Flow-rate control device

Abstract

To provide a flow-rate control device capable of suppressing a variation in supply pressure caused by a change in a setting flow-rate and suppressing an effect of pressure loss on a secondary side and cavitation.SOLUTION: A flow-rate control device 18 according to the present invention comprises: a flow-rate control valve 19 for controlling a flow-rate of a fluid flowing through a flow path; a flow-rate meter 20 that measures the flow-rate of the fluid through the flow path; and a control unit 21 that controls an opening degree of the flow-rate control valve 19 based on a measurement result of the flow-rate meter 20. The flow-rate control valve 19 is a three-way valve that divides and adjusts the flow of the fluid which flows from an inflow port 24 to a first outflow port 25 and a second outflow port 26. The flow-rate meter 20 is connected to the side of the second outflow port 26 and a multi-stage orifice 22 that reduces the pressure of the fluid in a step wise is provided on the side of the first outflow port 25.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a flow rate control device that can suppress fluctuations in supply pressure caused by changes in a set flow rate, and can suppress the effects of pressure loss on the secondary side and cavitation. [Background technology]

[0002] For example, Patent Document 1 discloses a system that uses a flow control device to control the instantaneous flow rate of cooling water when controlling the mold temperature. This flow control device includes a flow control valve, a flow meter, and a controller, and is configured to use a two-way valve for the flow control valve, measure the instantaneous flow rate of cooling water flowing in one direction with the flow meter, and have the controller feedback-control the opening of the flow control valve based on the measurement result.

[0003] Incidentally, in applications with many piping systems, such as die-casting dies, as in the mold temperature control system of Patent Document 1, installing a pump for each piping system has many disadvantages, such as problems with cost and installation space, so a single pump is often used with multiple piping systems branched off. In this case, there is a problem that when the set flow rate is changed, the supply pressure changes along the pump's QH curve. In addition, when the set flow rate is changed for each piping system, the source pressure changes according to the set flow rate, resulting in problems such as mutual interference between the piping systems and inability to control the instantaneous flow rate with the expected response speed.

[0004] As a method for solving this problem, a method is generally known in which an inverter and a pressure sensor are installed in the pump and the rotation speed of the pump is controlled so that the pressure is constant (for example, see Patent Document 2). However, since the frequency range in which the pump can be adjusted is somewhat limited, there is a problem that the pressure adjustment cannot be fully implemented when the set flow rate of the flow control device is completely closed (set flow rate 0 L) or when the set flow rate is extremely small. For example, when starting temperature control of a mold or heating from a standby state, the flow rate of cooling water is often set as low as possible during heating in order to improve the heating speed and achieve energy saving effects, and the above method has difficulty in dealing with such applications.

[0005] In terms of response, too, a sudden change in the pump's rotation speed can cause breakdowns, so the rotation speed must be changed gradually, and there is also the problem that it cannot respond to sudden changes in flow rate. This is because when the set flow rate is in a wide range, the pump's rotation frequency also becomes wide, resulting in delayed response. In addition, mutual interference occurs between the pump's pressure control and the flow control device, so in order to prevent this, it is necessary to make the response speed of the flow control device slower than the response speed of the pump, which creates the problem that the original response performance cannot be demonstrated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6844938 [Patent Document 2] JP 2005-194970 A Summary of the Invention [Problem to be solved by the invention]

[0007] As a method for preventing the above-mentioned interference of pressure fluctuation, for example, in the mold temperature control system of Patent Document 1, a method of controlling the flow rate using a three-way valve instead of a two-way valve as a flow control valve is considered. The general flow rate characteristics of a two-way valve are such that the flow rate changes according to the opening degree, as shown in FIG. 7, and the supply pressure of the pump changes along the QH curve accordingly. In contrast, the general flow rate characteristics of a three-way valve are such that the flow rates flowing into ports A and B change according to the opening degree, but the total flow rate flowing into port C is approximately constant, so that the supply pressure of the pump remains approximately constant even if the opening degree is changed. By utilizing this characteristic and making a flow control device using a three-way valve, it is possible to suppress the occurrence of source pressure fluctuations and mutual interference between each piping system even if the set flow rate is changed. However, even with this structure, the following problems remain.

[0008] The first issue is the effect of pressure loss. For example, if the cooling flow path of the target mold is narrow and the pressure loss is high, the flow characteristics will change significantly and the flow characteristics will become unbalanced. In this case, as shown in Figure 9, the flow characteristics will no longer be symmetrical between the A port side and the B port side, and not only will the expected flow control not be possible, but the total flow rate flowing into the C port will tend to change significantly depending on the opening due to the asymmetry. To solve this, as shown in Figure 10, an orifice (restriction) is provided on the A port side so that the loss is the same as that on the B port side. This makes the flow characteristics symmetrical, and even if the opening is changed, the total flow rate flowing into the C port will be roughly constant, and the occurrence of pressure fluctuations can be suppressed. However, since the total flow rate of the C port will decrease, if the flow rate is insufficient, it is necessary to increase the pump pressure to increase the supply amount.

[0009] The second problem is the occurrence of cavitation. As mentioned above, when the opening of the valve on the A port side is increased while the supply pressure of the pump is high, the differential pressure before and after the orifice provided on the secondary side of the A port becomes high. In addition, the flow rate of the fluid that is suddenly throttled by the orifice becomes extremely fast, and since there is almost no back pressure on the secondary side, cavitation is likely to occur due to a sudden drop in pressure. Cavitation not only generates vibrations, but also has adverse effects such as fluctuations in back pressure and accompanying fluctuations in differential pressure due to the local generation of bubbles, which causes gas-liquid mixing, resulting in unstable flow control and damage to the inside of the piping. In order to suppress this cavitation, it is necessary to suppress the flow rate and prevent the pressure from falling below the saturated water vapor pressure. However, the secondary side of the orifice is the return piping to the tank, which has almost no back pressure and is likely to fall below the saturated water vapor pressure, making it an environment in which cavitation is extremely likely to occur.

[0010] The present invention has been made to solve the above problems, and its object is to provide a flow control device that can suppress fluctuations in supply pressure caused by changes in the set flow rate, and can suppress the effects of secondary pressure loss and cavitation. [Means for solving the problem]

[0011] In order to suppress the fluctuation of the supply pressure due to the change of the set flow rate, the present invention adopts a structure in which the flow rate is controlled by using a three-way valve instead of a two-way valve as the flow control valve. Also, in order to suppress the influence of the pressure loss on the secondary side, the present invention adopts a structure in which an orifice is provided on the A port (first outlet port) side of the three-way valve so that the flow characteristics on the A port (first outlet port) side have the same pressure loss as the B port (second outlet port) side. Furthermore, in order to suppress the cavitation that occurs on the secondary side of the orifice, the present invention adopts a structure in which the orifice is not a single stage but a multi-stage structure that reduces the pressure in stages.

[0012] As shown in Figure 11, by providing a multi-stage orifice on the A port (first outlet port) side, the fluid pressure is reduced in stages, allowing the orifice diameter to be made larger, and as a result, the flow rate to be reduced. In addition, back pressure is applied to the secondary side of each stage, making it difficult for the pressure to fall below the saturated water vapor pressure, and the occurrence of cavitation can be suppressed. If you want to reduce the number of multi-stage orifices, you can consider making the upstream orifices smaller, which are less likely to fall below the saturated water vapor pressure.

[0013] Here, if the multi-stage orifice also functions as an orifice that adjusts pressure balance, it can be manufactured at low cost. However, if the orifices are connected in multiple stages by piping one by one, the number of sealing parts increases and a lot of space is required. Therefore, in the present invention, as shown in FIG. 12, ring plates having orifices are arranged in multiple stages, making it possible to make the device compact and significantly reduce the number of sealing parts. Also, as shown in FIG. 13, by incorporating this multi-stage orifice in the valve adapter of the three-way valve, it is possible to further compactify the device and reduce the number of sealing parts and manufacturing costs. In fact, as shown in FIG. 14, the present invention is a flow control device equipped with a flow control valve consisting of a three-way valve including a multi-stage orifice, a flow meter, and a controller (control unit).

[0014] That is, the flow control device of the present invention comprises a flow control valve that adjusts the flow rate of a fluid flowing through a flow path, a flow meter that measures the flow rate of the fluid flowing through the flow path, and a control unit that controls the opening degree of the flow control valve based on the measurement result of the flow meter, and is characterized in that the flow control valve is a three-way valve that divides and adjusts the fluid flowing in from an inlet port to a first outlet port and a second outlet port, the flow meter is connected to the second outlet port side, and a multi-stage orifice that gradually reduces the pressure of the fluid is provided on the first outlet port side.

[0015] In the flow control device according to the present invention, the multi-stage orifice may be configured to be built in a valve adapter of the three-way valve.

[0016] Furthermore, in the flow control device according to the present invention, the multi-stage orifice may have a structure in which multiple ring plates, each having a tapered orifice whose diameter narrows from the inlet to the outlet, are arranged side by side. Effect of the Invention

[0017] According to the flow control device of the present invention, the flow control valve is structured as a three-way valve that divides and adjusts the flow of the fluid flowing in from the inlet port to the first outlet port and the second outlet port, thereby suppressing fluctuations in the pump supply pressure caused by changes in the set flow rate. Also, by adopting a structure in which an orifice is provided on the first outlet port side so that the flow characteristics on the first outlet port side of the three-way valve have the same pressure loss as the second outlet port side that is the subject of flow control, the influence of pressure loss on the secondary side can be suppressed. Furthermore, by adopting a structure in which a multi-stage orifice is provided on the first outlet port side that reduces the pressure of the fluid in stages, cavitation caused by a decrease in the back pressure on the secondary side can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] Overall view showing an example in which the flow rate control device according to the present invention is applied to a mold temperature control system. [Diagram 2] FIG. 1 is a partial cross-sectional view showing the structure of a flow control device according to the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a switching form of a flow rate control valve in the flow rate control device according to the present invention; [Figure 4] FIG. 2 is an enlarged exploded view showing the structure of a multi-stage orifice in the flow control device according to the present invention. [Diagram 5] FIG. 11 is a partial cross-sectional view showing a modified example of the flow control device according to the present invention. [Figure 6] FIG. 11 is a partial cross-sectional view showing a modified example of the flow control device according to the present invention. [Figure 7] An explanatory diagram showing typical flow characteristics of a two-way valve [Figure 8] An explanatory diagram showing typical flow characteristics of a three-way valve [Figure 9]An explanatory diagram showing the flow characteristics when there is pressure loss on the B port side of a three-way valve [Figure 10] An explanatory diagram showing the flow characteristics when an orifice is installed on the A port side of a three-way valve. [Figure 11] An explanatory diagram showing the structure of a three-way valve with a multi-stage orifice on the A port side [Figure 12] An explanatory diagram showing the structure of a multi-stage orifice provided by arranging ring plates on the A port side of a three-way valve. [Figure 13] An explanatory diagram showing the structure of a multi-stage orifice built into the valve adapter on the A port side of a three-way valve [Figure 14] An explanatory diagram showing a flow control device including a flow control valve consisting of a three-way valve including a multi-stage orifice, a flow meter, and a controller (control unit). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] Fig. 1 shows an embodiment in which a mold temperature control system is constructed using a flow control device according to the present invention. The mold temperature control system 1 of this embodiment is a system that controls the temperature of a mold 3 in a die casting machine 2 that produces (casts) aluminum die-cast products by changing the flow rate of cooling water that is controlled at a constant flow rate during production. The mold 3 constitutes a part of the die casting machine 2, and is composed of a fixed mold 4 provided in the injection unit and a movable mold 5 provided in the mold clamping unit.

[0021] Temperature sensors 6 (...6n) consisting of thermocouples or resistance temperature detectors are attached to each part of the mold 3 (fixed mold 4 and movable mold 5). The temperature sensors 6 detect the maximum temperature, minimum temperature, average temperature, and current temperature of the mold 3 in the production cycle in real time. The detected temperature information of the mold 3 is converted into an electric signal and output to a control device 7 which performs the calculation process described later.

[0022] A cooling water circulator 8 for circulating cooling water is provided outside the die casting machine 2 as a means for adjusting the temperature of the die 3. The cooling water circulator 8 is configured to include a cooling tower 9, a heat exchanger 10, a tank 11, and a pump 12. The water in the tank 11 is cooled by the cooling tower 9 via the heat exchanger 10. The cooling water is supplied by the pump 12 through a water supply pipe 13 and a die pipe 14 to cooling water holes provided in each part of the die 3, and circulates to the tank 11 through a return pipe 15.

[0023] A flow control unit 16 is attached to each of the molds 3 (the fixed mold 4 and the movable mold 5). The flow control unit 16 is composed of a manifold 17 connected to the water supply pipe 13, and an assembly of multiple flow controllers 18 (...18n) connected to the manifold 17. Cooling water from the water supply pipe 13 is introduced into the cavity of the manifold 17 via a strainer (not shown), and is branched at multiple ports to be supplied to each of the flow controllers 18 (...18n).

[0024] The flow controller 18 is a flow control device that controls the instantaneous flow rate of cooling water that cools each part of the mold 3 (the fixed mold 4 and the movable mold 5). As shown in Fig. 2, the flow controller 18 is configured with a flow control valve 19, a flow meter 20, a controller (control part) 21, and a multi-stage orifice 22, and is connected to a port of the manifold 17 via an adapter 23.

[0025] The flow rate control valve 19 is a three-way valve of a dividing type that divides the fluid flowing in from an inlet port 24 into a first outlet port 25 and a second outlet port 26, and adjusts the flow rate ratio flowing out from both outlet ports. The inlet port 24 is connected to a water supply pipe 13 that supplies cooling water from the pump 12, and the first outlet port 25 is connected to a return pipe 15 that returns the cooling water to the tank 11. The second outlet port 26 is connected to a mold pipe 14 that supplies cooling water to a cooling water hole in the mold 3, and the piping system on the second outlet port 26 side (one side) is the target of flow rate control.

[0026] The flow rate control valve 19 of this embodiment employs an electrically operated rotary valve mechanism, in which a valve element 28 built into a valve body 27 is driven by the electric force of an actuator 29, and the valve opening is adjusted by the electric force. The actuator 29 has a built-in stepping motor 30, and is attached to the valve body 27 via a motor bracket 31. The valve element 28 comprises a valve shaft 32 and a valve 33 provided at its tip, and is connected to the rotating shaft of the stepping motor 30. Reference numeral 34 denotes a sliding O-ring, 35 denotes a shaft packing that presses the valve shaft 32 and acts as an orifice, and 36 denotes a retainer lock that presses and fixes the shaft packing 35.

[0027] 3, when the opening of the second outflow port (port B) 26 is switched from a fully closed state (opening degree 0%) to a fully open state (opening degree 100%), the opening of the first outflow port (port A) 25 is switched from a fully open state to a fully closed state accordingly, so that the flow rate ratio of the cooling water flowing out from both outflow ports (ports A and B) can be adjusted. Note that even if the valve 33 of the valve body 28 rotates and the flow rate ratio of the cooling water flowing out from the first outflow port (port A) 25 and the second outflow port (port B) 26 changes, the flow rate (total flow rate) of the cooling water flowing in from the inflow port (port C) 24 remains approximately constant.

[0028] The flowmeter 20 measures the flow rate of the fluid flowing out from the second outlet port 26, and in this embodiment, an impeller type flowmeter is used. This impeller type flowmeter is configured with a screw 37 rotatably supported in the flow path, and a magnetic sensor 39 that detects a magnet 38 sealed in the blade of the screw 37. The magnetic sensor 39 is a non-contact sensor with a built-in Hall IC 40 consisting of a Hall element, a power circuit, an amplifier, etc., and the Hall IC 40 detects the magnetic field of the magnet 38 and outputs an electric signal to the controller 21. In addition, 41 is a straightening plate that prevents turbulence of the fluid that has flowed into the flow path after being diverted and straightens the flow, and this straightening plate 41 also serves as a bearing for the screw 37. In addition, 42 is a wave washer that presses the straightening plate 41 to prevent rattling.

[0029] The controller (controller) 21 is a microcomputer equipped with functions such as flow rate measurement, motor control, and PID flow rate control. The controller 21 measures a flow rate value calculated based on the number of rotations of the screw 37 using an electric signal output from the magnetic sensor 39. The controller 21 also controls the stepping motor 30 of the actuator 29 based on the measured flow rate value and a set flow rate value input from the control device 7, and performs feedback control (PID control) of the opening of the flow rate adjustment valve 19.

[0030] The multi-stage orifice 22 reduces the pressure of the fluid flowing out of the first outlet port 25 in stages, and has the functions of adjusting the pressure balance and suppressing cavitation. The multi-stage orifice 22 of this embodiment is built into a valve adapter 43 connected to the valve body 27, and is designed to be compact and reduce the number of sealing parts. As shown in an enlarged view in FIG. 4, the multi-stage orifice 22 has multiple ring plates 44 (five in this embodiment) arranged in the thickness direction, resulting in a compact structure that is less likely to be clogged with dust. Each ring plate 44 has a tapered orifice 45 on one side (the inlet side) whose diameter gradually narrows from the inlet to the outlet.

[0031] As described above, according to the flow controller 18 of the present embodiment, the flow rate control valve 19 is a three-way valve to control the distribution amount between the first outlet port 25 and the second outlet port 26, thereby suppressing fluctuations in the supply pressure of the pump 12 according to the flow rate of the flowing cooling water, and suppressing mutual interference between the piping systems. In addition, the tapered orifice 45 is provided in the valve adapter 43, and precise flow rate control is possible by preventing deterioration of the balance of flow characteristics caused by the difference in back pressure between the first outlet port 25 side and the second outlet port 26 side. Furthermore, by adopting the multi-stage orifice 22 in which a plurality of ring plates 44 having tapered orifices 45 are arranged side by side, the pressure of the fluid flowing out of the first outlet port 25 can be reduced in stages, and cavitation caused by low back pressure can be suppressed.

[0032] In the above-mentioned embodiment, a T-shaped three-way valve is used as the flow rate control valve 19 constituting the flow controller 18, but modified examples such as those shown in Figs. 5 and 6 may be used. Since the flow rate control valve 19 has a valve throttle at the inlet of the flow meter 20, it is possible that turbulent flow from the valve may adversely affect the flow rate characteristics. In order to prevent such adverse effects, the flow controller 18A shown in Fig. 5 is connected to the flow meter 20 via an L-shaped elbow 46 interposed between the valve body 27, and the flow controller 18B shown in Fig. 6 is connected to the multi-stage orifice 22 via an L-shaped elbow 46 interposed between the valve body 27. By bending the piping with the L-shaped elbow 46 in this way, the fluid flowing through the flow path collides with the inner wall, so that extreme turbulence can be suppressed over a short distance. In addition, since the mounting position of the flow meter 20 is vertical, in the case of an impeller-type flow meter such as that of this embodiment, the sliding resistance of the shaft of the screw 37 is reduced, which has the effect of improving the low flow rate characteristics and enabling flow rate measurement over a wide range.

[0033] In the above-described embodiment, the flow control device according to the present invention is used to construct a die-casting machine mold temperature control system, but the application of the present invention is not limited to this. For example, the present invention can be applied to a piping system in which a plurality of injection molding machines using cooling water and machine tools using cutting oil are installed, in which the supply amount of fluids such as cooling water, refrigerant liquid, cutting oil, etc. is changed according to the change in the number of machines in operation. In the above-described mold temperature control system, the instantaneous flow rate of the cooling water is controlled by a flow controller, but it is also possible to control the instantaneous flow rate, count the integrated value, and control the integrated flow rate. [Explanation of symbols]

[0034] 1: Mold temperature control system 2: Die casting machine 3:Mold 4: Fixed type 5: Movable type 6: Temperature sensor 7: Control device 8: Cooling water circulation system 9: Cooling tower 10: Heat exchanger 11: Tank 12: Pump 13: Water supply piping 14: Mold piping 15: Return pipe 16: Flow control unit 17: Manifold 18: Flow controller 19: Flow control valve 20:Flowmeter 21: Controller 22: Multi-stage orifice 23: Adapter 24: Inlet port 25: First outflow port 26: Second outflow port 27: Valve body 28: Valve body 29: Actuator 30: Stepping motor 31: Motor bracket 32: Valve shaft 33: Valve 34: Sliding O-ring 35: Shaft packing 36: Retainer lock 37: Screw 38: Magnet 39: Magnetic sensor 40: Hall IC 41: Rectifier plate 42: Wave washer 43: Valve adapter 44: Ring plate 45: Tapered orifice 46: L-shaped elbow

Claims

1. a flow rate control valve that controls the flow rate of the fluid flowing through the flow path; a flow meter for measuring a flow rate of a fluid flowing through the flow path; a control unit that controls the opening degree of the flow rate adjustment valve based on the measurement result of the flow meter, The flow rate control valve is a three-way valve that divides and adjusts the flow of a fluid that has flowed in from an inlet port to a first outlet port and a second outlet port, and the flow meter is connected to the second outlet port side, and a multi-stage orifice that reduces the pressure of the fluid in stages is provided on the first outlet port side. A flow rate control device.

2. The multi-stage orifice is built into a valve adapter of the three-way valve. The flow control device according to claim 1 .

3. The multi-stage orifice is configured by arranging a plurality of ring plates each having a tapered orifice whose diameter narrows from the inlet to the outlet.

3. The flow rate control device according to claim 1 or 2.

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