1. Field of the Invention
The present application relates to a lubrication system for a two-cycle engine and, more particularly, to a lubrication system that incorporates a lubrication pump that pressurizes and delivers lubricant to a portion of a two-cycle engine.
2. Description of Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control. Recent two-cycle engines, therefore, incorporate a lubricant pump to deliver a desired amount of lubricant to lubricate internal portions of the engines. Mechanically operated pumps can be used as the lubricant pump. Such mechanical pumps, however, are not easily controlled to provide highly precise amounts of lubricant in response to engine operations. Electrically operable pumps tend to replace the mechanical pumps because higher precision controls are more widely available with such electrical pumps.
The electrical pumps can periodically pressurize lubricant under the control of a control device, such as, for example, an electronic control unit (ECU). The ECU can control a frequency of the periodic pressurization with, for example, an electronic control signal configured to operate the pump in accordance with a desired duty cycle. The higher the frequency, the greater the amount of the lubricant.
An electromagnetic solenoid pump is one type of such electrical pump. Japanese Laid Open Patent Publication 10-37730 discloses a lubrication system incorporating such an electromagnetic solenoid pump. The solenoid pump has a pumping piston reciprocally disposed in a pump housing. A plunger is coupled with the pumping piston. An electromagnetic solenoid can actuate the plunger. A control device controls the solenoid to selectively actuate or release the plunger such that the pumping piston periodically pressurizes the lubricant.
The control device disclosed in Japanese Laid Open Patent Publication 10-37730 has a control map that provides an amount of lubricant required by the engine versus an engine speed and determines a frequency of energization of the solenoid using the control map. The solenoid pump thus can pressurize a proper amount of lubricant in response to the engine speed of the engine.