Electric heating – Heating devices – Resistive element: igniter type
Reexamination Certificate
2001-03-22
2002-07-02
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
Resistive element: igniter type
C123S14500A
Reexamination Certificate
active
06414273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a glow plug control apparatus for controlling a glow plug so as to accelerate the ignition/combustion of a fuel by said glow plug or detect ions generated during the combustion of a fuel by said glow plug and a glow plug therefor.
2. Description of the Related Art
The recent trend is for more diesel engines having a high heat efficiency to be mounted on passenger cars for the purpose of enhancing fuel economy. Under these circumstances, the users have demanded further enhancement of fuel economy as well as further improvement of prevention of vibration or noise and actuation properties which are inferior to gasoline engine. On the other hand, from the standpoint of environmental protection, the exhaust gas has been demanded to be more clean.
In order to meet this demand, as disclosed in Japanese Patent Unexamined Publications No. Hei. 10-9113 and Hei. 10-77945, a feedback control has been proposed involving the use of results of detection of ions produced during the combustion of a fuel for the purpose of controlling the timing or amount of fuel injection in the engine. As a method of detecting ions there is particularly proposed a method involving the measurement of ionic current flowing due to the presence of ions produced by the application of a voltage across the glow plug and the inner wall of the combustion chamber of an engine.
Heretofore, a glow plug has played a role ranging from aiding actuation to stabilizing the engine drive until the completion of warming up and thus has normally not been energized after the completion of warming up. However, it has been made obvious that it is effective for the reduction of vibration or noise of the engine and purification of exhaust gas to energize the glow plug even after the warming-up of the engine so that the glow plug is kept at a relatively high temperature. A system has been proposed involving the energization of a glow plug depending on the operating conditions for the purpose of controlling the temperature of the glow plug to not lower than a predetermined temperature.
However, the above cited JP-A-10-9113 and JP-A-10-77945 merely disclose a system involving the energization of a glow plug before actuation (pre-glow period) and during the warming-up of the engine (after-glow period) and the use of the glow plug only for the detection of ionic current. In other words, the invention disclosed in the above cited patents cannot energize the glow plug even after the completion of warming-up to detect ionic current and control the engine. It is preferred that ionic current be detected to control the engine also in the stage before the completion of warming-up such as pre-glow period and after-glow period. However, when the system is arranged such that switching is made from the energization of the glow plug to the measurement of ionic current or vice versa during pre-glow period, particularly in the initial stage of energization of glow plug, it is likely that the temperature rise of the glow plug during pre-glow period can be delayed, deteriorating the actuation properties.
SUMMARY OF THE INVENTION
The present invention has been worked out in the light of the foregoing problems. An object of the present invention is to provide a glow plug control apparatus which can keep the temperature of the glow plug to not lower than a predetermined temperature even after the lapse of the stage after pre-glow period and the stage during the warming-up of an engine in addition to during these stages to lessen the vibration or noise of the engine and clean the exhaust gas and can detect ions produced during the combustion of a fuel to control the engine. Also, a glow plug suitable for the glow plug control apparatus and a method of detecting ions in the combustion chamber of an engine which has been warmed up are provided. Another object of the present invention is to provide a glow plug control apparatus which exhibits good actuation properties without deterring the temperature rise of the glow plug during pre-glow period.
To solve the foregoing problems, the present invention provide a glow plug control apparatus comprising a glow plug including a housing fixed to an engine, a heating element insulated from the housing which generates heat when energized by electric current supplied through two conductive paths at least either before or after the completion of warming-up of the engine and a ceramic heater having an exposed portion which is heated by the heating element and exposed to the interior of the combustion chamber of the engine; a glow plug energization controlling means for controlling the energization of the heating element of the glow plug depending on the surface temperature of the exposed portion so as to raise or keep the surface temperature to not lower than a predetermined temperature; an ion detecting means for detecting ions in the combustion chamber using the glow plug; a switching means for switching the state of the glow plug from the state of being controlled in energization by the glow plug controlling means to the state of being detected in ion by the ion detecting means or vice versa; and a switching command means for commanding the switching from the state of being controlled in energization to the state of being detected in ions by the switching means for a predetermined period of time from the time of injection of fuel into the combustion chamber when the surface temperature of the exposed portion is not lower than the predetermined temperature.
In accordance with the glow plug control apparatus of the invention, the glow plug energization controlling means controls such that the surface temperature of the exposed portion of the ceramic heater is raised or kept to not lower than a predetermined temperature. When the surface temperature of the exposed portion is not lower than the predetermined temperature, the switching command means commands the switching means to switch the state of being controlled in energization to the state of being detected in ions for a predetermined period of time from the time of injection of fuel.
For example, before the actuation of the engine, the glow plug is energized. The detection of ions is not conducted before the temperature thereof rises from a temperature as low as ordinary temperature to the predetermined temperature.
However, when the temperature of the glow plug reaches not lower than the predetermined temperature, the state of the glow plug is switched from the state of being controlled in energization to the state of being detected in ions for a predetermined period of time from the time of injection of a fuel into the combustion chamber. Accordingly, the detection of ions can be conducted in the internals of the rise of the temperature of the glow plug. Thus, engine control during actuation is made possible.
Thereafter, also in the stage of actuation and warming up of the engine, the surface temperature of the exposed portion of the glow plug is kept to the predetermined temperature at lowest, making it possible to detect ions. Accordingly, the engine control during warming-up can be conducted.
In accordance with the glow plug control apparatus, the surface temperature of the exposed portion of the glow plug is kept to the predetermined temperature at lowest even after the completion of warming-up. In this manner, the vibration and noise of the engine can be lessened and the exhaust gas can be cleaned. Further, ions produced by the combustion of the fuel can be detected, making it possible to control the engine.
The foregoing control may be conducted either before or after the completion of warming up of the engine. Accordingly, the foregoing control may be conducted at any time between pre-glow period before the actuation of the engine and after-glow period after the actuation of the engine and during the period after the completion of warming up.
Further, the foregoing control may be conducted at any time between before the actuation of the engine and before the completion of w
Nagasawa Masakazu
Suzuki Hiroyuki
Taniguchi Masato
Jeffery John A.
NGK Spark Plug Co. Ltd.
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