JPH0559337B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a cooling system having a variable capacity compressor whose compression capacity is variable depending on the state of heat load and the rotational speed of the compressor. The present invention relates to a cooling system having a variable capacity compressor suitable for a vehicle air conditioner, which detects the refrigerant pressure at the outlet of an evaporator and switches the compression capacity of the variable capacity compressor in accordance with changes in the refrigerant pressure.

(Prior Art) Generally, in vehicle air conditioners, power from the engine is transmitted to the pulley of the compressor via a belt, and an electromagnetic clutch installed together with the pulley on the compressor is turned on and off. This controlled the operation of the compressor.

(Problem to be solved by the invention) However, in vehicle air conditioners, the rotation speed of the compressor is low when idling or driving at low speeds, resulting in insufficient cooling capacity; The cooling capacity becomes excessive. In order to respond to such changes in cooling capacity by turning the electromagnetic clutch on and off, the electromagnetic clutch has to be turned on and off frequently, which not only causes discomfort to the driver but also increases power loss.

The purpose of the present invention is to reduce the frequency of switching on and off of the electromagnetic clutch when the cooling load is below medium load.
It is an object of the present invention to provide an air-conditioning device that reduces discomfort caused to a driver, such as torque shock caused by turning on and off an electromagnetic clutch and fluctuations in evaporator outlet air temperature, and also saves energy.

(Means for Solving the Problems) According to the present invention, there is provided an air conditioner that cools a room by exchanging heat between a refrigerant sent from a compressor equipped with a variable compression capacity mechanism and indoor air using an evaporator. a pressure sensor for detecting the pressure of the refrigerant, which is provided on the refrigerant outlet pipe of the evaporator;
In the cooling device, the controller includes a controller that receives a pressure detected by the pressure sensor and controls a variable compression capacity mechanism for controlling the temperature in the room according to the detected pressure. The detected pressure detected from the start of the machine until the detected pressure reaches the set pressure (P ₀ ) is received from the pressure sensor, the rate of pressure change is calculated, and the calculated rate of pressure change is calculated in advance. Set setting change rate (α)
When the calculated pressure change rate is greater than or equal to the set change rate, a high upper limit pressure value (P ₁ ': However,
P ₁ ′<P ₀ ) and high lower limit pressure value (P ₂ ′: However, P ₂ ′<
P ₁ ′) is selected as the pressure control range, and when the calculated pressure change rate is smaller than the set change rate, the lower upper limit pressure value (P ₁ :
P ₂ ′<P ₁ <P ₁ ′) and low lower limit pressure value (P ₂ :However, P ₂
<P ₂ ′) is selected as the pressure control range, and the pressure detected by the pressure sensor drops to the lower limit pressure value (P ₂ ′ or P ₂ ) of the pressure range selected as the pressure control range. When the compressor is switched from large capacity to small capacity and the pressure detected by the pressure sensor rises to the upper limit pressure value (P ₁ ' or P ₁ ) of the pressure range selected as the pressure control range,
In order to switch the compressor from small capacity to large capacity,
A cooling device characterized in that the variable compression capacity mechanism is controlled is obtained. Thereby, the present invention
Turning on/off the electromagnetic clutch when the cooling load is below medium load.
By reducing the frequency of off-switching, it is possible to reduce the discomfort caused to the driver, such as torque shock and fluctuations in evaporator outlet air temperature due to on/off of the electromagnetic clutch, and to save energy.

(Example) Hereinafter, the present invention will be explained according to an example shown in the drawings.

FIG. 1 shows an embodiment of a vehicle air conditioner used in an embodiment of the control method of the present invention. The compressed gaseous refrigerant is sent to a condenser 3 of the refrigeration circuit, condensed, and sent to an evaporator 6 via a receiver dryer 4 and a throttle mechanism 5. The refrigerant, which has undergone heat exchange in the evaporator 6 and has become gaseous, is returned to the compressor 2 again. The variable capacity compressor 2 bypasses the inlet of the compressor 2 and the intermediate pressure port of the compression process, and includes a capacity switching mechanism 7 in the bypass circuit that is controlled by a solenoid valve (a piston valve, not shown). The compression capacity is now changed for the first time.

This capacity switching mechanism 7 is controlled by a controller 8, which will be described later.

The evaporator 6 is arranged within an air duct 9. Inside this air duct 9, a damper 10 and a heater 11 are arranged on the outlet side of the evaporator 6, and a blower 12 is arranged on the inlet side. It is sent into the vehicle interior through a damper 10 and a heater 11.

The heater 11 is provided with a hot water circuit connected to the engine 1, and hot water is supplied to the engine 1.
It circulates between.

A pressure sensor 13 is connected to the controller 8, which is installed in the outlet side piping of the evaporator 6 and detects the evaporator outlet refrigerant pressure P _E (hereinafter abbreviated as outlet pressure P _E ), and the detected value is sent to the controller. 8 is input.

Then, the controller 8 first calculates the rate of change from the start of the compressor 2 to the set pressure P ₀ (shown later), and compares it with the set rate of change to determine the first to fourth settings. Let the value be P ₁ ~ _{P 4} or P ₁ ′ ~
P ₄ ' or determine the control range and set the first set value P ₁
(P ₁ ′), second set value P ₂ (P ₂ ′), third set value P ₃ (P ₃ ′)
)
and the fourth set value P ₄ (P ₄ ′) and the evaporator outlet refrigerant pressure P _E detected by the pressure sensor 13 are compared, and the output signal thereof is transmitted to the capacity switching mechanism 7 and the clutch 14, It is designed to switch the capacity of the compressor 2, maintain the capacity, and turn the clutch on and off.

FIG. 2 shows a high load using the control device of the present invention.
This shows the capacity control state during medium speed running, and when the outlet pressure P _E is higher than the first set pressure P ₁ (P _E > P ₁ ), the capacity of the compressor 2 always maintains a large capacity, Further, when the outlet pressure P _E is lower than the second set pressure P ₂ (P _E <P ₂ ), a small capacity is always maintained.

Next, the control method of the present invention will be explained with reference to the flowchart shown in FIG.

After starting the variable capacity compressor 2, the compressor 2 maintains the small capacity for t ₁ seconds, and then switches to the large capacity.
Then, t _seconds after the start of the compressor 2, the pressure sensor 13 detects the outlet pressure P _E at several points (about 4 to 8 points) within an extremely short period of time (about 15 seconds to 30 seconds), and calculates the arithmetic average of the results. is calculated by the controller 8 and stored as P _E1 . Next, after another t _a seconds have elapsed, the arithmetic mean is set to P _E2 in the same way. Here, the controller 8 calculates the rate of change p/t of the pressure P _E with respect to time t. In this case, the rate of change p/t is p/t=(P _E1
−P _E2 )/t _a . From now on, after t _a seconds have elapsed, the average of the pressure P _E is detected in the same way, the rate of change p/t is calculated, and this process is repeated, but the controller 8 uses the previously calculated rate of change p/t. is deleted, and only the most recent value of rate of change p/t is stored. The above operations by the controller 8 control the pressure P _E
However, the set pressure P ₀ is set higher than the set pressure P ₁ ′.
is repeated until . Therefore, the rate of change p/t stored in the controller 8 indicates that the pressure P _E is the set pressure.
This is the value calculated just before reaching P ₀ .

Also, if the measured pressure P _Eo is higher than the previously measured P _E(o-1) , the pressure change rate obtained from these two points is canceled and the change rate obtained before is valid. becomes. In FIG. 2, which shows the pull-down state at high load and medium speed, the rate of change p/
Since t is smaller than the setting change rate α, the first and second
The set pressures are P ₁ , P ₂ , the third and fourth set pressures are P ₃ ,
It becomes P ₄ . In FIG. 2, after the variable capacity compression mechanism 2 is started, the indoor temperature decreases and the outlet pressure P _E of the evaporator 6 also decreases, reaching the second set pressure P ₂ and the capacity of the compressor becomes small. Thereafter, the capacity of the compressor becomes insufficient for the load, and the evaporator outlet pressure P _E rises and reaches the first set pressure P ₁ , and the capacity of the variable capacity compressor 2 becomes large again, so that the pressure P _E increases to the first set pressure P 1 . 2. Descend until the set pressure _P2 is reached.
Thereafter, such operations are repeated unless conditions such as the outside air condition and the rotation speed of the compressor change significantly.
FIG. 4 shows the capacity control state at medium load, where a indicates low speed to medium speed, and b indicates medium speed to high speed. Here, since the pressure change rate p/t obtained by the method described above is larger than the preset change rate α for both a and b, the first to fourth set pressures are P ₁ ′ and P ₂ ′, respectively. , P ₃ ′, P ₄ . In a,
Since the rotation speed of the compressor is low and the capacity of the compressor is insufficient for the load, when the second set pressure P ₂ ' is reached and the capacity of the compressor becomes small, the pressure P _E increases and the set pressure P ₁ '← Cycling (compressor capacity switching) is performed between →P ₂ ′. The dotted lines in Fig. 4 indicate the first and second set pressures P 1 and ₂ under the same conditions.
This is a control curve when cycling between P ₂ and P ₁ ←→P ₂ . In this case, the dotted line has a shorter cycle time than the solid line, that is, the compressor capacity is switched more frequently. Therefore, under light load conditions such as a medium load, the frequency of capacity switching of the compressor can be reduced by increasing the first and second set pressures.
Also, line b has a higher rotation speed of the compressor than line a, and the pressure is higher.
Even if P _E reaches the set pressure P ₂ ′, there is overcapacity and the pressure P _E decreases further, so when the set pressure P ₄ ′ is reached, the clutch breaks to prevent frost formation and from then on P ₃ ′←→P ₄ ′ Clutch cycling takes place in between. Here, the third and fourth set pressures are set to P ₃ ,
The pressures P ₃ ′ and P ₄ ′ are higher than P ₄ because the evaporator outlet air temperature is generally lower when the load is low than when the load is high. In this embodiment, the first to fourth set values were changed according to the rate of change p/t just before the evaporator outlet pressure P _E reached the set pressure P ₀ , but the evaporator outlet pressure P _E It is also possible to detect the average rate of change until the pressure reaches the set pressure _P0 , and change the first to fourth set values based on this rate of change.

Next, another embodiment will be described with reference to FIG.
In the embodiment described above, by detecting the rate of change in the refrigerant pressure at the outlet of the evaporator immediately before reaching the first set pressure during pulldown, the heat load at that time was estimated and the first to fourth set pressures were selected. In this example, in the process of cycling the compressor between high capacity and low capacity within the selected pressure control range, the time _tF for high capacity is measured using a timer and compared with a preset time. , the first to fourth set pressures (pressure control range) are changed. That is, under the conditions of cycling between the first set pressure and the second set pressure, the evaporator outlet refrigerant pressure P _E decreases after the compressor is started, but the second set pressure
When P ₂ ′ is reached, the capacity of the compressor is switched to a small one and the pressure P _E increases, and when P ₁ ′ is reached, the capacity of the compressor is increased and the pressure P _E is reduced. From then on, cycling between P ₁ ′←→P ₂ ′ will continue between large and small compressor capacity.Here, measure the time t for large compressor capacity, and if this is longer than the set time t _c ′, the pressure will increase. The control range is changed from the first and second set pressures P ₁ ' and P ₂ ' to smaller values P ₁ and P ₂ . In other words,
Under high load conditions, the time t _F during which the compressor's capacity is high is long, so the first and second set pressures are P ₁ and P ₂ when the load is high, and P ₁ ′ and P ₂ ′ (P ₁ ′＞P ₁ ,
P ₂ ′＞P ₂ ). Also, the first and second set pressures are
Even after changing to P ₁ and P ₂ , the time when the compressor capacity is high is measured and compared with the set value t _c , and if it is smaller, the first and second set pressures are returned to P ₁ ′ and P ₂ ′ again. It can respond to load changes after changing the set pressure.

Therefore, in this embodiment, the first and second set pressures can be changed according to changes in the load during cycling of the compressor, and more efficient operation can be achieved.

In addition, in this embodiment, if the compressor is switched from small capacity to large capacity whenever the air conditioner switch is turned on, the direct switching from the clutch off to the large capacity compressor, which has a large shock, will be completely eliminated, and the clutch will be switched off. The shock caused by turning on and off can be reduced.

Further, the variable capacity compressor of the present invention is not limited to the illustrated two-stage variable capacity compressor, but is equally effective even if the capacity is three or more stages. Furthermore, the selection of the first to fourth set pressures can be adjusted in conjunction with a room temperature control switch such as an air mix damper lever.

(Effects of the Invention) According to the present invention, it is possible to eliminate the need to start and stop a variable capacity compressor with a large shock when the capacity is large, and it is possible to operate the compressor smoothly according to the load. This has the effect of eliminating wasteful capacity switching and clutch on/off, enabling efficient operation, reducing evaporator outlet air temperature fluctuations, and saving energy.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a vehicle air conditioner according to the present invention, FIG. 2 is an explanatory diagram showing capacity control in high load and medium speed running according to the present invention, and FIG. 3 is a flow chart diagram of the present invention. FIG. 4 is an explanatory diagram showing capacity control at medium load according to the present invention, and FIG. 5 is an explanatory diagram showing capacity control according to another embodiment of the present invention. 1... Engine, 2... Variable capacity compressor, 3... Condenser, 4... Receiver dryer, 5... Throttle mechanism, 6... Evaporator, 7... Capacity switching mechanism,
8...Controller, 9...Air duct, 10...Damper,
11...Heater, 12...Blower, 13...Pressure sensor, 14...Clutch.

Claims (1)

[Scope of Claims] 1. A cooling device that cools a room by exchanging heat between a refrigerant sent from a compressor equipped with a variable compression capacity mechanism and indoor air using an evaporator, wherein a refrigerant outlet pipe of the evaporator is connected to a refrigerant outlet pipe of the evaporator. a pressure sensor that detects the pressure of the refrigerant, and a controller that receives the pressure detected by the pressure sensor and controls the variable compression capacity mechanism for controlling the temperature in the room according to the detected pressure. In the cooling device, the controller receives from the pressure sensor the detected pressure detected from the time the compressor is started until the detected pressure reaches the set pressure (P ₀ ), and adjusts the detected pressure. Calculate the rate of change, compare the calculated rate of pressure change with a preset rate of change, and if the calculated rate of pressure change is greater than the set rate of change, a high upper limit pressure value (P ₁ ': However, , P ₁ ′<P ₀ ) and a high lower limit pressure value (P ₂ ′: P ₂ ′<P ₁ ′) as the pressure control range, and the calculated pressure change rate is set as the above setting. When it is smaller than the rate of change, the lower upper limit pressure value (P ₁ : However, P ₂ ′<P ₁ <P ₁ ′)
and a low lower limit pressure value (P ₂ : However, P ₂ < P ₂ ′) as the pressure control range,
The pressure detected by the pressure sensor is the lower limit pressure value (P ₂ ′ or P ₂ ) of the pressure range selected as the pressure control range.
When the compressor is switched from large capacity to small capacity, and the pressure detected by the pressure sensor rises to the upper limit pressure value (P ₁ ' or P ₁ ) of the pressure range selected as the pressure control range, A cooling device characterized in that a variable compression capacity mechanism is controlled to switch the compressor from a small capacity to a large capacity. 2. In the cooling device according to claim 1, the controller detects the rate of pressure change at a plurality of points at certain time intervals, calculates the average value, and calculates the average value. A cooling device characterized by calculating a pressure change rate as a detection output.