JP2017116387A - Differential pressure change amount calculation device and differential pressure change amount calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a differential pressure change amount calculation device capable of accurately calculating a differential pressure change amount caused by a leak from a sealed space.SOLUTION: In leak inspection of a workpiece W, two leak inspections are performed at a time interval. On the basis of a first differential pressure change amount dPa1 and first workpiece temperature change amount dTw1 obtained in the first leak inspection and a second differential pressure change amount dPa2 and second workpiece temperature change amount dTw2 obtained in the second leak inspection, an actual differential pressure change amount dPa is calculated which is a time change amount of the differential pressure between the pressure of a sealed space WS and that of a comparison space CS, and is a time change amount of the differential pressure caused by a leak from the sealed space WS.SELECTED DRAWING: Figure 2C

Description

  The present invention calculates a differential pressure change amount for calculating a temporal change amount (differential pressure change amount) of a differential pressure between a pressure of a sealed space formed in a work and a pressure of a comparison space formed in a master work. The present invention relates to a device and a differential pressure change amount calculation method.

  A tracer gas method using helium gas is exemplified as one method for inspecting the presence or absence of leakage in a container or the like in which a large-capacity sealed space is formed. However, the leak inspection using the tracer gas method has a problem that the equipment cost and running cost are high. Therefore, the differential pressure between the pressure in the sealed space formed on the workpiece to be inspected and the pressure in the comparison space formed on the master workpiece is measured and the time variation (differential pressure variation) of the measured differential pressure is calculated. A differential pressure type leak inspection method for inspecting whether there is a leak in the sealed space based on the calculated differential pressure change amount is often used.

  When a high pressure higher than atmospheric pressure is applied to the sealed space by the differential pressure type leak inspection method, the gas in the sealed space is compressed, and the temperature of the gas in the sealed space rises due to the compression heat. Therefore, during the measurement of the differential pressure between the pressure in the sealed space and the pressure in the comparison space, the temperature of the gas in the sealed space changes (decreases) due to heat release from the compression heat, and the pressure in the sealed space is caused by the temperature change. Changes. That is, the differential pressure change amount includes the differential pressure change amount due to the temperature change of the gas in the sealed space and the differential pressure change amount due to the leak in the sealed space. Therefore, in the differential pressure type leak inspection method, the differential pressure change amount excluding the differential pressure change amount due to the temperature change of the gas in the sealed space, that is, the differential pressure change amount due to the leak in the sealed space is calculated. Is desirable. In the past, attempts have been made to calculate the amount of change in differential pressure due to leakage in a sealed space by various methods.

  Japanese Patent Application Laid-Open No. H10-227707 discloses a pressure differential equation including a heat radiation characteristic term representing a heat radiation characteristic of a workpiece acquired in advance and a leakage characteristic term representing a gas leakage from the sealed space of the workpiece, with the pressure of the sealed space in the workpiece. A leak inspection method is disclosed in which a coefficient relating to a leak characteristic term of a differential pressure equation is obtained by substituting, and whether or not there is a leak in the sealed space is determined using the coefficient relating to the obtained leak characteristic term. Patent Document 2 discloses a method for obtaining a drift amount of the internal pressure of the work caused by heat radiation from the temperature difference between the work temperature and the temperature of the jig for fixing the work.

Patent No. 4056818 JP 2002-022592 A

(Problems to be solved by the invention)
According to Patent Literature 1, the amount of change in differential pressure due to leakage in a sealed space is calculated using a differential pressure equation formulated in advance including a heat dissipation characteristic term and a leakage characteristic term. Here, the amount of change in the differential pressure due to the temperature change of the gas in the sealed space also changes due to the temperature change in the environment surrounding the workpiece. The differential pressure equation shown in Patent Document 1 does not take into account the temperature change of the environment around the workpiece. Therefore, when the temperature change of the surrounding environment of the workpiece occurs, when the method described in Patent Document 1 is applied, the coefficient relating to the leakage characteristic term cannot be accurately calculated. For this reason, the amount of change in differential pressure due to leak in the sealed space cannot be calculated accurately, and therefore, a highly accurate leak test cannot be performed. Further, the method described in Patent Document 1 can be applied only within a temperature range in which a preset differential pressure equation can be established, and when applied in other temperature ranges, the calculated differential pressure change Since the quantity error increases, a highly accurate leak test cannot be performed.

  According to Patent Document 2, the differential pressure drift amount is obtained in consideration of the heat radiation of the gas in the sealed space via the jig for fixing or sealing the workpiece. However, as described above, the amount of change in the differential pressure caused by the temperature change of the gas in the sealed space changes due to the temperature change in the environment around the workpiece. In the method disclosed in Patent Document 2, the temperature change due to heat radiation from the workpiece to the jig is taken into account in obtaining the drift amount of the differential pressure, but the temperature change in the surrounding environment of the workpiece is not taken into consideration. Therefore, similarly to Patent Document 1, even when the method described in Patent Document 2 is applied in the case where the temperature change of the surrounding environment of the workpiece occurs, the amount of change in the differential pressure caused by the leak in the sealed space is more accurate. Therefore, it is not possible to calculate a leak test with high accuracy.

  An object of the present invention is to provide a differential pressure change amount calculation device and a differential pressure change amount calculation method capable of calculating a differential pressure change amount caused by a leak in an enclosed space more accurately than in the past.

(Means for solving the problem)
The present invention provides a first pipe (4a) having one end connected to the pressure source (2) and the other end connected to a sealed space (WS) formed in the work (W), and the first pipe. An intervening first on-off valve (5a) and a comparison space (one end disposed downstream of the first on-off valve and communicating with the sealed space and the other end formed in the master work (6)) The second pipe (4b) communicated with CS), the second on-off valve (5b) interposed in the second pipe, and the differential pressure (ΔPs) between the pressure in the sealed space and the pressure in the comparison space are detected. The pressure in the sealed space is controlled by controlling the differential pressure sensor (7), the workpiece temperature sensor (9a) for detecting the workpiece temperature (Tw), and the opening / closing operation of the first opening / closing valve and the opening / closing operation of the second opening / closing valve. And a control unit (10) for calculating a temporal change amount of a differential pressure between the pressure in the comparison space and The unit opens the first on-off valve and the second on-off valve to connect the pressure source, the sealed space, and the comparison space, and a predetermined test pressure (Pt) is applied from the pressure source to the sealed space and the comparison space. As described above, the pressure adjustment process (S2, S4) for adjusting the pressure of the sealed space and the pressure of the comparison space, and the first on-off valve is closed after the pressure adjustment process is performed, and the communication between the pressure source and the sealed space is A valve closing process (S6, S8) that shuts off the communication between the pressure source and the comparison space and closes the second on-off valve to shut off the communication between the sealed space and the comparison space, and is detected by the differential pressure sensor. The first differential pressure change amount (dPa1), which is the amount that the differential pressure has changed during the first period (tt1) in which the first on-off valve and the second on-off valve are closed by executing the valve closing process, and the workpiece This is the amount that the temperature of the workpiece detected by the temperature sensor has changed within the first period. First state acquisition processing (S12, S13) for acquiring the first workpiece temperature change amount (dTw1), and the differential pressure detected by the differential pressure sensor is closed by the first on-off valve and the second on-off valve. The second differential pressure change amount (dPa2), which is the period and the amount changed in the second period (tt2) after the first period, and the workpiece temperature detected by the workpiece temperature sensor are within the second period. The second state acquisition process (S22, S23) for acquiring the second workpiece temperature change amount (dTw2) that is the amount changed to the first, the first differential pressure change amount, the first workpiece temperature change amount, the second differential pressure change amount. Based on the second work temperature change amount, the actual pressure difference is the time change amount of the differential pressure between the pressure of the sealed space and the pressure of the comparison space, and the time change amount of the differential pressure caused by the leak of the sealed space. The actual differential pressure change amount calculation process (S24) for calculating the change amount (δPa) is executed. That provides a differential pressure change amount calculation unit (1).

  According to the differential pressure change amount calculation apparatus according to the present invention, the differential pressure change amount and the workpiece temperature change amount in two different inspection periods (first period and second period) are acquired. Here, since the volume of the sealed space is always constant, the ratio of the pressure change amount of the sealed space and the temperature change amount of the gas in the sealed space is constant according to Boyle-Charles' law. Therefore, the pressure change amount obtained in two different periods and the workpiece are obtained by regarding the pressure change amount in the enclosed space as the differential pressure change amount and considering the temperature change amount of the gas in the sealed space as the workpiece temperature change amount. From the temperature change amount, it is possible to calculate the differential pressure change amount when the workpiece temperature change amount is 0, that is, when there is no temperature change of the gas in the sealed space. The differential pressure change amount calculated in this way is a differential pressure change amount (actual differential pressure change amount) generated due to leakage in the sealed space.

  That is, according to the present invention, the differential pressure change amount excluding the influence of the temperature change on the differential pressure change is calculated from the workpiece temperature change amount and the differential pressure change amount acquired in two different periods. For this reason, it is possible to calculate the differential pressure change amount (actual differential pressure change amount) caused by the leak in the sealed space more accurately than in the past.

  In addition, changes in external factors such as the temperature of the environment surrounding the work are reflected in changes in the work temperature. In the present invention, the amount of change in workpiece temperature is taken into account when calculating the amount of change in differential pressure (actual amount of change in actual differential pressure) due to leakage in the sealed space. Therefore, according to the present invention, when the temperature of the environment around the workpiece changes, and even when other external factors change, the workpiece is sealed more accurately than before by taking the workpiece temperature change into consideration. It is possible to calculate a differential pressure change amount (actual differential pressure change amount) caused by a space leak.

In the present invention, the first differential pressure change amount is dPa1, the first work temperature change amount is dTw1, the first period is tt1, the second differential pressure change amount is dPa2, the second work temperature change amount is dTw2, and the second work temperature change amount is dTw2. When the period is tt2 and the actual differential pressure change amount is δPa, the control unit performs the following formula δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) / (dTw1) in the actual differential pressure change calculation process. /Tt1-dTw2/tt2).(dTw2/tt2)
Thus, the actual differential pressure change amount δPa may be calculated. According to this, based on Boyle-Charles' law, the actual differential pressure change amount can be calculated more accurately than in the past.

  Further, the control unit may execute a leak determination process (S25, S26, S27) for determining whether or not there is a leak in the sealed space of the workpiece based on the actual differential pressure change amount. According to this, the presence or absence of leakage in the sealed space of the workpiece can be determined more accurately than in the past based on the actual differential pressure change amount. In this case, the control unit may determine whether there is a leak in the sealed space of the workpiece based on whether the actual differential pressure change amount is equal to or less than a predetermined threshold differential pressure change amount in the leak determination process. . Further, in the leak determination process, the control unit determines that the sealed space is not leaking when the actual differential pressure change amount is equal to or less than the threshold differential pressure change amount, and the actual differential pressure change amount is the threshold differential pressure change amount. It is good to judge that the sealed space is leaking when it is larger than the above.

  The control unit opens the second on-off valve for a predetermined time while the first on-off valve is closed after the execution of the first state acquisition processing and before the execution of the second state acquisition processing. It is preferable to execute an equilibrium process (S15) for communicating with the comparison space. In order to continuously acquire two differential pressure changes (first differential pressure change and second differential pressure change), a differential pressure sensor having a large differential pressure measurement width is required. On the other hand, as in the present invention, after acquiring the first differential pressure change amount in the first state acquisition process, the closed space and the comparison space are once communicated to make both spaces have the same pressure. A differential pressure change amount (a first differential pressure change amount and a second differential pressure change amount) can be acquired twice using a differential pressure sensor having a differential pressure measurement width. In addition, when performing this equilibrium process, the process (S18) which closes a 2nd on-off valve is performed before execution of a 2nd state acquisition process.

  The pressure adjustment processing includes pressurization processing (S1, S2) for pressurizing the sealed space and the comparison space so that the pressure in the sealed space and the comparison space becomes the first pressure (P1) higher than the test pressure, and pressurization. It is preferable to include a decompression process (S4) for decompressing the sealed space and the comparison space so that the pressure in the sealed space and the comparison space becomes the test pressure after the execution of the process. According to this, the gas in the sealed space can be rapidly cooled by adiabatic expansion by the decompression process. For this reason, the heat radiation of the gas in the sealed space to the workpiece can be promoted, whereby the temperature of the gas in the sealed space and the temperature of the workpiece can be brought closer to each other early. Therefore, the temperature change amount of the gas in the sealed space can be brought close to the work temperature change amount, and as a result, the calculation accuracy of the actual differential pressure change amount calculated using the work temperature change amount can be improved. In addition, the equilibration time for bringing the workpiece temperature close to the temperature of the gas in the sealed space can be shortened. Therefore, the work inspection time can be shortened.

  The present invention also provides a sealed space (WS) formed in the work (W) and a comparison space (CS) formed in the master work (6) by communicating with the pressure source (2). Pressure adjustment step (S2, S4) for adjusting the pressure in the sealed space and the pressure in the comparison space so that the pressure in the comparison space and the pressure in the comparison space become the same test pressure (Pt), and communication between the pressure source and the sealed space; The blocking step (S6, S8) for blocking the communication between the pressure source and the comparison space, and the differential pressure between the pressure in the sealed space and the pressure in the comparison space are determined by the blocking step. The amount of change in the first differential pressure (dPa1), which is the amount changed within the first period (tt1) in which communication with the comparison space is blocked, and the amount of change in the workpiece temperature (Tw) within the first period The first workpiece temperature change amount (dtw1) is acquired. The first state acquisition step (S12, S13) and the pressure difference (ΔPs) between the pressure in the sealed space and the pressure in the comparison space block the communication between the pressure source and the sealed space and the communication between the pressure source and the comparison space. The amount of change in the second differential pressure (dPa2), which is the amount changed in the second period (tt2) after the first period, and the amount in which the temperature of the work changed in the second period A second state acquisition step (S22, S23) for acquiring a second workpiece temperature change amount (dTw2), a first differential pressure change amount, a first workpiece temperature change amount, a second differential pressure change amount, and a second Based on the workpiece temperature variation, the actual differential pressure variation (δPa), which is the temporal variation of the differential pressure between the pressure in the sealed space and the pressure in the comparison space and is the temporal variation in the differential pressure due to leakage in the sealed space. ) Calculating the actual differential pressure change amount calculating step (S24). The law provides.

In this case, the actual differential pressure change amount calculating step includes the first differential pressure change amount dPa1, the first work temperature change amount dTw1, the first period tt1, the second differential pressure change amount dPa2, and the second work temperature change. When the amount is dTw2, the second period is tt2, and the actual differential pressure change amount is δPa, the following formula δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) / (dTw1 / tt1-dTw2 / tt2). (DTw2 / tt2)
Thus, the step of calculating the actual differential pressure change amount δPa is good.

  In addition, the differential pressure change amount calculation method according to the present invention may include a leak determination step (S25) for determining whether there is a leak in the sealed space of the workpiece based on the actual differential pressure change amount. Further, an equilibration step (S15) is performed after the first state acquisition step and before the second state acquisition step, and the pressure in the sealed space and the pressure in the comparison space are matched by communicating the sealed space and the comparison space. It is good to include. The pressure adjusting step includes a pressurizing step (S1, S2) for applying a first pressure (P1) higher than the test pressure from the pressure source to the sealed space and the comparison space, and the pressure in the sealed space and the comparison space is the test pressure. And a pressure reducing step (S4) for reducing the pressure in the sealed space and the comparison space.

  Also by the differential pressure change amount calculation method according to the present invention, the same effect as the above-described differential pressure change amount calculation device according to the present invention is achieved.

It is the schematic which shows the structure of the leak inspection apparatus which concerns on this embodiment. It is a part of flowchart which shows the flow of the leak test process routine which a control apparatus performs. It is a part of flowchart which shows the flow of the leak test process routine which a control apparatus performs. It is a part of flowchart which shows the flow of the leak test process routine which a control apparatus performs. The pressure P, differential pressure ΔPs, work temperature Tw, open / close state of the first on-off valve 5a, open / close state of the second on-off valve 5b when the control device executes the above-described leak inspection processing routine. 4 is a graph showing changes over time in the opening state of the third on-off valve 5c and the estimated value of the temperature Ta of the gas in the sealed space WS. It is a graph which shows the relationship between differential pressure | voltage change amount (DELTA) Ps and workpiece | work temperature change amount dTw.

  Hereinafter, embodiments of the present invention will be described. In the present embodiment, a leak inspection apparatus as a differential pressure change amount calculation apparatus according to the present invention and a leak inspection method as a differential pressure change amount calculation method according to the present invention will be described. Here, the workpiece W, which is a leak inspection target, is a container-like member in which a large-capacity sealed space WS is formed. For example, a large hot water storage container or the like can be exemplified as the work W to be inspected. The capacity of the sealed space is, for example, 30 liters, but is not limited thereto, and may be larger or smaller. Further, the sealed space WS is a space configured to maintain the pressure when a predetermined pressure is applied to the space, and may be a space partitioned only by the wall surface of the workpiece W. Alternatively, it may be a space defined by the wall surface of the workpiece W and the wall surfaces of other members.

  FIG. 1 is a schematic diagram showing a configuration of a leak inspection apparatus according to the present embodiment. As shown in FIG. 1, the leak inspection apparatus 1 according to the present embodiment includes a pressure regulator 3, a first pipe 4a, a second pipe 4b, a first on-off valve 5a, a second on-off valve 5b, A master work 6, a differential pressure sensor 7, and a control device 10 are provided.

  The pressure regulator 3 is connected to the pressure source 2. The pressure source 2 supplies the pressure regulator 3 with a high-pressure gas to be supplied to the sealed space WS formed in the work W to be inspected. High pressure air can be exemplified as the high pressure gas. The pressure regulator 3 regulates the high-pressure gas supplied from the pressure source 2 to a predetermined pressure, and discharges the regulated gas from a discharge port (not shown).

  One end of the first pipe 4 a is connected to the discharge port of the pressure regulator 3. The other end of the first pipe 4 a opens into the sealed space WS of the workpiece W. Accordingly, the first pipe 4 a is configured such that one end is connected to the pressure source 2 via the pressure regulator 3 and the other end is connected to the sealed space WS formed in the workpiece W.

  A first on-off valve 5a is interposed in the first pipe 4a. When the first on-off valve 5a is opened, the gas flow in the first pipe 4a is permitted, and when the first on-off valve 5a is closed, the gas flow in the first pipe 4a is shut off. Therefore, when the first on-off valve 5a is opened, the gas discharged from the pressure source 2 via the pressure regulator 3 flows through the first pipe 4a and is supplied to the sealed space WS of the workpiece W and the sealed space. A predetermined high pressure adjusted by the pressure regulator 3 is applied to WS.

  The first opening / closing valve 5a is located in the middle of the first pipe 4a and downstream of the position where the first opening / closing valve 5a is interposed (that is, the side close to the sealed space WS of the workpiece W). One end of the second pipe 4b communicates with the downstream position of the mounted position. The other end of the second pipe 4 b communicates with a comparison space CS formed in the master work 6. Accordingly, the second pipe 4b connects the comparison space CS formed in the master work 6 to a position downstream of the position where the first on-off valve 5a is interposed, which is in the middle of the first pipe 4a. Configured. In addition, a midway position of the first pipe 4a and a position downstream of the first on-off valve 5a communicates with the sealed space WS. Accordingly, one end of the second pipe 4b communicates with the sealed space WS. That is, the second pipe 4b is configured such that one end thereof communicates with the sealed space WS and the other end communicates with the comparison space CS. Further, a second on-off valve 5b is interposed in the second pipe 4b. When the second on-off valve 5b is opened, the gas flow in the second pipe 4b is permitted, and when the second on-off valve 5b is closed, the gas flow in the second pipe 4b is shut off. Therefore, when the second on-off valve 5b is opened, the closed space WS of the workpiece W and the comparison space CS of the master workpiece 6 communicate with each other via the first pipe 4a and the second pipe 4b, and the two spaces WS and CS are The same pressure is applied. The master work 6 is configured so that no leak occurs in the internal comparison space CS. Further, the master work 6 has an extremely large contact area of gas in the comparison space CS with respect to the volume of the comparison space CS (area where the gas in the comparison space CS contacts the wall surface of the master work 6) compared to the work W. It is comprised so that it may become. For example, a plurality of ring-shaped protrusions are stacked on the inner wall surface of the master work 6 so that the contact area becomes very large with respect to the volume of the comparison space CS.

  As shown in FIG. 1, the differential pressure sensor 7 includes a casing 71 in which a space is formed, a diaphragm 72 that hermetically divides the space in the casing 71 into a first space 71a and a second space 71b, And a detection unit 73 that detects the movement of the diaphragm 72. The first space 71a communicates with the downstream position of the position where the second pipe 4b communicates with the middle position of the first pipe 4a. The second space 71b is a position in the middle of the second pipe 4b and downstream of the position where the second opening / closing valve 5b is interposed (the side communicating with the comparison space CS), that is, the second opening / closing valve 5b. It communicates with the downstream position. The differential pressure sensor 7 detects a differential pressure between the pressure in the first space 71 a and the pressure in the second space 71 b based on the movement of the diaphragm 72. Here, the first space 71a communicates with the sealed space WS, and the second space 71b communicates with the comparison space CS. Therefore, the differential pressure sensor 7 detects a differential pressure ΔPs between the pressure in the sealed space WS of the workpiece W and the pressure in the comparison space CS of the master workpiece 6. The detected differential pressure information is transmitted to the control device 10.

  In addition, one end of the third pipe 4c communicates with a position in the middle of the first pipe 4a and in the vicinity of a portion communicating with the sealed space WS. The other end of the third pipe 4c is open to the atmosphere. A third on-off valve 5c is interposed in the third pipe 4c. When the third on-off valve 5c is opened, the gas in the sealed space WS is opened to the atmosphere via the third pipe 4c. Further, when both the second on-off valve 5b and the third on-off valve 5c are opened, the gas in the sealed space WS and the gas in the comparison space CS are released to the atmosphere via the third pipe 4c.

  The leak inspection apparatus 1 according to the present embodiment includes a workpiece temperature sensor 9a and a pressure sensor 9b. The work temperature sensor 9a is attached to the work W and detects the temperature of the work W (work temperature Tw). The pressure sensor 9b is attached at a position midway through the first pipe 4a and downstream of the position where the first space 71a of the differential pressure sensor 7 communicates, and detects the pressure at the attachment position. The space in the first pipe 4a where the pressure sensor 9b detects the pressure communicates with the sealed space WS as shown in FIG. Therefore, the pressure sensor 9b detects the pressure P in the sealed space WS. The temperature information or pressure information detected by each sensor is transmitted to the control device 10.

  The control device 10 includes a microcomputer including a CPU, a ROM, and a RAM as main components. The control device 10 inputs the differential pressure information from the differential pressure sensor 7, the temperature information from the workpiece temperature sensor 9a, and the pressure information from the pressure sensor 9b, and the operation of the pressure regulator 3, the first on-off valve 5a, the first The opening / closing operation of the second opening / closing valve 5b and the third opening / closing valve 5c is controlled. Further, as will be described later, the control device 10 controls the operation of the pressure regulator 3 and the opening / closing operations of the first opening / closing valve 5a and the second opening / closing valve 5b, thereby controlling the pressure in the sealed space WS and the pressure in the comparison space CS. And a differential pressure change amount (actual differential pressure change amount δPa) caused by a leak in the sealed space, and a sealed space based on the calculated actual differential pressure change amount δPa. It is determined whether there is a WS leak.

  When performing the leak inspection of the sealed space WS formed in the workpiece W to be inspected using the leak inspection apparatus 1 having the above configuration, first, the worker places the sealed space WS of the workpiece W into the first pipe. The workpiece W is set in the leak inspection apparatus 1 so as to communicate with 4a. Thereafter, the operator presses a start switch provided in the leak inspection apparatus 1. Then, the control device 10 executes a leak inspection process. 2A, 2B, and 2C are flowcharts showing the flow of a leak inspection processing routine executed by the control device 10.

  When the leak inspection processing routine starts, the control device 10 firstly, in step (hereinafter abbreviated as S) 1 in FIG. 2A, the discharge pressure of the pressure regulator 3 is higher than the predetermined test pressure Pt. The pressure regulator 3 is controlled so as to be a first pressure P1 that is predetermined as the pressure.

  Next, the control device 10 outputs an opening operation signal to the first opening / closing valve 5a and the second opening / closing valve 5b, and outputs a closing operation signal to the third opening / closing valve 5c (S2). Thereby, the first on-off valve 5a is opened and the third on-off valve 5c is closed. In the initial state, the second on-off valve 5b is open. Therefore, the open state of the second on-off valve 5b is maintained by the process of S2.

  When the first on-off valve 5a is opened by the execution of the process of S2, the gas discharged from the pressure regulator 3 flows through the first pipe 4a and is supplied to the sealed space WS of the workpiece W, and the sealed space WS. Is pressurized, and the pressure in the sealed space WS is increased to the first pressure P1. At this time, since the second on-off valve 5b is opened, the sealed space WS and the comparison space CS are in communication. Therefore, the gas discharged from the pressure regulator 3 is also supplied to the comparison space CS via the second pipe 4b, and the pressure in the comparison space CS is increased to the first pressure P1. The process of S1 and S2 is the pressurization process of the present invention, that is, the process of pressurizing the sealed space WS and the comparison space CS so that the pressure of the sealed space WS and the comparison space CS becomes the first pressure P1 higher than the test pressure Pt. Configure.

  Subsequently, the control device 10 determines whether or not the pressure P in the sealed space WS has reached the first pressure P1 based on the pressure information input from the pressure sensor 9b. When the pressure P of the sealed space WS has not reached the first pressure P1 (S3: No), the control device 10 repeats the process of S3. When the pressure P of the sealed space WS reaches the first pressure P1 (S3: Yes), the control device 10 adjusts the pressure so that the discharge pressure of the pressure regulator 3 becomes the test pressure Pt lower than the first pressure P1. The device 3 is controlled (S4). By executing the process of S4, the sealed space WS and the comparison space CS are depressurized, and the pressure P of the sealed space WS and the pressure of the comparison space CS are set to the test pressure Pt. The process of S4 constitutes a decompression process of the present invention, that is, a process of decompressing the sealed space WS and the comparison space CS so that the pressure in the sealed space WS and the comparison space CS becomes the test pressure Pt after the pressurization process is performed. Further, the processes of S2 and S4 are the pressure adjustment process of the present invention, that is, the first on-off valve 5a and the second on-off valve 5b are opened, and the pressure source 2, the sealed space WS, and the comparison space CS are communicated. The process of adjusting the pressure of the sealed space WS and the pressure of the comparison space CS is configured such that a predetermined test pressure Pt is applied from the pressure source 2 to the sealed space WS and the comparison space CS.

  Next, the control device 10 determines whether or not the pressure P in the sealed space WS has decreased to the test pressure Pt based on the pressure information input from the pressure sensor 9b (S5). When the pressure P of the sealed space WS has not decreased to the test pressure Pt (S5: No), the control device 10 repeats the process of S5. When the pressure in the sealed space WS has decreased to the test pressure Pt (S5: Yes), the control device 10 advances the process to S6.

  In S6, the control device 10 outputs a closing operation signal to the first on-off valve 5a. Thereby, the first on-off valve 5a is closed. When the first on-off valve 5a is closed, the communication between the sealed space WS and the pressure source 2 via the first pipe 4a and the comparison space CS and the pressure source via the first pipe 4a and the second pipe 4b are performed. Communication with 2 is blocked. Thereafter, the control device 10 advances the process to S7.

  In S7, the control device 10 determines whether or not an elapsed time ta after the first opening / closing valve 5a is closed by executing the process of S6 has reached a predetermined first equilibrium time te1. When the elapsed time ta does not reach the first equilibrium time te1 (S7: No), the control device 10 repeats the process of S7. When the elapsed time ta reaches the first equilibrium time te1 (S7: Yes), the control device 10 outputs a closing operation signal to the second on-off valve 5b (S8). As a result, the second on-off valve 5b is closed, the communication between the sealed space WS and the comparison space CS is shut off, and the first measurement of the differential pressure ΔPs by the differential pressure sensor 7 is started. The processing of S6 and S8 is the valve closing processing of the present invention, that is, the first on-off valve 5a is closed after the execution of the pressure adjustment processing, the communication between the pressure source 2 and the sealed space WS, and the pressure source 2 and the comparison space CS. Is closed, and the second on-off valve 5b is closed to block communication between the sealed space WS and the comparison space CS. After executing the process of S8, the control device 10 advances the process to S9 of FIG. 2B.

  In S9, based on the temperature information input from the workpiece temperature sensor 9a, the control device 10 acquires the workpiece temperature Tw immediately after the second opening / closing valve 5b is closed as a workpiece temperature Tw1a by executing the processing in S8. . Thereafter, the control device 10 determines that the elapsed time tb after the second opening / closing valve 5b is closed by executing the process of S8 is a predetermined period, and the first opening / closing valve 5a and the second opening / closing valve 5b are closed. It is determined whether or not the first inspection time tt1, which is a valid period, has been reached (S10). When the elapsed time tb has not reached the first inspection time tt1 (S10: No), the control device 10 repeats the process of S9. When the elapsed time tb reaches the first inspection time tt1 (S10: Yes), the control device 10 advances the process to S11. In S11, the control device 10 acquires the workpiece temperature Tw when the elapsed time tb reaches the first inspection time tt1 as the workpiece temperature Tw1b based on the temperature information input from the workpiece temperature sensor 9a.

  Next, the control device 10 acquires the amount of change in the differential pressure ΔPs within the first inspection time tt1 as the first differential pressure change amount dPa1 (S12). Here, the first measurement of the differential pressure ΔPs by the differential pressure sensor 7 is started when the second opening / closing valve 5b is closed by the execution of the process of S8. Since the closed space WS and the comparison space CS are communicated with each other by opening the two on-off valve 5b, the differential pressure ΔPs is zero. Therefore, the amount of change in the differential pressure ΔPs within the first inspection time tt1 is equal to the differential pressure ΔPs at the time when the elapsed time tb reaches the first inspection time tt1. Therefore, the control device 10 can acquire the first differential pressure change amount dPa1 based on the differential pressure ΔPs input from the differential pressure sensor 7 in S12.

  Thereafter, the control device 10 calculates a first workpiece temperature change amount dTw1 (= Tw1a−Tw1b) that is the magnitude of the difference between the workpiece temperature Tw1a acquired in S9 and the workpiece temperature Tw1b acquired in S11 (S13). ). The first workpiece temperature change amount dTw1 is an amount by which the workpiece temperature Tw has changed within the first inspection time tt1.

  The processing of S12 and S13 is the first state acquisition processing of the present invention, that is, the first differential pressure change amount dPa1 that is the amount by which the differential pressure ΔPs detected by the differential pressure sensor 7 has changed within the first inspection time tt1 and The process which acquires the 1st workpiece | work temperature variation | change_quantity dTw1 which is the quantity which the workpiece | work temperature Tw changed within 1st inspection time tt1 is comprised.

  Subsequently, the control device 10 determines whether or not the first differential pressure change amount dPa1 acquired in S12 is equal to or less than the maximum differential pressure change amount dPmax (S14). When the differential pressure change amount is larger than the maximum differential pressure change amount dPmax, it is determined that a large scratch or the like is formed in the workpiece W and the leak amount from the internal sealed space WS is very large. The amount of change in differential pressure to be obtained is predetermined. When the first differential pressure change amount dPa1 is larger than the maximum differential pressure change amount dPmax (S14: No), the control device 10 advances the process to S16, and determines that the sealed space WS of the workpiece W is leaking greatly (large). (Leak determination).

  On the other hand, when the first differential pressure change amount dPa1 is equal to or less than the maximum differential pressure change amount dPmax (S14: Yes), the control device 10 proceeds to S15 and outputs an opening operation signal to the second on-off valve 5b. As a result, the second on-off valve 5b is opened while the first on-off valve 5a is closed. When the second on-off valve 5b is opened, the sealed space WS and the comparison space CS are communicated, and the pressures in both spaces are made the same. That is, the differential pressure ΔPs is once set to zero. After the process of S15 is the equilibrium process of the present invention, that is, after the execution of the first state acquisition process and before the execution of the second state acquisition process described later, the second open / close valve is kept closed. A process of opening the valve 5b for a predetermined time to make the sealed space WS and the comparison space CS communicate with each other is configured.

  After outputting the opening operation signal to the second on-off valve 5b in S15, the control device 10 advances the process to S17. In S17, the control device 10 determines whether or not an elapsed time tc from the opening of the second on-off valve 5b by the execution of the process of S15 has reached a predetermined second equilibrium time te2. When the elapsed time tc has not reached the second equilibrium time te2 (S17: No), the control device 10 repeats the process of S17. When the elapsed time tc reaches the second equilibrium time te2 (S17: Yes), the control device 10 outputs a closing operation signal to the second on-off valve 5b (S18). As a result, the second on-off valve 5b is closed. When the second on-off valve 5b is closed, the communication between the sealed space WS in the workpiece W and the comparison space CS in the master workpiece 6 is blocked again, and the second time of the differential pressure ΔPs by the differential pressure sensor 7 Measurement starts. Then, the control apparatus 10 advances a process to S19 of FIG. 2C.

  In S19, based on the temperature information input from the workpiece temperature sensor 9a, the control device 10 acquires the workpiece temperature Tw immediately after the second opening / closing valve 5b is closed by executing the processing in S18 as the workpiece temperature Tw2a. Thereafter, the control device 10 determines whether or not an elapsed time td after the second opening / closing valve 5b is closed by executing the process of S18 has reached a predetermined second inspection time tt2 (S20). . The second inspection time tt2 is a period in which the first on-off valve 5a and the second on-off valve 5b are closed and is a time after the first inspection time tt1. When the elapsed time td has not reached the second inspection time tt2 (S20: No), the control device 10 repeats the process of S20. When the elapsed time td reaches the second inspection time tt2 (S20: Yes), the control device 10 advances the process to S21. In S21, the control device 10 acquires, as the workpiece temperature Tw2b, the workpiece temperature Tw when the elapsed time td reaches the second inspection time tt2 based on the temperature information input from the workpiece temperature sensor 9a.

  Next, the control device 10 acquires the amount of change in the differential pressure ΔPs within the second inspection time tt2 as the second differential pressure change amount dPa2 (S22). Here, the second measurement of the differential pressure ΔPs by the differential pressure sensor 7 is started when the second on-off valve 5b is closed by the execution of the process of S18. Since the closed space WS and the comparison space CS are communicated with each other by opening the two on-off valve 5b, the differential pressure ΔPs is zero. Therefore, the amount by which the differential pressure ΔPs changes within the second inspection time tt2 is equal to the differential pressure ΔPs at the time when the elapsed time td reaches the second inspection time tt2. Therefore, the control device 10 can acquire the second differential pressure change amount dPa2 based on the differential pressure ΔPs input from the differential pressure sensor 7 in S22.

  Thereafter, the control device 10 calculates a second workpiece temperature change amount dTw2 (= Tw2a−Tw2b) that is the magnitude of the difference between the workpiece temperature Tw2a acquired in S19 and the workpiece temperature Tw2b acquired in S21 (S23). ). The second workpiece temperature change amount dTw2 is an amount by which the workpiece temperature Tw has changed within the second inspection time tt2.

  The processing of S22 and S23 is the second state acquisition processing of the present invention, that is, the second differential pressure change amount dPa2 that is the amount by which the differential pressure ΔPs detected by the differential pressure sensor 7 has changed within the second inspection time tt2. The process which acquires 2nd workpiece | work temperature variation | change_quantity dTw2 which is the quantity which the workpiece | work temperature Tw changed within 2nd inspection time tt2 is comprised.

Subsequently, the control device 10 proceeds to S24, and calculates the actual differential pressure change amount δPa using the following equation.
δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) / (dTw1 / tt1-dTw2 / tt2). (dTw2 / tt2)
The actual differential pressure change amount δPa will be described later.

  Next, the control device 10 determines whether or not the actual differential pressure change amount δPa calculated in S24 is equal to or less than the threshold differential pressure change amount δPth (S25). The threshold differential pressure change amount δPth is determined in advance as an upper limit value of the differential pressure change amount per unit time at which it can be determined that no leak has occurred in the sealed space WS. When the actual differential pressure change amount δPa is equal to or less than the threshold differential pressure change amount δPth (S25: Yes), the control device 10 determines that there is no leak (no leak) in the sealed space WS and passes. A determination is made (S26). On the other hand, when the actual differential pressure change amount δPa is larger than the threshold differential pressure change amount δPth (S25: No), the control device 10 determines that a leak has occurred (leaked) in the sealed space WS. Then, a leak determination (failure determination) is performed (S27). The processes of S25, S26, and S27 constitute the leak determination process and the leak determination process of the present invention, that is, the process and the process of determining whether there is a leak in the sealed space WS of the workpiece W based on the actual differential pressure change amount δPa. .

  After performing any of the determinations (acceptance determination, leak determination, large leak determination) in S26, S27, and S16, the control device 10 proceeds to S28 and performs the second on-off valve 5b and the third on-off valve 5c. Outputs an open operation signal. As a result, the second opening / closing valve 5b is opened to connect the sealed space WS and the comparison space CS, and the third opening / closing valve 5c is opened to cause the gas in the sealed space WS and the gas in the comparison space CS to be in the atmosphere. Opened. Thereafter, the control device 10 ends this routine and ends the leak inspection of the sealed space WS of the workpiece W.

  As can be seen from the above processing flow, in the present embodiment, two leak inspections (differential pressure measurement) are performed intermittently with a time interval for one workpiece W. Further, based on the temperature change amount and the differential pressure change amount obtained in each leak test, the actual differential pressure change amount δPa is calculated in S24. Then, based on the calculated actual differential pressure change amount δPa, it is determined whether or not there is a leak in the sealed space WS.

  FIG. 3 shows the pressure P, the differential pressure ΔPs, the workpiece temperature Tw, the open / close state of the first on-off valve 5a, and the second open / close state when the control device 10 executes the above-described leak inspection processing routine. It is a graph which shows each time change of the open / close state of the valve 5b, the open / close state of the third open / close valve 5c, and the estimated value of the temperature Ta of the gas in the sealed space WS. 3A is a graph showing the time change of the pressure P (pressure in the sealed space WS), FIG. 3B is a graph showing the time change of the differential pressure ΔPs, and FIG. 3C is a time change of the workpiece temperature Tw. 3 (d) is a graph showing the time change of the open / close state of the first open / close valve 5a, FIG. 3 (e) is a graph showing the time change of the open / close state of the second open / close valve 5b, and FIG. 3 (f). ) Is a graph showing the time change of the open / close state of the third on-off valve 5c, and FIG. 3G is a graph showing the time change of the estimated value of the temperature Ta of the gas (air) in the sealed space WS of the work W.

  As shown in FIG. 3, at time t0, the discharge pressure of the pressure regulator 3 is adjusted to the first pressure P1 higher than the test pressure Pt (S1). At time t0, the first on-off valve 5a and the second on-off valve 5b are open, and the third on-off valve 5c is closed. Therefore, the sealed space WS formed in the work W and the comparison space CS formed in the master work 6 communicate with the pressure source 2 via the pressure regulator 3. Accordingly, the pressure P in the sealed space WS (and the pressure in the comparison space CS) rises rapidly and is pressurized to the first pressure P1 (pressurization step). With this pressurization, the gas in the sealed space WS is compressed and the temperature Ta rises, thereby raising the workpiece temperature Tw. Then, at time t1 after time t0, the discharge pressure of the pressure regulator 3 is reduced to the test pressure Pt. As a result, the pressure P in the sealed space WS is reduced, and the pressure P in the sealed space WS (and the pressure in the comparison space CS) is adjusted to the test pressure Pt (depressurization step). As the pressure is reduced, the temperature Ta of the gas in the sealed space WS decreases due to adiabatic expansion, and thus the workpiece temperature Tw also decreases. Thereafter, the temperature Ta and the workpiece temperature Tw gradually decrease due to heat radiation to the outside. By the pressure process and the pressure reduction process described above, the closed space WS formed in the work W and the comparison space CS formed in the master work 6 are communicated with a pressure source, and the pressure of the sealed space WS and the comparison space CS are A pressure adjustment process is configured to adjust the pressure in the sealed space WS and the pressure in the comparison space CS so that the pressure becomes the same test pressure Pt.

  At time t2 after time t1, the first on-off valve 5a is closed (S6). Thereby, the communication between the pressure source 2 and the sealed space WS and the communication between the pressure source 2 and the comparison space CS are both blocked (blocking step). Since the second on-off valve 5b is open from the time t2 until the first equilibrium time te1 elapses, the pressure in the sealed space WS and the pressure in the comparison space CS are made equal. During the first equilibrium time, the heat of the gas in the sealed space WS is radiated to the workpiece W, whereby the workpiece temperature Tw is brought close to the temperature of the gas in the sealed space WS. Then, at time t3 when the first equilibrium time te1 has elapsed from time t2, the second on-off valve 5b is closed (S8). Thereby, the communication between the sealed space WS and the comparison space CS is blocked (blocking step). From this time, the first measurement of the differential pressure ΔPs is started.

  The differential pressure ΔPs is measured during the period from the time t3 until the first inspection time tt1 elapses. Then, at time t4 when the first inspection time tt1 has elapsed from time t3, the amount of change in the differential pressure ΔPs within the first inspection time tt1 (first differential pressure change amount dPa1) and the workpiece temperature Tw are the first. An amount (first workpiece temperature change amount dTw1) changed within the inspection time tt1 is acquired (S12, S13: first state acquisition step).

  At the time t4, the first measurement of the differential pressure ΔPs is completed, and the second on-off valve 5b is opened (S15). As a result, the sealed space WS and the comparison space CS communicate with each other, and the pressure in the sealed space WS and the pressure in the comparison space CS are equalized (equilibrium process). Then, at time t5 when the second equilibrium time te2 has elapsed from time t4, the second on-off valve 5b is closed (S18). Thereby, the communication between the sealed space WS and the comparison space CS is blocked again. From this point, the measurement of the second differential pressure ΔPs is started.

  The differential pressure ΔPs is measured during a period from the time t5 until the second inspection time tt2 elapses. Then, at time t6 when the second inspection time tt2 has elapsed from time t5, the amount that the differential pressure ΔPs has changed within the second inspection time tt2 (second differential pressure change amount dPa2) and the workpiece temperature Tw are second. An amount (second workpiece temperature change amount dTw2) changed within the inspection time tt2 is acquired (S22, S23: second state acquisition step).

  Then, at time t6, the second on-off valve 5b and the third on-off valve 5c are opened, and the inspection is finished. Using the first differential pressure change amount dPa1, the first work temperature change amount dTw1, the second differential pressure change amount dPa2, and the second work temperature change amount dTw2 obtained in the course of the inspection, the actual differential pressure change as described above. The amount δPa is calculated (S24), and based on the calculated actual differential pressure change amount δPa, it is determined whether there is a leak in the sealed space WS (S25, S26, S27).

  By the way, according to Boyle-Charles' law, when the volume is constant, the ratio between the temperature and pressure of the ideal gas is constant. Therefore, the ratio between the temperature change amount per unit time of the ideal gas and the pressure change amount per unit time caused by the temperature change is also constant. Moreover, in this embodiment, as above-mentioned, the master work 6 is the contact area of the gas in the comparison space CS with respect to the volume of the comparison space CS inside (the gas in the comparison space CS contacts the wall surface of the master work 6). Is configured to be much larger than the contact area of the gas in the sealed space WS with respect to the sealed space WS of the workpiece W. Therefore, the heat of the high-pressure gas introduced into the comparison space CS is quickly radiated to the wall surface of the master work 6, and further, the heat of the wall surface of the master work 6 is quickly radiated to the outside. Therefore, the gas in the comparison space CS is set to substantially the same temperature as the external temperature during the first equilibrium time te1. Therefore, the temperature change of the gas in the comparison space CS during the measurement of the differential pressure ΔPs after the elapse of the first equilibrium time te1 becomes negligibly small, and accordingly, the pressure change in the comparison space CS during the measurement of the differential pressure ΔPs. Is also very small. Therefore, the amount of change in differential pressure between the sealed space WS and the comparison space CS can be regarded as the amount of change in pressure of the gas in the sealed space WS. That is, the ratio between the temperature change amount per unit time of the gas in the sealed space WS and the differential pressure change amount per unit time caused by the change is constant. Furthermore, the temperature of the gas in the sealed space WS is considered to be close to the temperature of the workpiece W. Therefore, by regarding the workpiece temperature Tw as the temperature of the gas in the sealed space WS, the ratio between the workpiece temperature change amount per unit time and the differential pressure change amount per unit time caused thereby is substantially constant. It is believed that there is.

Therefore, in this embodiment, when the workpiece temperature change amount per unit time is δTw and the differential pressure change amount per unit time caused by the workpiece temperature change is δPb, the following equation (1) is established. δPb = k · δTw (1)
In the above formula (1), k is a proportionality constant.

In the present embodiment, the differential pressure change amount (= ΔPs) represented by the differential pressure ΔPs obtained from the differential pressure sensor 7 is equal to the differential pressure change amount caused by the change in the workpiece temperature and the sealed space WS. And the amount of differential pressure change caused by leakage. Accordingly, when the differential pressure change amount per unit time (actual differential pressure change amount) caused by the leak in the sealed space WS among the differential pressure change amounts is δPa, the following equation (2) is established.
δPs = k · δTw + δPa (2)
In the above formula (2), δPs is a differential pressure change amount per unit time obtained from the differential pressure sensor 7.

  FIG. 4 is a graph showing the relationship between the differential pressure change amount δPs and the workpiece temperature change amount δTw expressed by the above equation (2). As shown in FIG. 4, the differential pressure change amount δPs is expressed as a linear function of the workpiece temperature change amount δTw. Further, the relationship between the first differential pressure change amount δPa1 (= dPa1 / tt1) per unit time acquired in the first measurement and the first work temperature change amount δTw1 (= dTw1 / tt1) per unit time, Also, the relationship between the second differential pressure change amount δPa2 (= dPa2 / tt2) per unit time acquired in the second measurement and the second workpiece temperature change amount δTw2 (= dTw2 / tt2) per unit time is 4 is represented on a straight line represented by a linear function shown in FIG. Then, the differential pressure change amount (= δPa) represented by the size of the intercept of the graph shown in FIG. 4 represents the differential pressure change amount per unit time when the workpiece temperature change amount is zero. It is considered that the differential pressure change amount when the work temperature change amount is 0 is the differential pressure change amount caused by the leakage of the sealed space WS. Therefore, by obtaining the intercept of the graph of FIG. 4, it is possible to accurately calculate the differential pressure change amount (actual differential pressure change amount) per unit time caused by the leak in the sealed space WS.

The first differential pressure change amount δPa1 (= dPa1 / tt1) per unit time and the first change per unit time obtained in the first measurement are added to the differential pressure change amount δPs and the workpiece temperature change amount δTw in Expression (2). Substituting one workpiece temperature change amount δTw1 (= dTw1 / tt1), the following equation (3) is obtained. Further, the second differential pressure change amount δPa2 (= dPa2 / tt2) per unit time and the unit time obtained in the second measurement are added to the differential pressure change amount δPs and the workpiece temperature change amount δTw in Expression (2). Substituting the second workpiece temperature change amount δTw2 (= dTw2 / tt2), Equation (4) is obtained.
δPa1 = k · δTw1 + δPa (3)
δPa2 = k · δTw2 + δPa (4)

Equation (5) is obtained by subtracting both sides of equation (3) by both sides of equation (4).
δPa1-δPa2 = k (δTw1-δTw2) (5)
Further, when Expression (5) is modified, Expression (6) is obtained.
k = (δPa1-δPa2) / (δTw1-δTw2) (6)

Substituting the right side of equation (6) into k in equation (4) and rearranging results in equation (7).
δPa = δPa2- (δPa1-δPa2) / (δTw1-δTw2) · δTw2
(7)

Rewriting δPa1 in equation (7) to dPa1 / tt1, δTw1 to dTw1 / tt1, δPa2 to dPa2 / tt2, and δTw2 to dTw2 / tt2, respectively, equation (8) is obtained.
δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) / (dTw1 / tt1-dTw2 / tt2). (dTw2 / tt2) (8)
The above equation (8) agrees with the equation used when calculating the actual differential pressure change amount δPa in S24. Further, the equation (8) is obtained by calculating the actual differential pressure change amount δPa based on the first differential pressure change amount dPa1, the first work temperature change amount dTw1, the second differential pressure change amount dPa2, and the second work temperature change amount dTw2. It is configured to calculate. That is, the process and step of S24 are performed based on the first differential pressure change amount dPa1, the first work temperature change amount dTw1, the second differential pressure change amount dPa2, and the second work temperature change amount dTw2. Change in the differential pressure between the pressure in the comparison space CS and the time difference in the differential pressure due to leakage in the sealed space WS (specifically, the change in time per unit time) This is an actual differential pressure change amount calculation process for calculating the amount δPa, and an actual differential pressure change amount calculation step.

  As described above, in the present embodiment, the sealed space WS is included in the differential pressure change amount that is the time change amount of the differential pressure between the pressure in the sealed space WS and the pressure in the comparison space CS based on the above equation (8). By excluding the amount of change in the differential pressure caused by the temperature change of the gas inside, the amount of change in the differential pressure caused by the leak in the sealed space WS can be calculated more accurately than in the past.

  Further, the right side of the above equation (8) includes the workpiece temperature change amount acquired in two different periods. The amount of change in the work temperature varies depending on the temperature change in the surrounding environment of the work W and other external environment changes. That is, the temperature change amount of the work reflects the temperature change of the environment around the work W and other changes of the external environment. Therefore, when the actual differential pressure change amount δPa is calculated by the above equation (8), the calculated actual differential pressure change amount δPa is also taken into consideration of the temperature change in the environment surrounding the workpiece W and other external environment changes. Will be. That is, in the present embodiment, even when a temperature change in the surrounding environment of the work and other changes in the external environment occur, the actual differential pressure change amount δPa, that is, the sealed space WS of the work W is more accurately determined. The amount of change in differential pressure caused by the leak can be calculated.

  Further, the above equation (8) does not hold only when a specific condition is satisfied, but generally holds. Therefore, the calculation method of the differential pressure change amount described in the present embodiment is highly versatile, and even under various conditions, it is caused by the leakage of the sealed space WS using the equation (8) more accurately than in the past. Thus, it is possible to calculate the amount of change in differential pressure.

  Further, according to this embodiment, the control device 10 determines whether there is a leak in the sealed space WS of the workpiece W based on the actual differential pressure change amount δPa calculated in S24 (S25, S26, By executing S27), it is possible to accurately determine whether or not there is a leak in the sealed space WS of the workpiece W.

  Moreover, according to this embodiment, the control apparatus 10 is the 1st on-off valve 5a after execution of a 1st state acquisition process (S12, S13) and before execution of a 2nd state acquisition process (S22, S23). With the valve closed, the second on-off valve 5b is opened for a predetermined time to execute an equilibration process (S15) for communicating the sealed space WS and the comparison space CS. By this equilibration process (equilibrium process), the differential pressure ΔPs is returned to 0 before the second differential pressure measurement. For this reason, even when a differential pressure sensor with a small measurement width is used, it is possible to measure the differential pressure ΔPs twice.

  Furthermore, according to this embodiment, when adjusting the pressure of the sealed space WS and the comparison space CS, the sealed space and the comparison space are set so that the pressure in the sealed space and the comparison space becomes the first pressure (P1) higher than the test pressure. Pressurization processing (S1, S2) for pressurizing the comparison space, and decompression processing (S4) for depressurizing the sealed space and the comparison space so that the pressure of the sealed space and the comparison space becomes the test pressure after the pressurization processing is performed. Executed. According to this, the gas in the sealed space WS can be rapidly cooled by adiabatic expansion by the decompression process. For this reason, the heat radiation of the gas in the sealed space WS to the workpiece W can be promoted, whereby the gas temperature Ta in the sealed space WS and the workpiece temperature Tw can be brought close to each other. Therefore, the temperature change amount of the gas in the sealed space WS can be brought close to the workpiece temperature change amount, and as a result, the calculation accuracy of the actual differential pressure change amount dPa calculated using the workpiece temperature change amount can be improved. it can. In addition, by rapidly cooling by adiabatic expansion, the equilibrium time for bringing the temperature of the workpiece W close to the temperature of the gas in the sealed space WS can be shortened. Therefore, the inspection time can be shortened.

  Furthermore, according to the present embodiment, when the first differential pressure change amount dPa1 obtained during the first measurement of the differential pressure ΔPs is large, specifically, the first differential pressure change amount dPa1 is greater than the maximum differential pressure change amount dPmax. Is larger, a large leak determination is made and the subsequent inspection is omitted. For this reason, it is not necessary to measure the differential pressure ΔPs twice for a workpiece in which such a large leak occurs. Therefore, the inspection time can be shortened.

  As mentioned above, although embodiment of this invention was described, this invention should not be limited to the said embodiment. For example, in the above embodiment, the first on-off valve 5a is closed after the processing of S12 and S13 (first state acquisition processing) and before the processing of S22 and 23 (second state acquisition processing). Equilibrium processing is performed in which the second on-off valve 5b is opened with the valve kept open, but the first on-off valve 5a and the second on-off valve 5b are closed by using a differential pressure sensor having a large measurement width. The first state acquisition process and the second state acquisition process may be executed continuously. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Leak inspection apparatus (differential pressure change amount calculation apparatus), 2 ... Pressure source, 3 ... Pressure regulator, 4a ... 1st piping, 4b ... 2nd piping, 4c ... 3rd piping, 5a ... 1st on-off valve, 5b ... second on-off valve, 5c ... third on-off valve, 6 ... master work, 7 ... differential pressure sensor, 9a ... work temperature sensor, 9b ... pressure sensor, 10 ... control device (control unit), δPa ... actual differential pressure Change amount, dPa1 ... first differential pressure change amount, dPa2 ... second differential pressure change amount, dPmax ... maximum differential pressure change amount, δPth ... threshold differential pressure change amount, dTw1 ... first work temperature change amount, dTw2 ... second Work temperature change amount, P1 ... first pressure, Pt ... test pressure, tt1 ... first inspection time (first period), tt2 ... second inspection time (second period), W ... work, WS ... sealed space, CS ... Comparison space, ΔPs ... Differential pressure

Claims (10)

A first pipe having one end connected to a pressure source and the other end connected to a sealed space formed in the workpiece;
A first on-off valve interposed in the first pipe;
A second pipe having one end disposed downstream of the first on-off valve and communicating with the sealed space and the other end communicating with a comparison space formed in the master work;
A second on-off valve interposed in the second pipe;
A differential pressure sensor for detecting a differential pressure between the pressure in the sealed space and the pressure in the comparison space;
A workpiece temperature sensor for detecting the temperature of the workpiece;
A controller that calculates a time change amount of a differential pressure between the pressure of the sealed space and the pressure of the comparison space by controlling the opening / closing operation of the first opening / closing valve and the opening / closing operation of the second opening / closing valve; Prepared,
The control unit is
The first on-off valve and the second on-off valve are opened to connect the pressure source, the sealed space, and the comparison space, and a predetermined test pressure is applied from the pressure source to the sealed space and the comparison space. A pressure adjustment process for adjusting the pressure of the sealed space and the pressure of the comparison space to be applied; and
After execution of the pressure adjustment process, the first on-off valve is closed to shut off the communication between the pressure source and the sealed space and the communication between the pressure source and the comparison space, and the second on-off valve is closed. A valve closing process for blocking communication between the sealed space and the comparison space;
A differential pressure detected by the differential pressure sensor is a first differential pressure that is an amount that has changed during a first period in which the first on-off valve and the second on-off valve are closed by executing the valve closing process. A first state acquisition process for acquiring a first work temperature change amount, which is an amount of change and a temperature at which the work temperature detected by the work temperature sensor has changed within the first period;
The differential pressure detected by the differential pressure sensor is a period during which the first on-off valve and the second on-off valve are closed, and is an amount changed within a second period after the first period. A second state acquisition process for acquiring a second differential pressure change amount and a second workpiece temperature change amount that is an amount by which the temperature of the workpiece detected by the workpiece temperature sensor has changed within the second period;
Based on the first differential pressure variation, the first workpiece temperature variation, the second differential pressure variation, and the second workpiece temperature variation, the difference between the pressure in the sealed space and the pressure in the comparison space An actual differential pressure change amount calculation process for calculating an actual differential pressure change amount that is a time change amount of the pressure and is a time change amount of the differential pressure caused by a leak in the sealed space;
The differential pressure change amount calculation device that executes In the differential pressure change amount calculation device according to claim 1,
The first differential pressure change amount is dPa1, the first work temperature change amount is dTw1, the first period is tt1, the second differential pressure change amount is dPa2, the second work temperature change amount is dTw2, and the second work temperature change amount is dTw2. When the period is tt2 and the actual differential pressure change amount is δPa, the control unit performs the following equation δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) in the actual differential pressure change amount calculation process. /(DTw1/tt1-dTw2/tt2).(dTw2/tt2)
A differential pressure change amount calculation device that calculates the actual differential pressure change amount δPa by In the differential pressure change amount calculation device according to claim 1 or 2,
The control unit executes a leak determination process for determining whether or not there is a leak in the sealed space of the workpiece based on the actual differential pressure change amount.
Differential pressure variation calculation device. The differential pressure change amount calculating device according to any one of claims 1 to 3,
The controller is
After the execution of the first state acquisition process and before the execution of the second state acquisition process, the second on-off valve is opened for a predetermined time while the first on-off valve is closed, and the sealed space A differential pressure change amount calculation device that executes an equilibrium process for communicating with the comparison space. In the differential pressure change amount calculation device according to any one of claims 1 to 4,
The pressure adjustment process is:
A pressurizing process for pressurizing the sealed space and the comparison space such that the pressure of the sealed space and the comparison space becomes a first pressure higher than the test pressure;
Depressurization processing for depressurizing the sealed space and the comparison space so that the pressure of the sealed space and the comparison space becomes the test pressure after the pressurization processing is performed;
A differential pressure change amount calculation device. The sealed space formed in the work and the comparison space formed in the master work are communicated with a pressure source so that the pressure in the sealed space and the pressure in the comparison space become the same test pressure. A pressure adjustment step of adjusting the pressure of the comparison space and the pressure of the comparison space;
A blocking step of blocking communication between the pressure source and the sealed space and communication between the pressure source and the comparison space;
The first period in which the pressure difference between the pressure in the sealed space and the pressure in the comparison space is blocked by the blocking step between the communication between the pressure source and the sealed space and the communication between the pressure source and the comparison space. A first state acquisition step of acquiring a first differential pressure change amount that is an amount that has changed inward, and a first work temperature change amount that is an amount in which the temperature of the work has changed within the first period;
The pressure difference between the pressure in the sealed space and the pressure in the comparison space is a period in which the communication between the pressure source and the sealed space and the communication between the pressure source and the comparison space are blocked. A second differential pressure change amount that is an amount that has changed within a second period after the period, and a second workpiece temperature change amount that is an amount at which the temperature of the workpiece has changed within the second period. A two-state acquisition process;
Based on the first differential pressure variation, the first workpiece temperature variation, the second differential pressure variation, and the second workpiece temperature variation, the difference between the pressure in the sealed space and the pressure in the comparison space An actual differential pressure change amount calculating step for calculating an actual differential pressure change amount that is a time change amount of the pressure and is a time change amount of the differential pressure caused by a leak in the sealed space;
A differential pressure change amount calculation method. In the differential pressure change amount calculation method according to claim 6,
In the actual differential pressure change amount calculating step, the first differential pressure change amount is dPa1, the first workpiece temperature change amount is dTw1, the first period is tt1, the second differential pressure change amount is dPa2, and the second differential pressure change amount is dPa2. When the workpiece temperature change amount is dTw2, the second period is tt2, and the actual differential pressure change amount is δPa, the following equation δPa = dPa2 / tt2- (dPa1 / tt1-dPa2 / tt2) / (dTw1 / tt1- dTw2 / tt2). (dTw2 / tt2)
The differential pressure change amount calculation method, which is a step of calculating the actual differential pressure change amount δPa. In the differential pressure change amount calculation method according to claim 6 or 7,
A differential pressure change amount calculation method including a leak determination step of determining whether or not there is a leak in the sealed space of the workpiece based on the actual differential pressure change amount. In the differential pressure change amount calculation method according to any one of claims 6 to 8,
An equilibration step that is performed after the first state acquisition step and before the second state acquisition step, and makes the pressure in the sealed space coincide with the pressure in the comparison space by communicating the sealed space and the comparison space. A differential pressure change amount calculation method. In the differential pressure change amount calculation method according to any one of claims 6 to 9,
The pressure adjusting step includes
Applying a first pressure higher than the test pressure from the pressure source to the sealed space and the comparison space; and
A pressure reducing step for reducing the pressure of the sealed space and the comparison space so that the pressure of the sealed space and the comparison space becomes the test pressure;
A differential pressure change amount calculation method.

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