Interrelated power delivery controls – including engine control – Transmission control – Including fluid drive
Reexamination Certificate
1999-10-01
2001-01-09
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Including fluid drive
C477S158000, C477S162000
Reexamination Certificate
active
06171211
ABSTRACT:
TECHNICAL FIELD
The invention relates to automatic transmissions for automotive vehicles including a hydrokinetic torque converter.
BACKGROUND OF THE INVENTION
An electronically controlled automatic transmission for automotive vehicles has clutches and brakes for establishing and disestablishing torque flow paths through multiple-ratio gearing from a vehicle engine to vehicle traction wheels. A hydrokinetic torque converter is disposed between the engine and torque input elements of the gearing. The neutral idle control system of the invention is particularly adapted to be used in an automatic transmission control system of the kind disclosed, for example, in U.S. Pat. No. 5,389,046. A multiple-ratio gearing system for the transmission of the '046 patent is disclosed in U.S. Pat. No. 4,938,097.
Automatic transmissions having a torque converter and multiple-ratio planetary gearing, such as the transmissions disclosed in the '046 and '097 patents, do not have the ability to provide a neutral idle since the forward and reverse clutches are applied with line pressure. With the engine throttle closed, the line pressure for the control valve system is reduced, but the minimum value is relatively high (e.g., 50 psi). The forward drive clutch or the reverse clutch thus is fully engaged when the engine throttle is closed as the torque converter continues to deliver torque.
Attempts have been made to improve the driveline efficiency by unloading the converter when the engine is idling and the vehicle is at rest. Such control valve systems make it possible to reduce undesirable noise vibration and harshness in the driveline when the engine is idling and the automatic transmission is in a drive mode. U.S. Pat. No. 5,272,630 is an example of an attempt to avoid the noise vibration and harshness problem.
The '630 patent describes a control strategy for supplying a residual or threshold pressure to the fluid pressure actuators for the clutches at the beginning of the acceleration mode using an electronic, closed-loop controller. The actuators can be fully stroked at the instant the acceleration mode begins. The closed-loop controller compensates for changes in driveline variables such as changes in oil temperature and clutch spring forces, for example, so that each clutch engagement is repeatable.
The control system of the '046 patent, unlike the control system for the '630 patent, lacks the ability to provide neutral idle since the forward and reverse clutches are applied with a minimum value that is relatively high at the initiation of the acceleration mode. For that reason, the clutches remain applied when the engine idles and the vehicle is at rest.
The neutral idle feature described in the '630 patent requires the addition of extra solenoids, pressure accumulators, and extra valve elements in the control system, which adds complexity and manufacturing cost to the transmission compared to the control system of the '046 patent.
U.S. Pat. Nos. 4,938,097, 5,272,630 and 5,389,046 are owned by the assignee of the present invention.
BRIEF DESCRIPTION OF THE INVENTION
The improved control system of the present invention provides a neutral idle capability in both forward and reverse drive ranges without the addition of costly and complex solenoid valves, accumulators, and associated fluid circuitry. This is done by controlling the forward drive clutch or the reverse drive clutch so that the clutches will slip to emulate a neutral state. This slipping clutch mode requires the fluid pressure piston actuators for the clutches to be fully stroked to effect an immediate torque delivery state when the driver demands torque at the initiation of the acceleration mode of the vehicle. The neutral idle feature is achieved in the improved transmission system of the invention by providing only one additional valve and a slight modification to a shift valve element that controls ratio changes between the lowest ratio and an intermediate ratio.
The transmission that embodies the present invention, like the transmissions disclosed in the '097 patent, the '046 patent and the '630 patent, includes a pressure-operated torque converter bypass clutch, which is applied when the transmission operates in the low-gear ratio at the beginning of the acceleration mode. A main pressure regulator valve supplies regulated line pressure to the valve system. Line pressure is modulated in both forward and reverse drive. An engagement valve controls modulated line pressure distribution to a forward clutch or a low-and-reverse brake when the transmission is in the normal operating mode as well as when the transmission is in the neutral idle mode.
A torque converter bypass clutch for the transmission of the invention can be applied so that the hydrokinetic torque flow path through the converter is replaced with a mechanical torque flow path through the friction elements of the bypass clutch. The invention includes a means for multiplexing a bypass clutch control solenoid for the bypass clutch so that it is capable of acting as an actuator for the engagement valve to achieve a neutral idle condition when the transmission is in a neutral idle mode and for controlling the bypass clutch when the transmission is in the normal operating mode.
The pressure made available to each clutch (i.e., the forward clutch or the low-and-reverse brake) is controlled by a pressure regulator valve that responds to an electronic line pressure control solenoid. The electronic line pressure control solenoid is capable of establishing line pressure regulation and clutch and brake servo pressure during operation of the transmission in its normal operating mode, but it is capable also of functioning as one element of a forward clutch and low-and-reverse brake controller in conjunction with a pressure regulator valve when the transmission is in the neutral idle mode. The multiple functions achieved by the bypass clutch control solenoid and by the electronic line pressure control solenoid eliminate the requirement for additional valves and separate dedicated pressure controllers for the forward clutch and the low-and-reverse brake during neutral idle operation.
The present invention also eliminates the need for forward clutch and low-and-reverse brake accumulators normally used in the transmission disclosed in the '046 patent. The functions of the accumulators are provided instead by the electronic line pressure solenoid, which is used for forward clutch and low-and-reverse brake pressure regulation during the neutral idle operating mode. The removal of the low-and-reverse accumulator further simplifies the control system.
REFERENCES:
patent: 4843920 (1989-07-01), Hayasaki et al.
patent: 4938097 (1990-07-01), Pierce
patent: 5272630 (1993-12-01), Brown et al.
patent: 5389046 (1995-02-01), Timte et al.
patent: 5637053 (1997-06-01), Droste et al.
patent: 5865704 (1999-02-01), Takagi et al.
Ortmann Walter Joseph
Spaulding Todd Curtis
Estremsky Sherry
Ford Global Technologies Inc.
McKenzie Frank G.
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