JPH0144946B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a flow rate control device.

There are various devices that require flow rate control, one example of which is a refrigerator. Refrigerators use a compressor to pressurize a gas (refrigerant) such as Freon gas, liquefy it by water or air cooling, and then put it into a regulator to bring it to the required low pressure and vaporize it in a vaporizer. Cooling is performed by transferring heat, and in order to control this cooling temperature, a valve generally called an automatic expansion valve is installed between the regulator and the vaporizer to control the flow rate of refrigerant to the vaporizer. is provided. Conventionally, such automatic expansion valves include temperature (self-powered) type, bimetallic type, electromagnetic proportional type, and the like.

However, thermostatic automatic expansion valves detect the evaporation pressure and suction superheat of the flowing refrigerant and operate on their own depending on the superheat to control the amount of refrigerant based on these. Since it is not possible to increase or decrease the flow rate depending on other factors such as Since the time constant of is made large, there is a drawback that there is a delay in tracking during transient times such as during startup, and liquid return is likely to occur.

A bimetallic automatic expansion valve is a valve that is directly operated by a bimetal that is heated by a heater.The valve drive unit operates slowly and takes a long time to operate, so it is suitable for devices that fluctuate, such as car air conditioners. The position of the valve is likely to fluctuate depending on the temperature of the location where the heater is installed or the presence or absence of refrigerant, and the opening degree of the valve relative to the applied voltage must be set in advance with considerable accuracy. There are drawbacks such as.

Finally, an electromagnetic proportional automatic expansion valve is a valve that maintains a predetermined opening degree by balancing the attraction force of a coil that is proportional to the applied voltage and the load of a spring that resists this. Even if the degree is set in advance with considerable accuracy, the load due to the pressure difference between the liquid before and after the valve is added to the above load, so changes in this pressure difference will cause the valve opening degree to fluctuate or deviate. Continuing to apply electricity causes the temperature of the coil to rise, which reduces the suction force, resulting in drawbacks such as fluctuations in the opening degree of the valve.

As mentioned above, all conventional automatic expansion valves control the flow rate of refrigerant by controlling the opening degree of the valve, so they require small-capacity refrigerant control, such as in refrigerators, and Reynolds For products that require fluid control in a small number of locations, there is a problem that even if the valve position is maintained at a certain location, the flow rate changes due to changes in fluid viscosity and cannot be controlled. .

The present invention has been made in view of the above points, and
The purpose is to provide a new flow rate control device that solves the problems of conventional flow control based on the opening degree of a valve.

The flow rate control device according to the present invention does not control the flow rate by the opening degree of the valve, but by the opening time of the valve. The flow rate of the fluid passing through the solenoid valve is controlled by applying a periodic pulse and changing the width of this pulse to change the ON time of the solenoid valve, and the solenoid valve a plunger that reciprocates in a direction, a valve body protruding from a surface of the plunger facing the valve port and biased by a spring in the direction of the valve port; and a cushion member protruding from the cushion member.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram of a refrigerator in which the flow rate of refrigerant is controlled by the flow rate control device according to the present invention.
In the figure, 1 is a compressor that makes the refrigerant high pressure and liquefies it by water cooling or air cooling, 2 is a regulator that brings the liquefied refrigerant to the required low pressure, and 3 is a vaporizer that vaporizes the refrigerant and takes the heat of vaporization from the surroundings. , 4 is regulator 2 and vaporizer 3
This is an automatic expansion valve that is installed between the vaporizer 3 and the vaporizer 3 and controls the flow rate of the refrigerant to the vaporizer 3.

The automatic expansion valve 4 is composed of a solenoid valve that is fully opened and fully closed by pulses that can be very commonly obtained by an electronic circuit. A pulse with a constant T is applied, and the full opening time of the valve is controlled by the width of the pulse. Figures 2a to 2c show the flow rate of refrigerant passing through the solenoid valve 4 at 90% of its allowable flow rate.
%, 550% and 10%, the pulses applied to the solenoid valve 4 are shown, and the width of each pulse is τ ₁ , τ ₂ , respectively.
Denoted by τ ₃ .

In general, in a refrigerator, the cooling temperature is proportional to the amount of refrigerant supplied to the vaporizer 3 as well as the temperature difference between the input and output of the vaporizer 3, that is, the degree of superheating. By controlling the flow rate of the refrigerant passing through the electromagnetic valve 4, a predetermined cooling temperature can be obtained.

The other parts of the refrigerator shown in Figure 1 are for generating the pulses that need to be applied to the solenoid valve 4 in order to control the flow rate of the refrigerant with the solenoid valve 4 so that the degree of superheat is at the set value. , 5 is a temperature sensor for detecting the inlet temperature of the vaporizer 3, 6 is a temperature sensor for detecting the outlet temperature of the vaporizer 4, 7 is an oscillator, 8 is a pulse generator, 9 is a driver, and 10 is a calculation section. The outputs of the temperature sensors 5 and 6 are input to an arithmetic unit 10 to which a set value of the degree of superheat is applied, and the output of the arithmetic unit 10 is input to a pulse generator 8 to which an oscillation output of an oscillator 7 is applied. The driver 9 turns the solenoid valve 4 on and off based on the pulses generated by the pulse generator 8.

More specifically, the calculation unit 10 and the pulse generator 8
is configured as shown in FIG.
is a summing point 10 that generates a voltage corresponding to the temperature difference between the input and output based on the signals from the temperature sensors 5 and 6.
a, a summing point 10b for determining the deviation between the output signal of this summing point 10a and the set value of the degree of superheat;
It consists of an integrator 10c that integrates the output signal of this summing point 10b over time. The pulse generator 8 is
It consists of a comparator 8a that compares the output signal of the integrator 10c and the signal from the oscillator 7 and generates a pulse in which the output signal from the integrator 10c is at a high level for a period of time when it is greater.

Now, when the output of the oscillator 7 is a triangular wave as shown in FIG. 4a, and the output of the integrator 10c gradually increases as shown in FIG. 4b, the output of the pulse generator 8 has a diagonal line shown in FIG. As shown with , a pulse train whose pulse width gradually increases is generated. In the example shown in the figure, the output of the integrator 10c gradually increases when the actual degree of superheating becomes smaller than the set value + a deviation appears, and control is performed to widen the pulse width and increase the flow rate of refrigerant to the vaporizer 3. When the deviation is ±0, the integrator 1
Since the output of 0c maintains a constant level, a pulse train with a pulse width corresponding to the level is generated, and when there is a deviation, the integrator 1
The output of 0c gradually decreases, and a pulse train whose pulse width gradually becomes smaller is generated.

In short, this valve is controlled by pulse width, making it easier to control the speed of increase/decrease in flow rate and to improve resolution compared to other methods, so unlike a vaporizer, there is a long dead time and the flow rate is changed gradually. This makes it suitable for controlling the flow rate to what is necessary for system stability. Therefore, depending on the magnitude of the actual degree of superheat relative to the set degree of superheat, the valve opening time is gradually decreased or increased until the actual degree of superheat reaches the set value, and when the actual degree of superheat reaches the set value, Control is performed to maintain the valve opening time.

The solenoid valve used in the above-mentioned flow control device is
Due to its control characteristics, the number of on/off operations per unit time is greater than that of ordinary solenoid valves, so it is necessary to take measures such as improving durability and reducing operating noise.

FIG. 5 shows an embodiment of a solenoid valve with the above-mentioned device, and in the figure, 20 is a U-shaped outer cover made of magnetic material, and between the opposing pieces of this outer cover 20, a flange is attached. An electromagnetic coil 22 wound around a hollow bobbin 21 is held therebetween. Reference numeral 23 designates a plunger tube having a suction element 24 fixed to one end inserted into the hollow part of the bobbin 21 and a valve seat 25 fixed to the other end protruding from the hollow part of the bobbin 21. It is fixed to the outer case 20 by fastening 26.

The valve seat 25 is connected to an inlet pipe 27 and an outlet pipe 28, and is provided with an orifice 29 at the boundary with the outlet pipe 28, which serves as a valve port.

30 is a tubular plunger made of magnetic material;
It is slidably housed in the plunger tube 23, and a piston ring 31 is fitted around the outer periphery of the piston ring 31 to reduce sliding resistance between the outer periphery of the plunger 30 and the plunger tube 23. Circumferential grooves 30a and 30b are provided at both ends of the inner circumferential wall of the plunger 30, respectively, and
The hollow portion has flanges 32a and 33a that engage with the circumferential grooves 30a and 30b, respectively, into which a valve body 32 and cushion material 33 made of a soft material such as Teflon are fitted. Also accommodated in the hollow portion of the plunger 30 is a loaded coil spring 34 that is compressed between the valve body 32 and the cushion material 33. As described above, the end surfaces of the valve body 32 and the cushion material 33 provided at both ends of the plunger 30 are slightly protruded from the end surfaces of the plunger 30 and are connected to the valve port 29 and the suction element 2.
4 are facing each other.

In addition, 35 is a lead wire for supplying pulse current to the electromagnetic coil 22, and FIG. 5 shows the lead wire 35.
A pulse current is applied to excite the coil 22, so that the plunger 30 is attracted by the attractor and the valve body 32 is separated from the valve port 29, indicating a fully open state of the valve.

The operation of the solenoid valve configured as described above is shown in Figs. 6a to 6c.
Explain with reference to.

Figure 6a shows the valve closed state; in this state,
The spring 34 is compressed to the point where the force due to the plunger 30's own weight and the force of the spring 34 are balanced, and the valve body 32 and the plunger 30 are relatively moved by a distance _L1 . When the coil 22 is energized in this state, the plunger 30 is attracted by the attractor 24, but at this time, no load is applied to the plunger 30 during L ₁ to open the valve, so L ₁ increases the force for opening the valve. Acts as a shock interval for. The plunger 30 moves beyond _L1 , and the valve body 32 moves to the valve port 2.
9, the cushion material 33 moves to the sixth position.
It collides with the suction element 24 as shown in Figure b. From this point on, during the protrusion length L ₂ of the cushion material 33, the spring 34 acts as a force that resists the suction force of the suction element 24, so that the impact on the plunger 30 against the suction element 24 is weakened, as shown in FIG. 6c. It is attracted to the suction element 24 as shown in FIG. At this time, the valve is fully opened and the valve body 32 is connected to the valve port 2.
9 to L ₃ lengths apart.

As can be seen from the above, the plunger 30
Assuming that the stroke is L ₄ , the impact interval of L ₁ of this stroke is effective in opening the valve with a small pulse width, and L ₂ is the impact interval of the suction element 24.
It works effectively to soften the impact of the plunger 30 on.

When the coil is then de-energized, the spring 34 overcomes the residual magnetism of the attractor 24 and pulls the plunger 30 away from the attractor 24 by L ₂ length, as shown in FIG. 6b. Therefore, the plunger 30 moves to the position shown in FIG. 6a by the force of its own weight, and the valve closes.

Generally, in a solenoid valve, the maximum force is generated when the plunger 30 is in close contact with the attractor 24 and L ₄ =0, as shown in FIG. 6c, but the solenoid valve requires the maximum force because When the valve opens slightly by overcoming the pressure difference in the fluid, that is, when it transitions from the state shown in Figure 6 a to the state shown in b, from then on, it does not require that much force, but rather, if the force is large, This may appear as impact noise or cause undesirable effects such as abrasion of the adsorption image.

As explained above, in the flow rate control device according to the present invention, by changing the width of the pulse that turns the solenoid valve on and off, it is possible to flow a flow rate depending on the situation. Therefore, when applied to devices such as car coolers that require quick response and precision, the pulse repetition period T may be set to, for example, 0.1 seconds; otherwise, a longer repetition period may be used. It is sufficient to use periodic pulses.

Furthermore, since the valve only needs to be fully opened and fully closed repeatedly, the designed flow rate can be obtained by accurately determining only the valve ports and accurately setting the pulse width.

Furthermore, in the case of small capacity control, the conventional problems can be solved by making the valve port less susceptible to the influence of fluid viscosity and by reducing the pulse width. Further, the repeated opening and closing operations of the valve serve to remove sludge and the like that tend to accumulate on the edges of the valve orifice, so fluctuations in the flow rate can also be prevented from this point of view.

Furthermore, in the electromagnetic valve used in the device according to the present invention, the valve element, which is biased by a spring on the surface facing the valve opening of the plunger that reciprocates between the suction element and the valve opening, faces the suction element. Since the spring-biased cushion members protrude from the respective surfaces, when the valve body is in the closed state, the spring biasing force against the valve body closes the valve with a small force due to the effect of the impact gap created between the valve body and the plunger. opens, and the spring biasing force against the cushion material absorbs the impact energy of the plunger against the suction element. and,
When in the open state, the biasing force against the cushion material acts as a force against the attractor, and when the current is turned off, it acts to overcome the residual magnetism of the attractor and pull the plunger away from the attractor. Therefore, the effect of the residual magnetism on the plunger becomes minute, and the plunger moves under its own weight to close the valve.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is a block diagram of a refrigerator to which the device of the present invention is applied, and FIG.
to c are graphs for explaining the principle of the present invention,
FIG. 3 is a circuit diagram showing a more detailed example of a part of FIG. 1, FIGS. 4a to 4c are graphs for explaining the operation of the apparatus shown in FIGS. 1, and FIGS. 6a to 6c are sectional views for explaining the operation of the solenoid valve shown in FIG. 5. 4... Solenoid valve, 24... Attractor, 29... Valve port, 30... Plunger, 32... Valve body, 33...
...Cushion material, 34...Spring.

Claims (1)

[Claims] 1. Applying a pulse with a constant repetition period to a solenoid valve that operates on and off by pulses, and controlling the flow rate of fluid passing through the solenoid valve by changing the width of the pulse and changing the ON time of the solenoid valve. In the liquid control device, the electromagnetic valve includes a plunger that reciprocates between a suction element and a valve port, a valve body protruding from a surface of the plunger facing the valve port, and the suction element of the plunger. a cushion member protruding from opposing surfaces; and a cushion member housed within the plunger;
A flow rate control device comprising: a spring that is commonly used to bias the valve body and the cushion material in a direction in which the valve body and the cushion material protrude.