1. Field of the Invention
The present invention generally relates to a solenoid valve control apparatus, and more particularly to a control apparatus for controlling a solenoid valve that functions to displace one of an intake valve or an exhaust valve of an internal combustion engine.
2. Description of the Related Art
As disclosed in Japanese Laid-Open Patent Application No.7-335437, a conventional solenoid valve that serves to displace one of an intake valve or an exhaust valve of an internal combustion engine is known. The intake valve or the exhaust valve is provided with a valve element, which is displaced between a valve-open position and a valve-closed position in order to open or close a passage between the engine port and the combustion chamber. The solenoid valve controls the movement of the valve element by a cooperation of a resilient force of an elastic member and an electromagnetic force of a solenoid coil. By electrically controlling the solenoid valve, it is possible to set the passage between the engine port and the combustion chamber in the open condition or the closed condition.
However, it should be noted that an internal pressure of the engine cylinder and a pressure of the engine port are exerted on the valve element of the intake valve or the exhaust valve. The engine cylinder pressure functions to displace the valve element in a valve-closing direction toward the valve-closed position, and the engine port pressure functions to displace the valve element in the opposite direction toward the valve-open position. As the engine cylinder pressure and the engine port pressure often fluctuate during operation of the engine, the electromagnetic force needed to displace the valve element from the valve-closed position to the valve-open position and the electromagnetic force needed to displace the valve element from the valve-open position to the valve-closed position considerably change.
In order to properly operate the solenoid valve with low power consumption, it is desirable to control the magnitude of the electromagnetic force to displace the valve element from the valve-closed position to the vale-open position or vice versa, so as to make it as small as possible. In order to properly operate the solenoid valve with a reliable smooth valve element operation even if the engine cylinder pressure and the engine port pressure on the valve element of the intake valve or the exhaust valve fluctuate, it is necessary to properly adjust the magnitude of the electromagnetic force to displace the valve element in the valve-opening direction or in the opposite valve-closing direction, in accordance with the engine cylinder/port pressure acting on the valve element.
However, in the above-mentioned solenoid valve, the influences of the valve-element pressure onto the electromagnetic force to displace the valve element are not at all taken into consideration. It is difficult for the above-mentioned solenoid valve to adjust the to displace the valve element between the valve-open position and the valve-closed position with low power consumption when the engine cylinder/port pressure acting on the valve element considerably fluctuates.
An object of the present invention is to provide an improved solenoid valve control apparatus in which the above-described problems are eliminated.
Another object of the present invention is to provide a solenoid valve control apparatus that properly adjusts the magnitude of an electromagnetic force to displace the valve element from one of the valve-open position and the valve-closed position to the other position, to a controlled value based on the pressure acting on the valve element.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides a solenoid valve control apparatus which controls a solenoid valve, the solenoid valve displacing a valve element between a valve-open position and a valve-closed position by a cooperation of a resilient force of an elastic member and an electromagnetic force of a solenoid coil, the solenoid valve control apparatus including: a pressure detection means for directly or indirectly detecting a pressure acting on the valve element; and an electromagnetic force adjustment means for adjusting, when the valve element is displaced from one of the valve-open position and the valve-closed position to the other position, the magnitude of an electromagnetic force to displace the valve element to the other position, to a controlled value based on the valve-element pressure detected by the pressure detection means.
In the solenoid valve control apparatus of the above preferred embodiment of the invention, the electromagnetic force to displace the valve element from one of the valve-open position and the valve-closed position to the other position is properly adjusted to the controlled value based on the valve-element pressure. The electromagnetic force is not significantly influenced even if the valve-element pressure changes due to the fluctuations of the operating conditions of the engine. The solenoid valve control apparatus of the above preferred embodiment is effective in properly adjusting the magnitude of the electromagnetic force to the controlled value based on the valve-element pressure. The solenoid valve control apparatus of the above preferred embodiment can provide the least possible electromagnetic force that is needed to displace the valve element. It is possible to properly operate the solenoid valve with low power consumption and with a reliable smooth valve element operation.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus in which the pressure detection means includes cylinder pressure detection means for detecting an internal pressure of a cylinder of an internal combustion engine, and the pressure detection means detects the valve-element pressure based on the internal pressure of the engine cylinder.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the internal pressure of the engine cylinder. The solenoid valve control apparatus of this embodiment can directly detect the valve-element pressure with high accuracy.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means further includes port pressure detection means for directly or indirectly detecting a port pressure of the engine, and the pressure detection means detects the valve-element pressure based on a difference between the engine cylinder pressure and the engine port pressure.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the difference between the engine cylinder pressure and the engine port pressure. The solenoid valve control apparatus of this embodiment can detect the valve-element pressure with high accuracy. The engine port pressure can be directly detected by using a port pressure sensor that senses a port pressure of the engine, or can be indirectly detected through a mapping from the engine speed to the engine port pressure.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means includes elastic-member strain detection means for detecting an amount of strain of the elastic member when a predetermined period has elapsed after a start of the displacement of the valve element, and the pressure detection means detects the valve-element pressure based on the amount of strain of the elastic member.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the amount of strain of the elastic member. The correlation between the amount of strain of the elastic member and the pressure acting on the valve element is utilized to detect the valve-element pressure, and the solenoid valve control apparatus of this embodiment can detect the valve-element pressure with high accuracy.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means includes elastic-member length detection means for detecting a whole length of the elastic member when a predetermined period has elapsed after a start of the displacement of the valve element, and the pressure detection means detects the valve-element pressure based on the whole length of the elastic member.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the whole length of the elastic member. The correlation between the whole length of the elastic member and the pressure acting on the valve element is utilized to detect the valve-element pressure, and the solenoid valve control apparatus of this embodiment can detect the valve-element pressure with high accuracy.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means includes load detection means for detecting a load of an internal combustion engine, and the pressure detection means detects the valve-element pressure based on the engine load.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the engine load. The engine load correlates with the engine cylinder pressure. The solenoid valve control apparatus of this embodiment can detect or estimate the valve-element pressure with high accuracy by utilizing the correlation between the engine load and the engine cylinder pressure. The engine load can be detected based on a vacuum pressure of the intake pipe of the engine, an amount of air taken in the engine, and a position of the throttle valve of the engine.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means further includes port pressure detection means for directly or indirectly detecting a port pressure of the engine, and the pressure detection means detects the valve-element pressure based on the engine load and the engine port pressure.
In the solenoid valve control apparatus of the above preferred embodiment, the valve-element pressure is detected based on the engine load and the engine port pressure. The solenoid valve control apparatus of this embodiment can detect the valve-element pressure with high accuracy. The engine port pressure can be directly detected by using a port pressure sensor that senses a port pressure of the engine, or can be indirectly detected through a mapping from the engine speed to the engine port pressure.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus which further includes transient-condition detection means for detecting a transient condition of the engine in which a transient change of the engine load occurs, wherein the electromagnetic force adjustment means adjusts, when the transient condition is detected, the magnitude of the electromagnetic force to a controlled value which is compensated for the change of the engine load.
The solenoid valve control apparatus of the above preferred embodiment is effective in properly adjusting the magnitude of the electromagnetic force to a controlled value based on the valve-element pressure even when the transient condition of the engine exists. When the vehicle operator intends to abruptly accelerate or decelerate the vehicle, there will exist the transient condition of the engine in which the engine load quickly changes. In this transient condition, the engine load may quickly change prior to the adjustment of the electromagnetic force based on the valve-element pressure. In the solenoid valve control apparatus of this embodiment, when the transient condition is detected, the magnitude of the electromagnetic force is adjusted to a controlled value which is compensated for the change of the engine load.
In order to achieve the above-mentioned objects, one preferred embodiment of the present invention provides the solenoid valve control apparatus wherein the pressure detection means includes high-pressure condition detection means for detecting a high-pressure condition in which the valve-element pressure is larger than a predetermined high pressure, and the electromagnetic force adjustment means adjusts, when the high-pressure condition is detected, the magnitude of the electromagnetic force to displace the valve element to the other position, to a controlled value based on the predetermined high pressure.
In the solenoid valve control apparatus of the above preferred embodiment, when the high-pressure condition is detected, the magnitude of the electromagnetic force to displace the valve element to the other position, is adjusted to a controlled value based on the predetermined high pressure. At a start of the operation of the internal combustion engine, a very high pressure is likely to act on the valve element. Even when the high-pressure condition exists, the solenoid valve control apparatus of this embodiment can provide a reliable, smooth valve element operation.