Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2000-04-28
2002-03-26
Marmor, Charles A. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S138000
Reexamination Certificate
active
06361472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to controllers for automatic transmissions mounted on vehicles, and more particularly to improvements to vehicle start selection for an automatic transmission which duty-cycle controls its solenoid valves.
2. Background Art
One such conventional controller for an automatic transmission is disclosed, for example, in a published unexamined Japanese patent application 7-139615. In this controller, when start selection is made, for example, from an N-range to a D- or R- range, a drive frequency of respective solenoid valves which receive duty-cycle control is set to a value higher than those set in other gear shifting operations, for example in travelling, to thereby reduce an amplitude of vibrations of the hydraulic pressure produced in the solenoid valves and to restrict and prevent production of noise.
However, when a vehicle starts based on switching from the N-range to the D- or R-range, a transmission torque is generally small, for example, a hydraulic pressure required for each of the frictionally engageable elements is low, and a duty cycle for the respective solenoids is low. When the duty cycle is low, an output pressure from the solenoid valve is low, so that an amplitude of vibrations of the hydraulic pressure is small. Conversely, when the vehicle starts, it is at a zero speed where vehicle noise is very low. Thus, when the drive frequency of the solenoid valve increases, for example, the number of times a plunger and a ball hit each other within the solenoid valve increases, and its hitting energy is felt as a large operation sounds or noise. When, for example, the transmission torque is large and the oil pressure required for each frictionally engageable element is high a gear shift made while the vehicle is travelling, the duty cycle for each solenoid valve and vibrations of the hydraulic oil pressure can often be high. If the drive frequency of the solenoid valve decreases in such state where the vibrations of the hydraulic oil are high, fluctuations or changes of a quantity or speed of flow of the hydraulic oil increase, for example, when the solenoid is turned on and off increase. Thus, the vibrations of the hydraulic oil further increase. Those vibrations are transmitted as torque vibrations from the respective frictionally engageable elements to the vehicle and can be felt as abnormal sounds or vehicle body vibrations.
The present invention has been made in view of the above problems. It is therefore an object of the present invention to provide a control for an automatic transmission which restricts and prevents production of noise when the vehicle starts, and also which restricts and prevents production of abnormal sounds and vehicle body vibrations, for example, a gear shift made while the vehicle is travelling.
SUMMARY OF THE INVENTION
In order to achieve the above object, the present invention provides a controller for an automatic transmission for a vehicle comprising: start selection detecting means for detecting that start selection is made; and solenoid valve drive frequency changing means, responsive to the detecting means detecting that the start selection is made, for changing a drive frequency of a PWM (Pulse Wave Modulation) solenoid valve to a frequency lower than a drive frequency of the PWM solenoid valve used in gear shifting while the vehicle is travelling.
The start selection detecting means detects the range position of a shift lever which a driver manipulates and said start selection is to manipulate the shift lever to select a D range from a N range or a R range from the N range.
The duty cycle control referred to herein is to control a quantity of actuation of an electromagnetic (solenoid) valve or a quantity or speed of a flow of the hydraulic oil concerned by adjusting a duty cycle involving a so-called pulse width modulation. The start selection is to manipulate a select lever to select a D- or R- range from an N-range in a vehicle with an automatic transmission. The gear-shift in travel involves automatic gear-shift control provided depending on the vehicle speed or throttle opening.
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patent: 7-139615 (1995-05-01), None
Jatco Transtechnology Ltd.
Marmor Charles A.
Pang Roger
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