JPH08291945A - Method for controlling screw heat pump - Google Patents

Abstract

PURPOSE: To provide a method for controlling a screw heat pump in which a changing-over of a four-way valve can be performed surely when a power source is recovered after its power failure. CONSTITUTION: This invention relates to a method for controlling a screw heat pump comprised of a screw compressor 1, a water heat exchanger 2, an air heat exchanger 3 and a solenoid valve type four-way valve 4, means 7 for connecting these elements with a pipe to form a circuit and for sensing a pressure difference in the circuit, means for discriminating if the pressure difference can change-over the solenoid valve type four-way valve and means 6 for storing it. A control after recovery of the power source in the case that a power failure occurs under a state of ON (a heating cycle) of the solenoid valve type four-way valve is performed like (a) the solenoid valve type four-way valve is OFF in the case that the pressure difference occurs before power failure and there is no pressure difference after recovery of the power source, (b) the solenoid valve type four-way valve is ON in the case that there is a pressure difference before power failure and there is also a pressure difference after recovery of the power source, and (c) the solenoid valve type four-way valve is ON in the case that there is no pressure difference before power failure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a screw heat pump, and more particularly to a method for controlling a four-way valve for switching a refrigerant flow path after a power failure of the screw heat pump is restored.

[0002]

2. Description of the Related Art Conventionally, in a screw heat pump for cooling and heating by compressing a refrigerant with a screw compressor,
It had a four-way valve for switching the refrigerant flow path, and switching of the four-way valve was performed by outputting a switching signal depending on whether it was in the cooling or heating mode. That is, the cooling / heating signal is simply input and the ON / OFF signals are sent to the four-way switching valve according to the signal. However, the four-way valve has a problem that it stops at the intermediate position and does not operate when the pressure at the time of switching the four-way valve is small or when the pressure rises halfway. There is a drawback that causes problems.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a screw heat pump control method capable of reliably switching a four-way valve when power is restored after a power failure. .

[0004]

In order to solve the above problems, the present invention provides a screw compressor, a water heat exchanger, an air heat exchanger, a solenoid valve type four-way valve, and a circuit in which they are connected by piping. Method for controlling a screw heat pump having means for forming a pressure difference in the circuit, means for determining whether or not the pressure difference can switch a solenoid valve type four-way valve, and means for storing it The solenoid valve type four-way valve is ON
Control after power restoration in case of power failure in the state of (heating cycle): (a) If there is a pressure difference before power failure and there is no pressure difference after power restoration, turn off the solenoid valve four-way valve,
(B) If there is a pressure difference before the power failure and after the power is restored, turn on the solenoid valve type four-way valve, and (c) If there is no pressure difference before the power failure, turn on the solenoid valve type four-way valve. That is what I decided to do. In the above control method, the means for detecting the pressure difference does not detect the circuit directly, but the hot water temperature after the power failure, the compressor operation signal before the power failure, the compressor current signal, the compressor discharge side temperature and the suction side temperature. Either the temperature difference or the compressor discharge gas temperature can be detected and used as a substitute.

[0005]

In the present invention, it is estimated how the four-way valve moves (in the cooling cycle or the heating cycle) at the time of a power failure, and after the power is restored, the pressure difference and the position of the valve are controlled as elements. As a result, it is possible to reliably switch the four-way valve.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings, but the present invention is not limited thereto. Example 1 FIG. 1 shows a schematic configuration diagram of a heat pump of the present invention, and a cooling and heating cycle will be described with this. In FIG. 1, 1 is a screw compressor, 2 is a water heat exchanger, 3 is an air heat exchanger (coil), 4 is a four-way valve, 5 is piping, 6 is a control device, 7 is a pressure difference detector, In the conventional device, the pressure difference detector 7 is not installed, and the provision of this is a feature of the present invention.

In the cooling cycle, the refrigerant discharge gas from the screw compressor 1 radiates heat to the outside air in the air heat exchanger 3 via the four-way valve 4, is condensed and becomes a liquid, and in the water heat exchanger 2. Evaporate to make cold water for cooling. The evaporated refrigerant gas is sucked into the screw compressor 1 via the four-way valve 4 to form a cooling cycle. On the other hand, in the heating cycle, the refrigerant flow path is switched by the four-way valve 4, and the refrigerant discharge gas from the screw compressor 1 is condensed in the water heat exchanger 2 via the four-way valve 4 to produce hot water for heating. The condensed refrigerant liquid absorbs heat from the outside air in the air heat exchanger 3 and evaporates, and the evaporated refrigerant gas is sucked into the screw compressor 1 via the four-way valve 4 to form a heating cycle.

A control device 6 stores a signal from the pressure difference detector 7, stores a cooling / heating signal, and sends the signal to the four-way switching valve. The drive system of the four-way valve here is a solenoid valve system, and the valve is a pilot system of the piston type which is operated by utilizing the high and low pressure difference in the circuit. Then, the following description will be made assuming that: cooling: electromagnetic valve OFF, heating: electromagnetic valve ON. First, during cooling with the solenoid valve turned off, there is no problem even if a power failure occurs. Originally, since it is OFF, it remains the same whether there is a differential pressure or not.

The heating operation in which the solenoid valve is turned on is effective in the present invention. That is, Case 1: There is a pressure difference (generally during operation)
In case of power failure in this case, the four-way valve operates during the power failure and turns off.
Becomes That is, it switches to the cooling cycle. Case 2: Power outage in the absence of differential pressure (generally stopped) In this case, the four-way valve does not operate during the power outage. That is, the heating cycle remains.

Next, when the power is restored, the four-way valve solenoid valve is controlled according to the above case. First, before and after a power failure, it is always judged and stored in case 1 or 2 and after a power failure recovery, a) Before a power failure In case 1 After a power failure recovery, immediately turn on if there is a pressure difference. b) Before power failure After the power failure is restored in Case 1, if there is no pressure difference, leave it OFF and turn it ON when the pressure difference occurs. c) Before power failure Case 2 O immediately after power failure recovery
N By controlling in this way, it is possible to reliably prevent malfunction of the four-way valve when switching.

FIG. 2 is a flow chart showing the control contents of the invention. Usually, if the power supply of the four-way valve and the power supply of the control device are the same, the power failure and the power supply restoration are the start-up of the power supply.
At the initial start, it can be regarded as a recovery from a power failure.
As a means for detecting the pressure difference, there is a differential pressure transmitter,
Since the cost is high, it can be substituted by others. As alternative means, there are any one of hot water temperature after power failure, compressor operation signal before compressor failure, compressor current signal, temperature difference between compressor discharge side temperature and suction side temperature, detection of compressor discharge gas temperature, etc. Can be used. The working pressure difference varies depending on the four-way valve used, but is typically in the range of 3.5 to 20 kg / cm ² . The compressor is not limited to the screw compressor.

[0012]

As described in detail above, according to the present invention,
It is possible to provide a screw heat pump having no malfunction of the four-way valve after the power failure is restored.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a heat pump of the present invention.

FIG. 2 is a control flow chart showing the control content of the present invention.

[Explanation of symbols]

1: Screw compressor, 2: Water heat exchanger, 3: Air heat exchanger (coil), 4: Four-way valve, 5: Piping, 6: Control device, 7: Pressure difference detector

Claims (3)

[Claims] 1. A screw compressor, a water heat exchanger, an air heat exchanger, a solenoid valve type four-way valve, and means for detecting the pressure difference in the circuit by connecting them with a pipe to form a circuit. In a method of controlling a screw heat pump having means for determining whether or not the difference is a solenoid valve type four-way valve switchable, and means for storing the difference, a solenoid valve type four-way valve is in an ON (heating cycle) state. If there is a pressure difference before the power failure and there is no pressure difference after the power failure, the solenoid valve type four-way valve is turned off, and (b) the pressure difference before the power failure occurs. Yes, if there is a pressure difference after the power is restored, the solenoid valve type four-way valve is turned on. (C) If there is no pressure difference before the power failure, the solenoid valve type four-way valve is turned on. Heat pump control method. 2. The method for controlling a screw heat pump according to claim 1, wherein the means for detecting the pressure difference after the power failure is hot water temperature. 3. A means for detecting a pressure difference before a power failure detects one of a compressor operating signal, a compressor current signal, a temperature difference between a compressor discharge side temperature and a compressor side temperature, or a compressor discharge gas temperature. The method of controlling the screw heat pump according to claim 1, wherein