Interrelated power delivery controls – including engine control – Transmission control
Reexamination Certificate
2000-07-12
2002-04-30
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
C477S039000, C477S044000
Reexamination Certificate
active
06379278
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a mechanical power transmission for driving a vehicle, which transmission transmits the driving force output from the engine to the drive wheels of the vehicle with a speed change being performed by a speed change mechanism.
1. Field of the Invention
Many such transmissions have been used for driving vehicles, and a variety of speed change mechanisms are incorporated in the transmissions, ranging from gear transmissions with a plurality of steps of speed change ratios to continuously variable transmissions with gradually varying speed change ratio controlled by means of a belt, etc. Recently, a hybrid transmission which uses an electrical motor in addition to an engine has been introduced for fuel efficiency. The applicant of the present invention is also developing a hybrid transmission. This hybrid transmission comprises a continuously variable transmission with a metal V-belt which is disposed around the common output shaft of the engine and the electrical motor arranged in series, and the output shaft of the continuously variable transmission is provided with a starting clutch (main clutch).
2. Description of the Related Art
One purpose for developing this transmission is to improve fuel efficiency. Therefore, desirably, the operation of the engine be controlled such that the engine stops its operation when the vehicle come into a halt (such control is here referred to as “idling elimination control”). As an idling elimination control, there is a method to stop the engine when the engine comes into an idling condition after the vehicle has stopped completely. However, while the vehicle is decelerating after the accelerator pedal once depressed has been released, an engine brake is effected. It is known that, during this deceleration, the fuel injection to the engine is terminated (or the supply of fuel is terminated). In consideration of this fuel supply termination, there is a more desirable way to eliminate engine idling. When the vehicle is decelerated to a halt, the fuel injection is terminated, and this condition of non-fuel supply should be maintained to stop the operation of the engine (this control is referred to as “engine strop control”).
Although this engine stop control successfully improves the fuel efficiency by terminating the fuel injection, there is still a need for improvement. In a prior-art engine stop control, after the operation of the engine is terminated, electricity is still kept flowing through a circuit which controls the speed change mechanism, especially through the solenoids of the linear solenoid valves that control the starting clutch and the variable widths of the pulleys of the metal belt type continuously variable transmission (this electricity is referred to as “base current”). This is somewhat wasteful. On the other hand, if this base current is terminated before the rotation of the engine ceases and the hydraulic pressure supplied from the oil pump becomes zero, then there will be another problem. In this case, the hydraulic pressures used for controlling the variable widths of the drive and driven pulleys will increase to a maximum value (generating a maximum thrust), and this condition may affect the durability of the metal belt, the drive and driven pulleys, etc. of the speed change mechanism.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a stop control system for a vehicular transmission which system conserves electricity by avoiding wasteful power consumption without causing any adverse effect to the durability of the speed change mechanism.
In order to achieve this objective, the present invention provides a stop control system for a mechanical power transmission used for driving a vehicle. Here, the power transmission comprises a speed change mechanism (for example, the continuously variable transmission CVT of the embodiment described in the following section), which transmits a driving force from an engine with a speed change. In this transmission, the engine is controlled to stop when the vehicle is brought into a halt. After the engine has stopped, a control that adjusts an electrical current controlling the speed change mechanism almost to zero (or substantially to zero) is executed.
In the transmission, whose engine is stopped when the vehicle is stopped, after the engine has stopped, there is no need to control the speed change mechanism. Therefore, the electrical current that controls the speed change mechanism is adjusted almost to zero according to the present invention. Because the control current is supplied as necessary before the engine stops, the durability of the speed change mechanism is not affected adversely. After the engine has stopped, the control current is terminated to avoid wasteful power consumption. Here, making the control current almost to zero means that the control current is reduced to a level at which only a weak current (normally, about a few mA~about a few 10 mA) is left flowing.
It is preferable that the control for adjusting the electrical current which controls the speed change mechanism almost to zero be executed after the engine has stopped, and after the hydraulic pressure which actuates the speed change mechanism has decreased. The hydraulic pressure for the speed change mechanism is generated by an oil pump, which is generally connected to the input shaft of the speed change mechanism and rotated by the engine. When the engine stops, the oil pump also stops, and the pressure decreases gradually. Just after the engine has stopped, the pressure in the hydraulic circuit has not decreased much. If the control current is adjusted almost to zero immediately in this condition, for example, the above mentioned problem that the hydraulic pressures used for controlling the variable widths of the drive and driven pulleys will increase to a maximum value and may affect the durability of the speed change mechanism. In the power transmission according to the present invention, the control current for the speed change mechanism is terminated after these hydraulic pressures have decreased. Thus, the electrical current not necessary after the termination of the operation of the engine is terminated to save electricity without any adverse effect to the durability of the speed change mechanism.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4126200 (1978-11-01), Miller et al.
patent: 5024638 (1991-06-01), Sakakibara et al.
patent: 6338695 (2002-01-01), Aoki et al.
patent: 62031533 (1987-02-01), None
patent: 4271941 (1992-09-01), None
Eguchi Takahiro
Katano Hiroyuki
Teshima Daihei
Armstrong Westerman & Hattori, LLP
Estremsky Sherry
Honda Giken Kogyo Kabushiki Kaisha
Lewis Tisha D.
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