Internal-combustion engines – Combustion chamber means combined with air-fuel mixture... – Air or combustible mixture entering the combustion chamber...
Reexamination Certificate
2000-12-05
2003-09-30
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Combustion chamber means combined with air-fuel mixture...
Air or combustible mixture entering the combustion chamber...
C123S090110, C251S129150
Reexamination Certificate
active
06626146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electromagnetic valve drive apparatus of an internal combustion engine and, more particularly, to an internal combustion engine electromagnetic valve drive apparatus in which intake valves and/or exhaust valves provide for a plurality of cylinders with valve-opening electromagnetic valves, valve-closing electromagnetic valves, and closed valve state holding mechanisms that do not employ electromagnetic force, and in which drive circuits are provided for the electromagnetic valves, whereby the valves are opened and closed.
2. Description of the Related Art
The disclosure of Japanese Patent Application No. HEI 11-347396 filed on Dec. 7, 1999 is herein incorporated by reference.
Known electric valves are used as intake valves or exhaust valves of internal combustion engines. An example of electromagnetic valves an armature displaceable with a valve body, a pair of electromagnetic coils disposed above and below the armature, and springs that urge the valve body toward a neutral position, as described in Japanese Patent Application Laid-Open No. HEI 8-284626.
In the electromagnetic valve, the valve body and the armature are held at the neutral position by the forces from the springs when neither one of the electromagnetic coils is supplied with an exciting current. When the upper electromagnetic coil is supplied with an exciting current, the valve body and the armature are magnetically drawn toward the upper electromagnetic coil. Conversely, when the lower electromagnetic coil is supplied with an exciting current, the valve body and the armature are magnetically drawn toward the lower electromagnetic coil. Therefore, this conventional electromagnetic valve is able to open and close the valve body by supplying suitable exciting current alternately through the electromagnetic coils.
In view of the responsiveness of the electromagnetic valve in opening and closing actions, durability of the electromagnetic valve, and the like, it is necessary to control the quantity of current through the electromagnetic coils with a high responsiveness. Thus, the exciting current supplied to each electromagnetic coil is controlled by an H-shape bridge circuit. The H-shape bridge circuit is formed by the terminals of the electromagnetic coils and four switching elements, each of which is provided between one of the terminals of the electromagnetic coil, and a high potential side or a low potential side.
In the H-bridge circuit, a voltage can be applied to the electromagnetic coil to supply an exciting current in a forward direction by turning on a pair of switching elements located diagonally about the electromagnetic coil and turning off the other pair of switching elements. By reversing the on/off states of the two pairs of switching elements, a voltage in a direction opposite to the exciting current can be applied to the electromagnetic coil. Therefore, by switching the on/off states of the switching elements of the H-bridge circuit, it is possible to quickly discontinue the production of electromagnetic force from the electromagnetic coil, and to supply a reverse current through the electromagnetic coil immediately after the discontinuation of electromagnetic force. Conversely, when a current is flowing through the electromagnetic coil in the direction opposite to the exciting current, it is possible to quickly discontinue the production of electromagnetic force from the electromagnetic coil in the reverse direction, or to deliver a current through the electromagnetic coil in the forward direction immediately after the discontinuation of reverse electromagnetic force, by applying a voltage to the electromagnetic coil in the forward direction.
In this manner, the quantity of current through each electromagnetic coil can be controlled with a increased responsiveness.
However, in order to achieve such a increased responsiveness, it is necessary to provide four switching elements for each electromagnetic coil as described above. Because each electromagnetic valve needs to have two electromagnetic coils, such as, a valve-closing electromagnetic valve and an valve-opening electromagnetic valve, the total number of switching elements needed for each electromagnetic coil becomes eight. Therefore, in the case of a four-cylinder four-valve engine, 128 switching elements are needed for the 16 valves, thus leading to a size increase and a cost increase of the electromagnetic valve drive apparatus.
In order to solve this problem, a drive apparatus for electromagnetic valves are known in which the number of switching elements is reduced while the functions of the electromagnetic valve drive apparatus are maintained, as described in Japanese Patent Application Laid-Open No. HEI 11-166657. This drive apparatus for electromagnetic valves has a drive circuit. The drive circuit includes series circuits having three switching elements connected in series and arranged in parallel for a group of electromagnetic valves that perform identical operations. In this circuit construction, switching elements are used collectively for a plurality of electromagnetic valves. That is, this construction reduces the need to provide dedicated switching elements for each electromagnetic valve. Therefore, if this three-switching-elements-in-series type drive circuit is applied to a four-cylinder four-valve engine, only 72 switching elements are needed for the 16 valves. The size and cost of the electromagnetic valve drive apparatus may be reduced.
However, even with the sharing of switching elements, the total number of switching elements employed is still large. A need has arisen for a further reduction in the number of switching elements to reduce the size and cost of the electromagnetic valve drive apparatus.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an electromagnetic valve drive apparatus of an internal combustion engine that allows a further reduction in the number of switching elements.
To achieve the aforementioned and other objects, an electromagnetic valve drive apparatus of an internal combustion engine includes valve-closing electromagnetic coils provided for intake valves and/or exhaust valves. The valves are provided for a plurality of cylinders. The electromagnetic drive apparatus includes valve-opening electromagnetic coils provided for the intake valves and/or the exhaust valves, and a mechanism that holds the intake valves and the exhaust valves in a closed state without using an electromagnetic force. The electromagnetic valve drive apparatus also includes a drive circuit provided for the electromagnetic coils, so that the electromagnetic valve drive apparatus opens and closes the valves. The drive circuit is provided for a valve group of valves, including a plurality of valves that perform identical operations and has at least one valve whose open period does not overlap an open period of the plurality of valves that perform identical operations. In the drive circuit, a plurality of series circuits are connected in parallel between a high electric potential side and a low electric potential side. Each series circuit is formed by connecting a plurality of switching elements in series. The electromagnetic coils are provided individually for the valves of the valve group and are connected between the series circuits.
Thus, the drive circuit is provided collectively for a valve group that consists of a plurality of valves that perform identical operations and at least one other valve whose open period does not overlap the open period of the valves that perform identical operations. The drive circuit is constructed to have a plurality of series circuits connected in parallel between the high electric potential side and the low electric potential side. Each series circuit is formed by connecting a plurality of switching elements in series. The electromagnetic coils are provided individually for the valves of the valve group and are connected between the series circuits.
The electromagnetic coils drive
Makita Mitsugu
Yanai Akihiro
Castro Arnold
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
Yuen Henry C.
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