Power plants – Internal combustion engine with treatment or handling of... – Divider – collector – valve means – or boundary layer device...
Reexamination Certificate
2000-05-23
2001-11-27
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Divider, collector, valve means, or boundary layer device...
C060S274000, C060S277000, C060S287000
Reexamination Certificate
active
06321533
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Application Nos. 11-143210 filed on May 24, 1999 and 2000-85369 filed on Mar. 24, 2000 including the specifications, drawings and abstracts are incorporated herein by reference in their entire ICS .
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an exhaust passage switching unit and method for an internal combustion engine and, more particularly, to an exhaust passage switching unit and method capable of precisely judging the state of a switching mechanism for switching an exhaust passage.
2. Description of Related Art
Exhaust passage switching units as disclosed, for example, in Japanese Patent Application No. 8-334014 have been known. A switching unit of this type is equipped with a switching valve which switches exhaust gases to a main exhaust passage in which a catalyst is disposed or to a bypass passage. In an operating state with a high rotational speed and a high load, deterioration caused by overheating of the catalyst is prevented by switching the exhaust passage to the bypass passage.
When the main exhaust passage serves as the exhaust passage, the flow resistance of the exhaust passage increases because of the resistance of the catalyst. If the flow resistance of the exhaust passage increases, the negative pressure in an intake pipe decreases accordingly. Hence, according to the switching unit of the related art, it is determined, based on a change in negative pressure in the intake pipe when a switching signal is supplied to the switching valve, whether or or the exhaust passage has been switched, that is, whether or not the switching valve is in normal operation.
However, the negative pressure in the intake pipe changes depending not only on a flow resistance of the exhaust passage but also on an operating state of the internal combustion engine. Thus, it is difficult to distinguish between a change in negative pressure in the intake pipe caused by the switching of the exhaust passage and a change in negative pressure in the intake pipe caused by an operating state of the internal combustion engine. The method in the aforementioned switching unit of the related art does not necessarily permit precise judgment of an operational state of the switching valve.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an exhaust passage switching unit for an internal combustion engine which permits precise judgment of the state of a switching mechanism for switching an exhaust passage.
In a first aspect of the invention, an exhaust passage switching unit for an internal combustion engine comprises a switching mechanism which has a moving member driven by a fluid pressure and a pressure transmitting portion for transmitting a fluid pressure of a fluid pressure source to the moving member, wherein the switching member switches an exhaust passage in accordance with a movement of the moving member, a transmitting portion pressure detector that detects a pressure of the pressure transmitting portion, a controller that determines a state of the switching mechanism based on a pressure detected by the transmitting portion pressure detector.
In the first aspect of the present invention, the pressure transmitting portion transmits a fluid pressure to the moving member. The moving member is driven by the fluid pressure transmitted by the pressure transmitting portion, whereby the exhaust passage is switched. If a fluid pressure in the fluid pressure source is supplied to the pressure transmitting portion, the pressure in the pressure transmitting portion changes towards the pressure in the fluid pressure source. In this case, the volume in the pressure transmitting portion changes in accordance with an amount of movement of the moving member, whereby the pressure in the pressure transmitting portion also changes. That is, the change in pressure of the pressure transmitting portion reflects an operating state of the moving member. Thus, the controller can determine a state of the switching mechanism based on a pressure in the pressure transmitting portion detected by the transmitting portion pressure detector.
In the case where the switching mechanism is in normal operation, while the moving member moves in the course of a change in pressure of the pressure transmitting portion towards the pressure in the fluid pressure source, the volume of the pressure transmitting portion changes in such a direction as to attenuate changes in pressure therein. As a result, the absolute value of a gradient of changes in pressure decreases. On the contrary, if the switching mechanism is locked, the moving member does not move. Therefore, the aforementioned change in gradient of changes in pressure does not occur.
In the first aspect of the present invention, the controller may judge presence or absence of locking of the switching mechanism based on whether or not there is a period when an absolute value of a gradient of changes in pressure detected by the transmitting portion pressure detector becomes equal to or smaller than a predetermined value within a predetermined period after start of a switching operation of the exhaust passage by the switching mechanism.
The controller may judge presence or absence of locking of the switching mechanism based on whether or not there is a period when an absolute value of a change amount of a gradient of changes in pressure detected by the transmitting portion pressure detector becomes equal to or smaller than a predetermined value within a predetermined period after start of a switching operation of the exhaust passage by the switching mechanism.
If the switching mechanism is locked, the volume of the pressure transmitting portion changes depending on the locking position of the switching mechanism. In this case, the gradient of changes in pressure at the time of supply of a fluid pressure of the fluid pressure source to the pressure transmitting portion changes in accordance with a volume of the pressure transmitting portion.
Thus, in the aforementioned aspect, if it is determined that the switching mechanism is locked, the controller may determine a locking position of the switching mechanism based on a gradient of changes in pressure detected by the transmitting portion pressure detector.
If there arises a malfunction such as pressure leakage in the pressure transmitting portion, the pressure in the pressure transmitting portion does not reach the pressure in the fluid pressure source.
Thus, in the first aspect of the present invention, the controller may be constructed to judge presence or absence of a malfunction in the pressure transmitting portion based on a pressure detected by the transmitting portion pressure detector after lapse of a predetermined length of time since start of a switching operation of the exhaust passage by the switching mechanism.
While the moving member moves in the course of a change in pressure of the pressure transmitting portion towards the pressure in the fluid pressure source, the volume of the pressure transmitting portion changes in such a direction as to attenuate changes in pressure therein. As a result, the absolute value of the gradient of changes in pressure decreases. That is, the absolute value of a change amount of the gradient of changes in pressure increases. If the moving member has moved to its maximum after a decrease in absolute value of the gradient of changes in pressure, the volume of the pressure transmitting portion does not change afterwards. As a result, the absolute value of the gradient of changes in pressure increases. That is, the absolute value of the change amount of the gradient of changes in pressure increases.
Thus, in the aforementioned aspect, the may be constructed controller to determine an amount of movement of the moving member based on a period from a moment when an absolute value of a change amount of a gradient of changes in pressure detected by the transmitting portion pressure detector becomes equal to or greater than a first predetermined value after start of a switchin
Hoshi Koichi
Sakurai Kazuhiro
Watanabe Takashi
Denion Thomas
Nguyen Tu M.
Olff & Berridge, PLC
Toyota Jidosha & Kabushiki Kaisha
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