Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1990-01-26
1992-01-14
Braun, Leslie A.
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
74878, 74866, B60K 4106
Patent
active
050799738
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to an electronically controlled hydraulic speed change stage control system equipped in an automatic transmission.
2. Background Art
In a general automatic transmission, speed is changed by a shift tower manually operated by a driver. This shift tower is so designed that speed change stages P-R-N-D-2--1 are arranged in line and the shift tower can not be shifted to P-range position (parking) and R-range position (reverse) if a push button of the shift tower is not pushed, so as to avoid selection of P-range or R-range position due to maloperation when a vehicle is moving forward.
However, some drivers have a bad habit of shifting the shift tower while pushing the push button even during forward driving. And, in this case, fail-safe function does not work for preventing the shifting to P-range or R-range position by the use of the push button during forward driving.
Even in 2-range or 1-range position provided for fixing the speed-change stage, it is desirable that the electronic control is enabled.
In the event of failure in the electronic control, it is desirable that the speed-change stage is fixed to second speed mode in 2-range position and to first speed mode in 1-range position even if, for example, a power source for electronic control is turned off.
DISCLOSURE OF THE INVENTION
This invention provides a hydraulic speed change stage control system, in which a planetary gear transmission is installed at a rear stage of a torque converter transmitting an engine power through means of fluid and the planetary gear transmission is hydraulically controlled by an electronic control means working in cooperation with speed-change operation of driver; characterized by that a shift limiting valve driven by a control solenoid valve controlled by the electronic control means is installed between a manual shift valve working in cooperation with the speed-change operation of the driver and shift valves driven by solenoid valves controlled by the electronic control means, and the control solenoid valve is controlled by the electronic control means to actuate the shift limiting valve when a vehicle is moving forward at a specified or higher speed so that the planetary gear transmission is not changed to a reverse drive mode even if the driver changes a drive stage to the reverse drive mode.
Since oil passages are closed by the shift limiting valve in the above-mentioned structure, the planetary gear transmission is not changed to the reverse drive mode under a state where the vehicle is moving forward at a specified or higher speed. Accordingly, the fail-safe function also works on the maloperation of shifting to R-range position with the push button being pushed during the forward driving
Under the state where the vehicle is moving forward at a specified or higher speed, even if the driver changes the drive mode to the second or first speed stage, the planetary gear transmission is not changed directly to the second or first speed but the electronic control means carries out a speed change control appropriate for the second or first speed. Therefore, an objective zone of electronic control is enlarged so that shifting down is avoided and excessive engine braking or engine overrunning is prevented.
When the electronic control means does not send a control signal to the control solenoid valve and the shift limiting valve does not work, the planetary gear transmission is changed according to driver's speed change operation. Therefore, the drive mode can be changed to any speed change stage by operating the shift tower in case for example when the electronic control means breaks down to become incapable of sending an output signal.
Further, when a line pressure control solenoid valve is utilized also as the foregoing control solenoid valve, it becomes unnecessary to specially install the control solenoid valve so that this measure provides economical structure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic structural diagram of an automatic transmiss
REFERENCES:
patent: 3937105 (1976-02-01), Arai et al.
patent: 4467427 (1984-08-01), Magnusson
patent: 4488457 (1984-12-01), Nishimura et al.
patent: 4631984 (1986-12-01), Jones
patent: 4829853 (1989-05-01), Sakaguchi
patent: 4846022 (1989-07-01), Ito et al.
patent: 4942782 (1990-07-01), Kumayama et al.
Ookubo Masahiro
Shiba Hirofumi
Braun Leslie A.
Kabushiki Kaisha Daikin Seisakusho
Levi Benjamin
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