The disclosure of Japanese Patent Application No. HEI 11-87167 filed on Mar. 29, 1999 including the specification, drawings and abstract are incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a control system for starting an engine installed in a vehicle, and more particularly to a control system provided with a plurality of starting systems.
2. Description of Related Art
An engine, such as a gasoline engine is constructed such that fuel-air mixture goes through an intake stroke and a compression stroke before being ignited to cause an explosive combustion, and the pressure generated thereby moves the piston to generate power, and the power is then transmitted to a crankshaft. The control system for the engine is provided with a starting system for rotating the crankshaft at a rotational speed equal to or greater than a predetermined rotational speed when starting the engine.
Japanese Patent Laid-Open No. HEI 9-117012 discloses a vehicle provided with such a starting system. The vehicle includes an electric motor, an engine, and a generator, which serve as power sources for driving the vehicle, and the generator is connected to the engine. The generator is operated as an electric motor to rotate the engine from a stopped state up to a predetermined idle speed. When the engine speed reaches the idle speed, the fuel is supplied to the engine and then ignited. Then, the generator is no longer operated as an electric motor.
In addition to the aforementioned publication, there is also suggested a start control system of a vehicle equipped with an electric motor for driving auxiliaries of a vehicle and a starter motor provided exclusively for engine start, wherein at least one of the electric motor and the starter motor can be used for starting the engine.
However, because a single generator is used to serve as the electric motor for starting the engine, the startability of the engine is adversely affected due to nonconformance of the rotational speed or the torque of the electric motor with the state of the vehicle. Also, because a single generator is used to serve as the electric motor, the startability of the engine is adversely affected when the state of charge of the battery for supplying electrical energy to the electric motor is insufficient to start the engine. Moreover, a pair of large and small spur gears are usually employed as means for power transmission between the starter motor and the engine. Accordingly, there exists the possibility of noise being generated at engine start depending on specifications of the spur gear mesh and the selection of the engine starting mode.
The invention has been made in the light of the aforementioned circumstances and therefore it is an object of the invention to provide a start control system capable of improving the engine startability in conformance with the state of a vehicle.
In a first aspect of the invention, an engine start control system includes a plurality of starting systems capable of starting the engine, and a controller. The controller determines a first associated amount associated with the rotational resistance of the engine, and then selects the mode of starting the engine by the plurality of starting systems in accordance with the determination results. The first associated amount refers to a phenomenon or a state which allows a direct or indirect determination of the engine rotational resistance.
According to the first aspect, the first associated amount associated with the engine rotational resistance is determined, and the starting mode of the engine is selected based on the determination result of the first associated amount. For example, the starting mode of the engine is selected such that a torque corresponding to the rotational resistance of the engine is obtained. That is, when the rotational resistance of the engine is comparatively high, the starting mode of the plurality of starting systems is selected so that a high starting torque can be obtained. This improves the startability of the engine irrespective of the rotational resistance of the engine.
The first associated amount may be the viscosity of the engine oil or the temperature of the engine cooling water. The rotational resistance of the engine is estimated based on the viscosity of the engine oil or the temperature of the engine cooling water.
In a second aspect of the invention, the engine start control system provided with a plurality of starting systems capable of starting the engine is also capable of driving a functional device other than the engine using either one or more of the starting systems. The controller of the engine start control system further determines a drive state of the functional device and selects the mode of starting the engine by the plurality of starting systems based on the determined drive state. The drive state of the functional device may be the rotational speed of the functional device, for example.
According to the second aspect, the drive state of the functional device is determined, and the mode of starting the engine by the plurality of starting systems is selected based on the determination result. For example, the starting mode of the engine is selected so that a rotational speed appropriate for starting the engine can be obtained. That is, when the functional device is driven by either one or more of the starting systems and when the rotational speed of the starting system is comparatively high, the engine can be rotated by a starting system that is driving a functional device after the engine is rotated by a starting system that is not driving a functional device. This makes it possible to gradually increase the engine rotational speed, whereby the startability of the engine is improved.
According to a third aspect of the invention, an engine start control system includes a plurality of starting systems capable of starting the engine, a plurality of energy sources which supply energy to respective starting systems, and a controller that determines the states of the plurality of energy sources, and selects the mode of starting the engine by the plurality of starting systems based on the determined states of the plural energy sources.
According to the third aspect, the states of the plurality of energy sources are determined, and the mode of starting the engine by the plurality of starting systems is selected based on the determination result. For example, the starting mode of the engine is selected so that an energy appropriate for starting the engine can be obtained. That is, by selecting a starting mode for starting the engine with a starting system having a higher energy state, the startability of the engine can be improved and a decrease in the energy amount of a starting system having a lower energy state can be suppressed.
According to a fourth aspect of the invention, an engine start control system includes a power transmission member which transmits power from the engine or from at least one of the power sources other than the engine, a plurality of starting systems capable of starting the engine, and a controller that determines a second associated amount associated with the vehicle speed in a state where the vehicle is run by power from the power source, and then selects for selecting the mode of starting the engine by the plurality starting systems based on the determined second associated amount. The second associated amount refers to a phenomenon or a state which allows a direct or indirect determination of the vehicle speed.
According to the fourth aspect, a difference between the engine rotational speed and the rotational speed of the power transmission member is estimated based on the second associated amount associated with the vehicle speed, and the starting mode of the engine is selected based on the estimation result.
In accordance with the first through fourth aspects of the invention, the selection of the starting mode of the engine involves selection of which starting system function (rotational speed, torque, and the like) to use, the number of starting systems employed for starting the engine, and the timings for driving and stopping each starting system when a plurality of starting systems are used.
According to a fifth aspect of the invention, an engine start control system includes a first starting system capable of starting the engine by transmitting power to the engine via a gear transmission, a second starting system capable of starting the engine by transmitting power from the engine via a belt transmission, and a controller that, upon starting the engine, first drives the first starting system, then drives the second starting system and continues driving the second starting system even after the first starting system is stopped.
According to the fifth aspect, upon engine start, first, the first starting system is driven and the power is transmitted to the engine via the gear transmission. Then, the second starting system is driven, and the power is transmitted to the engine via the belt transmission. The engine is driven by the power transmitted from the second starting system after the first starting system is stopped. For example, the drive time of the first starting system, which transmits power to the engine via the gear transmission, is set short, so that the generation of noise due to engine start can be suppressed. The belt transmission, which transmits power from the second starting system to the engine, prevents generation of gear noise and abnormal sounds due to backlash as compared to the gear transmission upon engine start. Also, the belt transmission does not require lubricating oil for cooling and lubricating the engaging portions because the device does not contain any engaging portions such as in the gear transmission. Accordingly, temperature increase or power loss caused by agitation of the lubricating oil is eliminated. Also, the construction of the belt transmission is simple because it does not require a lubricating system.
According to a sixth aspect of the invention, an engine start control system includes a first starting system connected to a crankshaft of the engine, a second starting device connected to the crankshaft of the engine, and a controller that, upon starting the engine, first drives the first starting system, then drives the second starting system before driving of the first starting system is terminated.
According to the sixth aspect, the engine is started by drive of the first and the second starting systems in parallel, whereby the startability of the engine is improved.