CN108454049B

CN108454049B - Pressure control device

Info

Publication number: CN108454049B
Application number: CN201710085962.5A
Authority: CN
Inventors: 久田松润; 荒木康也
Original assignee: Matsui Universal Joint Manufacturing Co
Current assignee: Matsui Universal Joint Manufacturing Co
Priority date: 2017-02-17
Filing date: 2017-02-17
Publication date: 2022-03-29
Anticipated expiration: 2037-02-17
Also published as: CN108454049A

Abstract

The invention provides a pressure control device. The pressure control device (100) controls the pressure of the medium circulating in the circulation paths (11, 12, 16), and the circulation paths (11, 12, 16) are provided between the suction side and the discharge side of the pump (31) and the respective predetermined objects. A pressure control device (100) is provided with: a temperature detection unit (71) that detects the temperature of the medium in the circulation path (11); a pressure calculation unit (52) that calculates the saturated vapor pressure of the medium in the circulation path (11) based on the temperature detected by the temperature detection unit (71); and a pressure control unit (50) for controlling the pressure of the medium on the suction side of the pump so as to be equal to or higher than the saturated steam pressure calculated by the pressure calculation unit (52). With this pressure control device, the pressure of the medium circulating in the circulation path can be controlled to an optimum pressure.

Description

Pressure control device

Technical Field

The present invention relates to a pressure control device that controls the pressure of a medium circulating through a circulation path provided between a suction side and a discharge side of a pump and a predetermined object thereof.

Background

A mold is used in an injection molding machine for injection molding a synthetic resin such as plastic. The injection molding mold comprises: a mold cavity which is a space portion filled with molten plastic; a flow path through which flows a medium for cooling and solidifying the molten plastic. It is very important to maintain the temperature of the mold at a predetermined temperature accurately to improve the accuracy of the molded product.

The mold temperature adjusting machine for adjusting the mold temperature generally uses water as a medium, and is roughly classified into two types, i.e., a type for controlling the mold temperature to 100 ℃ or lower and a type for controlling the mold temperature to 100 ℃ or higher. In the high-temperature type mold temperature control machine, the pressure of the medium in the circulation path needs to be maintained at a state equal to or higher than the saturated vapor pressure in the medium temperature. If the pressure is lower than the saturated vapor pressure, the medium may boil in the circulation passage, the vapor region may be generated in the circulation passage, and the medium pump may be damaged due to the empty operation of the medium pump.

Therefore, a temperature control device has been disclosed in the related art (japanese patent application laid-open No. 2010-94855) which includes an auxiliary pump (pressure pump) in addition to a medium pump, and which is activated when the pressure of a medium in a circulation passage is lower than a set pressure.

However, in the temperature control machine described in japanese patent application laid-open No. 2010-94855, since the pressure pump (auxiliary pump) is operated when the pressure of the medium in the circulation passage is lower than the set pressure, the pressure pump needs to be operated sufficiently or excessively in order to make the pressure of the medium in the circulation passage equal to or higher than the saturated vapor pressure.

In addition, an excessive pressure is applied to the circulation path, the mold, and the like by the operation of the pressurizing pump. Therefore, problems occur such as excessive power consumption, shortened life of the pressure pump, and necessity of increasing the pressure resistance of the circulation path, the die, and the like.

Disclosure of Invention

In view of the above circumstances, an object of the present invention is to provide a pressure control device capable of controlling the pressure of a medium circulating in a circulation path to an optimum pressure.

The present invention provides a pressure control device for controlling a pressure of a medium circulating in a circulation path provided between a suction side and a discharge side of a pump and respective predetermined objects, the pressure control device comprising: a temperature detection unit that detects a temperature of the medium in the circulation path; and a pressure calculation unit that calculates a saturated vapor pressure of the medium in the circulation path based on the temperature detected by the temperature detection unit; and a pressure control unit for controlling the pressure of the medium on the suction side of the pump to be equal to or higher than the saturated steam pressure calculated by the pressure calculation unit.

In the present invention, the pressure control device includes: a temperature detection unit for detecting the temperature of the medium in the circulation path; and a pressure calculation unit that calculates a saturated vapor pressure of the medium in the circulation path based on the temperature detected by the temperature detection unit; and a pressure control unit for controlling the pressure of the medium on the suction side of the pump to be equal to or higher than the saturated steam pressure calculated by the pressure calculation unit.

Therefore, in the case where the medium is water, the relationship between the saturated water vapor pressure (absolute pressure) and the temperature (absolute temperature) is disclosed in various formulas, and as an example, the operation can be performed by using the Hailan-Wickers formula. Since the relationship between the temperature (c) of the medium and the pressure (gauge pressure is absolute pressure — atmospheric pressure) can be known by this equation, the saturated vapor pressure of the medium in the circulation path can be calculated based on the temperature measured by the temperature detector.

The pressure control unit controls the pressure of the medium to be higher than the saturated steam pressure corresponding to the temperature of the medium, so that the pressure can be controlled to be proper no matter the temperature of the medium, and the pressure resistance degree of the circulating path, the die and the like does not need to be increased.

Another pressure control apparatus according to the present invention is characterized by further comprising: a water feed pipe connected to a water feed port and communicating with a circulation path on a suction side of the pump; and a pressure control unit that controls the pressure of the medium to be equal to or higher than a saturated vapor pressure by pressurization of the pressure pump.

In the invention, the pressure control device also comprises a water supply pipe which is connected with the water supply mouth and communicated with the circulation path at the suction side of the pump; and a pressure control unit for controlling the pressure of the medium to be equal to or higher than a saturated vapor pressure by pressurization of the pressure pump.

That is, the pressure control unit controls the pressure of the medium to be equal to or higher than the saturated vapor pressure corresponding to the temperature of the medium in accordance with the various temperatures of the medium by the pressurizing type of the pressurizing pump, and thus the pressure of the medium can be controlled to be an appropriate pressure regardless of the temperature of the medium. In addition, unnecessary operation of the booster pump is not required, and generation of excessive power consumption can be suppressed, thereby preventing a reduction in the life of the booster pump.

Another pressure control apparatus according to the present invention is characterized by further comprising: a pressure detection unit that detects a pressure of the medium on a suction side of the pump; and a driving unit that drives the pressure pump when the pressure detected by the pressure detecting unit is equal to or less than a predetermined lower limit value.

In the present invention, the pressure control device further includes: a pressure detection unit that detects a pressure of the medium on the suction side of the pump; and a driving unit that drives the pressurizing pump when the pressure detected by the pressure detecting unit is less than or equal to a predetermined lower limit value. The lower limit value may be, for example, a lower limit value corresponding to the saturated steam pressure calculated by the pressure calculation unit. Therefore, since the saturated vapor pressure can be obtained for each medium temperature, the lower limit value of each medium temperature can be set so that the pressure can be controlled to be appropriate regardless of the temperature of the medium.

Another pressure control apparatus according to the present invention is characterized by further comprising: a drain pipe connected to the drain port and communicating with the circulation path on the suction side of the pump; and a drain valve installed midway in the drain pipe; and a drain valve control unit that controls the drain valve to open when the pressure detected by the pressure detection unit is equal to or higher than a predetermined upper limit value.

In the present invention, the pressure control device further includes: a drain pipe connected to the drain port and communicating with the circulation path on the suction side of the pump; and a drain valve installed midway in the drain pipe; and a drain valve control unit that controls the drain valve to open when the pressure detected by the pressure detection unit is equal to or higher than a predetermined upper limit value. The upper limit value may be, for example, an upper limit value corresponding to the saturated steam pressure calculated by the pressure calculation unit.

That is, when the pressure of the medium in the circulation path is equal to or higher than a predetermined upper limit value, the discharge valve control unit opens the discharge valve to reduce the pressure in the circulation path. Since the saturated vapor pressure of each medium temperature can be obtained, the lower limit value of each medium temperature can be set so as to be controlled to an appropriate pressure, that is, within a certain range, regardless of the temperature of the medium.

In another pressure control apparatus according to the present invention, the driving unit drives the pressure pump before a node at which the discharge valve is opened when the discharge valve control unit controls the discharge valve to be opened.

In the present invention, when the drain valve control section controls the drain valve to open, the driving section drives the pressurizing pump before a node at which the drain valve is in an open state. After the drain valve is opened, the closed circulation path is depressurized through the drain valve, which may cause the pressure of the medium in the circulation path to be lower than the saturated vapor pressure. In this case, the pressure in the circulation path is increased before the node at which the discharge valve is opened or before the node at which the discharge valve is opened and the pressure in the circulation path is decreased, by driving the pressure pump, and thereby the pressure in the circulation path is prevented from being decreased to be lower than the saturated vapor pressure calculated by the pressure calculation unit.

In another pressure control device according to the present invention, the pressure pump is an electromagnetic pump, and the driving unit drives the pressure pump by using a dc pulse having a desired cycle and duty ratio.

In the present invention, the pressure pump is an electromagnetic pump. That is, the medium is pressurized by the stroke of the plunger of the pressurizing pump. And a driving unit for driving the pressure pump by using the DC pulse with a required period and duty ratio. The number of strokes of the plunger can be changed by changing the cycle of the dc pulse, and the torque (thrust) of the plunger can be changed by changing the duty ratio of the dc pulse, so that the required pressure can be finely controlled.

With the pressure control device of the present invention, the pressure of the medium circulating in the circulation path can be controlled to an optimum pressure.

Drawings

Fig. 1 is an explanatory view showing a structure of a mold temperature controller as a pressure control device according to the present embodiment.

Fig. 2 is an explanatory diagram showing a relationship between the temperature of the medium, the absolute pressure, and the gauge pressure.

Fig. 3 is a timing chart showing a basic operation of the mold temperature controller according to the present embodiment.

Fig. 4 is a timing chart showing an operation when the pressure of the mold temperature adjusting machine according to the present embodiment rises.

Fig. 5 is a flowchart showing a processing procedure of the mold temperature adjusting machine according to the present embodiment.

Detailed Description

The present invention will be described below with reference to drawings showing the present embodiment. Fig. 1 is an explanatory diagram showing a configuration of a mold temperature controller 100 as a pressure control device according to the present embodiment. In the present embodiment, the die temperature controller 100 is exemplified as the pressure control device, but the pressure control device is not limited to the die temperature controller. The mold temperature controller 100 controls the temperature and pressure of a medium for cooling supplied to the mold 200 as an object.

As shown in fig. 1, the mold temperature adjusting machine 100 is formed in the following structure: a pipe line 11 (a medium supply pipe) is connected between the discharge side (OUT) of the pump 31 and the inlet side of the die 200, a pipe line 12 (a medium return pipe) is connected between the outlet side of the die 200 and the suction side (IN) of the pump 31, and a medium (for example, water) is circulated through the pipes 11 and 12 and the branch pipe 16 by the pump 31. That is, the pump 31 rotates the impeller at a high speed by the rotation of the motor in the casing, for example, and circulates the medium through the pipes 11 and 12 and the branch pipe 16 by the centrifugal force acting on the medium. The pipelines 11 and 12 and the branch pipeline 16 may be collectively referred to as a circulation pipeline.

A pressure sensor 62 is provided in the pipe line 11 near the discharge side of the pump 31, and can detect the pressure of the medium near the discharge side of the pump 31. A heating unit 80 is installed in the middle of the pipe 11 to heat the medium and raise the temperature of the medium. The thermostat 81 stops heating of the heating unit 80 when the heating unit 80 exceeds a predetermined temperature. The pipeline 11 is provided with a temperature sensor 71 as a temperature detecting unit capable of detecting the temperature of the medium in the pipeline 11.

The pipeline 11 is branched into 2 systems in the middle, and the branched pipelines 11 are connected to the inlet sides of the molds 200, respectively. The branched pipes 11 are respectively provided with a medium feeding valve 21, and the flow rate of the medium in each branched pipe 11 can be adjusted. Similarly, the line 12 is branched into 2 lines at the outlet side of the mold 200, and the branched lines 12 are integrated into one line 12. The branched pipes 12 are respectively provided with a return valve 22 for adjusting the flow rate of the medium in each branched pipe 12.

A heat exchanger 40 is attached to a middle portion of the pipe 12, and a cooling electromagnetic pump 23 is attached to the pipe 12 on the outlet side of the heat exchanger 40. A branch line 16 is provided between a necessary position of the line 12 on the inlet side of the heat exchanger 40 (a position indicated by a reference symbol a in fig. 1, which may also be referred to as a branch point a) and a necessary position of the line 12 on the outlet side of the cooling electromagnetic pump 23 (a position indicated by a reference symbol B in fig. 1, which may also be referred to as a branch point B). However, the branch line 16 may not be provided.

The heat exchanger 40 has a cooling passage through which cooling water flows, one side of which communicates with the cooling line 13, and a medium passage through which a medium flows, the other side of which communicates with the line 12. The heat exchanger 40 performs heat exchange between the cooling water flowing through the cooling flow passage and the medium flowing through the medium flow passage, thereby adjusting the temperature of the cooling medium.

An open relief valve and a pressure sensor 63 as a pressure detecting unit are provided in the vicinity of the suction side of the pump 31 in the pipe line 12. The pressure sensor 63 is used to detect the pressure of the medium near the suction side of the pump 31. Further, a strainer is provided in the pipe line 12 on the inlet side of the heat exchanger 40 (upstream of the branch point a). The filter screen can remove solid components contained in the medium.

A water supply pipe 14 is provided between the water supply port and a branch point B of the pipe 12. That is, the water feed pipe 14 communicates with the suction-side pipe line 12 of the pump 31. The water supply pipe 14 is provided with a strainer and a pressure sensor 61 on the water supply port side. The pressure sensor 61 is used to detect the feed water pressure. A check valve 26 is attached to a middle portion of the water supply pipe 14, both sides of the check valve 26 are connected to a branch line 14a, and a pressure pump 32 is attached to the branch line 14 a.

The pressurizing pump 32 may be, for example, an electromagnetic pump. That is, the medium is pressurized by the stroke of a plunger (not shown) of the pressurizing pump 32. The pressure pump 32 pressurizes the pressure of the medium (for example, water) in the pipelines 11 and 12 and the branch pipeline 16 to a pressure higher than the saturated vapor pressure under the control of the pressure control unit 50.

Further, a cooling line 13 is connected to an upstream side of a position connected to the branch pipe 14a of the line 14, and the cooling line 13 branches the cooling water and flows to the heat exchanger 40. The cooling line 13 is connected to one end of the cooling flow passage on the inlet side of the heat exchanger 40. The cooling line 13 connected to the other end of the cooling flow path on the outlet side of the heat exchanger 40 is connected to a drain port. A cooling water electromagnetic valve 25 is attached to a middle portion of the cooling line 13 connected to the drain port.

Further, a drain pipe 15 is connected to the pipe line 12b between the heat exchanger 40 and the cooling solenoid valve 23, and the drain pipe 15 is connected to a drain port. A drain solenoid valve 24 as a drain valve is installed in the middle of the drain pipe 15.

The mold temperature controller 100 includes a pressure control unit 50, and the pressure control unit 50 includes a valve opening/closing control unit 51, a pressure calculation unit 52, a drive unit 53, and the like. The pressure control section 50 can acquire the temperature measured by the temperature sensor 71. The pressure control unit 50 can acquire the pressures measured by the

pressure sensors

61, 62, and 63.

The valve opening/closing control unit 51 controls the opening/closing of the cooling solenoid valve 23, the drain solenoid valve 24, and the cooling water solenoid valve 25.

The pressure calculation unit 52 calculates the saturated vapor pressure of the medium in the pipe line 11 based on the temperature detected by the temperature sensor 71.

The driving unit 53 drives the pressurizing pump 32 when the pressure detected by the pressure sensor 63 is less than a predetermined lower limit value. In addition, the lower limit value is a pressure value higher than the saturated vapor pressure.

Next, an outline of the operation of the mold temperature controller 100 will be described. After the water discharge solenoid valve 24, the cooling solenoid valve 23, the medium feed pump 21, and the medium return valve 22 are opened, water as a medium is supplied from the water supply port to completely discharge the air in the circulation passages such as the pipelines 11 and 12 and the branch pipeline 16, and thereafter, the water discharge solenoid valve 24 is closed to fill the circulation passages such as the pipelines 11 and 12 and the branch pipeline 16 with the medium. The pressure of the medium in the circulation path such as the pipelines 11 and 12 and the branch pipeline 16 can be maintained at a saturated vapor pressure or higher corresponding to the temperature of the medium by the control operation of the pressure control unit 50. The temperature of the medium in the circulation path such as the pipelines 11 and 12 and the branch pipeline 16 can be raised to a temperature required for heating by the heating unit 80. The temperature of the medium in the circulation path such as the branch line 16 can be cooled to a desired temperature by the heat exchanger 40. The temperature of the medium in the circulation path such as the pipes 11 and 12 and the branch pipe 16 can be adjusted (controlled) by the heating unit 80 and the cooling operation by the heat exchanger 40, and the temperature of the medium, that is, the temperature of the medium in the mold 200 can be adjusted (controlled) to a desired temperature (for example, 180 ℃, but not limited thereto, and may be 150 ℃).

The mold temperature controller 100 will be described in detail below.

As described above, the mold temperature controller 100 according to the present embodiment includes: a temperature sensor 71 for detecting the temperature of the medium in the pipes 11 and 12 and the branch pipe 16 (circulation passage); a pressure calculation unit 52 that calculates the saturated vapor pressure of the medium in the circulation path based on the temperature detected by the temperature sensor 71; and a pressure control unit 50 for controlling the pressure of the medium on the suction side of the pump 31 to be equal to or higher than the saturated steam pressure calculated by the pressure calculation unit 52.

Various formulas are disclosed for the relationship between saturated vapor pressure (absolute pressure) and temperature (absolute temperature) when the medium is water, and the calculation can be performed by using the formula of helan-Wexler-Hyland as an example. Since the relationship between the temperature (c) of the medium and the pressure (gauge pressure is absolute pressure — atmospheric pressure) can be known by this equation, the saturated vapor pressure of the medium in the circulation path can be calculated based on the temperature measured by the temperature detector 71. In addition, the formula of the relationship between the saturated water vapor pressure (absolute pressure) and the temperature (absolute pressure) is not limited to the haian-weklers formula.

Fig. 2 is an explanatory diagram showing a relationship between the temperature of the medium, the absolute pressure, and the gauge pressure. The temperature of the medium (water) is given in degrees celsius. Gauge pressure is the absolute pressure minus atmospheric pressure. As shown in FIG. 2, when the temperature of the medium was 150 ℃, the gauge pressure was 0.3749MPa, the temperature of the medium was 180 ℃ and the gauge pressure was 0.9015 MPa.

When the pressure in the pipe line 12 on the suction side of the pump 31 is, for example, 0.9MPa, the pressure in the pipe line 11 on the discharge side of the pump 31 is about 1.3MPa because the pressure is raised by the pump 31 by about 0.4 MPa. In fig. 2, for the sake of simplicity, temperatures at 10 ℃ are illustrated, and in practice, the temperature intervals may be recorded in a memory (not shown) as gauge pressure at 0.1 ℃ and the pressure may be calculated by referring to the pressure (gauge pressure) corresponding to the measured temperature. Further, the pressure calculation unit 52 may be incorporated with the relationship shown in FIG. 2 as an arithmetic expression to calculate the pressure corresponding to the measured temperature.

The pressure calculation unit 52 can calculate the saturated steam pressure corresponding to the temperature of the medium even when the temperature of the medium in the pipelines 11 and 12 and the branch pipeline 16 changes. The pressure control unit 50 controls the pressure of the medium to be equal to or higher than the saturation vapor pressure corresponding to the temperature of the medium, regardless of the temperature of the medium. Therefore, it is possible to suppress the application of excessive pressure to the circulation path, the die, and the like, and it is not necessary to increase the degree of pressure resistance of the circulation path, the die, and the like.

Further, the mold temperature controller 100 of the present embodiment further includes: a water supply pipe connected to the water supply port and communicating with the suction-side pipe 12 of the pump 31; and a pressure pump 32 attached to a middle portion of the water supply pipe 14. And a pressure control unit 50 for controlling the pressure of the medium to be equal to or higher than the saturated vapor pressure by the pressurization of the pressurization pump 32.

That is, the pressure control unit 50 controls the pressure of the medium to be equal to or higher than the saturated vapor pressure corresponding to the temperature of the medium in accordance with the type of pressurization by the pressurization pump 32 for various temperatures of the medium, and thus can control the pressure of the medium to be an appropriate pressure regardless of the temperature of the medium. Further, the operation of the pressurizing pump is not required, and the generation of the excessive power consumption can be suppressed, and the shortening of the life of the pressurizing pump can be prevented.

Further, the mold temperature controller 100 of the present embodiment further includes: a pressure sensor 63 that detects the pressure of the medium on the suction side of the pump 31; the driving unit 53 drives the pressurizing pump 32 when the pressure detected by the pressure sensor 63 is equal to or lower than a predetermined lower limit value.

The lower limit value may be, for example, a lower limit value corresponding to the saturated steam pressure calculated by the pressure calculation unit 52. Therefore, since the saturated vapor pressure can be obtained for each medium temperature, the lower limit value of each medium temperature can be set so that the pressure can be controlled to be appropriate regardless of the temperature of the medium.

Further, the mold temperature controller 100 of the present embodiment further includes: a drain pipe 15 connected to the drain port and communicating with the pipe 12 on the suction side of the pump 31; a drain electromagnetic pump 24 attached to a middle portion of the drain pipe 15; the valve opening/closing control unit 51, which is a drain valve control unit, controls the drain solenoid valve 24 to open when the pressure calculated by the pressure calculation unit 52 is equal to or higher than a predetermined upper limit value. The upper limit value may be, for example, an upper limit value corresponding to the saturated steam pressure calculated by the pressure calculation unit.

That is, when the pressure of the medium in the pipe line 12 is equal to or higher than a predetermined upper limit value, the valve opening/closing control unit 51 opens the drain solenoid valve 24 for a certain period of time, and reduces the pressure in the pipe lines 11 and 12 and the branch pipe line 16. Since the saturation vapor pressure at each temperature of the medium can be obtained, the upper limit value of each temperature of the medium can be set so that the pressure can be controlled to be appropriate, that is, within a certain range, regardless of the temperature of the medium.

In the mold temperature controller 100 according to the present embodiment, the driving unit 53 drives the pressurizing pump 32 before the node at which the electromagnetic drain pump 24 is in the open state when the valve opening/closing control unit 51 controls the opening of the electromagnetic drain pump 24.

When the electromagnetic drain pump 24 is turned on, the pressure of the medium in the piping 11, 12 and the branch piping 16, which are originally closed, is reduced by the electromagnetic drain valve 24, and the pressure of the medium in the piping 11, 12 and the branch piping 16 may be lower than the saturated vapor pressure. At this time, by driving the pressurizing pump 32 at the node at which the drain solenoid valve 24 is opened or at a node before the node, when the drain solenoid valve 24 is opened, the pressure is increased before the node at which the pressure in the pipes 11 and 12 and the branch pipe 16 is reduced, and therefore, the pressure of the medium can be prevented from being reduced to be lower than the saturated vapor pressure calculated by the pressure calculating unit 52.

In the mold temperature controller 100 according to the present embodiment, the pressure pump 32 may be, for example, an electromagnetic pump. The driving unit 53 drives the pressure pump 32 with a dc pulse having a desired cycle and duty ratio. By changing the duty ratio of the direct current pulse, the torque (thrust) of the plunger can be changed, so that the required pressure can be finely controlled.

Fig. 3 is a timing chart showing a basic operation of the mold temperature controller 100 according to the present embodiment. Fig. 3 shows, from the upper stage to the lower stage, the pressure of the medium, the operating state of the pump 31, the operating state of the pressure pump 32, and the operating state of the drain solenoid valve 24 in this order. Fig. 3 shows operations when the pressure of the medium rises, when the pressure of the medium stabilizes, and when the pressure of the medium falls. In addition, the horizontal axis represents time.

As shown in the graph of [ rise up ] of fig. 3, when the pressure of the medium rises and exceeds the upper limit value, the drain solenoid pump 24 is turned on for only a certain time. Accordingly, the pressure in the pipes 11 and 12 and the branch pipe 16 can be reduced. Since the saturation vapor pressure at each temperature of the medium can be obtained, the upper limit value of each temperature of the medium can be set so that the pressure can be controlled to be appropriate, that is, within a certain range, regardless of the temperature of the medium. In addition, when the pressure of the medium rises again, the same operation may be repeated. In fig. 3, the discharge solenoid valve 24 is opened to reduce the pressure of the medium to the lower limit value and then increase the pressure of the medium, but the pressure of the medium may be increased without reducing the pressure to the lower limit value.

As shown in the graph of [ when stabilized ] of fig. 3, when the pressure of the medium is stabilized between the upper limit value and the lower limit value, the pressurizing pump 32 is not operated. In addition, the drain electromagnetic pump 24 does not need to be operated.

As shown in the graph of fig. 3 [ at the time of drop ], when the pressure of the medium decreases and falls below the lower limit value, the pressurizing pump 32 is turned on for only a certain time. Accordingly, since the saturation vapor pressure at each temperature of the medium can be obtained, the lower limit value of each temperature of the medium can be set so that the pressure can be controlled to be appropriate regardless of the temperature of the medium. In addition, when the pressure of the medium drops again, the same operation may be repeated.

Fig. 4 is a timing chart showing the operation of the mold temperature controller 100 according to the present embodiment when the pressure is increased. Fig. 4 shows, from the upper stage to the lower stage, the pressure of the medium, the operating state of the pressure pump 32, and the operating state of the drain solenoid valve 24 in this order. Fig. 4 shows the operation states of example 1, example 2, and example 3. In addition, the horizontal axis represents time.

In example 1, an example is shown in which the pressurizing pump 32 is not operated when the pressure of the medium rises. That is, when the pressure of the medium exceeds the upper limit value, the pressure of the medium in the pipes 11 and 12 and the branch pipe 16 is excessively reduced to be lower than the lower limit value by opening the electromagnetic drain pump 24 for a certain period of time.

In example 2, an example is shown in which the pressurizing pump 32 is operated when the pressure of the medium rises. That is, it is shown that when the pressure of the medium exceeds the upper limit value, the drain solenoid valve 24 is opened for a certain time, and the pressurizing pump 32 is driven after the drain solenoid valve 24 is opened. At this time, the pressure of the medium in the pipes 11 and 12 and the branch pipe 16 is lower than the lower limit value before the pressurizing pump 32 pressurizes and exerts the effect.

In example 3, an operation is shown for preventing the case where the medium pressure is lower than the lower limit value as in the above-described examples 1 and 2. That is, by driving the pressure pump 32 at the node at which the drain solenoid valve 24 is opened or at a node before the node, the pressure in the pipes 11 and 12 and the branch pipe 16 is increased before being reduced by opening the drain solenoid valve 24, and the pressure of the medium can be prevented from falling below the lower limit value. The pressure of the generation medium can be prevented from being lower than the saturated vapor pressure calculated by the pressure calculation unit 52.

Fig. 5 is a flowchart showing a processing procedure of the mold temperature controller 100 according to the present embodiment. For convenience, the process main body is set as the pressure control unit 50. The pressure control unit 50 closes the drain solenoid valve 24 (i.e., step S11), and detects the temperature of the medium by the temperature sensor 71 (i.e., step S12). The pressure control unit 50 calculates the saturated vapor pressure of the medium based on the measured temperature (i.e., step S13).

The pressure control unit 50 detects the pressure of the medium by the pressure sensor 63 (i.e., step S14), and determines whether or not the detected pressure of the medium is equal to or less than a lower limit value corresponding to the calculated saturated vapor pressure (i.e., step S15). When the detected pressure of the medium is equal to or lower than the lower limit value (YES in step S15), the pressure control unit 50 drives the pressure pump 32 for a certain time (step S16). When the detected pressure of the medium is not lower than the lower limit value (i.e., NO in step S15), the pressure control unit 50 executes the process of step S17 described below without executing the process of step S16.

The pressure control unit 50 determines whether or not the detected pressure of the medium is equal to or higher than the upper limit value corresponding to the calculated saturated vapor pressure (i.e., step S17). When the detected pressure of the medium is equal to or higher than the upper limit value (YES in step S17), the pressure control unit 50 drives the pressurizing pump 32 for a certain time (step S18) before the node at which the drain solenoid valve 24 is opened, and then drives the drain solenoid pump 24 for a certain time (step S19). When the detected pressure of the medium is not equal to or higher than the upper limit value (i.e., NO in step S17), the pressure control unit 50 executes the following processing in step S20 without executing the processing in steps S18 and S19.

The pressure control unit 50 determines whether or not the processing is completed (i.e., step S20), and if the processing is not completed (i.e., NO in step S20), the processing is continued after step S12, and if the processing is completed (i.e., YES in step S20), the processing is terminated.

In the above embodiment, water may be used as the medium, but oil may be used instead of water.

In the above-described embodiment, the die temperature controller was described as an example of the pressure control device, but the pressure control device is not limited to the die temperature controller, and the present embodiment can be applied to any device as long as it controls the pressure of the medium.

At least some of the above embodiments may be arbitrarily replaced or combined.

Claims

1. A pressure control device for controlling the pressure of a medium circulating in a circulation path provided between a suction side and a discharge side of a pump and a die, respectively, the pressure control device comprising:

a temperature detection unit that detects a temperature of the medium in the circulation path; and

a pressure calculation unit that calculates a saturated vapor pressure of the medium in the circulation path based on the temperature detected by the temperature detection unit; and

a pressure control unit for controlling the pressure of the medium on the suction side of the pump to be equal to or higher than the saturated vapor pressure calculated by the pressure calculation unit,

the pressure control unit controls the pressure of the medium to be equal to or higher than a saturation vapor pressure corresponding to each temperature change of the medium circulating through the circulation path.

2. The pressure control device of claim 1, further comprising:

a water feed pipe connected to a water feed port and communicating with a circulation path on a suction side of the pump; and

a pressurizing pump installed in the middle of the water supply pipe,

and a pressure control unit that controls the pressure of the medium to be equal to or higher than a saturated vapor pressure by the pressurization of the pressurization pump.

3. The pressure control device of claim 2, further comprising:

a pressure detection unit that detects a pressure of the medium on a suction side of the pump; and

and a driving unit that drives the pressurizing pump when the pressure detected by the pressure detecting unit is equal to or less than a predetermined lower limit value.

4. The pressure control apparatus according to claim 3, further comprising:

a drain pipe connected to the drain port and communicating with the circulation path on the suction side of the pump; and

a drain valve installed midway in the drain pipe; and

and a drain valve control unit that controls the drain valve to open when the pressure detected by the pressure detection unit is equal to or higher than a predetermined upper limit value.

5. The pressure control apparatus according to claim 4,

the driving unit drives the pressurizing pump before a node at which the drain valve is opened when the drain valve control unit controls the drain valve to be opened.

6. The pressure control apparatus according to any one of claims 3 to 5,

the pressure pump is an electromagnetic pump,

the driving unit drives the pressure pump by using a dc pulse having a desired cycle and duty ratio.