacity switching is performed alternately in the large capacity region by ΔTfe1.

In this way, in the second embodiment of the present invention, when the cooling load is small, the suction temperature Ts and the set value Ts
2. Since the capacity of the compressor is controlled by Ts1 in a small capacity range, power loss can be reduced as in the first embodiment, the number of damper adjustments can be reduced, and the evaporator can prevent frosting.

Next, a third embodiment of the control method of the present invention will be described with reference to FIG.

In this embodiment, the capacity switching of the compressor is controlled in a large capacity range based on the temperature △Trc of the cabin temperature Tr and the set temperature Tc, and the capacity switching of the compressor is controlled in a small capacity range based on the intake gas temperature Ts. The compressor is operated at full capacity in the early stages of cooling when the temperature difference △Trc is large, and when the temperature difference △Trc becomes smaller and becomes less than the set value △Trc2 as the cooling progresses, the controller 16
A capacity down signal in the large capacity area is output from the compressor, and the compressor is operated in a capacity down state in the large capacity area.
In this state, if the cooling capacity is slightly large, the fourth
As shown by the solid line in the diagram, the cabin temperature Tr and the intake gas temperature Ts gradually decrease, and when the intake gas temperature Ts reaches the set value Ts2, the controller 16 outputs a switching signal to the capacity down state in the small capacity range. The compressor is operated at minimum capacity. Then the suction gas temperature Ts
increases and reaches the set value Ts1, the temperature difference △Trc has not reached the set value △Trc1, so the compressor is operated in a capacity-up state in the small capacity range, and from then on the set value
Capacity switching control in the small capacity region is performed alternately by Ts1 and Ts2.

On the other hand, if the cabin temperature TR decreases and the compressor is in a capacity-up state in the small capacity range and the cooling capacity is insufficient, the cabin temperature Tr will gradually rise and the temperature will decrease as shown by the two-dot chain line in Figure 4. When the difference △Trc reaches the set value △Trc1, the compressor is switched to the capacity up state in the large capacity range, and thereafter, the capacity is switched in the large capacity range by the set values △Trc1 and △Trc2, regardless of the suction gas temperature Ts. are performed alternately.

This third embodiment shows a case where the controller 16 determines that the cabin temperature Tr and the intake gas temperature Ts have reached preset values. Specifically, the cabin temperature Tr and the set temperature are determined by the controller 16. The temperature difference △Trc in Tc controls the capacity down or up in the large capacity range, while the intake gas temperature Ts controls the capacity down or up in the small capacity range. (not shown) to set cabin temperature Tc or set value △Trc1, △Trc
This embodiment has a feature that the temperature of the vehicle interior can be easily adjusted by changing the temperature of the vehicle, but other effects are the same as those of the first embodiment.

Next, a fourth embodiment of the control method of the present invention will be described with reference to FIG.

This embodiment shows a case where the controller 16 determines that the outlet temperature Te and the suction gas superheat degree Tsh have reached preset values. Specifically, the outlet temperature Te and the set value Te1, Capacity switching is performed in a large capacity range using Te2, and the superheat degree of suction gas is
Capacity switching is controlled in a small capacity area using Tsh and set values Tsh1 and Tsh2. When the cooling operation is started and the outlet temperature Te decreases to the set value Te2, the state is switched from full capacity to a reduced capacity state in the large capacity range. If the cooling capacity is large in this state, the outlet temperature Te and superheat degree Tsh will decrease, and Tsh will be the set value.
When Tsh2 is reached, the state is switched to a capacity down state in the small capacity range, and the compressor is operated at the minimum capacity. Thereafter, when the degree of superheat Tsh increases and reaches the set value Tsh1, the compressor is switched to a capacity up state in a small capacity range. Thereafter, capacity switching control is performed in the small capacity area using the set values Tsh1 and Tsh2.

On the other hand, when the cooling capacity is insufficient in the increased capacity state in the small capacity region, the outlet temperature Te rises as shown by the two-dot chain line in Figure 5, and when it reaches the set value Te1, the compressor enters the increased capacity state in the large capacity region. The capacitance is switched, and the capacitance is alternately switched between large capacitances and the subsequent set values Te1 and Te2.

The effects of this fourth embodiment are also similar to those of the first embodiment.

In each of the above-mentioned embodiments, when the cooling load is large, a specific one of the outlet temperature Te, the temperature difference △Tfe between the outlet temperature Tf and the outlet temperature Te, and the temperature difference Trc between the cabin temperature Tr and the set temperature Tc is This indicates a case where it is determined that one has reached a preset value set by the controller 16, and when the cooling load is small, one of the suction gas pressure Ps, suction gas temperature Ts, and suction gas superheat degree Tsh Although the case is shown in which it is determined that a specific one has become a preset value by the controller 16, the present invention is not limited to the combinations of the above-mentioned embodiments, and can be applied to any combination. is possible. This is because, among the measured values of ~ and ~ mentioned above, which value becomes the preset set value varies depending on the operating conditions of the compressor. This is because it changes arbitrarily.

As described in detail above, the present invention allows fine-grained control to be performed accurately, so the compressor can be efficiently operated according to the cooling load to reduce power loss, and the evaporator frost can be reduced. This has the effect of being able to prevent this and further reduce the number of times the damper needs to be adjusted.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing an embodiment of a cooling device used in the control method of the present invention for vehicle air conditioning, and FIGS. 2 to 5 are the first embodiment of the control method of the present invention. - It is a graph explaining a fourth example. Variable capacity compressor...2, Capacity switching mechanism...3,
Heater...13, Temperature sensor...15, 17, 1
8, 20, Controller...16, Pressure sensor...1
9. Evaporator outlet air temperature...Te, duct outlet air temperature...Tf, vehicle interior air temperature...
Tr, set cabin temperature...Tc, intake gas pressure...
Ps, temperature...Ts, discharge gas pressure...Pd, temperature...
...Td, degree of superheating of intake (discharge) gas...Tsh,
Tdh, temperature difference...△Tfe, △Trc, set temperature...
Te1, Te2, Ts1, Ts2, set pressure...Ps1,
Ps2, set temperature difference...△Tfe1, △Tfe2, △
Trc1, △Trc2.

Claims (1)

[Scope of Claims] 1 Compressed gas is sent to the refrigeration cycle from a variable capacity compressor whose capacity, or cooling capacity, can be switched and adjusted according to the cooling load using a capacity switching mechanism to perform a cooling action, and then heat exchange is completed. In the cooling method in which the compressed gas is sucked into the compressor again, the temperature difference ΔTfe between the outlet air temperature Te of the evaporator and the outlet air temperature Tf of the duct heated by a heating means such as a heater is Tfe. Indoor air temperature Tr and set indoor air temperature
Temperature difference ΔTrc of Tc The above ~ and this ~ are compared and determined by a preset value corresponding to each ~, and when any one of the ~ above reaches the set value, the operating means causes the above capacitance to be determined. The switching mechanism is operated to switch and control the capacity of the compressor in a large capacity range with high cooling capacity, and the suction gas pressure Ps of the compressor and the suction gas temperature Ts of the compressor are determined by the suction gas pressure Ps and temperature Ts. Degree of superheating of the suction gas Tsh Degree of superheating of the discharged gas determined by the discharge gas pressure Pd and discharge gas temperature ΔTd of the compressor
Tdh Evaporator outlet air temperature Te The above ~ and this ~ are respectively compared and determined by a preset set value, and when any one of the ~ above reaches the set value, the operating means A method for controlling the operation of a variable capacity compressor in a cooling device, characterized in that the capacity switching mechanism is actuated to control the capacity of the compressor in a small capacity range where cooling capacity is low.