Abstract:
A leak inspection device for inspecting leaks from a work by sealing a gas inside the work or sucking the gas therefrom includes: a depressurizing device that reduces the pressure of the gas inside the work; a pressurizing device that pressurizes the gas inside the work; a temperature sensor that detects the temperature of the work; a pressure sensor that detects the pressure of the gas inside the work; and a controller. The controller calculates the saturation vapor pressure at the same temperature as the temperature of the work, controls the depressurizing device to thereby reduce the pressure of the gas inside the work to the saturation vapor pressure, sucks the water vapor that has vaporized inside the work, controls the pressurizing device to thereby seal the gas inside the work and pressurize the gas inside the work until the temperature of the work detected by the temperature sensor reaches a predetermined temperature.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a leak inspection device and a leak inspection method. 
       BACKGROUND ART 
       [0002]    It is conventionally known that gas is enclosed in a work to be inspected to inspect the leak from the work. For example, in the automobile factory, the leak inspections are operated to various manufactures such as an engine cylinder block. 
         [0003]    JP S60-111249 U discloses the leak inspection method that includes pressurizing the master chamber and the work at the same time, and detecting the differential pressure between the master chamber and the work. The internal pressure of the work is influenced by the temperature variation of the work and environment thereof or by the water remained inside the work. JP S60-111249 U may fail to deal with these disturbances, so that it is difficult to put into practice. 
         [0004]    JP 2007-218745 A discloses the leak inspection method adjusting the amount of the water remained in the work by means of a heat source. Heating up the work to completely vaporize the water remained in the work requires huge amount of heat. Such heat source may be too large to be useful in the mass-produce lines. It may take long time to cool down the heated-up work to be handled without considering the heat exchange with surroundings. It is also difficult to employ such long time cooling section in the mass-produce lines. 
         [0005]    JP 2006-275906 A discloses the leak inspection method detecting the leak amount momentarily by measuring the change of the pressure by pressure sensor with a special pressurizing/depressurizing cycle. JP 2006-275906 A cannot be applicable to the work with large capacity such as the cylinder block. The water remained in the work, which is one of the disturbances, is not considered, so that it is difficult to put into practice. 
         [0006]    As described above, conventional leak inspection methods may fail to deal with the disturbances including the temperature variation of the work or the water remained in the work. Therefore, the reliable leak inspection has not been obtained. 
       Citation List 
     Patent Literature 
       [0007]    PTL 1: JP S60-111249 U 
         [0008]    PTL 2: JP 2007-218745 A 
         [0009]    PTL 3: JP 2006-275906 A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    The objective of the present invention is to provide a technique of removing the disturbances on the leak inspection such as the temperature variation and the water remained in the work. 
       Technical Solutions 
       [0011]    The first embodiment of the present invention is a leak inspection device for inspecting a leak from a work, which includes: a depressurizing device for depressurizing a gas in the work; a pressurizing device for pressurizing the gas in the work; a temperature sensor for measuring the temperature of the work; a pressure sensor for measuring the internal pressure of the work; and a controller for controlling the pressure of the gas in the work by means of the depressurizing device and the pressurizing device. The controller calculates a saturation vapor pressure at the work temperature measured by the temperature sensor, the depressurizing device evacuates the gas in the work until the internal pressure of the work reaches the saturation vapor pressure and sucks the vaporized water, and the pressurizing device pressurizes the gas in the work until the temperature of the work reaches a predetermined temperature. 
         [0012]    The second embodiment of the present invention is a leak inspection method for inspecting a leak from a work, which includes: depressurizing process for depressurizing a gas in the work until the internal pressure of the work reaches a saturation vapor pressure at the work temperature and sucking the vaporized water; and pressurizing process for pressurizing the gas in the work until the temperature of the work reaches a predetermined temperature. 
       Advantageous Effects of Invention 
       [0013]    According to the present invention, the disturbances on the leak inspection can be removed such as the temperature variation and the water remained in the work. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a block diagram depicting a leak inspection device as a first embodiment. 
           [0015]      FIG. 2  is a flowchart of the leak inspection. 
           [0016]      FIG. 3  is a table showing a valve sequencing control in the leak inspection. 
           [0017]      FIG. 4  is a block diagram depicting a leak inspection device as a second embodiment. 
           [0018]      FIG. 5  is a table showing a valve sequencing control in the leak inspection. 
           [0019]      FIG. 6  is a block diagram depicting a leak inspection device as a third embodiment. 
           [0020]      FIG. 7  is a table showing a valve sequencing control in the leak inspection. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0021]    Referring to attached drawings, the embodiments of the present invention are described below. 
         [0022]    In  FIGS. 1 ,  4  and  6 , solid lines represent air pipes of a leak inspection device, broken lines represent air pipes for controlling valves, and two-dot chain lines represent electrical signals. 
         [0023]    In  FIGS. 3 ,  5  and  7 , switching of each valve is shown in each sequence, and hatched areas show “ON” of the valves. 
         [0024]      FIG. 1  depicts a leak inspection device  10  as a first embodiment. 
         [0025]    The leak inspection device  10  is disposed in an inspection apparatus in an automobile factory. The inspection device  10  includes: sealing a gas inside an engine cylinder block (work W); and removing water remained in the work W and preventing temperature variation of the work W, in which the water remained in the work and the variation in temperature of the work cause disturbances on the inspection. In the embodiment, the gas to be enclosed is a dry air. 
         [0026]    The inspection device  10  includes a depressurizing device  11 , a pressurizing device  12  and a vacuum tank  21 . These components  11 ,  12  and  21  are connected via air pipes and configure an air pressure circuit Al. 
         [0027]    The depressurizing device  11  is a vacuum pump, which is capable of evacuating the air in the circuit Al to create vacuum. The pressurizing device  12  is an air compressor, which pressurizes the circuit Al. The vacuum tank  21  has larger capacity than the work W to be inspected by the inspection device  10 , and the depressurizing device  11  evacuates the tank. 
         [0028]    The inspection device  10  includes valves VL 0  to VL 8  and mufflers MU 1  and MU 2 . These valves VL 0  to VL 8  and mufflers MU 1  and MU 2  are connected through air pipes and configure the air pressure circuit A 1 . The valves VL 0  to VL 8  are two-position spring-return valves and actuated by air pressure in a control circuit  60  as a pilot. The mufflers MU 1  and MU 2  are communicated with air and capable of opening the circuit A 1  and of introducing air into the circuit A 1 . 
         [0029]    The inspection device  10  includes a controller  50 , the air pressure control circuit  60 , a pressure sensor  51  and a temperature sensor  52 . The control circuit  60 , the pressure sensor  51  and the temperature sensor  52  are connected to the controller  50 . 
         [0030]    The controller  50  controls the internal pressure Pi of the work W by using the depressurizing device  11  and the pressurizing device  12 . The controller  50  is electrically connected to these devices  11  and  12 , and transmits the control signal to control them. 
         [0031]    The pressure sensor  51  is disposed in the air pipe near the work W to measure the internal pressure Pi of the work W. The temperature sensor  52  is disposed in the work W to measure the temperature To of the work W. In the embodiment, the temperature sensor  52  is located on the wall of the cylinder. These sensors  51  and  52  transmit the measured values (pressure Pi and temperature To) to the controller  50 . 
         [0032]    Referring to  FIGS. 2 and 3 , the leak inspection as a first embodiment is described. 
         [0033]    The leak inspection control includes eliminating the disturbances such as residual water inside the work W and changes in temperature of the work W by enclosing gas into the work W before starting the leak inspection. 
         [0034]      FIG. 2  depicts an actuator control by the controller  50  for removing the disturbances.  FIG. 3  shows valve sequencing of the air pressure circuit Al with the controller  50  during the leak inspection in which the gas is sealed inside the work W. 
         [0035]    The controller  50  calculates a saturation vapor pressure Ps in STEP S 100 . The saturation vapor pressure Ps is calculated assuming that the water temperature T is same as the temperature To of the work W (T=To). The saturation vapor pressure Ps is calculated on the basis of the temperature To measured by the temperature sensor  52  by using the saturation vapor pressure curve stored in the controller  50  in advance. 
         [0036]    The controller  50  transmits the control signal to the depressurizing device  11  to vacuum the internal pressure Pi in STEP S  110 . 
         [0037]    The controller  50  compares the internal pressure Pi detected by the pressure sensor  51  with the saturation vapor pressure Ps in STEP S  120 . In STEP S 120 , if the internal pressure Pi is not smaller than the saturation vapor pressure Ps, depressurizing the internal pressure Pi is continued. 
         [0038]    In STEP S 120 , if the internal pressure Pi is smaller than (reaches) the saturation vapor pressure Ps, the remained water inside the work W is evaporated. 
         [0039]    In STEP S 130 , the controller  50  transmits the control signal to the depressurizing device  11  to vacuum the water vapor. 
         [0040]    The controller  50  transmits the control signal to the pressurizing device  12  to pressurize the internal pressure Pi of the work W in STEP S 140 . The temperature of the gas in the work W is increased by adiabatic compression, whereby the work temperature To is increased according to the rise of internal gas temperature. The controller  50  compares the work temperature To with a predetermined temperature T 1  in STEP S 150 . The predetermined temperature T 1  is a temperature being slight higher than the air temperature, which is stored in the controller  50  in advance. 
         [0041]    In STEP S 150 , if the temperature To is not higher than the predetermined temperature T 1 , the pressurizing of internal pressure Pi is continued. In STEP S 150 , if the temperature To is higher than (reaches) the predetermined temperature T 1 , the control of removing the disturbance is finished. 
         [0042]    After that, the gas is sealed in the work W, and the leak inspection for inspecting the leak from the work W is started. 
         [0043]    Referring to  FIG. 3 , the valve sequencing control in the air pressure circuit Al with the controller  50  is described below. 
         [0044]    In the sequence SE 1  as a depressurizing process, the controller  50  turns on the valves VL 0  and VL 1  (valves VL 2  to VL 8  are off) to communicate the depressurizing device  11  with the vacuum tank  21 , starting the evacuation of the vacuum tank  21 . The control  50  controls the valves VL 0  to VL 8  via the air pressure control circuit  60 . 
         [0045]    After the depressurization of the vacuum tank  21 , in the sequence SE 2 , the controller  50  turns off the valves VL 0  and VL 1 , and turns on the valve VL 5 . Thereby, the vacuum tank  21  is communicated with the work W, starting depressurization of the work W by the negative pressure of the vacuum tank  21 . The controller  50  detects that the internal pressure Pi of the work W become lower than the saturation vapor pressure Ps (corresponding to STEP S 120 ), moved to the sequence SE 3  from the sequence SE 2 . 
         [0046]    In the sequence SE 3 , the controller  50  turns off the valve VL 5 , and turns on the valves VL 3  and VL 6 . Thus, the pressurizing device  12 , the vacuum tank  21  and the muffler MU 2  are communicated with each other, and the tank  21  is purged. 
         [0047]    In the sequence SE 4  as a pressurizing process, the controller  50  turns off the valves VL 3  and VL 6 , and turns on the valves VL 4 , VL 7  and VL 8 . Thus, the pressurizing device  12  is communicated with the work W, starting the pressurization of the work W. The work W is heated up by pressurization. 
         [0048]    The controller  50  detects that the work temperature To is higher than the predetermined temperature Ti (corresponding to STEP S 150 ), moved to the sequence SE 5  from the sequence SE 4 . In the sequence SE 5 , the controller  50  turns off the valves VL 4  and VL 7 , and turns on the valves VL 1 , VL 2 , VL 5  and VL 6 , maintaining the valve VL 8  on. Thus, the vacuum tank  21  is communicated with the muffler MU 1 , thereby opening the work W to the atmosphere. 
         [0049]    Due to the above-described structure, before starting the leak inspection, the water remained in the work W is sucked as water vapor so that the water is completely removed from the inside of the work W. Also, before the inspection, the temperature of the work W is increased to the predetermined temperature T 1 , so that the work W can be insulated from the temperature of surroundings. As the result, the leak inspection can be performed without being affected by the environment of the work W or by the temperature variation of the work W. 
         [0050]    Consequently, the embodiment provides the leak inspection capable of reliably detecting the leak by means of eliminating the disturbances for the leak inspection, before the leak inspection, such as the temperature variation of the work W or the water remained in the work W. 
         [0051]      FIG. 4  depicts a leak inspection device  20  as a second embodiment. The leak inspection device  20  is added by the configuration, for a positive air leak test that inspects the leak from the work W into which the gas is enclosed, to the leak inspection device  10  as the first embodiment. 
         [0052]    Hereinafter, the same numerals as the first embodiment represent the same structures. The valves VL 6  to VL 9  in the second embodiment correspond to the valves VL 5  to VL 8  in the first embodiment, respectively. The valves VL 10  to VL 12  are added in order to inspect the leak from the work W, i.e., the positive air leak test. 
         [0053]    The leak inspection device  20  includes the depressurizing device  11 , the pressurizing device  12 , a second pressurizing device  13 , the vacuum tank  21  and a master chamber M. These components  11 ,  12 ,  13 ,  21  and M are connected via air pipes, and configure the second air pressure circuit A 2 . The master chamber M has the same capacity as the work W and is a completely sealed chamber. 
         [0054]    The inspection device  20  includes the valves VL 0  to VL 12 , the mufflers MU 1 , MU 2  and MU 3 . These valves VL 0  to VL 12  and mufflers MU 1 , MU 2  and MU 3  are connected through air pipes and configure the air pressure circuit A 2 . 
         [0055]    The inspection device  20  includes the controller  50 , the air pressure control circuit  60 , the pressure sensor  51 , the temperature sensor  52  and a differential pressure sensor  53 . The control circuit  60 , the pressure sensor  51 , the temperature sensor  52  and the differential pressure sensor  53  are connected to the controller  50 . The differential pressure sensor  53  is disposed in the air pressure circuit A 2 , and detects the difference between the pressure of the work W and that of the master chamber M. 
         [0056]    Referring to  FIG. 5 , the leak inspection as a second embodiment is described. 
         [0057]      FIG. 5  shows valve sequencing of the air pressure circuit A 2  with the controller  50 , in which the actuator control (disturbance Control) by the controller  50  is the same as the first embodiment. 
         [0058]    In the second embodiment, the sequences SE 1  to SE 4  are the same as the first embodiment. The control  50  controls the valves VL 0  to VL 12  via the air pressure control circuit  60 . 
         [0059]    In the sequence SES, the controller  50  keeps the valves VL 4 , VL 8  and VL 9  on, which are turned on in the sequence SE 4 , and turns on the valves VL 5  and VL 11 . The pressurizing device  13 , the master chamber M and the work W are communicated with each other, and the pressurizing device  13  pressurizes the master chamber M and the work W. 
         [0060]    In the sequence SE 6 , the controller  50  keeps the valves VL 4 , VL 8 , VL 9  and VL 11  on, and turns off the valve VL 5 . The pressurizing device  13  is insulated from the master chamber M and the work W, thereby making the master chamber M and the work W equal pressure. 
         [0061]    In the sequence SE 7 , the controller  50  keeps the valves VL 4 , VL 8 , VL 9  and VL 11  on, and turns on the valve VL 10 . Thus, the master chamber M is isolated from the work W, and the master chamber M and the work W are separately stable. 
         [0062]    In the sequence SE 8  after sequence SE 7 , the valve sequencing is maintained since the sequence SE 7 , the controller  50  detects the differential pressure Pd between the master chamber M and the work W that is measured with the differential pressure sensor  53 . If the differential pressure Pd is smaller than the predetermined pressure P 1 , the leak inspection for the work W is clear. 
         [0063]    In the sequence SE 9 , the controller  50  maintains the valves VL 9  and VL 11  on, and turns on the valves VL 1 , VL 2 , VL 6 , VL 7  and VL 12 . Thereby, the muffler MU 3  is communicated with the master chamber M and the work W. The master chamber M and the work W are open to air, so that the remained pressure is released. 
         [0064]    Due to the above-described structure, before starting the leak inspection, the water remained in the work W is sucked as water vapor so that the water is completely removed from the inside of the work W. Also, before the inspection, the temperature of the work W is increased to the predetermined temperature T 1 , so that the work W can be insulated from the temperature of surroundings. As the result, the leak inspection can be performed without being affected by the environment of the work W or by the temperature variation of the work W. 
         [0065]    Consequently, the embodiment provides the leak inspection capable of reliably detecting the leak by means of removing the disturbances for the leak inspection, before the leak inspection, such as the temperature variation of the work W or the water remained in the work W. Moreover, the leak inspection is determined by the differential pressure Pd between the work W and the master chamber M, and therefore the minute leak can be detected. 
         [0066]      FIG. 6  depicts a leak inspection device  30  as a third embodiment. 
         [0067]    The leak inspection device  30  is added by the configuration, for a negative air leak test that inspects the leak from the work W into which the gas is enclosed, to the leak inspection device  10  as the first embodiment. Hereinafter, the same numerals as the first embodiment or the second embodiment represent the same structures. 
         [0068]    The valves VL 2  to VL 5  in the third embodiment correspond to the valves VL 1  to VL 4  in the first embodiment, and the valves VL 7  to VL 10  in the third embodiment corresponding to the valves VL 5  to VL 8  in the first embodiment. The valves VL 1 , VL 6  and VL 11  to VL 13  are added in order to inspect the leak from the work W, i.e., the negative air leak test. The vacuum tank  22  in the third embodiment corresponds to the vacuum tank  21  in the first embodiment, and the vacuum tank  21  is added in the third embodiment. 
         [0069]    The leak inspection device  30  includes the depressurizing device  11 , the pressurizing device  12 , the vacuum tanks  21 ,  22  and the master chamber M. These components  11 ,  12 ,  21 ,  22  and M are connected via air pipes, and configure the third air pressure circuit A 3 . 
         [0070]    The inspection device  30  includes the valves VL 0  to VL 13 , the mufflers Min, MU 2  and MU 3 . These valves VL 0  to VL 13  and mufflers MU 1 , MU 2  and MU 3  are connected through air pipes and configure the air pressure circuit A 3 . 
         [0071]    The inspection device  30  includes the controller  50 , the air pressure control circuit  60 , the pressure sensor  51 , the temperature sensor  52  and the differential pressure sensor  53 . The control circuit  60 , the pressure sensor  51 , the temperature sensor  52  and the differential pressure sensor  53  are connected to the controller  50 . 
         [0072]    Referring to  FIG. 7 , the leak inspection as a third embodiment is described.  FIG. 7  shows valve sequencing of the air pressure circuit A 3  with the controller  50 , in which the actuator control (disturbance control) by the controller  50  is the same as the first embodiment. 
         [0073]    The control  50  controls the valves VL 0  to VL 13  via the air pressure control circuit  60 . In the sequence SE 1  as the depressurization, the valves VL 0 , VL 1 , and VL 2  are turned on (valves VL 3  to VL 13  are off). The depressurizing device  11  is communicated with the vacuum tanks  21  and  22 , and the vacuum tanks  21  and  22  are evacuated. The sequences SE 2  to SE 4  in the third embodiment are the same as the sequences SE 2  to SE 4  in the first embodiment. 
         [0074]    In the sequence SES, the controller  50  keeps the valves VL 5 , VL 9  and VL 10  on, which are turned on in the sequence SE 4 , and turns on the valves VL 6  and VL 12 . The vacuum tank  21 , the master chamber M and the work W are communicated with each other, and the master chamber M and the work W are depressurized. 
         [0075]    In the sequence SE 6 , the controller  50  keeps the valves VL 5 , VL 9 , VL 10  and VL 12  on, and turns off the valve VL 6 . The vacuum tank  21  is isolated from the master chamber M and the work W, thereby making the master chamber M and the work W equal pressure. 
         [0076]    In the sequence SE 7 , the controller  50  keeps the valves VL 5 , VL 9 , VL 10  and VL 12  on, and turns on the valve VL 11 . Thus, the master chamber M is isolated from the work W, and the master chamber M and the work W are separately made stable. 
         [0077]    In the sequence SE 8  after the sequence SE 7 , the valve sequencing is maintained since the sequence SE 7 , the controller  50  detects the differential pressure Pd between the master chamber M and the work W that is measured with the differential pressure sensor  53 . If the differential pressure Pd is smaller than the predetermined pressure P 1 , the leak inspection for the work W is clear. 
         [0078]    In the sequence SE 9 , the controller  50  maintains the valves VL 10  and VL 12  on, and turns on the valves VL 1 , VL 2 , VL 3 , VL 6 , VL 7 , VL 8  and VL 13 . Thereby, the mufflers MU 1  and MU 3  are communicated with the vacuum tank  21 , the master chamber M and the work W. The master chamber M and the work W are open to air so that the remained pressure is released. 
         [0079]    Due to the above-described structure, before starting the leak inspection, the water remained in the work W is sucked as water vapor so that the water is completely removed from the inside of the work W. Also, before the inspection, the temperature of the work W is increased to the predetermined temperature Ti, so that the work W can be insulated from the temperature of surroundings. As the result, the leak inspection can be performed without being affected by the environment of the work W or by the temperature variation of the work W. 
         [0080]    Consequently, the embodiment provides the leak inspection capable of reliably detecting the leak by means of removing the disturbances for the leak inspection, before the leak inspection, such as the temperature variation of the work W or the water remained in the work W. Moreover, the leak inspection is determined by the differential pressure Pd between the work W and the master chamber M, and therefore the minute leak can be detected. 
       DESCRIPTION OF NUMERALS 
       [0081]      10 : leak inspection device (first embodiment),  20 : leak inspection device (second embodiment),  30 : leak inspection device (third embodiment),  11 : depressurizing device,  12 : pressurizing device,  13 : pressurizing device,  50 : controller,  51 : pressure sensor,  52 : temperature sensor,  53 : differential sensor