1. A control apparatus for an engine that introduces purge gas containing fuel gas evaporated from a fuel tank into an intake system, comprising:
an air-fuel ratio calculation unit that calculates an air-fuel ratio (AF) of the engine;
a purge rate calculation unit that calculates a purge rate (RPRG) corresponding to an introduction rate of the purge gas;
a concentration calculation unit that calculates a concentration (KAF\u2014PRG) of the purge gas based on the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and the purge rate (RPRG) calculated by the purge rate calculation unit; and
a decision unit that permits or inhibits the concentration calculation unit (4) to calculate the concentration (KAF\u2014PRG) based on the purge rate (RPRG) calculated by the purge rate calculation unit.
2. The control apparatus according to claim 1, wherein
the decision unit allows the concentration calculation unit to update a calculation value of the concentration (KAF\u2014PRG) to the latest value when the purge rate (RPRG) is equal to or higher than a criterion rate (RTH); and
the decision unit makes the concentration calculation unit maintain the last value of the concentration (KAF\u2014PRG) when the purge rate (RPRG) is lower than the criterion rate (RTH).
3. The control apparatus according to claim 1, further comprising:
an air amount calculation unit that calculates an air amount (EC) to be introduced into a cylinder of the engine; and
an inhibition period calculation unit that calculates a period for which the calculation of the concentration (KAF\u2014PRG) by the concentration calculation unit is inhibited based on a history of the air amount (EC) calculated by the air amount calculation unit.
4. The control apparatus according to claim 2, further comprising:
an air amount calculation unit that calculates an air amount (EC) to be introduced into a cylinder of the engine; and
an inhibition period calculation unit that calculates a period for which the calculation of the concentration (KAF\u2014PRG) by the concentration calculation unit is inhibited based on a history of the air amount (EC) calculated by the air amount calculation unit.
5. The control apparatus according to claim 1, wherein
the decision unit permits or inhibits the calculation of the concentration (KAF\u2014PRG) to the concentration calculation unit based on a fuel amount correction coefficient (KFB\u2014PRG) correlative to a difference between the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and a target air-fuel ratio.
6. The control apparatus according to claim 2, wherein
the decision unit permits or inhibits the calculation of the concentration (KAF\u2014PRG) to the concentration calculation unit based on a fuel amount correction coefficient (KFB\u2014PRG) correlative to a difference between the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and a target air-fuel ratio.
7. The control apparatus according to claim 3, wherein
the decision unit permits or inhibits the calculation of the concentration (KAF\u2014PRG) to the concentration calculation unit based on a fuel amount correction coefficient (KFB\u2014PRG) correlative to a difference between the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and a target air-fuel ratio.
8. The control apparatus according to claim 4, wherein
the decision unit permits or inhibits the calculation of the concentration (KAF\u2014PRG) to the concentration calculation unit based on a fuel amount correction coefficient (KFB\u2014PRG) correlative to a difference between the air-fuel ratio (AF) calculated by the air-fuel ratio calculation unit and a target air-fuel ratio.
9. The control apparatus according to claim 5, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) in a driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is equal to or greater than a criterion amount, and
permits the calculation of the concentration (KAF\u2014PRG) in another driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is smaller than the criterion amount.
10. The control apparatus according to claim 6, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) in a driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is equal to or greater than a criterion amount, and
permits the calculation of the concentration (KAF\u2014PRG) in another driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is smaller than the criterion amount.
11. The control apparatus according to claim 7, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) in a driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is equal to or greater than a criterion amount, and
permits the calculation of the concentration (KAF\u2014PRG) in another driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is smaller than the criterion amount.
12. The control apparatus according to claim 8, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) in a driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is equal to or greater than a criterion amount, and
permits the calculation of the concentration (KAF\u2014PRG) in another driving state in which the variation amount of the fuel amount correction coefficient (KFB\u2014PRG) is smaller than the criterion amount.
13. The control apparatus according to claim 1, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) when the engine is accelerated or decelerated suddenly, and
permits the calculation of the concentration (KAF\u2014PRG) except a case in which the engine is accelerated or decelerated suddenly.
14. The control apparatus according to claim 1, wherein
the decision unit
inhibits the calculation of the concentration (KAF\u2014PRG) when a load acting on the engine is equal to or lower than a criterion amount, and
permits the calculation of the concentration (KAF\u2014PRG) when the load is higher than the criterion amount.
15. The control apparatus according to claim 1, wherein
the decision unit
permits the calculation of the concentration (KAF\u2014PRG) when feedback injection control is being carried out, and
inhibits the calculation of the concentration (KAF\u2014PRG) when open loop injection control is being carried out.
16. The control apparatus according to claim 1, wherein
the decision unit changes a condition for permitting or inhibiting the calculation of the concentration (KAF\u2014PRG) in response to the air-fuel ratio (AF).
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An x-ray tube, comprising:
an outer housing containing a coolant;
an evacuated enclosure disposed in the outer housing so as to be at least in partial fluid communication with the coolant, the evacuated enclosure containing an electron source and an anode positioned to receive electrons produced by the electron source;
an expansion bladder contained within the outer housing, the expansion bladder defining an interior volume;
a port defined in the outer housing and configured to provide atmospheric pressure access to the interior volume of the expansion bladder via an air passageway; and
wherein the port is positioned within a region of the outer housing that is substantially x-ray transmissive.
2. The x-ray tube as defined in claim 1, further comprising means for substantially preventing coolant contained within the housing from escaping through the port.
3. The x-ray tube as defined in claim 2, wherein the means for substantially preventing allows the transmission of air, gases, and vapors.
4. The x-ray tube as defined in claim 2, wherein the means for substantially preventing comprises a semi-permeable membrane.
5. The x-ray tube as defined in claim 4, wherein the semi-permeable membrane is included within a membrane seal plug that is received within the port defined in the outer housing.
6. The x-ray tube as defined in claim 1, wherein the air passageway is a tube extending between the interior volume of the expansion bladder and the port.
7. The remote expansion bladder venting system as defined in claim 1, wherein the coolant is continuously circulated in and out of the x-ray tube housing.
8. A remote expansion bladder venting system suitable for use in an x-ray tube, comprising:
an expansion bladder positioned within a first region of an x-ray tube housing, the first region being substantially non-transmissive to x-rays, the bladder having an exterior surface in contact with a coolant disposed within the housing;
a vent provided in a second region of the x-ray tube housing, the second region being substantially transmissive to x-rays, the vent being in communication with atmospheric pressure; and
an air passageway that interconnects an interior volume of the expansion bladder with the vent so as to enable the expansion bladder to be subject to atmospheric pressure.
9. The remote expansion bladder venting system as defined in claim 8, wherein the vent includes a semi-permeable portion such that the vent is substantially transmissive to air but substantially non-transmissive to the coolant.
10. The remote expansion bladder venting system as defined in claim 9, wherein the semi-permeable portion is comprised of a microporous, expanded PTFE membrane.
11. The remote expansion bladder venting system as defined in claim 8, wherein the air passageway is at least partially defined by a tube that extends between an opening in the expansion bladder interior and the vent.
12. The remote expansion bladder venting system as defined in claim 11, wherein the tube extends from an outlet fitting included at the opening in the expansion bladder interior to a housing fitting included in a surface of the housing in the second region.
13. The remote expansion bladder venting system as defined in claim 8, wherein the coolant is a dielectric oil.
14. An x-ray tube, comprising:
an outer housing that defines an interior volume containing a coolant;
a radiation shielding layer included on a portion of the outer housing;
an evacuated enclosure contained in the outer housing and having an outer surface in communication with the coolant, the evacuated enclosure containing an electron source and an anode positioned to receive electrons produced by the electron source; and
a remote bladder venting system, comprising:
an expansion bladder contained within the portion of the outer housing that includes the radiation shielding layer, the expansion bladder having an outer surface that is in communication with the coolant;
a semi-permeable membrane that is in communication with and substantially transmissive of atmospheric pressure, the semi-permeable membrane being positioned proximate a portion of the outer housing that does not include the radiation shielding layer; and
an air passage extending at least partially between the expansion bladder and the semi-permeable membrane such that an interior volume of the expansion bladder is subject to atmospheric pressure.
15. The x-ray tube as defined in claim 14, wherein the semi-permeable membrane is substantially non-transmissive of liquid so as to preclude leakage of the cooling liquid rupture of the tube or expansion bladder.
16. The x-ray tube as defined in claim 14, wherein the semi-permeable membrane is included in a membrane seal plug that is received in a hole defined in the outer housing.
17. The x-ray tube as defined in claim 14, wherein the air passage and the expansion bladder are composed of rubber.
18. The x-ray tube as defined in claim 16, wherein a fitting is interposed between an end of the air passage and the membrane seal plug, the fitting and the air passage defining an air passageway between the interior volume of the expansion bladder and the membrane seal plug.
19. The x-ray tube as defined in claim 14, wherein placement of the membrane seal plug precludes the need for modifying the lead shielding in order to subject the expansion bladder to atmospheric pressure.
20. The x-ray tube as defined in claim 14, wherein the radiation shielding layer surrounds the anode and the expansion bladder, and wherein the membrane seal plug is positioned proximate a stator of the x-ray tube.